Roll no: 04
BS (Hons) 7th semester
The Islamia University of
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Diagram of Ring topology
Diagram of Bus Topology
Advantages of Bus topology
Disadvantages of Bus Topology
Diagram of Star topology
Advantages/Disadvantages of Star topology
Diagram of Mesh Topology
Advantages/Disadvantages of Mesh Topology 23
Two types of logical Topology
AN INTRODUCTION TO NETWORKING
Network topology is the study of the arrangement or
mapping of the elements (links, nodes, etc.) of a
network, especially the physical (real) and logical
(virtual) interconnections between nodes A local area
network (LAN) is one example of a network that exhibits
both a physical topology and a logical topology.
Any particular network topology is determined only by
the graphical mapping of the configuration of physical
and/or logical connections between nodes. LAN
Network Topology is, therefore, technically a part of
The way in which the
connections are made is called the topology of the
The structure of the network is divided into the
physical topology and the logical topology.
refers to the configuration of the cables, computers,
and other peripherals.
Devices are connected from one to another to form
a ring shape.
Each host is connected to the next and the last
node is connected to the first.
A data token1 is used to grant permission for each
computer to communicate.
Easy to install and wire.
Because every computer is given equal access to the
token, no one computer can monopolize the network.
Requires more cable than a bus topology.
If one computer fails it can affect the whole network.
It is difficult to identify the problem if the entire network
The bus topology is often used when a network
installation is small, simple, or temporary.
All hosts are connected to the backbone cable in a
Advantages of the Bus
There are several advantages to a bus topology:
The bus is simple, reliable in very small networks, easy to
use, and easy to understand.
The bus requires the least amount of cable to connect
the computers together and is therefore less expensive
than other cabling arrangements.
It is easy to extend a bus. Two cables can be joined into
one longer cable with a BNC barrel connector, making a
longer cable and allowing more computers to join the
A repeater can also be used to extend a bus; a repeater
boosts the signal and allows it to travel a longer distance.
Disadvantages of the Bus
A bus topology is commonly subject to the following disadvantages:
Heavy network traffic can slow a bus considerably. Because any
computer can transmit at any time, and computers on most bus
networks do not coordinate with each other to reserve times to
transmit, a bus network with a lot of computers can spend a lot of its
bandwidth (capacity for transmitting information) with the computers
interrupting each other instead of communicating. The problem only
gets worse as more computers are added to the network.
Each barrel connector weakens the electrical signal, and too many
may prevent the signal from being correctly received all along the
It is difficult to troubleshoot a bus. A cable break or malfunctioning
computer anywhere between two computers can cause them not to
be able to communicate with each other. A cable break or loose
connector will also cause reflections and bring down the whole
network, causing all network activity to stop.
In a star topology, all the cables run from the computers to a central
location, where they are all connected by a device called a hub.
Stars are used in concentrated networks, where the endpoints are
directly reachable from a central location; when network expansion is
expected; and when the greater reliability of a star topology is
All hosts are connected to a single point of concentration.
Usually uses a hub3 or switch4 as a center node.
Range limits are about 100 meters from the hub
Data on a star network passes through the hub or concentrator
before continuing to its destination.
It is easy to modify and add new computers to a star network
without disturbing the rest of the network.
If one node or workstation (beside the middle node) goes
down, the rest of the network will still be functional.
The center of a star network is a good place to figure out
where the network faults are located.
You can use several cable types in the same network if the
hub you have can handle multiple cable types.
Requires more cable than a bus topology.
If the middle node goes down , then the entire network goes
It is more expensive than because all cables must be
connected to one central point.
Tree topology is a combination of Bus and Star topology.
This particular type of network topology is based on
a hierarchy of nodes. The highest level of any tree network
consists of a single, 'root' node, this node connected either
a single (or, more commonly, multiple) node(s) in the level
below by (a) point-to-point link(s). These lower level nodes are
also connected to a single or multiple nodes in the next level
down. Tree networks are not constrained to any number of
levels, but as tree networks are a variant of the bus network
topology, they are prone to crippling network failures should a
connection in a higher level of nodes fail/suffer damage. Each
node in the network has a specific, fixed number of nodes
connected to it at the next lower level in the hierarchy, this
number referred to as the 'branching factor' of the tree. This
tree has individual peripheral nodes.
The mesh topology is distinguished by having
redundant links between devices. A true mesh
configuration has a link between each device in the
network. As you can imagine, this gets
unmanageable beyond a very small number of
devices. Most mesh topology networks are not true
Each host is connected to all the other hosts.
Increased reliability since there are multiple paths for
each node to take.
Increased speed since shortcuts have been created by
add more cables/links.
The cost of cabling all the hosts together is expensive
and time consuming.
refers to the method for passing information
TWO TYPES OF LOGICAL TOPOLOGIES:
Broadcast - This type of logical topology works on a
first come, first serve basis. The first in line gets to
be the first to be sent. Each host sends its data to
all other hosts. The Ethernet is a good example of
a broadcast logical topology.
Token Passing - This type of logical topology
controls access by passing a token1. Each host
can only send data when it has the token1.
Cisco Networking Academy Program CCNA 1 and 2 Lab
Companion, Revised Third Edition. Cisco Press,
2005. ISBN: 158731498.
Computer in business P.62-65
Network Topology: http://www.theapaws.net/network_topology.htm
The Home PC: http://thehomepc.com/networks/topology.htm