TCP/IP Model – Explanation, Layers, Pros and Cons

TCP IP Model

Find out what is the TCP/IP Model, how does it work, what are its advantages and disadvantages. This article also explains its four different layers.

We all know communication has become an integral part of our day to day lives. Humans, animals and even machines need to communicate with each other for various purposes. Yes, you have read it right, even devices (or computers) have to communicate with each other. So these computers have a common way to communicate with their fellow computers with the help of TCP/IP. Most of the computers follow TCP/IP nowadays which is built into computers and is mostly automatically operated. The whole article is about how TCP / IP works, their advantages and disadvantages and some standard TCP / IP protocols.

Why is communication important among computers?

We know, that an individual computer can perform a lot of jobs, like calculating complicated mathematical equations, summarizing data into graphs and curves, playing audio and video and much more! But do you know that it is not the computer’s real power? The real power of the computer shines when we allow it to communicate with other computers! Let us think about some of the everyday things done by computer- sending an e-mail, watching Netflix or Amazon Prime, getting directions via the map, downloading audio or video files, watching an online soccer match etc. You will see that all these tasks requires YOUR computer to communicate with OTHER systems. All these computers involved may be from different geographic locations, with various human operators, or running on different operating systems!

Why are protocols necessary in communication between computers?

As discussed above, computers need to communicate with each other to bring out the best performance. This type of communication may be between two computer systems or even hundreds of systems! To make this communication error and chaos-free, computers should be aware of how they should behave, even before the communication starts. They should know the answers to the following questions:

  • “How do they start the conversation?”
  • “Whose turn is it to communicate?”
  • “How does each computer know its message was transmitted correctly?”
  • “How do they end the conversation?”

Don’t you think these questions are similar to how humans are supposed to behave? Just like there are some rules or ‘protocols’ which humans have to follow while communicating, Computers also have these protocols. A protocol, in a layman’s term, is “An agreed-upon set of rules”. Set the same for all the computers. All the machines involved in communication have their own set of protocols set for communication for each other. Like, CB radio use codes like “10-4” or telegraphs using morse codes.

The same kinds of rules are also there with computers. But these rules in case of computers are more hard and fast. It is because when all the computers use the same protocols, one can transfer information without any issue. But suppose there are different protocols for different computers. What do you expect to be the result? Isn’t complete chaos it?

Before the 1960s, communication between computers was very complicated. Each vendor has his own way of communicating between his computers. This created problems when he wanted his computer to communicate with someone else’s computers. This led to people and vendors agreeing that there was a need to set up an agreed-upon standard for all the computers so that the communication becomes feasible. And thus the standard was set, called TCP / IP.

What is TCP / IP?

By definition, “Internet protocol suite is the conceptual model and set of communication protocols used in the internet and similar computer networks.” Popularly, it is known as TCP / IP. This is because the foundational protocols in Internet Protocol suite are Transmission Control Protocol (TCP) and the Internet Protocol (IP). While TCP / IP was developing, some versions of it were called the Department of Defence (DoD) model. It was because the whole development was funded by the United States Dept of Defense.

The internet protocol suite offers end-to-end data communication. It also specifies the way of packetizing, addressing, transmitting, routing and receiving data. The whole functionality of TCP / IP is organized into four abstraction layers, viz link layer, internet layer, transport layer and application layer. These layers classify all the related protocols of TCP / IP according to the scope of networking involved in it.

The Internet Engineering Task Force (IETF) maintains the technical standards underlying the internet protocol suite, and it’s elements.  The TCP / IP is a predecessor to the OSI model, which is a more comprehensive reference framework for a general networking system.

What is the difference between TCP and IP?

TCP and IP are two different computer network protocols. IP is the protocol which is responsible for obtaining the address to which data is sent. TCP, on the other hand, is concerned about delivering the data once the system gets that IP address. Of course, one can separate IP and TCP, but there is no sense of doing so. People generally use TCP and IP together. You must have heard “TCP / IP” and “TCP / IP model”. These have become recognized terms in the IT industry. To elaborate in simple terms, let us say that the IP address is the phone number assigned to your smartphone. And TCS is then all the technology to make your phone communicate someone else phone in the form of phone calls, WhatsApp messages or Facebook. One is entirely useless without the other. And hence we use both TCP and IP together.

How does TCP / IP actually work?

The Department of Defence of the United States sponsored the development of TCP / IP. The main objective was to specify how computers can transfer data from one device to another. TCP / IP puts particular emphasis on the accuracy of data transfer and has numerous steps to ensure the same.

Let explain in brief one of the ways to ensure the accuracy of data transfer by TCP / IP. Suppose, a system has to send a particular message to another system in one piece, it would have been a bit risky. If the message encounters any problem midway, the operation will fail. The system thus may have to resend the data. To avoid this problem, TCP / IP breaks each message into numerous packets. When the packets are received at the other end, they are reassembled. If the first route is not available or congested, each packet can take a different route to the destination.

Apart from that, TCP / IP also divides different communication tasks into four different layers. Each layer has a unique function. Here, the received data has to go through different layers before it reaches the other end. I will explain it broadly in the next section. TCP / IP’s task is to go through these layers again but in reverse order to reassemble the data and then present it to the receiving end.

The chief purpose of these layers is to keep things standardized without forcing various hardware and software vendors to communicate on their own. Like, let us talk about a car. All car manufacturers agree on the location of steering wheels, breaks, accelerators and gears. So that is something which is standardized among all the vehicles across the globe. So it means that, if one wants, he can update a particular layer without being forced to update the whole system.

The four layers of TCP / IP

TCP / IP works in four layers, and each includes some specific protocols. Each layer of TCP / IP is defined according to the particular function it is supposed to perform. All these layers work together in order to transfer data from one layer to another.

TCP IP Model Layers

Application Layer

This layer is responsible for interacting with the application program of the receiving end. The application layer is the highest level of the OSI model. It is the OSI layer which is closest to the receiving user. This layer allows the operators of the system to communicate with other software applications.

The Application layer is responsible for interacting with the applications to execute the communicating component. However, the data interpretation by the application model is beyond the capacity of the OSI Model.

Example of application layer can be e-mail, remote login or even file transfer.

Let us have a look at the functions of Application Layers:

  1. This layer provides users with various electronic mailing services.
  2. Allows the users to remote control other system or login to a remote host.
  3. It will help the users to identify his communication partners and determining some resource availability.

Transport Layer

The primary function of the transport layer is to build a network layer to provide the transportation of data from a process of the system from source to a process of the system from the destination. The transport layer is responsible for maintaining the quality of service function. The transport layer can be hosted using single or even multiple networks.

The transport layer decides the amount of data to be sent and the rate of transfer too. It ensures errorless data delivery from the host to the receiver. You can also control the reliability of a link via error control, flow control, or segmentation and desegmentation. After successful data transfer, transport layer offers a conformation to the user. After that, it sends the next data, in case no error has occurred.

Let us have a look at the essential functions of the transport layer.

  1. The transport layer is responsible for delivering the message to the exact process of the destination system.
  2. Divides the received message from the session layer into numerous segments and assigns them numbers in order to make a sequence.
  3. Transport Layer makes sure that the whole message is delivered without any error. If there is an error, the transport layer re-transmits the data before moving on to the next data.

Internet Layer

The internet layer is the second layer of the TCP / IP model. It is known as ‘network layer’ too. The main task of this layer is to transfer the data packets from one network or system to their destination. The internet layer does not concern itself about the route which the data packets take. This layer offers numerous methods to transfer data of variable length and sequence from one node to another by taking the help of different networks.

The network interface layer

The network interface layer is also called a network access layer and is the final layer in the TCP / IP model. This layer is responsible for defining various details in the data transfer like how you can send data using the network. It also defines how hardware devices should optically signal various bits with a network medium, like optical, coaxial, coaxial fibre etc.

Advantages of TCP / IP protocol suite

  1. It is a widely accepted model which can be deployed effectively in all the practical networking problems.
  2. TCP / IP can also allow cross-platform communications among heterogeneous networks.
  3. Any individual or organization can use TCP / IP suite without any reorganization or permission. Basically, no institution or individual owns the TCP / IP suite.
  4. You can add networks without disturbing any service with the help of TCP / IP.
  5. The best thing about TCP / IP is that it assigns a unique IP address to each computer or system registered on a network. This makes each device exclusive in the network.
  6. Almost all the routers can read TCP packets and give special service to them.

Disadvantages of TCP / IP protocol suite

  1. TCP / IP model is not generic in nature. This means TCP / IP fails to represent any other stack (for example Bluetooth) except TCP / IP suite.
  2. TCP / IP does not clearly distinguish the concepts of interfaces, protocols and services. So this model cannot describe new models or new technologies.
  3. Again, it does not differentiate between the data link and physical barriers.
  4. Originally, TCP / IP was designed for wide area networks. So it cannot work so efficiently with Low Area Network (LAN) and Personal Area Network (PAN).
  5. Among the suite protocols of TCP / IP, only TCP and IP worked well in the long run whereas others lost their relevance with time. However, they are still in use even after over 50 years of their introduction. This is because of the immense popularity of TCP / IP!
  6. TCP / IP is difficult to set up and maintain as compared to IPX/SPX or NetBEUI.
  7. To have a centralized TCP / IP domain, it requires a lot of efforts for registration.

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