Chapter 21 Topologies Chapter 2. 2 Chapter Objectives Explain the different topologies Explain the...

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Transcript of Chapter 21 Topologies Chapter 2. 2 Chapter Objectives Explain the different topologies Explain the...

  • TopologiesChapter 2

  • Chapter ObjectivesExplain the different topologiesExplain the structure of various topologiesCompare different topologies

  • RecallLAN types are Ethernet, Token Ring, Token bus and Fiber Distributed Data Interface (FDDI).OSI layers are Physical, Data Link, Network, Transport, Session, Presentation and Application layerThe factors of network selection criteria are Performance, Reliability and SecurityStandards organization is unit which develops, maintains, improves, amends and revises standards

  • Introducing TopologiesTopology refers to physical or logical arrangement of networkPhysical topologies areSingle NodeBusStarRingMeshTreeHybrid

  • Single Node Topology - ISingle device, at times device called dumb terminal is connected to the serverDevices operates on files from server and returns them back after completing task

  • Single Node Topology - IIAdvantages:

    Easy to install, configure and manage

    Least expensive

    Single cable is required


    Network consists of single device

    Dumb terminal is dependent on server

  • Bus topology - IAll devices are connected to a common cable called trunkMaximum segment length of cable is 200 mMaximum of 30 devices per segment

  • Bus topology - IIServer is at one end and devices are at different positions50 ohm terminator is usedDevices are not responsible for data transmissionNumber of collisions are more Daisy chain method can be used to add more devices

  • Bus topology - IIIAdvantages:

    Installation of devices is easy

    Requires less cable compared to star topology

    Less expensive and works better for smaller networks


    If backbone breaks, entire network gets down

    Difficult to isolate problems

    Limited number of devices

  • Star Topology - IEach device is connected to a central device called hub through cableData passes through hub before reaching destination

  • Star Topology - IIAdvantages:

    Easy to install, configure, manage and expand

    Centralized management

    Addition or removal of device does not affect the whole network


    Requires more cable

    Failure of hub affects entire networkMore Expensive

  • Case Study 1Hyderabad branch of the MoneyMaker bank has built an insurance department in such a way that each device is connected to one another. This department consists of seven agents. It is required that agents should handle only their specific clients since the information is confidential. But in the existing topology the data is not secured. So, Smith, the network administrator, wants to switch over to other topology.

  • Problem Design a new type of network for this department.

  • Suggested SolutionThe current topology implemented by the bank is mesh in which information is shared between different devices. To obtain security of data star network seems to be the best choice. It also provides ease of troubleshooting, centralized management and ease of reconfiguration.

  • Ring Topology - IDevices are connected in a closed loop All devices have equal access to mediaDevice waits for its turn to transmitMost common type is Token Ring

  • Ring Topology - IIAdvantages:

    Data travels at greater speed

    No collisions

    Handles large volume of traffic


    More cabling is required compared to bus

    One faulty device affects the entire network

    Addition of devices affect network

  • Dual Ring TopologyConsists of two independent primary and secondary rings

    Secondary ring is redundant, used only when primary stops functioning

  • Mesh Topology - IUsed in WANs to interconnect LANs Every device is connected to every other deviceUse routers to determine the best path of communication

  • Mesh Topology - IIFull mesh topology All devices are connected to each otherPartial mesh topology - Some devices are connected to only those with whom they exchange most of the data

  • Mesh Topology - IIIAdvantages:

    Improves fault tolerance

    Failure of one link does not affect entire network

    Centralized management is not requiredDisadvantages:

    Difficult to install and manage

    Each link from one device to other requires individual NIC

    Very much expensive

  • Tree Topology - IConnects groups of star networksDevices are wired to root hubRoot hub is connected to second level devicesLowest level devices are smaller computers

  • Tree Topology - IIAdvantages:Easy to add new devicesPoint-to-point wiring for each deviceFault detection is easy

    Disadvantages:Difficult to configureIf backbone breaks, entire network goes downMore expensive

  • Hybrid Topology - ICombines two or more different physical topologiesCommonly Star-Bus or Star-Ring Star-Ring uses Multistation Access Unit (MAU)

  • Hybrid Topology - IIAdvantages:

    Used for creating larger networks

    Handles large volume of traffic

    Fault detection is easy


    Installation and configuration is difficult

    More expensive than other topologies

    More cabling is required

  • Case Study 2MoneyMaker Bank at Mumbai has implemented a star topology in their IT department. All computers are connected to the central switch. In the Loan department, all computers are connected in closed loop format. Network administrator, John wants to connect these two networks so that data can be shared among different departments.

  • ProblemConnect two different departments

  • Suggested SolutionThe administrator can join these two star and ring networks to form a hybrid network with the help of Multistation Access Unit (MAU). It is a centralized hub. Ensure that there is no break in the link between two computers in a ring network and switch in star network is working properly.

  • Summary - INetwork is an interconnection of many communicating entities that are connected for the purpose of data communicationTopology describes the way in which networking devices are connected to each otherPhysical topologies are how the wires are interconnected, while logical topology is how the network behaves and interoperatesDifferent types of topologies are Single Node, Star, Bus, Ring, Mesh, Tree and Hybrid

  • Summary - IIIn a single node topology, just a single device called dumb terminal is connected to the serverBus topology connects each device to a single cable and at either end of the cable terminator is used to remove unsent data from the cableIn star topology, multiple devices are connected to a central connection point known as hub or switch In a ring topology, data travels around the loop in one direction and passes through each device

  • Summary - IIIIn a mesh topology, every device is connected to each and every node in the network with many redundant interconnections at least two paths to and from every node Tree topology connects multiple star networks to other star networks using bus topologyHybrid topology is a combination of different topologies such as Star-Bus or Star-Ring