Telecommunications and Networking

1. Telecommunications and Networking Network Topologies

2. What is Topology? • Physical or logical map of devices on a network • Physical refers to where each device is physically located and how they are connected to each other • Logical refers to how data is transmitted from one node to another on the network

3. Topology • When the word topology is used by itself, we typically mean the physical topology • Four major topology designs • Bus • Ring • Star • Mesh

4. Not this… Bus

5. Bus Topology Single cable that connects all nodes on a network Each node is connected to a common cable Uses least amount of cable compared to other topologies Often used as a backbone to link other topologies

6. Bus Topology Cont’d. • Requires a terminator at one end and a grounded resistor at the other • If terminator is missing, you experience signal bounce • Supports only one channel for communication

7. Bus Topology Cont’d. • Pros • Inexpensive • Simple to set up • Cons • No fault tolerance • Not scalable • Not practical for more than 10 workstations • Difficult to troubleshoot • Single point of failure • 5-3-3 rule

8. Use a Bus if… Expense is a major issue A temporary network is required until the primary network is completed and you must have communications You want to install a backbone to connect two networks

9. Typical Bus Layout

10. Not this… Ring

11. Ring Topology • Network forms a circle • First node connects to second node • Last node connects to first node • Data is (typically) transmitted clockwise • Unidirectional • Each workstation acts as a repeater • Active topology • Typically Uses TP or Fiber cabling • No fault tolerance

12. Ring Topology Cont’d. • Pros • Organized in terms of data transmission • Design is simple • No need for server/central device • Each node has equal access to resources

13. Ring Topology Cont’d. • Cons • Single point of failure • Each packet must go through every computer to get to the right receiver • Token passing • Not very flexible or scalable • No fault tolerance

14. Use a Ring if… • You have a small network that will not expand • 10 nodes or less • You do not require a central device to manage network

15. Typical Ring Layout

16. Not this… Star

17. Star Topology • Every node is connected to a central device • Single cable only connects two devices; node to central device • Typically built with TP or fiber • Supports maximum of 1024 addressable nodes per segment • More users = slower performance • Uses switches to subdivide segments

18. Star Topology Cont’d. • More fault tolerant than Bus or Ring • Cable problem will only affect the two devices it connects • Failure in central device will affect entire network • Single point of failure • Single workstation problem will only affect that workstation • Flexible and easily scalable

19. Use Star if… You need fault tolerance You need maximum scalability You need/want central network management You need/want easy troubleshooting

20. Star Topology Cont’d. • Pros • Better performance than Bus/Ring • Somewhat fault tolerant • Easily scalable • Centralized control

21. Star Topology Cont’d. • Cons • Single point of failure (central device) • Cost of equipment/installation • More cable required than Bus or Ring • Performance and number of nodes supported dependent on central device

22. Typical Star Layout

23. Not this… Mesh

24. Mesh Topology • Each device is connected to every other device on the network • Extremely fault tolerant • Highest fault tolerance of all topologies • Easy to troubleshoot problems • Not easily scalable

25. Mesh Topology Cont’d. If a data pathway becomes overloaded or breaks, the network can re-route the data over a different pathway Central device is optional EXPENSIVE

26. Use Mesh if… • Constant network connectivity is critical to your business/environment • You have large-scale data transmission • Video surveillance

27. Typical Mesh Layout Full Mesh Partial Mesh

28. Summary • Logical topology represents how the data is transmitted around the network • Physical topology represents the physical layout of the network • Four major types of networks • Bus • Ring • Star • Mesh

29. Summary Cont’d. • Bus • Forms a line • Easy to build • Inexpensive • Not fault tolerant • Single cable connects all nodes • Single point of failure

30. Summary Cont’d. • Ring • Forms a circle • Easy to build • Inexpensive • Not fault tolerant • Single cable connects all nodes • Single point of failure

31. Summary Cont’d. • Star • All nodes connect to a central device • More fault tolerant than Bus or Ring • Easily scalable • Easy to troubleshoot • Expensive • Single point of failure

32. Summary Cont’d. • Mesh • Every device is connected to every other device • Extremely fault tolerant • Easy to troubleshoot problems • Large-scale data transmission • Extremely expensive • Not easily scalable • Difficult to install