Outlines requirements and time allocation 2.2 What World Wide Web:HTTP(Web应用和HTTP协议) 2.2.1 A Nuts and Bolts Description 5分钟 http:hypertext transfer protocol Web's application layer protocol client/server model 222 Non-persistent and persistent connections 20分钟 server parses request,responds,and closes TCP connection 2 RTTs to fetch each object Each object transfer suffers from slow start Persistent default for HTTP/1.I on same TCP connection:server,parses request,responds,parses new request, Client sends requests for all referenced objects as soon as it receives base HTML Fewer RTTs and less slow start 2.2.3 HTTP Message Format HTTP/1.0 200 OK Date:Thu,06Aug 19981200:15 GMT Server:Apache/1.3.0 (Unix) Last-Modified:Mon,22 Jun 1998. Content-Length:6821 Content-Type text/html datadata data datadata 2.24 User-Service Interaction:Authentication and Cookies 15分钟 Authentication goal:control access to server documents stateless:client must present authorization in each request authorization:typically name,password 22.5 The Condition GET http request msg:If-modified-since:<date http response:HTTP/10,304 Not Modified 2.2.6 Web Caches user sets browser.Web accesses via web cache me:cache is ) smaller response time:cache "closer"to client decrease traffic to distant servers (重点讲解HTTP格式，引入Condition GET等内容，用启发、讨论式教学方式教学。) 复习本次课的主要内容。 5分钟 9 Outlines, requirements and time allocation 2.2 What World Wide Web: HTTP（Web 应用和 HTTP 协议） 2.2.1 A Nuts and Bolts Description http: hypertext transfer protocol Web’s application layer protocol client/server model 2.2.2 Non-persistent and persistent connections Non-persistent HTTP/1.0 server parses request, responds, and closes TCP connection 2 RTTs to fetch each object Each object transfer suffers from slow start Persistent default for HTTP/1.1 on same TCP connection: server, parses request, responds, parses new request,. Client sends requests for all referenced objects as soon as it receives base HTML. Fewer RTTs and less slow start 2.2.3 HTTP Message Format HTTP/1.0 200 OK Date: Thu, 06 Aug 1998 12:00:15 GMT Server: Apache/1.3.0 (Unix) Last-Modified: Mon, 22 Jun 1998 . Content-Length: 6821 Content-Type: text/html data data data data data . 2.2.4 User-Service Interaction: Authentication and Cookies Authentication goal: control access to server documents stateless: client must present authorization in each request authorization: typically name, password 2.2.5 The Condition GET http request msg: If-modified-since: <date> http response: HTTP/1.0, 304 Not Modified 2.2.6 Web Caches user sets browser: Web accesses via web cache client sends all http requests to web cache Assume: cache is “close” to client (e.g., in same network) smaller response time: cache “closer” to client decrease traffic to distant servers （重点讲解 HTTP 格式，引入 Condition GET 等内容，用启发、讨论式教学方式教学。） 复习本次课的主要内容。 5 分钟 20 分钟 15 分钟 5 分钟