[internet]
[internet service] [classification network]
[network architecture] [network topology]
NETWORK TOPOLOGY
What is a network
topology?
§A network topology
refers to
i.The layout of the computers and devices
in a communications network or
ii.The configuration of a network that
consists of cables, computers, and other peripherals.
§It describes the physical and logical
layout of the network.
What is a physical
topology?
§The physical topology of
a network refers to the configuration of cables, computers, and other
peripherals.
What is a logical
topology?
§The logical topology of
a network refers to the architecture, that is the way in which the network
appears to the devices that use it.
COMPUTER NETWORK TERM
§Node – any device that is connected to a
network.
§Client
– a node that requests and uses resources available from other nodes.
§Server – A nodes that share resources
with other nodes.
Host
– Any computer that provides services and connection to other computers on a
network
§Switch – central node that coordinate the flow
of data by sending messages directly between sender and receiver nodes.
§Hub – The
device that provides a common central connection point for nodes on network.
§Network interface cards
(NIC) – expansion cards located within
the system unit that connect a computer to a network.
TYPES OF NETWORK TOPOLOGY
Three (3) basic types of network
topology:
i.Star Network.
ii.Bus Network.
iii. Ring Network.
BUS NETWORK TOPOLOGY
A bus network consists of a single central
cable (backbone/trunk), to which all computers and
other devices connect (node).
§The bus is the
physical cable that connects the computers and
other devices.
§The bus in a bus network transmit
data, instructions, and information as a series
of signal.
Those signals are sent as electrical
pulses that travel along the length of the cable in both directions
Each devices is connected to the
single bus
cable through T-Connector.
HOW IT TRANSMIT THE DATA
A terminator is required at each end of the bus
cable to prevent the signal from bouncing
back
and forth on the bus cable.
When a sending device transmits
data, the
address of the receiving device is
included
with the transmission.
If the device address does not match the
intended address for the data, the device
ignores the data.
If the data does match the device address, the
data is accepted.
All devices receive the data but only the
receiving device accept them.
ADVANTAGE
.
Bus networks are inexpensive and easy to install.
2.
Computers and other devices can be attached
and detached at any point on the bus
without
disturbing the rest of the network.
3.
Failure of one device usually does not affect the
rest of the bus network.
DISADVANTAGE
.
There might be disruption when computer or
other devices are added or removed.
2.
Because all systems on the network connect to
a single cable or backbone, a break in the
cable
will prevent all systems from accessing the
network.
3.
It is difficult to identify the problem if the entire
network shut down.
RING TOPOLOGY
On a ring network,
a cable forms a closed loop
(ring) with all computers and devices
arranged
along the ring.
HOW DATA TRANSMIT
Data transmitted on a ring network
travels from
device to device around the entire ring, in one
direction (clockwise
or counterclockwise)
Token
passing is
one method for sending data
around a ring
Each device takes a turn sending and receiving
information
through the
use of a token.
The token along with any data is sent from the
first device to the second device which extracts the
data addressed to it and adds any data it wishes
to send.
Then second device passes the token and data
to
the third device, etc. until it comes back around to
the first device again.
Only the device with the token is allowed to
send
data . All other devices must wait for the token to
come to them.
ADVANTAGE
The
transmission of data is relatively
simple as packets travel in one direction
only.
2.
Cable faults are easily located, making
troubleshooting easier.
3. The uses of token passing enables all devices in
a ring topology to share the network resources
fairly.
DISADVANTAGE
1.
A failure in any cable or device breaks the
loop and can take down the entire network.
2.
Data packets must pass through every computer
therefore, this makes it slower.
3.
A ring network can span a larger distance than a
bus network, but it is more difficult to
install.
STAR NETWORK TOPOLOGY
All the computers and other devices
on the
network connect to a central
device, thus forming
a star.
Two types of devices that provide a common
central connection point to all the other devices
on the network are a hub and a switch.
HUB/SWITCH
The device that provides a common
central
connection point for other devices on a
network.
All data that transfers from one device to
another passes through the hub or
switch.
The
hub takes a signal that comes from any device
and passes it along to all
the other devices in the network.
ADVANTAGE
If
one device fails, only that device is affected.
2.
Devices can be added to or removed from
network with little or no disruption.
3. Easy to troubleshoot and isolate
problem
DISADVANTAGE
.
If the hub or switch fails, the entire network will
be inoperable.
2.
Requires more cable than most of the other
topologies.
3.
More expensive because of the cost of the
hub/switch.