CHAPTER LAN Topology

1. CHAPTER LAN Topology

2. Chapter Objectives • Describe the characteristics of different LAN topologies • Bus, ring, star and mixed topologies • Compare and contrast the topologies with one another with respect to their relative advantages and disadvantages

3. Chapter Modules • Topology: The Bus LAN • Bus LAN Practical Implementations • Topology: The Ring LAN • Ring LAN Practical Implementation • Topology: The Star LAN • Topology: Mixed Topologies

4. END OF Chapter Introduction

5. MODULE The Bus Topology

6. Questions • What are physical and logical topologies? • What is a collision domain? • How can the bus network be implemented in practice? • How is it frequently implemented in practice? • How could collisions be reduced? • Is it possible to reduce the danger of a cable breakdown? Explain.

7. Bus Network Server Printer Peripheral Device Single Data Bus Workstation Workstation

8. Bus LAN Transmission Logic • Listen to the bus for traffic • If no traffic is detected, then transmit • Otherwise, if the bus is busy with traffic, wait for a random period of time before attempting to transmit again • Repeated attempts will be made until the bus is found free

9. Collision of Data • Two workstations may find the bus free at the same time • Both would transmit at the same time • Collision of data occurs • Both workstations will now wait for a random period of time before attempting to transmit again

10. Advantages of Bus LAN • Cabling is simple and easy to install in a local setup • Based on well established standards • IEEE 802.3 • Also known as the Ethernet standard

11. Disadvantages of a Bus LAN • Sharing of a single data bus • When the traffic increases the performance deteriorates • Waiting period may reach unacceptable lengths of time under heavy data traffic • Cable fault results in the entire LAN becoming inoperative

12. Solution • Collision domains are present only when a hub used • Using switches will eliminate the collision domains

13. Advantage of Using a Switch WS2 Switch WS3 WS1 LAN 2 (Collision Domain 2) LAN 1 (Collision Domain 1) Occasional Crossover Traffic

14. Practical Consideration • All popular logical bus networks currently implemented using switches

15. In Summary • The use of switches in a . network reduces network traffic congestion • Increases the utilization of the bus network

16. END OF MODULE

17. MODULE Bus LAN Practical Implementation: 10Base2

18. Logical and Physical Topology • Logical topology • Logical functioning of a network • Physical topology • Physical configuration of a network • Example: • For ease of implementation, a logical bus network may be physically configured as a star network

19. Major Bus Implementation Architectures • 10Base2 • 10Base5 • 10BaseT • 100BaseTX • 1000BaseT • Although this represents a logical bus topology, it is implemented physically in the form of a star topology

20. Topologies • 10Base2 and 10Base5 • Logical bus and Physical bus • 10BaseT • Logical bus and Physical star • 100BaseTx • Logical bus and physical star • Fast Ethernet LAN

21. 10Base2 • 10 Mbps LAN • Based on a well established standard • Ethernet 802.3 standard • Configured using thin coaxial cables • Sometimes called the 10Base2 cables • Very popular in the past • In recent times, the popularity has declined • Due to emergence of fast Ethernet • Due to the popularity of 100BaseTX

22. Components for Building a 10Base2 Network T connector Network Interface Card Thin coaxial cable Terminator

23. A Typical Installation BNC Jack Thin Coaxial Cable T Connector Terminator Expansion Slots

24. Practical Implementation Source: Black Box

25. END OF MODULE

26. MODULE Bus LAN Practical Implementation: 10Base5

27. 10Base5 • 10 Mbps • It is also based on a popular standard known as the Ethernet 802.3 standard • Thick coaxial cables are used for configuring the network in this case • The cables are less maneuverable • In practice, the 10Base5 network is often used as a feeder connection to 10Base2 and/or other types of networks

28. A Simple Implementation Vampire Clamp Thick Coax (10Base5) Transceiver Transceiver 15-pin AUI Connector Client Server

29. A Practical Implementation Source: Black Box

30. 10Base5 Feeder Connection 10Base 5 Feeder Line 10Base2 Clusters Source: Black Box

31. END OF MODULE

32. MODULE Topology: The Ring LAN

33. Questions • Is there a collision domain in this case? • How is a ring network implemented in practice? • Is the ring network technologically superior to the bus network? • Is a ring or bus LAN used widely in practice? • Explain

34. Ring LAN Peripheral Device Printer Server WS WS WS

35. Ring LAN : Practical Implementation Multi-Access Unit (MAU) Or Hub Server WS Physical Star/ Logical Ring

36. Practical Implementation Considerations of a Ring Network • Based on a central hub • Multi-Access Unit (MAU) • Multi-Station Access Unit (MSAU) • Logical ring • Wiring inside the hub • Physical star • Resembles in appearance only • Ring bypass • Bypass the Non-functioning workstation

37. Ring LAN Token Server WS WS WS Token carries and delivers the information in the network.

38. Characteristics of the Ring Transmission Logic • Data path • A ring that connects the workstations and the servers • Transmission logic • Based on a token that circulates around the ring • The token carries the data • Protocol • The popular IEEE 802.5 standard

39. Ring LAN Advantages • Orderly transmission of data • Guarantees an opportunity for each workstation to transmit • Performance deterioration is not as critical as in the case of the bus LAN • Data traffic congestion is minimized • Gradual decline in performance with increased load • A good topology for larger LANs • Used as a backbone in large enterprise networks

40. Ring LAN Disadvantages • Difficult to implement the network as a ring • This drawback is overcome by physically implementing the network in the form of a star • Relatively higher cost of configuring the ring LAN

41. Current Status of the Ring LAN • First introduced to overcome the speed limitation of the older bus networks • 16 Mbps ring LANs as opposed to the 10 Mbps bus LANs • Recent advancement in bus LANs in the 100 Mbps speed range • Resulted in the decline in the popularity of the ring LANs • However, 100 Mbps Token-Ring products are now available

42. Questions • Is there a collision domain in this case? • How is a ring network implemented in practice? • Is the ring network technologically superior to the bus network? • Is a ring or bus LAN used widely in practice? • Explain

43. END OF MODULE

44. MODULE Ring LAN Practical Implementation

45. Practical Ring LAN Characteristics • The practical implementation is based on the IEEE 802.5 standard • The newer Ring LANs operate at a speed of 100 mbps • Many current Ring LANs operate at 16 Mbps • The older ring LANs operate at 4 Mbps • As a hub-based LAN, it is easy to implement and manage

46. Hardware Required to Implement a Basic Token Ring LAN • Token-ring NIC • Cable • IBM Type 1 or 2 or 3 • UTP as needed by the design • Multi-station Access Unit (MAU) • Multi-station Access Unit (MSAU) • Smart Multi-station Access Unit (SMAU)

47. Actual Implementation Hardware Source: Black Box

48. A Typical Token Ring LAN Configuration Special IBM Connectors Multi-Station Access Unit IBM Type 1 Twisted Pair 9-Pin AUI Connectors Client Client Server

49. An Actual 4 Mbps Token Ring Implementation Source: Black Box

50. An Actual 16 Mbps Token Ring LAN Implementation Source: Black Box