What is TCP IP Model in Computer Network? All Layers, Diagram, Protocols, Features

In this write-up (part of our comprehensive Ethical Hacking Tutorial for Beginners), we are going to discuss what is TCP IP model in computer networks. In addition, we will go into depth about TCP IP model layers, features, architecture, advantages and disadvantages, as well as TCP IP model protocols.

This is among the most important topics in computer networking. So far, we have covered several topics related to it, including:

• What is computer networking and its types?

• What is IP address?

• What are the different types of IP addresses?

• What are networking ports?

• What is OSI model and its layers?

You can check the links to understand these concepts. Here, we have explained the TCP IP model in detail. So, let’s get started!

The full form of TCP/IP is Transmission Control Protocol/Internet Protocol.

The TCP/IP model is similar to the OSI model, but it is based on standard protocols. 

When we talk about network communications, it is the most used model. Its role is to enable end-to-end data transmission. 

The architecture of the TCP/IP model is more straightforward than the OSI model, as it has only four layers. Created by the Department of Defence (DoD), the TCP/IP model can be called a concise version of the OSI model.

Let's understand the concept of OSI model and TCP/IP model in detail with this quick video:

Here is the architecture diagram of TCP IP model in computer networking:

Image source: Oracle

Features that make the TCP/IP model stand out are:

• It is among the most important network concepts adopted by ARPANET.

• It is a connection-oriented protocol.

• Adding more systems to the network is hassle-free.

• Consists of four layers: the Network Access layer, Internet layer, Transport layer, and Application layer (from bottom to top).

• The network stays intact until the source and destination devices function properly.

• This network model is implemented during communication and network-related issues.

• Communication between different devices over the network is possible through various layers.

• It is reliable and ensures that the data arriving out of sequence is put back into the right order.

• The layers in the TCP/IP model takes care of flow control, maintenance of communication channel, and reliability check format.

• Allows to implement flow control so that the sender doesn’t overpower the receiver with data. 

There are 4 Layers in TCP/IP Model:

1. Application Layer

2. Transport Layer

3. Internet Layer

4. Network Access Layer

Below, we have explained all the layers of the TCP IP model in simple terms:

1. Application Layer

It is the top-most layer in the TCP/IP model, equivalent to the Application, Presentation, and Session layers of the OSI model and shares the same features. It works like an interface between application programs and interacts with them. It uses protocols such as FTP, SMTP, HTTP, HTTPS, SSH, NTP, SNMP, etc. Also, data acts as a Protocol Data Unit (PDU).

Functions of TCP IP Model Application Layer

• Helps to identify communication partners, synchronise communication, and determine resource availability.

• Handles high-level protocols and representation issues.

• As one Application layer protocol interacts with another, it forwards data to the Transport layer.

• Allows users to log in to a remote host.

• Offers several e-mail services.

• The layer offers distributed database sources and allows access to global information about different objects and services.

2. Transport Layer

The Transport layer in TCP IP model is responsible for transporting data from the source system to the destination system. It also provides flow control, reliability, and correction of data shared over the network. 

The layer also determines how much data should be shared and at what rate. The Transport layer is built on the message received from the application layer, ensuring data is delivered without an error in the sequence. 

This TCP IP model layer divides the data into packets, acknowledges them, and makes sure that the recipient also acknowledges the success of data transmission. 

Functions of TCP IP Model Transport Layer

• Divides the messages received from the Session layer into segments and create a sequence using numbers.

• It checks that the message is received error-free, else retransmits it.

• Makes sure the message is delivered to the correct destination.

3. Internet Layer

The Internet layer, also known as the Network layer, is another TCP/IP model layer responsible for logical addressing and routing. The layer forwards the packets from any computer and delivers them based on the IP addresses of the devices, making the Internet Protocol the most significant at this layer. 

The main task of the internet layer in TCP IP model is to ensure that the data is sent accurately and speedily and reaches the correct destination. So, if there’s heavy internet traffic, the layer might take a bit longer to send the file but with a minimal chance of an error corrupting it. 

Functions of Network Layer in TCP IP Model

• Offers procedural and functional methods to transfer variable-length data sequences.

• Protocols used in this layer are Internet Control Message Protocol (ICMP) and Internet Group Management Protocol (IGMP).

• Responsible for delivering the message to the correct destination.

4. Network Access Layer

The Network Access layer in TCP IP model is where hardware addressing is done. The layer is responsible for the physical infrastructure that allows computers to communicate with each other over the internet. 

This TCP IP model layer includes wireless networks, ethernet cables, device drivers, network interface cards, and more. It defines the protocols and every other detail of data transmission. 

Functions of Network Access Layer in TCP IP Model

• Includes the technical infrastructure as well, such as code to convert digital data into transmittable signals, that enables network connection.

• Handles the way bits should be signalled optically by hardware devices that directly interface with a network medium.

• Takes care of how data is sent physically through the network.

• Responsible for data transmission between two devices on the same network.

While sending a message, if the system shares the complete data into one piece and encounters an issue, the file must be resent. Therefore, TCP/IP breaks every message, be it a photo or a file, into packets based on the four-layer model and reassembles it on the receiving end. 

The data goes through the four layers of the TCP IP model in a specific order and follows the reverse order when it is reassembled on the other side.

Each packet can take a different route to the computer in case the first one is congested or unavailable. The TCP/IP model works as it follows a standardized procedure. It divides communication tasks between the layers, assigning specific functions to each. Hence, communication remains seamless, accurate, and efficient. 

The combined purpose of all four layers in the TCP IP model is to keep the data flow standardised without multiple software and hardware vendors managing the communication. Every layer can be updated for improved performance and security without affecting the entire model. All these features make the TCP/IP model one of the most effective ways to send data over the internet. 

The following are the main benefits of the TCP IP model:

• This industry-standard model can be deployed effectively on practical networking issues.

• Helps to establish connections between different computers.

• Allows cross-platform communication among heterogeneous networks, making it interoperable.

• Supports multiple routing protocols.

• Works independently without any operating system.

• Allows internetworking between organizations.

• It is an open protocol suite, i.e., it is not owned by any institute and can be used by any person or organization.

• It is known for its highly scalable client-server architecture, so it can add networks without disrupting current services.

• Assigns an IP address to every computer on the network, making them uniquely identifiable. 

• It assigns a domain name to each site along with the name and address resolution services.

The following are the limitations or drawbacks of the TCP IP model in computer networking:

• It is a complicated model, making it difficult to set up and manage.

• Generic in nature, so it doesn’t represent any protocol stack except TCP/IP suite. 

• Doesn’t distinguish between the Physical and Data Link layers, which have different functionalities. The Physical layer is responsible for laying down the physical features of transmission, while the Data Link layer is concerned with the transmission of frames. A great model should separate the two layers.

• Replacing protocol in this model is not that easy.

• Doesn’t separate different concepts, such as interfaces, services, and protocols. Hence, making it unsuitable for defining new technologies in new networks.

• The overhead of the TCP/IP model is higher than IPX.

• The Transport layer in the model doesn’t assure the delivery of packets.

• TCP/IP was initially designed for wide area networks and is not optimized for small networks, such as PAN (Personal Area Network) and LAN (Local Area Network).

Here is a look at the TCP/IP model protocol stack:

Protocols of Application Layer in TCP IP Model

1. HTTP and HTTPS 

HTTP stands for Hypertext Transfer Protocol, and HTTPS is HTTP-Secure. HTTP is used by the World Wide Web (WWW) to handle communication between servers and web browsers. HTTPS combines HTTP with SSL (Secure Socket Layer) and is efficient when the browser needs to sign in, fill out forms, authenticate, and perform bank transactions.

2. SMTP

SMTP stands for Simple Mail Transfer Protocol. It is responsible for handling e-mail-related issues and processes like sending data from one e-mail address to another.

3. FTP

FTP stands for File Transfer Protocol. It is a standard internet protocol that handles file transmission from one computer to another over the network channel.

4. SSH

SSH stands for Secure Shell. It is a preferred protocol as it maintains the encrypted connection and sets up a secure session.

5. SNMP

SNMP stands for Simple Network Management Protocol. This framework is used to manage devices on the internet through the TCP/IP protocol suite.

Protocols of Transport Layer in TCP IP Model

1. UDP

UDP stands for User Datagram Protocol. It offers connectionless services and handles end-to-end data transmission. However, it is unreliable as it can identify errors but can’t specify them. UDP finds errors, and ICMP reports them to the sender. 

UDP comprises the following fields:

• Source port address: It is the address of the application program that has created the message.

• Destination port address: The address of the application program receiving the message.

• Total length: Total number of bytes of the user datagram.

• Checksum: A 16-bit field used to detect an error.

2. TCP

TCP stands for Transmission Control Protocol. It offers all the transport layer services to applications. TCP creates a virtual circuit between the sender and the receiver and is active throughout the data transmission. It is more reliable as it discovers errors and retransmits the damaged frames. Thus, ensuring that all the segments are received and acknowledged before the data transmission is marketed completely and the virtual circuit is discarded. 

Protocols of Internet layer in TCP IP Model

1. IP

IP stands for Internet Protocol and assigns a unique address to the device. It is also responsible for delivering data from the source host to the destination host over the communication channel. IP has 2 versions:

• IPv4: Used most commonly by websites.

• IPv6: Growing in number as IPv4 addresses are limited compared to users.

2. ICMP 

ICMP stands for Internet Control Message Protocol and is encapsulated within IP datagrams. ICMP takes care of informing hosts about network problems.

3. ARP 

ARP stands for Address Resolution Protocol. It finds the hardware address of the host using the IP address. Different types of ARP are Proxy ARP, Reverse ARP, Gratuitous ARP, and Inverse ARP.

Protocols of Network Access Layer in TCP IP Model

The protocols used by this layer are: 

• token ring

• ethernet

• X.25

• FDDI

• frame relay

Some debate that ARP is a protocol of the Network Access layer rather than the Internet layer. They claim that it resides in layer 3 and is encapsulated by layer 2 protocols.

In this section, you will find some of the frequently asked questions about the TCP IP model of networking:

1. Who developed the TCP/IP model?

The TCP/IP protocol suite was designed by 2 DARPA scientists, Vint Cerf and Bob Kahn, most often called the fathers of the Internet, in the 1970s. It was developed by the U.S. Department of Defense and was adopted as the protocol standard for ARPANET (Advanced Research Project Agency Network) in 1983.

2. TCP/IP model consists of how many layers?

There are 4 layers in the TCP/IP model:

• Application layer

• Transport layer

• Internet layer

• Network Access layer

3. What does the TCP/IP model stand for?

The full form of the TCP/IP model is Transmission Control Protocol/Internet Protocol Model.