On Wed, Dec 2, 2009 at 4:04 AM, <michael.dillon@bt.com> wrote:
What are the broken anycast routers?
They are routers that announce 2002::/16 and 192.88.99.1, but are very far away, drop packets, have unreliable connectivity, etc. etc. etc. Our data shows that 6to4 and Teredo have a ~50ms latency penalty compared to native IPv6, and we know of at least one case in which a third-party 6to4 gateway was causing connectivity problems because the network that set it up had put in place, and then neglected to increase a bandwidth throttle on it.
Why can't they be fixed?
Because they are in someone else's network and it's an operational burden to create specific BGP policy to avoid them. Even if you maintain your own 6to4 relays, that only takes care of the outgoing path - you're still subject to them on the way back.