Re: I-D ACTION:draft-palet-v6ops-tun-auto-disc-00.txt

[Pekka Savola <pekkas@netcore.fi>]

On Wed, 21 Apr 2004, Brian E Carpenter wrote:
> Section 4 puzzles me. My understanding is that anycast is best
> if used in single-shot mode: send an anycast UDP packet, pick one of
> the replies, and then use unicast to establish a session with the host 
> that sent that reply. You won't use the anycast address again after
> that initial discovery packet. It's the same as the initial broadcast
> in DHCP or the initial multicast in SLP. 
> 
> Admittedly, that's not the model in RFC 3068 (Anycast for 6to4). But 6to4
> is a special case, since there is no tunnel negotiation.

Shared-unicast DNS root servers and other load-balanced services also 
use the similar technique as 6to4.

I.e., when you just use one address, it's closest to you whereever you 
roam in the network where there are multiple anycasting servers.

Obviously, this only works if you don't need to store state in the
anycast server, or if it's OK to lose the state if the routing changes
or you move.

There doesn't have to be stored state if the IPv4 address is embedded
completely or encoded in a reversible fashion in the IPv6 address.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings