Mumbai University > Information Technology > Sem4 > Computer Networks

Marks: 5M

Year: May 2014

Topology refers to the way in which the network of computers is connected. Each topology is suited to specific tasks and has its own advantages and disadvantages. The choice of topology is dependent upon type and number of equipment being used, planned applications and rate of data transfer required, response time, and cost. Topology can also be defined as the geometrically interconnection pattern by which the stations (nodes/computers) are connected using suitable transmission media (which can be point-to-point and broadcast).

In a network of computers, the transmission media provide the physical path for communication among the nodes and the manner in which the nodes are geometrically interconnected is known as its topology.

These two interrelated issues largely influence the function and performance of a network There are 4 main types of Topologies. They are

• Bus
• Tree
• Ring
• Star

Choice of Topology:

There are many factors in choosing an appropriate topology. They are

• Reliability
• Expandability
• Performance

These factors are to be considered collectively as the overall task is to design a Local Area Network.

There are four alternative media that can be used:

• Twisted Pair
• Baseband Co-axial Cable
• Broadband Co-axial Cable
• Optical Fiber

1) Twisted Pair: This approach is not in use now, because Twisted Pair offers much less data rates.

2) Baseband Co-Axial Cable: This media offers digital signalling. Ethernet makes use of this technique.

3) Broadband Co-Axial Cable: This media is used in cable television systems. But this media is costly, difficult to install and fault isolation and identification are very difficult. This media is not used any more.

4) Optical Fiber: This media is very costly. Due to the cost factor and availability of alternative schemes, this media is also no longer used.

For bus topology, baseband co-axial cable is compatible to give the best result. For star topology, twisted pair and optical fiber are used. For ring topology, the scheme provides the best throughput when provided with very high speed links.

Choice of Transmission Medium

The choice is determined by a number of factors. They are

• Capacity: to support the expected network traffic.
• Reliability: to meet the requirements for availability.
• Types of data supported: Tailor-made to suit the application.
• Environmental Scope: To provide service over a wide range of environments required