Page 129 - DCAP516_COMPUTER_SECURITY

Unit 10: Network Concepts

1. Star Topology: All devices connected with a Star setup communicate through a central Notes
Hub by cable segments. Signals are transmitted and received through the Hub. It is the
simplest and the oldest and all the telephone switches are based on this. In a star topology,
each network device has a home run of cabling back to a network hub, giving each device
a separate connection to the network. So, there can be multiple connections in parallel.
Figure 10.1: Star Topology

Advantages

(i) Network administration and error detection is easier because problem is isolated to
central node.
(ii) Networks runs even if one host fails.

(iii) Expansion becomes easier and scalability of the network increases.
(iv) More suited for larger networks.
Disadvantages
(i) Broadcasting and multicasting is not easy because some extra functionality needs to
be provided to the central hub.
(ii) If the central node fails, the whole network goes down; thus making the switch
some kind of a bottleneck.
(iii) Installation costs are high because each node needs to be connected to the central
switch.

2. Bus Topology: The simplest and one of the most common of all topologies, Bus consists of
a single cable, called a Backbone that connects all workstations on the network using a
single line. All transmissions must pass through each of the connected devices to complete
the desired request. Each workstation has its own individual signal that identifies it and
allows for the requested data to be returned to the correct originator. In the Bus Network,
messages are sent in both directions from a single point and are read by the node (computer
or peripheral on the network) identified by the code with the message. Most Local Area
Networks (LANs) are Bus Networks because the network will continue to function even if
one computer is down. This topology works equally well for either peer to peer or client
server.

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