IPng Working Group A. Conta (Lucent) INTERNET-DRAFT July 1997 Transmission of IPv6 Packets over IPv6 and IPv4 Tunnels. Specification draft-conta-ipv6-trans-tunnel-00.txt Status of this Memo This document is an Internet-Draft. Internet-Drafts are working doc- uments of the Internet Engineering Task Force (IETF), its Areas, and its Working Groups. Note that other groups may also distribute work- ing 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 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. Abstract This memo describes the transmission of IPv6 packets over IPv6 and IPv4 tunnels, and the IPv6 tunnel link local addresses. 1. Introduction This document specifies the frame format for transmission of IPv6 packets and the method of forming IPv6 link-local addresses on IPv6 tunnels. It also specifies the content of the Source/Target Link- layer Address option used in Inverse Neighbor Solicitation, and Neighbor Advertisement messages when those messages are transmitted over an IPv6 tunnel [IND_TUN]. Conta Expires in six months [Page 1] INTERNET-DRAFT IPv6 over IPv6 and IPv4 Tunnels 29 July 1997 The keywords MUST, MUST NOT, MAY, OPTIONAL, REQUIRED, RECOMMENDED, SHALL, SHALL NOT, SHOULD, SHOULD NOT are to be interpreted as defined in RFC 2119. 2. Maximum Transmission Unit The default MTU size for IPv6 or IPv4 tunnels is the MTU of the underlying physical interface less the size of the tunnel headers [TUNNEL]. The MTU can be reduced by manual configuration. An IPv6 or IPv4 tun- nel MTU cannot be larger than its default size. 3. Frame format IPv6 packets are transmitted in standard IPv6 packet format - IPv6 packets are payloads of IPv6 Tunnel packets. The IPv6 tunnel header contains as Source and Destination the tunnel entry-point and exit-point node addresses. The tunnel IPv6 header is filled in conforming to [TUNNEL]. 4. Stateless Autoconfiguration This applies only for IPv6 tunnels. The interface token [CONF] for an IPv6 tunnel pseudo-interface must be unique on the virtual link represented by the tunnel, i.e., the tunnel's end-point nodes must have distinct pseudo-interface tokens. The default IPv6 tunnel pseudo-interface token is based on the under- lying physical interface EUI-64 identifier [ETHER]. It is the result of masking the forth and fifth octets of the EUI-64 identifier with the fixed FFFC hexadecimal value. For instance for an underlying physical interface EUI-64 identifier 36-56-78-FF-FE-9A-BC-DE. the IPv6 tunnel pseudo-interface token is: 36-56-78-FF-FC-9A-BC-DE. An IPv6 address prefix used for stateless autoconfiguration of an IPv6 tunnel interface must have a length of 64 bits. Conta Expires in six months [Page 2] INTERNET-DRAFT IPv6 over IPv6 and IPv4 Tunnels 29 July 1997 5. Link-Local Addresses This applies only to IPv6. The IPv6 link-local address [AARCH] for an IPv6 tunnel pseudo- interface is formed by appending the pseudo-interface token, as defined above, to the prefix FE80::/64. 10 bits 54 bits 64 bits +----------+-----------------------+----------------------------+ |1111111010| (zeros) | Pseudo-Interface Token | +----------+-----------------------+----------------------------+ 6. Address Mapping - Unicast The procedure for mapping IPv6 addresses to tunnel IPv6 or IPv4 addresses is described in [IND_TUN]. The Source/Target Virtual Link-layer Address option has the following form when the (virtual) link layer is an IPv6 or IPv4 tunnel. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0 | Type | Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 4 | | + + 8 | | + IPv6 Address + 12 | | + +-------------------------------+ 16 | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + 20 | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Conta Expires in six months [Page 3] INTERNET-DRAFT IPv6 over IPv6 and IPv4 Tunnels 29 July 1997 or 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 0 | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 2 | IPv4 | +- -+ 4 | Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 6 | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Option fields: Type 1 for Source Link-layer address. 2 for Target Link-layer address. Length 3 (in units of 8 octets) for IPv6 addresses 1 (in units of 8 octets) for IPv4 addresses IPv6 Address The 128 bit IPv6 address of the IPv6 tunnel pseudo-interface. or IPv4 Address The 32 bit IPv4 address of the IPv4 tunnel pseudo-interface. 7. Security Considerations The mechanisms defined in this document for generating IPv6 tunnel address tokens are intended to provide virtual link uniqueness. There is no security protection from duplication through forgery or accident. 8. Acknowledgments This draft is a result of a discussion with Steve Deering about the applicability and benefits of Neighbor Discovery for IPv6 tunnels. After more thinking and in combination with IPv6 Inverse Neighbor Discovery things seemed to fall into place. The IPv4 part is an idea that Dan Harrington suggested, and it was very easy to add. Conta Expires in six months [Page 4] INTERNET-DRAFT IPv6 over IPv6 and IPv4 Tunnels 29 July 1997 9. References [RFC-1883] S. Deering, R. Hinden, "Internet Protocol Version 6 Speci- fication" [RFC-1885] A. Conta, and S. Deering "Internet Control Message Proto- col for the Internet Protocol Version 6 (IPv6)" [RFC-1970] T. Narten, E. Nordmark, W.Simpson "Neighbor Discovery for IP Version 6 (IPv6)" [IND_TUN] A. Conta "IPv6 ND Extensions for Inverse Neighbor Discov- ery. [TUNNEL] A. Conta, S. Deering "Generic IPv6 Encapsulation". [ETHER] M. Crawford "Transmission of IPv6 packets over Ethernet" Authors' Addresses Alex Conta Lucent Technologies Inc. 300 Baker Ave, Suite 100 Concord, MA 01742 +1-508-287-2842 email: aconta@lucent.com Conta Expires in six months [Page 5]