Chapter 10 LAN Wiring, Physical Topology, and Interface Hardware Network Interface Card (fig 10.2)(fig 10.2) Ethernet wiring schemes – Thicknet – Thinnet – Twisted-pair

Thick Ethernet Thicknet or 10Base5 bus topology using a large coax cable. External transceiver needed for digital to analog signal conversion and carrier signal detection AUI (attachment unit interface) cable is used to connect a NIC to a transceiver (fig 10.3)(fig 10.3) Pinout of AUI interface: 1 logic ref.9 Collision – 2Collision +10Tx – 3Tx +11Logic ref 4logic ref12 Rx – 5Rx Vdc 6Gnd14logic ref 7N/C15N/C

Thin wire Ethernet Thinnet or 10Base2 (fig 10.5)(fig 10.5) consists of a smaller coax cable bus topology Transceiver function built into BNC NIC. AUI cable not needed BNC T-connector used to connect cable directly to back of computer Cheaper than thicknet terminator – 50 ohm resistor connects center wire in the cable to the outer shield – needed to avoid reflection of signal – Absence causes interference and collision

Twisted-pair Ethernet 10BaseT or 100BaseT (fig 10.6)(fig 10.6) uses an electronic device (hub) that simulates a shared physical cable to connect to each computer via twisted-pair copper wiring Failure in wiring to one computer will not affect the other computers RJ-45 One pair used for Rx; other pair for Tx

Ethernet Standards standardCable typeSpeedMaximum Distance 10 Base5Thick coax10 Mbps500 m 10 Base2Thin coax10 Mbps200 m 10 BaseTTwisted-pair copper 10 Mbps100 m 100 BaseTTwisted-pair copper 100 Mbps100 m 100 BaseFOptical fiber100 Mbps2 km 1000BaseFOptical fiber1000 Mbps

Interoperability Thicknet, Thinnet, and 10BaseT wiring (fig 10.7)schemes use the same standard for frame formats and network access(fig 10.7) possible to mix wiring technologies on a single network (fig 10.8)(fig 10.8)

Topology Paradox Physically, twisted-pair Ethernet uses a star topology. Logically, twisted pair Ethernet functions like a bus. Thus 10BaseT is often called star-shaped bus. Token-ring is sometimes known as a star-shaped ring. A given network technology(eg. Ethernet) determines the logical topology. The wiring scheme determines the physical topology(eg. Physical star, logical ring or bus).