Internet DRAFT - draft-boucadair-tcpm-dhc-converter
draft-boucadair-tcpm-dhc-converter
Network Working Group M. Boucadair
Internet-Draft C. Jacquenet
Intended status: Standards Track Orange
Expires: April 9, 2020 T. Reddy
McAfee
October 7, 2019
DHCP Options for 0-RTT TCP Converters
draft-boucadair-tcpm-dhc-converter-03
Abstract
Because of the lack of important TCP extensions, e.g., Multipath TCP
support at the server side, some service providers now consider a
network-assisted model that relies upon the activation of a dedicated
function called Transport Converters. For example, network-assisted
Multipath TCP deployment models are designed to facilitate the
adoption of Multipath TCP for the establishment of multi-path
communications without making any assumption about the support of
Multipath TCP by the remote servers. Transport Converters located in
the network are responsible for establishing multi-path
communications on behalf of endpoints, thereby taking advantage of
Multipath TCP capabilities to achieve different goals that include
(but are not limited to) optimization of resource usage (e.g.,
bandwidth aggregation), of resiliency (e.g., primary/backup
communication paths), and traffic offload management.
This document focuses on the explicit deployment scheme where the
identity of the Transport Converters is explicitly configured on
connected hosts. This document specifies DHCP (IPv4 and IPv6)
options to configure hosts with Converters parameters.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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material or to cite them other than as "work in progress."
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This Internet-Draft will expire on April 9, 2020.
Copyright Notice
Copyright (c) 2019 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. DHCPv6 Converter Option . . . . . . . . . . . . . . . . . . . 4
3.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . 5
4. DHCPv4 Converter Option . . . . . . . . . . . . . . . . . . . 6
4.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. DHCPv4 Client Behavior . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6.1. DHCPv6 Option . . . . . . . . . . . . . . . . . . . . . . 8
6.2. DHCPv4 Option . . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Appendix A. DHCP Server Configuration Guidelines . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
One of the promising deployment scenarios for Multipath TCP (MPTCP,
[RFC6824]) is to enable a host or a Customer Premises Equipment (CPE)
connected to multiple networks (e.g., DSL, LTE, WLAN) to optimize the
usage of such resources. A deployment scenario relies on MPTCP
Conversion Points (called, Transport Converters
[I-D.ietf-tcpm-converters]). A Converter terminates the extended TCP
(e.g., MPTCP, TCPinc) sessions established from a host, before
redirecting traffic into a legacy TCP session. Further Network-
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Assisted MPTCP deployment and operational considerations are
discussed in [I-D.nam-mptcp-deployment-considerations].
Figure 1 shows a deployment example of the Converters to assist
establishing MPTCP connections.
+------------+ _--------_ +----------------+
| | ( LTE ) | |
| Host +=======+ +===+ Backbone |
| | (_ _) | Network |
| | (_______) |+--------------+|
| | IP Network #1 || Converter ||------> Internet
| | || ||
| | |+--------------+|
| | IP Network #2 | |
| | _--------_ | |
| | ( DSL ) | |
| +=======+ +==+ |
| | (_ _) | |
+------------+ (_______) +----------------+
Figure 1: "Network-Assisted" MPTCP Design
[I-D.ietf-tcpm-converters] specifies the Converter as a function that
is installed by a network operator to aid the deployment of TCP
extensions and to provide the benefits of such extensions to clients.
A Transport Converter supports one or more TCP extensions.
[I-D.ietf-tcpm-converters] assumes the explicit mode that consists in
configuring explicitly the reachability information of the
Converter(s) on a host.
This document defines DHCPv4 [RFC2131] and DHCPv6 [RFC8415] options
that can be used to configure hosts with Converter IP addresses.
This specification assumes a Converter is reachable through one or
multiple IP addresses. As such, a list of IP addresses can be
returned in the DHCP Converter option. Also, it assumes the various
network attachments provided to an MPTCP-enabled host are managed by
the same administrative entity.
2. Terminology
This document makes use of the following terms:
o Converter: a function that terminates a transport flow and relays
all data received over it over another transport flow. This
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element is located upstream in the network. One or multiple
Converters can be deployed in the network side. The Converter
achieves the following:
* Listen for client sessions;
* Receive from a client the address of the final target server;
* Setup a session to the final server;
* Relay control messages and data between the client and the
server;
* Perform access controls according to local policies.
o DHCP refers to both DHCPv4 [RFC2131] and DHCPv6 [RFC8415].
o DHCP client denotes a node that initiates requests to obtain
configuration parameters from one or more DHCP servers.
o DHCP server refers to a node that responds to requests from DHCP
clients.
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.
3. DHCPv6 Converter Option
3.1. Format
The DHCPv6 Converter option can be used to configure a list of IPv6
addresses of a Converter.
The format of this option is shown in Figure 2. As a reminder, this
format follows the guidelines for creating new DHCPv6 options
(Section 5.1 of [RFC7227]).
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OPTION_V6_CONVERT | Option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ipv6-address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ipv6-address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: DHCPv6 Converter option
The fields of the option shown in Figure 2 are as follows:
o Option-code: OPTION_V6_CONVERT (TBA, see Section 6.1)
o Option-length: Length of the 'Converter IP Address(es)' field in
octets. MUST be a multiple of 16.
o Converter IPv6 Addresses: Includes one or more IPv6 addresses
[RFC4291] of the Converter to be used by the TCP client.
Note, IPv4-mapped IPv6 addresses (Section 2.5.5.2 of [RFC4291])
are allowed to be included in this option.
To return more than one Converter to the requesting DHCPv6 client,
the DHCPv6 server returns multiple instances of OPTION_V6_CONVERT.
Some guidelines for DHCP servers are elaborated in Appendix A.
3.2. DHCPv6 Client Behavior
Clients MAY request option OPTION_V6_CONVERT, as defined in
[RFC8415], Sections 18.2.1, 18.2.2, 18.2.4, 18.2.5, 18.2.6, and 21.7.
As a convenience to the reader, we mention here that the client
includes requested option codes in the Option Request Option.
The DHCPv6 client MUST be prepared to receive multiple instances of
OPTION_V6_CONVERT; each instance is to be treated separately as it
corresponds to a given Converter: there are as many Converters as
instances of the OPTION_V6_CONVERT option.
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If an IPv4-mapped IPv6 address is received in OPTION_V6_CONVERT, it
indicates that the Converter has the corresponding IPv4 address.
The DHCPv6 client MUST silently discard multicast and host loopback
addresses [RFC6890] conveyed in OPTION_V6_CONVERT.
4. DHCPv4 Converter Option
4.1. Format
The DHCPv4 Converter option can be used to configure a list of IPv4
addresses of a Converter. The format of this option is illustrated
in Figure 3.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| List-Length | List of |
+-+-+-+-+-+-+-+-+ |
/ Converter IPv4 Addresses /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
| List-Length | List of | |
+-+-+-+-+-+-+-+-+ | |
/ Converter IPv4 Addresses / |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
. ... . Optional
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| List-Length | List of | |
+-+-+-+-+-+-+-+-+ | |
/ Converter IPv4 Addresses / |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ---
Figure 3: DHCPv4 Converter option
The fields of the option shown in Figure 3 are as follows:
o Code: OPTION_V4_CONVERT (TBA, see Section 6.2);
o Length: Length of all included data in octets. The minimum length
is 5.
o List-Length: Length of the "List of Converter IPv4 Addresses"
field in octets; MUST be a multiple of 4.
o List of Converter IPv4 Addresses: Contains one or more IPv4
addresses of the Converter to be used by the TCP client. The
format of this field is shown in Figure 4.
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o OPTION_V4_CONVERT can include multiple lists of Converter IPv4
addresses; each list is treated separately as it corresponds to a
given Converter.
When several lists of Converter IPv4 addresses are to be included,
"List-Length" and "Converter IPv4 Addresses" fields are repeated.
0 8 16 24 32 40 48
+-----+-----+-----+-----+-----+-----+--
| a1 | a2 | a3 | a4 | a1 | a2 | ...
+-----+-----+-----+-----+-----+-----+--
IPv4 Address 1 IPv4 Address 2 ...
This format assumes that an IPv4 address is encoded as a1.a2.a3.a4.
Figure 4: Format of the List of Converter IPv4 Addresses
OPTION_V4_CONVERT is a concatenation-requiring option. As such, the
mechanism specified in [RFC3396] MUST be used if OPTION_V4_CONVERT
exceeds the maximum DHCPv4 option size of 255 octets.
Some guidelines for DHCP servers are elaborated in Appendix A.
4.2. DHCPv4 Client Behavior
To discover one or more Converters, the DHCPv4 client MUST include
OPTION_V4_CONVERT in a Parameter Request List Option [RFC2132].
The DHCPv4 client MUST be prepared to receive multiple lists of
Converter IPv4 addresses in the same OPTION_V4_CONVERT; each list is
to be treated as a separate Converter instance.
The DHCPv4 client MUST silently discard multicast and host loopback
addresses [RFC6890] conveyed in OPTION_V4_CONVERT.
5. Security Considerations
The security considerations in [RFC2131] and [RFC8415] are to be
considered.
Generic Convert security considerations are discussed in
[I-D.ietf-tcpm-converters].
MPTCP-related security considerations are discussed in [RFC6824].
Means to protect the Converter against Denial-of-Service (DoS)
attacks must be enabled. Such means include the enforcement of
ingress filtering policies at the boundaries of the network. In
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order to prevent exhausting the resources of the Converter by
creating an aggressive number of simultaneous subflows for each MPTCP
connection, the administrator should limit the number of allowed
subflows per host for a given connection.
Attacks outside the domain can be prevented if ingress filtering is
enforced. Nevertheless, attacks from within the network between a
host and a Converter instance are yet another actual threat. Means
to ensure that illegitimate nodes cannot connect to a network should
be implemented.
Traffic theft is also a risk if an illegitimate Converter is inserted
in the path. Indeed, inserting an illegitimate Converter in the
forwarding path allows to intercept traffic and can therefore provide
access to sensitive data issued by or destined to a host. To
mitigate this threat, secure means to discover a Converter should be
enabled.
6. IANA Considerations
6.1. DHCPv6 Option
IANA is requested to assign the following new DHCPv6 Option Code in
the registry maintained in http://www.iana.org/assignments/
dhcpv6-parameters:
Option Name Value
----------------- -----
OPTION_V6_CONVERT TBA
6.2. DHCPv4 Option
IANA is requested to assign the following new DHCPv4 Option Code in
the registry maintained in http://www.iana.org/assignments/bootp-
dhcp-parameters/:
Option Name Value Data length Meaning
----------------- ----- ----------- ---------------------------------
OPTION_V4_CONVERT TBA Variable; Includes one or multiple lists of
the minimum Converter IP addresses; each list
length is is treated as a separate
5. Converter.
7. Acknowledgements
Many thanks to Olivier Bonaventure for the feedback on this document.
Olivier suggested to define the option as a name but that design
approach was debated several times within the dhc wg.
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Thanks to Dan Seibel, Bernie Volz, Niall O'Reilly, Simon Hobson, and
Ted Lemon for the feedback on the dhc wg mailing list.
8. References
8.1. Normative References
[I-D.ietf-tcpm-converters]
Bonaventure, O., Boucadair, M., Gundavelli, S., Seo, S.,
and B. Hesmans, "0-RTT TCP Convert Protocol", draft-ietf-
tcpm-converters-12 (work in progress), October 2019.
[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>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997,
<https://www.rfc-editor.org/info/rfc2132>.
[RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the
Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396,
DOI 10.17487/RFC3396, November 2002,
<https://www.rfc-editor.org/info/rfc3396>.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, DOI 10.17487/RFC4291, February
2006, <https://www.rfc-editor.org/info/rfc4291>.
[RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
"TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,
<https://www.rfc-editor.org/info/rfc6824>.
[RFC6890] Cotton, M., Vegoda, L., Bonica, R., Ed., and B. Haberman,
"Special-Purpose IP Address Registries", BCP 153,
RFC 6890, DOI 10.17487/RFC6890, April 2013,
<https://www.rfc-editor.org/info/rfc6890>.
[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>.
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[RFC8415] Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
RFC 8415, DOI 10.17487/RFC8415, November 2018,
<https://www.rfc-editor.org/info/rfc8415>.
8.2. Informative References
[I-D.nam-mptcp-deployment-considerations]
Boucadair, M., Jacquenet, C., Bonaventure, O., Henderickx,
W., and R. Skog, "Network-Assisted MPTCP: Use Cases,
Deployment Scenarios and Operational Considerations",
draft-nam-mptcp-deployment-considerations-01 (work in
progress), December 2016.
[RFC0793] Postel, J., "Transmission Control Protocol", STD 7,
RFC 793, DOI 10.17487/RFC0793, September 1981,
<https://www.rfc-editor.org/info/rfc793>.
[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
<https://www.rfc-editor.org/info/rfc7227>.
[RFC7844] Huitema, C., Mrugalski, T., and S. Krishnan, "Anonymity
Profiles for DHCP Clients", RFC 7844,
DOI 10.17487/RFC7844, May 2016,
<https://www.rfc-editor.org/info/rfc7844>.
[RFC7969] Lemon, T. and T. Mrugalski, "Customizing DHCP
Configuration on the Basis of Network Topology", RFC 7969,
DOI 10.17487/RFC7969, October 2016,
<https://www.rfc-editor.org/info/rfc7969>.
Appendix A. DHCP Server Configuration Guidelines
DHCP servers that support the DHCP Converter option can be configured
with a list of IP addresses of the Converter(s). If multiple IP
addresses are configured, the DHCP server MUST be explicitly
configured whether all or some of these addresses refer to:
1. the same Converter: the DHCP server returns multiple addresses in
the same instance of the DHCP Converter option.
2. distinct Converters : the DHCP server returns multiple lists of
Converter IP addresses to the requesting DHCP client (encoded as
multiple OPTION_V6_CONVERT or in the same OPTION_V4_CONVERT);
each list refers to a distinct Converter.
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Precisely how DHCP servers are configured to separate lists of IP
addresses according to which Converter they refer to is out of scope
for this document. However, DHCP servers MUST NOT combine the IP
addresses of multiple Converters and return them to the DHCP client
as if they were belonging to a single Converter, and DHCP servers
MUST NOT separate the addresses of a single Converter and return them
as if they were belonging to distinct Converters. For example, if an
administrator configures the DHCP server by providing a Fully
Qualified Domain Name (FQDN) for a Converter, even if that FQDN
resolves to multiple addresses, the DHCP server MUST deliver them
within a single server address block.
DHCPv6 servers that implement this option and that can populate the
option by resolving FQDNs will need a mechanism for indicating
whether to query A records or only AAAA records. When a query
returns A records, the IP addresses in those records are returned in
the DHCPv6 response as IPv4-mapped IPv6 addresses.
Since this option requires support for IPv4-mapped IPv6 addresses, a
DHCPv6 server implementation will not be complete if it does not
query A records and represent any that are returned as IPv4-mapped
IPv6 addresses in DHCPv6 responses. The mechanism whereby DHCPv6
implementations provide this functionality is beyond the scope of
this document.
For guidelines on providing context-specific configuration
information (e.g., returning a regional-based configuration), and
information on how a DHCP server might be configured with FQDNs that
get resolved on demand, see [RFC7969].
Authors' Addresses
Mohamed Boucadair
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
Christian Jacquenet
Orange
Rennes
France
Email: christian.jacquenet@orange.com
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Tirumaleswar Reddy
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
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