Network Topology 1 Introduction 8 Physical and Logical

Network Topology 1

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

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 3

Bus Topology 4

Bus Topology (5) Advantages 8 Inexpensive to install 8 Easy to add stations 8 Use less cable than other topologies 8 Works well for small networks Disadvantages 8 No longer recommended 8 Backbone breaks, whole network down 8 Limited no of devices can be attached 8 Difficult to isolate problems 8 Sharing same cable slows response rates 5

Ring Topology 6

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 7

Star Topology 8

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 9

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

Mesh Topology (Web) 11

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” 12

Mesh Topology (3) Advantages 8 Improves Fault Tolerance Disadvantages 8 Expensive 8 Difficult to install 8 Difficult to manage 8 Difficult to troubleshoot CP 2073 Networking 13

Hybrid Topology 14

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 15

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 16

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 17

Logical Ring (2) 18

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

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