What are the 4 layers of TCP IP?

Protocols are sets of rules for message formats and procedures that allow machines and application programs to exchange information. These rules must be followed by each machine involved in the communication in order for the receiving host to be able to understand the message. The TCP/IP suite of protocols can be understood in terms of layers (or levels).

This figure depicts the layers of the TCP/IP protocol. From the top they are, Application Layer, Transport Layer, Network Layer, Network Interface Layer, and Hardware.

Figure 1. TCP/IP suite of protocols

TCP/IP carefully defines how information moves from sender to receiver. First, application programs send messages or streams of data to one of the Internet Transport Layer Protocols, either the User Datagram Protocol (UDP) or the Transmission Control Protocol (TCP). These protocols receive the data from the application, divide it into smaller pieces called packets, add a destination address, and then pass the packets along to the next protocol layer, the Internet Network layer.

The Internet Network layer encloses the packet in an Internet Protocol (IP) datagram, puts in the datagram header and trailer, decides where to send the datagram (either directly to a destination or else to a gateway), and passes the datagram on to the Network Interface layer.

The Network Interface layer accepts IP datagrams and transmits them as frames over a specific network hardware, such as Ethernet or Token-Ring networks.

Figure 2. Movement of information from sender application to receiver host

This figure shows the flow of information down the TCP/IP protocol layers from the Sender to the Host.

Frames received by a host go through the protocol layers in reverse. Each layer strips off the corresponding header information, until the data is back at the application layer.

Figure 3. Movement of information from host to application

This figure shows the flow of information up the TCP/IP protocol layers from the Host to the Sender.

Frames are received by the Network Interface layer (in this case, an Ethernet adapter). The Network Interface layer strips off the Ethernet header, and sends the datagram up to the Network layer. In the Network layer, the Internet Protocol strips off the IP header and sends the packet up to the Transport layer. In the Transport layer, the TCP (in this case) strips off the TCP header and sends the data up to the Application layer.

Hosts on a network send and receive information simultaneously. Figure 4 more accurately represents a host as it communicates.

The excess requirement of efficient and error-free data transmission over communication channels leads us to the discussion of the topic - what is the TCP/IP model. This tutorial will easily help to make you understand the basis and need for the TCP/IP model in the network domain. The TCP/IP is needed for implementing various network applications during the transmission of data and information over the communication channel.

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What Is TCP/IP Model?

The TCP/IP model refers to the Transmission Control Protocol/Internet Protocol Model. This model is a part of the network domain designed specifically for overseeing efficient and error-free transmission of data.

The model works on a four-layered architecture model, where each layer implicit the required network protocols on the data to be transmitted, which remodels the data to the most optimum structure for efficient transmission over the network.

In this tutorial on what is TCP/IP model is, you will understand the working of each layer in detail to better understand the functioning of the model.

Features of the TCP/IP Model

Below mentioned are some of the features that make the TCP/IP model stand out in the network concepts:

• The TCP/IP model is among one of the most important network concepts that contributed to the working of ARPANET.
• The TCP/IP model comprises four layers: the network access layer, internet layer, transport layer, and application layer (going from bottom to top).
• The network model is implemented during network and communication-related issues.
• Communication between different modes of network devices is possible through the application of various layers.
• The layers in the model provide maintenance of communication channel, flow control, reliability check format, among other applications in the form of protocols.

Now go ahead and continue with the next topic in this tutorial on ‘what is TCP/ IP model’, which includes the layers of the TCP/IP model.

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Layers of the TCP/IP Model

In this section, you will understand the different layers of the model and their functionality in the network concept:

The TCP/IP model is divided into four different layers:

• Application layer
• Transport layer
• Internet layer
• Network Access layer

Each layer performs a specific task on the data that is being transmitted over the network channel, and data moves from one layer to another in a preset pattern as mentioned below:

The above model represents the flow of data when it is being transmitted from the sender side. In the case of data being received, the layers of the model work in reverse order.

Now, take a look at each of the layers in detail:

Application Layer

This is the topmost layer which indicates the applications and programs that utilize the TCP/IP model for communicating with the user through applications and various tasks performed by the layer, including data representation for the applications executed by the user and forwards it to the transport layer.

The application layer maintains a smooth connection between the application and user for data exchange and offers various features as remote handling of the system, e-mail services, etc.

Some of the protocols used in this layer are:

• HTTP: Hypertext transfer protocol is used for accessing the information available on the internet.
• SMTP: Simple mail transfer protocol, assigned the task of handling e-mail related steps and issues.
• FTP: This is the standard protocol that oversees the transfer of files over the network channel.

Now, move on to the next layer, 

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Transport Layer

This layer is responsible for establishing the connection between the sender and the receiver device and also performs the task of dividing the data from the application layer into packets, which are then used to create sequences. 

It also performs the task of maintaining the data, i.e., to be transmitted without error, and controls the data flow rate over the communication channel for smooth transmission of data.

The protocols used in this layer are:

• TCP: Transmission Control Protocol is responsible for proper transmission of segments over the communication channel. It also establishes a network connection between the source and destination system.
• UDP: User Datagram Protocol is responsible for identifying errors, and other tasks during the transmission of information. UDP maintains various fields for data transmission such as:

• Source Port Address: This port is responsible for designing the application that makes up the message to be transmitted.
• Destination Port Address: This port receives the message sent from the sender side.
• Total Length: The total number of bytes of user datagram.
• Checksum: Used for error detection of the message at the destination side.

Moving on to the next layer, you have -

Internet Layer

The Internet layer performs the task of controlling the transmission of the data over the network modes and enacts protocols related to the various steps related to the transmission of data over the channel, which is in the form of packets sent by the previous layer.

This layer performs many important functions in the TCP/IP model, some of which are:

1. It is responsible for specifying the path that the data packets will use for transmission.
2. This layer is responsible for providing IP addresses to the system for the identification matters over the network channel.

Some of the protocols applied in this layer are:

• IP: This protocol assigns your device with a unique address; the IP address is also responsible for routing the data over the communication channel.
• ARP: This protocol refers to the Address Resolution Protocol that is responsible for finding the physical address using the IP address.

The last layer in the network model is the network access layer.

Network Access Layer

This layer is the combination of data-link and physical layer, where it is responsible for maintaining the task of sending and receiving data in raw bits, i.e., in binary format over the physical communication modes in the network channel.

• It uses the physical address of the system for mapping the path of transmission over the network channel.
• Till this point in this tutorial on what is TCP/IP model, you understood the basic idea behind the model and details about its layers, now compare the model with another network model.

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OSI Model vs. TCP IP Model

The TCP/IP model was designed in the 1960s to maintain and explain the transmission of data, whereas the OSI model is a network concept specifically for explaining the communication and working of data and protocols during the transmission of information.

OSI Model

TCP/IP Model

The OSI model consists of 7 layers.

TCP/IP model comprises 4 layers.

The OSI model has separate session and presentation layers.

This model comprises a session and presentation layer in the application layer.

The transport layer in this model provides a packet delivery protocol.

In this model, the transport layer does not have any such protocols.

This model is implemented during network communication.

This model is used as a reference model for the network channel.

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Conclusion

In this ‘What is TCP/IP model’ tutorial, you understood the network communication details about data, which includes the basic idea behind the working of the model, the functioning of each layer in the model, and also how the data is restructured to achieve efficient transmission over the communication channel.

To better understand the working of each layer and the different steps they take during the data transmission over the network from a professional point of view, you can refer to Simplilearn’s Cyber Security Expert course, which will allow you to gain in-depth knowledge about the network functions and working of the model at a whole new level.

Do you have any questions related to this tutorial on ‘What is TCP/IP model?’ If yes, feel free to mention them in the comments section at the bottom of this page. Our team will help you solve your queries ASAP.

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About the Author

Kartik Menon

Kartik is an experienced content strategist and an accomplished technology marketing specialist passionate about designing engaging user experiences with integrated marketing and communication solutions.

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