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Versions: 00 01 02 03 04 05 rfc2497                                     
INTERNET-DRAFT                                              I. Souvatzis
Expires 13 April 1997                                 The NetBSD Project
                                                         13 October 1996


  A Method for the Transmission of IPv6 Packets over ARCnet Networks.
                  <draft-souvatzis-ipv6-arcnet-01.txt>


Status of this Memo

   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 documents at any
   time.  It is inappropriate to use Internet- 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 the
   ``1id-abstracts.txt'' listing contained in the Internet- Drafts
   Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
   munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
   ftp.isi.edu (US West Coast).

   Distribution of this memo is unlimited. Please send comments to the
   author.

Introduction

   This memo specifies a frame format for transmission of IPv6 [IPV6]
   packets and the method of forming IPv6 link-local addresses on ARCnet
   networks. It also specifies the content of the Source/Target Link-
   layer Address option used by the Router Solicitation, Router
   Advertisement, Neighbor Solicitation, and Neighbor Advertisement
   messages described in [DISC], when those messages are transmitted on
   an ARCnet.

Frame Format

   IPv6 packets are link layer fragmented and reassembled according to
   [PHDS]. A brief but sufficient discussion of this fragmentation
   method can be found in [ARCIP4].

   The protocol id used is hex D4, the same as for IPv4. IPv6 packets
   are recognized by looking at the version number in the high half of



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INTERNET-DRAFT          IPv6 Datagrams on ARCnet         13 October 1996


   the first octet of the data, which is 4 for IPv4 and 6 for IPv6.

Maximum Transmission Unit

   The maximum IPv6 packet length possible using this encapsulation
   method is 60,480 octets. Since this length is impractical, all ARCnet
   implementations on a given ARCnet network will need to agree on a
   smaller value. In the presence of a router, this size should be
   reduced by a Router Advertisement [DISC] containing an MTU option, or
   by manual configuration of each node. If a Router Advertisement is
   received with an MTU option specifying an MTU larger than 60480, or
   larger than a manually configured value less than 60480, that MTU
   option must be ignored.

   In any case, implementations must be able to send and receive IPv6
   datagrams up to 576 octets in length, and are strongly encouraged to
   handle IPv6 datagrams up to 1500 octets in length.

   Implementations may accept arriving IPv6 datagrams which are larger
   than their configured maximum transmission unit.  They are not
   required to discard such datagrams.

Stateless Auto-configuration and Link-Local Addresses

   The address token [CONF] for an ARCnet interface is the interface's
   configured 8-bit hardware address, in canonical bit order.

   An IPv6 address prefix used for stateless auto-configuration of an
   ARCnet interface must be 120 bits in length.

   The IPv6 Link-local address [AARCH] for an ARCnet interface is formed
   by appending the interface's hardware address to the 120-bit prefix
   FE80::.

   +-------+-------+-------+-------+-------+-------+------+---------------+
   |  FE      80      00      00      00      00      00     00           |
   +-------+-------+-------+-------+-------+-------+------+---------------+
   |  00      00      00      00      00      00      00  | ARCnet address|
   +-------+-------+-------+-------+-------+-------+------+---------------+

Address Mapping -- Unicast

   The procedure for mapping IPv6 addresses into ARCnet link-layer
   addresses is described in [DISC]. The Source/Target link layer
   Address option has the following form when the link layer is ARCnet.






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   +-------+-------+---------------+-------+-------+---...------+
   | Type  |Length | ARCnet Address|   5 octets of padding      |
   +-------+-------+---------------+-------+-------+---...------+

   Option fields:
   Type    1 for Source Link-layer address.
           2 for Target Link-layer address.
   Length  1 (in units of 8 octets).

   ARCnet address

           The 8 bit ARCnet address, in canonical bit order.

Address Mapping -- Multicast

   As ARCnet only provides 1 multicast address (hex 00), all IPv6
   multicast packets must be mapped to this address.


Security Considerations


   Security issues are not discussed in this memo.

References

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

   [ARCIPV4] Provan, D., "Transmitting IP Traffic over ARCNET Networks",
   RFC1201, Novell, Inc., February 1991

   [CONF] Thomson, S., and T. Narten, "IPv6 Stateless Address
   Autoconfiguration", RFC 1971, August 1996.

   [DISC] Narten, T., Nordmark, E., and W. Simpson, "Neighbor Discovery
   for IP Version 6 (IPv6)", RFC 1970, August 1996.


   [IPV6] S. Deering, R. Hinden, Internet Protocol, Version 6 (IPv6)
   Specification.  RFC1883.


   [PHDS] Novell, Inc., "ARCNET Packet Header Definition Standard",
   Novell, Inc., November 1989.






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Author's Address

   Ignatios Souvatzis
   The NetBSD Project
   Muehlental 27
   D-53639 Koenigswinter
   Germany

   Phone (work): +49 (228) 734316

   EMail: is@netbsd.org








































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