1. Data Communication Networks
Lec 3

2. Physical Structure
Point-to-point
Multipoint

3. Point-to-point

4. Multipoint

5. Physical Topology
Refer to way in which network is laid out physically.
Mesh
Star
Bus
Ring

6. Mesh topology
In mesh, every device has a dedicated point-to-point link to every other device.
Link carries traffic only between the two devices it connects.

7. Advantages of Mesh Topology
Each connection carries its own data load, eliminate traffic problems.
robust
Privacy and security

8. Disadvantages of Mesh topology
Amount of cabling.
Installation and reconnection.
Expensive.

9. Mesh topology

10. Star topology
Each device has dedicated point-to-point link only to a central controller, using a hub.
Does not allow direct traffic between devices.
All communication is through controller.

11. Advantages of Star Topology
Each device needs one link and one port to connect to any number of others.
Easy to install and reconfigure.
Less cabling.
Robustness, one link fails, only that is affected.
Hub can monitor link problems and bypass defective links.

12. Disadvantage of Star Topology
Dependency on a single point, the hub.

13. Star Topology

14. Bus Topology
One long cable acts as a backbone to link all devices in the network.
Nodes are connected to the bus cable by drop lines and taps.

15. Advantages of Bus Topology
Ease of installation.
Less cabling.

16. Disadvantages of Bus topology
Difficult to add new devices.
Signal reflection at the taps cause degradation in quality.
Adding new device require modification or replacement of the backbone.
Damaged area causes noise.

17. Bus topology

18. Ring topology
Each device has a dedicated point-to-point connection with only the two devices on either side.
Signal is passed along the ring in one direction, from device to device, until reaches destination.
repeater

19. Advantages of Ring topology
Easy to install and reconfigure.
Device is linked to only immediate neighbors, add or remove require changing two connections.

20. Disadvantages of Ring Topology
Break in ring , can disable entire network.

21. Ring topology

22. Hybrid topology

23. Network Models Networks are created by different entities.
Standards are needed.
OSI model and internet model.
OSI(open systems interconnection) define 7 layer network.
Internet model defines 5 layer network.

24. Categories of Networks
LAN
MAN
WAN

25. Local Area Network(LAN)
Privately owned and link the devices in a single office, building or campus.
Designed to allow resources to shared personal computers e.g. hardware, printer data etc.
Engineering workstations or accounting PCs.
Servers to clients.
Restrictions for number of users.
LAN topologies.
Data rates

26. LAN

27. Wide area Network(WAN)
Provides long distance transmission of data.
Large geographical area that comprise of country or even whole world.
Switched WAN and point-to-point WAN.
Switched WAN connects the end systems, usually a router that connects to LAN or WAN.
Point-to- point WAN is a leased line from telephone or cable TV , that connects to ISP.

28. WAN

29. Metropolitan Area Network(MAN)
Lies between size of LAN and WAN.
Covers the area inside city or a town.

30. Internetwork LAN , WAN and MAN are not seen in isolation.
Mostly are interconnected, form an internetwork or a internet.

31. internetworks