On 13/03/2007, at 12:36 PM, jamie baddeley wrote:

On Tue, 2007-03-13 at 12:29 +1300, Nathan Ward wrote:
>
> Seems to me some people don't think through the logical  
> consequences of
> their actions.  It also seems to me that anyone needing failover in  
> less
> than about an hour wants a different solution than updating DNS  
> entries
> (load balancer, anycast, etc).

These solutions are about failover between sites where anycast is (a)  
not possible because of lack of BGP,
I wonder how many sites that serve "big content" and are concerned about loadsharing are not BGP connected. Not many I suspect.
 or (b) a concern for connection� 
oriented protocols (TCP). 
Correct me if I'm wrong but this is only a concern under a failure mode of an anycast node? So combined with probability of risk and ease of resolution (browser reload), is this really a big concern?

Ah but you didn't read the next sentence which was "It's also useful to balance load between�sites, as Simon suggested Google and Yahoo do.". That's not so easy to do with anycast - the site selection is done by the network not by you (or your automagic boxes).

If you don't care about that, anycast would work fine. It would work even better if you have lots of small files, ie. no long running TCP sessions. Not terribly good for people who do large files though, and is probably one of the reasons that people like Akamai use BGP-fed DNS views (or similar) for this sort of thing. Not as bad for live streaming I suppose, because people don't need to start the `download' again, or have much manual intervention (sure, having to start a download from scratch is software dependent).

Nathan Ward