1. Network Topology

2. Introduction Physical and Logical Topologies Topologies Bus Ring Star
Extended Star
Mesh
Hybrid

3. Physical vs. Logical Topology
The actual layout of a network and its media is its Physical Topology
The way in which the data access the medium and transmits packets is the Logical Topology
A glance at a network is not always revealing. Cables emerging from a Hub does not make it necessarily a Star Topology – it may actually be a bus or a ring

4. Bus Topology

5. Bus Topology (5) Advantages Inexpensive to install
Easy to add stations
Use less cable than other topologies
Works well for small networks
Disadvantages
No longer recommended
Backbone breaks, whole network down
Limited no of devices can be attached
Difficult to isolate problems
Sharing same cable slows response rates

6. Ring Topology

7. Ring Topology (3) Advantages Disadvantages
Data packets travel at great speed
No collisions
Easier to fault find
No terminators required
Disadvantages
Requires more cable than a bus
A break in the ring will bring it down
Not as common as the bus – less devices available

8. Star Topology

9. Star Topology (3) Advantages Disadvantages
Easy to add devices as the network expands
One cable failure does not bring down the entire network (resilience)
Hub provides centralised management
Easy to find device and cable problems
Can be upgraded to faster speeds
Lots of support as it is the most used
Disadvantages
A star network requires more cable than a ring or bus network
Failure of the central hub can bring down the entire network
Costs are higher (installation and equipment) than for most bus networks

10. Extended Star Topology
A Star Network which has been expanded to include an additional hub or hubs.

11. Mesh Topology (Web)

12. Mesh Topology (2) Not common on LANs
Most often used in WANs to interconnect LANS
Each node is connected to every other node
Allows communication to continue in the event of a break in any one connection
It is “Fault Tolerant”

13. Mesh Topology (3) Disadvantages Advantages Expensive
Difficult to install
Difficult to manage
Difficult to troubleshoot
Advantages
Improves Fault Tolerance
CP2073 Networking

14. Hybrid Topology

15. Logical Bus Modern Ethernet networks are Star Topologies (physically)
The Hub is at the centre, and defines a Star Topology
The Hub itself uses a Logical Bus Topology internally, to transmit data to all segments

16. Logical Bus A single node failure does not bring the network down
Advantages
A single node failure does not bring the network down
Most widely implemented topology
Network can be added to or changed without affecting other stations
Disadvantages
Collisions can occur easily
Only one device can access the network media at a time

17. Logical Ring Data in a Star Topology can transmit data in a Ring
The MAU (Multistation Access Unit) looks like an ordinary Hub, but data is passed internally using a logical ring
It is superior to a Logical Bus Hub – see later slide

18. Logical Ring (2)

19. Logical Ring (3) Advantages Disadvantages
The amount of data that can be carried in a single message is greater than on a logical bus
There are no collisions
Disadvantages
A broken ring will stop all transmissions
A device must wait for an empty token to be able to transmit

20. Summary Bus Topology Ring Topology Star Topology Other Topologies
Logical Topologies
Questions and Answers