Internet DRAFT - draft-smyslov-ipsecme-ikev2-reliable-transport
draft-smyslov-ipsecme-ikev2-reliable-transport
Network Working Group V. Smyslov
Internet-Draft ELVIS-PLUS
Intended status: Standards Track 28 December 2023
Expires: 30 June 2024
Use of Reliable Transport in the Internet Key Exchange Protocol Version
2 (IKEv2)
draft-smyslov-ipsecme-ikev2-reliable-transport-01
Abstract
The Internet Key Exchange protocol version 2 (IKE2) can operate
either over unreliable (UDP) transport or over reliable (TCP)
transport. If TCP is used, then IPsec tunnels created by IKEv2 also
use TCP. This document specifies how to decouple IKEv2 and IPsec
transports, so that IKEv2 can operate over TCP, while IPsec tunnels
use unreliable transport. This feature allows IKEv2 to effectively
exchange large blobs of data (e.g. when post-quantum algorithms are
employed) while avoiding performance problems which arise when TCP is
used for IPsec.
Status of This Memo
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology and Notation . . . . . . . . . . . . . . . . . . 3
3. Protocol Details . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
6.1. Normative References . . . . . . . . . . . . . . . . . . 4
6.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
The Internet Key Exchange protocol version 2 (IKEv2) [RFC7296]
originally used unreliable transport (UDP) for its messages. Later
it was extended to use TCP [RFC9329] where UDP is blocked. UDP is
still considered as a preferred transport for IKEv2, and TCP is only
used if UDP datagrams cannot get through.
Originally IKEv2 peers exchanged relatively small amount of data, so
that simple retransmission mechanism on top of UDP with no congestion
control sufficed. The situation has changed when post-quantum
cryptographic algorithms started to be incorporated into IKEv2
[RFC9370]. Most of post-quantum algorithms require IKE peers to
exchange much more data, than classical algorithms, up to tens (or
even hundreds) Kbytes. Few proposals exist that allow to overcome
the 64 Kbytes limitation on the size of an IKE payload
([I-D.nir-ipsecme-big-payload],
[I-D.smyslov-ipsecme-ikev2-extended-pld],
[I-D.tjhai-ikev2-beyond-64k-limit]).
When IKE messages grow up to tens (or even hundreds) Kbytes, using
UDP as a transport will become challenging. Use of IKE fragmentation
[RFC7383] avoids IP fragmentation problems and also allows each IKE
message fragment to fit into UDP datagram, even if the original
message doesn't. However, all IKE fragments are always being sent
(and retransmitted) at once, so that with the increased number of
fragments and the lack of congestion control the simple
retransmission mechanism of IKEv2 will perform poorly, perhaps even
making more truble to the network.
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Using reliable transport (like TCP) for IKEv2 would be a solution to
the problem. However, the current use of TCP as defined in [RFC9329]
implies that ESP SAs are also encapsulated in TCP, which has negative
impact on IPsec performance (see Section 9 of [RFC9329].
This specification allows to decouple IKE and IPsec transports, so
that it makes possible to negotiate and use reliable transport for
IKEv2 while maintaining using unreliable transport for IPsec.
The idea to decouple IKE and IPsec transports was originally
presented in [I-D.tjhai-ikev2-beyond-64k-limit].
2. Terminology and Notation
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. Protocol Details
If the initiator supports this extension and is configured to use and
it and also anticipates that large amount of data may be exchanged in
this SA (e.g. it proposes Key Exchange transforms with large public
keys), then the initiator starts the IKE_SA_INIT exchange using UDP
port 4500 and includes a new status type notification
RELIABLE_IKE_TRANSPORT (<TBA by IANA>) into the request message. The
RELIABLE_IKE_TRANSPORT notification has protocol 0, SPI size 0 and
contains no data. Using UDP port 4500 for the IKE_SA_INIT messages
is explicitly allowed by [RFC7296], and ensures that IPsec packets
can get through if they are UDP encapsulated.
If the responder supports this extension and is configured to use it
and the IKE_SA_INIT request contains the RELIABLE_IKE_TRANSPORT
notification, then the responder sends back this notification in the
response.
Initiator (UDP:4500) Responder (UDP:4500)
-------------------------------------------------------------------
HDR , SAi1, KEi1, Ni,
[N(NAT_DETECTION_SOURCE_IP),
N(NAT_DETECTION_DESTINATION_IP),]
N(RELIABLE_IKE_TRANSPORT) --->
HDR, SAr1, KEr1, Nr,
[N(NAT_DETECTION_SOURCE_IP),
N(NAT_DETECTION_DESTINATION_IP),]
<--- N(RELIABLE_IKE_TRANSPORT)
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In this case the initiator MUST switch to TCP using destination port
4500 in the next exchange (IKE_INTERMEDIATE or IKE_AUTH) and the
responder MUST be prepared to receive the next exchange request
message on TCP port 4500.
Initiator (TCP) Responder (TCP:4500)
-------------------------------------------------------------------
HDR, SK{...} --->
<--- HDR, SK{...}
All subsequent IKE exchanges MUST continue to use TCP transport. In
particular, peers MUST NOT try to swich IKE transport to UDP as
defined in Sections 7.1 and 7.3 of [RFC9329]. All recommendations of
[RFC9329] regarding maintaning TCP connection apply accordingly.
With this IKE extension child SAs are created as defined in [RFC7296]
- they either use direct transport over IP or are UDP encapsulated if
NAT is detected. Note, that in the latter case peers are responsible
for maintaining NAT mapping by sending NAT keepalives (see
Section 2.23 of [RFC7296]).
4. Security Considerations
Section 10 of [RFC9329] discusses security implications of using TCP
as IKE transport.
5. IANA Considerations
This document defines a new Notify Message Type in the "Notify
Message Types - Status Types" registry:
<TBA> RELIABLE_IKE_TRANSPORT
6. References
6.1. 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>.
[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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[RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T.
Kivinen, "Internet Key Exchange Protocol Version 2
(IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October
2014, <https://www.rfc-editor.org/info/rfc7296>.
[RFC9329] Pauly, T. and V. Smyslov, "TCP Encapsulation of Internet
Key Exchange Protocol (IKE) and IPsec Packets", RFC 9329,
DOI 10.17487/RFC9329, November 2022,
<https://www.rfc-editor.org/info/rfc9329>.
6.2. Informative References
[RFC7383] Smyslov, V., "Internet Key Exchange Protocol Version 2
(IKEv2) Message Fragmentation", RFC 7383,
DOI 10.17487/RFC7383, November 2014,
<https://www.rfc-editor.org/info/rfc7383>.
[RFC9370] Tjhai, CJ., Tomlinson, M., Bartlett, G., Fluhrer, S., Van
Geest, D., Garcia-Morchon, O., and V. Smyslov, "Multiple
Key Exchanges in the Internet Key Exchange Protocol
Version 2 (IKEv2)", RFC 9370, DOI 10.17487/RFC9370, May
2023, <https://www.rfc-editor.org/info/rfc9370>.
[I-D.tjhai-ikev2-beyond-64k-limit]
Tjhai, C., Heider, T., and V. Smyslov, "Beyond 64KB Limit
of IKEv2 Payloads", Work in Progress, Internet-Draft,
draft-tjhai-ikev2-beyond-64k-limit-03, 28 July 2022,
<https://datatracker.ietf.org/doc/html/draft-tjhai-ikev2-
beyond-64k-limit-03>.
[I-D.nir-ipsecme-big-payload]
Nir, Y., "A Larger Internet Key Exchange version 2 (IKEv2)
Payload", Work in Progress, Internet-Draft, draft-nir-
ipsecme-big-payload-02, 23 July 2023,
<https://datatracker.ietf.org/doc/html/draft-nir-ipsecme-
big-payload-02>.
[I-D.smyslov-ipsecme-ikev2-extended-pld]
Smyslov, V., "Extended IKEv2 Payload Format", Work in
Progress, Internet-Draft, draft-smyslov-ipsecme-ikev2-
extended-pld-01, 6 March 2023,
<https://datatracker.ietf.org/doc/html/draft-smyslov-
ipsecme-ikev2-extended-pld-01>.
Author's Address
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Valery Smyslov
ELVIS-PLUS
PO Box 81
Moscow (Zelenograd)
124460
Russian Federation
Phone: +7 495 276 0211
Email: svan@elvis.ru
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