I see. I asked because I recently listened to FLOSS Weekly's "Apache Traffic Server" episode featuring some Yahoos who were involved with it from its beginnings, and which is apparently used heavily within the Yahoo infrastructure.

http://twit.cachefly.net/floss0179.mp3

"We talk about the Apache Traffic Server, a proxy server that you probably don't realize you are already using.

Guests: Leif Hedstrom and Bryan Call"