TCP/IP Protocol Architecture and Its Layers

Communication is the process of transfer of information from one place to another. Either it could be the transmission of calls from one device to another or transfer of files from one computer to another. World wars have brought a tremendous evolution the communication electronics. Today we use digital communication methods everywhere. With the development of technology, many types of communication devices are being implemented. To establish proper and error-free communication between devices of different types and different configurations, all the devices must follow some standard protocols. One such standard protocol for communication between different devices is the TCP/IP protocol.

What is the TCP/IP Protocol?

TCP/IP protocol stands for the Transmission Control Protocol/ Internet Protocol. It was developed by the United States Department of Defence in the 1960s. It is a conceptual model that has a set of communication protocols used for the transfer of information over the internet and computer networks.


This protocol tells us how data should be addressed, stored, transferred, coded and decoded by the devices for end-to-end communication between devices. It is the main protocol of the Intenet Protocol Suite. TCP/IP provides a reliable, safe and error-free transfer of data between applications running on hosts through an Internet media.

Many popular web applications such as the World Wide Web, email, etc.. use this protocol.

TCP/IP Protocol Fundamental

TCP/IP is a layered protocol widely used in networking. To understand the working of the networking protocol let us look at an example of a simple delivery.

To send a delivery from one place to another certain tasks are involved. At first, the package should be packed and addressed. Then the delivery man takes the package from the sender to the mail dispatch room. Here the packages are sorted by address and loaded in vans and dispatched to a remote office. At the remote office, the packages are placed in a tray for the mailman. Then the mailman collects the package and delivers it to the recipient.

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The networking protocol such as TCP/IP also works in a similar fashion while sending information and data from one device to another. It has four layers that divide the tasks accordingly. They are the Application Layer, Transport Layer, Networking Layer and the Data Link layer from top to bottom. All these layers have their specific functions and they communicate with the layers above and below them when transferring data.

TCP/IP Protocol Architecture

It is a four-layered protocol stack. It helps in the interconnection of network devices over the internet. Each layer contains certain protocols that help in the functioning of the layer. The four layers of TCP/IP protocol are Application Layer, Transport Layer, Networking/Internet Layer and the Data Link/physical layer.

Data-Flow-of-TCP/IP-protocol
Data-Flow-of-TCP/IP-protocol

The application, Presentation and Session Layers of the OSI model are combined as the Application/Process Layer in TCP/IP protocol. It is the top layer of this protocol stack. This layer controls the user-interface and node-to-node communication. This layer provides the network interface, internetworking and transport functions. It sends the data to the transport layer.

The reliability, flow-control, and correction of data that is sent over the network are taken care of by the transport layer. User Datagram Protocol and the Transmission control protocol are present in the transport layer. After the transport layer, the control is given to the Internet layer.

The Internet layer is also known as the network layer. Its function is to move the data packets over the internet to the destination. Data packets can take any of the optimized routes suggested by this layer. The most important protocol -IP Protocol is present in this layer. This protocol is responsible for adding the IP addresses to the data, routing the packets, data encapsulation, formatting.

The last layer in the TCP/IP protocol stack is the Network Access Layer. It is the combination of the physical and data link layers of the OSI model. The transmission of data physically over a network between two devices is controlled by this layer. The mapping of IP addresses of the devices into physical addresses is also done at this layer.

Protocol Suite

A protocol is a set of rules that tells and directs how systems should communicate. A protocol suite is a collection of protocols that are designed to work together. The protocol suite that has only one protocol is known as a single stack protocol. But this type of protocol is very unstable and frequently requires to change the whole protocol software if any changes are made to the application.

To make the protocol usage more flexible, the layered protocol stack was proposed. This type of protocol stack consists of protocols arranged at different levels with each level performing a certain task. Each level can communicate with the levels above and below them. Here the task or the functioning of a level or layer can be changed or modified without affecting other layers.

TCP/IP is a 4 layered protocol suite. It takes the OSI model as its conceptual framework. This suite consists of various protocols arranged on four levels. It is named after its two most popular protocols -the transmission control protocol and the Internet Protocol.

The Protocols Present in the Application Layer 

 HTTP – HyperText Transfer Protocol.This protocol allows the user to access the data over the world wide web. It can be used in the hypertext environment and send data in the form of plain texts, audio, and video.

 SNMP – Simple Network Management Protocol, which manages devices over the internet.

 SMTP – Single Mail Transfer Protocol. This protocol manages the sending and receiving of emails

 DNS – Domain Name System, it maps the hostnames to the host IP address which are connected to the internet.

 TELNET – Terminal Network, to establish the connection between the local computer and the remote computer.

 FTP – File Transfer Protocol, used for transmitting of files from one computer to another.

The Protocols Present in Transport Layer

 UDP – UserDatagram Protocol. It tells the user about the presence of error. This protocol provides end-to-end transmission of data. To a data packet, this protocol adds 8 bytes of header. The header consists of four fields -Source Port address of 16 bits, Destination port address of 16 bits, a 16-bit field for indicating the total length and a checksum field of 16-bits.

The source port address gives the address of the application program that created the message. The destination port address is the address of the destination application to which the data has to be transmitted. The total length field gives information about the total number of bytes present in the datagram. The information present in the checksum field is used for error detection.

 TCP – Transmission Control Protocol. This protocol is active for the duration of the transmission of data. It from a virtual circuit between sender and receiver. At the sender side, the protocol breakdown the data in the form of small units called segments. Each segment is associated with a sequence number which helps in reordering the segments from the original message.

At the receiver end, TCP collects all the segments and reorder them according to their sequence numbers. Whenever an error is detected by the protocol it retransmits the segment. After ensuring that all the segments are transmitted and acknowledged and transmission is completed, the protocol then discards the virtual circuit.

Protocols Present in Internet Layer

IP Protocol – this is the most significant protocol of TCP/IP protocol suite. To identify the device over the internet and ti establish the internetwork routing, this protocol implements logical host addresses called the IP addresses for each host device. This protocol accepts the data from the transport layer and ensures the secure transmission of data from one device to another.

It converts the data segments into IP Datagrams. If the size of the datagram is greater than the limit provides by the next layer- the link layer, IP protocol fragments the datagram into small parts so that they can be transmitted easily through the local network. At the receiving end, these segments are rearranged to form the original message. Routers are used to send the data between devices that are connected through the distant network.

ARP – Address Resolution Protocol. This protocol finds the physical addresses from the IP addresses. The sender devices which want to know the physical address of the receiver device send an ARP request over the network. All the devices present in the networks receive this request, process it and the recipient recognizes the IP address present in the request and sends its physical address though ARP reply.

Thus all these protocols together form the TCP/IP protocol suite. Applications will choose which type of protocol to use at each layer based on the functions provided by the protocols. This protocol suite can be easily modified and is compatible with all types of Computer hardware and operating systems. It was originally designed for the UNIX operating system.

Routers and switches are examples of the networking devices used for transmission of data between devices connected through the internet. As the TCP/IP protocol takes the OSI model as a reference, which layers of the OSI model are combined as Application Layer of TCP/IP protocol?

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