RFC 2893 IPv6 Transition Mechanisms August 2000 Table of Contents 1. Introduction............................................. 2 1.1. Terminology......................................... 3 1.2. Structure of this Document.......................... 5 2. Dual IP Layer Operation.................................. 6 2.1. Address Configuration............................... 7 2.2. DNS................................................. 7 2.3. Advertising Addresses in the DNS.................... 8 3. Common Tunneling Mechanisms.............................. 9 3.1. Encapsulation....................................... 11 3.2. Tunnel MTU and Fragmentation........................ 11 3.3. Hop Limit........................................... 13 3.4. Handling IPv4 ICMP errors........................... 13 3.5. IPv4 Header Construction............................ 15 3.6. Decapsulation....................................... 16 3.7. Link-Local Addresses................................ 17 3.8. Neighbor Discovery over Tunnels..................... 18 4. Configured Tunneling..................................... 18 4.1. Default Configured Tunnel........................... 19 4.2. Default Configured Tunnel using IPv4 "Anycast Address" 19 4.3. Ingress Filtering................................... 20 5. Automatic Tunneling...................................... 20 5.1. IPv4-Compatible Address Format...................... 20 5.2. IPv4-Compatible Address Configuration............... 21 5.3. Automatic Tunneling Operation....................... 22 5.4. Use With Default Configured Tunnels................. 22 5.5. Source Address Selection............................ 23 5.6. Ingress Filtering................................... 23 6. Acknowledgments.......................................... 24 7. Security Considerations.................................. 24 8. Authors' Addresses....................................... 24 9. References............................................... 25 10. Changes from RFC 1933................................... 26 11. Full Copyright Statement................................ 29 1. Introduction The key to a successful IPv6 transition is compatibility with the large installed base of IPv4 hosts and routers. Maintaining compatibility with IPv4 while deploying IPv6 will streamline the task of transitioning the Internet to IPv6. This specification defines a set of mechanisms that IPv6 hosts and routers may implement in order to be compatible with IPv4 hosts and routers. The mechanisms in this document are designed to be employed by IPv6 hosts and routers that need to interoperate with IPv4 hosts and utilize IPv4 routing infrastructures. We expect that most nodes in Gilligan & Nordmark Standards Track