Persistent and No persistent Connections

HTTP can use  both  persistent  and non persistent connection. By defaults  uses persistent  connections.

Persistent Connections

HTTP persistent  connection also called HTTP keep alive or HTTP connection reuses is the idea  of using the same TCP connection to send and receive multiple HTTP  request / responses  as opposed  to opening a new one for every single  request/ response  pair using persistent  connections  is very  important  for improving HTTP performance.

HTTP  specifies  a persistent connection by  default. With persistent  connection  the server leaves the TCP connection open after sending a response. Subsequent  request an denture web page can be sent over a single persistent TCP connection moreover multiple web pages residing on the same server can be sent  from the server to  same  client over a single persistent TCP connection. The HTTP server close  a connection  when  it isn't  used for  certain  time ( a configurable time out interval).

These  are several advantages of using  persistent  connections including:

a.Network  friendly  less network  traffic due  to fewer setting up  and tearing down of  TCP connections.

b.Reduced latency on subsequent  request. Due to avoidance of initial TCP handshake.

c.Long lasting  connection allowing TCP sufficient time to determine  the congestion  state  of the network  thus to  react appropriately.

There  are two  versions  of persistent  connections.