The TCP-IP Reference Model

TCP/IP means Transmission Control and Internet Protocol. It is the network model used in the current internet architecture as well. Protocols are a 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 or the internet. They also offer simple naming and addressing schemes.

Overview of the TCP/IP reference model

TCP/IP that is Transmission control and internet protocol was developed by the department of defenses project Research Agency (ARPA, later DARPA) as a part of a research project of network interconnection to connect remote machines.

The features that stood out during the research, which led to making the TCP/IP reference model were:

• 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.

The overall idea was to allow one application on one application on one computer to talk another application running on a different computer.

Different layers of TCP/IP Reference Model

Below we have discussed the 4 layers that form the TCP/IP reference model:

Layer 1: Host-to-network-Layer

i) The lowest layer of the all.

ii) The protocol is used to connect to the host so that the packets can be sent over it.

iii) Varies from host to host and network to network.

Layer 2: Internet Layer

i) The selection of a packet switching network which is based on a connectionless internetwork layer is called an internet layer.

ii) It is the layer that holds the whole architecture together.

iii) It helps the packet to travel independently to the destination.

iv) Order in which packets are received is different from the way they are sent.

v) IP is used in this layer.

vi) The various functions performed by the layer are:

• Delivering IP packets

• Performing routing

• Avoiding congestion

Layer 3: Transport Layer

i) It decides if data transmission should be on a parallel path or single path.

ii) Functions such as multiplexing, segmenting or splitting into the data are done by the transport layer.

iii) The application can read and write to the transport layer.

iv) The transport layer adds header information to the data.

v) The transport layer breaks the message into small units so that they are handled more efficiently by the network layer.

vi) The transport layer also arranges the packets to be sent, in sequence.

Layer 4: Application Layer

The TCP/IP specification described a lot of applications that were at the top of the protocol stack. Some of them were TELNET, FTP, SMTP, DNS, etc.

i) TELNET is a two-way communication protocol that allows connecting to a remote machine and runs applications on it.

ii) FTP (file Mail Transport Protocol), is a protocol that allows file transfer amongst computer users connected over a network. It is reliable, simple and efficient.

iii) SMTP (Simple Mail Transport Protocol) is a protocol, which is used to transport electronic mail between a source and destination, directed via a route.

iv) DNS (Domain name Server) resolves an IP address into a textual address for Hosts connected over a network.

v) It allows peer entities to carry a conversation.

vi) It defines two end-to-end protocols: TCP & UDP

• TCP (Transmission Control Protocol): It is a reliable connection-oriented protocol that handles byte-stream from source to destination without error and flows control.

• UDP (User-Datagram Protocol): It is an unreliable connection-less Protocol that does not want TCPs, sequencing and flows control.