Transmission Control Protocol/Internet Protocol Model

TCP/IP Model

Suppose two persons are to communicate with one another. To communicate successfully, they should be sharing a common language. Therefore, both ends should be able to understand what the other person is saying. Similarly, in computer networks, the computers should be sharing a common message format. They should know how long the message is. If one computer speaks ASCII and the other speaks Unicode, successful communication will not occur unless they are prepared to perform the translations back and forth. So, some ground rules are required to communicate successfully. In computer networks, the agreed-upon set of ground rules that make communication possible are called protocols. This TCP/IP model is set of protocols that support network communication, but what is a network and what is communication? Let suppose two computers connected by LAN Cable sharing data with the help of Network Interface Cards forms a network, and the process of sending messages from one place to another through a wired or wireless medium is called communication. The message can be a file, a voice conversation, a streaming video or anything which can be communicated in digital form. These messages are not sent as a single unit; instead, they are broken into small data units. These data units are transmitted through the network and restored at the receiver into the original message. In TCP/IP protocol suite, TCP breaks messages into small data units called segments and hands them off to IP, which deals with routing segments through the networks to their final destination. TCP module in the receiver combines the segments to form the original message. Note that TCP stands for Transmission Control Protocol and IP stands for Internet Protocol. An alternative to TCP is UDP. It stands for User Datagram Protocol. The main difference is that TCP  is highly reliable, but it is slow, whereas UDP is less reliable but generally faster. Both TCP and UDP are a part of the protocol suite.  However, due to heavy dependence on TCP, and for historical reasons, the entire set of protocols is referred to as TCP/IP. TCP/IP is a network model designed to support network communication, even if the computers are from different manufacturers. There is one more network model called the OSI model or Open System Interconnection reference model. It is primarily used for research. On the other hand, TCP/IP is a practical model developed to meet the needs of the original Internet design. As per the name, TCP/IP seems to be a set of two protocols only – TCP and IP. However, it consists of numerous protocols bundled at different layers. The topmost layer is the Application layer which generates a message. The message is passed to the lower layers at the sending node, where each layer encapsulates the message from the above layer. So, the message sent becomes larger and larger as it passes down the chain. The data unit in the data link layer is called an Ethernet frame; in the network layer, it is called an IP packet; if it is in the transport layer, it is called TCP segment in case of TCP protocol and UDP datagram in case of UDP protocol. In the application layer, it is called an application message. The peer layer removes the header at the receiving node and passes the remainder upwards layer-by-layer till the message finally reaches the application layer.  

Fig 1: TCP/IP Model

TCP/IP Model stands for the Transmission Control Protocol/Internet Protocol Model. This model is developed by the Advanced Research Project Agency Network that is known as the ARPANET.

TCP/IP Model is the model that has the four layers. And TCP/IP is the more reliable than Open System Interconnection Model. And TCP/IP model is the model that has the not very strict boundaries. This Model is the model that follow the approach of the horizontal approach. TCP/IP model is the model in which application layer is the combination of the session and presentation layers. In this model the layer of transport does not provide the assurance delivery of the user data/packets. The network layer of this model is provide the services of connection less. This Model is tough with respect to the replacement of the protocols.

Following are the four layers of the TCP/IP Model:

• Application Layer
• Transport Layer
• Internet Layer
• Link Layer

Application Layer

Application layer is the layer that is the combination of the OSI model's 5th,6th, and 7th layers. This layer is the layer that has the responsibility of the node to node communication and also control the UI specifications. Some are the protocols of this layer:

• Http that use the port number 80.
• Https that   use the port number 443.
• FTP that use the port number 20-21.
• SSH that use the port number 22.
• Telnet that use the port number 23.
• SMTP that use the port number 25.
• TFTP that use the port number 69.

Transport Layer

This layer is the layer that is responsible for the end to end communication and the error remove delivery of the user data. This layer is known as the host to host layer. Here are the two most important protocols that are below: 

TCP (Transmission Control Protocol)                                                      

• TCP is Reliable. 
• TCP is Connection Oriented.
• TCP is Slower than UDP.

UDP (User Datagram Protocol)

• UDP is Unreliable.
• UDP is Connectionless.
• UDP is Faster.

Internet Layer

Internet layer is the layer that equivalent to the network layer of the OSI model. It is responsible for the logical transmission of the data. This is the second layer of the TCP/IP model. This is also known as the network layer and the main point is that this layer is responsible for the delivery of the packets.

Open Shortest Path First is the example protocol of the internet layer and this protocol is based on the Dijkstra Algorithm and that algorithm also known as the shortest path first algorithm and link state algorithm. These are the three names of one algorithm of the internet layer's routing protocol OSPF.

Link Layer

This layer is the 1st layer of the TCP/IP Model and that layer is also known as the network access layer. It is very helpful for the understanding of the how data should sent through the network. This layer concern with the how the data transmit between the two devices.