INTRPCUCTION

NETWORK AND INTERNET:

NETWORK:

A network is defined as a system for connecting computers using a single transmission technology.
The computers can communicate with each other in a network.They can send and receive data from each other when they are in a network.

INTERNET:

The Internet is defined as the set of networks connected by routers that are configured to pass traffic among any computers attached to any network in the set. By internet many computers which are at longer distances from each other can communicate with each other.

CLASSIFICATION OF NETWORKS :

Computer networks are classified by four factors which are as follow:

1) By Size:
2) By Connectivity:
3) By Medium:
4) By Mobility:

1) BY SIZE:
According to their size there are two classifications of netwoeks.
1) Local Area Network. (LAN)
2) Wide Area Nerwork. (WAN)

In LAN network occupies the smaller area like a room a floor or a building.
In WAN,network occupies larger areas like cities & countries. Internet is a Wide Area Network.

LAN & WAN are compared by the speed of transmission, bandwidth and latency, management security, reliability,billing and their standards.

2) BY CONNECTIVITY:

Networks are also classified by connectivity in which two topologies are discussed.
a) Point-to-Point
b) Broadcast

a) POINT-TO-POINT
In Point-to-Point topology there are two topologies.
1) STAR topology
2) TREE topology

In star topology each computer is connected to a central hub. The communication
takes place through the hub.It is shown in the figure below.

Figure 1.1:star and tree topologies

In Tree topology all computers are connected to each other in such a way that they make a tree as shown in the figure above.

b) BROADCAST:
In broadcast topology ther are further two categories

1)SATELLITE\RADIO 2)RING TOPOLOGY

In a satellite or radio topology all camputers are connected to each other via satellite or radio wave as shown in the figure.

Figure:1.2 Satellite and Ring topologies:In a ring topology each computer is connected to other thorough a ring as shown in the figure above.

3) BY MEDIUM:

The classification of networks is also based on the Medium of transmission.
Following are the mediums of transmission:

• Copper wire
• Co-axial cable
• Optical fiber
• Radio waves

All these mediums differ from each other with respect different parameters. These
parameters are speed of transmission, range of the receiver and transmitter computer,
sharing of information, topology, installation & maintenance costs and reliability.
For example the range of radio waves will be much more than an optical fiber.
Similarly other mediums differ from each other and appropriate medium is selected
for the sake of transmission.

4) BY MOBILITY:

The networks are also classified according to their mobility.
In this respect there are two types of networks.

• Fixed networks
• Mobile networks

In these days mobile networks are the hot case. Mobile networks have been emerged
in the last decade. In this regard there are some issues which are attached with the
mobility of networks which are as follows:

• Location and tracking
• Semi persistent connections
• Complex administration and billing as devices and users move around the network.