02-HTTP.pdf - HTTP 2019\/20 COMP3322B Modern Technologies on WWW Contents \u2022 HTTP \u2022 Request Response \u2022 Proxy \u2022 Cookies \u2022 Quick Practice 2 Core

02-HTTP.pdf - HTTP 2019/20 COMP3322B Modern Technologies...

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HTTP 2019/20 COMP3322B Modern Technologies on WWW
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Contents HTTP Request & Response Proxy Cookies Quick Practice 2
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Core Features of the Web 1. A URL to uniquely identify a resource on the WWW. 2. At two ends, there are two programs interacting by means of the HTTP protocol , which is one form of client-server communication . The browser program which makes HTTP requests from URLs and that can display the HTML it receives. The web server software program that responds to HTTP requests. 3. The HTTP protocol to describe how requests and responses operate. 4. HTML and CSS to publish documents. 3
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HyperText Transfer Protocol (H T T P) HTTP is the foundation of data communication for the WWW. It is an application layer protocol that is sent over TCP . The protocol specifies format and meaning of messages exchanged between clients and servers. Each message has control information and message content presented in plaintext format , but it supports transmission of arbitrary binary data. Can download or upload data. 4
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HyperText Transfer Protocol (H T T P) It follows a classical client-server communication model: The client (a web browser) first initiates a TCP connection to the Web server. After that, it sends a request to the connected server. Then it waits for the response from the server. connect accept HTTP request HTTP response Browser Web Server 5
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Stateless Protocol HTTP is a stateless protocol. This means that each request is independent the system does not have memory to store the relationship between two requests every request is considered as a new request without knowledge of previous activities . Server does not maintain information about the access history of the clients. In the past, all web pages were static pages; this makes error recovery really simple. This creates difficulty for users attempting to interact with certain pages coherently, for example, using e-commerce shopping carts. 6
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Evolution of HTTP HTTP/0.9 1991 HTTP/1.0 1996 HTTP/1.1 1997 HTTP/2 2015 HTTP/3 is coming 7
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HTTP/1.0 HTTP/0.9 was called the one-line protocol and only supported one type of request: the GET request. HTTP headers were introduced in HTTP/1.0 New functionality can even be introduced by adding a new header. Made it easy to extend and experiment with new features. Added the status code info in the response messages. HTTP/1.0 has one major issue: A new TCP connection is opened for each request/response exchange. This affects the communication performance. connect accept request 1 response 1 Browser Web Server connect accept request 2 response 2 8
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HTTP/1.1 HTTP/1.1 is still widely used at the moment. To improve performance: It introduced the concept of reusing the TCP connection (aka Persistent Connection ) for multiple request/response exchanges.
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  • Fall '13
  • Dr.L.Y.Wei
  • World Wide Web, Web server, Web browser, Hypertext Transfer Protocol

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