Content Cache

1. Slashdotting
 : the name stems from the huge influx of web traffic that would result from the technology news site Slashdot linking to websites
 - This overloads the smaller site, causing it to slow down or even temporarily become unavailable

2. Cache
 - the temporary storage of frequently accessed data stored for rapid access
 (+) reduces access time/latency for clients
 (+) reduces bandwidth usage
 (+) reduces load on a server
 - HTTP cache-control headers
  * Freshness: how long the cached copy stays "fresh" without revisiting the origin server
  * Validation: compare the cached copy to the origin document after it stops being "fresh"

 - Browser cache: cache for a single user / application
 - Proxy cache: cache located close to the clients
  e.g. University or Internet Service Provider
  * decreases external bandwidth usage
  * decreases network latency
 - Reverse proxy cache: cache proxy located closer to the origin web server
  * deployed by a Web hosting ISP
  * decreases load on the Web service (database)

http://searchstorage.techtarget.com/definition/cache

3. Content Distribution Networks (CDN)
 - Business requirement: stream video content to hundreds of thousands of simultaneous users
 - Obvious Web Solution: single, large "mega-server"
  => But, this solution doesn't work in practice
  => Working Web solution: store / serve many copies of videos at multiple geographically distributed sites
 - CDN Cluster selection strategy: how does CDN DNS select "good" CDN node to stream to client
  * pick CDN node geographically closest to client
  * pick CDN node with shortest delay to client
  * let client decide - give client a list of serveral CDN servers

http://searchaws.techtarget.com/definition/content-delivery-network-CDN

4. Streaming multimedia: DASH
 - DASH: Dynamic, Adaptive Streaming over HTTP
 - manifest file: provides URLs for different chunks by server
 - "intelligence" at client: client determines
  * when to request chunk => buffer starvation or overflow does not occur
  * what encoding rate to request => higher quality when more bandwidth available)
  * where to request chunk => can request from URL server that is "close" to client or has high available bandwidth

http://www.streamingmedia.com/Articles/Editorial/What-Is-.../What-is-MPEG-DASH-79041.aspx