Internet Key Exchange Protocol Version 2 (IKEv2) Message Fragmentation
RFC 7383
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Type |
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RFC - Proposed Standard
(November 2014; No errata)
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Last updated |
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2015-10-14
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Replaces |
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draft-smyslov-ipsecme-ikev2-fragmentation
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IETF
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plain text
pdf
html
bibtex
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WG state
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Submitted to IESG for Publication
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Document shepherd |
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Paul Hoffman
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Shepherd write-up |
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Show
(last changed 2014-04-18)
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| IESG |
IESG state |
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RFC 7383 (Proposed Standard)
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Consensus Boilerplate |
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Yes
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Telechat date |
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Responsible AD |
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Kathleen Moriarty
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Send notices to |
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(None)
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| IANA |
IANA review state |
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Version Changed - Review Needed
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IANA action state |
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RFC-Ed-Ack
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Internet Engineering Task Force (IETF) V. Smyslov
Request for Comments: 7383 ELVIS-PLUS
Category: Standards Track November 2014
ISSN: 2070-1721
Internet Key Exchange Protocol Version 2 (IKEv2) Message Fragmentation
Abstract
This document describes a way to avoid IP fragmentation of large
Internet Key Exchange Protocol version 2 (IKEv2) messages. This
allows IKEv2 messages to traverse network devices that do not allow
IP fragments to pass through.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7383.
Copyright Notice
Copyright (c) 2014 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
(http://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.
Smyslov Standards Track [Page 1]
RFC 7383 IKEv2 Fragmentation November 2014
Table of Contents
1. Introduction ....................................................2
1.1. Problem Description ........................................2
1.2. Proposed Solution ..........................................3
1.3. Conventions Used in This Document ..........................4
2. Protocol Details ................................................4
2.1. Overview ...................................................4
2.2. Limitations ................................................4
2.3. Negotiation ................................................5
2.4. Using IKE Fragmentation ....................................5
2.5. Fragmenting Message ........................................6
2.5.1. Selecting Fragment Size .............................8
2.5.2. PMTU Discovery ......................................9
2.5.3. Fragmenting Messages Containing Unprotected
Payloads ...........................................11
2.6. Receiving IKE Fragment Message ............................11
2.6.1. Replay Detection and Retransmissions ...............13
3. Interaction with Other IKE Extensions ..........................14
4. Transport Considerations .......................................14
5. Security Considerations ........................................15
6. IANA Considerations ............................................16
7. References .....................................................16
7.1. Normative References ......................................16
7.2. Informative References ....................................16
Appendix A. Design Rationale ......................................19
Appendix B. Correlation between IP Datagram Size and Encrypted
Payload Content Size ..................................19
Acknowledgements ..................................................20
Author's Address ..................................................20
1. Introduction
1.1. Problem Description
The Internet Key Exchange Protocol version 2 (IKEv2), specified in
[RFC7296], uses UDP as a transport for its messages. Most IKEv2
messages are relatively small, usually below several hundred bytes.
A notable exception is the IKE_AUTH exchange, which requires fairly
large messages, up to several KB, especially when certificates are
transferred. When the IKE message size exceeds the path MTU, it gets
fragmented at the IP level. The problem is that some network
devices, specifically some NAT boxes, do not allow IP fragments to
pass through. This apparently blocks IKE communication and,
therefore, prevents peers from establishing an IPsec Security
Association (SA). Section 2 of [RFC7296] discusses the impact of IP
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