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Network Working Group                                        J. Pezeshki
Internet-Draft                                                E. Ertekin
Intended status: Experimental                                  R. Jasani
Expires: July 3, 2008                                        C. Christou
                                                     Booz Allen Hamilton
                                                       December 31, 2007

    IKEv2 Extensions to Support Robust Header Compression over IPsec

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Copyright Notice

   Copyright (C) The IETF Trust (2007).


   When using Robust Header Compression (RoHC [ROHC]) in conjunction
   with IPsec [IPSEC] (i.e.  [RoHCOIPSEC]) a mechanism is needed to
   negotiate RoHC configuration parameters between end-points prior to
   operation.  Internet Key Exchange (IKE) is a mechanism which can be
   leveraged to handle these negotiations.  This document specifies

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   extensions to Internet Key Exchange (IKEv2 [IKEV2]) that will allow
   RoHC and its associated configuration parameters to be negotiated for
   IPsec security associations (SAs).

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  RoHC Channel Negotiation  . . . . . . . . . . . . . . . . . . . 3
     2.1.  Negotiation of RoHC Channel Parameters  . . . . . . . . . . 3
   3.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
   6.  Normative References  . . . . . . . . . . . . . . . . . . . . . 7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9

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1.  Introduction

   Increased packet header overhead due to IPsec protection can result
   in inefficient utilization of bandwidth.  Coupling RoHC with IPsec
   offers an efficient way to transfer protected IP traffic.

   For proper RoHCoIPsec [ROHCOIPSEC] operation, RoHC requires
   configuration parameters to be negotiated between the compressor and
   decompressor, prior to operation.  Current specifications of hop-by-
   hop RoHC schemes negotiate these parameters through a link-layer
   protocol such as Point-to-Point Protocol (PPP) (i.e.  RoHC over PPP
   [ROHCPPP]).  Similarly, key exchange protocols (e.g.  IKEv2) are
   commonly used to negotiate parameters between IPsec peers before a SA
   can be established.  This document proposes the use of IKEv2 to
   handle RoHC channel configuration for RoHCoIPsec, and details various
   extensions to IKEv2 which are intended to provide this functionality.

2.  RoHC Channel Negotiation

   The initialization of a RoHC session requires the negotiation of a
   set of configuration parameters (e.g.  MAX_CID, etc.).  As such, a
   mechanism must exist for a RoHC enabled device to share a list of
   supported RoHC parameters with its peer, and for the peer to select
   the appropriate parameters from this list.

   Similarly, negotiable parameters must also be shared between IPsec
   peers before a SA can be established.  To perform this negotiation, a
   key exchange protocol, IKEv2, is commonly used.  IKEv2 is an
   extensible protocol that negotiates parameters via request/response
   message pairs (i.e. exchanges).

   A set of extensions to IKEv2 can be defined, which will allow for
   RoHC parameters to be negotiated during the creation and rekeying of
   Child SAs.  This new Notify payload will contain values for the set
   of RoHC parameters to be negotiated between the two RoHC peers.

2.1.  Negotiation of RoHC Channel Parameters

   RoHC configuration parameters will be negotiated at either the
   establishment or rekeying of a Child SA.  Specifically, a Notify
   payload will be used during the IKE_AUTH and CREATE_CHILD_SA
   exchanges to negotiate the RoHCoIPsec session.  The Notify payload
   sent by the initiator will contain the configuration parameters for
   the RoHC scheme.  Upon receipt of the initiator's request, the
   responder will either ignore the payload (if it doesn't support RoHC
   or the proposed parameters) or respond with a Notify payload that
   contains the accepted RoHC channel parameters.  These accepted

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   parameters are subset of the parameters proposed by the initiator,
   and the parameters supported by the responder (e.g. if the initiator
   proposes a MAX_CID value of 15, but the responder only supports a
   MAX_CID value of 13, the responder will respond with a value of 13,
   which is supported by both parties).  Note that only one Notify
   payload is used to convey RoHC parameters per exchange.  If multiple
   Notify payloads relaying RoHC parameters are received by the
   responder, all but the first such Notify payload must be dropped.

   A new Notify Message Type value, denoted ROHC_SUPPORTED, will be
   added to indicate that the Notify payload is conveying RoHC channel
   parameters.  Additionally, several fields of the Notify payload (as
   defined in [IKEV2]) are set as follows:

   Critical (1 bit)
      This value is set to zero to indicate that the recipient must skip
      this payload if it does not understand the payload type code in
      the Next Payload field of the previous payload.

   RESERVED (7 bits)
      Must be sent as zero, and must be ignored on receipt.

   Protocol ID (1 octet)
      Since the RoHC parameters are set at SA creation, and thus do not
      relate to an existing SA, this field must be set to zero.

   SPI Size (1 octet)
      This value must be set to zero, since no SPI is applicable (RoHC
      parameters are set at SA creation, thus the SPI has not been

   Notify Message Type (2 octets)
      This field must be set to ROHC_SUPPORTED.

   RoHC configuration parameters will be communicated via a new Notify
   message type, denoted ROHC_SUPPORTED.  The RoHC configuration
   parameters will be listed within the Notification Data field of the
   Notify payload, in the following format:

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                        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
   !            MAX_CID            !              MRRU             !
   !           MAX_HEADER          !         PROFILE LENGTH        !
   !                                                               !
   ~                           PROFILES...                         ~
   !                                                               !
   !                                                               !
   ~                     INTEGRITY ALGORITHMS...                   ~
   !                                                               !

   Figure 1: Notification Data field

   MAX_CID (2 octets)
      The MAX_CID field indicates the maximum value of a context
      identifier.  This value must be at least 0 and at most 16383 (The
      value 0 implies having one context).

      Suggested value: 15

      Note: The value of LARGE_CIDS will be implicitly determined by
      this value (i.e. if MAX_CID is <= 15, LARGE_CIDS will be assumed
      to be 0).

   MRRU (2 octets)
      The MRRU field indicates the maximum reconstructed reception unit
      (see [ROHC], section 5.1.1).

      Suggested value: 0

      The MRRU value is used in conjunction with the segmentation
      protocol defined in RoHC.  Since RoHCoIPsec will generally be
      implemented across multiple link-layer "hops", segmentation will
      not normally be required.  In these cases the MRRU value will be
      set to zero, indicating that no segment headers are allowed on the

   MAX_HEADER (2 octets)
      The largest header size in octets that may be compressed.

      Suggested value: 168 octets

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      Note: The MAX_HEADER parameter is not used for all RoHC profiles.
      If none of the RoHC profiles require this field, this value is

   PROFILE LENGTH (2 octets)
      The total number of profiles contained within the PROFILES field
      (note that each RoHC profile is 2-octets in length).

      The set of profiles to be enabled for the RoHC process.  Profiles
      are further detailed in [ROHC].  In addition, several common
      profiles are defined in [ROHCPROF].  These 16-bit profile
      identifiers are to be sent in network byte order.

      The set of Integrity Algorithms that may be use to ensure the
      integrity of the decompressed packets (i.e. ensure that the
      packets are properly decompressed).  Each Integrity Algorithm is
      represented by a 2-octet value that corresponds to the value
      listed in [IKEV2-PARA] "For Transform Type 3 (Integrity
      Algorithm)" section.

         Note: The length of this field is inferred from the Notify
         Payload's "Payload Length" field ([IKEV2], Section 3.10).

         Note: The key for this Integrity Algorithm is computed using
         the same method as is used to compute IPsec's Integrity
         Algorithm key ([IKEV2], Section 2.17).

   Note: When a pair of SAs are created (one in each direction), the
   RoHC channel parameter FEEDBACK_FOR is set implicitly to the other SA
   of the pair (i.e. the SA pointing in the reverse direction).

3.  Security Considerations

   The RoHC parameters negotiated via IKEv2 do not add any new
   vulnerabilities beyond those associated with the normal operation of

4.  IANA Considerations

   This document defines a new Notify Message (Status Type).  Therefore,
   IANA is requested to allocate one value from the IKEv2 Notify Message
   registry to indicate ROHC_SUPPORTED.  Note that, since this Notify
   Message is a Status Type, values ranging from 0 to 16383 must not be
   allocated for ROHC_SUPPORTED.

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5.  Acknowledgments

   The authors would like to thank Mr. Sean O'Keeffe, Mr. James Kohler,
   and Ms. Linda Noone of the Department of Defense, as well as Mr. Rich
   Espy of OPnet for their contributions and support in the development
   of this document.  The authors would also like to thank Mr. Tero
   Kivinen for providing his technical expertise for this document.  In
   addition, the authors would like to thank the following for their
   numerous reviews and comments to this document:

   o  Dr. Stephen Kent
   o  Dr. Carsten Bormann
   o  Mr. Lars-Erik Jonnson
   o  Mr. Pasi Eronen

   Finally, the authors would also like to thank Mr. Tom Conkle, Ms.
   Michele Casey, and Mr. Etzel Brower.

6.  Normative References

   [ROHC]     Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
              Hannu, H., Jonsson, L., Hakenberg, R., Koren, T., Le, K.,
              Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K.,
              Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header
              Compression (ROHC): Framework and four profiles: RTP, UDP,
              ESP, and uncompressed", RFC 3095, July 2001.

   [IPSEC]    Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

              Ertekin, E., Christou, C., and R. Jasani, "Integration of
              Robust Header Compression over IPsec Security
              Associations", work in progress , June 2006.

   [IKEV2]    Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.

   [ROHCPPP]  Bormann, C., "Robust Header Compression (ROHC) over PPP",
              RFC 3241, April 2002.

   [AH]       Kent, S., "IP Authentication Header", RFC 4302,
              December 2005.

   [ESP]      Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, December 2005.

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              Pelletier, G. and K. Sandlund, "RObust Header Compression
              Version 2 (RoHCv2): Profiles for RTP, UDP, IP, ESP and UDP
              Lite", www.iana.org/assignments/ROHC-pro-ids , May 2007.

              "IKEv2 Parameters",
              http://www.iana.org/assignments/ikev2-parameters ,
              November 2007.

Authors' Addresses

   Jonah Pezeshki
   Booz Allen Hamilton
   13200 Woodland Park Dr.
   Herndon, VA  20171

   Email: pezeshki_jonah@bah.com

   Emre Ertekin
   Booz Allen Hamilton
   13200 Woodland Park Dr.
   Herndon, VA  20171

   Email: ertekin_emre@bah.com

   Rohan Jasani
   Booz Allen Hamilton
   13200 Woodland Park Dr.
   Herndon, VA  20171

   Email: jasani_rohan@bah.com

   Chris Christou
   Booz Allen Hamilton
   13200 Woodland Park Dr.
   Herndon, VA  20171

   Email: christou_chris@bah.com

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