[dns-operations] opting in to stupid DNS tricks
matt at conundrum.com
Wed Feb 23 14:14:39 UTC 2011
On 23-Feb-2011, at 08:06, Joe Abley wrote:
>> As an anycast DNS provider, my answer to this is: because BGP
>> optimizes for the shortest AS path, not the shortest path, or the
>> lowest RTT, or the most bandwidth, or the most capacity. At
>> $DAYJOB we give the same answer from everywhere, but we don't just
>> rely on BGP to give great performance. Anycast gives availability,
>> and helps to sink regional DDoS.. it does not provide performance.
> I think this depends very much on what you're optimising for. For
> any of the clouds that I have had a hand in deploying or running,
> performance means availability, not RTT.
> If you expect your responses to be cached and answered from the
> cache, then the incremental performance benefit in reducing the
> initial cache miss by 100ms is close to zero; the performance
> benefit in serving a (topological) region that otherwise can't get
> an answer is enormous, however.
Exactly*. CDNs are optimizing for more than just availability, and
thus anycast is not the (only) answer for them.
* I actually define availability and performance as separate things,
but it's clear we agree on the central point.
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