TCP/IP Model

There are 7 layers in OSI Model.But in TCP/IP model there are only 4 layers.

•            Application Layer.
•            Transport Layer.          
•            Internet Layer.
•            Network Access Layer.

     Each layer of the TCP/IP has a particular function to perform and each layer is completely separate from the layers next to it.The communication process that takes place,at it's simplest between two computers,is that the data moves from layer 4 to 3 to 2 then to 1 and the information sent at the system and moves from 1 to 2 to 3 then finally to 4.

Application Layer.

     The Application layer concerned with providing network services to Applications.There are many application network processes and protocols that work at this layer including HTTP,SMTP and FTP.
       At this layer sockets and port numbers are used to differentiate the path and sessions which applications operate.Most application layer protocols,specially on the server side ,have specially allocated port numbers.Eg:HTTP = 80;SMTP = 25;FTP = 20.

Transport Layer.

      Transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the internet protocol suite .The details of implementation and semantics of the Transport layer of the TCP/IP model which is the foundation of the internet.
The best known transport protocol of TCP/IP is the Transmission Control Protocol and lent it's name to the title of the entire suite.TCP is the more complex protocol due to it's stateful design incorparating reliable transmission and data stream services.

The Internet Layer.

        The internet layer is a group of inter-networking methods,protocols and specifications in the internet protocol suite.That we used to transport datagrams from the originating host across network boundaries.
       Internet-layer protocols use IP-base packets.The internet layer does not include the protocols that define communication between local network nodes which fulfill the purpose of maintaining link states between the local nodes.

Network Access Layer.  

              The Network Access Layer is in the TCP/IP model at which data is transmitted and received across the physical network.
           Several protocols are serve various functions at the network access layer,including

•             Ethernet.
•             Wireless 802.11A,802.11B.
•             FDDI.
•             ATM.