[dns-operations] Quick anycast primer

[John Payne]

On Jul 14, 2006, at 12:28 PM, Edward Lewis wrote:

> At 12:03 PM -0400 7/14/06, John Payne wrote:
>
>> As we're talking about a network service, the only topology that
>> makes sense is the IP network topology, which has only a small
>> correlation to the physical paths of the fibers and cables.
>
> Thanks to port-level filtering, load balancing, and other load
> management techniques, the IP network topology may not be the one
> that makes sense.  Okay, you may get to the LAN where the service is
> rendered via the IP topology rules, but once there the traffic for
> one service may get shunted elsewhere.  If the shunting is noticable
> to the client, traffic may be directed to another IP address, yadda,
> yadda, yadda.
>
> (Alluding to the possibility that layer 3 load balancing and layer 7
> load balancing might have unintended consequences.)
>
> Nothing's so clear any more.

The IP network topology will decide which cluster you'll go to in an  
anycast cloud.

Beyond that is implementation specific.