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01 network topologies

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01 network topologies

  1. 1. NETWORK TOPOLOGIESNETWORK TOPOLOGIESThere are three basicThere are three basicconfigurations used to connectconfigurations used to connectcomputers they are thecomputers they are theBusBusRingRingStarStar
  2. 2. Bus topologyBus topology This type of network was widely used in the 1980’sThis type of network was widely used in the 1980’s In this configuration every computer (node) sharesIn this configuration every computer (node) sharesthe networks total bus capacities.the networks total bus capacities. In this configuration adding more computers willIn this configuration adding more computers willreduce the access speed on the network.reduce the access speed on the network. Each computer communicates to other computersEach computer communicates to other computerson the network independently this is referred to ason the network independently this is referred to asPEER-TO-PEER networkingPEER-TO-PEER networking
  3. 3. How a Bus Peer to PeerHow a Bus Peer to PeerNetwork WorksNetwork Works All computers on a network have a distinctAll computers on a network have a distinctaddress just like your house doesaddress just like your house does a message would be send from onea message would be send from onecomputer with the address of anothercomputer with the address of anothercomputer attached to the messagecomputer attached to the message The message is broadcasted to all theThe message is broadcasted to all thecomputers on the network until thecomputers on the network until theaddressed PC accepts the messageaddressed PC accepts the message
  4. 4. How it workedHow it worked The type of wires used for Bus Networks in theThe type of wires used for Bus Networks in the80’s were called Thicknet and Thinnet80’s were called Thicknet and Thinnet A Thicknet cable (very large about 1 inch inA Thicknet cable (very large about 1 inch indiameter usually yellow was hung around a room)diameter usually yellow was hung around a room) Thinnet cables were connected to the PC’s NICThinnet cables were connected to the PC’s NICand a Transceiver. The Transceiver was tappedand a Transceiver. The Transceiver was tappedinto the Thicknet cableinto the Thicknet cable To stop the message from bouncing back andTo stop the message from bouncing back andforward down the wire (known as signal bounce)forward down the wire (known as signal bounce)both ends of the network are terminated with 50Ωboth ends of the network are terminated with 50Ωresistorsresistors
  5. 5. ProblemsProblems One of the main problems with this type ofOne of the main problems with this type ofnetwork is that it is not very fault tolerant, anetwork is that it is not very fault tolerant, abreak or defect in the bus would affect thebreak or defect in the bus would affect thewhole networkwhole network
  6. 6. Ring TopologyRing Topology In Ring topology each node is connected to theIn Ring topology each node is connected to thetwo nearest nodes so the entire network forms atwo nearest nodes so the entire network forms acirclecircle Data only travels in one direction on a RingData only travels in one direction on a Ringnetworknetwork
  7. 7. How this Topology worksHow this Topology works a node has information to send to anothera node has information to send to anothercomputer on the network so it sends thecomputer on the network so it sends theinformation out on the network to the PC it isinformation out on the network to the PC it isconnected to, if the information is for this PC (theconnected to, if the information is for this PC (therecipients NIC address is attached to therecipients NIC address is attached to themessage, which is like putting an address on anmessage, which is like putting an address on anenvelope) then the PC accepts the dataenvelope) then the PC accepts the data otherwise it passes the information on to the nextotherwise it passes the information on to the nextPC by repeating the data back out on the linePC by repeating the data back out on the line This method of repeating the data helps keep theThis method of repeating the data helps keep theintegrity of the data readable by other computersintegrity of the data readable by other computers
  8. 8. How it WorksHow it Works As it is better to have computers take turnsAs it is better to have computers take turnsusing the connecting Data cable, Ringusing the connecting Data cable, Ringtopologies incorporated a system calledtopologies incorporated a system calledToken passingToken passing In this topology, to transmit on the wire yourIn this topology, to transmit on the wire yourcomputer must have control of the token orcomputer must have control of the token orwait for the token to be freewait for the token to be free Larger Token Ring networks use multipleLarger Token Ring networks use multipletokenstokens
  9. 9. Problems and SolutionsProblems and Solutions The drawback to this type of topology is that a singleThe drawback to this type of topology is that a singlemalfunctioning workstation can disable the whole networkmalfunctioning workstation can disable the whole network To make sure all the information is sent the receiving PCTo make sure all the information is sent the receiving PCsends the token back to the sending PC after it hassends the token back to the sending PC after it hasreceived all the datareceived all the data If the sending PC is finished sending it passes the token toIf the sending PC is finished sending it passes the token tothe next PCthe next PC This type of network was also widely used in the 1980’sThis type of network was also widely used in the 1980’s This type of network used Thinnet cable joining nodes.This type of network used Thinnet cable joining nodes. In the mid 1980’s Thinnet cable was replaced byIn the mid 1980’s Thinnet cable was replaced byCategory 3 Ethernet cable capable of handling up toCategory 3 Ethernet cable capable of handling up to10Mbps10Mbps
  10. 10. Star topologyStar topology In a Star topology every node is connectedIn a Star topology every node is connectedthrough a central device such as a Hub,through a central device such as a Hub,Switch or RouterSwitch or Router Compared to a Ring or Bus topology a StarCompared to a Ring or Bus topology a Startopology requires that more thought be puttopology requires that more thought be putinto its setupinto its setupHUB
  11. 11. The Good and Bad of aThe Good and Bad of aStar NetworkStar Network The upside of a star network is that if anyThe upside of a star network is that if anyone cable fails then only the nodeone cable fails then only the nodeconnected on that cable would be affectedconnected on that cable would be affected Another positive point to this type of networkAnother positive point to this type of networkis that it is very simple to join two staris that it is very simple to join two starnetworks together by connecting theirnetworks together by connecting theircentral devices to each othercentral devices to each other
  12. 12. The Good and Bad of aThe Good and Bad of aStar NetworkStar Network As each computer is connected to a centralAs each computer is connected to a centraldevice (Hub) the location of the Hub mustdevice (Hub) the location of the Hub mustbe made as central as possible, so as tobe made as central as possible, so as toreduce cable lengthsreduce cable lengths The drawback to this type of topology is if aThe drawback to this type of topology is if acentral device was to fail then all computerscentral device was to fail then all computersconnected to that device would not be ableconnected to that device would not be ableto see the networkto see the network
  13. 13. What is a Hub?What is a Hub? A hub is usually a small rectangular box,A hub is usually a small rectangular box,often made of plastic, which receives itsoften made of plastic, which receives itspower from an ordinary wall outletpower from an ordinary wall outlet A hub joins multiple computers (or otherA hub joins multiple computers (or othernetwork devices) together to form a singlenetwork devices) together to form a singlenetworknetwork segmentsegment On this network segment, all computers canOn this network segment, all computers cancommunicate directly with each othercommunicate directly with each other
  14. 14. What is a Hub?What is a Hub? EthernetEthernet hubs are by far the most commonhubs are by far the most commontype, but hubs for other types of networkstype, but hubs for other types of networkssuch assuch as USBUSB also existalso exist A hub includes a series ofA hub includes a series of portsports that eachthat eachaccepts a network cableaccepts a network cable Small hubs can network four computersSmall hubs can network four computerstogethertogether They contain four or sometimes five portsThey contain four or sometimes five ports
  15. 15. What is a Hub?What is a Hub? Many times the fifth port is reserved forMany times the fifth port is reserved for"uplink" which is the connecting of one hub"uplink" which is the connecting of one hubto another hub or similar device (joining twoto another hub or similar device (joining twosegments together).segments together). Larger hubs contain eight, 12, 16, and evenLarger hubs contain eight, 12, 16, and even24 ports24 ports
  16. 16. Key Features of HubsKey Features of Hubs Hubs classify as Layer 1 devices in theHubs classify as Layer 1 devices in the OSI modelOSI model OSI stands for :OSI stands for :The Open Systems Interconnection Basic ReferenceThe Open Systems Interconnection Basic ReferenceModelModel At the physical layer, hubs can support little in theAt the physical layer, hubs can support little in theway of sophisticated networkingway of sophisticated networking Hubs do not read any of the data passing throughHubs do not read any of the data passing throughthem and are not aware of their source orthem and are not aware of their source ordestinationdestination
  17. 17. Key Features of HubsKey Features of Hubs Essentially, a hub simply receives incomingEssentially, a hub simply receives incomingpacketspackets, possibly amplifies the electrical, possibly amplifies the electricalsignal, and broadcasts these packets out tosignal, and broadcasts these packets out toall devices on the network - including theall devices on the network - including theone that originally sent the packet!one that originally sent the packet! aa packetpacket is a formatted block of data carriedis a formatted block of data carriedby a computerby a computer networknetwork
  18. 18. Different Types of HubsDifferent Types of Hubs Technically speaking, three different typesTechnically speaking, three different typesof hubs existof hubs existPassivePassiveActiveActiveIntelligentIntelligent
  19. 19. Passive hubsPassive hubs Passive hubsPassive hubs do not amplify the electricaldo not amplify the electricalsignal of incoming packets beforesignal of incoming packets beforebroadcasting them out to the networkbroadcasting them out to the networkActive hubsActive hubs amplify the electrical signal of incomingamplify the electrical signal of incomingpackets back to their original level beforepackets back to their original level beforebroadcasting them back out on the networkbroadcasting them back out on the network
  20. 20. Intelligent hubsIntelligent hubs add extra features to an active hub that areadd extra features to an active hub that areof particular importance to businessesof particular importance to businesses An intelligent hub is typically stackable (builtAn intelligent hub is typically stackable (builtin such a way that multiple units can bein such a way that multiple units can beplaced one on top of the other to conserveplaced one on top of the other to conservespace).space).
  21. 21. Intelligent hubsIntelligent hubs It also typically includes remoteIt also typically includes remotemanagement capabilities viamanagement capabilities via SNMPSNMP andandvirtual LAN (VLAN)virtual LAN (VLAN) support (You cansupport (You canconfigure or check it from a computer that isconfigure or check it from a computer that isconnected to it).connected to it). SNMP-SNMP-Simple Network ManagementSimple Network ManagementProtocolProtocol
  22. 22. What is a Network Switch?What is a Network Switch? AA network switchnetwork switch is a small hardwareis a small hardwaredevice that joins multiple computersdevice that joins multiple computerstogether within onetogether within onelocal area network (LAN)local area network (LAN) Technically, network switches operate atTechnically, network switches operate atlayer two (Data Link Layer) of thelayer two (Data Link Layer) of theOSI modelOSI model
  23. 23. Network SwitchNetwork Switch Network switches appear nearly identical toNetwork switches appear nearly identical tonetwork hubsnetwork hubs, but a switch generally, but a switch generallycontains more "intelligence" (and a slightlycontains more "intelligence" (and a slightlyhigher price tag) than a hubhigher price tag) than a hub Unlike hubs, network switches are capableUnlike hubs, network switches are capableof inspecting dataof inspecting data packetspackets as they areas they arereceived, determining the source andreceived, determining the source anddestination device of that packet, anddestination device of that packet, andforwarding it appropriatelyforwarding it appropriately
  24. 24. Network SwitchNetwork Switch By delivering each message only to theBy delivering each message only to theconnected device it was intended for, aconnected device it was intended for, anetwork switch conservesnetwork switch conservesnetwork bandwidthnetwork bandwidth and offers generallyand offers generallybetter performance than a hubbetter performance than a hub
  25. 25. What is a Router?What is a Router? RoutersRouters are physical devices that joinare physical devices that joinmultiple wired or wireless networks togethermultiple wired or wireless networks together Technically, a wired or wireless router is aTechnically, a wired or wireless router is aLayer 3Layer 3 gatewaygateway, meaning that the, meaning that thewired/wireless router connects networkswired/wireless router connects networkstogethertogether A Gateway is a device that acts like aA Gateway is a device that acts like asecurity guard and only allows data in or outsecurity guard and only allows data in or outif it has the right networkif it has the right network headersheaders
  26. 26. RoutersRouters Home “networkers” often use an Internet ProtocolHome “networkers” often use an Internet Protocol(IP) wired or wireless router(IP) wired or wireless router IP is the most common OSI network layer protocolIP is the most common OSI network layer protocol Protocols are the rules governing the transfer ofProtocols are the rules governing the transfer ofdata information, it can also be compared to howdata information, it can also be compared to howhumans use languages (to get your point acrosshumans use languages (to get your point acrossyou must talk in the same language as the personyou must talk in the same language as the personyou are speaking to).you are speaking to).
  27. 27. RoutersRouters An IP router such as a DSL or cable modemAn IP router such as a DSL or cable modemareare broadband routersbroadband routers and joins the homesand joins the homeslocal area network (LAN)local area network (LAN) to theto thewide-area network (WAN)wide-area network (WAN) of the Internetof the Internet A Broadband Router is a device that allowsA Broadband Router is a device that allowsmultiple PC’s to access the Internet usingmultiple PC’s to access the Internet usingonly one address.only one address.

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