Internet DRAFT - draft-ietf-dots-signal-channel
draft-ietf-dots-signal-channel
DOTS T. Reddy, Ed.
Internet-Draft McAfee
Intended status: Standards Track M. Boucadair, Ed.
Expires: July 9, 2020 Orange
P. Patil
Cisco
A. Mortensen
Arbor Networks, Inc.
N. Teague
Iron Mountain Data Centers
January 6, 2020
Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal
Channel Specification
draft-ietf-dots-signal-channel-41
Abstract
This document specifies the DOTS signal channel, a protocol for
signaling the need for protection against Distributed Denial-of-
Service (DDoS) attacks to a server capable of enabling network
traffic mitigation on behalf of the requesting client.
A companion document defines the DOTS data channel, a separate
reliable communication layer for DOTS management and configuration
purposes.
Editorial Note (To be removed by RFC Editor)
Please update these statements within the document with the RFC
number to be assigned to this document:
o "This version of this YANG module is part of RFC XXXX;"
o "RFC XXXX: Distributed Denial-of-Service Open Threat Signaling
(DOTS) Signal Channel Specification";
o "| [RFCXXXX] |"
o reference: RFC XXXX
Please update this statement with the RFC number to be assigned to
the following documents:
o "RFC YYYY: Distributed Denial-of-Service Open Threat Signaling
(DOTS) Data Channel Specification (used to be I-D.ietf-dots-data-
channel)
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Please update TBD/TBD1/TBD2 statements with the assignments made by
IANA to DOTS Signal Channel Protocol.
Also, please update the "revision" date of the YANG modules.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 9, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 6
4. DOTS Signal Channel: Messages & Behaviors . . . . . . . . . . 10
4.1. DOTS Server(s) Discovery . . . . . . . . . . . . . . . . 10
4.2. CoAP URIs . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3. Happy Eyeballs for DOTS Signal Channel . . . . . . . . . 10
4.4. DOTS Mitigation Methods . . . . . . . . . . . . . . . . . 12
4.4.1. Request Mitigation . . . . . . . . . . . . . . . . . 13
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4.4.2. Retrieve Information Related to a Mitigation . . . . 29
4.4.2.1. DOTS Servers Sending Mitigation Status . . . . . 34
4.4.2.2. DOTS Clients Polling for Mitigation Status . . . 37
4.4.3. Efficacy Update from DOTS Clients . . . . . . . . . . 38
4.4.4. Withdraw a Mitigation . . . . . . . . . . . . . . . . 40
4.5. DOTS Signal Channel Session Configuration . . . . . . . . 41
4.5.1. Discover Configuration Parameters . . . . . . . . . . 43
4.5.2. Convey DOTS Signal Channel Session Configuration . . 48
4.5.3. Configuration Freshness and Notifications . . . . . . 53
4.5.4. Delete DOTS Signal Channel Session Configuration . . 54
4.6. Redirected Signaling . . . . . . . . . . . . . . . . . . 55
4.7. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 57
5. DOTS Signal Channel YANG Modules . . . . . . . . . . . . . . 60
5.1. Tree Structure . . . . . . . . . . . . . . . . . . . . . 60
5.2. IANA DOTS Signal Channel YANG Module . . . . . . . . . . 62
5.3. IETF DOTS Signal Channel YANG Module . . . . . . . . . . 66
6. YANG/JSON Mapping Parameters to CBOR . . . . . . . . . . . . 77
7. (D)TLS Protocol Profile and Performance Considerations . . . 79
7.1. (D)TLS Protocol Profile . . . . . . . . . . . . . . . . . 79
7.2. (D)TLS 1.3 Considerations . . . . . . . . . . . . . . . . 81
7.3. DTLS MTU and Fragmentation . . . . . . . . . . . . . . . 83
8. Mutual Authentication of DOTS Agents & Authorization of DOTS
Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 86
9.1. DOTS Signal Channel UDP and TCP Port Number . . . . . . . 86
9.2. Well-Known 'dots' URI . . . . . . . . . . . . . . . . . . 86
9.3. Media Type Registration . . . . . . . . . . . . . . . . . 86
9.4. CoAP Content-Formats Registration . . . . . . . . . . . . 87
9.5. CBOR Tag Registration . . . . . . . . . . . . . . . . . . 87
9.6. DOTS Signal Channel Protocol Registry . . . . . . . . . . 88
9.6.1. DOTS Signal Channel CBOR Key Values Sub-Registry . . 88
9.6.1.1. Registration Template . . . . . . . . . . . . . . 88
9.6.1.2. Initial Sub-Registry Content . . . . . . . . . . 89
9.6.2. Status Codes Sub-Registry . . . . . . . . . . . . . . 91
9.6.3. Conflict Status Codes Sub-Registry . . . . . . . . . 92
9.6.4. Conflict Cause Codes Sub-Registry . . . . . . . . . . 94
9.6.5. Attack Status Codes Sub-Registry . . . . . . . . . . 94
9.7. DOTS Signal Channel YANG Modules . . . . . . . . . . . . 95
10. Security Considerations . . . . . . . . . . . . . . . . . . . 96
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 98
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 99
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 99
13.1. Normative References . . . . . . . . . . . . . . . . . . 99
13.2. Informative References . . . . . . . . . . . . . . . . . 102
Appendix A. CUID Generation . . . . . . . . . . . . . . . . . . 107
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 107
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1. Introduction
A distributed denial-of-service (DDoS) attack is a distributed
attempt to make machines or network resources unavailable to their
intended users. In most cases, sufficient scale for an effective
attack can be achieved by compromising enough end-hosts and using
those infected hosts to perpetrate and amplify the attack. The
victim in this attack can be an application server, a host, a router,
a firewall, or an entire network.
Network applications have finite resources like CPU cycles, the
number of processes or threads they can create and use, the maximum
number of simultaneous connections they can handle, the limited
resources of the control plane, etc. When processing network
traffic, such applications are supposed to use these resources to
provide the intended functionality in the most efficient manner.
However, a DDoS attacker may be able to prevent an application from
performing its intended task by making the application exhaust its
finite resources.
A TCP DDoS SYN-flood [RFC4987], for example, is a memory-exhausting
attack while an ACK-flood is a CPU-exhausting attack. Attacks on the
link are carried out by sending enough traffic so that the link
becomes congested, thereby likely causing packet loss for legitimate
traffic. Stateful firewalls can also be attacked by sending traffic
that causes the firewall to maintain an excessive number of states
that may jeopardize the firewall's operation overall, besides likely
performance impacts. The firewall then runs out of memory, and can
no longer instantiate the states required to process legitimate
flows. Other possible DDoS attacks are discussed in [RFC4732].
In many cases, it may not be possible for network administrators to
determine the cause(s) of an attack. They may instead just realize
that certain resources seem to be under attack. This document
defines a lightweight protocol that allows a DOTS client to request
mitigation from one or more DOTS servers for protection against
detected, suspected, or anticipated attacks. This protocol enables
cooperation between DOTS agents to permit a highly-automated network
defense that is robust, reliable, and secure. Note that "secure"
means the support of the features defined in Section 2.4 of
[RFC8612].
An example of a network diagram that illustrates a deployment of DOTS
agents is shown in Figure 1. In this example, a DOTS server is
operating on the access network. A DOTS client is located on the LAN
(Local Area Network), while a DOTS gateway is embedded in the CPE
(Customer Premises Equipment).
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Network
Resource CPE router Access network __________
+-----------+ +--------------+ +-------------+ / \
| |___| |____| |___ | Internet |
|DOTS client| | DOTS gateway | | DOTS server | | |
| | | | | | | |
+-----------+ +--------------+ +-------------+ \__________/
Figure 1: Sample DOTS Deployment (1)
DOTS servers can also be reachable over the Internet, as depicted in
Figure 2.
Network DDoS mitigation
Resource CPE router __________ service
+-----------+ +-------------+ / \ +-------------+
| |___| |____| |___ | |
|DOTS client| |DOTS gateway | | Internet | | DOTS server |
| | | | | | | |
+-----------+ +-------------+ \__________/ +-------------+
Figure 2: Sample DOTS Deployment (2)
In typical deployments, the DOTS client belongs to a different
administrative domain than the DOTS server. For example, the DOTS
client is embedded in a firewall protecting services owned and
operated by a customer, while the DOTS server is owned and operated
by a different administrative entity (service provider, typically)
providing DDoS mitigation services. The latter might or might not
provide connectivity services to the network hosting the DOTS client.
The DOTS server may (not) be co-located with the DOTS mitigator. In
typical deployments, the DOTS server belongs to the same
administrative domain as the mitigator. The DOTS client can
communicate directly with a DOTS server or indirectly via a DOTS
gateway.
The document adheres to the DOTS architecture
[I-D.ietf-dots-architecture]. The requirements for DOTS signal
channel protocol are documented in [RFC8612]. This document
satisfies all the use cases discussed in [I-D.ietf-dots-use-cases].
This document focuses on the DOTS signal channel. This is a
companion document of the DOTS data channel specification
[I-D.ietf-dots-data-channel] that defines a configuration and a bulk
data exchange mechanism supporting the DOTS signal channel.
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2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
(D)TLS is used for statements that apply to both Transport Layer
Security [RFC5246][RFC8446] and Datagram Transport Layer Security
[RFC6347]. Specific terms are used for any statement that applies to
either protocol alone.
The reader should be familiar with the terms defined in [RFC8612].
The meaning of the symbols in YANG tree diagrams is defined in
[RFC8340].
3. Design Overview
The DOTS signal channel is built on top of the Constrained
Application Protocol (CoAP) [RFC7252], a lightweight protocol
originally designed for constrained devices and networks. The many
features of CoAP (expectation of packet loss, support for
asynchronous Non-confirmable messaging, congestion control, small
message overhead limiting the need for fragmentation, use of minimal
resources, and support for (D)TLS) makes it a good candidate to build
the DOTS signaling mechanism from.
DOTS clients and servers behave as CoAP endpoints. By default, a
DOTS client (or server) behaves as a CoAP client (or server).
Nevertheless, a DOTS client (or server) behaves as a CoAP server (or
client) for specific operations such as DOTS heartbeat operations
(Section 4.7).
The DOTS signal channel is layered on existing standards (Figure 3).
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+---------------------+
| DOTS Signal Channel |
+---------------------+
| CoAP |
+----------+----------+
| TLS | DTLS |
+----------+----------+
| TCP | UDP |
+----------+----------+
| IP |
+---------------------+
Figure 3: Abstract Layering of DOTS Signal Channel over CoAP over
(D)TLS
In some cases, a DOTS client and server may have mutual agreement to
use a specific port number, such as by explicit configuration or
dynamic discovery [I-D.ietf-dots-server-discovery]. Absent such
mutual agreement, the DOTS signal channel MUST run over port number
TBD as defined in Section 9.1, for both UDP and TCP. In order to use
a distinct port number (as opposed to TBD), DOTS clients and servers
SHOULD support a configurable parameter to supply the port number to
use.
Note: The rationale for not using the default port number 5684
((D)TLS CoAP) is to avoid the discovery of services and resources
discussed in [RFC7252] and allow for differentiated behaviors in
environments where both a DOTS gateway and an IoT gateway (e.g.,
Figure 3 of [RFC7452]) are co-located.
Particularly, the use of a default port number is meant to
simplify DOTS deployment in scenarios where no explicit IP address
configuration is required. For example, the use of the default
router as DOTS server aims to ease DOTS deployment within LANs (in
which, CPEs embed a DOTS gateway as illustrated in Figures 1 and
2) without requiring a sophisticated discovery method and
configuration tasks within the LAN. It is also possible to use
anycast addresses for DOTS servers to simplify DOTS client
configuration, including service discovery. In such anycast-based
scenario, a DOTS client initiating a DOTS session to the DOTS
server anycast address may, for example, be (1) redirected to the
DOTS server unicast address to be used by the DOTS client
following the procedure discussed in Section 4.6 or (2) relayed to
a unicast DOTS server.
The signal channel uses the "coaps" URI scheme defined in Section 6
of [RFC7252] and the "coaps+tcp" URI scheme defined in Section 8.2 of
[RFC8323] to identify DOTS server resources accessible using CoAP
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over UDP secured with DTLS and CoAP over TCP secured with TLS,
respectively.
The DOTS signal channel can be established between two DOTS agents
prior or during an attack. The DOTS signal channel is initiated by
the DOTS client. The DOTS client can then negotiate, configure, and
retrieve the DOTS signal channel session behavior with its DOTS peer
(Section 4.5). Once the signal channel is established, the DOTS
agents may periodically send heartbeats to keep the channel active
(Section 4.7). At any time, the DOTS client may send a mitigation
request message (Section 4.4) to a DOTS server over the active signal
channel. While mitigation is active (because of the higher
likelihood of packet loss during a DDoS attack), the DOTS server
periodically sends status messages to the client, including basic
mitigation feedback details. Mitigation remains active until the
DOTS client explicitly terminates mitigation, or the mitigation
lifetime expires. Also, the DOTS server may rely on the signal
channel session loss to trigger mitigation for pre-configured
mitigation requests (if any).
DOTS signaling can happen with DTLS over UDP and TLS over TCP.
Likewise, DOTS requests may be sent using IPv4 or IPv6 transfer
capabilities. A Happy Eyeballs procedure for DOTS signal channel is
specified in Section 4.3.
A DOTS client is entitled to access only to resources it creates. In
particular, a DOTS client can not retrieve data related to mitigation
requests created by other DOTS clients of the same DOTS client
domain.
Messages exchanged between DOTS agents are serialized using Concise
Binary Object Representation (CBOR) [RFC7049], a binary encoding
scheme designed for small code and message size. CBOR-encoded
payloads are used to carry signal channel-specific payload messages
which convey request parameters and response information such as
errors. In order to allow reusing data models across protocols,
[RFC7951] specifies the JavaScript Object Notation (JSON) encoding of
YANG-modeled data. A similar effort for CBOR is defined in
[I-D.ietf-core-yang-cbor].
DOTS agents determine that a CBOR data structure is a DOTS signal
channel object from the application context, such as from the port
number assigned to the DOTS signal channel. The other method DOTS
agents use to indicate that a CBOR data structure is a DOTS signal
channel object is the use of the "application/dots+cbor" content type
(Section 9.3).
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This document specifies a YANG module for representing DOTS
mitigation scopes, DOTS signal channel session configuration data,
and DOTS redirected signaling (Section 5). All parameters in the
payload of the DOTS signal channel are mapped to CBOR types as
specified in Table 4 (Section 6).
In order to prevent fragmentation, DOTS agents must follow the
recommendations documented in Section 4.6 of [RFC7252]. Refer to
Section 7.3 for more details.
DOTS agents MUST support GET, PUT, and DELETE CoAP methods. The
payload included in CoAP responses with 2.xx Response Codes MUST be
of content type "application/dots+cbor". CoAP responses with 4.xx
and 5.xx error Response Codes MUST include a diagnostic payload
(Section 5.5.2 of [RFC7252]). The Diagnostic Payload may contain
additional information to aid troubleshooting.
In deployments where multiple DOTS clients are enabled in a network
(owned and operated by the same entity), the DOTS server may detect
conflicting mitigation requests from these clients. This document
does not aim to specify a comprehensive list of conditions under
which a DOTS server will characterize two mitigation requests from
distinct DOTS clients as conflicting, nor recommend a DOTS server
behavior for processing conflicting mitigation requests. Those
considerations are implementation- and deployment-specific.
Nevertheless, the document specifies the mechanisms to notify DOTS
clients when conflicts occur, including the conflict cause
(Section 4.4).
In deployments where one or more translators (e.g., Traditional NAT
[RFC3022], CGN [RFC6888], NAT64 [RFC6146], NPTv6 [RFC6296]) are
enabled between the client's network and the DOTS server, DOTS signal
channel messages forwarded to a DOTS server MUST NOT include internal
IP addresses/prefixes and/or port numbers; external addresses/
prefixes and/or port numbers as assigned by the translator MUST be
used instead. This document does not make any recommendation about
possible translator discovery mechanisms. The following are some
(non-exhaustive) deployment examples that may be considered:
o Port Control Protocol (PCP) [RFC6887] or Session Traversal
Utilities for NAT (STUN) [RFC5389] may be used to retrieve the
external addresses/prefixes and/or port numbers. Information
retrieved by means of PCP or STUN will be used to feed the DOTS
signal channel messages that will be sent to a DOTS server.
o A DOTS gateway may be co-located with the translator. The DOTS
gateway will need to update the DOTS messages, based upon the
local translator's binding table.
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4. DOTS Signal Channel: Messages & Behaviors
4.1. DOTS Server(s) Discovery
This document assumes that DOTS clients are provisioned with the
reachability information of their DOTS server(s) using any of a
variety of means (e.g., local configuration, or dynamic means such as
DHCP [I-D.ietf-dots-server-discovery]). The description of such
means is out of scope of this document.
Likewise, it is out of scope of this document to specify the behavior
to be followed by a DOTS client to send DOTS requests when multiple
DOTS servers are provisioned (e.g., contact all DOTS servers, select
one DOTS server among the list). Such behavior is specified in other
documents (e.g., [I-D.ietf-dots-multihoming]).
4.2. CoAP URIs
The DOTS server MUST support the use of the path-prefix of "/.well-
known/" as defined in [RFC8615] and the registered name of "dots".
Each DOTS operation is indicated by a path-suffix that indicates the
intended operation. The operation path (Table 1) is appended to the
path-prefix to form the URI used with a CoAP request to perform the
desired DOTS operation.
+-----------------------+----------------+-------------+
| Operation | Operation Path | Details |
+-----------------------+----------------+-------------+
| Mitigation | /mitigate | Section 4.4 |
+-----------------------+----------------+-------------+
| Session configuration | /config | Section 4.5 |
+-----------------------+----------------+-------------+
| Heartbeat | /hb | Section 4.7 |
+-----------------------+----------------+-------------+
Table 1: Operations and their Corresponding URIs
4.3. Happy Eyeballs for DOTS Signal Channel
[RFC8612] mentions that DOTS agents will have to support both
connectionless and connection-oriented protocols. As such, the DOTS
signal channel is designed to operate with DTLS over UDP and TLS over
TCP. Further, a DOTS client may acquire a list of IPv4 and IPv6
addresses (Section 4.1), each of which can be used to contact the
DOTS server using UDP and TCP. If no list of IPv4 and IPv6 addresses
to contact the DOTS server is configured (or discovered), the DOTS
client adds the IPv4/IPv6 addresses of its default router to the
candidate list to contact the DOTS server.
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The following specifies the procedure to follow to select the address
family and the transport protocol for sending DOTS signal channel
messages.
Such procedure is needed to avoid experiencing long connection
delays. For example, if an IPv4 path to reach a DOTS server is
functional, but the DOTS server's IPv6 path is non-functional, a
dual-stack DOTS client may experience a significant connection delay
compared to an IPv4-only DOTS client, in the same network conditions.
The other problem is that if a middlebox between the DOTS client and
DOTS server is configured to block UDP traffic, the DOTS client will
fail to establish a DTLS association with the DOTS server and, as a
consequence, will have to fall back to TLS over TCP, thereby
incurring significant connection delays.
To overcome these connection setup problems, the DOTS client attempts
to connect to its DOTS server(s) using both IPv6 and IPv4, and tries
both DTLS over UDP and TLS over TCP following a DOTS Happy Eyeballs
approach. To some extent, this approach is similar to the Happy
Eyeballs mechanism defined in [RFC8305]. The connection attempts are
performed by the DOTS client when it initializes, or in general when
it has to select an address family and transport to contact its DOTS
server. The results of the Happy Eyeballs procedure are used by the
DOTS client for sending its subsequent messages to the DOTS server.
The difference in behavior with respect to the Happy Eyeballs
mechanism [RFC8305] are listed below:
o The order of preference of the DOTS signal channel address family
and transport protocol (most preferred first) is: UDP over IPv6,
UDP over IPv4, TCP over IPv6, and finally TCP over IPv4. This
order adheres to the address preference order specified in
[RFC6724] and the DOTS signal channel preference which privileges
the use of UDP over TCP (to avoid TCP's head of line blocking).
o The DOTS client after successfully establishing a connection MUST
cache information regarding the outcome of each connection attempt
for a specific time period, and it uses that information to avoid
thrashing the network with subsequent attempts. The cached
information is flushed when its age exceeds a specific time period
on the order of few minutes (e.g., 10 min). Typically, if the
DOTS client has to re-establish the connection with the same DOTS
server within few seconds after the Happy Eyeballs mechanism is
completed, caching avoids trashing the network especially in the
presence of DDoS attack traffic.
o If DOTS signal channel session is established with TLS (but DTLS
failed), the DOTS client periodically repeats the mechanism to
discover whether DOTS signal channel messages with DTLS over UDP
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becomes available from the DOTS server, so the DOTS client can
migrate the DOTS signal channel from TCP to UDP. Such probing
SHOULD NOT be done more frequently than every 24 hours and MUST
NOT be done more frequently than every 5 minutes.
When connection attempts are made during an attack, the DOTS client
SHOULD use a "Connection Attempt Delay" [RFC8305] set to 100 ms.
In reference to Figure 4, the DOTS client proceeds with the
connection attempts following the rules in [RFC8305]. In this
example, it is assumed that the IPv6 path is broken and UDP traffic
is dropped by a middlebox but has little impact to the DOTS client
because there is no long delay before using IPv4 and TCP.
+-----------+ +-----------+
|DOTS client| |DOTS server|
+-----------+ +-----------+
| |
T0 |--DTLS ClientHello, IPv6 ---->X |
T1 |--DTLS ClientHello, IPv4 ---->X |
T2 |--TCP SYN, IPv6-------------->X |
T3 |--TCP SYN, IPv4--------------------------------------->|
|<-TCP SYNACK-------------------------------------------|
|--TCP ACK--------------------------------------------->|
|<------------Establish TLS Session-------------------->|
|----------------DOTS signal--------------------------->|
| |
Note:
* Retransmission messages are not shown.
* T1-T0=T2-T1=T3-T2= Connection Attempt Delay.
Figure 4: DOTS Happy Eyeballs (Sample Flow)
A single DOTS signal channel between DOTS agents can be used to
exchange multiple DOTS signal messages. To reduce DOTS client and
DOTS server workload, DOTS clients SHOULD re-use the (D)TLS session.
4.4. DOTS Mitigation Methods
The following methods are used by a DOTS client to request, withdraw,
or retrieve the status of mitigation requests:
PUT: DOTS clients use the PUT method to request mitigation from a
DOTS server (Section 4.4.1). During active mitigation, DOTS
clients may use PUT requests to carry mitigation efficacy
updates to the DOTS server (Section 4.4.3).
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GET: DOTS clients may use the GET method to subscribe to DOTS
server status messages, or to retrieve the list of its
mitigations maintained by a DOTS server (Section 4.4.2).
DELETE: DOTS clients use the DELETE method to withdraw a request for
mitigation from a DOTS server (Section 4.4.4).
Mitigation request and response messages are marked as Non-
confirmable messages (Section 2.2 of [RFC7252]).
DOTS agents MUST NOT send more than one UDP datagram per round-trip
time (RTT) to the peer DOTS agent on average following the data
transmission guidelines discussed in Section 3.1.3 of [RFC8085].
Requests marked by the DOTS client as Non-confirmable messages are
sent at regular intervals until a response is received from the DOTS
server. If the DOTS client cannot maintain an RTT estimate, it MUST
NOT send more than one Non-confirmable request every 3 seconds, and
SHOULD use an even less aggressive rate whenever possible (case 2 in
Section 3.1.3 of [RFC8085]). Mitigation requests MUST NOT be delayed
because of checks on probing rate (Section 4.7 of [RFC7252]).
JSON encoding of YANG modelled data [RFC7951] is used to illustrate
the various methods defined in the following sub-sections. Also, the
examples use the Labels defined in Sections 9.6.2, 9.6.3, 9.6.4, and
9.6.5.
4.4.1. Request Mitigation
When a DOTS client requires mitigation for some reason, the DOTS
client uses the CoAP PUT method to send a mitigation request to its
DOTS server(s) (Figures 5 and 6).
If a DOTS client is entitled to solicit the DOTS service, the DOTS
server enables mitigation on behalf of the DOTS client by
communicating the DOTS client's request to a mitigator (which may be
co-located with the DOTS server) and relaying the feedback of the
thus-selected mitigator to the requesting DOTS client.
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Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
{
...
}
Figure 5: PUT to Convey DOTS Mitigation Requests
The order of the Uri-Path options is important as it defines the CoAP
resource. In particular, 'mid' MUST follow 'cuid'.
The additional Uri-Path parameters to those defined in Section 4.2
are as follows:
cuid: Stands for Client Unique Identifier. A globally unique
identifier that is meant to prevent collisions among DOTS
clients, especially those from the same domain. It MUST be
generated by DOTS clients.
For the reasons discussed in Appendix A, implementations SHOULD
set 'cuid' using the following procedure: first, the
Distinguished Encoding Rules (DER)-encoded Abstract Syntax
Notation One (ASN.1) representation of the Subject Public Key
Info (SPKI) of the DOTS client X.509 certificate [RFC5280], the
DOTS client raw public key [RFC7250], the "Pre-Shared Key (PSK)
identity" used by the DOTS client in the TLS 1.2
ClientKeyExchange message, or the "identity" used by the DOTS
client in the "pre_shared_key" TLS 1.3 extension is input to
the SHA-256 [RFC6234] cryptographic hash. Then, the output of
the cryptographic hash algorithm is truncated to 16 bytes;
truncation is done by stripping off the final 16 bytes. The
truncated output is base64url encoded (Section 5 of [RFC4648])
with the trailing "=" removed from the encoding, and the
resulting value used as the 'cuid'.
The 'cuid' is intended to be stable when communicating with a
given DOTS server, i.e., the 'cuid' used by a DOTS client
SHOULD NOT change over time. Distinct 'cuid' values MAY be
used by a single DOTS client per DOTS server.
If a DOTS client has to change its 'cuid' for some reason, it
MUST NOT do so when mitigations are still active for the old
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'cuid'. The 'cuid' SHOULD be 22 characters to avoid DOTS
signal message fragmentation over UDP. Furthermore, if that
DOTS client created aliases and filtering entries at the DOTS
server by means of the DOTS data channel, it MUST delete all
the entries bound to the old 'cuid' and re-install them using
the new 'cuid'.
DOTS servers MUST return 4.09 (Conflict) error code to a DOTS
peer to notify that the 'cuid' is already in-use by another
DOTS client. Upon receipt of that error code, a new 'cuid'
MUST be generated by the DOTS peer (e.g., using [RFC4122]).
Client-domain DOTS gateways MUST handle 'cuid' collision
directly and it is RECOMMENDED that 'cuid' collision is handled
directly by server-domain DOTS gateways.
DOTS gateways MAY rewrite the 'cuid' used by peer DOTS clients.
Triggers for such rewriting are out of scope.
This is a mandatory Uri-Path parameter.
mid: Identifier for the mitigation request represented with an
integer. This identifier MUST be unique for each mitigation
request bound to the DOTS client, i.e., the 'mid' parameter
value in the mitigation request needs to be unique (per 'cuid'
and DOTS server) relative to the 'mid' parameter values of
active mitigation requests conveyed from the DOTS client to the
DOTS server.
In order to handle out-of-order delivery of mitigation
requests, 'mid' values MUST increase monotonically.
If the 'mid' value has reached 3/4 of (2**32 - 1) (i.e.,
3221225471) and no attack is detected, the DOTS client MUST
reset 'mid' to 0 to handle 'mid' rollover. If the DOTS client
maintains mitigation requests with pre-configured scopes, it
MUST re-create them with the 'mid' restarting at 0.
This identifier MUST be generated by the DOTS client.
This is a mandatory Uri-Path parameter.
'cuid' and 'mid' MUST NOT appear in the PUT request message body
(Figure 6). The schema in Figure 6 uses the types defined in
Section 6. Note that this figure (and other similar figures
depicting a schema) are non-normative sketches of the structure of
the message.
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{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"string"
],
"target-port-range": [
{
"lower-port": number,
"upper-port": number
}
],
"target-protocol": [
number
],
"target-fqdn": [
"string"
],
"target-uri": [
"string"
],
"alias-name": [
"string"
],
"lifetime": number,
"trigger-mitigation": true|false
}
]
}
}
Figure 6: PUT to Convey DOTS Mitigation Requests (Message Body
Schema)
The parameters in the CBOR body (Figure 6) of the PUT request are
described below:
target-prefix: A list of prefixes identifying resources under
attack. Prefixes are represented using Classless Inter-Domain
Routing (CIDR) notation [RFC4632].
As a reminder, the prefix length must be less than or equal to 32
(or 128) for IPv4 (or IPv6).
The prefix list MUST NOT include broadcast, loopback, or multicast
addresses. These addresses are considered as invalid values. In
addition, the DOTS server MUST validate that target prefixes are
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within the scope of the DOTS client domain. Other validation
checks may be supported by DOTS servers.
This is an optional attribute.
target-port-range: A list of port numbers bound to resources under
attack.
A port range is defined by two bounds, a lower port number (lower-
port) and an upper port number (upper-port). When only 'lower-
port' is present, it represents a single port number.
For TCP, UDP, Stream Control Transmission Protocol (SCTP)
[RFC4960], or Datagram Congestion Control Protocol (DCCP)
[RFC4340], a range of ports can be, for example, 0-1023,
1024-65535, or 1024-49151.
This is an optional attribute.
target-protocol: A list of protocols involved in an attack. Values
are taken from the IANA protocol registry [proto_numbers].
If 'target-protocol' is not specified, then the request applies to
any protocol.
This is an optional attribute.
target-fqdn: A list of Fully Qualified Domain Names (FQDNs)
identifying resources under attack [RFC8499].
How a name is passed to an underlying name resolution library is
implementation- and deployment-specific. Nevertheless, once the
name is resolved into one or multiple IP addresses, DOTS servers
MUST apply the same validation checks as those for 'target-
prefix'.
The use of FQDNs may be suboptimal because:
* It induces both an extra load and increased delays on the DOTS
server to handle and manage DNS resolution requests.
* It does not guarantee that the DOTS server will resolve a name
to the same IP addresses that the DOTS client does.
This is an optional attribute.
target-uri: A list of Uniform Resource Identifiers (URIs) [RFC3986]
identifying resources under attack.
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The same validation checks used for 'target-fqdn' MUST be followed
by DOTS servers to validate a target URI.
This is an optional attribute.
alias-name: A list of aliases of resources for which the mitigation
is requested. Aliases can be created using the DOTS data channel
(Section 6.1 of [I-D.ietf-dots-data-channel]), direct
configuration, or other means.
An alias is used in subsequent signal channel exchanges to refer
more efficiently to the resources under attack.
This is an optional attribute.
lifetime: Lifetime of the mitigation request in seconds. The
RECOMMENDED lifetime of a mitigation request is 3600 seconds --
this value was chosen to be long enough so that refreshing is not
typically a burden on the DOTS client, while still making the
request expire in a timely manner when the client has unexpectedly
quit. DOTS clients MUST include this parameter in their
mitigation requests. Upon the expiry of this lifetime, and if the
request is not refreshed, the mitigation request is removed. The
request can be refreshed by sending the same request again.
A lifetime of '0' in a mitigation request is an invalid value.
A lifetime of negative one (-1) indicates indefinite lifetime for
the mitigation request. The DOTS server MAY refuse indefinite
lifetime, for policy reasons; the granted lifetime value is
returned in the response. DOTS clients MUST be prepared to not be
granted mitigations with indefinite lifetimes.
The DOTS server MUST always indicate the actual lifetime in the
response and the remaining lifetime in status messages sent to the
DOTS client.
This is a mandatory attribute.
trigger-mitigation: If the parameter value is set to 'false', DDoS
mitigation will not be triggered for the mitigation request unless
the DOTS signal channel session is lost.
If the DOTS client ceases to respond to heartbeat messages, the
DOTS server can detect that the DOTS signal channel session is
lost. More details are discussed in Section 4.7.
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The default value of the parameter is 'true' (that is, the
mitigation starts immediately). If 'trigger-mitigation' is not
present in a request, this is equivalent to receiving a request
with 'trigger-mitigation' set to 'true'.
This is an optional attribute.
In deployments where server-domain DOTS gateways are enabled,
identity information about the origin source client domain ('cdid')
SHOULD be propagated to the DOTS server. That information is meant
to assist the DOTS server to enforce some policies such as grouping
DOTS clients that belong to the same DOTS domain, limiting the number
of DOTS requests, and identifying the mitigation scope. These
policies can be enforced per-client, per-client domain, or both.
Also, the identity information may be used for auditing and debugging
purposes.
Figure 7 shows an example of a request relayed by a server-domain
DOTS gateway.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cdid=7eeaf349529eb55ed50113"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
{
...
}
Figure 7: PUT for DOTS Mitigation Request as Relayed by a DOTS
Gateway
A server-domain DOTS gateway SHOULD add the following Uri-Path
parameter:
cdid: Stands for Client Domain Identifier. The 'cdid' is conveyed by
a server-domain DOTS gateway to propagate the source domain
identity from the gateway's client-facing-side to the gateway's
server-facing-side, and from the gateway's server-facing-side
to the DOTS server. 'cdid' may be used by the final DOTS server
for policy enforcement purposes (e.g., enforce a quota on
filtering rules). These policies are deployment-specific.
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Server-domain DOTS gateways SHOULD support a configuration
option to instruct whether 'cdid' parameter is to be inserted.
In order to accommodate deployments that require enforcing per-
client policies, per-client domain policies, or a combination
thereof, server-domain DOTS gateways instructed to insert the
'cdid' parameter MUST supply the SPKI hash of the DOTS client
X.509 certificate, the DOTS client raw public key, or the hash
of the "PSK identity" in the 'cdid', following the same rules
for generating the hash conveyed in 'cuid', which is then used
by the ultimate DOTS server to determine the corresponding
client's domain. The 'cdid' generated by a server-domain
gateway is likely to be the same as the 'cuid' except if the
DOTS message was relayed by a client-domain DOTS gateway or the
'cuid' was generated from a rogue DOTS client.
If a DOTS client is provisioned, for example, with distinct
certificates as a function of the peer server-domain DOTS
gateway, distinct 'cdid' values may be supplied by a server-
domain DOTS gateway. The ultimate DOTS server MUST treat those
'cdid' values as equivalent.
The 'cdid' attribute MUST NOT be generated and included by DOTS
clients.
DOTS servers MUST ignore 'cdid' attributes that are directly
supplied by source DOTS clients or client-domain DOTS gateways.
This implies that first server-domain DOTS gateways MUST strip
'cdid' attributes supplied by DOTS clients. DOTS servers
SHOULD support a configuration parameter to identify DOTS
gateways that are trusted to supply 'cdid' attributes.
Only single-valued 'cdid' are defined in this document. That
is, only the first on-path server-domain DOTS gateway can
insert a 'cdid' value. This specification does not allow
multiple server-domain DOTS gateways, whenever involved in the
path, to insert a 'cdid' value for each server-domain gateway.
This is an optional Uri-Path. When present, 'cdid' MUST be
positioned before 'cuid'.
A DOTS gateway SHOULD add the CoAP Hop-Limit Option
[I-D.ietf-core-hop-limit].
Because of the complexity to handle partial failure cases, this
specification does not allow for including multiple mitigation
requests in the same PUT request. Concretely, a DOTS client MUST NOT
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include multiple entries in the 'scope' array of the same PUT
request.
FQDN and URI mitigation scopes may be thought of as a form of scope
alias, in which the addresses associated with the domain name or URI
(as resolved by the DOTS server) represent the scope of the
mitigation. Particularly, the IP addresses to which the host
subcomponent of authority component of an URI resolves represent the
'target-prefix', the URI scheme represents the 'target-protocol', the
port subcomponent of authority component of an URI represents the
'target-port-range'. If the optional port information is not present
in the authority component, the default port defined for the URI
scheme represents the 'target-port'.
In the PUT request at least one of the attributes 'target-prefix',
'target-fqdn','target-uri', or 'alias-name' MUST be present.
Attributes and Uri-Path parameters with empty values MUST NOT be
present in a request and render the entire request invalid.
Figure 8 shows a PUT request example to signal that TCP port numbers
80, 8080, and 443 used by 2001:db8:6401::1 and 2001:db8:6401::2
servers are under attack. The presence of 'cdid' indicates that a
server-domain DOTS gateway has modified the initial PUT request sent
by the DOTS client. Note that 'cdid' MUST NOT appear in the PUT
request message body.
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Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cdid=7eeaf349529eb55ed50113"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-port-range": [
{
"lower-port": 80
},
{
"lower-port": 443
},
{
"lower-port": 8080
}
],
"target-protocol": [
6
],
"lifetime": 3600
}
]
}
}
Figure 8: PUT for DOTS Mitigation Request (An Example)
The corresponding CBOR encoding format for the payload is shown in
Figure 9.
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A1 # map(1)
01 # unsigned(1)
A1 # map(1)
02 # unsigned(2)
81 # array(1)
A3 # map(3)
06 # unsigned(6)
82 # array(2)
74 # text(20)
323030313A6462383A363430313A3A312F313238
74 # text(20)
323030313A6462383A363430313A3A322F313238
07 # unsigned(7)
83 # array(3)
A1 # map(1)
08 # unsigned(8)
18 50 # unsigned(80)
A1 # map(1)
08 # unsigned(8)
19 01BB # unsigned(443)
A1 # map(1)
08 # unsigned(8)
19 1F90 # unsigned(8080)
0A # unsigned(10)
81 # array(1)
06 # unsigned(6)
0E # unsigned(14)
19 0E10 # unsigned(3600)
Figure 9: PUT for DOTS Mitigation Request (CBOR)
In both DOTS signal and data channel sessions, the DOTS client MUST
authenticate itself to the DOTS server (Section 8). The DOTS server
MAY use the algorithm presented in Section 7 of [RFC7589] to derive
the DOTS client identity or username from the client certificate.
The DOTS client identity allows the DOTS server to accept mitigation
requests with scopes that the DOTS client is authorized to manage.
The DOTS server couples the DOTS signal and data channel sessions
using the DOTS client identity and optionally the 'cdid' parameter
value, so the DOTS server can validate whether the aliases conveyed
in the mitigation request were indeed created by the same DOTS client
using the DOTS data channel session. If the aliases were not created
by the DOTS client, the DOTS server MUST return 4.00 (Bad Request) in
the response.
The DOTS server couples the DOTS signal channel sessions using the
DOTS client identity and optionally the 'cdid' parameter value, and
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the DOTS server uses 'mid' and 'cuid' Uri-Path parameter values to
detect duplicate mitigation requests. If the mitigation request
contains the 'alias-name' and other parameters identifying the target
resources (such as 'target-prefix', 'target-port-range', 'target-
fqdn', or 'target-uri'), the DOTS server appends the parameter values
in 'alias-name' with the corresponding parameter values in 'target-
prefix', 'target-port-range', 'target-fqdn', or 'target-uri'.
The DOTS server indicates the result of processing the PUT request
using CoAP response codes. CoAP 2.xx codes are success. CoAP 4.xx
codes are some sort of invalid requests (client errors). COAP 5.xx
codes are returned if the DOTS server is in an error state or is
currently unavailable to provide mitigation in response to the
mitigation request from the DOTS client.
Figure 10 shows an example response to a PUT request that is
successfully processed by a DOTS server (i.e., CoAP 2.xx response
codes). This version of the specification forbids 'cuid' and 'cdid'
(if used) to be returned in a response message body.
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"mid": 123,
"lifetime": 3600
}
]
}
}
Figure 10: 2.xx Response Body
If the request is missing a mandatory attribute, does not include
'cuid' or 'mid' Uri-Path options, includes multiple 'scope'
parameters, or contains invalid or unknown parameters, the DOTS
server MUST reply with 4.00 (Bad Request). DOTS agents can safely
ignore comprehension-optional parameters they don't understand
(Section 9.6.1.1).
A DOTS server that receives a mitigation request with a lifetime set
to '0' MUST reply with a 4.00 (Bad Request).
If the DOTS server does not find the 'mid' parameter value conveyed
in the PUT request in its configuration data, it MAY accept the
mitigation request by sending back a 2.01 (Created) response to the
DOTS client; the DOTS server will consequently try to mitigate the
attack. A DOTS server could reject mitigation requests when it is
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near capacity or needs to rate-limit a particular client, for
example.
The relative order of two mitigation requests, having the same
'trigger-mitigation' type, from a DOTS client is determined by
comparing their respective 'mid' values. If two mitigation requests
with the same 'trigger-mitigation' type have overlapping mitigation
scopes, the mitigation request with the highest numeric 'mid' value
will override the other mitigation request. Two mitigation requests
from a DOTS client have overlapping scopes if there is a common IP
address, IP prefix, FQDN, URI, or alias-name. To avoid maintaining a
long list of overlapping mitigation requests (i.e., requests with the
same 'trigger-mitigation' type and overlapping scopes) from a DOTS
client and avoid error-prone provisioning of mitigation requests from
a DOTS client, the overlapped lower numeric 'mid' MUST be
automatically deleted and no longer available at the DOTS server.
For example, if the DOTS server receives a mitigation request which
overlaps with an existing mitigation with a higher numeric 'mid', the
DOTS server rejects the request by returning 4.09 (Conflict) to the
DOTS client. The response includes enough information for a DOTS
client to recognize the source of the conflict as described below in
the 'conflict-information' subtree with only the relevant nodes
listed:
conflict-information: Indicates that a mitigation request is
conflicting with another mitigation request. This optional
attribute has the following structure:
conflict-cause: Indicates the cause of the conflict. The
following values are defined:
1: Overlapping targets. 'conflict-scope' provides more details
about the conflicting target clauses.
conflict-scope: Characterizes the exact conflict scope. It may
include a list of IP addresses, a list of prefixes, a list of
port numbers, a list of target protocols, a list of FQDNs, a
list of URIs, a list of alias-names, or a 'mid'.
If the DOTS server receives a mitigation request which overlaps with
an active mitigation request, but both having distinct 'trigger-
mitigation' types, the DOTS server SHOULD deactivate (absent explicit
policy/configuration otherwise) the mitigation request with 'trigger-
mitigation' set to false. Particularly, if the mitigation request
with 'trigger-mitigation' set to false is active, the DOTS server
withdraws the mitigation request (i.e., status code is set to '7' as
defined in Table 2) and transitions the status of the mitigation
request to '8'.
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Upon DOTS signal channel session loss with a peer DOTS client, the
DOTS server SHOULD withdraw (absent explicit policy/configuration
otherwise) any active mitigation requests overlapping with mitigation
requests having 'trigger-mitigation' set to false from that DOTS
client, as the loss of the session implicitly activates these
preconfigured mitigation requests and they take precedence. Note
that active-but-terminating period is not observed for mitigations
withdrawn at the initiative of the DOTS server.
DOTS clients may adopt various strategies for setting the scopes of
immediate and pre-configured mitigation requests to avoid potential
conflicts. For example, a DOTS client may tweak pre-configured
scopes so that the scope of any overlapping immediate mitigation
request will be a subset of the pre-configured scopes. Also, if an
immediate mitigation request overlaps with any of the pre-configured
scopes, the DOTS client sets the scope of the overlapping immediate
mitigation request to be a subset of the pre-configured scopes, so as
to get a broad mitigation when the DOTS signal channel collapses and
maximize the chance of recovery.
If the request is conflicting with an existing mitigation request
from a different DOTS client, the DOTS server may return 2.01
(Created) or 4.09 (Conflict) to the requesting DOTS client. If the
DOTS server decides to maintain the new mitigation request, the DOTS
server returns 2.01 (Created) to the requesting DOTS client. If the
DOTS server decides to reject the new mitigation request, the DOTS
server returns 4.09 (Conflict) to the requesting DOTS client. For
both 2.01 (Created) and 4.09 (Conflict) responses, the response
includes enough information for a DOTS client to recognize the source
of the conflict as described below:
conflict-information: Indicates that a mitigation request is
conflicting with another mitigation request(s) from other DOTS
client(s). This optional attribute has the following structure:
conflict-status: Indicates the status of a conflicting mitigation
request. The following values are defined:
1: DOTS server has detected conflicting mitigation requests
from different DOTS clients. This mitigation request is
currently inactive until the conflicts are resolved.
Another mitigation request is active.
2: DOTS server has detected conflicting mitigation requests
from different DOTS clients. This mitigation request is
currently active.
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3: DOTS server has detected conflicting mitigation requests
from different DOTS clients. All conflicting mitigation
requests are inactive.
conflict-cause: Indicates the cause of the conflict. The
following values are defined:
1: Overlapping targets. 'conflict-scope' provides more details
about the conflicting target clauses.
2: Conflicts with an existing accept-list. This code is
returned when the DDoS mitigation detects source addresses/
prefixes in the accept-listed ACLs are attacking the
target.
3: CUID Collision. This code is returned when a DOTS client
uses a 'cuid' that is already used by another DOTS client.
This code is an indication that the request has been
rejected and a new request with a new 'cuid' is to be re-
sent by the DOTS client (see the example shown in
Figure 11). Note that 'conflict-status', 'conflict-scope',
and 'retry-timer' MUST NOT be returned in the error
response.
conflict-scope: Characterizes the exact conflict scope. It may
include a list of IP addresses, a list of prefixes, a list of
port numbers, a list of target protocols, a list of FQDNs, a
list of URIs, a list of alias-names, or references to
conflicting ACLs (by an 'acl-name', typically
[I-D.ietf-dots-data-channel]).
retry-timer: Indicates, in seconds, the time after which the DOTS
client may re-issue the same request. The DOTS server returns
'retry-timer' only to DOTS client(s) for which a mitigation
request is deactivated. Any retransmission of the same
mitigation request before the expiry of this timer is likely to
be rejected by the DOTS server for the same reasons.
The retry-timer SHOULD be equal to the lifetime of the active
mitigation request resulting in the deactivation of the
conflicting mitigation request.
If the DOTS server decides to maintain a state for the
deactivated mitigation request, the DOTS server updates the
lifetime of the deactivated mitigation request to 'retry-timer
+ 45 seconds' (that is, this mitigation request remains
deactivated for the entire duration of 'retry-timer + 45
seconds') so that the DOTS client can refresh the deactivated
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mitigation request after 'retry-timer' seconds, but before the
expiry of the lifetime, and check if the conflict is resolved.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=7eeaf349529eb55ed50113"
Uri-Path: "mid=12"
(1) Request with a conflicting 'cuid'
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"conflict-information": {
"conflict-cause": "cuid-collision"
}
}
]
}
}
(2) Message body of the 4.09 (Conflict) response
from the DOTS server
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=f30d281ce6b64fc5a0b91e"
Uri-Path: "mid=12"
(3) Request with a new 'cuid'
Figure 11: Example of Generating a New 'cuid'
As an active attack evolves, DOTS clients can adjust the scope of
requested mitigation as necessary, by refining the scope of resources
requiring mitigation. This can be achieved by sending a PUT request
with a new 'mid' value that will override the existing one with
overlapping mitigation scopes.
For a mitigation request to continue beyond the initial negotiated
lifetime, the DOTS client has to refresh the current mitigation
request by sending a new PUT request. This PUT request MUST use the
same 'mid' value, and MUST repeat all the other parameters as sent in
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the original mitigation request apart from a possible change to the
lifetime parameter value. In such case, the DOTS server MAY update
the mitigation request, and a 2.04 (Changed) response is returned to
indicate a successful update of the mitigation request. If this is
not the case, the DOTS server MUST reject the request with a 4.00
(Bad Request).
4.4.2. Retrieve Information Related to a Mitigation
A GET request is used by a DOTS client to retrieve information
(including status) of DOTS mitigations from a DOTS server.
'cuid' is a mandatory Uri-Path parameter for GET requests.
Uri-Path parameters with empty values MUST NOT be present in a
request.
The same considerations for manipulating 'cdid' parameter by server-
domain DOTS gateways specified in Section 4.4.1 MUST be followed for
GET requests.
The 'c' Uri-Query option is used to control selection of
configuration and non-configuration data nodes. Concretely, the 'c'
(content) parameter and its permitted values defined in the following
table [I-D.ietf-core-comi] can be used to retrieve non-configuration
data (attack mitigation status), configuration data, or both. The
DOTS server MAY support this optional filtering capability. It can
safely ignore it if not supported. If the DOTS client supports the
optional filtering capability, it SHOULD use "c=n" query (to get back
only the dynamically changing data) or "c=c" query (to get back the
static configuration values) when the DDoS attack is active to limit
the size of the response.
+-------+-----------------------------------------------------+
| Value | Description |
+-------+-----------------------------------------------------+
| c | Return only configuration descendant data nodes |
| n | Return only non-configuration descendant data nodes |
| a | Return all descendant data nodes |
+-------+-----------------------------------------------------+
The DOTS client can use Block-wise transfer [RFC7959] to get the list
of all its mitigations maintained by a DOTS server, it can send
Block2 Option in a GET request with NUM = 0 to aid in limiting the
size of the response. If the representation of all the active
mitigation requests associated with the DOTS client does not fit
within a single datagram, the DOTS server MUST use the Block2 Option
with NUM = 0 in the GET response. The Size2 Option may be conveyed
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in the response to indicate the total size of the resource
representation. The DOTS client retrieves the rest of the
representation by sending additional GET requests with Block2 Options
containing NUM values greater than zero. The DOTS client MUST adhere
to the block size preferences indicated by the DOTS server in the
response. If the DOTS server uses the Block2 Option in the GET
response and the response is for a dynamically changing resource
(e.g., "c=n" or "c=a" query), the DOTS server MUST include the ETag
Option in the response. The DOTS client MUST include the same ETag
value in subsequent GET requests to retrieve the rest of the
representation.
The following examples illustrate how a DOTS client retrieves active
mitigation requests from a DOTS server. In particular:
o Figure 12 shows the example of a GET request to retrieve all DOTS
mitigation requests signaled by a DOTS client.
o Figure 13 shows the example of a GET request to retrieve a
specific DOTS mitigation request signaled by a DOTS client. The
configuration data to be reported in the response is formatted in
the same order as was processed by the DOTS server in the original
mitigation request.
These two examples assume the default of "c=a"; that is, the DOTS
client asks for all data to be reported by the DOTS server.
Header: GET (Code=0.01)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Observe: 0
Figure 12: GET to Retrieve all DOTS Mitigation Requests
Header: GET (Code=0.01)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=12332"
Observe: 0
Figure 13: GET to Retrieve a Specific DOTS Mitigation Request
If the DOTS server does not find the 'mid' Uri-Path value conveyed in
the GET request in its configuration data for the requesting DOTS
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client, it MUST respond with a 4.04 (Not Found) error response code.
Likewise, the same error MUST be returned as a response to a request
to retrieve all mitigation records (i.e., 'mid' Uri-Path is not
defined) of a given DOTS client if the DOTS server does not find any
mitigation record for that DOTS client. As a reminder, a DOTS client
is identified by its identity (e.g., client certificate, 'cuid') and
optionally the 'cdid'.
Figure 14 shows a response example of all active mitigation requests
associated with the DOTS client as maintained by the DOTS server.
The response indicates the mitigation status of each mitigation
request.
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{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"mid": 12332,
"mitigation-start": "1507818434",
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-protocol": [
17
],
"lifetime": 1756,
"status": "attack-successfully-mitigated",
"bytes-dropped": "134334555",
"bps-dropped": "43344",
"pkts-dropped": "333334444",
"pps-dropped": "432432"
},
{
"mid": 12333,
"mitigation-start": "1507818393",
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-protocol": [
6
],
"lifetime": 1755,
"status": "attack-stopped",
"bytes-dropped": "0",
"bps-dropped": "0",
"pkts-dropped": "0",
"pps-dropped": "0"
}
]
}
}
Figure 14: Response Body to a GET Request
The mitigation status parameters are described below:
mitigation-start: Mitigation start time is expressed in seconds
relative to 1970-01-01T00:00Z in UTC time (Section 2.4.1 of
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[RFC7049]). The CBOR encoding is modified so that the leading tag
1 (epoch-based date/time) MUST be omitted.
This is a mandatory attribute when an attack mitigation is active.
Particularly, 'mitigation-start' is not returned for a mitigation
with 'status' code set to 8.
lifetime: The remaining lifetime of the mitigation request, in
seconds.
This is a mandatory attribute.
status: Status of attack mitigation. The various possible values of
'status' parameter are explained in Table 2.
This is a mandatory attribute.
bytes-dropped: The total dropped byte count for the mitigation
request since the attack mitigation is triggered. The count wraps
around when it reaches the maximum value of unsigned integer64.
This is an optional attribute.
bps-dropped: The average number of dropped bytes per second for the
mitigation request since the attack mitigation is triggered. This
average SHOULD be over five-minute intervals (that is, measuring
bytes into five-minute buckets and then averaging these buckets
over the time since the mitigation was triggered).
This is an optional attribute.
pkts-dropped: The total number of dropped packet count for the
mitigation request since the attack mitigation is triggered. The
count wraps around when it reaches the maximum value of unsigned
integer64.
This is an optional attribute.
pps-dropped: The average number of dropped packets per second for
the mitigation request since the attack mitigation is triggered.
This average SHOULD be over five-minute intervals (that is,
measuring packets into five-minute buckets and then averaging
these buckets over the time since the mitigation was triggered).
This is an optional attribute.
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+-----------+-------------------------------------------------------+
| Parameter | Description |
| Value | |
+-----------+-------------------------------------------------------+
| 1 | Attack mitigation setup is in progress (e.g., |
| | changing the network path to redirect the inbound |
| | traffic to a DOTS mitigator). |
+-----------+-------------------------------------------------------+
| 2 | Attack is being successfully mitigated (e.g., traffic |
| | is redirected to a DDoS mitigator and attack traffic |
| | is dropped). |
+-----------+-------------------------------------------------------+
| 3 | Attack has stopped and the DOTS client can withdraw |
| | the mitigation request. This status code will be |
| | transmitted for immediate mitigation requests till |
| | the mitigation is withdrawn or the lifetime expires. |
| | For mitigation requests with pre-configured scopes |
| | (i.e., 'trigger-mitigation' set to 'false'), this |
| | status code will be transmitted 4 times and then |
| | transition to "8". |
+-----------+-------------------------------------------------------+
| 4 | Attack has exceeded the mitigation provider |
| | capability. |
+-----------+-------------------------------------------------------+
| 5 | DOTS client has withdrawn the mitigation request and |
| | the mitigation is active but terminating. |
+-----------+-------------------------------------------------------+
| 6 | Attack mitigation is now terminated. |
+-----------+-------------------------------------------------------+
| 7 | Attack mitigation is withdrawn (by the DOTS server). |
| | If a mitigation request with 'trigger-mitigation' set |
| | to false is withdrawn because it overlaps with an |
| | immediate mitigation request, this status code will |
| | be transmitted 4 times and then transition to "8" for |
| | the mitigation request with pre-configured scopes. |
+-----------+-------------------------------------------------------+
| 8 | Attack mitigation will be triggered for the |
| | mitigation request only when the DOTS signal channel |
| | session is lost. |
+-----------+-------------------------------------------------------+
Table 2: Values of 'status' Parameter
4.4.2.1. DOTS Servers Sending Mitigation Status
The Observe Option defined in [RFC7641] extends the CoAP core
protocol with a mechanism for a CoAP client to "observe" a resource
on a CoAP server: The client retrieves a representation of the
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resource and requests this representation be updated by the server as
long as the client is interested in the resource. DOTS
implementations MUST use the Observe Option for both 'mitigate' and
'config' (Section 4.2).
A DOTS client conveys the Observe Option set to '0' in the GET
request to receive asynchronous notifications of attack mitigation
status from the DOTS server.
Unidirectional mitigation notifications within the bidirectional
signal channel enables asynchronous notifications between the agents.
[RFC7641] indicates that (1) a notification can be sent in a
Confirmable or a Non-confirmable message, and (2) the message type
used is typically application-dependent and may be determined by the
server for each notification individually. For DOTS server
application, the message type MUST always be set to Non-confirmable
even if the underlying COAP library elects a notification to be sent
in a Confirmable message. This overrides the behavior defined in
Section 4.5 of [RFC7641] to send a Confirmable message instead of a
Non-confirmable message at least every 24 hour for the following
reasons: First, the DOTS signal channel uses a heartbeat mechanism to
determine if the DOTS client is alive. Second, Confirmable messages
are not suitable during an attack.
Due to the higher likelihood of packet loss during a DDoS attack, the
DOTS server periodically sends attack mitigation status to the DOTS
client and also notifies the DOTS client whenever the status of the
attack mitigation changes. If the DOTS server cannot maintain an RTT
estimate, it MUST NOT send more than one asynchronous notification
every 3 seconds, and SHOULD use an even less aggressive rate whenever
possible (case 2 in Section 3.1.3 of [RFC8085]).
When conflicting requests are detected, the DOTS server enforces the
corresponding policy (e.g., accept all requests, reject all requests,
accept only one request but reject all the others, ...). It is
assumed that this policy is supplied by the DOTS server administrator
or it is a default behavior of the DOTS server implementation. Then,
the DOTS server sends notification message(s) to the DOTS client(s)
at the origin of the conflict (refer to the conflict parameters
defined in Section 4.4.1). A conflict notification message includes
information about the conflict cause, scope, and the status of the
mitigation request(s). For example,
o A notification message with 'status' code set to '7 (Attack
mitigation is withdrawn)' and 'conflict-status' set to '1' is sent
to a DOTS client to indicate that an active mitigation request is
deactivated because a conflict is detected.
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o A notification message with 'status' code set to '1 (Attack
mitigation is in progress)' and 'conflict-status' set to '2' is
sent to a DOTS client to indicate that this mitigation request is
in progress, but a conflict is detected.
Upon receipt of a conflict notification message indicating that a
mitigation request is deactivated because of a conflict, a DOTS
client MUST NOT resend the same mitigation request before the expiry
of 'retry-timer'. It is also recommended that DOTS clients support
means to alert administrators about mitigation conflicts.
A DOTS client that is no longer interested in receiving notifications
from the DOTS server can simply "forget" the observation. When the
DOTS server sends the next notification, the DOTS client will not
recognize the token in the message and thus will return a Reset
message. This causes the DOTS server to remove the associated entry.
Alternatively, the DOTS client can explicitly deregister itself by
issuing a GET request that has the Token field set to the token of
the observation to be cancelled and includes an Observe Option with
the value set to '1' (deregister). The latter is more deterministic
and thus is RECOMMENDED.
Figure 15 shows an example of a DOTS client requesting a DOTS server
to send notifications related to a mitigation request. Note that for
mitigations with pre-configured scopes (i.e., 'trigger-mitigation'
set to 'false'), the state will need to transition from 3 (attack-
stopped) to 8 (attack-mitigation-signal-loss).
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+-----------+ +-----------+
|DOTS client| |DOTS server|
+-----------+ +-----------+
| |
| GET /<mid> |
| Token: 0x4a | Registration
| Observe: 0 |
+----------------------------------------->|
| |
| 2.05 Content |
| Token: 0x4a | Notification of
| Observe: 12 | the current state
| status: "attack-mitigation-in-progress" |
| |
|<-----------------------------------------+
| 2.05 Content |
| Token: 0x4a | Notification upon
| Observe: 44 | a state change
| status: "attack-successfully-mitigated" |
| |
|<-----------------------------------------+
| 2.05 Content |
| Token: 0x4a | Notification upon
| Observe: 60 | a state change
| status: "attack-stopped" |
|<-----------------------------------------+
| |
...
Figure 15: Notifications of Attack Mitigation Status
4.4.2.2. DOTS Clients Polling for Mitigation Status
The DOTS client can send the GET request at frequent intervals
without the Observe Option to retrieve the configuration data of the
mitigation request and non-configuration data (i.e., the attack
status). DOTS clients MAY be configured with a policy indicating the
frequency of polling DOTS servers to get the mitigation status. This
frequency MUST NOT be more than one UDP datagram per RTT as discussed
in Section 3.1.3 of [RFC8085].
If the DOTS server has been able to mitigate the attack and the
attack has stopped, the DOTS server indicates as such in the status.
In such case, the DOTS client recalls the mitigation request by
issuing a DELETE request for this mitigation request (Section 4.4.4).
A DOTS client SHOULD react to the status of the attack as per the
information sent by the DOTS server rather than performing its own
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detection that the attack has been mitigated. This ensures that the
DOTS client does not recall a mitigation request prematurely because
it is possible that the DOTS client does not sense the DDoS attack on
its resources, but the DOTS server could be actively mitigating the
attack because the attack is not completely averted.
4.4.3. Efficacy Update from DOTS Clients
While DDoS mitigation is in progress, due to the likelihood of packet
loss, a DOTS client MAY periodically transmit DOTS mitigation
efficacy updates to the relevant DOTS server. A PUT request is used
to convey the mitigation efficacy update to the DOTS server. This
PUT request is treated as a refresh of the current mitigation.
The PUT request used for efficacy update MUST include all the
parameters used in the PUT request to carry the DOTS mitigation
request (Section 4.4.1) unchanged apart from the 'lifetime' parameter
value. If this is not the case, the DOTS server MUST reject the
request with a 4.00 (Bad Request).
The If-Match Option (Section 5.10.8.1 of [RFC7252]) with an empty
value is used to make the PUT request conditional on the current
existence of the mitigation request. If UDP is used as transport,
CoAP requests may arrive out-of-order. For example, the DOTS client
may send a PUT request to convey an efficacy update to the DOTS
server followed by a DELETE request to withdraw the mitigation
request, but the DELETE request arrives at the DOTS server before the
PUT request. To handle out-of-order delivery of requests, if an If-
Match Option is present in the PUT request and the 'mid' in the
request matches a mitigation request from that DOTS client, the
request is processed by the DOTS server. If no match is found, the
PUT request is silently ignored by the DOTS server.
An example of an efficacy update message, which includes an If-Match
Option with an empty value, is depicted in Figure 16.
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Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
If-Match:
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:mitigation-scope": {
"scope": [
{
"target-prefix": [
"2001:db8:6401::1/128",
"2001:db8:6401::2/128"
],
"target-port-range": [
{
"lower-port": 80
},
{
"lower-port": 443
},
{
"lower-port": 8080
}
],
"target-protocol": [
6
],
"attack-status": "under-attack"
}
]
}
}
Figure 16: An Example of Efficacy Update
The 'attack-status' parameter is a mandatory attribute when
performing an efficacy update. The various possible values contained
in the 'attack-status' parameter are described in Table 3.
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+-----------+-------------------------------------------------------+
| Parameter | Description |
| value | |
+-----------+-------------------------------------------------------+
| 1 | The DOTS client determines that it is still under |
| | attack. |
+-----------+-------------------------------------------------------+
| 2 | The DOTS client determines that the attack is |
| | successfully mitigated (e.g., attack traffic is not |
| | seen). |
+-----------+-------------------------------------------------------+
Table 3: Values of 'attack-status' Parameter
The DOTS server indicates the result of processing a PUT request
using CoAP response codes. The response code 2.04 (Changed) is
returned if the DOTS server has accepted the mitigation efficacy
update. The error response code 5.03 (Service Unavailable) is
returned if the DOTS server has erred or is incapable of performing
the mitigation. As specified in [RFC7252], 5.03 uses Max-Age option
to indicate the number of seconds after which to retry.
4.4.4. Withdraw a Mitigation
DELETE requests are used to withdraw DOTS mitigation requests from
DOTS servers (Figure 17).
'cuid' and 'mid' are mandatory Uri-Path parameters for DELETE
requests.
The same considerations for manipulating 'cdid' parameter by DOTS
gateways, as specified in Section 4.4.1, MUST be followed for DELETE
requests. Uri-Path parameters with empty values MUST NOT be present
in a request.
Header: DELETE (Code=0.04)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "mitigate"
Uri-Path: "cuid=dz6pHjaADkaFTbjr0JGBpw"
Uri-Path: "mid=123"
Figure 17: Withdraw a DOTS Mitigation
If the DELETE request does not include 'cuid' and 'mid' parameters,
the DOTS server MUST reply with a 4.00 (Bad Request).
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Once the request is validated, the DOTS server immediately
acknowledges a DOTS client's request to withdraw the DOTS signal
using 2.02 (Deleted) response code with no response payload. A 2.02
(Deleted) Response Code is returned even if the 'mid' parameter value
conveyed in the DELETE request does not exist in its configuration
data before the request.
If the DOTS server finds the 'mid' parameter value conveyed in the
DELETE request in its configuration data for the DOTS client, then to
protect against route or DNS flapping caused by a DOTS client rapidly
removing a mitigation, and to dampen the effect of oscillating
attacks, the DOTS server MAY allow mitigation to continue for a
limited period after acknowledging a DOTS client's withdrawal of a
mitigation request. During this period, the DOTS server status
messages SHOULD indicate that mitigation is active but terminating
(Section 4.4.2).
The initial active-but-terminating period SHOULD be sufficiently long
to absorb latency incurred by route propagation. The active-but-
terminating period SHOULD be set by default to 120 seconds. If the
client requests mitigation again before the initial active-but-
terminating period elapses, the DOTS server MAY exponentially
increase (the base of the exponent is 2) the active-but-terminating
period up to a maximum of 300 seconds (5 minutes).
Once the active-but-terminating period elapses, the DOTS server MUST
treat the mitigation as terminated, as the DOTS client is no longer
responsible for the mitigation.
If a mitigation is triggered due to a signal channel loss, the DOTS
server relies upon normal triggers to stop that mitigation
(typically, receipt of a valid DELETE request, expiry of the
mitigation lifetime, or scrubbing the traffic to the attack target).
In particular, the DOTS server MUST NOT consider the signal channel
recovery as a trigger to stop the mitigation.
4.5. DOTS Signal Channel Session Configuration
A DOTS client can negotiate, configure, and retrieve the DOTS signal
channel session behavior with its DOTS peers. The DOTS signal
channel can be used, for example, to configure the following:
a. Heartbeat interval (heartbeat-interval): DOTS agents regularly
send heartbeats to each other after mutual authentication is
successfully completed in order to keep the DOTS signal channel
open. Heartbeat messages are exchanged between DOTS agents every
'heartbeat-interval' seconds to detect the current status of the
DOTS signal channel session.
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b. Missing heartbeats allowed (missing-hb-allowed): This variable
indicates the maximum number of consecutive heartbeat messages
for which a DOTS agent did not receive a response before
concluding that the session is disconnected or defunct.
c. Acceptable probing rate (probing-rate): This parameter indicates
the average data rate that must not be exceeded by a DOTS agent
in sending to a peer DOTS agent that does not respond.
d. Acceptable signal loss ratio: Maximum retransmissions,
retransmission timeout value, and other message transmission
parameters for Confirmable messages over the DOTS signal channel.
When the DOTS signal channel is established over a reliable transport
(e.g., TCP), there is no need for the reliability mechanisms provided
by CoAP over UDP since the underlying TCP connection provides
retransmissions and deduplication [RFC8323]. As a reminder, CoAP
over reliable transports does not support Confirmable or Non-
confirmable message types. As such, the transmission-related
parameters (missing-hb-allowed and acceptable signal loss ratio) are
negotiated only for DOTS over unreliable transports.
The same or distinct configuration sets may be used during times when
a mitigation is active ('mitigating-config') and when no mitigation
is active ('idle-config'). This is particularly useful for DOTS
servers that might want to reduce heartbeat frequency or cease
heartbeat exchanges when an active DOTS client has not requested
mitigation. If distinct configurations are used, DOTS agents MUST
follow the appropriate configuration set as a function of the
mitigation activity (e.g., if no mitigation request is active (also
referred to as 'idle' time), 'idle-config'-related values must be
followed). Additionally, DOTS agents MUST automatically switch to
the other configuration upon a change in the mitigation activity
(e.g., if an attack mitigation is launched after an 'idle' time, the
DOTS agent switches from 'idle-config' to 'mitigating-config'-related
values).
CoAP Requests and responses are indicated for reliable delivery by
marking them as Confirmable messages. DOTS signal channel session
configuration requests and responses are marked as Confirmable
messages. As explained in Section 2.1 of [RFC7252], a Confirmable
message is retransmitted using a default timeout and exponential
back-off between retransmissions, until the DOTS server sends an
Acknowledgement message (ACK) with the same Message ID conveyed from
the DOTS client.
Message transmission parameters are defined in Section 4.8 of
[RFC7252]. The DOTS server can either piggyback the response in the
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acknowledgement message or, if the DOTS server cannot respond
immediately to a request carried in a Confirmable message, it simply
responds with an Empty Acknowledgement message so that the DOTS
client can stop retransmitting the request. Empty Acknowledgement
messages are explained in Section 2.2 of [RFC7252]. When the
response is ready, the server sends it in a new Confirmable message
which in turn needs to be acknowledged by the DOTS client (see
Sections 5.2.1 and 5.2.2 of [RFC7252]). Requests and responses
exchanged between DOTS agents during 'idle' time, except heartbeat
messages, are marked as Confirmable messages.
Implementation Note: A DOTS client that receives a response in a
Confirmable message may want to clean up the message state right
after sending the ACK. If that ACK is lost and the DOTS server
retransmits the Confirmable message, the DOTS client may no longer
have any state that would help it correlate this response: from
the DOTS client's standpoint, the retransmission message is
unexpected. The DOTS client will send a Reset message so it does
not receive any more retransmissions. This behavior is normal and
not an indication of an error (see Section 5.3.2 of [RFC7252] for
more details).
4.5.1. Discover Configuration Parameters
A GET request is used to obtain acceptable (e.g., minimum and maximum
values) and current configuration parameters on the DOTS server for
DOTS signal channel session configuration. This procedure occurs
between a DOTS client and its immediate peer DOTS server. As such,
this GET request MUST NOT be relayed by a DOTS gateway.
Figure 18 shows how to obtain configuration parameters that the DOTS
server will find acceptable.
Header: GET (Code=0.01)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "config"
Figure 18: GET to Retrieve Configuration
The DOTS server in the 2.05 (Content) response conveys the current,
minimum, and maximum attribute values acceptable by the DOTS server
(Figure 19).
{
"ietf-dots-signal-channel:signal-config": {
"mitigating-config": {
"heartbeat-interval": {
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"max-value": number,
"min-value": number,
"current-value": number
},
"missing-hb-allowed": {
"max-value": number,
"min-value": number,
"current-value": number
},
"probing-rate": {
"max-value": number,
"min-value": number,
"current-value": number
},
"max-retransmit": {
"max-value": number,
"min-value": number,
"current-value": number
},
"ack-timeout": {
"max-value-decimal": "string",
"min-value-decimal": "string",
"current-value-decimal": "string"
},
"ack-random-factor": {
"max-value-decimal": "string",
"min-value-decimal": "string",
"current-value-decimal": "string"
}
},
"idle-config": {
"heartbeat-interval": {
"max-value": number,
"min-value": number,
"current-value": number
},
"missing-hb-allowed": {
"max-value": number,
"min-value": number,
"current-value": number
},
"probing-rate": {
"max-value": number,
"min-value": number,
"current-value": number
},
"max-retransmit": {
"max-value": number,
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"min-value": number,
"current-value": number
},
"ack-timeout": {
"max-value-decimal": "string",
"min-value-decimal": "string",
"current-value-decimal": "string"
},
"ack-random-factor": {
"max-value-decimal": "string",
"min-value-decimal": "string",
"current-value-decimal": "string"
}
}
}
}
Figure 19: GET Configuration Response Body Schema
The parameters in Figure 19 are described below:
mitigating-config: Set of configuration parameters to use when a
mitigation is active. The following parameters may be included:
heartbeat-interval: Time interval in seconds between two
consecutive heartbeat messages.
'0' is used to disable the heartbeat mechanism.
This is an optional attribute.
missing-hb-allowed: Maximum number of consecutive heartbeat
messages for which the DOTS agent did not receive a response
before concluding that the session is disconnected.
This is an optional attribute.
probing-rate: The average data rate that must not be exceeded by
a DOTS agent in sending to a peer DOTS agent that does not
respond (referred to as PROBING_RATE parameter in CoAP).
This is an optional attribute.
max-retransmit: Maximum number of retransmissions for a message
(referred to as MAX_RETRANSMIT parameter in CoAP).
This is an optional attribute.
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ack-timeout: Timeout value in seconds used to calculate the
initial retransmission timeout value (referred to as
ACK_TIMEOUT parameter in CoAP).
This is an optional attribute.
ack-random-factor: Random factor used to influence the timing of
retransmissions (referred to as ACK_RANDOM_FACTOR parameter in
CoAP).
This is an optional attribute.
idle-config: Set of configuration parameters to use when no
mitigation is active. This attribute has the same structure as
'mitigating-config'.
Figure 20 shows an example of acceptable and current configuration
parameters on a DOTS server for DOTS signal channel session
configuration. The same acceptable configuration is used during
mitigation and idle times.
{
"ietf-dots-signal-channel:signal-config": {
"mitigating-config": {
"heartbeat-interval": {
"max-value": 240,
"min-value": 15,
"current-value": 30
},
"missing-hb-allowed": {
"max-value": 20,
"min-value": 3,
"current-value": 15
},
"probing-rate": {
"max-value": 20,
"min-value": 5,
"current-value": 15
},
"max-retransmit": {
"max-value": 15,
"min-value": 2,
"current-value": 3
},
"ack-timeout": {
"max-value-decimal": "30.00",
"min-value-decimal": "1.00",
"current-value-decimal": "2.00"
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},
"ack-random-factor": {
"max-value-decimal": "4.00",
"min-value-decimal": "1.10",
"current-value-decimal": "1.50"
}
},
"idle-config": {
"heartbeat-interval": {
"max-value": 240,
"min-value": 15,
"current-value": 30
},
"missing-hb-allowed": {
"max-value": 20,
"min-value": 3,
"current-value": 15
},
"probing-rate": {
"max-value": 20,
"min-value": 5,
"current-value": 15
},
"max-retransmit": {
"max-value": 15,
"min-value": 2,
"current-value": 3
},
"ack-timeout": {
"max-value-decimal": "30.00",
"min-value-decimal": "1.00",
"current-value-decimal": "2.00"
},
"ack-random-factor": {
"max-value-decimal": "4.00",
"min-value-decimal": "1.10",
"current-value-decimal": "1.50"
}
}
}
}
Figure 20: Example of a Configuration Response Body
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4.5.2. Convey DOTS Signal Channel Session Configuration
A PUT request (Figures 21 and 22) is used to convey the configuration
parameters for the signal channel (e.g., heartbeat interval, maximum
retransmissions). Message transmission parameters for CoAP are
defined in Section 4.8 of [RFC7252]. The RECOMMENDED values of
transmission parameter values are ack-timeout (2 seconds), max-
retransmit (3), and ack-random-factor (1.5). In addition to those
parameters, the RECOMMENDED specific DOTS transmission parameter
values are 'heartbeat-interval' (30 seconds) and 'missing-hb-allowed'
(15).
Note: heartbeat-interval should be tweaked to also assist DOTS
messages for NAT traversal (SIG-011 of [RFC8612]). According to
[RFC8085], heartbeat messages must not be sent more frequently
than once every 15 seconds and should use longer intervals when
possible. Furthermore, [RFC4787] recommends NATs to use a state
timeout of 2 minutes or longer, but experience shows that sending
packets every 15 to 30 seconds is necessary to prevent the
majority of middleboxes from losing state for UDP flows. From
that standpoint, the RECOMMENDED minimum heartbeat-interval is 15
seconds and the RECOMMENDED maximum heartbeat-interval is 240
seconds. The recommended value of 30 seconds is selected to
anticipate the expiry of NAT state.
A heartbeat-interval of 30 seconds may be considered as too chatty
in some deployments. For such deployments, DOTS agents may
negotiate longer heartbeat-interval values to prevent any network
overload with too frequent heartbeats.
Different heartbeat intervals can be defined for 'mitigating-
config' and 'idle-config' to reduce being too chatty during idle
times. If there is an on-path translator between the DOTS client
(standalone or part of a DOTS gateway) and the DOTS server, the
'mitigating-config' heartbeat-interval has to be smaller than the
translator session timeout. It is recommended that the 'idle-
config' heartbeat-interval is also smaller than the translator
session timeout to prevent translator traversal issues, or
disabled entirely. Means to discover the lifetime assigned by a
translator are out of scope.
Given that the size of the heartbeat request can not exceed
(heartbeat-interval * probing-rate) bytes, probing-rate should be
set appropriately to avoid slowing down heartbeat exchanges. For
example, probing-rate may be set to 2 * ("size of encrypted DOTS
heartbeat request"/heartbeat-interval) or (("size of encrypted
DOTS heartbeat request" + "average size of an encrypted mitigation
request")/heartbeat-interval). Absent any explicit configuration
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or inability to dynamically adjust probing-rate values
(Section 4.8.1 of [RFC7252]), DOTS agents use 5 bytes/second as a
default probing-rate value.
If the DOTS agent wishes to change the default values of message
transmission parameters, it SHOULD follow the guidance given in
Section 4.8.1 of [RFC7252]. The DOTS agents MUST use the negotiated
values for message transmission parameters and default values for
non-negotiated message transmission parameters.
The signal channel session configuration is applicable to a single
DOTS signal channel session between DOTS agents, so the 'cuid' Uri-
Path MUST NOT be used.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "config"
Uri-Path: "sid=123"
Content-Format: "application/dots+cbor"
{
...
}
Figure 21: PUT to Convey the DOTS Signal Channel Session
Configuration Data
The additional Uri-Path parameter to those defined in Table 1 is as
follows:
sid: Session Identifier is an identifier for the DOTS signal channel
session configuration data represented as an integer. This
identifier MUST be generated by DOTS clients. 'sid' values MUST
increase monotonically (when a new PUT is generated by a DOTS
client to convey the configuration parameters for the signal
channel).
This is a mandatory attribute.
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{
"ietf-dots-signal-channel:signal-config": {
"mitigating-config": {
"heartbeat-interval": {
"current-value": number
},
"missing-hb-allowed": {
"current-value": number
},
"probing-rate": {
"current-value": number
},
"max-retransmit": {
"current-value": number
},
"ack-timeout": {
"current-value-decimal": "string"
},
"ack-random-factor": {
"current-value-decimal": "string"
}
},
"idle-config": {
"heartbeat-interval": {
"current-value": number
},
"missing-hb-allowed": {
"current-value": number
},
"probing-rate": {
"current-value": number
},
"max-retransmit": {
"current-value": number
},
"ack-timeout": {
"current-value-decimal": "string"
},
"ack-random-factor": {
"current-value-decimal": "string"
}
}
}
}
Figure 22: PUT to Convey the DOTS Signal Channel Session
Configuration Data (Message Body Schema)
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The meaning of the parameters in the CBOR body (Figure 22) is defined
in Section 4.5.1.
At least one of the attributes 'heartbeat-interval', 'missing-hb-
allowed', 'probing-rate', 'max-retransmit', 'ack-timeout', and 'ack-
random-factor' MUST be present in the PUT request. Note that
'heartbeat-interval', 'missing-hb-allowed', 'probing-rate', 'max-
retransmit', 'ack-timeout', and 'ack-random-factor', if present, do
not need to be provided for both 'mitigating-config', and 'idle-
config' in a PUT request.
The PUT request with a higher numeric 'sid' value overrides the DOTS
signal channel session configuration data installed by a PUT request
with a lower numeric 'sid' value. To avoid maintaining a long list
of 'sid' requests from a DOTS client, the lower numeric 'sid' MUST be
automatically deleted and no longer available at the DOTS server.
Figure 23 shows a PUT request example to convey the configuration
parameters for the DOTS signal channel. In this example, the
heartbeat mechanism is disabled when no mitigation is active, while
the heartbeat interval is set to '30' when a mitigation is active.
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Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "config"
Uri-Path: "sid=123"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:signal-config": {
"mitigating-config": {
"heartbeat-interval": {
"current-value": 30
},
"missing-hb-allowed": {
"current-value": 15
},
"probing-rate": {
"current-value": 15
},
"max-retransmit": {
"current-value": 3
},
"ack-timeout": {
"current-value-decimal": "2.00"
},
"ack-random-factor": {
"current-value-decimal": "1.50"
}
},
"idle-config": {
"heartbeat-interval": {
"current-value": 0
},
"max-retransmit": {
"current-value": 3
},
"ack-timeout": {
"current-value-decimal": "2.00"
},
"ack-random-factor": {
"current-value-decimal": "1.50"
}
}
}
}
Figure 23: PUT to Convey the Configuration Parameters
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The DOTS server indicates the result of processing the PUT request
using CoAP response codes:
o If the request is missing a mandatory attribute, does not include
a 'sid' Uri-Path, or contains one or more invalid or unknown
parameters, 4.00 (Bad Request) MUST be returned in the response.
o If the DOTS server does not find the 'sid' parameter value
conveyed in the PUT request in its configuration data and if the
DOTS server has accepted the configuration parameters, then a
response code 2.01 (Created) MUST be returned in the response.
o If the DOTS server finds the 'sid' parameter value conveyed in the
PUT request in its configuration data and if the DOTS server has
accepted the updated configuration parameters, 2.04 (Changed) MUST
be returned in the response.
o If any of the 'heartbeat-interval', 'missing-hb-allowed',
'probing-rate', 'max-retransmit', 'target-protocol', 'ack-
timeout', and 'ack-random-factor' attribute values are not
acceptable to the DOTS server, 4.22 (Unprocessable Entity) MUST be
returned in the response. Upon receipt of this error code, the
DOTS client SHOULD retrieve the maximum and minimum attribute
values acceptable to the DOTS server (Section 4.5.1).
The DOTS client may re-try and send the PUT request with updated
attribute values acceptable to the DOTS server.
A DOTS client may issue a GET message with 'sid' Uri-Path parameter
to retrieve the negotiated configuration. The response does not need
to include 'sid' in its message body.
4.5.3. Configuration Freshness and Notifications
Max-Age Option (Section 5.10.5 of [RFC7252]) SHOULD be returned by a
DOTS server to associate a validity time with a configuration it
sends. This feature allows the update of the configuration data if a
change occurs at the DOTS server side. For example, the new
configuration may instruct a DOTS client to cease heartbeats or
reduce heartbeat frequency.
It is NOT RECOMMENDED to return a Max-Age Option set to 0.
Returning a Max-Age Option set to 2**32-1 is equivalent to
associating an infinite lifetime with the configuration.
If a non-zero value of Max-Age Option is received by a DOTS client,
it MUST issue a GET request with 'sid' Uri-Path parameter to retrieve
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the current and acceptable configuration before the expiry of the
value enclosed in the Max-Age option. This request is considered by
the client and the server as a means to refresh the configuration
parameters for the signal channel. When a DDoS attack is active,
refresh requests MUST NOT be sent by DOTS clients and the DOTS server
MUST NOT terminate the (D)TLS session after the expiry of the value
returned in Max-Age Option.
If Max-Age Option is not returned in a response, the DOTS client
initiates GET requests to refresh the configuration parameters each
60 seconds (Section 5.10.5 of [RFC7252]). To prevent such overload,
it is RECOMMENDED that DOTS servers return a Max-Age Option in GET
responses. Considerations related to which value to use and how such
value is set, are implementation- and deployment-specific.
If an Observe Option set to 0 is included in the configuration
request, the DOTS server sends notifications of any configuration
change (Section 4.2 of [RFC7641]).
If a DOTS server detects that a misbehaving DOTS client does not
contact the DOTS server after the expiry of Max-Age and retrieve the
signal channel configuration data, it MAY terminate the (D)TLS
session. A (D)TLS session is terminated by the receipt of an
authenticated message that closes the connection (e.g., a fatal alert
(Section 6 of [RFC8446])).
4.5.4. Delete DOTS Signal Channel Session Configuration
A DELETE request is used to delete the installed DOTS signal channel
session configuration data (Figure 24).
Header: DELETE (Code=0.04)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "config"
Uri-Path: "sid=123"
Figure 24: Delete Configuration
The DOTS server resets the DOTS signal channel session configuration
back to the default values and acknowledges a DOTS client's request
to remove the DOTS signal channel session configuration using 2.02
(Deleted) response code.
Upon bootstrapping or reboot, a DOTS client MAY send a DELETE request
to set the configuration parameters to default values. Such a
request does not include any 'sid'.
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4.6. Redirected Signaling
Redirected DOTS signaling is discussed in detail in Section 3.2.2 of
[I-D.ietf-dots-architecture].
If a DOTS server wants to redirect a DOTS client to an alternative
DOTS server for a signal session, then the response code 5.03
(Service Unavailable) will be returned in the response to the DOTS
client.
The DOTS server can return the error response code 5.03 in response
to a request from the DOTS client or convey the error response code
5.03 in a unidirectional notification response from the DOTS server.
The DOTS server in the error response conveys the alternate DOTS
server's FQDN, and the alternate DOTS server's IP address(es) values
in the CBOR body (Figure 25).
{
"ietf-dots-signal-channel:redirected-signal": {
"alt-server": "string",
"alt-server-record": [
"string"
]
}
Figure 25: Redirected Server Error Response Body Schema
The parameters are described below:
alt-server: FQDN of an alternate DOTS server.
This is a mandatory attribute.
alt-server-record: A list of IP addresses of an alternate DOTS
server.
This is an optional attribute.
The DOTS server returns the Time to live (TTL) of the alternate DOTS
server in a Max-Age Option. That is, the time interval that the
alternate DOTS server may be cached for use by a DOTS client. A Max-
Age Option set to 2**32-1 is equivalent to receiving an infinite TTL.
This value means that the alternate DOTS server is to be used until
the alternate DOTS server redirects the traffic with another 5.03
response which encloses an alternate server.
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A Max-Age Option set to '0' may be returned for redirecting
mitigation requests. Such value means that the redirection applies
only for the mitigation request in progress. Returning short TTL in
a Max-Age Option may adversely impact DOTS clients on slow links.
Returning short values should be avoided under such conditions.
If the alternate DOTS server TTL has expired, the DOTS client MUST
use the DOTS server(s), that was provisioned using means discussed in
Section 4.1. This fall back mechanism is triggered immediately upon
expiry of the TTL, except when a DDoS attack is active.
Requests issued by misbehaving DOTS clients which do not honor the
TTL conveyed in the Max-Age Option or react to explicit re-direct
messages can be rejected by DOTS servers.
Figure 26 shows a 5.03 response example to convey the DOTS alternate
server 'alt-server.example' together with its IP addresses
2001:db8:6401::1 and 2001:db8:6401::2.
{
"ietf-dots-signal-channel:redirected-signal": {
"alt-server": "alt-server.example",
"alt-server-record": [
"2001:db8:6401::1",
"2001:db8:6401::2"
]
}
Figure 26: Example of Redirected Server Error Response Body
When the DOTS client receives 5.03 response with an alternate server
included, it considers the current request as failed, but SHOULD try
re-sending the request to the alternate DOTS server. During a DDoS
attack, the DNS server may be the target of another DDoS attack,
alternate DOTS server's IP addresses conveyed in the 5.03 response
help the DOTS client skip DNS lookup of the alternate DOTS server, at
the cost of trusting the first DOTS server to provide accurate
information. The DOTS client can then try to establish a UDP or a
TCP session with the alternate DOTS server. The DOTS client MAY
implement a method to construct IPv4-embedded IPv6 addresses
[RFC6052]; this is required to handle the scenario where an IPv6-only
DOTS client communicates with an IPv4-only alternate DOTS server.
If the DOTS client has been redirected to a DOTS server to which it
has already communicated with within the last five (5) minutes, it
MUST ignore the redirection and try to contact other DOTS servers
listed in the local configuration or discovered using dynamic means
such as DHCP or SRV procedures [I-D.ietf-dots-server-discovery]. It
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is RECOMMENDED that DOTS clients support means to alert
administrators about redirect loops.
4.7. Heartbeat Mechanism
To provide an indication of signal health and distinguish an 'idle'
signal channel from a 'disconnected' or 'defunct' session, the DOTS
agent sends a heartbeat over the signal channel to maintain its half
of the channel (also, aligned with the "consents" recommendation in
Section 6 of [RFC8085]). The DOTS agent similarly expects a
heartbeat from its peer DOTS agent, and may consider a session
terminated in the prolonged absence of a peer agent heartbeat.
Concretely, while the communication between the DOTS agents is
otherwise quiescent, the DOTS client will probe the DOTS server to
ensure it has maintained cryptographic state and vice versa. Such
probes can also keep firewalls and/or stateful translators bindings
alive. This probing reduces the frequency of establishing a new
handshake when a DOTS signal needs to be conveyed to the DOTS server.
Implementation Note: Given that CoAP roles can be multiplexed over
the same session as discussed in [RFC7252] and already supported
by CoAP implementations, both the DOTS client and server can send
DOTS heartbeat requests.
The DOTS Heartbeat mechanism uses non-confirmable PUT requests
(Figure 27) with an expected 2.04 (Changed) Response Code
(Figure 28). This procedure occurs between a DOTS agent and its
immediate peer DOTS agent. As such, this PUT request MUST NOT be
relayed by a DOTS gateway. The PUT request used for DOTS heartbeat
MUST NOT have a 'cuid', 'cdid,' or 'mid' Uri-Path.
Header: PUT (Code=0.03)
Uri-Path: ".well-known"
Uri-Path: "dots"
Uri-Path: "hb"
Content-Format: "application/dots+cbor"
{
"ietf-dots-signal-channel:heartbeat": {
"peer-hb-status": true
}
}
Figure 27: PUT to Check Peer DOTS Agent is Responding
The mandatory 'peer-hb-status' attribute is set to 'true' (or
'false') to indicates that a DOTS agent is (or not) receiving
heartbeat messages from its peer in the last (2 * heartbeat-interval)
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period. Such information can be used by a peer DOTS agent to detect
or confirm connectivity issues and react accordingly. For example,
if a DOTS client receives 2.04 response for its heartbeat messages
but no server-initiated heartbeat messages, the DOTS client sets
'peer-hb-status' to 'false'. The DOTS server will need then to try
another strategy for sending the heartbeats (e.g., adjust the
heartbeat interval or send a server-initiated heartbeat immediately
after receiving a client-initiated heartbeat message).
Header: (Code=2.04)
Figure 28: Response to a DOTS Heartbeat Request
DOTS servers MAY trigger their heartbeat requests immediately after
receiving heartbeat probes from peer DOTS clients. As a reminder, it
is the responsibility of DOTS clients to ensure that on-path
translators/firewalls are maintaining a binding so that the same
external IP address and/or port number is retained for the DOTS
signal channel session.
Under normal traffic conditions (i.e., no attack is ongoing), if a
DOTS agent does not receive any response from the peer DOTS agent for
'missing-hb-allowed' number of consecutive heartbeat messages, it
concludes that the DOTS signal channel session is disconnected. The
DOTS client MUST then try to re-establish the DOTS signal channel
session, preferably by resuming the (D)TLS session.
Note: If a new DOTS signal channel session cannot be established,
the DOTS client SHOULD NOT retry to establish the DOTS signal
channel session more frequently than every 300 seconds (5 minutes)
and MUST NOT retry more frequently than every 60 seconds (1
minute). It is recommended that DOTS clients support means to
alert administrators about the failure to establish a (D)TLS
session.
In case of a massive DDoS attack that saturates the incoming link(s)
to the DOTS client, all traffic from the DOTS server to the DOTS
client will likely be dropped, although the DOTS server receives
heartbeat requests in addition to DOTS messages sent by the DOTS
client. In this scenario, DOTS clients MUST behave differently to
handle message transmission and DOTS signal channel session
liveliness during link saturation:
The DOTS client MUST NOT consider the DOTS signal channel session
terminated even after a maximum 'missing-hb-allowed' threshold is
reached. The DOTS client SHOULD keep on using the current DOTS
signal channel session to send heartbeat requests over it, so that
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the DOTS server knows the DOTS client has not disconnected the
DOTS signal channel session.
After the maximum 'missing-hb-allowed' threshold is reached, the
DOTS client SHOULD try to establish a new DOTS signal channel
session. The DOTS client SHOULD send mitigation requests over the
current DOTS signal channel session and, in parallel, send the
mitigation requests over the new DOTS signal channel session.
This may be handled, for example, by resumption of the (D)TLS
session or using 0-RTT mode in DTLS 1.3 to piggyback the
mitigation request in the ClientHello message.
As soon as the link is no longer saturated, if traffic from the
DOTS server reaches the DOTS client over the current DOTS signal
channel session, the DOTS client can stop the new DOTS signal
channel session attempt or if a new DOTS signal channel session is
successful then disconnect the current DOTS signal channel
session.
If the DOTS server receives traffic from the peer DOTS client (e.g.,
peer DOTS client initiated heartbeats) but maximum 'missing-hb-
allowed' threshold is reached, the DOTS server MUST NOT consider the
DOTS signal channel session disconnected. The DOTS server MUST keep
on using the current DOTS signal channel session so that the DOTS
client can send mitigation requests over the current DOTS signal
channel session. In this case, the DOTS server can identify the DOTS
client is under attack and the inbound link to the DOTS client
(domain) is saturated. Furthermore, if the DOTS server does not
receive a mitigation request from the DOTS client, it implies the
DOTS client has not detected the attack or, if an attack mitigation
is in progress, it implies the applied DDoS mitigation actions are
not yet effective to handle the DDoS attack volume.
If the DOTS server does not receive any traffic from the peer DOTS
client during the time span required to exhaust the maximum 'missing-
hb-allowed' threshold, the DOTS server concludes the session is
disconnected. The DOTS server can then trigger pre-configured
mitigation requests for this DOTS client (if any).
In DOTS over TCP, the sender of a DOTS heartbeat message has to allow
up to 'heartbeat-interval' seconds when waiting for a heartbeat
reply. When a failure is detected by a DOTS client, it proceeds with
the session recovery following the same approach as the one used for
unreliable transports.
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5. DOTS Signal Channel YANG Modules
This document defines a YANG [RFC7950] module for DOTS mitigation
scope, DOTS signal channel session configuration data, DOTS
redirection signaling, and DOTS heartbeats.
This YANG module (ietf-dots-signal-channel) defines the DOTS client
interaction with the DOTS server as seen by the DOTS client. A DOTS
server is allowed to update the non-configurable 'ro' entities in the
responses. This YANG module is not intended to be used via NETCONF/
RESTCONF for DOTS server management purposes; such module is out of
the scope of this document. It serves only to provide a data model
and encoding, but not a management data model.
A companion YANG module is defined to include a collection of types
defined by IANA: "iana-dots-signal-channel" (Section 5.2).
5.1. Tree Structure
This document defines the YANG module "ietf-dots-signal-channel"
(Section 5.3), which has the following tree structure. A DOTS signal
message can be a mitigation, a configuration, a redirect, or a
heartbeat message.
module: ietf-dots-signal-channel
+--rw dots-signal
+--rw (message-type)?
+--:(mitigation-scope)
| +--rw scope* [cuid mid]
| +--rw cdid? string
| +--rw cuid string
| +--rw mid uint32
| +--rw target-prefix* inet:ip-prefix
| +--rw target-port-range* [lower-port]
| | +--rw lower-port inet:port-number
| | +--rw upper-port? inet:port-number
| +--rw target-protocol* uint8
| +--rw target-fqdn* inet:domain-name
| +--rw target-uri* inet:uri
| +--rw alias-name* string
| +--rw lifetime? int32
| +--rw trigger-mitigation? boolean
| +--ro mitigation-start? uint64
| +--ro status? iana-signal:status
| +--ro conflict-information
| | +--ro conflict-status? iana-signal:conflict-status
| | +--ro conflict-cause? iana-signal:conflict-cause
| | +--ro retry-timer? uint32
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| | +--ro conflict-scope
| | +--ro target-prefix* inet:ip-prefix
| | +--ro target-port-range* [lower-port]
| | | +--ro lower-port inet:port-number
| | | +--ro upper-port? inet:port-number
| | +--ro target-protocol* uint8
| | +--ro target-fqdn* inet:domain-name
| | +--ro target-uri* inet:uri
| | +--ro alias-name* string
| | +--ro acl-list* [acl-name]
| | | +--ro acl-name
| | | | -> /ietf-data:dots-data/dots-client/acls/
| | | | acl/name
| | | +--ro acl-type?
| | | -> /ietf-data:dots-data/dots-client/acls/
| | | acl/type
| | +--ro mid? -> ../../../mid
| +--ro bytes-dropped? yang:zero-based-counter64
| +--ro bps-dropped? yang:gauge64
| +--ro pkts-dropped? yang:zero-based-counter64
| +--ro pps-dropped? yang:gauge64
| +--rw attack-status? iana-signal:attack-status
+--:(signal-config)
| +--rw sid uint32
| +--rw mitigating-config
| | +--rw heartbeat-interval
| | | +--ro max-value? uint16
| | | +--ro min-value? uint16
| | | +--rw current-value? uint16
| | +--rw missing-hb-allowed
| | | +--ro max-value? uint16
| | | +--ro min-value? uint16
| | | +--rw current-value? uint16
| | +--rw probing-rate
| | | +--ro max-value? uint16
| | | +--ro min-value? uint16
| | | +--rw current-value? uint16
| | +--rw max-retransmit
| | | +--ro max-value? uint16
| | | +--ro min-value? uint16
| | | +--rw current-value? uint16
| | +--rw ack-timeout
| | | +--ro max-value-decimal? decimal64
| | | +--ro min-value-decimal? decimal64
| | | +--rw current-value-decimal? decimal64
| | +--rw ack-random-factor
| | +--ro max-value-decimal? decimal64
| | +--ro min-value-decimal? decimal64
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| | +--rw current-value-decimal? decimal64
| +--rw idle-config
| +--rw heartbeat-interval
| | +--ro max-value? uint16
| | +--ro min-value? uint16
| | +--rw current-value? uint16
| +--rw missing-hb-allowed
| | +--ro max-value? uint16
| | +--ro min-value? uint16
| | +--rw current-value? uint16
| +--rw probing-rate
| | +--ro max-value? uint16
| | +--ro min-value? uint16
| | +--rw current-value? uint16
| +--rw max-retransmit
| | +--ro max-value? uint16
| | +--ro min-value? uint16
| | +--rw current-value? uint16
| +--rw ack-timeout
| | +--ro max-value-decimal? decimal64
| | +--ro min-value-decimal? decimal64
| | +--rw current-value-decimal? decimal64
| +--rw ack-random-factor
| +--ro max-value-decimal? decimal64
| +--ro min-value-decimal? decimal64
| +--rw current-value-decimal? decimal64
+--:(redirected-signal)
| +--ro alt-server string
| +--ro alt-server-record* inet:ip-address
+--:(heartbeat)
+--rw peer-hb-status boolean
5.2. IANA DOTS Signal Channel YANG Module
<CODE BEGINS> file "iana-dots-signal-channel@2019-01-17.yang"
module iana-dots-signal-channel {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:iana-dots-signal-channel";
prefix iana-signal;
organization
"IANA";
contact
"Internet Assigned Numbers Authority
Postal: ICANN
12025 Waterfront Drive, Suite 300
Los Angeles, CA 90094-2536
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United States of America
Tel: +1 310 301 5800
<mailto:iana@iana.org>";
description
"This module contains a collection of YANG data types defined
by IANA and used for DOTS signal channel protocol.
Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
revision 2019-01-17 {
description
"Initial revision.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel Specification";
}
typedef status {
type enumeration {
enum attack-mitigation-in-progress {
value 1;
description
"Attack mitigation setup is in progress (e.g., changing
the network path to re-route the inbound traffic
to DOTS mitigator).";
}
enum attack-successfully-mitigated {
value 2;
description
"Attack is being successfully mitigated (e.g., traffic
is redirected to a DDoS mitigator and attack
traffic is dropped or blackholed).";
}
enum attack-stopped {
value 3;
description
"Attack has stopped and the DOTS client can
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withdraw the mitigation request.";
}
enum attack-exceeded-capability {
value 4;
description
"Attack has exceeded the mitigation provider
capability.";
}
enum dots-client-withdrawn-mitigation {
value 5;
description
"DOTS client has withdrawn the mitigation
request and the mitigation is active but
terminating.";
}
enum attack-mitigation-terminated {
value 6;
description
"Attack mitigation is now terminated.";
}
enum attack-mitigation-withdrawn {
value 7;
description
"Attack mitigation is withdrawn.";
}
enum attack-mitigation-signal-loss {
value 8;
description
"Attack mitigation will be triggered
for the mitigation request only when
the DOTS signal channel session is lost.";
}
}
description
"Enumeration for status reported by the DOTS server.";
}
typedef conflict-status {
type enumeration {
enum request-inactive-other-active {
value 1;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients.
This mitigation request is currently inactive
until the conflicts are resolved. Another
mitigation request is active.";
}
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enum request-active {
value 2;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients.
This mitigation request is currently active.";
}
enum all-requests-inactive {
value 3;
description
"DOTS Server has detected conflicting mitigation
requests from different DOTS clients. All
conflicting mitigation requests are inactive.";
}
}
description
"Enumeration for conflict status.";
}
typedef conflict-cause {
type enumeration {
enum overlapping-targets {
value 1;
description
"Overlapping targets. conflict-scope provides
more details about the exact conflict.";
}
enum conflict-with-acceptlist {
value 2;
description
"Conflicts with an existing accept-list.
This code is returned when the DDoS mitigation
detects that some of the source addresses/prefixes
listed in the accept-list ACLs are actually
attacking the target.";
}
enum cuid-collision {
value 3;
description
"Conflicts with the cuid used by another
DOTS client.";
}
}
description
"Enumeration for conflict causes.";
}
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typedef attack-status {
type enumeration {
enum under-attack {
value 1;
description
"The DOTS client determines that it is still under
attack.";
}
enum attack-successfully-mitigated {
value 2;
description
"The DOTS client determines that the attack is
successfully mitigated.";
}
}
description
"Enumeration for attack status codes.";
}
}
<CODE ENDS>
5.3. IETF DOTS Signal Channel YANG Module
This module uses the common YANG types defined in [RFC6991] and types
defined in [I-D.ietf-dots-data-channel].
<CODE BEGINS> file "ietf-dots-signal-channel@2019-11-13.yang"
module ietf-dots-signal-channel {
yang-version 1.1;
namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel";
prefix signal;
import ietf-inet-types {
prefix inet;
reference "Section 4 of RFC 6991";
}
import ietf-yang-types {
prefix yang;
reference "Section 3 of RFC 6991";
}
import ietf-dots-data-channel {
prefix ietf-data;
reference
"RFC YYYY: Distributed Denial-of-Service Open Threat Signaling
(DOTS) Data Channel Specification";
}
import iana-dots-signal-channel {
prefix iana-signal;
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}
organization
"IETF DDoS Open Threat Signaling (DOTS) Working Group";
contact
"WG Web: <https://datatracker.ietf.org/wg/dots/>
WG List: <mailto:dots@ietf.org>
Editor: Konda, Tirumaleswar Reddy
<mailto:TirumaleswarReddy_Konda@McAfee.com>
Editor: Mohamed Boucadair
<mailto:mohamed.boucadair@orange.com>
Author: Prashanth Patil
<mailto:praspati@cisco.com>
Author: Andrew Mortensen
<mailto:amortensen@arbor.net>
Author: Nik Teague
<mailto:nteague@verisign.com>";
description
"This module contains YANG definition for the signaling
messages exchanged between a DOTS client and a DOTS server.
Copyright (c) 2019 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject
to the license terms contained in, the Simplified BSD License
set forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see
the RFC itself for full legal notices.";
revision 2019-11-13 {
description
"Initial revision.";
reference
"RFC XXXX: Distributed Denial-of-Service Open Threat
Signaling (DOTS) Signal Channel Specification";
}
/*
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* Groupings
*/
grouping mitigation-scope {
description
"Specifies the scope of the mitigation request.";
list scope {
key "cuid mid";
description
"The scope of the request.";
leaf cdid {
type string;
description
"The cdid should be included by a server-domain
DOTS gateway to propagate the client domain
identification information from the
gateway's client-facing-side to the gateway's
server-facing-side, and from the gateway's
server-facing-side to the DOTS server.
It may be used by the final DOTS server
for policy enforcement purposes.";
}
leaf cuid {
type string;
description
"A unique identifier that is
generated by a DOTS client to prevent
request collisions. It is expected that the
cuid will remain consistent throughout the
lifetime of the DOTS client.";
}
leaf mid {
type uint32;
description
"Mitigation request identifier.
This identifier must be unique for each mitigation
request bound to the DOTS client.";
}
uses ietf-data:target;
leaf-list alias-name {
type string;
description
"An alias name that points to a resource.";
}
leaf lifetime {
type int32;
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units "seconds";
default "3600";
description
"Indicates the lifetime of the mitigation request.
A lifetime of '0' in a mitigation request is an
invalid value.
A lifetime of negative one (-1) indicates indefinite
lifetime for the mitigation request.";
}
leaf trigger-mitigation {
type boolean;
default "true";
description
"If set to 'false', DDoS mitigation will not be
triggered unless the DOTS signal channel
session is lost.";
}
leaf mitigation-start {
type uint64;
config false;
description
"Mitigation start time is represented in seconds
relative to 1970-01-01T00:00:00Z in UTC time.";
}
leaf status {
type iana-signal:status;
config false;
description
"Indicates the status of a mitigation request.
It must be included in responses only.";
}
container conflict-information {
config false;
description
"Indicates that a conflict is detected.
Must only be used for responses.";
leaf conflict-status {
type iana-signal:conflict-status;
description
"Indicates the conflict status.";
}
leaf conflict-cause {
type iana-signal:conflict-cause;
description
"Indicates the cause of the conflict.";
}
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leaf retry-timer {
type uint32;
units "seconds";
description
"The DOTS client must not re-send the
same request that has a conflict before the expiry of
this timer.";
}
container conflict-scope {
description
"Provides more information about the conflict scope.";
uses ietf-data:target {
when "../conflict-cause = 'overlapping-targets'";
}
leaf-list alias-name {
when "../../conflict-cause = 'overlapping-targets'";
type string;
description
"Conflicting alias-name.";
}
list acl-list {
when "../../conflict-cause = 'conflict-with-acceptlist'";
key "acl-name";
description
"List of conflicting ACLs as defined in the DOTS data
channel. These ACLs are uniquely defined by
cuid and acl-name.";
leaf acl-name {
type leafref {
path "/ietf-data:dots-data/ietf-data:dots-client/"
+ "ietf-data:acls/ietf-data:acl/ietf-data:name";
}
description
"Reference to the conflicting ACL name bound to
a DOTS client.";
}
leaf acl-type {
type leafref {
path "/ietf-data:dots-data/ietf-data:dots-client/"
+ "ietf-data:acls/ietf-data:acl/ietf-data:type";
}
description
"Reference to the conflicting ACL type bound to
a DOTS client.";
}
}
leaf mid {
when "../../conflict-cause = 'overlapping-targets'";
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type leafref {
path "../../../mid";
}
description
"Reference to the conflicting 'mid' bound to
the same DOTS client.";
}
}
}
leaf bytes-dropped {
type yang:zero-based-counter64;
units "bytes";
config false;
description
"The total dropped byte count for the mitigation
request since the attack mitigation is triggered.
The count wraps around when it reaches the maximum value
of counter64 for dropped bytes.";
}
leaf bps-dropped {
type yang:gauge64;
config false;
description
"The average number of dropped bits per second for
the mitigation request since the attack
mitigation is triggered. This should be over
five-minute intervals (that is, measuring bytes
into five-minute buckets and then averaging these
buckets over the time since the mitigation was
triggered).";
}
leaf pkts-dropped {
type yang:zero-based-counter64;
config false;
description
"The total number of dropped packet count for the
mitigation request since the attack mitigation is
triggered. The count wraps around when it reaches
the maximum value of counter64 for dropped packets.";
}
leaf pps-dropped {
type yang:gauge64;
config false;
description
"The average number of dropped packets per second
for the mitigation request since the attack
mitigation is triggered. This should be over
five-minute intervals (that is, measuring packets
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into five-minute buckets and then averaging these
buckets over the time since the mitigation was
triggered).";
}
leaf attack-status {
type iana-signal:attack-status;
description
"Indicates the status of an attack as seen by the
DOTS client.";
}
}
}
grouping config-parameters {
description
"Subset of DOTS signal channel session configuration.";
container heartbeat-interval {
description
"DOTS agents regularly send heartbeats to each other
after mutual authentication is successfully
completed in order to keep the DOTS signal channel
open.";
leaf max-value {
type uint16;
units "seconds";
config false;
description
"Maximum acceptable heartbeat-interval value.";
}
leaf min-value {
type uint16;
units "seconds";
config false;
description
"Minimum acceptable heartbeat-interval value.";
}
leaf current-value {
type uint16;
units "seconds";
default "30";
description
"Current heartbeat-interval value.
'0' means that heartbeat mechanism is deactivated.";
}
}
container missing-hb-allowed {
description
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"Maximum number of missing heartbeats allowed.";
leaf max-value {
type uint16;
config false;
description
"Maximum acceptable missing-hb-allowed value.";
}
leaf min-value {
type uint16;
config false;
description
"Minimum acceptable missing-hb-allowed value.";
}
leaf current-value {
type uint16;
default "15";
description
"Current missing-hb-allowed value.";
}
}
container probing-rate {
description
"The limit for sending non-confirmable messages with
no response.";
leaf max-value {
type uint16;
units "byte/second";
config false;
description
"Maximum acceptable probing-rate value.";
}
leaf min-value {
type uint16;
units "byte/second";
config false;
description
"Minimum acceptable probing-rate value.";
}
leaf current-value {
type uint16;
units "byte/second";
default "5";
description
"Current probing-rate value.";
}
}
container max-retransmit {
description
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"Maximum number of retransmissions of a Confirmable
message.";
leaf max-value {
type uint16;
config false;
description
"Maximum acceptable max-retransmit value.";
}
leaf min-value {
type uint16;
config false;
description
"Minimum acceptable max-retransmit value.";
}
leaf current-value {
type uint16;
default "3";
description
"Current max-retransmit value.";
}
}
container ack-timeout {
description
"Initial retransmission timeout value.";
leaf max-value-decimal {
type decimal64 {
fraction-digits 2;
}
units "seconds";
config false;
description
"Maximum ack-timeout value.";
}
leaf min-value-decimal {
type decimal64 {
fraction-digits 2;
}
units "seconds";
config false;
description
"Minimum ack-timeout value.";
}
leaf current-value-decimal {
type decimal64 {
fraction-digits 2;
}
units "seconds";
default "2";
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description
"Current ack-timeout value.";
}
}
container ack-random-factor {
description
"Random factor used to influence the timing of
retransmissions.";
leaf max-value-decimal {
type decimal64 {
fraction-digits 2;
}
config false;
description
"Maximum acceptable ack-random-factor value.";
}
leaf min-value-decimal {
type decimal64 {
fraction-digits 2;
}
config false;
description
"Minimum acceptable ack-random-factor value.";
}
leaf current-value-decimal {
type decimal64 {
fraction-digits 2;
}
default "1.5";
description
"Current ack-random-factor value.";
}
}
}
grouping signal-config {
description
"DOTS signal channel session configuration.";
leaf sid {
type uint32;
mandatory true;
description
"An identifier for the DOTS signal channel
session configuration data.";
}
container mitigating-config {
description
"Configuration parameters to use when a mitigation
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is active.";
uses config-parameters;
}
container idle-config {
description
"Configuration parameters to use when no mitigation
is active.";
uses config-parameters;
}
}
grouping redirected-signal {
description
"Grouping for the redirected signaling.";
leaf alt-server {
type string;
config false;
mandatory true;
description
"FQDN of an alternate server.";
}
leaf-list alt-server-record {
type inet:ip-address;
config false;
description
"List of records for the alternate server.";
}
}
/*
* Main Container for DOTS Signal Channel
*/
container dots-signal {
description
"Main container for DOTS signal message.
A DOTS signal message can be a mitigation, a configuration,
or a redirected signal message.";
choice message-type {
description
"Can be a mitigation, a configuration, or a redirect
message.";
case mitigation-scope {
description
"Mitigation scope of a mitigation message.";
uses mitigation-scope;
}
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case signal-config {
description
"Configuration message.";
uses signal-config;
}
case redirected-signal {
description
"Redirected signaling.";
uses redirected-signal;
}
case heartbeat {
description
"DOTS heartbeats.";
leaf peer-hb-status {
type boolean;
mandatory true;
description
"Indicates whether a DOTS agent receives heartbeats
from its peer. The value is set to 'true' if the
DOTS agent is receiving heartbeat messages
from its peer.";
}
}
}
}
}
<CODE ENDS>
6. YANG/JSON Mapping Parameters to CBOR
All parameters in the payload of the DOTS signal channel MUST be
mapped to CBOR types as shown in Table 4 and are assigned an integer
key to save space.
o Note: Implementers must check that the mapping output provided by
their YANG-to-CBOR encoding schemes is aligned with the content of
Table 4. For example, some CBOR and JSON types for enumerations
and the 64-bit quantities can differ depending on the encoder
used.
The CBOR key values are divided into two types: comprehension-
required and comprehension-optional. DOTS agents can safely ignore
comprehension-optional values they don't understand, but cannot
successfully process a request if it contains comprehension-required
values that are not understood. The 4.00 response SHOULD include a
diagnostic payload describing the unknown comprehension-required CBOR
key values. The initial set of CBOR key values defined in this
specification are of type comprehension-required.
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+----------------------+-------------+-----+---------------+--------+
| Parameter Name | YANG | CBOR| CBOR Major | JSON |
| | Type | Key | Type & | Type |
| | | | Information | |
+----------------------+-------------+-----+---------------+--------+
| ietf-dots-signal-cha | | | | |
| nnel:mitigation-scope| container | 1 | 5 map | Object |
| scope | list | 2 | 4 array | Array |
| cdid | string | 3 | 3 text string | String |
| cuid | string | 4 | 3 text string | String |
| mid | uint32 | 5 | 0 unsigned | Number |
| target-prefix | leaf-list | 6 | 4 array | Array |
| | inet: | | | |
| | ip-prefix | | 3 text string | String |
| target-port-range | list | 7 | 4 array | Array |
| lower-port | inet: | | | |
| | port-number| 8 | 0 unsigned | Number |
| upper-port | inet: | | | |
| | port-number| 9 | 0 unsigned | Number |
| target-protocol | leaf-list | 10 | 4 array | Array |
| | uint8 | | 0 unsigned | Number |
| target-fqdn | leaf-list | 11 | 4 array | Array |
| | inet: | | | |
| | domain-name| | 3 text string | String |
| target-uri | leaf-list | 12 | 4 array | Array |
| | inet:uri | | 3 text string | String |
| alias-name | leaf-list | 13 | 4 array | Array |
| | string | | 3 text string | String |
| lifetime | int32 | 14 | 0 unsigned | Number |
| | | | 1 negative | Number |
| mitigation-start | uint64 | 15 | 0 unsigned | String |
| status | enumeration | 16 | 0 unsigned | String |
| conflict-information | container | 17 | 5 map | Object |
| conflict-status | enumeration | 18 | 0 unsigned | String |
| conflict-cause | enumeration | 19 | 0 unsigned | String |
| retry-timer | uint32 | 20 | 0 unsigned | Number |
| conflict-scope | container | 21 | 5 map | Object |
| acl-list | list | 22 | 4 array | Array |
| acl-name | leafref | 23 | 3 text string | String |
| acl-type | leafref | 24 | 3 text string | String |
| bytes-dropped | yang:zero- | | | |
| | based- | | | |
| | counter64 | 25 | 0 unsigned | String |
| bps-dropped | yang:gauge64| 26 | 0 unsigned | String |
| pkts-dropped | yang:zero- | | | |
| | based- | | | |
| | counter64 | 27 | 0 unsigned | String |
| pps-dropped | yang:gauge64| 28 | 0 unsigned | String |
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| attack-status | enumeration | 29 | 0 unsigned | String |
| ietf-dots-signal- | | | | |
| channel:signal-config| container | 30 | 5 map | Object |
| sid | uint32 | 31 | 0 unsigned | Number |
| mitigating-config | container | 32 | 5 map | Object |
| heartbeat-interval | container | 33 | 5 map | Object |
| max-value | uint16 | 34 | 0 unsigned | Number |
| min-value | uint16 | 35 | 0 unsigned | Number |
| current-value | uint16 | 36 | 0 unsigned | Number |
| missing-hb-allowed | container | 37 | 5 map | Object |
| max-retransmit | container | 38 | 5 map | Object |
| ack-timeout | container | 39 | 5 map | Object |
| ack-random-factor | container | 40 | 5 map | Object |
| max-value-decimal | decimal64 | 41 | 6 tag 4 | |
| | | | [-2, integer]| String |
| min-value-decimal | decimal64 | 42 | 6 tag 4 | |
| | | | [-2, integer]| String |
| current-value-decimal| decimal64 | 43 | 6 tag 4 | |
| | | | [-2, integer]| String |
| idle-config | container | 44 | 5 map | Object |
| trigger-mitigation | boolean | 45 | 7 bits 20 | False |
| | | | 7 bits 21 | True |
| ietf-dots-signal-cha | | | | |
|nnel:redirected-signal| container | 46 | 5 map | Object |
| alt-server | string | 47 | 3 text string | String |
| alt-server-record | leaf-list | 48 | 4 array | Array |
| | inet: | | | |
| | ip-address | | 3 text string | String |
| ietf-dots-signal-cha | | | | |
| nnel:heartbeat | container | 49 | 5 map | Object |
| probing-rate | container | 50 | 5 map | Object |
| peer-hb-status | boolean | 51 | 7 bits 20 | False |
| | | | 7 bits 21 | True |
+----------------------+-------------+-----+---------------+--------+
Table 4: CBOR Key Values Used in DOTS Signal Channel Messages & Their
Mappings to JSON and YANG
7. (D)TLS Protocol Profile and Performance Considerations
7.1. (D)TLS Protocol Profile
This section defines the (D)TLS protocol profile of DOTS signal
channel over (D)TLS and DOTS data channel over TLS.
There are known attacks on (D)TLS, such as man-in-the-middle and
protocol downgrade attacks. These are general attacks on (D)TLS and,
as such, they are not specific to DOTS over (D)TLS; refer to the
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(D)TLS RFCs for discussion of these security issues. DOTS agents
MUST adhere to the (D)TLS implementation recommendations and security
considerations of [RFC7525] except with respect to (D)TLS version.
Since DOTS signal channel encryption relying upon (D)TLS is virtually
a green-field deployment, DOTS agents MUST implement only (D)TLS 1.2
or later.
When a DOTS client is configured with a domain name of the DOTS
server, and connects to its configured DOTS server, the server may
present it with a PKIX certificate. In order to ensure proper
authentication, a DOTS client MUST verify the entire certification
path per [RFC5280]. Additionally, the DOTS client MUST use [RFC6125]
validation techniques to compare the domain name with the certificate
provided. Certification authorities that issue DOTS server
certificates SHOULD support the DNS-ID and SRV-ID identifier types.
DOTS server SHOULD prefer the use of DNS-ID and SRV-ID over CN-ID
identifier types in certificate requests (as described in Section 2.3
of [RFC6125]) and the wildcard character '*' SHOULD NOT be included
in the presented identifier. DOTS doesn't use URI-IDs for server
identity verification.
A key challenge to deploying DOTS is the provisioning of DOTS
clients, including the distribution of keying material to DOTS
clients to enable the required mutual authentication of DOTS agents.
Enrollment over Secure Transport (EST) [RFC7030] defines a method of
certificate enrollment by which domains operating DOTS servers may
provide DOTS clients with all the necessary cryptographic keying
material, including a private key and a certificate to authenticate
themselves. One deployment option is DOTS clients behave as EST
clients for certificate enrollment from an EST server provisioned by
the mitigation provider. This document does not specify which EST or
other mechanism the DOTS client uses to achieve initial enrollment.
The Server Name Indication (SNI) extension [RFC6066] defines a
mechanism for a client to tell a (D)TLS server the name of the server
it wants to contact. This is a useful extension for hosting
environments where multiple virtual servers are reachable over a
single IP address. The DOTS client may or may not know if it is
interacting with a DOTS server in a virtual server hosting
environment, so the DOTS client SHOULD include the DOTS server FQDN
in the SNI extension.
Implementations compliant with this profile MUST implement all of the
following items:
o DTLS record replay detection (Section 3.3 of [RFC6347]) or an
equivalent mechanism to protect against replay attacks.
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o DTLS session resumption without server-side state to resume
session and convey the DOTS signal.
o At least one of raw public keys [RFC7250] or PSK handshake
[RFC4279] with (EC)DHE key exchange which reduces the size of the
ServerHello, and can be used by DOTS agents that cannot obtain
certificates.
Implementations compliant with this profile SHOULD implement all of
the following items to reduce the delay required to deliver a DOTS
signal channel message:
o TLS False Start [RFC7918] which reduces round-trips by allowing
the TLS client's second flight of messages (ChangeCipherSpec) to
also contain the DOTS signal. TLS False Start is formally defined
for use with TLS, but the same technique is applicable to DTLS as
well.
o Cached Information Extension [RFC7924] which avoids transmitting
the server's certificate and certificate chain if the client has
cached that information from a previous TLS handshake.
Compared to UDP, DOTS signal channel over TCP requires an additional
round-trip time (RTT) of latency to establish a TCP connection. DOTS
implementations are encouraged to implement TCP Fast Open [RFC7413]
to eliminate that RTT.
7.2. (D)TLS 1.3 Considerations
TLS 1.3 provides critical latency improvements for connection
establishment over TLS 1.2. The DTLS 1.3 protocol
[I-D.ietf-tls-dtls13] is based upon the TLS 1.3 protocol and provides
equivalent security guarantees. (D)TLS 1.3 provides two basic
handshake modes the DOTS signal channel can take advantage of:
o A full handshake mode in which a DOTS client can send a DOTS
mitigation request message after one round trip and the DOTS
server immediately responds with a DOTS mitigation response. This
assumes no packet loss is experienced.
o 0-RTT mode in which the DOTS client can authenticate itself and
send DOTS mitigation request messages in the first message, thus
reducing handshake latency. 0-RTT only works if the DOTS client
has previously communicated with that DOTS server, which is very
likely with the DOTS signal channel.
The DOTS client has to establish a (D)TLS session with the DOTS
server during 'idle' time and share a PSK.
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During a DDoS attack, the DOTS client can use the (D)TLS session
to convey the DOTS mitigation request message and, if there is no
response from the server after multiple retries, the DOTS client
can resume the (D)TLS session in 0-RTT mode using PSK.
DOTS servers that support (D)TLS 1.3 MAY allow DOTS clients to
send early data (0-RTT). DOTS clients MUST NOT send "CoAP Ping"
as early data; such messages MUST be rejected by DOTS servers.
Section 8 of [RFC8446] discusses some mechanisms to implement to
limit the impact of replay attacks on 0-RTT data. If the DOTS
server accepts 0-RTT, it MUST implement one of these mechanisms to
prevent replay at the TLS layer. A DOTS server can reject 0-RTT
by sending a TLS HelloRetryRequest.
The DOTS signal channel messages sent as early data by the DOTS
client are idempotent requests. As a reminder, the Message ID
(Section 3 of [RFC7252]) is changed each time a new CoAP request
is sent, and the Token (Section 5.3.1 of [RFC7252]) is randomized
in each CoAP request. The DOTS server(s) MUST use the Message ID
and the Token in the DOTS signal channel message to detect replay
of early data at the application layer, and accept 0-RTT data at
most once from the same DOTS client. This anti-replay defense
requires sharing the Message ID and the Token in the 0-RTT data
between DOTS servers in the DOTS server domain. DOTS servers do
not rely on transport coordinates to identify DOTS peers. As
specified in Section 4.4.1, DOTS servers couple the DOTS signal
channel sessions using the DOTS client identity and optionally the
'cdid' parameter value. Furthermore, 'mid' value is monotonically
increased by the DOTS client for each mitigation request,
attackers replaying mitigation requests with lower numeric 'mid'
values and overlapping scopes with mitigation requests having
higher numeric 'mid' values will be rejected systematically by the
DOTS server. Likewise, 'sid' value is monotonically increased by
the DOTS client for each configuration request (Section 4.5.2),
attackers replaying configuration requests with lower numeric
'sid' values will be rejected by the DOTS server if it maintains a
higher numeric 'sid' value for this DOTS client.
Owing to the aforementioned protections, all DOTS signal channel
requests are safe to transmit in TLS 1.3 as early data. Refer to
[I-D.boucadair-dots-earlydata] for more details.
A simplified TLS 1.3 handshake with 0-RTT DOTS mitigation request
message exchange is shown in Figure 29.
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DOTS Client DOTS Server
ClientHello
(0-RTT DOTS signal message)
-------->
ServerHello
{EncryptedExtensions}
{Finished}
<-------- [DOTS signal message]
(end_of_early_data)
{Finished} -------->
[DOTS signal message] <-------> [DOTS signal message]
Note that:
() Indicates messages protected 0-RTT keys
{} Indicates messages protected using handshake keys
[] Indicates messages protected using 1-RTT keys
Figure 29: A Simplified TLS 1.3 Handshake with 0-RTT
7.3. DTLS MTU and Fragmentation
To avoid DOTS signal message fragmentation and the subsequent
decreased probability of message delivery, DOTS agents MUST ensure
that the DTLS record fit within a single datagram. As a reminder,
DTLS handles fragmentation and reassembly only for handshake messages
and not for the application data (Section 4.1.1 of [RFC6347]). If
the PMTU cannot be discovered, DOTS agents MUST assume a PMTU of 1280
bytes, as IPv6 requires that every link in the Internet have an MTU
of 1280 octets or greater as specified in [RFC8200]. If IPv4 support
on legacy or otherwise unusual networks is a consideration and the
PMTU is unknown, DOTS implementations MAY assume on a PMTU of 576
bytes for IPv4 datagrams, as every IPv4 host must be capable of
receiving a packet whose length is equal to 576 bytes as discussed in
[RFC0791] and [RFC1122].
The DOTS client must consider the amount of record expansion expected
by the DTLS processing when calculating the size of CoAP message that
fits within the path MTU. Path MTU MUST be greater than or equal to
[CoAP message size + DTLS 1.2 overhead of 13 octets + authentication
overhead of the negotiated DTLS cipher suite + block padding]
(Section 4.1.1.1 of [RFC6347]). If the total request size exceeds
the path MTU then the DOTS client MUST split the DOTS signal into
separate messages; for example, the list of addresses in the 'target-
prefix' parameter could be split into multiple lists and each list
conveyed in a new PUT request.
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Implementation Note: DOTS choice of message size parameters works
well with IPv6 and with most of today's IPv4 paths. However, with
IPv4, it is harder to safely make sure that there is no IP
fragmentation. If the IPv4 path MTU is unknown, implementations may
want to limit themselves to more conservative IPv4 datagram sizes
such as 576 bytes, as per [RFC0791].
8. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients
(D)TLS based upon client certificate can be used for mutual
authentication between DOTS agents. If, for example, a DOTS gateway
is involved, DOTS clients and DOTS gateways must perform mutual
authentication; only authorized DOTS clients are allowed to send DOTS
signals to a DOTS gateway. The DOTS gateway and the DOTS server must
perform mutual authentication; a DOTS server only allows DOTS signal
channel messages from an authorized DOTS gateway, thereby creating a
two-link chain of transitive authentication between the DOTS client
and the DOTS server.
The DOTS server should support certificate-based client
authentication. The DOTS client should respond to the DOTS server's
TLS CertificateRequest message with the PKIX certificate held by the
DOTS client. DOTS client certificate validation must be performed as
per [RFC5280] and the DOTS client certificate must conform to the
[RFC5280] certificate profile. If a DOTS client does not support TLS
client certificate authentication, it must support pre-shared key
based or raw public key based client authentication.
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+---------------------------------------------+
| example.com domain +---------+ |
| | AAA | |
| +---------------+ | Server | |
| | Application | +------+--+ |
| | server +<---------------+ ^ |
| | (DOTS client) | | | |
| +---------------+ | | |
| V V | example.net domain
| +-----+----+--+ | +---------------+
| +--------------+ | | | | |
| | Guest +<----x---->+ DOTS +<------>+ DOTS |
| | (DOTS client)| | gateway | | | server |
| +--------------+ | | | | |
| +----+--------+ | +---------------+
| ^ |
| | |
| +----------------+ | |
| | DDoS detector | | |
| | (DOTS client) +<-------------+ |
| +----------------+ |
+---------------------------------------------+
Figure 30: Example of Authentication and Authorization of DOTS Agents
In the example depicted in Figure 30, the DOTS gateway and DOTS
clients within the 'example.com' domain mutually authenticate. After
the DOTS gateway validates the identity of a DOTS client, it
communicates with the AAA server in the 'example.com' domain to
determine if the DOTS client is authorized to request DDoS
mitigation. If the DOTS client is not authorized, a 4.01
(Unauthorized) is returned in the response to the DOTS client. In
this example, the DOTS gateway only allows the application server and
DDoS attack detector to request DDoS mitigation, but does not permit
the user of type 'guest' to request DDoS mitigation.
Also, DOTS gateways and servers located in different domains must
perform mutual authentication (e.g., using certificates). A DOTS
server will only allow a DOTS gateway with a certificate for a
particular domain to request mitigation for that domain. In
reference to Figure 30, the DOTS server only allows the DOTS gateway
to request mitigation for 'example.com' domain and not for other
domains.
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9. IANA Considerations
9.1. DOTS Signal Channel UDP and TCP Port Number
IANA is requested to assign the port number TBD to the DOTS signal
channel protocol for both UDP and TCP from the "Service Name and
Transport Protocol Port Number Registry" available at
https://www.iana.org/assignments/service-names-port-numbers/service-
names-port-numbers.xhtml.
The assignment of port number 4646 is strongly suggested, as 4646 is
the ASCII decimal value for ".." (DOTS).
9.2. Well-Known 'dots' URI
This document requests IANA to register the 'dots' well-known URI
(Table 5) in the Well-Known URIs registry
(https://www.iana.org/assignments/well-known-uris/well-known-
uris.xhtml) as defined by [RFC8615]:
+----------+----------------+---------------------+-----------------+
| URI | Change | Specification | Related |
| suffix | controller | document(s) | information |
+----------+----------------+---------------------+-----------------+
| dots | IETF | [RFCXXXX] | None |
+----------+----------------+---------------------+-----------------+
Table 5: 'dots' well-known URI
9.3. Media Type Registration
This document requests IANA to register the "application/dots+cbor"
media type in the "Media Types" registry [IANA.MediaTypes] in the
manner described in [RFC6838], which can be used to indicate that the
content is a DOTS signal channel object:
o Type name: application
o Subtype name: dots+cbor
o Required parameters: N/A
o Optional parameters: N/A
o Encoding considerations: binary
o Security considerations: See the Security Considerations section
of [RFCXXXX]
o Interoperability considerations: N/A
o Published specification: [RFCXXXX]
o Applications that use this media type: DOTS agents sending DOTS
messages over CoAP over (D)TLS.
o Fragment identifier considerations: N/A
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o Additional information:
Magic number(s): N/A
File extension(s): N/A
Macintosh file type code(s): N/A
o Person & email address to contact for further information:
IESG, iesg@ietf.org
o Intended usage: COMMON
o Restrictions on usage: none
o Author: See Authors' Addresses section.
o Change controller: IESG
o Provisional registration? No
9.4. CoAP Content-Formats Registration
This document requests IANA to register the CoAP Content-Format ID
for the "application/dots+cbor" media type in the "CoAP Content-
Formats" registry [IANA.CoAP.Content-Formats] (0-255 range):
o Media Type: application/dots+cbor
o Encoding: -
o Id: TBD1
o Reference: [RFCXXXX]
9.5. CBOR Tag Registration
This section defines the DOTS CBOR tag as another means for
applications to declare that a CBOR data structure is a DOTS signal
channel object. Its use is optional and is intended for use in cases
in which this information would not otherwise be known. DOTS CBOR
tag is not required for DOTS signal channel protocol version
specified in this document. If present, the DOTS tag MUST prefix a
DOTS signal channel object.
This document requests IANA to register the DOTS signal channel CBOR
tag in the "CBOR Tags" registry [IANA.CBOR.Tags] using the 24-255
range:
o CBOR Tag: TBD2 (please assign the same value as the Content-
Format)
o Data Item: DDoS Open Threat Signaling (DOTS) signal channel object
o Semantics: DDoS Open Threat Signaling (DOTS) signal channel
object, as defined in [RFCXXXX]
o Description of Semantics: [RFCXXXX]
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9.6. DOTS Signal Channel Protocol Registry
The document requests IANA to create a new registry, entitled "DOTS
Signal Channel Registry". The following sections define sub-
registries.
9.6.1. DOTS Signal Channel CBOR Key Values Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel CBOR Key Values".
The structure of this sub-registry is provided in Section 9.6.1.1.
Section 9.6.1.2 provides how the registry is initially populated with
the values in Table 4.
9.6.1.1. Registration Template
Parameter name:
Parameter name as used in the DOTS signal channel.
CBOR Key Value:
Key value for the parameter. The key value MUST be an integer in
the 1-65535 range. The key values of the comprehension-required
range (0x0001 - 0x3FFF) and of the comprehension-optional range
(0x8000 - 0xBFFF) are assigned by IETF Review (Section 4.8 of
[RFC8126]). The key values of the comprehension-optional range
(0x4000 - 0x7FFF) are assigned by Specification Required
(Section 4.6 of [RFC8126]) and of the comprehension-optional range
(0xC000 - 0xFFFF) are reserved for Private Use (Section 4.1 of
[RFC8126]).
Registration requests for the 0x4000 - 0x7FFF range are evaluated
after a three-week review period on the dots-signal-reg-
review@ietf.org mailing list, on the advice of one or more
Designated Experts. However, to allow for the allocation of
values prior to publication, the Designated Experts may approve
registration once they are satisfied that such a specification
will be published. New registration requests should be sent in
the form of an email to the review mailing list; the request
should use an appropriate subject (e.g., "Request to register CBOR
Key Value for DOTS: example"). IANA will only accept new
registrations from the Designated Experts, and will check that
review was requested on the mailing list in accordance with these
procedures.
Within the review period, the Designated Experts will either
approve or deny the registration request, communicating this
decision to the review list and IANA. Denials should include an
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explanation and, if applicable, suggestions as to how to make the
request successful. Registration requests that are undetermined
for a period longer than 21 days can be brought to the IESG's
attention (using the iesg@ietf.org mailing list) for resolution.
Criteria that should be applied by the Designated Experts includes
determining whether the proposed registration duplicates existing
functionality, whether it is likely to be of general applicability
or whether it is useful only for a single use case, and whether
the registration description is clear. IANA must only accept
registry updates to the 0x4000 - 0x7FFF range from the Designated
Experts and should direct all requests for registration to the
review mailing list. It is suggested that multiple Designated
Experts be appointed. In cases where a registration decision
could be perceived as creating a conflict of interest for a
particular Expert, that Expert should defer to the judgment of the
other Experts.
CBOR Major Type:
CBOR Major type and optional tag for the parameter.
Change Controller:
For Standards Track RFCs, list the "IESG". For others, give the
name of the responsible party. Other details (e.g., email
address) may also be included.
Specification Document(s):
Reference to the document or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.
9.6.1.2. Initial Sub-Registry Content
+----------------------+-------+-------+------------+---------------+
| Parameter Name | CBOR | CBOR | Change | Specification |
| | Key | Major | Controller | Document(s) |
| | Value | Type | | |
+----------------------+-------+-------+------------+---------------+
| ietf-dots-signal-chan| 1 | 5 | IESG | [RFCXXXX] |
| nel:mitigation-scope | | | | |
| scope | 2 | 4 | IESG | [RFCXXXX] |
| cdid | 3 | 3 | IESG | [RFCXXXX] |
| cuid | 4 | 3 | IESG | [RFCXXXX] |
| mid | 5 | 0 | IESG | [RFCXXXX] |
| target-prefix | 6 | 4 | IESG | [RFCXXXX] |
| target-port-range | 7 | 4 | IESG | [RFCXXXX] |
| lower-port | 8 | 0 | IESG | [RFCXXXX] |
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| upper-port | 9 | 0 | IESG | [RFCXXXX] |
| target-protocol | 10 | 4 | IESG | [RFCXXXX] |
| target-fqdn | 11 | 4 | IESG | [RFCXXXX] |
| target-uri | 12 | 4 | IESG | [RFCXXXX] |
| alias-name | 13 | 4 | IESG | [RFCXXXX] |
| lifetime | 14 | 0/1 | IESG | [RFCXXXX] |
| mitigation-start | 15 | 0 | IESG | [RFCXXXX] |
| status | 16 | 0 | IESG | [RFCXXXX] |
| conflict-information | 17 | 5 | IESG | [RFCXXXX] |
| conflict-status | 18 | 0 | IESG | [RFCXXXX] |
| conflict-cause | 19 | 0 | IESG | [RFCXXXX] |
| retry-timer | 20 | 0 | IESG | [RFCXXXX] |
| conflict-scope | 21 | 5 | IESG | [RFCXXXX] |
| acl-list | 22 | 4 | IESG | [RFCXXXX] |
| acl-name | 23 | 3 | IESG | [RFCXXXX] |
| acl-type | 24 | 3 | IESG | [RFCXXXX] |
| bytes-dropped | 25 | 0 | IESG | [RFCXXXX] |
| bps-dropped | 26 | 0 | IESG | [RFCXXXX] |
| pkts-dropped | 27 | 0 | IESG | [RFCXXXX] |
| pps-dropped | 28 | 0 | IESG | [RFCXXXX] |
| attack-status | 29 | 0 | IESG | [RFCXXXX] |
| ietf-dots-signal- | 30 | 5 | IESG | [RFCXXXX] |
| channel:signal-config| | | | |
| sid | 31 | 0 | IESG | [RFCXXXX] |
| mitigating-config | 32 | 5 | IESG | [RFCXXXX] |
| heartbeat-interval | 33 | 5 | IESG | [RFCXXXX] |
| min-value | 34 | 0 | IESG | [RFCXXXX] |
| max-value | 35 | 0 | IESG | [RFCXXXX] |
| current-value | 36 | 0 | IESG | [RFCXXXX] |
| missing-hb-allowed | 37 | 5 | IESG | [RFCXXXX] |
| max-retransmit | 38 | 5 | IESG | [RFCXXXX] |
| ack-timeout | 39 | 5 | IESG | [RFCXXXX] |
| ack-random-factor | 40 | 5 | IESG | [RFCXXXX] |
| min-value-decimal | 41 | 6tag4 | IESG | [RFCXXXX] |
| max-value-decimal | 42 | 6tag4 | IESG | [RFCXXXX] |
| current-value- | 43 | 6tag4 | IESG | [RFCXXXX] |
| decimal | | | | |
| idle-config | 44 | 5 | IESG | [RFCXXXX] |
| trigger-mitigation | 45 | 7 | IESG | [RFCXXXX] |
| ietf-dots-signal-chan| 46 | 5 | IESG | [RFCXXXX] |
| nel:redirected-signal| | | | |
| alt-server | 47 | 3 | IESG | [RFCXXXX] |
| alt-server-record | 48 | 4 | IESG | [RFCXXXX] |
| ietf-dots-signal-chan| 49 | 5 | IESG | [RFCXXXX] |
| nel:heartbeat | | | | |
| probing-rate | 50 | 5 | IESG | [RFCXXXX] |
| peer-hb-status | 51 | 7 | IESG | [RFCXXXX] |
+----------------------+-------+-------+------------+---------------+
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Table 6: Initial DOTS Signal Channel CBOR Key Values Registry
9.6.2. Status Codes Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel Status Codes". Codes in this registry are used
as valid values of 'status' parameter.
The registry is initially populated with the following values:
+-----+----------------------------------+--------------+-----------+
| Cod | Label | Description | Reference |
| e | | | |
+-----+----------------------------------+--------------+-----------+
| 1 | attack-mitigation-in-progress | Attack | [RFCXXXX] |
| | | mitigation | |
| | | setup is in | |
| | | progress | |
| | | (e.g., | |
| | | changing the | |
| | | network path | |
| | | to redirect | |
| | | the inbound | |
| | | traffic to a | |
| | | DOTS | |
| | | mitigator). | |
| 2 | attack-successfully-mitigated | Attack is | [RFCXXXX] |
| | | being | |
| | | successfully | |
| | | mitigated | |
| | | (e.g., | |
| | | traffic is | |
| | | redirected | |
| | | to a DDoS | |
| | | mitigator | |
| | | and attack | |
| | | traffic is | |
| | | dropped). | |
| 3 | attack-stopped | Attack has | [RFCXXXX] |
| | | stopped and | |
| | | the DOTS | |
| | | client can | |
| | | withdraw the | |
| | | mitigation | |
| | | request. | |
| 4 | attack-exceeded-capability | Attack has | [RFCXXXX] |
| | | exceeded the | |
| | | mitigation | |
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| | | provider | |
| | | capability. | |
| 5 | dots-client-withdrawn-mitigation | DOTS client | [RFCXXXX] |
| | | has | |
| | | withdrawn | |
| | | the | |
| | | mitigation | |
| | | request and | |
| | | the | |
| | | mitigation | |
| | | is active | |
| | | but | |
| | | terminating. | |
| 6 | attack-mitigation-terminated | Attack | [RFCXXXX] |
| | | mitigation | |
| | | is now | |
| | | terminated. | |
| 7 | attack-mitigation-withdrawn | Attack | [RFCXXXX] |
| | | mitigation | |
| | | is | |
| | | withdrawn. | |
| 8 | attack-mitigation-signal-loss | Attack | [RFCXXXX] |
| | | mitigation | |
| | | will be | |
| | | triggered | |
| | | for the | |
| | | mitigation | |
| | | request only | |
| | | when the | |
| | | DOTS signal | |
| | | channel | |
| | | session is | |
| | | lost. | |
+-----+----------------------------------+--------------+-----------+
New codes can be assigned via Standards Action [RFC8126].
9.6.3. Conflict Status Codes Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel Conflict Status Codes". Codes in this registry
are used as valid values of 'conflict-status' parameter.
The registry is initially populated with the following values:
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+------+-------------------------------+----------------+-----------+
| Code | Label | Description | Reference |
+------+-------------------------------+----------------+-----------+
| 1 | request-inactive-other-active | DOTS server | [RFCXXXX] |
| | | has detected | |
| | | conflicting | |
| | | mitigation | |
| | | requests from | |
| | | different DOTS | |
| | | clients. This | |
| | | mitigation | |
| | | request is | |
| | | currently | |
| | | inactive until | |
| | | the conflicts | |
| | | are resolved. | |
| | | Another | |
| | | mitigation | |
| | | request is | |
| | | active. | |
| 2 | request-active | DOTS server | [RFCXXXX] |
| | | has detected | |
| | | conflicting | |
| | | mitigation | |
| | | requests from | |
| | | different DOTS | |
| | | clients. This | |
| | | mitigation | |
| | | request is | |
| | | currently | |
| | | active. | |
| 3 | all-requests-inactive | DOTS server | [RFCXXXX] |
| | | has detected | |
| | | conflicting | |
| | | mitigation | |
| | | requests from | |
| | | different DOTS | |
| | | clients. All | |
| | | conflicting | |
| | | mitigation | |
| | | requests are | |
| | | inactive. | |
+------+-------------------------------+----------------+-----------+
New codes can be assigned via Standards Action [RFC8126].
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9.6.4. Conflict Cause Codes Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel Conflict Cause Codes". Codes in this registry
are used as valid values of 'conflict-cause' parameter.
The registry is initially populated with the following values:
+------+--------------------------+---------------------+-----------+
| Code | Label | Description | Reference |
+------+--------------------------+---------------------+-----------+
| 1 | overlapping-targets | Overlapping | [RFCXXXX] |
| | | targets. | |
| 2 | conflict-with-acceptlist | Conflicts with an | [RFCXXXX] |
| | | existing accept- | |
| | | list. This code is | |
| | | returned when the | |
| | | DDoS mitigation | |
| | | detects source | |
| | | addresses/prefixes | |
| | | in the accept- | |
| | | listed ACLs are | |
| | | attacking the | |
| | | target. | |
| 3 | cuid-collision | CUID Collision. | [RFCXXXX] |
| | | This code is | |
| | | returned when a | |
| | | DOTS client uses a | |
| | | 'cuid' that is | |
| | | already used by | |
| | | another DOTS | |
| | | client. | |
+------+--------------------------+---------------------+-----------+
New codes can be assigned via Standards Action [RFC8126].
9.6.5. Attack Status Codes Sub-Registry
The document requests IANA to create a new sub-registry, entitled
"DOTS Signal Channel Attack Status Codes". Codes in this registry
are used as valid values of 'attack-status' parameter.
The registry is initially populated with the following values:
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+------+-------------------------------+----------------+-----------+
| Code | Label | Description | Reference |
+------+-------------------------------+----------------+-----------+
| 1 | under-attack | The DOTS | [RFCXXXX] |
| | | client | |
| | | determines | |
| | | that it is | |
| | | still under | |
| | | attack. | |
| 2 | attack-successfully-mitigated | The DOTS | [RFCXXXX] |
| | | client | |
| | | determines | |
| | | that the | |
| | | attack is | |
| | | successfully | |
| | | mitigated. | |
+------+-------------------------------+----------------+-----------+
New codes can be assigned via Standards Action [RFC8126].
9.7. DOTS Signal Channel YANG Modules
This document requests IANA to register the following URIs in the
"ns" subregistry within the "IETF XML Registry" [RFC3688]:
URI: urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel
Registrant Contact: The IESG.
XML: N/A; the requested URI is an XML namespace.
URI: urn:ietf:params:xml:ns:yang:iana-dots-signal-channel
Registrant Contact: IANA.
XML: N/A; the requested URI is an XML namespace.
This document requests IANA to register the following YANG modules in
the "YANG Module Names" subregistry [RFC7950] within the "YANG
Parameters" registry.
Name: ietf-dots-signal-channel
Namespace: urn:ietf:params:xml:ns:yang:ietf-dots-signal-channel
Maintained by IANA: N
Prefix: signal
Reference: RFC XXXX
Name: iana-dots-signal-channel
Namespace: urn:ietf:params:xml:ns:yang:iana-dots-signal-channel
Maintained by IANA: Y
Prefix: iana-signal
Reference: RFC XXXX
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This document defines the initial version of the IANA-maintained
iana-dots-signal-channel YANG module. IANA is requested to add this
note:
Status, conflict status, conflict cause, and attack status values
must not be directly added to the iana-dots-signal-channel YANG
module. They must instead be respectively added to the "DOTS
Status Codes", "DOTS Conflict Status Codes", "DOTS Conflict Cause
Codes", and "DOTS Attack Status Codes" registries.
When a 'status', 'conflict-status', 'conflict-cause', or 'attack-
status' value is respectively added to the "DOTS Status Codes", "DOTS
Conflict Status Codes", "DOTS Conflict Cause Codes", or "DOTS Attack
Status Codes" registry, a new "enum" statement must be added to the
iana-dots-signal-channel YANG module. The following "enum"
statement, and substatements thereof, should be defined:
"enum": Replicates the label from the registry.
"value": Contains the IANA-assigned value corresponding to the
'status', 'conflict-status', 'conflict-cause', or
'attack-status'.
"description": Replicates the description from the registry.
"reference": Replicates the reference from the registry and adds
the title of the document.
When the iana-dots-signal-channel YANG module is updated, a new
"revision" statement must be added in front of the existing revision
statements.
IANA is requested to add this note to "DOTS Status Codes", "DOTS
Conflict Status Codes", "DOTS Conflict Cause Codes", and "DOTS Attack
Status Codes" registries:
When this registry is modified, the YANG module iana-dots-signal-
channel must be updated as defined in [RFCXXXX].
10. Security Considerations
High-level DOTS security considerations are documented in [RFC8612]
and [I-D.ietf-dots-architecture].
Authenticated encryption MUST be used for data confidentiality and
message integrity. The interaction between the DOTS agents requires
Datagram Transport Layer Security (DTLS) or Transport Layer Security
(TLS) with a cipher suite offering confidentiality protection, and
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the guidance given in [RFC7525] MUST be followed to avoid attacks on
(D)TLS. The (D)TLS protocol profile used for the DOTS signal channel
is specified in Section 7.
If TCP is used between DOTS agents, an attacker may be able to inject
RST packets, bogus application segments, etc., regardless of whether
TLS authentication is used. Because the application data is TLS
protected, this will not result in the application receiving bogus
data, but it will constitute a DoS on the connection. This attack
can be countered by using TCP-AO [RFC5925]. Although not widely
adopted, if TCP-AO is used, then any bogus packets injected by an
attacker will be rejected by the TCP-AO integrity check and therefore
will never reach the TLS layer.
An attack vector that can be achieved if the 'cuid' is guessable is a
misbehaving DOTS client from within the client's domain which uses
the 'cuid' of another DOTS client of the domain to delete or alter
active mitigations. For this attack vector to happen, the
misbehaving client needs to pass the security validation checks by
the DOTS server, and eventually the checks of a client-domain DOTS
gateway.
A similar attack can be achieved by a compromised DOTS client which
can sniff the TLS 1.2 handshake, use the client certificate to
identify the 'cuid' used by another DOTS client. This attack is not
possible if algorithms such as version 4 Universally Unique
IDentifiers (UUIDs) in Section 4.4 of [RFC4122] are used to generate
the 'cuid' because such UUIDs are not a deterministic function of the
client certificate. Likewise, this attack is not possible with TLS
1.3 because most of the TLS handshake is encrypted and the client
certificate is not visible to eavesdroppers.
A compromised DOTS client can collude with a DDoS attacker to send
mitigation request for a target resource, gets the mitigation
efficacy from the DOTS server, and conveys the mitigation efficacy to
the DDoS attacker to possibly change the DDoS attack strategy.
Obviously, signaling an attack by the compromised DOTS client to the
DOTS server will trigger attack mitigation. This attack can be
prevented by monitoring and auditing DOTS clients to detect
misbehavior and to deter misuse, and by only authorizing the DOTS
client to request mitigation for specific target resources (e.g., an
application server is authorized to request mitigation for its IP
addresses but a DDoS mitigator can request mitigation for any target
resource in the network). Furthermore, DOTS clients are typically
co-located on network security services (e.g., firewall) and a
compromised security service potentially can do a lot more damage to
the network.
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Rate-limiting DOTS requests, including those with new 'cuid' values,
from the same DOTS client defends against DoS attacks that would
result in varying the 'cuid' to exhaust DOTS server resources. Rate-
limit policies SHOULD be enforced on DOTS gateways (if deployed) and
DOTS servers.
In order to prevent leaking internal information outside a client-
domain, DOTS gateways located in the client-domain SHOULD NOT reveal
the identification information that pertains to internal DOTS clients
(e.g., source IP address, client's hostname) unless explicitly
configured to do so.
DOTS servers MUST verify that requesting DOTS clients are entitled to
trigger actions on a given IP prefix. That is, only actions on IP
resources that belong to the DOTS client' domain MUST be authorized
by a DOTS server. The exact mechanism for the DOTS servers to
validate that the target prefixes are within the scope of the DOTS
client domain is deployment-specific.
The presence of DOTS gateways may lead to infinite forwarding loops,
which is undesirable. To prevent and detect such loops, this
document uses the Hop-Limit Option.
When FQDNs are used as targets, the DOTS server MUST rely upon DNS
privacy enabling protocols (e.g., DNS over TLS [RFC7858] or DoH
[RFC8484]) to prevent eavesdroppers from possibly identifying the
target resources protected by the DDoS mitigation service, and means
to ensure the target FQDN resolution is authentic (e.g., DNSSEC
[RFC4034]).
CoAP-specific security considerations are discussed in Section 11 of
[RFC7252], while CBOR-related security considerations are discussed
in Section 8 of [RFC7049].
11. Contributors
The following individuals have contributed to this document:
o Jon Shallow, NCC Group, Email: jon.shallow@nccgroup.trust
o Mike Geller, Cisco Systems, Inc. 3250 Florida 33309 USA, Email:
mgeller@cisco.com
o Robert Moskowitz, HTT Consulting Oak Park, MI 42837 United States,
Email: rgm@htt-consult.com
o Dan Wing, Email: dwing-ietf@fuggles.com
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12. Acknowledgements
Thanks to Christian Jacquenet, Roland Dobbins, Roman Danyliw, Michael
Richardson, Ehud Doron, Kaname Nishizuka, Dave Dolson, Liang Xia,
Gilbert Clark, Xialiang Frank, Jim Schaad, Klaus Hartke, Nesredien
Suleiman, Stephen Farrell, and Yoshifumi Nishida for the discussion
and comments.
The authors would like to give special thanks to Kaname Nishizuka and
Jon Shallow for their efforts in implementing the protocol and
performing interop testing at IETF Hackathons.
Thanks to the core WG for the recommendations on Hop-Limit and
redirect signaling.
Special thanks to Benjamin Kaduk for the detailed AD review.
Thanks to Alexey Melnikov, Adam Roach, Suresh Krishnan, Mirja
Kuehlewind, and Alissa Cooper for the review.
Thanks to Carsten Bormann for his review of the DOTS heartbeat
mechanism.
13. References
13.1. Normative References
[I-D.ietf-core-hop-limit]
Boucadair, M., Reddy.K, T., and J. Shallow, "Constrained
Application Protocol (CoAP) Hop-Limit Option", draft-ietf-
core-hop-limit-07 (work in progress), October 2019.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
Communication Layers", STD 3, RFC 1122,
DOI 10.17487/RFC1122, October 1989,
<https://www.rfc-editor.org/info/rfc1122>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC4279] Eronen, P., Ed. and H. Tschofenig, Ed., "Pre-Shared Key
Ciphersuites for Transport Layer Security (TLS)",
RFC 4279, DOI 10.17487/RFC4279, December 2005,
<https://www.rfc-editor.org/info/rfc4279>.
[RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing
(CIDR): The Internet Address Assignment and Aggregation
Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August
2006, <https://www.rfc-editor.org/info/rfc4632>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extensions: Extension Definitions", RFC 6066,
DOI 10.17487/RFC6066, January 2011,
<https://www.rfc-editor.org/info/rfc6066>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <https://www.rfc-editor.org/info/rfc6125>.
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[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
RFC 6991, DOI 10.17487/RFC6991, July 2013,
<https://www.rfc-editor.org/info/rfc6991>.
[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object
Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
October 2013, <https://www.rfc-editor.org/info/rfc7049>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>.
[RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
Application Protocol (CoAP)", RFC 7252,
DOI 10.17487/RFC7252, June 2014,
<https://www.rfc-editor.org/info/rfc7252>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC7641] Hartke, K., "Observing Resources in the Constrained
Application Protocol (CoAP)", RFC 7641,
DOI 10.17487/RFC7641, September 2015,
<https://www.rfc-editor.org/info/rfc7641>.
[RFC7918] Langley, A., Modadugu, N., and B. Moeller, "Transport
Layer Security (TLS) False Start", RFC 7918,
DOI 10.17487/RFC7918, August 2016,
<https://www.rfc-editor.org/info/rfc7918>.
[RFC7924] Santesson, S. and H. Tschofenig, "Transport Layer Security
(TLS) Cached Information Extension", RFC 7924,
DOI 10.17487/RFC7924, July 2016,
<https://www.rfc-editor.org/info/rfc7924>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
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[RFC7959] Bormann, C. and Z. Shelby, Ed., "Block-Wise Transfers in
the Constrained Application Protocol (CoAP)", RFC 7959,
DOI 10.17487/RFC7959, August 2016,
<https://www.rfc-editor.org/info/rfc7959>.
[RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage
Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085,
March 2017, <https://www.rfc-editor.org/info/rfc8085>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
Better Connectivity Using Concurrency", RFC 8305,
DOI 10.17487/RFC8305, December 2017,
<https://www.rfc-editor.org/info/rfc8305>.
[RFC8323] Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
Silverajan, B., and B. Raymor, Ed., "CoAP (Constrained
Application Protocol) over TCP, TLS, and WebSockets",
RFC 8323, DOI 10.17487/RFC8323, February 2018,
<https://www.rfc-editor.org/info/rfc8323>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8615] Nottingham, M., "Well-Known Uniform Resource Identifiers
(URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
<https://www.rfc-editor.org/info/rfc8615>.
13.2. Informative References
[I-D.boucadair-dots-earlydata]
Boucadair, M. and R. K, "Using Early Data in DOTS", draft-
boucadair-dots-earlydata-00 (work in progress), January
2019.
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[I-D.ietf-core-comi]
Veillette, M., Stok, P., Pelov, A., Bierman, A., and I.
Petrov, "CoAP Management Interface", draft-ietf-core-
comi-08 (work in progress), September 2019.
[I-D.ietf-core-yang-cbor]
Veillette, M., Petrov, I., and A. Pelov, "CBOR Encoding of
Data Modeled with YANG", draft-ietf-core-yang-cbor-11
(work in progress), September 2019.
[I-D.ietf-dots-architecture]
Mortensen, A., Reddy.K, T., Andreasen, F., Teague, N., and
R. Compton, "Distributed-Denial-of-Service Open Threat
Signaling (DOTS) Architecture", draft-ietf-dots-
architecture-14 (work in progress), May 2019.
[I-D.ietf-dots-data-channel]
Boucadair, M. and T. Reddy.K, "Distributed Denial-of-
Service Open Threat Signaling (DOTS) Data Channel
Specification", draft-ietf-dots-data-channel-31 (work in
progress), July 2019.
[I-D.ietf-dots-multihoming]
Boucadair, M., Reddy.K, T., and W. Pan, "Multi-homing
Deployment Considerations for Distributed-Denial-of-
Service Open Threat Signaling (DOTS)", draft-ietf-dots-
multihoming-02 (work in progress), July 2019.
[I-D.ietf-dots-server-discovery]
Boucadair, M. and T. Reddy.K, "Distributed-Denial-of-
Service Open Threat Signaling (DOTS) Agent Discovery",
draft-ietf-dots-server-discovery-06 (work in progress),
November 2019.
[I-D.ietf-dots-use-cases]
Dobbins, R., Migault, D., Moskowitz, R., Teague, N., Xia,
L., and K. Nishizuka, "Use cases for DDoS Open Threat
Signaling", draft-ietf-dots-use-cases-20 (work in
progress), September 2019.
[I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-34 (work in progress),
November 2019.
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[IANA.CBOR.Tags]
IANA, "Concise Binary Object Representation (CBOR) Tags",
<http://www.iana.org/assignments/cbor-tags/cbor-
tags.xhtml>.
[IANA.CoAP.Content-Formats]
IANA, "CoAP Content-Formats",
<http://www.iana.org/assignments/core-parameters/core-
parameters.xhtml#content-formats>.
[IANA.MediaTypes]
IANA, "Media Types",
<http://www.iana.org/assignments/media-types>.
[proto_numbers]
"IANA, "Protocol Numbers"", 2011,
<http://www.iana.org/assignments/protocol-numbers>.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
DOI 10.17487/RFC3022, January 2001,
<https://www.rfc-editor.org/info/rfc3022>.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, DOI 10.17487/RFC4034, March 2005,
<https://www.rfc-editor.org/info/rfc4034>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
[RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram
Congestion Control Protocol (DCCP)", RFC 4340,
DOI 10.17487/RFC4340, March 2006,
<https://www.rfc-editor.org/info/rfc4340>.
[RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet
Denial-of-Service Considerations", RFC 4732,
DOI 10.17487/RFC4732, December 2006,
<https://www.rfc-editor.org/info/rfc4732>.
[RFC4787] Audet, F., Ed. and C. Jennings, "Network Address
Translation (NAT) Behavioral Requirements for Unicast
UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January
2007, <https://www.rfc-editor.org/info/rfc4787>.
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[RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007,
<https://www.rfc-editor.org/info/rfc4960>.
[RFC4987] Eddy, W., "TCP SYN Flooding Attacks and Common
Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007,
<https://www.rfc-editor.org/info/rfc4987>.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
DOI 10.17487/RFC5389, October 2008,
<https://www.rfc-editor.org/info/rfc5389>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
DOI 10.17487/RFC6052, October 2010,
<https://www.rfc-editor.org/info/rfc6052>.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, DOI 10.17487/RFC6146,
April 2011, <https://www.rfc-editor.org/info/rfc6146>.
[RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms
(SHA and SHA-based HMAC and HKDF)", RFC 6234,
DOI 10.17487/RFC6234, May 2011,
<https://www.rfc-editor.org/info/rfc6234>.
[RFC6296] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Prefix
Translation", RFC 6296, DOI 10.17487/RFC6296, June 2011,
<https://www.rfc-editor.org/info/rfc6296>.
[RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown,
"Default Address Selection for Internet Protocol Version 6
(IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012,
<https://www.rfc-editor.org/info/rfc6724>.
[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/info/rfc6838>.
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[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<https://www.rfc-editor.org/info/rfc6887>.
[RFC6888] Perreault, S., Ed., Yamagata, I., Miyakawa, S., Nakagawa,
A., and H. Ashida, "Common Requirements for Carrier-Grade
NATs (CGNs)", BCP 127, RFC 6888, DOI 10.17487/RFC6888,
April 2013, <https://www.rfc-editor.org/info/rfc6888>.
[RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC7030, October 2013,
<https://www.rfc-editor.org/info/rfc7030>.
[RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP
Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014,
<https://www.rfc-editor.org/info/rfc7413>.
[RFC7452] Tschofenig, H., Arkko, J., Thaler, D., and D. McPherson,
"Architectural Considerations in Smart Object Networking",
RFC 7452, DOI 10.17487/RFC7452, March 2015,
<https://www.rfc-editor.org/info/rfc7452>.
[RFC7589] Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the
NETCONF Protocol over Transport Layer Security (TLS) with
Mutual X.509 Authentication", RFC 7589,
DOI 10.17487/RFC7589, June 2015,
<https://www.rfc-editor.org/info/rfc7589>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
RFC 7951, DOI 10.17487/RFC7951, August 2016,
<https://www.rfc-editor.org/info/rfc7951>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
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[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
[RFC8612] Mortensen, A., Reddy, T., and R. Moskowitz, "DDoS Open
Threat Signaling (DOTS) Requirements", RFC 8612,
DOI 10.17487/RFC8612, May 2019,
<https://www.rfc-editor.org/info/rfc8612>.
Appendix A. CUID Generation
The document recommends the use of SPKI to generate the 'cuid'. This
design choice is motivated by the following reasons:
o SPKI is globally unique.
o It is deterministic.
o It allows to avoid extra cycles that may be induced by 'cuid'
collision.
o DOTS clients do not need to store the 'cuid' in a persistent
storage.
o It allows to detect compromised DOTS clients that do not adhere to
the 'cuid' generation algorithm.
Authors' Addresses
Tirumaleswar Reddy (editor)
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
Mohamed Boucadair (editor)
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
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Prashanth Patil
Cisco Systems, Inc.
Email: praspati@cisco.com
Andrew Mortensen
Arbor Networks, Inc.
2727 S. State St
Ann Arbor, MI 48104
United States
Email: andrew@moretension.com
Nik Teague
Iron Mountain Data Centers
United Kingdom
Email: nteague@ironmountain.co.uk
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