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Versions: 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 5857

Network Working Group                                        J. Pezeshki
Internet-Draft                                                E. Ertekin
Expires: February 16, 2009                                     R. Jasani
                                                             C. Christou
                                                     Booz Allen Hamilton
                                                         August 15, 2008

    IKEv2 Extensions to Support Robust Header Compression over IPsec

Status of this Memo

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   In order to integrate RoHC with IPsec [ROHCOIPSEC], a mechanism is
   needed to negotiate RoHC configuration parameters between end-points.
   Internet Key Exchange (IKE) is a mechanism which can be leveraged to
   handle these negotiations.  This document specifies extensions to
   IKEv2 [IKEV2] that will allow RoHC and its associated configuration
   parameters to be negotiated for IPsec security associations (SAs).

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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 [IPSEC] can result in
   the inefficient utilization of bandwidth.  Coupling RoHC [ROHC] with
   IPsec offers an efficient way to transfer protected IP traffic.

   The operation of RoHCoIPsec [ROHCOIPSEC] requires configuration
   parameters to be negotiated between the compressor and decompressor.
   Current specifications for hop-by-hop RoHC negotiate these parameters
   through a link-layer protocol such as Point-to-Point Protocol (PPP)
   (i.e.  RoHC over PPP [ROHCPPP]).  Since key exchange protocols (e.g.
   IKEv2) can be used to negotiate parameters between IPsec peers, this
   document defines extensions to IKEv2 to negotiate RoHC parameters for

2.  RoHC Channel Negotiation

   The initialization of a RoHC session requires the negotiation of a
   set of configuration parameters (e.g.  MAX_CID, etc.).  The following
   subsections define extensions to IKEv2 which enables an initiator to
   propose a set of RoHC parameters; the responder selects the
   appropriate parameters from this list, and responds with the accepted
   parameters for the RoHC channel.

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 new Notify
   payload is used during the IKE_AUTH and CREATE_CHILD_SA exchanges to
   negotiate these parameters.

   The Notify payload sent by the initiator contains the configuration
   parameters for the RoHC implementation.  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.
   The accepted parameters are an intersection between 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.  If the initiator does not receive a Notify Payload
   with the responder's accepted RoHC channel parameters, RoHC must not

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   be enabled on the Child SA.

   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)
      If the RoHC parameters are set at SA creation, this field must be
      set to zero.  If this notification concerns an existing SA, this
      value may be set to (2) AH [AH], or (3) ESP [ESP].

   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 (default values for the
   configuration parameters are consistent with [ROHCPPP]):

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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 for the ROHC_SUPPORTED Notify
                               message type.

   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 RoHC is implemented over an IPsec
      SA, RoHC segmentation is not possible.  Therefore, the MRRU value
      must be set to zero, indicating that no segment headers are
      allowed on the channel.

   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 packet
      headers 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.
      It is noted that:
      1.  The length of this field is inferred from the Notify Payload's
          "Payload Length" field ([IKEV2], Section 3.10).
      2.  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).

   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
   o  Dr. Joseph Touch

   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.

              IANA, "IKEv2 Parameters,
              January 2008.

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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