Computer Networks – An Overview of TCP/IP Model

Transmission Control Protocol/Internet Protocol (TCP/IP) model is a concise version of the OSI Model. The TCP/IP protocol suite was developed before the OSI model. But the layers in the TCP/IP protocol suite do not exactly match those in the OSI model.

TCP/IP Protocol

  • The original TCP/IP protocol uses four layers − host-to-network, Internet, Transport, and Application layer.
  • The host-to-network layer is equivalent to the combination of physical and data link layers in the OSI model.
  • The Internet layer in TCP/IP is equivalent to the Network layer of the OSI model. And the Application layer does the job of the Session, Presentation, and Application layers with the Transport layer in TCP/IP.
  • In the TCP/IP model, the first four layers provide physical standards, network interface, internetworking, and transport functions.
  • The first topmost layers (application, presentation, and session layers) in the OSI model are represented in TCP/IP by a single layer called the application layer.
  • In the Transport layer, the TCP/IP model defines three protocols − Transmission Control Protocol (TCP), User Datagram Protocol (UDP), and the Stream Control Transmission Protocol (SCTP).

TCP/IP Protocol Suite to the OSI Reference Model

Application Layer

In TCP/IP, the Application layer protocols provide services to the application software running on a computer. The application layer uses HTTP, POP3, and SMTP protocols. The application layer provides an interface between the software running on a computer and the network itself.

Transport Layer

In TCP/IP, the Transport layer includes transmission control protocol (TCP) and user datagram protocol (UDP). TCP provides services to the application layer that reside above the transport layer or higher within the TCP/IP model.

Internet Layer (Network Layer)

The Internet layer in the TCP/IP model is the Network Layer 3 of the OSI model. It stores the IP addresses and the routing data. When data is transmitted from a node on one LAN to a node on a different LAN, the Internet Layer is used. IPv4, IPv6, ICMP, and routing protocols (among others) are the Internet Layer TCP/IP protocols.

Host-to-Network or Link Layer

In TCP/IP, the Host-to-Network layer is also called the network interface or link layer. It provides services to the upper layer within the model. When a host’s or router’s IP process chooses to send an IP packet to a different router or host, that host or router then uses the link-layer details to send that packet to the next host/router.

This layer is the lowermost layer of the TCP/IP model; it is concerned with the physical transmission of data. It is like a combination of the data link layer and physical layer of the OSI model.

Updated on: 23-Nov-2021

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