A NET WORK

A NET WORK

A network is a collection computers and devices connected together via communication devices and media.  Communication devices enable two or more computers to exchange items such as data, instructions and information with each other.

The primary function of a communication device (e.g a modem) is to convert signals so that they become suitable for the communications channel or a receiving device.

A network can relatively small or extensively large.

 A LOCAL AREA NETWORK (LAN)

This is a network that connects computers in a limited geographical area such as a school computer laboratory, an office or a group of closely positioned buildings.

Each computer or a device on the network is called a node.  The nodes are connected to the LAN via cables.

A wireless LAN is a local area network that uses no physical wires but wireless media such as radio waves.

A network operating system is the system software that organizes and coordinates the activities of a LAN.

KINDS OF A LAN

Two kinds of LAN are peer to peer and client/server network.

(a)   PEER-TO-PEER NETWORK

-       Each computer on a peer-to-peer network can share hardware, data or information located on any other computer on the network.

-       Each computers stores files on its own storage devices.

-       Each computer on the network contains both the network operating system and application software.

-       A peer-to-peer network is a simple, inexpensive network that generally connects less than 10 computers together.

-        Ideal for home and small business.

Fig:  Illustration of a peer-to-peer network

Advantages of peer-to-peer network

-       Less expensive to implement.

-       Does not require additional specialized network administration software.

-       Does not require a dedicated network administrator.

Disadvantages

-       Does not scale well to large networks and administration becomes unmanageable.

-        Each user must be trained to perform administrative tasks.

-       Less secure.

-       All machines sharing resources negatively impact the performance.

(b)   CLIENT/SERVER NETWORK

A client/server network has one or more computers acting as a server while the other computers (i.e clients) on the network can request services from the server.

A client/server network typically provides an efficient means to connect 10 or more computers together.

Most client/server networks have a network administrator who is in charge of the network.

Fig: Illustration of Client server network

Advantages of client/server network

-       Provides for better security.

-       Easier to administer when the network is large because administration is centralized.

-       All data can be backed up on one central location.

Disadvantages

-       Requires expensive specialized network administrative and operational software.

-       Requires expensive, more powerful hardware fro the server machine.

-       Requires a professional administrator.

-       Has a single point of failure, User data is un available if the server is down.

 A WIDE AREA NETWORK (WAN)

This is a network that covers a large geographical area such as one that connects the district offices of an enterprise across the country or across several countries in the world.

WANS are designed to:

-       Operate over a large geographical area

-       Allow access over a serial interfaces operating at a slow speed.

-       Provide full time and part-time connectivity.

-       Connect devices separated over wide, even global areas.

Computers are often connected to a WAN via public networks such as the telephone system or by dedicated lines or satellites.  A WAN  can be made up of two or more LANs connected together.  The INTERNET is the world’s largest WAN.

ADVANATAGES OF USING A NETWORK

(a)    Facilitates communication because people can communicate efficiently and easily via e-mail, instant messaging, chat rooms, telephony and video conferencing.

(b)   Reduce costs by sharing hardware (e.g a printer) and software (e.g using a network version or site license of a program).

(c)    Sharing data and information stored on other computers on the network.

(d)   Allow tight control over who has access to what data.

DISADAVANTAGES OF USING A NETWORK

(a)    The hardware, software and expertise required to set up a network can be expensive.

(b)   Networks are vulnerable security problems.

(c)     If the server fails to work, the complete network may also fail to work.

COMPONENTS OF A LAN

Local area networks are made up of several standard components.

(a)    Connecting or cabling system. LANs do not use a telephone network, instead they use some other cabling or connection system either wired or wireless.  Wired connection may be twisted pair wiring, coaxial or fibre optic cable.  Wired connection may be infrared or radio wave transmission.  Wireless network are especially useful if computers are portable and moved often.  However, they are subject to interference.

(b)   Microcomputers with interface cards.   Two or more computers are required along with network interface cards.  A network card which is inserted into expansion slot in a micro computer enable the computer to send a nd receive messages on the LAN.  Now days, newer computers come with network cards already embedded in the motherboard.

(c)    Network operating systems.  The network operating system software manages the activity of the network.  Depending on the type of a network, the operating system may be stored on a file server or on each microcomputer on the network. Examples of network operating systems include:

–     Novell’s netware

–     Windows NT e.t.c

(d)   Other shared devices.  Printers fax machine, scanners, storage devices and peripherals may be added to the network as necessary and shared by all users.

(e)    Bridges and gateways.  A LAN many stand alone but it may also connect to other networks either similar or different in technology.  Hardware and software devices are used as interfaces to make these connections.

A Bridge is an interface that enables similar networks to communicate.

A gateway is an interface that enables dissimilar networks to communicate such as a LAN with a WAN.