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Versions: 00 01 02 rfc5172                               Standards Track
IPv6 Working Group                          S.Varada        (Editor)
Internet Draft                              Transwitch
Obsoletes: RFC 2472 (if approved)           February 2008
Category: Standards track
Expires: July 2008

   Negotiation for IPv6 datagram compression using IPv6 Control Protocol

Status of this Memo
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Copyright Notice

      Copyright (C) The IETF Trust (2008).


      The Point-to-Point Protocol (PPP) provides a standard method of
      encapsulating Network Layer protocol information over
      point-to-point links.  PPP also defines an extensible Link Control
      Protocol, and proposes a family of Network Control Protocols
      (NCPs) for establishing and configuring different network-layer

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      The IPv6 Control Protocol (IPV6CP), which is an NCP for a PPP
      link, allows for the negotiation of desirable parameters for an
      IPv6 interface over PPP.

      This document defines the IPv6 datagram compression option that
      can be negotiated by a node on the link through the IPV6CP.

Table of Contents

   1. Introduction...................................................2
      1.1 Specification of Requirements..............................3
   2. IPV6CP Configuration Options...................................3
      2.1 IPv6-Compression-Protocol..................................3
   3. Security Considerations........................................5
   4. IANA Considerations............................................5
   5. Acknowledgments................................................6
   6. References.....................................................6
      6.1 Normative References.......................................6
      6.2 Informative References.....................................6
   Editor's Address..................................................7
   IPR Notice  ......................................................7
   Copyright Notice and Disclaimer...................................8

1. Introduction

      PPP [1] has three main components:

      1) A method for encapsulating datagrams over serial links.

      2) A Link Control Protocol (LCP) for establishing, configuring,
         and testing the data-link connection.

      3) A family of Network Control Protocols (NCPs) for establishing
         and configuring different network-layer protocols.

      In order to establish communications over a point-to-point link,
      each end of the PPP link must first send LCP packets to
      configure and test the data link.  After the link has been
      established and optional facilities have been negotiated as
      needed by the LCP, PPP must send NCP packets to choose and
      configure one or more network-layer protocols.  Once each of the
      chosen network-layer protocols has been configured, datagrams
      from each network-layer protocol can be sent over the link. The
      link will remain configured for communications until
      explicit LCP or NCP packets close the link down, or until some
      external event occurs (power failure at the other end, carrier
      drop, etc.).

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      In the IPv6 over PPP specification [2], the NCP, or IPV6CP, for
      establishing and configuring IPv6 over PPP is defined. The
      same specification defines the Interface Identifier parameter,
      which can be used to generate link-local and global unique IPv6
      addresses, for negotiation.

      In this specification, the compression parameter for use in IPv6
      datagram compression is defined. Together with RFC 5072 [2], this
      document obsoletes RFC 2472 [13]. However, no protocol changes
      have been introduced over RFC 2472.

1.1 Specification of Requirements

      In this document, several words are used to signify the
      requirements of the specification.

      The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
      "OPTIONAL" in this document are to be interpreted as described
      in [3].

2.  IPV6CP Configuration Options

      IPV6CP Configuration Options allow negotiation of desirable IPv6
      parameters.  IPV6CP uses the same Configuration Option format as
      defined for LCP [1] but with a separate set of Options.  If a
      Configuration Option is not included in a Configure-Request
      packet, the default value for that Configuration Option is

      The only IPV6CP option defined in this document is the IPv6-
      Compression-Protocol.  The Type field for this IPV6CP Option is as

            2 IPv6-Compression-Protocol

      Note that the up-to-date values of the IPV6CP Option Type field
      are specified in the on-line database of "Assigned Numbers"
      maintained at IANA [7].

2.1 IPv6-Compression-Protocol

      This Configuration Option provides a way to negotiate the use of a
      specific IPv6 packet compression protocol.  The
      IPv6-Compression-Protocol Configuration Option is used to indicate
      the ability to receive compressed packets.  Each end of the link

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      MUST separately request this option if bi-directional compression
      is desired.  By default, compression is not enabled.

      IPv6 compression negotiated with this option is specific to IPv6
      datagrams and is not to be confused with compression resulting
      from a compression method negotiated via the PPP Compression
      Control Protocol (CCP) [12], which potentially affects all

      A summary of the IPv6-Compression-Protocol Configuration Option
      format is shown below.  The fields are transmitted from left to

      0                   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
      |     Type      |    Length     |   IPv6-Compression-Protocol   |
      |    Data ...




          >= 4


         The IPv6-Compression-Protocol field is two octets and indicates
         the compression protocol desired.  Values for this field are
         always the same as the PPP Data Link Layer Protocol field
         values for that same compression protocol.

         IPv6-Compression-Protocol field values have been assigned in
         [14] for IPv6 Header Compression (004f), [4, 5] for IP Header
         Compression (0061), and [6] for Robust Header compression
         (ROHC) (0003). Other assignments can be made in documents that
         define specific compression algorithms.


         The Data field is zero or more octets and contains additional
         data as determined by the particular compression protocol.

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          No IPv6 compression protocol enabled.

3. Security Considerations

      Lack of proper link security, such as authentication, prior to
      data transfers may enable man-in-the middle attacks
      resulting in the loss of data integrity and confidentiality. The
      mechanisms that are appropriate for ensuring PPP link security
      are addressed below together with the reference to a generic
      threat model.

      The mechanisms that are appropriate for ensuring PPP link
      Security are: 1) Access Control Lists that apply filters on
      traffic received over the link for enforcing admission policy, 2)
      an Authentication protocol that facilitates negotiations between
      peers [8] to select an authentication method (e.g., MD5 [9]) for
      validation of the peer, and 3) an Encryption control protocol
      that facilitates negotiations between peers to select encryption
      algorithms (or,  crypto-suites) to ensure data confidentiality

      There are certain threats associated with peer interactions on a
      PPP link even with one or more of the above security measures in
      place. For instance, using the  MD5 authentication method [9]
      exposes one to replay attacks, in which an attacker could
      intercept and replay a station's identity and password hash to
      get access to a network. The user of this specification is
      advised to refer to [8], which presents a generic threat model,
      for an understanding of the threats posed to the security of a
      link. The reference [8] also gives a framework to specify
      requirements for the selection of an authentication method for a
      given application.

4. IANA Considerations

      There are no specific recommendations for the IANA on the
      assignment of values for the Type field of the IPv6 datagram
      compression option specified in section 2.1 of this document. The
      current assignment is up-to-date at [7].

      No action is needed either for the assignment of the

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      IPv6-Compression-Protocol values, as such values have already
      been defined by other documents listed in the Section 2.1. Values
      for this field  are always the same as the PPP Data Link Layer
      field values for that same compression protocol. As a result,
      future allocation of these values is governed by RFC 3818 [11]
      that requires IETF consensus process.

5. Acknowledgments

      The editor is grateful to Jari Arkko for the direction provided on
      this draft and James Carlson for helpful suggestions.
      Acknowledgements are also due to D. Haskins and E. Allen for the
      specification work done in RFC 2023 and RFC 2472.

6. References

6.1 Normative References

   [1] Simpson, W., "The Point-to-Point Protocol", STD 51, RFC 1661,
       July 1994.

   [2] Allen, E., Haskin, D., and, S. Varada, Ed., "IPv6 over PPP",
       RFC 5072, September 2007.

   [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.

   [4] Degermark M., B. Nordgren, and S. Pink, "IP Header Compression",
       RFC 2507, February 1999.

   [5] Koren T., S. Casner, and C. Bormann, "IP Header Compression Over
       PPP", RFC 3544, July 2003.

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

6.2 Informative References

   [7] IANA, "Assigned Numbers", http://www.iana.org/numbers.html

   [8] Aboba, R., Blunk, L., Vollbrecht, J., Carlson, J., and
       H. Levkowetz,Ed., "Extensible Authentication Protocol", RFC
       3748, June 2004.

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   [9] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April

   [10] Meyer, G., "The PPP Encryption Control Protocol (ECP)", RFC
        1968, June 1996.

   [11] Schryver, V., "IANA Considerations for the Point-to-Point
        Protocol (PPP)", RFC 3818, June 2004.

   [12] Rand, D., "The PPP Compression Control Protocol(CCP)", RFC 1962,
        June 1996.

   [13] Haskin D., and E. Allen, "IP Version 6 over PPP", RFC 2472,
        December 1998.

   [14] Haskin D., and E. Allen, "IP Version 6 over PPP", RFC 2023,
        October 1996.

Editor's Address

      Srihari Varada
      TranSwitch Corporation
      3 Enterprise Dr.
      Shelton, CT 06484. US.

      Phone: +1 203 929 8810
      EMail: varada@ieee.org

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Copyright Notice and Disclaimer

      Copyright (C) The IETF Trust (2008). This document is subject to
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      This document and the information contained herein are provided

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