1. Chapter 1 : Computer Networks.
Lecture 3

2. Network Topologies:
Network Topologies: - The network topology, refers to the arrangement or physical layout of computers, cables, and other components on the network.

3. Network Topologies:
The types of Network Topologies : 1. Bus topology. 2. Star topology. 3. Ring topology. 4. Mesh topology.

4. Bus Topology:
- Bus topology is the most commonly used in Networks. - Bus network is a one-cable topology in which all workstations are connected to a single cable that is terminated at each end. - Signals are broadcasted to all stations, but stations only act on the frames addressed to them.

5. Bus Topology:
- The advantages : 1- It is easy to set-up. 2- Bus topology costs very less. - The disadvantage: - If the cable breaks , it affects the whole network.

6. STAR Topology:
- In a star network each workstation is connected to a single computer location called the hub (the server) using a separate cable. - The design of a star network is easy to modify and troubleshooting can be conducted from a central point (the hub).

7. STAR Topology:
- A star network requires a great deal of cables, which increases its expense and if the hub fails it affect the entire network.

8. STAR Topology: The advantages of the star topology:
1- Easy to connect new nodes or devices. In star topology new nodes can be added easily without affecting rest of the network. Similarly components can also be removed easily.
2- Failure of one node or link doesn’t affect the rest of network. At the same time its easy to detect the failure and troubleshoot it.

9. STAR Topology: The disadvantages:
1- Too much dependency on central device(Hub) has its own drawbacks. If it fails whole network goes down.
2- It requires a great deal of cables, which increases the cost of a network.

10. Ring Topology: A ring network is a closed loop of cable.
Each workstation is connected to two other workstations.
Data is sent from workstation to workstation around the ring in the same direction, passing through workstations until it reaches its destination.

11. Ring Topology:
Each workstation acts as a repeater, resending the message to the next workstation.
The response time of a ring is determined by the number of workstations, i.e. the more workstations, the slower the LAN.

12. Ring Topology:
- The advantage of the ring topology: 1- It is easy to set-up. - The disadvantages are : 1- If a cable break between devices it affects the entire LAN. 2-The cost is another factor. The ring topology usually construes higher implementation costs. 3- Increasing of workstations affecting network performance.

13. Mesh Topology:
In a mesh topology, each computer is connected to every other computer by separate cabling.
- This configuration provides redundant paths throughout the network so that if one cable fails, another will take over the traffic.

14. Mesh Topology:
- These networks are expensive to install because they use a lot of cabling.

15. Mesh Topology:
- The advantages of the mesh topology: 1- If one of the components fails there is always an alternative present. So data transfer doesn’t get affected. 2- Expansion and modification in topology can be done without disrupting other nodes. - The main disadvantage is : - The cost , it is expensive because they need more resources (cables & ports).

16. Advantages and Disadvantages of Network Topologies
Topology
Advantages
Disadvantages
Bus
Cheap. Easy to install.
Difficult to reconfigure.
Break in bus disables
entire network.
Star
Easy to reconfigure.
Fault tolerant.
More expensive than bus.
Ring
Efficient. Easy to install.
Reconfiguration difficult.
Very expensive.
Mesh
Simplest. Most fault tolerant.
Reconfiguration extremely difficult.
Extremely expensive.
Very complex.