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1、Chapter 10LAN Wiring, Physical Topology,And Interface HardwareContent lDescribes:lthe hardware wiring schemes in more detaillnetwork interface cardlmajor hardware component used in various wiring schemeslthe difference between logical topology and physical topologySpeeds of LANs and ComputerslLAN da
2、ta transmission speeds are typically fast relative to CPU speedslthis creates a problemle.g., 100 MHz CPU could execute only one instruction for each bit on a 100Mhz Ethernetlbut several instructions are required for each bitlCPU cant process data at network speed lThe difference between the speed o
3、f the CPU and the speed of the network is a continuous and fundamental problem in networking Network Interface Card (NIC)lComputer systems use special purpose hardware for network connectionlCPU does not deal with the transmissionlUse a Network adapter cardlalso known as network interface card (NIC)
4、 lConnector at back of computer then accepts cable to physical networklThe NIC functions like an I/O devices:it is built for a specific network technology, and handles the details of frame transmission or reception without requiring the CPU to process each bitIllustration of NICArchitecture of NICsF
5、raming/De -framing (Data Buffer)Media Access ControlEncoding e.g., workstations in a lab lConnection multiplexor connects multiple computers to a single transceiverThin Ethernet WiringlUses thin coaxial that is cheaper and easier to install than thick Ethernet coaxial lTransceiver electronics built
6、into NIClNIC connects directly to network medium lCoaxial cable uses BNC connector lCoaxial runs directly to back of each connected computerSecond Generation Ethernet WiringlUsed thinner coaxial cablelFormal name 10Base2lCalled thinnetlUseful when many computers are located close to each other lMay
7、be unreliable - any disconnection disrupts entire net 10Base2 Introduced in 1985, not recommended for installations in networks today. Over thin coaxial cable bus, 称为细缆以太网 Installation was easier because of smaller size, lighter weight, and greater flexibility. -又称廉价以太网 。 不需要外部收发器及收发器电缆。 总线两端也需提供终结电
8、阻。细缆细缆BNC BNC 接头接头 NICNICModern Ethernet WiringlUses a hublFormal name 10Base-TlCalled twisted pair EthernetlReplaces AUI cable with twisted pair cable lReplaces thick coaxial with hub10BASE-TlIntroduced in 1990lcheaper and easier lused unshielded twisted pair (UTP) copper cable rather than coaxial
9、cable.-Category 3, Category 5 or better lStar topology The central connection device is called hub that contained the shared bus lExtended star topology use stars made up of stars lUTP cable uses eight-pin RJ-45 connectors10Base-TWhy Hubs ?lExtension of connection multiplexing concept lSometimes cal
10、led Ethernet-in-a-box lEffectively a very short Ethernet with very long AUI cables lCan be connected into larger EthernetsComparison of Wiring SchemeslThick Ethernet WiringlSeparate transceiver allows computer to be powered off or disconnected from network without disrupting other communication lTra
11、nsceiver may be located in an inconvenient place lFinding malfunctioning transceiver can be hardComparison of Wiring Schemes(2)lThin Ethernet WiringlThin coaxial takes minimum of cable lDisconnecting one computer (or one loose connection) can disrupt entire networklTwisted Pair EthernetlHub wiring c
12、entralizes electronics and connections, making management easier lmost popular because of costLogical and Physical Topologiesl10Base-T network topology is a bus; wiring topology is a star lToken ring network topology is a ring; wiring topology can be a star lDistinguish between logical and physical
13、topologiesEthernet Wiring In An OfficeThe Topology ParadoxlA given network technology can use a variety of wiring schemeslThe technology determines the logical topology, and the wiring scheme determines the physical topologylIt is possible for the physical topology to differ from the logical typeCat
14、egories of WirelFactor of choosing cable:lthe intended data ratellocal condition such as the distance and the amount of electromagnetic noiselanticipated future needs leconomicsSummarylNetwork interface card (NIC) connects computer system to network lNIC operates independently; is fast enough to kee
15、p up with network lMany physical wiring schemes are available for a logical network topology l10Base-T is a logical bus and a physical star ExerciseA six-story office building has 7 adjacent office per floor. Each office contain a wall socket for terminal in the front wall, so the socket from a rect
16、angular grid in the vertical plane, with a separation of 5 m between sockets both horizontally and vertically. Assuming its feasible to run a straight cable between any pair of socket, horizontally vertically or diagonally, how many minimum meters of cable are needed to connect all socket using? And indicate the topology of each network?
