Transcript Chapter 10 LAN Wiring, Physical Topology, and Interface Hardware

Chapter 10 LAN Wiring, Physical
Topology, and Interface Hardware
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Network Interface Card (fig 10.2)
 Ethernet wiring schemes
– Thicknet
– Thinnet
– Twisted-pair
Thick Ethernet
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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
2
3
4
5
6
7
logic ref.
Collision +
Tx +
logic ref
Rx +
Gnd
N/C
9
10
11
12
13
14
15
Collision –
Tx –
Logic ref
Rx –
+ 12Vdc
logic ref
N/C
Thin wire Ethernet
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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
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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-45
 One pair used for Rx; other pair for Tx
Ethernet Standards
standard
Cable type
Speed
10 Base5
Thick coax
10 Mbps
Maximum
Distance
500 m
10 Base2
Thin coax
10 Mbps
200 m
10 BaseT
100 BaseF
Twisted-pair 10 Mbps
copper
Twisted-pair 100 Mbps
copper
Optical fiber 100 Mbps
1000BaseF
Optical fiber 1000 Mbps
100 BaseT
100 m
100 m
2 km
Interoperability
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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 Paradox
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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) .