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Ch 05

Ch 05






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    Ch 05 Ch 05 Presentation Transcript

    • Chapter FivePhysical and Logical Topologies
    • 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
    • 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
    • Simple Physical Topologies Figure 5-2: A terminated bus network
    • 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
    • Simple Physical TopologiesStar topology Every node on the network is connected through a central device Figure 5-4: A typical star topology network
    • 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
    • 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
    • Hybrid Physical TopologiesDaisy-Chained A Daisy chain is linked series of devices Figure 5-7: A daisy- chained star-wired bus topology
    • Hybrid Physical TopologiesHierarchical hybrid topology Uses layers to separate devices by priority or function Figure 5-8: A hierarchical ring topology
    • Enterprise-Wide TopologiesEnterprise An entire organizationBackbone networks Serial backbone Distributed backbone Collapsed backbone Parallel backbone
    • 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
    • Enterprise-Wide Topologies Figure 5-10: A distributed backbone connecting multiple LANs
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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
    • Wide Area Network (WAN) TopologiesMesh WAN topology Many directly interconnected locations forming a complex mesh Figure 5-17: Full-mesh and partial-mesh WANs
    • 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
    • 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
    • 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
    • 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
    • EthernetFigure 5-19: CSMA/CD process
    • 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
    • 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
    • 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
    • EthernetFigure 5-21: A switched Ethernet network
    • 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
    • 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
    • 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
    • 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
    • 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
    • Ethernet IIOriginal Ethernet frame type developed byDEC, Intel and Xerox, before IEEE beganto standardize Ethernet Figure 5-24: An Ethernet II frame
    • 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
    • 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
    • Design Considerations for Ethernet Networks Cabling Connectivity devices Number of stations Speed Scalability Topology
    • 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
    • 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
    • Token RingMultistation Access Unit (MAU) Regenerates signals Figure 5-26: Interconnected Token Ring MAUs
    • 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
    • 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
    • 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
    • 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
    • Design Considerations for Token Ring NetworksCablingConnectivity devicesNumber of stationsSpeedScalabilityTopology
    • 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
    • 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
    • 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)
    • 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
    • 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
    • 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
    • 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