Explain the problems in TCP/IP Reference Model.

 Explain the problems in TCP/IP Reference Model.

Problems of the TCP/IP Reference Mode:

First, the model does not clearly distinguish the concepts of service, interface, and

protocol. Good software engineering practice requires differentiating between the

specification and the implementation, something that OSI does very carefully, and TCP/IPdoes not. Consequently, the TCP/IP model is not much of a guide for designing new

networks using new technologies. 

Second, the TCP/IP model is not at all general and is poorly suited to describing any

protocol stack other than TCP/IP. Trying to use the TCP/IP model to describe Bluetooth, for

example, is completely impossible. 

Third, the host-to-network layer is not really a layer at all in the normal sense of the

term as used in the context of layered protocols. It is an interface (between the network and

data link layers). The distinction between an interface and a layer is crucial, and one should

not be sloppy about it. 

Fourth, the TCP/IP model does not distinguish (or even mention) the physical and

data link layers. These are completely different. The physical layer has to do with the

transmission characteristics of copper wire, fiber optics, and wireless communication. The

data link layer's job is to delimit the start and end of frames and get them from one side to the

other with the desired degree of reliability. A proper model should include both as separate

layers. The TCP/IP model does not do this.

Finally, although the IP and TCP protocols were carefully thought out and well

implemented, many of the other protocols were ad hoc, generally produced by a couple of

graduate students hacking away until they got tired. The protocol implementations were then

distributed free, which resulted in their becoming widely used, deeply entrenched, and thus

hard to replace. Some of them are a bit of an embarrassment now. The virtual terminal

protocol, TELNET, for example, was designed for a ten-character per second mechanical

Teletype terminal. It knows nothing of graphical user interfaces and mice. Nevertheless, 25

years later, it is still in widespread use.