How Comcast built a CDN using Traffic Server
At the 2013 Content Delivery Summit, Jan van Doorn gave a really interesting talk about how Comcast built an open source content delivery network with Apache Traffic Server at its core. Both the video of the talk and the slides are online.
In the talk, Jan covers the major parts of the Comcast CDN: the cache, configuration management, content routing and utilization monitoring. This is a great overview for anyone who is interested in building a CDN. There's enough open source out there that this should be practical for almost any organization.
The static tiered caching support that Comcast developed for this project landed in the Traffic Server 3.3.4 release, so you can experiment with it today.