IPng Working Group Matt Crawford Internet Draft Fermilab March 21, 1997 Transmission of IPv6 Packets over Ethernet 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. Internet Drafts may be updated, replaced, or obsoleted by other documents at any time. It is not appropriate to use Internet Drafts as reference material or to cite them other than as a "working draft" or "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 ds.internic.net (US East Coast), nic.nordu.net (Europe), ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim). Distribution of this memo is unlimited. 1. Introduction This memo specifies the frame format for transmission of IPv6 packets and the method of forming IPv6 link-local addresses and statelessly autoconfigured addresses on Ethernet networks. It also specifies the content of the Source/Target Link-layer Address option used in Router Solicitation, Router Advertisement, Neighbor Solicitation and Neighbor Advertisement messages when those messages are transmitted on an Ethernet. 2. Maximum Transmission Unit The default MTU size for IPv6 [IPV6] packets on an Ethernet is 1500 octets. This size may be reduced by a Router Advertisement [DISC] containing an MTU option which specifies a smaller MTU, or by manual configuration of each node. If a Router Advertisement received on Expires September 21, 1997 Crawford [Page 1] Internet Draft IPv6 Over Ethernet March 21, 1997 an Ethernet interface has an MTU option specifying an MTU larger than 1500, or larger than a manually configured value MTU, if any, that MTU option must be ignored. 3. Frame Format IPv6 packets are transmitted in standard Ethernet frames. The Ethernet header contains the Destination and Source Ethernet addresses and the ethernet type code, which must contain the value 86DD hexadecimal. The data field contains the IPv6 header followed immediately by the payload, and possibly padding octets to meet the minimum frame size for Ethernet. 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination | +- -+ | Ethernet | +- -+ | Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source | +- -+ | Ethernet | +- -+ | Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 0 0 0 0 1 1 0 1 1 0 1 1 1 0 1| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv6 | +- -+ | header | +- -+ | and | +- -+ / payload ... / +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ (Each tic mark represents one bit.) 4. Stateless Autoconfiguration The interface token [CONF] for an Ethernet interface is the EUI-64 identifier [EUI64] derived from the interface's built-in 48-bit IEEE Expires September 21, 1997 Crawford [Page 2] Internet Draft IPv6 Over Ethernet March 21, 1997 802 address. The OUI of the Ethernet address (the first three octets) becomes the company_id of the EUI-64 (the first three octets). The fourth and fifth octets of the EUI are set to the fixed value FFFE hexadecimal. The last three octets of the Ethernet address become the last three octets of the EUI-64. For example, the interface token for an Ethernet interface whose built-in address is, in hexadecimal and in canonical bit order, 34-56-78-9A-BC-DE would be 34-56-78-FF-FE-9A-BC-DE. A different MAC address set manually or by software should not be used to derive the interface token. An IPv6 address prefix used for stateless autoconfiguration of an Ethernet interface must have a length of 64 bits. 5. Link-Local Addresses The IPv6 link-local address [AARCH] for an Ethernet interface is formed by appending the interface token, as defined above, to the prefix FE80::/64. 10 bits 54 bits 64 bits +----------+-----------------------+----------------------------+ |1111111010| (zeros) | Interface Token | +----------+-----------------------+----------------------------+ 6. Address Mapping -- Unicast The procedure for mapping IPv6 unicast addresses into Ethernet link-layer addresses is described in [DISC]. The Source/Target Link-layer Address option has the following form when the link layer is Ethernet. Expires September 21, 1997 Crawford [Page 3] Internet Draft IPv6 Over Ethernet March 21, 1997 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +- Ethernet -+ | | +- Address -+ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option fields: Type 1 for Source Link-layer address. 2 for Target Link-layer address. Length 1 (in units of 8 octets). Ethernet Address The 48 bit Ethernet IEEE 802 address, in canonical bit order. This is the address the interface currently responds to, and may be different from the built-in address used to derive the interface token. 7. Address Mapping -- Multicast An IPv6 packet with a multicast destination address DST, consisting of the sixteen octets DST[1] through DST[16], is transmitted to the Ethernet multicast address whose first two octets are the value 3333 hexadecimal and whose last four octets are the last four octets of DST. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 1 1 0 0 1 1|0 0 1 1 0 0 1 1| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DST[13] | DST[14] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | DST[15] | DST[16] | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Security Considerations Security considerations are not addressed in this memo. Expires September 21, 1997 Crawford [Page 4] Internet Draft IPv6 Over Ethernet March 21, 1997 8. References [AARCH] R. Hinden, S. Deering "IP Version 6 Addressing Architecture", RFC 1884. [CONF] S. Thomson, T. Narten, "IPv6 Stateless Address Autoconfiguration", RFC 1971. [DISC] T. Narten, E. Nordmark, W. A. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC 1970. [EUI64] "64-Bit Global Identifier Format Tutorial", http://standards.ieee.org/db/oui/tutorials/EUI64.html. [IPV6] S. Deering, R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 1883. 9. Author's Address Matt Crawford Fermilab MS 368 PO Box 500 Batavia, IL 60510 USA Phone: +1 630 840-3461 EMail: crawdad@fnal.gov Expires September 21, 1997 Crawford [Page 5]