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Versions: 00                                                            
Internet Engineering Task Force            Alain Durand Jean-Luc Richier
INTERNET-DRAFT                                                      IMAG
Expire in six months                                      November, 1996



                         IPv6 network prefix notation


                      <draft-durand-ipv6prefix-00.txt>



1. Status

      This document is an Internet-Draft.  Internet-Drafts are working
      documents of the Internet Engineering Task Force (IETF), its
      areas, and its working groups.  Note that other groups may also
      distribute working documents as Internet-Drafts.

      Internet-Drafts are draft documents valid for a maximum of six
      months and may be updated, replaced, or obsoleted by other
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      Drafts as reference material or to cite them other than as
      ``work in progress.''

      To learn the current status of any Internet-Draft, please check
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      ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast).


2. Abstract

     This memo propose a text representation of IPv6 network prefixes.


3. Motivation

     RFC 1884 propose a text representation of IPv6 addresses.
     IPv6 addresses consist of a network prefix and a local identifier.

     Routing registry tables use network prefixes. Prefix lengths are
     important informations for routing algorithms. A compact
     notation to represent both informations is needed.


Durand+Richier                                                  [Page 1]


DRAFT               IPv6 network prefix notation           November 1996


4. Notation

     An IPv6 address is a string of 128 bits that can be represented
     per [RFC1884] by a string of hex digits separated by ":".
     This address is composed by two substrings, the network prefix and
     the local identifier. The boundary between those two substrings
     is characterized by an integer, the prefix length plen, in the
     interval [0 - 128].

     The proposed method to represent the network prefix is to
     complement the prefix plen bit string by (128 - plen) bits
     set to zero. This will make an IPv6 address. Then we represent
     this address using [RFC1884] to obtain an hex string. The trailing
     zeros are represented by "::". Eventually, we concatenate the
     symbol "/" followed by the decimal notation of plen.


5. Examples

     ::/96                     IPv6 prefix for IPv4 compatible addresses
     fe80::/10                 link local prefix
     5f06:b500::/32            site prefix
     5f06:b500:8158:1a00::/80  local area network prefix


6. Security considerations

     Security issues are not discussed in this memo.


7. References

     [RFC1884] Hinden, R., and S. Deering, "IP Version 6 Addressing
     Architecture", RFC 1884, December 1995.


8. Author address

     Alain Durand & Jean-Luc Richier
     Institut d'Informatique et de Mathematiques Appliquees de Grenoble
     (IMAG), BP 53 38041 Grenoble CEDEX 9 FRANCE

     Phone : +33 4 76 63 57 03
     Fax   : +33 4 76 51 49 64
     E-Mail: Alain.Durand@imag.fr Jean-Luc Richier@imag.fr




Durand+Richier                                                  [Page 2]