Mysteries of a CDN Explained

Operations and Culture
Location: King's Suite Level: Intermediate
Average rating: ***..
(3.85, 13 ratings)

Content Delivery Networks are generally treated like a black box; some handwaving happens and suddenly things are expected to go faster from around the world. Time to reveal how a CDN actually works. At it’s core it is a distributed system operating under the worst possible conditions — long distances, high latency, and unreliable links that you don’t control. In addition you have to deal with a large amount of clients who are prone to misbehaviors, servers that aren’t standards compliant and settings that defeat the purpose of the caches.

The talk will cover both how to use a CDN and how a CDN is implemented, topics include:

  • How does the user get to the closest POP and what can go wrong
  • How content is fetched from origin and determined what can be cached
  • How does cache-control really work?
  • Far more about the Vary header than you ever wanted to know (why Vary: User-Agent, Cookie, Referer is not helpful)
  • Shielding servers and cache-hiearchys
  • Storage subsystems, cache-eviction and expiry.
  • TCP optimizations (kernel optimizations)
  • How config deployment works over unreliable networks
  • How purging works
  • Clever things you can do with purging.
  • Monitoring a CDN
  • How it is to live in fear of cascading failure.
Photo of Artur Bergman

Artur Bergman



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Picture of Kristian Sköld
Kristian Sköld
8/10/2012 12:24 BST

Sadly enough missed the session, but was told it was extremely interesting. Are the slides available somewhere?


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