TCP/IP Protocols

Dr. Sharon Hall Perkins

ApplicationsWorld Wide Web(HTTP)

Presented by

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

An Introduction To The WWW

Early history The expansion Difference between the Web and Internet Future

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

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.

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

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 torequest the web page from server

Server sends a copy of the page requested

Error Message

Page Found?

Error Message

No

No

Yes

Yes

Persistent Connections

What is a persistent connection? How is it established? Advantage

reduced overhead Disadvantage

Identification required for beginning and end

Data Length

Why is data length necessary?

Creation of Dynamic Web Pages

Present technology to help in the maintenance of dynamic Web Pages.

Length Encoding & Headers What representation does a server use to

send length information?

Negotiation Characteristics of negotiation capabilities:

About the connection Representation Content Control

Two types are: Server-driven Agent-driven

Support For Proxy Servers

What is the importance of Proxy Servers in the Web Architecture?

How does HTTP support the mechanism of Proxy Servers?

Caching

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