1 Network Topology

2 Introduction 8Physical and Logical Topologies 8Topologies 8Bus 8Ring 8Star 8Extended Star 8Mesh 8Hybrid

3 Physical vs. Logical Topology 8 The actual layout of a network and its media is its Physical Topology 8 The way in which the data access the medium and transmits packets is the Logical Topology 8 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 8Inexpensive to install 8Easy to add stations 8Use less cable than other topologies 8Works well for small networks Disadvantages 8No longer recommended 8Backbone breaks, whole network down 8Limited no of devices can be attached 8Difficult to isolate problems 8Sharing same cable slows response rates

6 Ring Topology

7 Ring Topology (3) Advantages 8 Data packets travel at great speed 8 No collisions 8 Easier to fault find 8 No terminators required Disadvantages 8 Requires more cable than a bus 8 A break in the ring will bring it down 8 Not as common as the bus – less devices available

8 Star Topology

9 Star Topology (3) 8 Advantages 8 Easy to add devices as the network expands 8 One cable failure does not bring down the entire network (resilience) 8 Hub provides centralised management 8 Easy to find device and cable problems 8 Can be upgraded to faster speeds 8 Lots of support as it is the most used 8 Disadvantages 8 A star network requires more cable than a ring or bus network 8 Failure of the central hub can bring down the entire network 8 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) 8 Not common on LANs 8 Most often used in WANs to interconnect LANS 8 Each node is connected to every other node 8 Allows communication to continue in the event of a break in any one connection 8 It is “Fault Tolerant”

CP2073 Networking 13 Mesh Topology (3) Advantages 8 Improves Fault Tolerance Disadvantages 8 Expensive 8 Difficult to install 8 Difficult to manage 8 Difficult to troubleshoot

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 Advantages 8 A single node failure does not bring the network down 8 Most widely implemented topology 8 Network can be added to or changed without affecting other stations Disadvantages 8 Collisions can occur easily 8 Only one device can access the network media at a time

17 Logical Ring 8 Data in a Star Topology can transmit data in a Ring 8 The MAU (Multistation Access Unit) looks like an ordinary Hub, but data is passed internally using a logical ring 8 It is superior to a Logical Bus Hub – see later slide

18 Logical Ring (2)

19 Logical Ring (3) Advantages 8 The amount of data that can be carried in a single message is greater than on a logical bus 8 There are no collisions Disadvantages 8 A broken ring will stop all transmissions 8 A device must wait for an empty token to be able to transmit

20 Summary 8 Bus Topology 8 Ring Topology 8 Star Topology 8 Other Topologies 8 Logical Topologies 8 Questions and Answers

Bibliography 8Source: Web Quests CP2073 Networking 21