Network Working Group                                         E. Ertekin
Internet-Draft                                               C. Christou
Expires: April 17, 2009                                        R. Jasani
                                                             J. Pezeshki
                                                     Booz Allen Hamilton
                                                        October 14, 2008

    IKEv2 Extensions to Support Robust Header Compression over IPsec

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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 . . . . . . . . . . . . . . . . . . . . . . . . 6
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     6.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     6.2.  Informative 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, PROFILES, 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
   message type 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
   indicate that the Notify payload is conveying ROHC channel
   parameters.  The Notify Payload (as defined in [IKEV2]) is
   illustrated in Figure 1 below:

                            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
       ! Next Payload  !C!  RESERVED   !         Payload Length        !
       !  Protocol ID  !   SPI Size    !      Notify Message Type      !
       !                                                               !
       ~                Security Parameter Index (SPI)                 ~
       !                                                               !
       !                                                               !
       ~                       Notification Data                       ~
       !                                                               !

                       Figure 1. Notify Payload format.

   The fields of the Notify Payload are set as follows:

   Next Payload (1 octet)
      Identifier for the payload type of the next payload in the
      message.  Further details can be found in [IKEV2].

   Critical (1 bit)
      Since all IKEv2 implementations must support the Notify Payload,
      this value is zero.

   Protocol ID (1 octet)
      Since this Notification message is used during the creation of a
      Child 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)

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      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]):

                            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            |    RESERVED   |PROFILES_LENGTH!
       !                                                               !
       ~                           PROFILES...                         ~
       !                                                               !
       !                                                               !
       ~                     INTEGRITY ALGORITHMS...                   ~
       !                                                               !

     Figure 2.  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

   PROFILES_LENGTH (1 octet)
      The total number of profiles contained within the PROFILES field
      (note that each ROHC profile is 2-octets in length).

   PROFILES (variable)
      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

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      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.
      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).
      3.  A ROHCoIPsec implementation may choose to negotiate a value of
          "0" in this field (i.e., NONE, as defined in the Integrity
          Algorithm Transform ID registry).

   The negotiated set of ROHC parameters are associated with the
   inbound/outbound pair of SAs established by each IKEv2
   CREATE_CHILD_SA exchange.

   The following ROHC channel parameters are not negotiated:
   o  LARGE_CIDS: This value is implicitly determined by the value of
      MAX_CID (e.g. if MAX_CID is <= 15, LARGE_CIDS is assumed to be 0).
   o  MRRU: IPsec implementations will always implement path MTU
      discovery; therefore, ROHC packets will never need to use ROHC
      segmentation over an IPsec SA.  As a result, this value will
      always be zero, and does not need to be negotiated.
   o  FEEDBACK_FOR: 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 channel 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.

5.  Acknowledgments

   The authors would like to thank Mr. Sean O'Keeffe, Mr. James Kohler,

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   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
   o  Mr. Yoav Nir

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

6.  References

6.1.  Normative References

              Ertekin, E., Christou, C., and R. Jasani, "Integration of
              Robust Header Compression over IPsec Security
              Associations", work in progress , October 2008.

   [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.

   [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.

6.2.  Informative References

              Pelletier, G. and K. Sandlund, "RObust Header Compression
              Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and UDP

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              Lite", , May 2007.

              IANA, "IKEv2 Parameters,
              January 2008.

Authors' Addresses

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


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


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


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


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