RE: implications of 6to4 for v6coex

[Christian Huitema <huitema@windows.microsoft.com>]

> Offering IPv6-only service isn't even sufficient to relieve providers
> of the requirement to deploy relays, because the return paths to
> 2002::/16 and 2001::/32 need to be made reliable for IPv6-only
> subscribers.  The requirement to provide reliable 6to4 and Teredo
> relays will be with us until the happy day that the IPv4
> specifications can be archived off in the Historic category.  I expect
> the Heat Death Of The Universe to arrive before that happens.

Teredo has a very different deployment strategy than 6to4.

Teredo relays are typically deployed only after an ISP has already deployed a V6 service. The relays will be used by remote V4 users connecting to the native IPv6 customers of that ISP. Teredo relays are not advertised on the V4 Internet. If the ISP ensures that the advertisements for 2001::/32 are not sent to third parties, then the relays can only be used by that ISP's customer.

Dual-stack IPv6 users can deploy their own Teredo relays. For example, the provider of a big service over IPv6 could deploy a Teredo relay as part of the service, for exclusive use by that service.

-- Christian Huitema