INTERNET-DRAFT I. Souvatzis
Expires 22 January 1998 The NetBSD Project
23 July 1997
A Method for the Transmission of IPv6 Packets over ARCnet Networks.
<draft-souvatzis-ipv6-arcnet-02.txt>
Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working
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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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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::/120
+-------+-------+-------+-------+-------+-------+------+---------------+
| 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
Stationenweg 29
D-53332 Bornheim
Germany
Phone (work): +49 (228) 734316
EMail: is@netbsd.org
Souvatzis Expires 22 January 1998 [Page 4]
