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Networking is a key area of functionally for Linux. Not only does Linux support the standard Internet protocols used for most UNIX- to-UNIX communication, but it also implements a number of protocols native to othe, non UNIX operating systems. In particular, since Linux was originally implemented pri -marily on PCs, rather than on large workstations or on PC networks, such as appletalk and IPX
Internally, networking in the Linux kernel is implemented by three layers of software:
1. The socket interface
2. Protocol drivers
3. Networking-device-drivers
User application perform all networking requests through the socket inter-face this interface is designed to look like the BSD4.3 socket layer so that any programs designed to make use of Berkeley sockets will run on Linux without any source -code changes.The BSD socket interface is sufficiently genral purpose to represent network addresses for wide range of networking protocols. This single interface is used in Linux to access not just those protocols implemented on standard BSD systems, but all the protocols suppoted by the system.software
The next layer of software is the protocol stack, which is similar in orgnization to BSD's own framework. whenever andy networking data arrives at this layer, either from an application's socket of from a network-device driver, the data are expected to have been tagged with an identifier specyfing which network protocol they contain. Protocols can communicate with one another manage routing, error reporting, and reliable retransmission of lost data.