Introduction to networking

Introduction to networking

Networking is the practice of linking computing devices together with hardware and software that supports data communications across these devices.

Importance of networking

Information and communication are two of the most important strategic issues for the success of every enterprise.
While today nearly every organization uses a substantial number of computers and communication tools , they are often still isolated. While managers today are able to use applications like wordprocessors or spreadsheets, not very many of them use computer-based tools to communicate with other departments or information retrieval programs.

To overcome these obstacles in an effective usage of information technology, computer networks are necessary. They are a new kind of organization of computer systems produced by the need to merge computers and communications. At the same time they are the means to converge the two areas; the unnecessary distinction between tools to process and store information and tools to collect and transport information can disappear. Computer networks can manage to put down the barriers between information held on several (not only computer) systems. Only with the help of computer networks can a borderless communication and information environment be built.

Types of networking

Computers with a wireless connection to a network also use a network card (see Advice Sheet 20 for more information on wireless networking).

• LANs (Local Area Networks),

for example a computer network in a company's department

• MANs (Metropolitan Area Networks),

for example a cable television network within a city

• WANs (Wide Area Networks, Long Haul Networks),

for example an ISDN network

OSI Reference model

The Open System Interconnection (OSI) Reference Model was developed by the International Standards Organization (ISO). It is an attempt to build a framework of layers, in which various protocols in computer networking fit.

The OSI model consists of seven layers which are:

1. The Physical Layer: transmits raw data bits over a communication channel (mostly mechanical and electrical issues)
2. The Data Link Layer: guarantees to the network layer that there are no transmission errors by breaking the input datastream up into frames and sending back acknowledgement frames
3. The Network Layer: controls the operation of the involved subnet; main issues are routing (determine a way from source to destination) and dealing with problems of heterogenous networks, e. g. different size requirements of transmitted data blocks
4. The Transport Layer: splits up data from the session layer if necessary (segmentation) and ensures that the pieces arrive correctly
5. The Session Layer: allows users on different computer systems to establish a session between them, i. e. they are able to transfer files or log into a remote system; the conditions of communication are laid down, for example full-duplex or half-duplex
6. The Presentation Layer: unlike the layers before it is concerned with the syntax and semantics of the transmitted information; it is concerned with all aspects of information representation such as data encoding, data compression and encryption
7. The Application Layer: contains a variety of commonly needed protocols like handling with different terminal types and file systems; a label to identify the communication process, its origin and destination application is added to the transmitted information