Network Topologies
Associate Professor
Department of Computer Science and Engineering
Topics of
Discussion
• Network
• Type of Connections
• Point-to-point
• Multipoint
• Network Topologies
• Physical Topology
• Logical Topology
• Mesh
• Star
• Bus
• Ring
• Hybrid
• Tree
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NETWORK
• A network is a set of devices (often referred to as
nodes) connected by communication links.
• A node can be a computer, printer, or any other device
capable of sending and/or receiving data generated by
other nodes on the network.
• A link can be a cable, air, optical fiber, or any medium
which can transport a signal carrying information.
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Type of connections
1. Point to Point - single transmitter and receiver
• Dedicated link: The term dedicated means that the link carries traffic only
between the two devices it connects.
• Entire capacity of the link is reserved for transmission
2. Multipoint - multiple recipients of single transmission
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Figure 1 Types of connections: point-to-point and multipoint
Dedicated link between two devices
Several devices can use the link
simultaneously or time-shared
(spatially or temporally)
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Topolog
y or more
Two devices connect to a link; two or more links form a
topology.
The topology of a network is the geometric representation of the
relationship of all the links and linking devices/nodes to one
another.
• Physical Topology
• Logical Topology
Physical Topology:
• Refers to the way in which a network is laid out physically
• How devices are actually interconnected with wires and cables.
Logical Topology:
• A logical topology is how devices appear connected to the user.
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Figure 2 Categories of topology
Hybrid topology Tree topology
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Figure 3 A fully connected mesh topology (five devices)
1. Mesh Topology: In a mesh topology, every device has a
dedicated point-to-point link to every other device.
• Node1 is connected to N-1 nodes
N3 • Node2 is connected to N-1 nodes
• ….
• No. of physical links N(N-1) N2 • Node N is connected to N-1 nodes
• In duplex mode: No. of links
N(N-1)/2 N4
LINK
• Every device on the network
must have n – 1 input/output
ports to be connected to the
other n- 1 stations.
N1 N5
Data Packet
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Mesh Topology: Pros &
Cons
Eliminating the traffic problems
Robust
Advantages
Privacy and security
Installation and reconnection are difficult
Wiring can be greater than available space
Disadvantages
Expensive hardware
Practical example: Telephone regional offices
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Figure 4 A star topology connecting four stations
2. Star Topology: In a star topology, each device has a dedicated
point-to-point link only to a central controller (hub)
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Star Topology: Pros &
Cons
Less expensive than mesh topology
Each device needs only one link and one I/O
Advantages port
Easy to install and reconfigure
Less cabling
Robustness
Disadvantage Dependency of the whole topology on one single
point, the hub
The star topology is used in local-area networks (LANs)
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Figure 5 A bus topology connecting three stations
3. Bus Topology: Nodes are connected to the bus cable by drop
lines and taps.
• A drop line is a connection running between the device and the
main cable.
• A bus topology is multipoint.
• Mesh and star are examples of point-to-point connections.
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Bus Topology: Pros &
Cons
Ease of installation
Advantages Less cabling than mesh or star topologies
Difficult reconnection and fault isolation
Signal reflection at the taps can cause
Disadvantages degradation in quality.
A fault or break in the bus cable stops all
transmission
Ethernet LANs can use a bus topology.
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Figure 6 A ring topology connecting six stations
4. Ring Topology: In a ring topology, each device has a dedicated
point-to-point connection with only the two devices on either side
of it.
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Ring Topology: Pros &
Cons
Advantages Easy to install and reconfigure
Fault isolation is simplified
Unidirectional traffic
Disadvantages In a simple ring, a break in the ring (such as a
disabled station) can disable the entire network.
🡪 Troubleshooting is difficult
• Ring topology was prevalent when IBM introduced its local-area
network Token Ring in the middle 1980s.
• Token Ring had a "Star Ring" topology.
• Token ring networks were physically similar to a star topology in
appearance, but logically wired as a Ring Topology.
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Figure 7 A hybrid topology: a star backbone with three bus networks
5. Hybrid Topology: This topology is a collection of two or more
topologies.
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Figure 8 A tree topology
6. Tree Topology: A tree topology (hierarchical topology) is a
collection of star networks arranged in a hierarchy.
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Thank
You
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