[c-nsp] Anycast services

[Sam Stickland]

Hi,

Comments inline.

> -----Original Message-----
> From: cisco-nsp-bounces at puck.nether.net [mailto:cisco-nsp-
> bounces at puck.nether.net] On Behalf Of Tim Durack
> Sent: 18 May 2006 16:20
> To: cisco-nsp at puck.nether.net
> Subject: [c-nsp] Anycast services
> 
> The subject of Anycast DNS has raised my curiosity. Anyone tried
> anycast of other services, such as a web proxy? Or is there a better
> way to do this?
> 
> I'm interested in this from a geographical redundancy perspective, as
> opposed to purely clustering for load-balancing/redundancy.

You can't ensure that packets routed to an Anycast address will always
arrive at the same end point. They might arrive at a different node.

Hence, you can't use Anycast for any kind of stateful service (e.g. TCP/IP).
The correct approach to using it here would be to Anycast your DNS servers,
and only have your DNS return entries for servers/cluster-groups that are
known to be up.

Sam