Transmission Control Protocol/Internet Protocol (TCP/IP) Model

TCP/IP also is a layered protocol but does not use all of the OSI layers. OSI model was theoretical model and protocol-independent standard but TCP/IP is the model aroung which Network or internet is developed and it is protocol-dependent model.It is occasionally known as the Department of Defense (DoD) model, because the development of the networking model was funded by DARPA. The TCP/IP Model consists of four layers:


TCP_OSI
The Application layer provides applications the ability to access the services of the other layers and defines the protocols that applications use to exchange data. IN TCP/IP Application layer is the Combined layer of Application, Presentation & Session Layer of the OSi model. Application layer in TCP/IP also performs Encryption, Decryption along with helps on creating Sessions. Example of Application Layer Protocol are BGP, DHCP, DNS, TELNET, HTTP etc.
Host to Host layer is equivalent to Network Layer of OSI model. It provides the services for Secure data transmission from Source and Destination. ensures the reliable arrival of messages and provides error checking mechanisms and data flow controls. It provides transparent transfer of data between end systems using the services of the network. It uses 2 Services i.e TCP and UDP.
The Internet layer is responsible for addressing, packaging, and routing functions. This layer is equivalent to Network Layer of OSI Model. Internet Layer is responsible to provide best path to reach destination. The core protocols of the Internet layer are IP, ARP, ICMP, and IGMP.
Network Access layer is responsible for placing TCP/IP packets on the network medium and receiving TCP/IP packets off the network medium. TCP/IP was designed to be independent of the network access method, frame format, and medium. In this way, TCP/IP can be used to connect differing network types. These include LAN technologies such as Ethernet and Token Ring and WAN technologies such as Frame Relay. Network Access layer encompasses the Data Link and Physical layers of the OSI model.