Akamai hostnames do not map to specific customers; that information is part of the metadata that follows the hostname. Obviously, the customer ID and the source server must match or else no cachey cachey. :) The number in the hostname figures into Akamai's load balancing algorithm, IIRC. What actually happens is a type of "mapping" that tries to nail down the network location of the source IP that's on the DNS query, and returns the IP of the cache server that's hopefully closest to that source IP. Most of the time this works well, although it's not extremely precise; the most obvious caveat is that the source IP recorded is that of the DNS resolver, not the HTTP client. If your workstation on UUNet in Washington is configured to query a name server that's on, say, Level3's network in Seattle, Akamai's servers will use the latter location for this evaluation, with the obvious sub-optimal result. But the majority of the time, it delivers the IP of a machine that's closer to the end user than the customer's server. And the customer gets the benefit of reduced outbound traffic and server load in any case. It's particularly effective at my office, as my workstation is 4ms away from the Akamai server in our local data center. But my home DSL service, for which the other end of the PVC lives at the same site, is served by an Akamai server in Philadelphia. Go figure. -Chris On Sun, Oct 07, 2001 at 01:14:24AM -0400, Vivien M. wrote:
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Valdis.Kletnieks@vt.edu Sent: October 7, 2001 1:05 AM To: Mary Grace Cc: nanog@merit.edu Subject: Re: dns based loadbalancing/failover
On Sat, 06 Oct 2001 16:44:57 EDT, Mary Grace said:
Hrmm, no, that is called "Akamai", isn't it? :)
There's an Akamai across the hall from my office, and the way it was explained to *me* was that the DNS always returns the same IP address for a given Akamai'zed page (so the URLs in the HTML are consistent), but routing games are used to direct the packets to the appropriate server. In other words, it's one IP that points to disparate machines.
They lied to you (I don't remember who a96.g.akamai is; it's some well-known Akamai customer, maybe CNN): vivienm@quartz:~$ nslookup a96.g.akamai.net Server: quartz.bos.dyndns.org Address: 66.37.218.198
Non-authoritative answer: Name: a96.g.akamai.net Addresses: 216.32.119.10, 216.32.119.74
vivienm@quartz:~$ nslookup a96.g.akamai.net amethyst.ith.dyndns.org Server: amethyst.ith.dyndns.org Address: 216.7.11.130
Non-authoritative answer: Name: a96.g.akamai.net Addresses: 207.127.111.70, 207.127.111.73
vivienm@nickel:~$ nslookup a96.g.akamai.net Server: zinc.fmt.dyndns.org Address: 64.71.191.27
Non-authoritative answer: Name: a96.g.akamai.net Addresses: 64.21.49.15, 64.21.49.36
vivienm@lapis:~$ nslookup a96.g.akamai.net Server: 212.100.224.10 Address: 212.100.224.10#53
Name: a96.g.akamai.net Address: 64.124.157.126 Name: a96.g.akamai.net Address: 64.124.157.91
[from my home box]
vivienm@deep:~$ nslookup a96.g.akamai.net Server: proxy1.slnt1.on.wave.home.com Address: 24.112.33.4
Name: a96.g.akamai.net Addresses: 65.163.234.8, 65.163.234.24
[from one of your DNS servers] vivienm@quartz:~$ nslookup a96.g.akamai.net milo.cns.vt.edu Server: milo.cns.vt.edu Address: 198.82.247.98
Name: a96.g.akamai.net Addresses: 198.82.164.48, 198.82.164.40
I'm sure I could keep going if you really wanted, but I think that's enough to prove the point...
Vivien
-- Vivien M. vivienm@dyndns.org Assistant System Administrator Dynamic DNS Network Services http://www.dyndns.org/
-- --------------------------- Christopher A. Woodfield rekoil@semihuman.com PGP Public Key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0xB887618B