What is TCP/IP reference model ?



What is TCP/IP reference model ?

  • TCP/IP means Transmission Control Protocol and Internet Protocol. It is the network model used in the current Internet architecture as well.
  • Protocols are set of rules which govern every possible communication over a network.
  • These protocols describe the movement of data between the source and destination or the internet. They also offer simple naming and addressing schemes.

TCP/IP Reference Model

Features of TCP/IP reference model

  • Support for a flexible architecture. Adding more machines to a network was easy.
  • The network was robust, and connections remained intact until the source and destination machines were functioning.

Protocol and networks in the TCP/IP model

Different Layers of TCP/IP Reference Model

Layer 1: Host-to-network Layer

  • Lowest layer of the all.
  • Protocol is used to connect to the host, so that the packets can be sent over it. Varies from host to host and network to network.

Layer 2: Internet Layer

  • Selection of a packet switching network which is based on a connectionless internetwork layer is called a internet layer. This layer which holds the whole architecture together.
  • It helps the packet to travel independently to the destination.
  • Order in which packets are received is different from the way they are sent.
  • IP (Internet Protocol) is used in this layer.

The various functions performed by the Internet Layer are

  • Delivering IP packets.
  • Performing routing.
  • Avoiding congestion.

Layer 3: Transport Layer

  • It decides if data transmission should be on parallel path or single path.
  • Functions such as multiplexing, segmenting or splitting on the data is done by transport layer.
  • The applications can read and write to the transport layer.
  • Transport layer adds header information to the data.
  • Transport layer breaks the message (data) into small units so that they are handled more efficiently by the network layer.
  • Transport layer also arrange the packets to be sent, in sequence.

Layer 4: Application Layer

  • The TCP/IP specifications described a lot of applications that were at the top of the protocol stack. Some of them were TELNET, FTP, SMTP, DNS etc.
    • TELNET is a two-way communication protocol which allows connecting to a remote machine and run applications on it.
    • FTP (File Transfer Protocol) is a protocol, that allows File transfer amongst computer users connected over a network. It is reliable, simple and efficient.
    • SMTP (Simple Mail Transport Protocol) is a protocol, which is used to transport electronic mail between a source and destination, directed via a route.
    • DNS (Domain Name Server) resolves an IP address into a textual address for Hosts connected over a network.
  • It allows peer entities to carry conversation.
  • It defines two end-to-end protocols : TCP and UDP
    • TCP (Transmission Control Protocol) : It is a reliable connection-oriented protocol which handles byte-stream from source to destination without error and flow control.
    • UDP (User-Datagram Protocol) : It is an unreliable connection-less protocol that do not want TCPs, sequencing and flow control. For Example One-shot request-reply kind of service.

Advantages of TCP/IP model

  • It operated independently.
  • It is scalable.
  • Client/server architecture.
  • Supports a number of routing protocols.
  • Can be used to establish a connection between two computers.

Disadvantages of TCP/IP Model

  • In this layer does not guarantee delivery of packets.
  • The model cannot be used in any other application.
  • Replacing protocol is not easy.
  • It has not clearly separated its services, interfaces and protocols.

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