1. Overview Network Topologies Transmission Media (Cable Types)Infromation Technology Unit - AFHQ 2

2. Network Topologies Token Ring Linear Bus Star Tree (Expanded Star) Considerations When Choosing a TopologyInfromation Technology Unit - AFHQ 3 3. Token Ring Uses a ring topology, wheredevices in the network arelogically arranged in a closedring/circle. It also uses a token passingprotocol, so that a machinecan only use the networkwhen it has control of theToken. This ensures that there are nocollisions because only onemachine can use the networkat any given time.Infromation Technology Unit - AFHQ 4 4. It is considered to be an active topology, as computersin the ring re-transmit the packet they receive to thenext computer in the ring. The token is a special packet of data, if a computerwants to send data onto the network, it has to waituntil it has possession of the token, else it passes it onto the next computer.Infromation Technology Unit - AFHQ 5 5. Upon start up, the machine with the highest MAC addressis chosen as the 'Active Monitor, and all other machinesbecome 'Standby Monitors'. Active Monitors are in charge of monitoring the networkand performing Ring Polling, by which other computersfind their Nearest Active Upstream Neighbor (NAUN).Infromation Technology Unit - AFHQ 6 6. Advantages Very orderly network where every device has access to the token andthe opportunity to transmit. Performs better than a star topology under heavy network load. Can create much larger network using Token Ring. Does not require network server to manage the connectivitybetween the computers. Disadvantages One malfunctioning workstation or bad port in the MAU can createproblems for the entire network. Moves, adds and changes of devices can affect the network. Network adapter cards and MAU's are much more expensive thanEthernet cards and hubs. Much slower than an Ethernet network under normal load.Infromation Technology Unit - AFHQ 7 7. Linear BusInfromation Technology Unit - AFHQ 8 8. A linear bus topology consists of a main run of cable with aterminator at each end. All nodes (file server, workstations,and peripherals) are connected to the linear cable. A signal from the source travels in both directions to allmachines connected on the bus cable until it finds theintended recipient. If the machine address does not matchthe intended address for the data, the machine ignores thedata. Uses CSMA/CD, or CSMA/CA to manage and minimizecollisions.Infromation Technology Unit - AFHQ 9 9. Linear bus The type of network topology in which all of the nodes of the networkare connected to a common transmission medium which has exactlytwo endpoints (also commonly referred to as the backbone, or trunk) all data transmitted between nodes in the network is sent over thebackbone and can be received by all nodes in the networksimultaneously. Distributed bus The type of network topology in which all of the nodes of the networkare connected to a common transmission medium which has morethan two endpoints (that are created by adding branches to the mainsection of the transmission medium). Notes: The linear bus topology is sometimes considered to be a special case of thedistributed bus topology i.e., a distributed bus with no branching segments. The physical distributed bus topology is sometimes incorrectly referred to as aphysical tree topology.Infromation Technology Unit - AFHQ 10 10. Advantages of a Linear Bus Topology Easy to connect a computer or peripheral to a linear bus. Requires less cable length than a star topology. Disadvantages of a Linear Bus Topology Entire network shuts down if there is a break in the maincable. Terminators are required at both ends of the backbone cable. Difficult to identify the problem if the entire network shutsdown. Not meant to be used as a stand-alone solution in a largebuilding.Infromation Technology Unit - AFHQ 11 11. Star Topology Each computer in a star topology is connected with its owncable (typically twisted-pair cable) to a port on the hub orsome central component unit.Infromation Technology Unit - AFHQ 12 12. Star LANs also use the same type of wait-and-listenstrategy to access data or send data as characterized by thebus topology. Advantages Better performance. Passing of Data Packet through unnecessary nodes is prevented bythis topology. This topology induces a huge overhead on the centralhub, however if the central hub has adequate capacity, then veryhigh network utilization by one device in the network does not affectthe other devices in the network. Isolation of devices. Each device is inherently isolated by the link that connects it to thehub. This makes the isolation of the individual devices fairlystraightforward. This isolated nature also prevents any non-centralizedfailure to affect the network.Infromation Technology Unit - AFHQ 13 13. Benefits from centralization. Easy to increase the capacity of the central hub, addadditional devices to the star (can scale the network veryeasily). The central nature also allows the inspection trafficthrough the network. Simplicity. The topology is easy to understand, establish, and navigate. Unobtrusive. Minimal effect on users.Infromation Technology Unit - AFHQ 14 14. Disadvantages. High dependence of the system on the functioning ofthe central hub. Performance and scalability of the network also dependon the capabilities of the hub. Number of connections in the star also depends on thehow many connections the hub can support.Infromation Technology Unit - AFHQ 15 15. Tree Topology (Expanded Star) Tree topology is a combination of Bus and Startopology.Infromation Technology Unit - AFHQ 16 16. It consists of groups of star-configured workstations connected to alinear bus backbone cable. 5-4-3 Rule Between any two nodes on the network there can only be a maximumof 5 segments, connected through 4 repeaters/concentrators. Inaddition, only 3 of the segments may be populated (trunk) segments ifthey are made of coaxial cable. Advantages Point-to-point wiring for individual segments. Supported by several hardware and software venders. Disadvantages Overall length of each segment is limited by the type of cabling used. If the backbone line breaks, the entire segment goes down. More difficult to configure and wire than other topologies.Infromation Technology Unit - AFHQ 17 17. Considerations When Choosing aTopology Money. A linear bus network may be the least expensive way to install anetwork; you do not have to purchase concentrators. Cable Length. The linear bus network uses shorter lengths of cable. Future growth. With a star topology, expanding a network is easily done by addinganother concentrator. Cable type. The most common cable in schools is unshielded twisted pair, which ismost often used with star topologies.Infromation Technology Unit - AFHQ 18 18. Topology SummeryInfromation Technology Unit - AFHQ 19 19. Transmission Media Twisted Pair Coaxial Cable Optical fiberInfromation Technology Unit - AFHQ 20 20. Twisted PairApplications Most common medium Telephone network Between house and local exchange (subscriber loop) Within buildingsTo private branch exchange (PBX) For local area networks (LAN)10Mbps or 100MbpsInfromation Technology Unit - AFHQ 21 21. Pros Cheap Easy to work withCons Low data rate Short rangeInfromation Technology Unit - AFHQ 22 22. Shielded Twisted Pair (STP) Metal braid or sheathing thatreduces interference More expensive Harder to handle (thick, heavy) Unshielded Twisted Pair (UTP) Ordinary telephone wire Cheapest Easiest to install Suffers from external EMinterferenceInfromation Technology Unit - AFHQ 23 23. Cross-Over Cable Crossover cables have pairs of wires that crisscross. Thisallows for two devices to communicate at the same time. Used to connect two like devices, like, Routers and computers. Switches and hubs.Infromation Technology Unit - AFHQ 24 24. Straight-Through Cable. Straight-through cables are primarily used forconnecting unlike devices. Between (Computers and Routers) and (Switches and Hubs).Infromation Technology Unit - AFHQ 25 25. Rollover Cable (Console cable). Rollover cables essentially have one end of the cable wiredexactly opposite from the other. Used to connect Computers and devices to a routersconsole port.Infromation Technology Unit - AFHQ 26 26. Category Maximum data rate Usual applicationCAT 1 Less than 1 Mbps analog voice (plain old telephone service)Integrated Services Digital Network Basic RateInterface in ISDN Doorbell wiringCAT 2 4 Mbps Mainly used in the IBM Cabling System for tokenring networksCAT 3 16 Mbps Voice and data on 10BASE-T Ethernet (certify16Mhz signal)CAT 4 20 Mbps Used in 16Mbps Token RingOtherwise not used muchCAT 5 100 Mbps 100 Mbps TPDDI155 Mbps asynchronous transfer mode (certify100 Mhz signal)Infromation Technology Unit - AFHQ 27 27. Crimping ToolsInfromation Technology Unit - AFHQ 28 28. Coaxial CableInfromation Technology Unit - AFHQ 29Applications Most versatile medium Television distribution Ariel to TV Cable TV Long distance telephone transmission Can carry 10,000 voice calls simultaneously Being replaced by fiber optic Short distance computer systems links Local area networks 29. Two types of coaxial cable are used for networkingcomputers: Thicknet A heavy-gauge coaxial cable that is fairly inflexible and requiresspecial equipment (over and above a simple network card) toconnect the computer to the network backbone. Thinnet. Thinnet (RG-58 coaxial cable) was the cable of choice at one time because ofits relative ease of installation and its low cost. Thinnet LANs employ a bus topology, where a T-connector is attached toeach computers network card. The computers are then chained togetherusing appropriate lengths of cable. Thinnet installations require that eachend of the network be terminated, and terminators are placed on thedownside T-connector of the computers that reside on either end of thenetwork.Infromation Technology Unit - AFHQ 30 30. Optical Fiber Optical fibers are based entirely on the principle oftotal internal reflection.Infromation Technology Unit - AFHQ 31 31. Fiber Modes. Single Mode. Multi Mode.Infromation Technology Unit - AFHQ 32 32. Infromation Technology Unit - AFHQ 33 33. Overview 5-4-3 rule In the Ethernet protocol, a signal sent out over thecollision domain must reach every part of the networkwithin a specified length of time. Thus comes the IEEE Way/5-4-3 rule, which states thatIn a given collision domain, only 5 segments, 4repeaters, and 3 populated segments may exist.. The populated segments are user segments, and theunpopulated ones are known as link.Infromation Technology Unit - AFHQ 34 34. The rule only applies to shared-access Ethernetbackbones. The rule does not apply to switchedEthernet because each port on a switch constitutes aseparate collision domain. Point-to-point Network The simplest topology is a permanent link betweentwo endpoints. There are two types of such networks. Permanent Switched Circuit switched Packet switchedInfromation Technology Unit - AFHQ 35 35. The eight steps The most important part of troubleshooting anyproblem is to divide the tasks of problem resolutioninto a systematic process of elimination. Cisco hasbroken this process into eight steps:Define the problem. Gather detailed information. Consider probable cause for the failure. Devise a plan to solve the problem. Implement the plan.Infromation Technology Unit - AFHQ 36 36. Observe the results of the implementation. Repeat the process if the plan does not resolve theproblem. Document the changes made to solve the problem. In case of networks, Identify the topology. Identify any special features. Work from the bottom up.Infromation Technology Unit - AFHQ 37 37. QUESTIONSInfromation Technology Unit - AFHQ 38