Chapter 9 – Introduction to Computer Networks Sumita Arora Solution
Short Answer Questions
1. What is a network? What are its goals and applications?
Answer : A network is an interconnected collection of autonomous computers that can share and exchange information.
i) Resource sharing: Through a network, data, software and hardware resources can be shared irrespective of the physical location of the resources and the user.
ii) Reliability: A file can have its copies on two or more computers of the network, so if one of them is unavailable, the other copies could be used. That makes a network more reliable.
iii) Reduced costs: Since resources can be shared, it gently reduces the costs.
iv) Fast communication: With networks, it is possible to exchange information at very fast speeds.
The goal of network is to share data, files and resources.
2. Discuss and compare various types of networks.
Answer: Networks vary widely in their size, complexity and geographical spread. On the basis of geographical spread, networks are classified as:
i) Personal Area Network (PAN): It is the interconnection of information technology devices within the range of individual person, typically within a range of 10 metres.
ii) Local Area Network (LAN): These are computer networks confined to a localised area such as an office, a building or a factory.
iii) Metropolitan Area Network (MAN): These are the computer networks that link computer facilities within a city.
iv) Wide Area Network (WAN): These are the networks spread over large distances, say across countries or even continents.
3. Explain various mostly used topologies.
Answer : Mostly used topologies are:
i) Star Topology: In this topology each workstation is directly linked to a central hub.
Advantages: Can be inexpensive, easy to install and reconfigure and easy to trouble shoot physicals problems.
ii) Bus or linear topology: In this topology, all devices on network are connected to a primary network cable in a single line.
Advantages: Inexpensive, easy to install, simple to understand, easy to extend.
iii) Ring Topology : In this topology all computers are connected in loop. Data travels in ne direction only, from node to node around the ring.
Advantages: All computers have equal excess to network media, easy installation , signals do not degrade much.
iv) Tree topology: In this topology, the shape of network is that of inverted tree with the central root branching and sub-branching to the extremities of the network.
It is hybrid topology of bus and star topologies.
Advantages: point-to-point wiring
v) Mesh topology: in this topology, each node is connected to more than one node to provide an alternative route in the case the host is either down or too busy. It is an extension to P-P network.
Advantages: long distance networking, robust, provides privacy and security, fault diagnosis is easy.
4. Discuss the factors that govern the selection of a topology for a network.
Answer: Factors that govern the selection of a topology for a network are:
• Cruciality of work: How crucial the continuity of work is a very important factor.
• Cost: For a network to be cost effective, one would try to minimize installation cost.
• Flexibility: The topology should allow for easy reconfiguration of the network.
• Future growth: If a network has to grow in future, then topology must support expansion.
• Reliability: The topology chosen for the network should help by allowing the location of the fault to be detected.
5. Which of the following is not a network topology : Star, Mesh, Tree, Bug, Bus?
Answer: Bug is not a network topology.