Hypertext transfer protocol (http)

what it is, versions. how it works and what methods Http use by which version of it.

1. Hypertext Transfer Protocol (HTTP) Shimona agarwal

2. Introduction HTTP was introduced by Tim Berners-Lee at CERN. HTTP functions as a request–response protocol in the client–server computing model . The client submits an HTTP request message to the server. The server, which provides resources such as HTML files and other content, or performs other functions on behalf of the client, returns a response message to the client. The response contains completion status information about the request and may also contain requested content in its message body . HTTP is an application layer protocol, which commonly uses TCP (transmission control protocol).

3. Connectivity HTTP does not handle network connectivity or how information is transmitted. DNS protocol helps client to connect with requested server. Application layer does important work like web browsing or file transferring. The server respond to client request without knowing anything about Client. Each request requires separate TCP network.

4. Request methods Http/1.0 (the original version) contained 3 methods – GET POST HEAD

5. Request methods GET The GET method requests a representation of the specified resource. Requests using GET should only retrieve data and should have no other effect. POST The POST method requests that the server accept the entity enclosed in the request as a new subordinate of the web resource identified by the URI. HEAD The HEAD method asks for a response identical to that of a GET request, but without the response body. This is useful for retrieving meta-information written in response headers, without having to transport the entire content.

6. Request methods HTTP/1.1 (revision of 1.0) added 5 new methods- PUT DELETE TRACE OPTION CONNECT

7. Request methods PUT The PUT method requests that the enclosed entity be stored under the supplied URI . If the URI refers to an already existing resource then the server can create the resource with that URI. [ DELETE The DELETE method deletes the specified resource. TRACE The TRACE method echoes the received request so that a client can see what changes or additions have been made by intermediate servers.

8. Request methods OPTION This can be used to check the functionality of a web server by requesting '*' instead of a specific resource. CONNECT The CONNECT method converts the request connection to a transparent TCP/IP .

9. Persistent Connection HTTP persistent connection , also called HTTP keep-alive , or HTTP connection reuse , is the idea of using a single TCP connection to send and receive multiple HTTP requests /responses. Persistent connections stay open across transactions, until either the client or the server decides to close them.

10. Advantages & Disadvantages Advantages Lower CPU and memory usage (because fewer connections are open simultaneously). Enables HTTP pipelining of requests and responses. Reduced network congestion (fewer TCP connections ). Reduced latency in subsequent requests (no handshaking ). Errors can be reported without the penalty of closing the TCP connection. Disadvantages If the client does not close the connection when all of the data it needs has been received, then the server will be unavailable for other clients.

11. Non- Persistent Connection HTTP non persistent Connection is the idea of using a multiple TCP connection to send and receive each HTTP requests /responses. Each object transfer suffers from low start. It is similar to being stateless.