Chapter 10 LAN Wiring, Physical Chapter 10 LAN Wiring, Physical

Topology, and Interface HardwareTopology, and Interface Hardware Network Interface Card (fig 10.2)Ethernet wiring schemes

– Thicknet– Thinnet– Twisted-pair

Thick EthernetThick 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) Pinout of AUI interface:

1 logic ref. 9 Collision –2 Collision + 10 Tx –3 Tx + 11 Logic ref4 logic ref 12 Rx –5 Rx + 13 + 12Vdc6 Gnd 14 logic ref7 N/C 15 N/C

Thin wire EthernetThin wire Ethernet Thinnet or 10Base2 (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 Twisted-pair Ethernet

10BaseT or 100BaseT (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-45One pair used for Rx; other pair for Tx

Ethernet StandardsEthernet Standardsstandard Cable type Speed Maximum

Distance

10 Base5 Thick coax 10 Mbps 500 m

10 Base2 Thin coax 10 Mbps 200 m

10 BaseT Twisted-pair copper

10 Mbps 100 m

100 BaseT Twisted-pair copper

100 Mbps 100 m

100 BaseF Optical fiber 100 Mbps 2 km

1000BaseF Optical fiber 1000 Mbps

InteroperabilityInteroperability

Thicknet, Thinnet, and 10BaseT wiring (fig 10.7)schemes use the same standard for frame formats and network access

possible to mix wiring technologies on a single network (fig 10.8)

Topology ParadoxTopology 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) .