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.
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.