TYPES OF NETWORK
TOPOLOGIES
Network Topology
 Network topology is the arrangement of the various elements
(links,nodes, etc.) of a computer network.
 Physical Topology is the placement of the various components of
a network, including device location and cable installation.
 Node is either a connection point, a redistribution point, or a
communication endpoint.
 Link is the means of connecting one location/node to another for
the purpose of transmitting and receiving digital information.
Importance of Network Topology
Avoids randomization in setting up of network.
Impacts performance
Impacts cost of cabling
Network topology is a factor in determining media type, used
to cable the network.
Some access methods can work only with specific topologies.
Types of Network Topology
BUS
STAR
RING
MESH
HYBRID (Star ring, Tree)
BUS TOPOLOGY
Features: Bus Topology
Bus topology is a network setup in which
each computer and network device are
connected to a single main cable or backbone.
One of the computers in the network
typically acts as the computer server.
Configuration: Bus Topology
Working: Bus Topology
The computers that send data also attach address of
the destination computer with the data. All computers
connected to the bus receive the data but only that computer
accepts it whose address matches the address attached with
data.
In this topology only one computer at a time can send
a data therefore the speed of network reduces as the number
of computers attached to the bus increases.
Applications: Bus Topology
Ethernet systems use bus topology.
Bus networks work best with a limited number of
devices.
Classroom and labs use bus topology.
Advantages: Bus Topology
It is easy to set-up and extend bus network.
Cable length required for this topology is the least
compared to other networks.
Bus topology is relatively inexpensive.
Linear Bus network works well in small networks.
Disadvantages: Bus Topology
Limit on central cable length and no. Of nodes that can be connected.
Dependency on central cable can lead to whole network breaking down if it
encounters a problem.
Proper termination is needed to dump signals. Therefore, use of terminators
is must.
Difficulty in detecting and troubleshooting fault at individual stations.
Efficiency reduces, as the number of devices connected increases.
Unsuitable for networks with heavy traffic.
STAR TOPOLOGY
Features: Star Topology
In this arrangement computers are connected to a single hub.
The hub is the central node and acts as a repeater for data flow.
The hub acts as a server and the peripheral devices act as
clients.
Every node has its own dedicated connection to the hub i.e.
the devices are not directly linked to one another.
Star topology can be used with twisted pair, Optical Fibre.
Configuration: Star Topology
Working: Star Topology
In a star topology, each device has a dedicated point-to-point
link only to a central controller, usually called a hub.
All the traffic that traverses the network passes through the
cental hub.
Controller acts as an exchange: If one device wants to send data
to another, it sends the data to the controller, which then sends
the data to the other connected device.
Central hub re-sends message either to all the computers (in
broadcast network) or only to the destination computer (in
switched network).
Applications: Star Topology
High speed LAN use star
topology with a central hub.
Advantages: Star Topology
 Hub can be upgraded easily.
 East to troubleshoot
 Easy to setup and modify without disturbing the rest of the
network.
 Robustness
 Lest cabling than Mesh
 Fast performance with few nodes and low network traffic.
 Easy fault identification & isolation.
 Multiple cable types supported by hub
 Centralized monitoring and management are possible.
Disadvantages: Star Topology
High cost of installation.
Performance is based on the hub, i.e., it depends on
its capacity.
Dependency on one single point, the hub.
Increased devices and traffic can make the
connection slow.
RING TOPOLOGY
Features: Ring Topology
Computer network configuration where the devices are
connected to each other in a circular shape.
Forms a ring as each computer is connected to another
computer, with the last one connected to the first. There are exactly
two neighbours for each device.
When a device sends data, it must travel through each device
on the ring until it reaches its destination. Every node is a critical link.
There is no server computer present, all nodes work as server & repeat
the signal.
Number of repeaters are used and the transmission is
unidirectional. Date is transferred in a sequential manner i.e. Bit by bit.
Configuration: Ring Topology
Working: Ring Topology
Each node connects to exactly two other nodes, performing single
continuous pathway for signals through each node- a ring. Data travels from
node to, with each node along the way handling every packet.
Some ring network do ring token passing. A short message called
token is passed around a ring until a computer wishes to send information to
other computers.
That computer modifies token, adds electronic address and data and
send it around the ring. Each computer in sequence receives the token and
next computer until either the electronic address matches the address of a
computer or the token returns to its origin. The receiving computer returns a
message to the sender indicating that message has been received.
Applications: Ring Topology
This topology can be found in peer-to-peer networks in which
machine manages both information processing and the distribution of
data files.
It is not widely popular in terms of usability but it can be found
in schools or office buildings.
Ring topology was prevalent when IBM introduced its LAN
Token Ring. Today, need for higher speed LANs has made this topology
less popular.
Advantages: Ring Topology
•Transmitting network is not affected by high traffic or by adding
more nodes.
•Cheap to install and expand
•Provides equal access for all computers.
•Fault isolation is simplified in single ring
•Performance is even despite many users.
•Provides an orderly network in which every device has access to
the token and can transmit.
•No one computer can monopolize the network
Disadvantages: Ring Topology
•Troubleshooting is difficult in ring topology.
•Adding or deleting the computers disturbs the
network activity.
•Failure of one computer disturbs the whole
network.
MESH TOPOLOGY
Features: Mesh Topology
A network setup where each computer
and network device is interconnected with one
another, i.e., every node has a direct point-topoint connection to every other node, allowing
for most transmissions to be distributed.
Types: Mesh Topology
Fully Mesh
Every computer in the network has a connection to each of the
other computers in that network. No. of connections in this network is
calculated using the formula, n(n-l)|2n is no. of computers in network.
Partially Mesh
At least two of the computers in the network have connections
to multiple other computers in that network.
Configuration: Mesh Topology
Working: Mesh Topology
Mesh networks relay message using either a flooding
technique or a routing technique. With routing, the message
is propagated along a path by hopping from node to node
until it reaches its destination.
To ensure all its paths’ availability , the network must
allow for continuous connections and must reconfigure itself
around broken paths, using self healing algorithms, that allow
a routing-based network to operate when a node breaks
down.
Applications: Mesh Topology
WANs, most notably the Internet, employ
mesh routing
The XO-1 laptop, also known as the One
Laptop per Child (OLPC) uses Mesh Networking.
FabFi a low-cost wireless networking system
Analysis: Mesh Topology
Advantages
Robust because if one connection fails, the others remain intact.
High security since data travels along a dedicated connection
Diadavantages
Expensive, since requires a lot of cables.
Connections redundant as there are several different paths for
data to travel from one node to another.
No. of connecting grows quadratically with no. of nodes, as per
the formula
Hybrid Topologies
Features: Hybrid Topology
Hybrid networks use combination of any two or more topologies,
in such a way that the resulting networks does not exhibit one of the
standard topologies (e.g., bus, star, ring, mesh)
A hybrid topology is always produced when two different basic
network topologies are connected.
Two common examples are: Star-Ring network & Star-Bus
network.
Hybrid Topology
Advantages
Reliable
Scalable
Flexible
Effective
Disadvantages
Complexity of design
Costly Hub
Costly Infrastructure
Types: Star Bus (Tree) Hybrid Topology
Has a root node and all other nodes are connected to it forming
a hierarchy.
Also called hierarchical topology and should at least have three
levels to the hierarchy.
Essentially a combination of bus and star topology. In this, no. of
Star networks are connected using Bus.
This main cable seems like main stem of a tree, and other star
networks as the branches.
Applications: Tree Topology
Ideal if workstations are located in groups
Use in Wide Area Network.
An example of this network could be cable TV
technology.
Other examples are in dynamic tree based wireless
networks for military, mining and otherwise mobile
applications.
Advantages: Tree Topology
•Best alternative when Star and Bus topologies can’t be
implemented individually for reasons related to scalability.
•Expansion of Networks possible and easy.
•Easy management & maintenance.
•Error detection and correction easy.
•Each segment is provided with dedicated point-to-point wiring to
the central hub.
•If one segment is damaged, other segments are not affected.
Disadvantages: Tree Topology
• Because of its basic structure, tree topology. Relies
heavily on the main bus cable, which, if breaks whole
network gets crippled
• Scalability of the network depends on the type of cable
used.
• As more and more nodes and segments are added, the
maintenance becomes difficult
Considerations when choosing a Topology
Cost
Length of cable needed
Future growth
Cable type
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