计算机网络系列（8）之应用场景Web acceleration

1. Web acceleration
Web acceleration is to speed up web access: fast processing + fast I/O + fast communication.

1.1. Local caching
The local browser gets a web page from a remote web server and store a copy in the local cache.

1.2. Web caching
In web caching, cached web page is shared by multiple users, so web caching is more effective for sharing. e.g., Proxy.

1.3. Prefetching
Prefetch several or all links of current web page.

1.4. HTTP compression
Many web documents contain ASCII texts which can be significantly compressed.

2. Questions
Q1: Consider proxy for web caching
case1: If a proxy is not fast enough, what is the consequence?
The proxy will be a bottleneck, resulting in slower access.

case2: How would you set up a fast proxy?
Network speed.
CPU speed.
I/O speed.

Q2: Discuss whether prefetching is an effective web acceleration method?
It is a selfish method. Not good for all users, but good for individual.

Q3: A browser sends an HTTP request to a web server where this request carries the following information:
- The browser uses HTTP 1.1. to request a file with pathname /IT_baby.html
- The web server is www.abc.com
- The browser supports HTTP compression and gzip.
The web sender sends an HTTP reply to the browser where this reply carries the following information:
- The sever uses HTTP 1.1 to provide the requested file to the browser.
- The server uses gzip to compress the requested file.
- The compressed file consists of 3000 bytes.
Draw a diagram to show the sequence of message exchanges and the content of these messages.

2. 总结
重点1：网络服务器的加速，主要有四个途径，分别问local PC的caching，web server的caching, 文件预取，以及压缩。