Physical Topologies

1. Physical Topologies • It refers to the way in which a • network is laid out physically • It is the geometric representation of relationship of all links and linking • devices (usually called as nodes) • connected to one another -K. M. THANVI

2. Types There are four basic types of network topologies Mesh topology Star topology Bus topology Ring topology

3. Mesh Topology • Every device has a dedicated point to point link to every other device • A fully connected mesh network has n(n-1)/2 physical channels to link n devices and to accommodate this links each device require (n-1) I/O ports

4. Figure shows 6 nodes connected with mesh topology

5. Advantages • Dedicated link • Robust • Privacy and security • Fault identification and isolation Disadvantages • Large amount of cabling and i/o ports are required • Installation and reconnection is difficult • Sheer bulk of wiring can be more than available space • Hardware required can be expensive Applications • telephone regional office • Wide area network

6. Star Topology -Each device has a point to point link only to the central controller , usually called as hub -Controller act as ‘Exchange’ -When device 1 wants to send data to device 2; First sends the data to hub. Which then relays the data to the other connected device.

7. Figure shows 5 nodes connected with mesh topology

8. Advantages • less expensive than mesh • easy installation and reconfiguration • Robustness • Fault identification and isolation Disadvantages • Though cabling required is less compared to mesh , but still more cables are required as each node should be connected to central hub. • If hub fails , all attached nodes are disabled • expensive Applications • LAN and High speed LAN

9. Bus Topology • -Mesh and star are point to point whereas bus is point to multipoint • In this one long cable act as a backbone cable to link all devices on network • nodes are connected ton bus cable by drop lines and taps • DROP LINE: Connection running between device and main cable • TAP : A tap is connector that either splices into main cable or punctures the sheathing of cable to create a contact with metallic core

10. Figure shows different nodes Connected with bus topology

11. Advantages • ease of installation • less cabling • less expensive Disadvantages • Fault isolation and reconnection is difficult • Signal reflection at taps cause degradation • Fault or break in the bus cable stops all transmission Applications • most computer motherboard

12. Ring Topology -point to point connection only with the devices on the either side -a signal is passed along the ring from device in one direction until it reaches the destination - It make use of token ring technology

13. Figure shows four nodes Connected with ring topology

14. Advantages • ease of installation and reconfiguration • fault detection and isolation is easy Disadvantages • unidirectional traffic • break in ring can disable entire network Applications • office building and school campus

15. Connecting devices

16. Different connecting devices used are • hub • repeater • bridge • switch • router • gateway

17. HUB

18. REPEATERS

19. BRIDGE

20. SWITCH

21. ROUTER

22. GATEWAY