TCP/IP Model

Introduction to TCP/IP 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. These protocols offer simple naming and addressing schemes.

TCP/IP that is Transmission Control Protocol and Internet Protocol was developed by Department of Defence’s 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 untill the source and destination machines were functioning.

The overall idea was to allow one application on one computer to talk to(send data packets) another application running on different computer.

The layers in the TCP/IP protocol suite do not exactly match those in the OSI model. The original TCP/IP protocol suite was defined as having four layers: host-to-network, internet, transport, and application. However, when TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers: physical, data link, network, transport, and application.

A) APPLICATION LAYER
Application layer protocols define the rules when implementing specific network applications. It relies on the underlying layers to provide accurate and efficient data delivery. Typical protocols are:

• FTP – File Transfer Protocol: For file transfer Telnet – Remote terminal protocol: For remote login on any other computer on the network

• SMTP – Simple Mail Transfer Protocol: For mail transfer

• ·HTTP – Hypertext Transfer Protocol: For Web browsing

B) TRANSPORT LAYER
Transport Layer protocols define the rules of dividing a chunk of data into segments and then reassemble segments into the original chunk. Typical protocols are:TCP – Transmission Control Protocol: Provide functions such as reordering and data resend.

•  UDP – User Datagram Service: Use when the message to be sent fit exactly into a datagram and Use also when a more simplified data format is required.

•  SCTP - Stream Control Transmission Protocol: The Stream Control Transmission Protocol (SCTP) provides support for newer applications such as voice over the Internet.

C) NETWORK LAYER
Network layer protocols define the rules of how to find the routes for a packet to the destination It only gives best effort delivery. Packets can be delayed, corrupted, lost, duplicated, out-oforder.

•  IP – Internet Protocol: Provide packet delivery

•  ARP – Address Resolution Protocol: Define the procedures of network address / MAC address translation i.e The Address Resolution Protocol (ARP) is used to associate a logical address with a physical address. ARP is used to find the physical address of the node when its Internet address is known.

•  RARP – Reverse Address Resolution Protocol: The Reverse Address Resolution Protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.

•  ICMP – Internet Control Message Protocol: The Internet Control Message Protocol (ICMP) is a mechanism used by hosts and gateways to send notification of datagram problems back to the sender.

•  IGMP – Internet Control Message Protocol: The Internet Group Message Protocol (IGMP) is used to facilitate the simultaneous transmission of a message to a group of recipients.

D) PHYSICAL AND DATA LINK LAYER
At the physical and data link layers, TCP-IP does not define any specific protocol. Rather, it supports all the standard protocols.

Merits of TCP/IP model
1. It operated independently.
2. It is scalable.
3. Client/server architecture.
4. Supports a number of routing protocols.
5. Can be used to establish a connection between two computers.

Demerits of TCP/IP
1. In this, the transport layer does not guarantee delivery of packets.
2. The model cannot be used in any other application.
3. Replacing protocol is not easy.
4. It has not clearly separated its services, interfaces and protocols.

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