1. Web Latency Reduction Via Client-side Prefetching Avinoam N. Eden; Brian W. Joh; Trevor Mudge Electrical Engineering and Conputer Science Department The University of Michigan Miketien Miketien@syslab.cse.yzu.edu.tw

2. Outline 1.Environment 2.Latency Reduction Techniques 3.Other Schemes 4.Client-side Prefetching 5.Simulation and Result

3. Http procotol 1.static object:the server transfer it back to the proxy server, which deliver it to the client.(ex:HTML,JPEG,GIF,Applet) 2.dynamic object: the origin server first construct it, and only then sends it to the proxy. It might require querying a database server. Classification of latency 1.Internal — proxy server  client 2.external — server  proxy 3.object creation-- ex:querying database,processing a script 1.Environment

4. Environment(cont.)

5. Three most common configuration in use on the WWW

6. 2.Latency Reduction Techniques Caching 1.proxy — physically located closer to the clients and has fewer clients than the content provider ex: BACK button (browser) might register a request at the proxy server. ad:reduce the external latency and object creation latency disad: the number of dynamically web pages constructed increases, the benefit of proxy server will diminish. 2.client — disad:does not apply the object brought by other clients ad:reduce the internal latency 3.server-- ad: reduce only the object creation latency disad: incur large object creation latency

7. Latency Reduction Techniques(cont.) Prefetching 1.proxy side — ad:reduction latency up to 50% disad:increasing the amount of traffic on the network 2.server side — If there is knowledge that a web page will be requested in the near future, the server can prefetch it.This web page will be requested without any object creation latency.

8. 3.Other Schemes Dynamic Object Solution: 1.Delta encoding—only send the portion of the binary file, when changed since the last version stored on the proxy side. 2.HTML Pre-Processing(HPP)—HTML extension.While the static portion can be cached, the dynamic portion is generated for each request. disad:They require cooperation between the proxy and the server.

9. 4.Client-side Prefetching By prefetching from the client side we target all portion of the latency; by having the user decide what and when to prefetch, we eliminate any extra network traffic usually created by prefetching. Shch mechanism can be implemented as part of current web browsers or as a plug-in for a browser. And without cooperation.

10. Client-side Prefetching(cont.)

11. 5.Simulation and Result Three Heuristic to Prefetch 1.Vanilla — Assumes that a user can always prefetch the next web page 2.Same-server — Assumes that a user can only prefetch a web page if the web page resides on the same server as the current page. 3.Assumes that a web page can only be prefetched if in a tree structure, and it is a leaf of this tree. If we do not know whether the web page is tree structure or not, we construct it. ex: a,b,a,c,a  b,c,d are leaves

12. Simulation and Result(cont.)

15. The average latency per page was 12.53 seconds without prefetching. Using the client-side prefetching was able to reduce it to 4.32 seconds.(1/3)