2 ObjectivesDescribe the basic and hybrid LAN physical topologies, and their uses, advantages and disadvantages.Describe the backbone structures that form the foundation for most LANs
3 Simple Physical Topologies Physical topology: physical layout of nodes on a networkFour fundamental shapes:BusRingStarMeshMay create hybrid topologiesTopology integral to type of network, cabling infrastructure, and transmission media used
4 Why we need a topology Choosing one topology over another can impact : type of equipment the network needscapabilities of the equipmentnetwork’s growthway a network is managed
6 Simple Physical Topologies A Bus topology consists of a single cable—called a backbone— connecting all nodes on a network without intervening connectivity devices
7 Bus (continued)Devices share responsibility for getting data from one point to anotherTerminators stop signals after reaching end of wirePrevent signal bounceInexpensive, not very scalableDifficult to troubleshoot, not fault- tolerant
8 Bus Advantages Disadvantage Works well for small networks Easy to installRelatively inexpensive to implementManagement costs can be highNetwork disruption when computers are added or removedA break in the cable will prevent all systems from accessing the network.Difficult to troubleshoot
10 Simple Physical Topologies Ring topologyEach node is connected to the two nearest nodes so the entire network forms a circleOne method for passing data on ring networks is token passingData travels around the networkTraffic flows in one directionSlow performanceOne workstation goes down; whole network goes downNetwork is highly dependent
11 Ring Advantages Disadvantage Cable faults are easily located, making troubleshooting easierRing networks are moderately easy to installExpensiveRequires more cable and network equipment at the startExpansion to the network can cause network disruptionA single break in the cable can disrupt the entire network
13 Simple Physical Topologies Star topologyEvery node on the network is connected through a central device called hub or switch.
14 Any single cable connects only two devices Star (continued)Any single cable connects only two devicesCabling problems affect two nodes at mostRequires more cabling than ring or bus networksMore fault-tolerantEasily moved, isolated, or interconnected with other networksScalableSupports max of 1024 addressable nodes on logical network
15 Star Advantages Disadvantage Good option for modern networks Low startup costsEasy to manageOffers opportunities for expansionMost popular topology in use; wide variety of equipment availableHub is a single point of failureRequires more cable than the bus
17 Simple Physical Topologies Mesh Topology: Each computer connects to every other.High level of redundancy.Rarely used.Wiring is very complicatedCabling cost is highTroubleshooting a failed cable is trickyA variation hybrid mesh – create point to pointconnection between specific network devices, oftenseen in WAN implementation.
18 Mesh Advantages Disadvantage Robust There is the advantage of privacy or securityThe network can be expanded without disruption to current usesPoint to point links make fault identification and fault isolation easyRequires more cable than the other LAN topologiesComplicated implementationInstallation and reconnection are difficult.Sheer bulk of wiring can be greater than the available space can accommodateExpensive
19 Hybrid Physical Topologies One example of Hybrid Topology is Tree topologyTree topology: is a combination of Bus and Star topology.It consists of groups of star-configuredworkstations connected to a linear bus backbone cable.If the backbone line breaks, the entiresegment goes downAn example of this network could becable TV technology
20 Choosing a Topology BUS network is small network will not be frequently reconfiguredleast expensive solution is requirednetwork is not expected to grow muchSTARit must be easy to add/remove PCsit must be easy to troubleshootnetwork is largenetwork is expected to grow in the futureRINGnetwork must operate reasonably under heavy loadhigher speed network is required