Application Layer

  The application  layer enables the user whether human  or software  to access the  network. It  provides  user interfaces and support for services such as  electronic  mail, fire  access and transfer access to systems resources surfing the world wide  web and  network management. In this  part we briefly discuss some   applications  that are  designed  as a client server pair in the internet.  the client  sends  a request  for  a service to the  server the server responds  to the client.

In  this chapter  we will briefly  the key  application layer  concepts including application layer protocol clients  and servers.   Processes sockets and transport layer  interface and full explanation of several network applications in detail including the web e mail  DNS ( Domain  Name Server) and P2P ( point to point) file sharing.