Application layer protocol.

  • The application layer is the topmost layer of the protocol hierarchy.
  • It is the layer where actual communication is initiated. It uses the services of the transport layer, the network layer, the data link layer, and the physical layer to transfer data to a remote host.
  • The Application Layer contains a variety of protocols that are commonly needed by users. One widely-used application protocol is HTTP(HyperText Transfer Protocol), which is the basis for the World Wide Web.
  • In http ,When a browser wants a web page, it sends the name of the page it wants to the server using HTTP. The server then sends the page back. 
  •  Function of application layer protocol. 
  1. Mail Services: This layer provides the basis for E-mail forwarding and storage.
  2. Network Virtual Terminal: It allows a user to log on to a remote host. application creates software emulation of a terminal at the remote host.
  3. Directory Services: This layer provides access for global information about various services.File Transfer, Access and Management (FTAM): It is a standard mechanism to access files and manages it.      
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