On May 3, 2005, at 7:38 PM, Edward B. Dreger wrote:
PWG> Date: Tue, 3 May 2005 18:03:12 -0400 PWG> From: Patrick W. Gilmore
PWG> NB [translation, "operational content"]: Akamai does not use any PWG> anycast for HTTP. I am not at all certain why Paul is telling us PWG> this is a bad idea, since we don't do it. Then again, we might in PWG> the future, I am not privy to every decision in the company. (No, PWG> that is not a "hint", I really do not think we will do anycast HTTP PWG> for content delivery, but I also really do not know everything we PWG> will do in the future.)
One also should distinguish between TCP _to_ an anycasted address and TCP _from_ an anycasted address. The latter is trickier, as asymmetric routing increases the chances that the session will need to be transferred to another pod:
Just to make life fun, there is the whole "anycast a bunch of name servers, each with different zone files pointing at local HTTP servers". Since the "anycast" portion is over UDP, it avoids a lot of the problems (real or otherwise) mentioned here, and the HTTP is still unicast but distributed and can be made resilient to failure. Of course, the DNS backend is then .. uh .. "de-coherent"? :-) But it works, and works well, in many currently operational configurations. Does PPLB (or anything else) break this? I'm certain I could find things that would break this if I looked hard enough. But as I've said many times, reality trumps NANOG posts. Since this is a _working_ configuration today, I would say that disproves any claims that it cannot or will not work. -- TTFN, patrick