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

Learn: In this article, learn about TCP/IP model and the functions performed by the different layers of the model.
Submitted by Abhishek Jain, on August 05, 2017

The TCP/IP (Transmission control protocol / Internet Protocol) model was initially developed by US Defense Advanced Research Projects Agency (DARPA). This model is also known as the Internet Reference model or DoD.

It consists of four layers, namely: Application layer, Transport layer, Network layer, and Physical layer.

Figure: shows the four layers of TCP/IP model

tcp/ip model

The Physical layer in the TCP/IP model is responsible for interacting with the medium of transmission of data, whereas the application layer helps in interacting with the users. The four layers of TCP/IP model and the functions performed by these layers are as follows:

1) Application Layer

Application layer is the topmost layer of the model. The application layer is responsible for managing all the user interface requirements. Many of the protocols, such as Telnet, FTP, SMTP, DNS, NFS, LPD, SNMP and DHCP work on this layers.

2) Transport Layer

The transport layer is responsible for the delivery of packets or datagram’s. It also hides the packet routing details from the upper layer, i.e., the application layer. In addition, the transport layer allows detection and correction of errors and helps to achieve end-to-end communication between devices. The transport layer connects the application layer to the network layer through two protocols, namely, TCP and UDP.

3) Network Layer

The network layer is also known as Internetworking layer or IP layer. It contains three protocols that perform different functions. The three protocols of Network layer are as follows:

  1. Internet Protocol (IP):
    IP is a connectionless protocol that is responsible for the delivery of packets. The IP protocol contains all the address and control information for each transmitted packet.
  2. Internet Control Message Protocol (ICMP):
    The ICMP protocol is responsible for reporting errors, sending error messages and controlling the flow of packets. It is more reliable than the IP as it is capable of determining errors during data transmission.
  3. Address Resolution Protocol (ARP):
    It is responsible for determining the Media Access Control (MAC) address corresponding to an IP address. It sends an ARP request on the network for a particular IP address and the device, which identifies the IP address as its own, returns an ARP reply along with its MAC address.

4) Physical Layer

The physical layer is responsible for collecting packets so that the frames, which are transmitted on the network, can be formed. It performs all the functions required to transmit the data on the network and determines the ways for accessing the medium through which data will be transmitted. This layer does not contain any protocols but instead of protocols, it contains some standards such as RS-232C, V.35 and IEEE 802.3.


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