Internet DRAFT - draft-ietf-lisp-map-server-reliable-transport
draft-ietf-lisp-map-server-reliable-transport
Network Working Group B. Pitta
Internet-Draft M. Portoles
Intended status: Experimental Cisco Systems
Expires: 22 April 2024 D. Lewis
ICANN
I. Kouvelas
Arista Networks Inc.
C. Cassar
Rivian Automotive
20 October 2023
LISP Map Server Reliable Transport
draft-ietf-lisp-map-server-reliable-transport-03
Abstract
The communication between LISP ETRs and Map-Servers is based on
unreliable UDP message exchange coupled with periodic message
transmission in order to maintain soft state. The drawback of
periodic messaging is the constant load imposed on both the ETR and
the Map-Server. New use cases for LISP have increased the amount of
state that needs to be communicated with requirements that are not
satisfied by the current mechanism. This document introduces the use
of a reliable transport for ETR to Map-Server communication in order
to eliminate the periodic messaging overhead, while providing
reliability, flow-control and endpoint liveness detection.
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 22 April 2024.
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Copyright Notice
Copyright (c) 2023 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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Notation . . . . . . . . . . . . . . . . . . . . 4
3. Message Format . . . . . . . . . . . . . . . . . . . . . . . 4
4. Session Establishment . . . . . . . . . . . . . . . . . . . . 5
4.1. Signaling to Trigger Session Establishment . . . . . . . 6
4.2. Transport Protocol and Port Usage . . . . . . . . . . . . 7
5. Error Notifications . . . . . . . . . . . . . . . . . . . . . 7
6. EID Prefix Registration . . . . . . . . . . . . . . . . . . . 8
6.1. Reliable Mapping Registration Messages . . . . . . . . . 9
6.1.1. Registration Message . . . . . . . . . . . . . . . . 9
6.1.2. Registration Acknowledgement Message . . . . . . . . 10
6.1.3. Registration Rejection Message . . . . . . . . . . . 11
6.1.4. Registration Refresh Message . . . . . . . . . . . . 12
6.1.5. Mapping Notification Message . . . . . . . . . . . . 13
6.2. ETR Behavior . . . . . . . . . . . . . . . . . . . . . . 14
6.3. Map-Server Behavior . . . . . . . . . . . . . . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
8.1. LISP Reliable Transport Message Types . . . . . . . . . . 19
8.2. Transport Protocol Port Numbers . . . . . . . . . . . . . 19
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 20
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
11. Normative References . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
The communication channel between LISP ETRs and Map-Servers is based
on unreliable UDP message exchange [RFC9301]. Where required,
reliability is pursued through periodic retransmissions that maintain
soft state on the peer. Map-Register messages are retransmitted
every minute by an ETR and the Map-Server times out its state if the
state is not refreshed for three successive periods. When
registering multiple EID-Prefixes, the ETR includes multiple mapping
records in the Map-Register message. Packet size limitations provide
an upper bound to the number of mapping records that can be placed in
each Map-Register message. When the ETR has more EID-Prefixes to
register than can be packed in a single Map-Register message, the
mapping records for the EID-Prefixes are split across multiple Map-
Register messages.
The drawback of the periodic registration is the constant load that
it introduces on both the ETR and the Map-Server. The ETR uses
resources to periodically build and transmit the Map-Register
messages, and to process the resulting Map-Notify messages issued by
the Map-Server. The Map-Server uses resources to process the
received Map-Register messages, update the corresponding registration
state, and build and transmit the matching Map-Notify messages. When
the number of EID-Prefixes to be registered by an ETR is small, the
resulting load imposed by periodic registrations may not be
significant. The ETR will only transmit a single Map-Register
message each period that contains a small number of mapping records.
In some LISP deployments, a large set of EID-Prefixes must be
registered by each ETR (e.g. mobility, database redistribution). Use
cases with a large set of EID-Prefixes behind an ETR will result in a
much higher load. An example is LISP mobility deployments where EID-
Prefixes are limited to host entries. ETRs may have thousands of
hosts to register resulting in hundreds of Map-Register and Map-
Notify messages per registration period.
A transport is required for the ETR to Map-Server communication that
provides reliability, flow-control and endpoint liveness
notifications. This document describes the use of TCP as a LISP
reliable transport. The initial application for the LISP reliable
transport session is the support of scalable EID prefix registration.
The reliable session mechanism is defined to be extensible so that it
can support additional LISP communication requirements as they arise
using a single reliable transport session between an ETR and a Map-
Server. The use of the reliable transport session for EID prefix
registration is an alternative and does not replace the existing UDP
based mechanism.
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2. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. Message Format
A single LISP reliable transport session may carry information for
multiple LISP applications. One such application is the registration
of EID to RLOC mappings that operates over a session between an ETR
and a Map-Server. Communication over a session is based on the
exchange of messages. This document defines a base set of messages
to support session establishment and management. It also defines the
messages for the EID to RLOC mapping registration application.
To support protocol extensibility when new applications, or
extensions to existing applications are introduced, the messages are
based on a TLV format.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message End Marker |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Reliable transport message format
* Type: 16 bit type field identifying the message type.
* Length: 16 bit field that provides the total size of the message
in octets including the length, type and end marker fields. The
length allows the receiver to locate the next message in the TCP
stream. The minimum value of the length field is 8.
* ID: A 32-bit value that identifies the message. May be used by
the receiver to identify the message in replies or notification
messages.
* Data: Type specific message contents.
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* End Marker: A 32-bit message end marker that must be set to
0x9FACADE9. The End Marker is used by the receiver to validate
that it has correctly parsed or skipped a message and provides a
method to detect formatting errors. Note that message data may
also contain this marker, and that the marker itself is not
sufficient for parsing the message.
The base message format does not indicate how the peer should deal
with the message in cases where the message type is not supported/
understood. This is best dealt with by the application. For
example, in case an error notification is returned, or an expected
acknowledgement message is not received, the application might choose
various courses of action; from simply logging that the feature is
not supported, all the way to tearing the relationship with the peer
down for the feature, or for all LISP features.
4. Session Establishment
To ensure backwards compatibility, the Map-Server and ETR MUST
communicate via unreliable UDP messages until a reliable session
between the two can be successfully established.
The ETR indicates its intent to use a reliable transport setting the
Reliable Transport bit in the UDP Map-Register message. As an
acknowledgement, when the MS is ready to accept the establishment of
a reliable transport session it also sets the Reliable Transport bit
in the Map-Notify message. The Reliable Transport bit is specified
below in Section 4.1.
The Map-Server authenticates the ETR with the authentication data
contained in the first UDP Map-Register message it receives from the
ETR. Once the ETR is authenticated, the Map-Server performs a
passive open by listening on TCP port 4342, and does not qualify the
remote port. As a security measure, the Map-Server does not create
any connection unless a UDP authentication, with the r bit set,
completes first. After that, the Map-Server accepts connections only
from those ETRs that have been authenticated via UDP Map-Register
messages. Note that the use of TCP here is for documentation
purposes, Section 4.2 lists the alternatives that can be used to
sustain the reliable transport session.
The ETR assumes the active role of the TCP session establishment by
connecting to the Map-Server once it has received a UDP Map-Notify
message with the Reliable Transport bit set. ETR MUST assume the
client role and it is always the one attempting the connection.
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When a TCP session goes down, UDP authentication must take place
before a new TCP session is established. The Map-Server will not
accept a connection from the ETR until a UDP Map-Register with the
Reliable Transport bit set has been received. Similarly, the ETR
will not attempt to establish a session with the Map-Server until an
UDP map-notify message has been received with the Reliable Transport
bit set.
A single reliable transport session is established between the Map-
Server and the ETR to cover all communication needs. For example, an
ETR that has EID prefix registrations for multiple EID instances and
EID address families will only establish a single session with the
Map-Server.
4.1. Signaling to Trigger Session Establishment
Following the procedures described in this document, the Map-Register
and Map-Notify headers are extended with a new flag, the Reliable
Transport bit, that is used to advertise intent to establish a
reliable transport session (ETR), as well as the capability to accept
reliable transport sessions (MS).
The Map-Register header, as defined in [RFC9301] is extended with an
additional field, the Reliable Transport bit.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=3 |P|S|I| Reserved |r|E|T|a|R|M| Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r: This is the Reliable Transport bit in the Map-Register header.
It should be set to 1 when the ETR that sends a registration
intends to establish a reliable transport session with the MS that
the registration is being sent to.
The Map-Notify header, as defined in [RFC9301], is extended with an
additional field, the Reliable Transport bit.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Type=4| Reserved |r| Record Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r: This is the Reliable Transport bit in the Map-Notify header. It
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should be set to 1 when the MS has validated an initial UDP
registration and acknowledges the possibility to use a reliable
transport session with the ETR.
4.2. Transport Protocol and Port Usage
This document defines TCP as transport protocol that can be used to
sustain a reliable transport between ETRs and the MS:
TCP [RFC0793]: This is the reference protocol used as a base for
documentation of this specification. The port 4342 is used for this
purpose (see Section 8.2). TCP sessions are long-lived and
maintained unless one of the endpoints closes or resets the session,
or the communication times out and needs to be restarted.
5. Error Notifications
The error notification message is used to communicate base reliable
transport session communication errors. LISP applications making use
of the reliable transport session and having to communicate
application specific errors must define their own messages to do so.
An error notification is issued when the receiver of a message does
not recognize the message type or cannot parse the message contents.
The notification includes the offending message type and ID and as
much of the offending message data as the notification sender wishes
to.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 16 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Code | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offending Message Type | Offending Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offending Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Offending Message Data ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message End Marker |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Error Notification message format
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* Error Code: An 8 bit field identifying the type of error that
occurred. Defined errors are:
- Unrecognized message type.
- Message format error.
* Reserved: Set to zero by the sender and ignored by the receiver.
* Offending Message Type: 16 bit type field identifying the message
type of the offending message that triggered this error
notification. This is copied from the Type field of the offending
message.
* Offending Message Length: 16 bit field that provides the total
size of the offending message in octets. This is copied from the
Length field of the offending message.
* Offending Message ID: A 32-bit field that is set to the Message ID
field of the offending message.
* Offending Message Data: The Data from the offending message that
triggered this error notification. The sender of the notification
may include as much of the original data as is deemed necessary.
The length of the Offending Message Data field is not provided by
the Offending Message Length field and is determined by
subtracting the size of the other fields in the message from the
Length field. It is valid to not include any of the offending
message data when sending an error notification.
* End Marker: A 32-bit message end marker that must be set to
0x9FACADE9. The End Marker is used by the receiver to validate
that it has correctly parsed or skipped a message and provides a
method to detect formatting errors. Note that message data may
also contain this marker, and that the marker itself is not
sufficient for parsing the message.
An error notification cannot be the offending message in another
error notification and MUST NOT trigger such a message.
6. EID Prefix Registration
EID prefix registration uses the reliable transport session between
an ETR and a Map-Server to communicate the ETR local EID database EID
to RLOC mappings to the Map-Server. In contrast to the UDP based
periodic registration, mapping information over the reliable
transport session is only sent when there is new information
available for the Map-Server. The Map-Server does not maintain a
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timer to expire registrations communicated over the reliable
transport session. Instead an explicit de-registration (a
registration carrying a zero TTL) is needed to delete the state
maintained by the Map-Server.
The key used to identify registration mapping records in the ETR to
Map-Server communication is the EID prefix. The prefix may be
specified using an LCAF encoding that includes an EID instance ID.
When the reliable transport session goes down, registration mappings
learned by the Map-Server are treated as periodic UDP registrations
and a timer is used to expire them after 3 minutes. During this
period UDP based registrations or the re-establishment of the
reliable transport session and subsequent communication of a new
mapping can update the EID prefix mapping state.
6.1. Reliable Mapping Registration Messages
This section defines the LISP reliable transport session messages
used to communicate local EID database registrations between the ETR
and the Map-Server.
6.1.1. Registration Message
The reliable transport registration message is used to communicate
EID to RLOC mapping registrations from the ETR to the Map-Server. To
increase code reuse, the "Message Data" field uses the same format as
the UDP Map-Registers but without the IP and UDP headers. A reliable
registration message MUST contain a single mapping-record. The Map-
Server MUST discard any reliable registration message that contains
more than one mapping record.
The reliable transport session is authenticated by means of the
session establishment procedure. Thus, although the Map-Register
MUST carry the authentication data, it is up to the Map-Server to
determine if each individual reliable registration message should be
authenticated.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 17 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Map-Register message ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Map-Register message |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message End Marker |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Registration message format
6.1.2. Registration Acknowledgement Message
The Acknowledgement message is sent from the Map-Server to the ETR to
confirm successful registration of an EID prefix previously
communicated by a reliable transport session Registration message.
The Registration Acknowledgement message does not carry a mapping
record (the Map-Servers view of the mapping). This is accomplished
by the LISP reliable transport Map Notification message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 18 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix-Length | EID-Prefix-AFI | EID-Prefix ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message End Marker |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Registration Acknowledgement message format
* Prefix-Length: Mask length for the EID prefix.
* EID-Prefix AFI: Address family identifier for the EID prefix in
the following field.
* EID-Prefix: The EID prefix from the received Registration.
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6.1.3. Registration Rejection Message
The Registration Rejection Message is sent by the Map-Server to the
ETR to indicate that the registration of a specific EID prefix is
being rejected or withdrawn. A rejection refers to a recently-sent
registration that is being immediately rejected. A withdrawal refers
to a previously accepted registration that is no longer acceptable,
perhaps due to a configuration change in the Map-Server. The ETR
must keep track of rejected EID prefixes and be prepared to re-
register their mappings when requested through a registration refresh
message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 19 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reason | Reserved | Prefix-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID-Prefix-AFI | EID-Prefix ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message End Marker |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Registration Rejection message format
* Reason: Code identifying the reason for which the Map-Server
rejected or withdrew the registration.
- 1 - Not a valid site EID prefix.
- 2 - Authentication failure.
- 3 - Locator set not allowed.
- 4 - Used to cover reason that's not defined.
* Reserved: This field is reserved for future use. Set to zero by
the sender and ignored by the receiver.
* Prefix-Length: Mask length for the EID prefix.
* EID-Prefix-AFI: Address family identifier for the EID prefix in
the following field.
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* EID-Prefix: The EID prefix being rejected or withdrawn.
6.1.4. Registration Refresh Message
Sent by the Map-Server to the ETR to request the (re-)transmission of
EID prefix database mapping Registration messages.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 20 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Scope |R| Reserved | Prefix-Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EID-Prefix-AFI | EID-Prefix ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message End Marker |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Registration Refresh message format
* Scope: Determines the set of registrations being refreshed.
- 0 - All prefixes under all address families under all EID
instances are being refreshed. When using this scope the
Prefix-Length, EID-Prefix-AFI, and EID-Prefix fields MUST be
omitted. That is, the Message End Marker follows immediately
after the Reserved field. The total length of the message MUST
be 15 bytes.
- 1 - All prefixes under all address families under a single EID
instance are being refreshed. The Prefix-Length MUST be set to
zero, EID-Prefix-AFI MUST be set to LCAF type, the EID-Prefix
encodes the LCAF Instance ID, the LCAF address AFI MUST be set
to UNSPECIFIED. The total length of the message MUST be 30
bytes.
- 2 - All prefixes under a single address family under a single
EID instance are being refreshed. The Prefix-Length MUST be
set to zero, the EID-Prefix-AFI MUST be set to LCAF type and
the EID-Prefix MUST encode the Instance ID. The LCAF address
AFI MUST specify the address family to refresh, the actual
address SHOULD be set to zero.
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- 3 - All prefixes covered by a specific EID prefix in a single
EID instance is being refreshed. The Prefix-Length, EID-
Prefix-AFI and EID prefix MUST be encoded accordingly.
- 4 - A specific EID prefix in a single EID instance is being
refreshed. The Prefix-Length, EID-Prefix-AFI and EID prefix
MUST be encoded accordingly.
The Map-Server has the flexibility to control the granularity of
the refresh by issuing refresh with different scopes. It can send
a single refresh with a coarse scope or send individual refreshes
with narrower scope. The ETR MUST be able to process all scopes
to ensure the Map-Server registration states are synchronized with
the ETR.
* R: Request from the ETR to only refresh registrations that have
been previously rejected by the Map-Server. If the R bit is set
then the scope cannot have a value of 3 and the EID-Prefix and
Prefix-Length fields must be omitted.
* Reserved: This field is reserved for future use. Set to zero by
the sender and ignored by the receiver.
* Prefix-Length: Mask length for the EID prefix. Refer to scope for
more details.
* EID-Prefix-AFI: Address family identifier for the EID prefix in
the following field. Refer to scope for more details.
* EID-Prefix: The EID prefix being refreshed. Refer to scope for
more details.
6.1.5. Mapping Notification Message
Mapping Notification messages communicate the Map-Server view of the
mapping for an EID prefix and no longer serve as a registration
acknowledgement. Mapping Notifications do not need message level
authentication as they are received over a reliable transport session
to a known Map-Server. Note that reliable transport Mapping
Notification messages do not reuse the UDP Map-Notify message format.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 21 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| xTR-ID 128 bits ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| xTR-ID 128 bits ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| xTR-ID 128 bits ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| xTR-ID 128 bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| site-ID 64 bits ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| site-ID 64 bits |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mapping Record ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Mapping Record |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message End Marker |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Mapping Notification message format
* xTR-ID: xTR-ID taken from the last valid registration the Map-
Server received for the EID-prefix conveyed in the mapping record.
* site-ID: site-ID taken from the last valid registration the Map-
Server received for the EID-prefix conveyed in the mapping record.
* Mapping Record: Mapping record of the EID-prefix the Map-Server is
conveying to the ETR.
6.2. ETR Behavior
The ETR operates the following per EID prefix, per MS state machine
that defines the reliable transport EID prefix registration behavior.
There are five states:
* No state: The local EID database prefix does not exist.
* Periodic: The local EID database prefix is being periodically
registered through UDP Map-Register messages as specified in [].
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* Stable: From the ETR's perspective, no registrations are due to be
sent to the peer. The session to the peer is up, and the peer has
either acknowledged the registration, or is expected to request a
refresh in the future.
* AckWait: A Registration message for the prefix has been
transmitted to the Map-Server and the ETR is waiting for either a
Registration Acknowledge or Registration Rejected reply from the
Map-Server.
* Reject: The reliable transport registration for the local EID
database prefix was rejected by the Map-Server. From the ETR's
perspective, no registration is due to the peer AND the peer is
known to have rejected the registration.
The following events drive the state transitions:
* DB creation: The local EID database entry for the EID prefix is
created.
* DB deletion: The local EID database entry for the EID prefix is
deleted.
* DB change: The mapping contents or authentication information for
the local EID database entry changes.
* Session up: The reliable transport session to the Map-Server is
established.
* Session down: The reliable transport session the Map-Server goes
down.
* Recv Refresh: A Registration refresh message is received from the
Map-Server.
* Recv ACK: A Registration Acknowledge message is received from the
Map-Server.
* Recv Rejected: A Registration Rejected message is received from
the Map-Server.
* Periodic timer: The timer that drives generation of periodic UDP
Map-Register messages fires.
The state machine is:
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+--------------------+--------------------------------------+
| | Prev State |
| Event +-------------------+------------------+
| | No state | Periodic |
+--------------------+-------------------+------------------+
| DB creation | -> Periodic | N/A |
| [session down] | A1 | |
+--------------------+-------------------+------------------+
| DB creation | -> AckWait | N/A |
| [session up] | A2 | |
+--------------------+-------------------+------------------+
| DB deletion | N/A | -> No state |
| | | A3 |
+--------------------+-------------------+------------------+
| DB change | N/A | - |
| | | A1 |
+--------------------+-------------------+------------------+
| Session up | - | -> Stable |
| | | A4 |
+--------------------+-------------------+------------------+
| Session down | - | N/A |
| | | |
+--------------------+-------------------+------------------+
| Recv Refresh | - | N/A |
| | | |
+--------------------+-------------------+------------------+
| Recv Refresh | - | N/A |
| [rejected] | | |
+--------------------+-------------------+------------------+
| Recv ACK | - | N/A |
| | | |
+--------------------+-------------------+------------------+
| Recv Rejection | - | N/A |
| | | |
+--------------------+-------------------+------------------+
| Timer | N/A | - |
| | | A5 |
+--------------------+-------------------+------------------+
xTR per EID prefix per MS state machine
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+-----------------+-----------------------------------------------+
| | Prev State |
| Event +---------------+---------------+---------------+
| | Stable | AckWait | Rejected |
+-----------------+---------------+---------------+---------------+
| DB creation | N/A | N/A | N/A |
| | | | |
+-----------------+---------------+---------------+---------------+
| DB deletion | -> No state | -> No state | -> No state |
| | A6 | A6 | |
+-----------------+---------------+---------------+---------------+
| DB change | -> AckWait | - | -> AckWait |
| | A2 | A2 | A2 |
+-----------------+---------------+---------------+---------------+
| Session up | N/A | N/A | N/A |
| | | | |
+-----------------+---------------+---------------+---------------+
| Session down | -> Periodic | -> Periodic | -> Periodic |
| | A7 | A7 | A7 |
+-----------------+---------------+---------------+---------------+
| Recv Refresh | -> AckWait | - | -> AckWait |
| | A2 | A2 | A2 |
+-----------------+---------------+---------------+---------------+
| Recv Refresh | - | - | -> AckWait |
| [rejected] | | A2 | A2 |
+-----------------+---------------+---------------+---------------+
| Recv ACK | - | -> Stable | -> AckWait |
| | | | A2 |
+-----------------+---------------+---------------+---------------+
| Recv Rejection | -> Rejected | -> Rejected | - |
| | | | |
+-----------------+---------------+---------------+---------------+
| Timer | N/A | N/A | N/A |
| | | | |
+-----------------+---------------+---------------+---------------+
xTR per EID prefix per MS state machine
Action descriptions:
* A1: Start periodic registration timer with zero delay.
* A2: Send Registration over reliable transport session.
* A3: Send UDP registration with zero TTL.
* A4: Stop periodic registration timer.
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* A7: Send UDP registration and start periodic registration timer
with registration period.
* A6: Send Registration with TTL zero over reliable transport
session.
* A7: Start periodic registration timer with registration period.
All timer start actions must be jittered.
When the reliable transport session is established the ETR moves the
state machine into the Stable state without first registering the EID
prefix over the reliable transport session. The Map-Server will send
a refresh message with a scope of 0 that will trigger the
registration message to be sent. Because other applications may be
using the reliable session, the refresh message signals the ETR that
the Map-Server supports reliable map registration messages. This
model will also allow future optimizations where the Map-Server may
retain registration state from a previous instantiation of the
reliable transport session with the ETR and only request the refresh
of EID prefix state beyond some negotiated session progress marker.
Aa Map-Server authentication key change is treated as a DB change
event and will result in triggering a new Registration message to be
transmitted.
6.3. Map-Server Behavior
Received registrations create/update or delete mapping state.
A refresh with global scope is sent when a session between the ETR
and Map-Server is first established so the Map-Server can obtain the
complete database contents from the ETR. This refresh is also
serving as a capability signaling from the Map-Server to the ETR that
it can support reliable registration.
Refresh for rejected registrations sent (R bit set) when a new EID
prefix is configured on the Map-Server.
Refresh is sent whenever authentication key is changed or EID prefix
is deconfigured. Upon reception of the registration Map-Server can
decide whether to acknowledge the registration or issue rejection.
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Mapping Notification message sent whenever the mapping for a
registered or more specific prefix for which notifications are
requested changes. ETR acknowledgement or rejection messaging for
Mapping Notification is not required because the ETR decides how to
process the message based on the registered mapping information. If
the mapping information changes the resulting registration will
trigger a new Mapping Notification message from the Map-Server.
7. Security Considerations
The LISP reliable transport session SHOULD be authenticated. On
controlled RLOC networks that can guarantee that the source RLOC
address of data packets cannot be spoofed, the authentication check
can be a source address validation on the reliable transport packets.
When the RLOC network does not provide such guarantees, reliable
transport authentication SHOULD be used. Implementations SHOULD
support the TCP Authentication Option (TCP-AO) [RFC5925].
8. IANA Considerations
8.1. LISP Reliable Transport Message Types
Assignment of new LISP reliable transport message types is done
according to the "IETF Review" model defined in [RFC5266].
The initial content of the registry should be as follows.
Type Name Reference
----------- ---------------------------------------- --------------
0-15 Reserved This document
16 Error Notification This document
17 Registration Message This document
18 Registration Acknowledgement Message This document
19 Registration Rejected Message This document
20 Registration Refresh Message This document
21 Mapping Notification Message This document
22-30 Reserved for EID membership distribution TBD
31-64999 Unassigned
65000-65535 Reserved for Experimental Use
8.2. Transport Protocol Port Numbers
Following the guidelines of [RFC8126], the authors request IANA is to
assign a TCP port (4342 is suggested) to sustain reliable transport
over TCP.
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9. Contributors
Jesus Arango
Microsoft
United States of America
Email: jearango@microsoft.com
Johnson Leong
Uber Technologies
Market St.
San Francisco, CA 94103
United States of America
10. Acknowledgments
The authors would like to thank Noel Chiappa, Dino Farinacci, Jesper
Skriver, Andre Pelletier, Les Ginsberg and Alberto Rodriguez-Natal
for their contributions to this document.
11. Normative References
[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>.
[RFC5266] Devarapalli, V. and P. Eronen, "Secure Connectivity and
Mobility Using Mobile IPv4 and IKEv2 Mobility and
Multihoming (MOBIKE)", BCP 136, RFC 5266,
DOI 10.17487/RFC5266, June 2008,
<https://www.rfc-editor.org/info/rfc5266>.
[RFC9301] Farinacci, D., Maino, F., Fuller, V., and A. Cabellos,
Ed., "Locator/ID Separation Protocol (LISP) Control
Plane", RFC 9301, DOI 10.17487/RFC9301, October 2022,
<https://www.rfc-editor.org/info/rfc9301>.
Authors' Addresses
Balaji Pitta
Cisco Systems
Tasman Drive
San Jose, CA 95134
United States of America
Email: bvenkata@cisco.com
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Marc Portoles
Cisco Systems
Tasman Drive
San Jose, CA 95134
United States of America
Email: mportole@cisco.com
Darrel Lewis
ICANN
Los Angeles, CA 90292
United States of America
Email: darrel.lewis@icann.org
Isidor Kouvelas
Arista Networks Inc.
5453 Great America Parkway
Santa Clara, CA 95054
United States of America
Email: isidor@kouvelas.net
Chris Cassar
Rivian Automotive
United Kingdom
Email: christiancassar@acm.org
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