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Ch 05

  1. 1. Chapter FivePhysical and Logical Topologies
  2. 2. ObjectivesDescribe the basic and hybrid LAN physicaltopologies, their uses, advantages, anddisadvantagesDescribe a variety of enterprise-wide andWAN physical topologies, their uses,advantages, and disadvantagesCompare the different types of switching usedin data transmissionUnderstand the transmission methods, orlogical topologies, underlying Ethernet, TokenRing, LocalTalk, and FDDI networks
  3. 3. Simple Physical TopologiesPhysical topology Physical layout of a networkA Bus topology consists of a single cable—calleda bus— connecting all nodes on a network withoutintervening connectivity devices Figure 5-1: Bus topology network
  4. 4. Simple Physical Topologies Figure 5-2: A terminated bus network
  5. 5. Simple Physical TopologiesRing topology Each node is connected to the two nearest nodes so the entire network forms a circle One method for passing data on ring networks is token passingActive topology Each workstation transmits data Figure 5-3: A typical ring network
  6. 6. Simple Physical TopologiesStar topology Every node on the network is connected through a central device Figure 5-4: A typical star topology network
  7. 7. Hybrid Physical TopologiesHybrid topology Complex combination of the simple physical topologiesStar-wired ring Star-wired topologies use physical layout of a star in conjunction with token ring-passing data transmission method Figure 5-5: A star- wired ring topology network
  8. 8. Hybrid Physical TopologiesStar-wired bus In a star-wired bus topology, groups of workstations are star-connected to hubs and then networked via a single bus Figure 5-6: A star-wired bus network topology
  9. 9. Hybrid Physical TopologiesDaisy-Chained A Daisy chain is linked series of devices Figure 5-7: A daisy- chained star-wired bus topology
  10. 10. Hybrid Physical TopologiesHierarchical hybrid topology Uses layers to separate devices by priority or function Figure 5-8: A hierarchical ring topology
  11. 11. Enterprise-Wide TopologiesEnterprise An entire organizationBackbone networks Serial backbone Distributed backbone Collapsed backbone Parallel backbone
  12. 12. Enterprise-Wide TopologiesSerial backbone Two or more hubs connected to each other by a single cableDistributed backbone Hubs connected to a series of central hubs or routers in a hierarchy Figure 5-9: A simple distributed backbone network
  13. 13. Enterprise-Wide Topologies Figure 5-10: A distributed backbone connecting multiple LANs
  14. 14. Enterprise-Wide TopologiesCollapsed backbone Uses a router or switch as the single central connection point for multiple subnetworks Figure 5- 11: A collapsed backbone network
  15. 15. Enterprise-Wide TopologiesParallel Backbone Collapsed backbone arrangement that consists of more than one connection from central router or switch to each network segment Figure 5- 12: A parallel backbone network
  16. 16. Enterprise-Wide TopologiesMesh networks Routers are interconnected with other routers, with at least two pathways connecting each router Figure 5-13: An example of a mesh network
  17. 17. Wide Area Network (WAN) TopologiesPeer-to-peer topology WAN with single interconnection points for each location Dedicated circuits Continuous physical or logical connections between two access points that are leased from a communication provider Figure 5-14: A peer-to-peer WAN
  18. 18. Wide Area Network (WAN) TopologiesRing WAN topology Each site is connected to two other sites so that entire WAN forms a ring pattern Figure 5-15: A ring-configured WAN
  19. 19. Wide Area Network (WAN) TopologiesStar WAN topology Single site acts as the central connection point for several other points Figure 5-16: A star- configured WAN
  20. 20. Wide Area Network (WAN) TopologiesMesh WAN topology Many directly interconnected locations forming a complex mesh Figure 5-17: Full-mesh and partial-mesh WANs
  21. 21. Wide Area Network (WAN) TopologiesTiered WAN topology Sites connected in star or ring formations are interconnected at different levels, with interconnection points organized into layers Figure 5-18: A tiered WAN topology
  22. 22. Logical TopologiesRefers to the way in which data aretransmitted between nodesDescribes the way: Data are packaged in frames Electrical pulses are sent over network’s physical mediaLogical topology may also be called networktransport system
  23. 23. SwitchingComponent of network’s logical topology thatdetermines how connections are createdbetween nodes Circuit switching Connection is established between two network nodes before they begin transmitting data Message switching Establishes connection between two devices, transfers information to second device, and then breaks connection Packet switching Breaks data into packets before they are transmitted
  24. 24. EthernetCarrier Sense Multiple Access with CollisionDetection (CSMA/CD) The access method used in Ethernet Collision In Ethernet networks, the interference of one network node’s data transmission with another network node’s data transmission Jamming Part of CSMA/CD in which, upon detection of collision, station issues special 32-bit sequence to indicate to all nodes on Ethernet segment that its previously transmitted frame has suffered a collision and should be considered faulty
  25. 25. EthernetFigure 5-19: CSMA/CD process
  26. 26. EthernetOn an Ethernet network, an individualnetwork segment is known as a collisiondomain Portion of network in which collisions will occur if two nodes transmit data at same timeData propagation delay Length of time data take to travel from one point on the segment to another point
  27. 27. EthernetDemand priority Method for data transmission used by 100BaseVG Ethernet networks Demand priority requires an intelligent hub Figure 5-20: CSMA/CD versus demand priority
  28. 28. EthernetTraditional Ethernet LANs, called sharedEthernet, supply fixed amount of bandwidththat must be shared by all devices on a segmentSwitch Device that can separate network segments into smaller segments, with each segment being independent of the others and supporting its own trafficSwitched Ethernet Newer Ethernet model that enables multiple nodes to simultaneously transmit and receive data over logical network segments
  29. 29. EthernetFigure 5-21: A switched Ethernet network
  30. 30. EthernetGigabit Ethernet 1 Gigabit Ethernet Ethernet standard for networks that achieve 1- Gbps maximum throughput 10 Gigabit Ethernet Standard currently being defined by IEEE 802.3ae committee Will allow 10-Gbps throughput Will include full-duplexing and multimode fiber requirements
  31. 31. EthernetPadding Bytes added to data portion of an Ethernet frame to make sure this field is at least 46 bytes in sizeEthernet frame types: IEEE 802.3 (“Ethernet 802.2” or “LLC”) Novell proprietary 802.3 frame (or “Ethernet 802.3”) Ethernet II frame IEEE 802.3 SNAP frame
  32. 32. IEEE 802.3 (“Ethernet 802.2” or “LLC”) Default frame type for versions 4.x and higher of Novell NetWare network operating system  Sometimes called LLC frame  In Novell’s lexicon, this frame is called Ethernet 802.2 frame Figure 5-22: An IEEE 802.3 frame
  33. 33. IEEE 802.3 (“Ethernet 802.2” or “LLC”)Service Access Point (SAP) Identifies node or internal process that uses LLC protocolFrame Check Sequence (FCS) This field ensures that data are received just as they were sentCyclical Redundancy Check (CRC) Algorithm used by FCS field in Ethernet frames
  34. 34. Novell Proprietary 802.3 (or “Ethernet 802.3”)Original NetWare frame typeAlso called: 802.3 Raw Ethernet 802.3 frame Figure 5-23: A Novell proprietary 802.3 frame
  35. 35. Ethernet IIOriginal Ethernet frame type developed byDEC, Intel and Xerox, before IEEE beganto standardize Ethernet Figure 5-24: An Ethernet II frame
  36. 36. IEEE 802.3 SNAPAdaptation of IEEE 802.3 and Ethernet IISNAP stands for Sub-Network Access Protocol Figure 5-25: An IEEE 802.3 SNAP frame
  37. 37. Understanding Frame TypesLearning about networks is analogous tolearning a foreign language, with the frame typebeing the language’s syntax Just as you may know the Japanese word for go but how to use it in a sentence, you may know all about the IPX/SPX protocol but not how devices handle itAutosense Feature of modern NICs that enables a NIC to automatically sense what types of frames are running on a network and set itself to that specification
  38. 38. Design Considerations for Ethernet Networks Cabling Connectivity devices Number of stations Speed Scalability Topology
  39. 39. LocalTalkLogical topology designed by AppleComputer, Inc.Uses a transmission method called CarrierSense Multiple Access/CollisionAvoidance (CSMA/CA)A teleconnector is a transceiver used on aLocalTalk networkMacintosh version of TCP/IP is calledMacTCP
  40. 40. Token RingToken Ring networks use the token passingroutine and a star-ring hybrid physicaltopologyThe 100-Mbps Token Ring standard is knownas High-Speed Token Ring (HSTR)On a Token Ring network, one workstation,called the active monitor, acts as thecontroller for token passing
  41. 41. Token RingMultistation Access Unit (MAU) Regenerates signals Figure 5-26: Interconnected Token Ring MAUs
  42. 42. Token RingControl Access Unit (CAU) Connectivity device used on a Token Ring networkLobe Attachment Module (LAM) Device that attaches to a CAU to expand the capacity of that device
  43. 43. Token RingToken Ring networks with STP cabling may use atype 1 IBM connectorA DB-9 connector is another type of connectorfound on STP Token Ring networks Figure 5-27: Type 1 IBM and DB-9 Token Ring connectors
  44. 44. Token RingMedia filter Device that enables two types of cables or connectors to be linkedToken Ring media filter Enables DB-9 cable and type 1 IBM cable to be connected Figure 5-28: A Token Ring media filter
  45. 45. Token RingToken Ring switching Like Ethernet networks, Token Ring networks can take advantage of switching to better utilize limited bandwidthToken Ring frames IEEE 802.5 Token Ring frame IBM Token Ring frame Figure 5-29: An IBM Token Ring frame
  46. 46. Design Considerations for Token Ring NetworksCablingConnectivity devicesNumber of stationsSpeedScalabilityTopology
  47. 47. Fiber Distributed Data Interface (FDDI)Logical topology whose standard was originally specifiedby ANSI in mid-1980s and later refined by ISO Figure 5-30: A FDDI network
  48. 48. Asynchronous Transfer Mode (ATM)Logical topology that relies on a fixed packetsize to achieve data transfer rates up to 9953MbpsThe fixed packet in ATM is called a cellA unique aspect of ATM technology is that itrelies on virtual circuits
  49. 49. Asynchronous Transfer Mode (ATM)ATM uses circuit switching, which allowsATM to guarantee a specific quality ofservice (QOS)ATM technology can be integrated withEthernet or Token Ring networks through theuse of LAN Emulation (LANE)
  50. 50. Chapter SummaryA physical topology is the basic layout of a networkPhysical topologies are categorized into threefundamental geometric shapes: bus, ring, and starFew LANs use the simple physical topologies intheir pure formHubs that service star-wired bus or star-wired ringtopologies can be daisy-chained to form a morecomplex hybrid topologyHierarchical hybrid topology can designate hubs atdifferent layers to perform different functions
  51. 51. Chapter SummaryCabling that connects each hub is called thebackboneIn mesh networks, routers are interconnected withother routers so at least two pathways connect eachnodeWAN topologies use LAN and enterprise-widetopologies as building blocks, but add morecomplexityNetwork logical topologies encompass a set of rulesspecifying which data are packaged and transmittedover network media
  52. 52. Chapter SummarySwitching is a component of a network’s logicaltopology that manages the filtering andforwarding of packets between nodes on anetworkEthernet is a networking technology and is by farthe most popular logical topology for LANs todayEthernet follows a network access method calledCSMA/CDOn heavily trafficked Ethernet networks,collisions are not uncommonA switch is a device that can separate a networkinto smaller segments, each independent of eachother and supporting its own traffic
  53. 53. Chapter SummaryToken Ring networks currently run at either 4 or 16Mbps, as specified by IEEE 802.5Token Ring networks use the token-passing routineand a star-ring hybrid physical topologyFDDI is a networking standard originally specified byANSI in mid-1980s and later refined by ISOATM relies on a fixed packet size to achieve datatransfer rates up to 9953 MbpsATM relies on virtual circuits to determine theoptimal path between sender and receiver