IPv6 Transmission Mechanisms
IPv4 and IPv6 networks are not directly interoperable, which means that a transition mechanism is needed in order to permit hosts on an IPv4 network to communicate with hosts on an IPv6 network, and vice versa. The links below are links to videos developed by RIPE NCC will help you understand some of these techniques.
There are several relay services that are of interest to ISPs because they can set up tunnel relay servers to either provide better service to a mixed v4/v6 Internet, or to enable full reachability regardless of the end-user's version of IP. The following pages deal with the main automatic tunnel/relay technologies:
- Cisco 6to4 Relay Service
- FreeBSD Teredo Relay
- Juniper 6to4 Relay Service
- Linux or BSD 6to4 Relays
- ISPs currently announcing a 6to4 prefix
There is also useful information about these technologies on these pages:
The following conversation from the NANOG list explains how effective placement of 6to4 relays in content-provider networks can greatly reduce the likelihood of latency issues in a mixed v4/v6 Internet.
And here is a brief Q&A that makes it clear that installing proper relays gives you greater visibility of your IPv6 traffic.