DNS Anycast as traffic optimizer?

Wed Sep 1 22:59:35 UTC 2004

      On Wed, 1 Sep 2004, James wrote:
    >> Hmm, why not anycast the service/application ips? Having
    >> inconsistent DNS info seems like a problem waiting to bite your
    >> behind.
    > Which begs the question.. is anyone doing this right now?

Yes, lots of people.  Akamai is the largest provider of services based on
inconsistent DNS that I know of, and they've been doing it for quite a
while.  They were by no means a pioneer.  Many others before them, they
might just be one you've heard of.

    > I've been wondering about the potential issues wrt anycasting tcp
    > applications. TCP sessions would be affected negatively during a
    > route change.

Yup, which happens about one hundredth as often as TCP sessions being
dropped for other reasons, so it's not worth worrying about.  You'll never
measure it, unless your network is already too unstable to carry TCP flows
anyway.  This is also ancient history.  I and I assume plenty of other
people were doing this with long-lived FTP sessions prior to the advent of
the World Wide Web.  This is the objection clever people who don't
actually bother to try it normally come up with, after they've thought
about it for a few (but fewer than, say, ten) minutes.

                                -Bill