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. 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 Souvatzis Expires 13 April 1997 [Page 1] 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. Souvatzis Expires 13 April 1997 [Page 2] INTERNET-DRAFT IPv6 Datagrams on ARCnet 13 October 1996 +-------+-------+---------------+-------+-------+---...------+ | 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. Souvatzis Expires 13 April 1997 [Page 3] INTERNET-DRAFT IPv6 Datagrams on ARCnet 13 October 1996 Author's Address Ignatios Souvatzis The NetBSD Project Muehlental 27 D-53639 Koenigswinter Germany Phone (work): +49 (228) 734316 EMail: is@netbsd.org Souvatzis Expires 13 April 1997 [Page 4]