1. TCP/IP Protocols Dr. Sharon Hall Perkins Applications World Wide Web(HTTP) Presented by

2. Architectural Components Uniform Resource Locators (URL) Hypertext Transfer Protocol Persistent Connections Data Length and Program Output Length Encoding and Headers Negotiation Support for Proxy Servers Caching Topics

3. An Introduction To The WWW Early history The expansion Difference between the Web and Internet Future

4. Architectural Components The World Wide Web comprises of Web Pages Large set of documents accessible over the Internet Web Browser Application program that a user invokes to access and display the Web page Web Server Application program that provides information about a Web page

5. Uniform Resource Locators (URL) What is a URL? Http scheme of a URL http://hostname [:port]/ path [;parameters] [?query] The types of URLs Absolute URL Contains a full specification Relative URL omits the address of the server and is useful only when the server is implicitly known.

6. Hyper Text Transfer Protocol (HTTP) What is HTTP? Characteristics of HTTP Operates at Application Level Http Request/Response Stateless Bi-directional Transfer Capability Support for Caching Support for Intermediaries

7. HTTP GET Request Steps followed to retrieve a page from a Web Server. Browser extracts hostname from URL Uses DNS to map the name to an IP Address Uses the IP Address to form a TCP connection TCP Connection? Browser sends HTTP Get command to request the web page from server Server sends a copy of the page requested Error Message Page Found? Error Message No Yes

8. Persistent Connections What is a persistent connection? How is it established? Advantage reduced overhead Disadvantage Identification required for beginning and end

9. Data Length Why is data length necessary? Creation of Dynamic Web Pages Present technology to help in the maintenance of dynamic Web Pages.

10. Length Encoding & Headers What representation does a server use to send length information?

11. Negotiation Characteristics of negotiation capabilities: About the connection Representation Content Control Two types are: Server-driven Agent-driven

12. Support For Proxy Servers What is the importance of Proxy Servers in the Web Architecture? How does HTTP support the mechanism of Proxy Servers?

13. Caching Goal How long should an item be kept in cache? Caching in a server.