1. 7/9/2001 Edward Chow Content Switch 1 Clients Content Delivery Network (CDN) Host Server Mind Spring PSINet Sprint GloobixQWest @Home UUnet Huge Requests Server Crash Slow Response Clients

2. 7/9/2001 Edward Chow Content Switch 2 Content Delivery Problems http://www.akamai.com

3. 7/9/2001 Edward Chow Content Switch 3 Use Client Cache/ Client Side Cache Server Host Server Mind Spring PSINet Sprint Gloobix @Home UUnet Fewer Requests Clients Client Cache Client Side Cache Server QWest Fast Response

4. 7/9/2001 Edward Chow Content Switch 4 Use Mirror Sites Host Server Mind Spring PSINet Sprint GloobixQWest @Home UUnet Fewer Requests Server Fast Response Clients Mirror Site Need improvement by guiding the selection of mirror servers with server load/network bandwidth measurement

5. 7/9/2001 Edward Chow Content Switch 5 Edge Network Cache Servers Host Server Mind Spring PSINet Sprint GloobixQWest @Home UUnet Fewer Requests Server Fast Response Clients Client Cache Mirror Site Edge Network Cache Server Cache Server Cache Server Cache Server Cache Server Client Side Cache Server

6. 7/9/2001 Edward Chow Content Switch 6 Content Delivery Problem Cache Location Problem: Where to put cache servers? How many are needed? When/where/how to push/delivery the content? How about dynamic content?

7. 7/9/2001 Edward Chow Content Switch 7 Akamai Edge Delivery Service Peering Bottleneck Problem: Access traffic evenly spread over 7400+ networks (no one over 5%; most << 1%)  Need to put edge servers in many networks. 11/2000, 4 billion bits/day for 2800 sites. Source Http://www.akamai.com Date# of Edge Servers # of Networks# of Countries 11/2000600033554 6/2001970065056

8. 7/9/2001 Edward Chow Content Switch 8 Caching Dynamic Content at Web Proxies Active Cache Project : [PeiCao 98] Univ. Wisconsin –Cache Java applet to be executed at proxies –Choice of passing to server, delivery cached copy, or generate dynamically. Edge Side Include (ESI): –XML tag to specify ESI fragment in a web page. –Each ESI fragment can have different cache requirements

9. 7/9/2001 Edward Chow Content Switch 9 Edge Side Include Example http://www.esi.org/ click here - - > http://www.myxyz.com/news/top.htmlwww.myxyz.com

10. 7/9/2001 Edward Chow Content Switch 10 Solution to First Mile Problem First Mile Problem: Hugh requests at web site of CDN High Bandwidth Connection Caching –End System Cache Client Cache Client Site Proxy Cache Server Mirror Site Caches –Cache Servers in Internet Hierarchical Cache Servers, e.g., Squid/Harvest/Adaptive Web Edge Servers of Akamai Faster Server/Server Farm (Server Side Caching+Cluster) Layer4 Load balancer+Real Servers Content Switch+Real Servers Distributed Packet Rewrite

11. 7/9/2001 Edward Chow Content Switch 11 Load Balancer or Content Switch Real Server Web Server Cluster Load balancer can run at Application Level — Reverse Proxy Kernel level — Linux Virtual Server Load balancer can distribute requests based on Layer 3-4 info — fixe field/fast hash Layer 3-7 info — var. length/slow parsing Real Server