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Versions: 00 01 02 RFC 5172

IPv6 Working Group                              S.Varada (Editor)
Internet Draft                                Transwitch
Category: Standards track                       May 2007
Expires: November 2007

   Negotiation for IPv6 datagram compression using IPv6 Control Protocol
               <draft-ietf-ipv6-compression-nego-v2-00.txt>


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Copyright Notice

      Copyright (C) The IETF Trust (2007).

Abstract

      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
      protocols.

      The IPv6 Control Protocol (IPv6CP), which is an NCP for a PPP
      link, allows for the negotiation of desirable parameters for the
      IPv6 interface over PPP.


Varada                                                        [Page 1]

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      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........................................4
   4. IANA Considerations............................................5
   5. Acknowledgments................................................5
   6. References.....................................................6
      6.1 Normative References.......................................6
      6.2 Informative References.....................................6
   Editor's Address..................................................6
   IPR Notice  ......................................................6
   Copyright Notice and Disclaimer...................................7


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.).

      In the IPv6 over PPP specification [2], the NCP, or IPv6CP, for
      establishing and configuring the IPv6 over PPP is defined. The
      same specification defines the Interface Identifier parameter,


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      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.

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
      NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
      "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
      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
      assumed.

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

            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 [4].

2.1 IPv6-Compression-Protocol

      Description
      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
      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 negotiations via Compression Control Protocol (CCP), which
      potentially affect all datagrams.


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


      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 ...
      +-+-+-+-+

        Type

          2

        Length

          >= 4

        IPv6-Compression-Protocol

         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.

         No IPv6-Compression-Protocol field values are currently
         assigned. Specific assignments will be made in documents that
         define specific compression algorithms.

        Data

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



        Default

          No IPv6 compression protocol enabled.

3. Security Considerations

      Lack of proper link security, such as authentication, prior to
      the data transfer may lead to such attacks as the man-in-the



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      middle 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 [5] to select an authentication method (e.g., MD5 [6]) for
      validation of the peer, and 3) an Encryption protocol that
      facilitates negotiations between peers to select encryption
      algorithms (or,  crypto-suites) to ensure data confidentiality
      [7]).

      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 MD5 authentication method [6] exposes
      one to replay attack, where 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 [5], which presents a generic threat model, for an
      understanding of the threats posed to the security of a link. The
      reference [5] also gives framework to specify requirements for
      the selection of an authentication method for a given
      application.

4. IANA Considerations

      The author has no specific recommendations for the IANA on the
      assignment of a value for the Type field of IPv6 datagram
      compression option specified in this specification. The current
      assignment is up-to-date at [4]. However, the reference to the
      RFC number needs to be updated when such a number is assigned.


5. Acknowledgments

      The editor is grateful to Jari Arkko for the direction provided on
      this draft.







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6. References

6.1 Normative References

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

   [2] Varada, S., et. al., "IPv6 over PPP," drafts-ietf-ipv6-over-ppp-
       v2-03.txt, May 2007.

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

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


6.2 Informative References

   [5]  Aboba, R., et. al., "Extensible Authentication Protocol," RFC
        3748, June 2004.

   [6]  Rivest, R., "The MD5 Message-Digest Algorithm," RFC 1321, April
        1992.

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

Editor's Address

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

      Phone: +1 203 929 8810
      EMail: varada@txc.com

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