layers of TCP/IP architecture

The Internet architecture is also known as TCP/IP architecture and is widely used. This architecture evolved out of a packet-switched network ARPANET. It is a four layered model.

 

It does not enforce strict layering, i.e., applications are free to bypass transport layer and can directly use IP or any of the underlying networks.

IP layer serves as focal point in the architecture i.e., it defines a common method for exchanging packets to any type of network and segregates host-to-host delivery from process-to-process delivery. 

For any protocol to be added to the architecture, it must also be accompanied by at least one working implementation of the specification. Thus efficiency is ensured.

TCP/IP does not define any specific protocol for the lowest level (physical/data link layers of OSI).

o All standard and proprietary protocols such as Ethernet, FDDI, etc are supported. o The protocols are generally implemented by a combination of hardware/software.

Network layer consists of a major protocol, the Internetworking Protocol (IP).

o   It supports the interconnection of multiple networking technologies into a logical internetwork.

o  It is an unreliable and connectionless protocol.

o   IP sends data in packets called datagrams, each of which is transported separately and independently.

o   The other protocols supported in this layer are ARP, RARP, ICMP and IGMP.

Transport layer is responsible for delivery of a message from one process to another process. The two protocols supported in this layer are:

o   Transmission Control Protocol (TCP) for connection-oriented reliable byte-stream channel.

o   User Datagram Protocol (UDP) for connectionless unreliable datagram delivery channel.

Application layer supports a wide range of protocols such as FTP, TFTP, Telnet (remote login), SMTP, etc., that enable the interoperation of popular applications. This layer is equivalent to combined session, presentation, and application layers in the OSI model.