TCP/IP Model (Internet Protocol Suite): Functions, ICMP, Transport Layer

TCP/IP Model stands for Transmission Control Protocol/Internet Protocol Model. The TCP/IP model contains four layers from the seven layers of the OSI model. Hence it is known as a concise version of the OSI model.

In this article, we have shared all the basic information about the TCP/IP Model such as the function of the TCP/IP Model.

Internet Protocol Suite: TCP/IP Model

four layers in tcp ip model

TCP/IP Model is also known as the Internet Protocol Suite because it is the set of communications protocols used in the Internet and similar computer networks.

The current main protocols in the suite are the Transmission Control Protocol and the Internet Protocol.

Each layer within the Internet Protocol Suite has a specific function. When all these layers of the TCP/IP model are combined and transmitted, communication between systems can occur.

Four primary layers of the TCP/IP Model are as follows;

  • Application Layer,
  • Transport Layer,
  • Network Layer, and
  • Internet (Link) layers.

The TCP/IP Model came first, followed by the OSI model. The TCP/IP Model and the OSI model are not identical. The application layer, transport layer, network layer, data link layer, and physical layer are the layers of the TCP/IP Model.

The first four levels, which correspond to the first four layers of the OSI model, including physical standards, network interface, inter-networking, and transport services, and these four layers are represented in the TCP/IP paradigm by a single layer termed the application layer.

TCP/IP is a hierarchical protocol made up of interacting modules, each of which has its own set of features. 

Hierarchical refers to the fact that each upper-layer protocol is backed up by two or more lower-layer protocols.

Must Read ➜ What is HTTP?

TCP/IP Model Layers Functions

tcp ip model layer functions

TCP/IP Model layers have the following functions:

Application Layer Function in TCP/IP Model:

  • During a communication session, both the source and destination devices use application layer protocols.
  • The application layer protocols deployed on the source and destination hosts must match for the communications to be successful.

Must Read ➜ Application Layer Protocols

Transport Layer Function in TCP/IP Model

  • It specifies how data should be physically transmitted through the network. 
  • This layer is primarily in charge of data transfer between two devices on the same network. 

Network/Internet Layer function in TCP/IP Model:

  • Encapsulating IP datagrams into network frames and translating IP addresses to physical addresses are two of the services performed by this layer. 
  • Ethernet, token ring, FDDI, X.25, and frame relay are the protocols used by this layer. 
  • The second tier of the TCP/IP Model paradigm is the internet layer. 
  • The network layer is another name for the internet layer. 
  • The internet layer’s primary function is to send packets from any network to their destination, regardless of the route they take.

Data Link or Network Access Layer Function in TCP/IP Model 

  • The TCP/IP model’s lowest layer is the network layer. 
  • The OSI reference model defines a network layer as a mixture of the Physical and Data Link layers.

Must Read ➜ Data Link Layer in OSI Model

TCP/IP Model Layers Protocols:

The protocols used at layers in TCP/IP Model are as follows: 

IP Protocol: This layer employs the IP protocol, which is the most important component of the TCP/IP suite. 

This protocol’s obligations are as follows: 

IP Addressing: This protocol implements IP addresses, which are logical host addresses. The internet and higher layers employ IP addresses to identify devices and to provide internetwork routing. 

The path along which data is to be transferred is determined by host-to-host communication. 

Data Encapsulation and Formatting: The data from the transport layer protocol is accepted by an IP protocol. An IP protocol wraps data into a message known as an IP datagram and ensures that it is transferred and received securely. 

Fragmentation and Reassembly: The Maximum Transmission Unit (MTU) is the size limit set by the data link layer protocol on the size of an IP datagram (MTU). If the size of an IP datagram exceeds the MTU unit, the IP protocol divides the datagram into smaller units for transmission across the local network.

The sender or an intermediary router can fragment data. All of the fragments are reassembled at the receiver’s end to make an original message. 

Direct delivery occurs when an IP datagram is transferred via the same local network, such as a LAN, MAN, or WAN. The IP datagram is transferred indirectly when the source and destination are on a different network. The IP datagram can be routed through multiple devices, such as routers, to do this.

ARP Protocol: ARP Protocol is a protocol that allows you to communicate with Address Resolution Protocol (ARP) is an acronym for Address Resolution Protocol. 

ARP is a network layer protocol for determining a physical address based on an IP address. 

The ARP Protocol is mostly connected with the two terms: 

ARP request: When a sender wants to know the device’s physical address, it sends an ARP request to the network. 

ARP reply: Every network device will receive and process the ARP request, but only the recipient will identify the IP address and respond with its physical address in the form of an ARP reply. The physical address is added to the recipient’s cache memory as well as the datagram header.

Must Read ➜ Types of Routing Protocols

Internet Controlled Messaging Protocol (ICMP) 

The Internet Control Message Protocol (ICMP) stands for Internet Control Message Protocol. 

It is a method used by hosts or routers to communicate back to the sender notifications about datagram errors. 

Until it reaches its destination, a datagram goes from router to router. The ICMP protocol is used to alert the sender that the datagram is undeliverable if a router is unable to route the data due to unexpected conditions such as disabled links, a device on fire, or network congestion. 

The most common terms used in an ICMP protocol are: 

ICMP Test: The ICMP Test is used to determine whether or not a destination can be reached. 

ICMP Reply: The ICMP Reply command is used to determine whether or not the destination device is responding. 

The ICMP protocol’s primary function is to notify problems rather than to solve them. The sender bears responsible for the adjustment. 

Because the IP datagram carries the addresses of the source and destination but not of the router to which it is sent, ICMP can only transmit messages to the source and not to intermediate routers. 

Transport Layer In TCP/IP Model 

  • The transport layer is in charge of data dependability, flow control, and correction as it travels through the network. 
  • User Datagram Protocol and Transmission Control Protocol are the two protocols utilized in the transport layer. 

 The User Datagram Protocol (UDP) is a protocol that allows (UDP) 

  • It delivers a connectionless service as well as end-to-end transmission delivery.  
  • It’s a shaky protocol since it detects mistakes but doesn’t tell you what they are. 
  • The error is discovered by the User Datagram Protocol, and the ICMP protocol informs the sender that the user datagram has been corrupted. 

The fields that make up UDP are as follows: 

  • The address of the application software that created the message is known as the source port address. 
  • The address of the application software that receives the message is known as the destination port address. 

Transmission Controlling Protocol (TCP):

  • It provides apps with full transport layer services. 
  • It establishes a virtual circuit between the sender and the receiver, which remains active throughout the communication. 
  • TCP is a dependable protocol since it detects errors and retransmits the frames that have been damaged. As a result, before the transmission is considered complete and a virtual circuit is deleted, all segments must be received and acknowledged. 
  • TCP breaks the entire message into smaller units known as segments at the sending end, and each segment contains a sequence number that is used to arrange the frames to form the original message. 
  • TCP takes all segments and reorders them depending on sequence numbers at the receiving end. 
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