Bus Networks:
The simplest and easiest topology to implement a bus network (also
known as a liner bus) consists of a single cable to which the client
computers and servers connect.
A bus network has open end. Each PC is connected to the network via a
network card. Each peripheral, such as printers, can also be added to
the network, each connected computer or peripherals is called terminal
or node. Each end of the network is connected by a terminating resistor,
which prevents signal interference. The most common example of this
type of network is Ethernet network.
On
a bus network, the nodes are passive participants, “listening” on the
line and waiting for message address to them. This type of network can
transmit to any other node whenever it wants, each message is broadcast,
along with the recipient’s unique network address. Transmissions are
limited to one computer at a time, so at any given time, one computer is
master of the network and any other are waiting to transmit must wait
until the line is free.
Message on the bus network travel in either direction (“left” to “right”
or “right” to “left). Because the network is based on a single cable,
also called a trunk or backbone the ends of the cable must be equipped
with a device called a terminator.
Bus networks are easy to implement and requires less cabling than other
topologies. In addition, nodes are relatively easy to add and remove.
On the negative side, problem can be difficult such a network and a
break in the trunk cable mean a breakdown in the entire network. It
performance is too slow the network because the node must wait for
longer periods being able to transmit over an open line.
Advantage of BUS Network:
i) Easy to extend terminals
We want to extend any terminal or want to add
workstation to an existing bus network at any point along its length.
More extensive additions can be achieved by adding extra segments
cancelled by a type of signal amplifier called repeater.
ii) Simple wiring layout
As we know that there is single common data path
connecting all terminals. Bus type network decreases the installation
cast because, the bus topology allows a very short cable length to be
used , and lead to a simple, wiring layout and easy to maintain.
iii) Flexible architecture
The bus architecture has an inherent simplicity that
makes it very reliable from every point of view. Because there is a
single cable through which all data passes and to which all terminals
are connected.
Disadvantage of the Bus network:
i) Fault diagnosis is difficult
Fault diagnosis is not a simple matter. In most LANs
bases on a bus control of the network is not centralized in any
particular terminal. This means detection of a fault may be performed
from much point in the work.
ii) Fault isolation is difficult
If any terminal is faulty on a bus, it must be
rectified at the point where the terminal is connected to the network.
Once the fault has been located, the terminal can simply be removed. But
in the star topology a defective terminal can easily be isolated from
the network by removing its connection at the center.
iii) Repeater configuration
When a bus topology type network has its backbone
extended using repeater reconfiguration may be necessary. This may be
involved tailoring cable length, adjusting terminators, etc.
