Internet Key Exchange Protocol Version 2 (IKEv2) Message Fragmentation
RFC 7383
| Document | Type | RFC - Proposed Standard (November 2014; No errata) | |
|---|---|---|---|
| Author | Valery Smyslov | ||
| Last updated | 2015-10-14 | ||
| Replaces | draft-smyslov-ipsecme-ikev2-fragmentation | ||
| Stream | IETF | ||
| Formats | plain text html pdf htmlized bibtex | ||
| Reviews | |||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Paul Hoffman | ||
| Shepherd write-up | Show (last changed 2014-04-18) | ||
| IESG | IESG state | RFC 7383 (Proposed Standard) | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Kathleen Moriarty | ||
| Send notices to | (None) | ||
| IANA | IANA review state | Version Changed - Review Needed | |
| IANA action state | RFC-Ed-Ack | ||
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 fragmentation on IKEv2 and acknowledges this problem. Smyslov Standards Track [Page 2] RFC 7383 IKEv2 Fragmentation November 2014Show full document text