The Application LayerLIMANI BHAVIK & SURANI SAUNAK (IMPERIAL INFOSYS)

Limani B

havik & S

urani Saunak (Im

perial Infosys)1

Topic to be discussed………

HTTP ( Hypertext Transfer Protocol )

Limani B

havik & S

urani Saunak (Im

perial Infosys)2

Why Application Layer is used?

The Application Layer is used to provide reliable transport over the internet, but they do

not do real work for user.

For that, it will require some protocol to allow the application to function.

That protocol is HTTP(Hypertext Transfer Protocol).

Limani B

havik & S

urani Saunak (Im

perial Infosys)3

Hypertext Transfer Protocol

HTTP ( Hypertext Transfer Protocol ) is the set of rules for transferring files ( text, graphic images, sound, video, and other multimedia files ) on the World Wide Web.

HTTP is an application protocol that runs on top of the TCP/IP suite of protocols .

HTTP is a transaction-oriented client/server protocol

Limani B

havik & S

urani Saunak (Im

perial Infosys)4

Count….

It means, It is an TCP/IP based communication protocol which is used to deliver virtually all files and other data, collectively called resources, on the World Wide Web.

These resources could be HTML files, image files, query results, or anything else.

The latest version of HTTP is HTTP 1.1.

Limani B

havik & S

urani Saunak (Im

perial Infosys)5

Count….

HTTP is a "stateless" protocol, each transaction is treated independently.

Another important feature of HTTP is flexibility in the formats that it can handle.

When a client issues a request to a server, it may include a prioritized list of formats that it can handle, and the server replies with the appropriate format.

Limani B

havik & S

urani Saunak (Im

perial Infosys)6

There are three important things about HTTP……

HTTP is connectionless.

HTTP is media independent.

HTTP is stateless.

Limani B

havik & S

urani Saunak (Im

perial Infosys)7

HTTP is connectionless…..

After a request is made, the client disconnects from the server and waits for a response. The server must re-establish the connection after it process the request.

Limani B

havik & S

urani Saunak (Im

perial Infosys)8

HTTP is media independent….

Any type of data can be sent by HTTP as long as both the client and server know how to handle the data content. How content is handled is determined by the MIME specification.

Limani B

havik & S

urani Saunak (Im

perial Infosys)9

HTTP is stateless…….

This is a direct result of HTTP's being connectionless. The server and client are aware of each other only during a request. Afterwards, each forgets the other. For this reason neither the client nor the browser can retain information between different request across the web pages.

Limani B

havik & S

urani Saunak (Im

perial Infosys)10

Following diagram shows where HTTP protocol fits in the communication.

Limani B

havik & S

urani Saunak (Im

perial Infosys)11

HTTP Methods

The GET Method

The HEAD Method

The POST Method

Limani B

havik & S

urani Saunak (Im

perial Infosys)12

The GET Method

The GET method means retrieve whatever information (in the form of an entity) is identified by the Request-URI. If the Request-URI refers to a data-producing process, it is the produced data which shall be returned as the entity in the response and not the source text of the process, unless that text happens to be the output of the process.

Limani B

havik & S

urani Saunak (Im

perial Infosys)13

Count…….

A conditional GET method requests that the identified resource be transferred only if it has been modified since the date given by the If-Modified-Since header. The conditional GET method is intended to reduce network usage by allowing cached entities to be refreshed without requiring multiple requests or transferring unnecessary data.

Limani B

havik & S

urani Saunak (Im

perial Infosys)14

The HEAD Method

A HEAD request is just like a GET request, except it asks the server to return the response headers only, and not the actual resource (i.e. no message body). This is useful to check characteristics of a resource without actually downloading it, thus saving bandwidth. Use HEAD when you don't actually need a file's contents.

Limani B

havik & S

urani Saunak (Im

perial Infosys)15

The POST Method

A POST request is used to send data to the server to be processed in some way, like by a CGI script.

The most common use of POST, by far, is to submit HTML form data to CGI scripts.

Limani B

havik & S

urani Saunak (Im

perial Infosys)16

Thanks……..Lim

ani Bhavik &

Surani S

aunak (Imperial Infosys)

17