6to4 Provider Managed Tunnels

6to4 Provider Managed Tunnels (6to4-PMT) provide a framework that canhelp manage 6to4 tunnels operating in an anycast configuration. The6to4-PMT framework is intended to serve as an option for operators tohelp improve the experience of 6to4 operation when conditions of thenetwork may provide sub-optimal performance or break normal 6to4operation. 6to4-PMT supplies a stable provider prefix and forwardingenvironment by utilizing existing 6to4 relays with an added functionof IPv6 Prefix Translation. This operation may be particularlyimportant in NAT444 infrastructures where a customer endpoint may beassigned a non-RFC1918 address, thus breaking the return path foranycast-based 6to4 operation. 6to4-PMT has been successfully used in aproduction network, implemented as open source code, and implementedby a major routing vendor. This document is not an Internet StandardsTrack specification; it is published for informational purposes.