PWG> Date: Tue, 3 May 2005 21:58:37 -0400 PWG> From: Patrick W. Gilmore PWG> Just to make life fun, there is the whole "anycast a bunch of name PWG> servers, each with different zone files pointing at local HTTP PWG> servers". Since the "anycast" portion is over UDP, it avoids a lot PWG> of the problems (real or otherwise) mentioned here, and the HTTP is PWG> still unicast but distributed and can be made resilient to failure. Actually, it's not because the anycast portion is over UDP _per se_. Someone hits an anycasted [Akamai] DNS server, which then transfers the session to a unicast IP address c/o DNS. Once the data is flowing via unicast, there's no further chance of transferring the session to another anycast box. DNS --> <whatever> is a quick-and-dirty way of accomplishing the session transfer once and for all without requiring additional protocol intelligence. It's also visible to the world, as opposed to behind-the-scenes session transfer. PWG> Of course, the DNS backend is then .. uh .. "de-coherent"? :-) But Comparing anycasted DNS service with CDNs is about as valid as comparing TCP with BGP. They serve different purposes at different levels, and one relies on the other. PWG> it works, and works well, in many currently operational configurations. Indeed. One could move beyond CDNs and cite many corporate WANs as examples of working configurations that lack coherent DNS. Unicast nameservers can lack coherency. As several others have said, anycast and coherency are orthogonal. PWG> Does PPLB (or anything else) break this? I'm certain I could find PWG> things that would break this if I looked hard enough. But as I've The trick is finding something that breaks your config without affecting "typical" ones. PWG> said many times, reality trumps NANOG posts. Since this is a PWG> _working_ configuration today, I would say that disproves any claims PWG> that it cannot or will not work. I'd not go so far as to say "disproves", but it shifts the burden of proof. Eddy -- Everquick Internet - http://www.everquick.net/ A division of Brotsman & Dreger, Inc. - http://www.brotsman.com/ Bandwidth, consulting, e-commerce, hosting, and network building Phone: +1 785 865 5885 Lawrence and [inter]national Phone: +1 316 794 8922 Wichita ________________________________________________________________________ DO NOT send mail to the following addresses: davidc@brics.com -*- jfconmaapaq@intc.net -*- sam@everquick.net Sending mail to spambait addresses is a great way to get blocked. Ditto for broken OOO autoresponders and foolish AV software backscatter.