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CHAPTER LAN Topology. 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. Chapter Modules. Topology: The Bus LAN
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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
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
MODULE The Bus Topology
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.
Bus Network Server Printer Peripheral Device Single Data Bus Workstation Workstation
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
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
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
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
Solution • Collision domains are present only when a hub used • Using switches will eliminate the collision domains
Advantage of Using a Switch WS2 Switch WS3 WS1 LAN 2 (Collision Domain 2) LAN 1 (Collision Domain 1) Occasional Crossover Traffic
Practical Consideration • All popular logical bus networks currently implemented using switches
In Summary • The use of switches in a . network reduces network traffic congestion • Increases the utilization of the bus network
MODULE Bus LAN Practical Implementation: 10Base2
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
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
Topologies • 10Base2 and 10Base5 • Logical bus and Physical bus • 10BaseT • Logical bus and Physical star • 100BaseTx • Logical bus and physical star • Fast Ethernet LAN
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
Components for Building a 10Base2 Network T connector Network Interface Card Thin coaxial cable Terminator
A Typical Installation BNC Jack Thin Coaxial Cable T Connector Terminator Expansion Slots
Practical Implementation Source: Black Box
MODULE Bus LAN Practical Implementation: 10Base5
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
A Simple Implementation Vampire Clamp Thick Coax (10Base5) Transceiver Transceiver 15-pin AUI Connector Client Server
A Practical Implementation Source: Black Box
10Base5 Feeder Connection 10Base 5 Feeder Line 10Base2 Clusters Source: Black Box
MODULE Topology: The Ring LAN
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
Ring LAN Peripheral Device Printer Server WS WS WS
Ring LAN : Practical Implementation Multi-Access Unit (MAU) Or Hub Server WS Physical Star/ Logical Ring
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
Ring LAN Token Server WS WS WS Token carries and delivers the information in the network.
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
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
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
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
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
MODULE Ring LAN Practical Implementation
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
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)
Actual Implementation Hardware Source: Black Box
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
An Actual 4 Mbps Token Ring Implementation Source: Black Box
An Actual 16 Mbps Token Ring LAN Implementation Source: Black Box