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Ethernet 802.3 Physical Layer Topology: Order in which stations receive

bits

Ethernet hubs use a bus topology

Signal is broadcast

All stations receive almost simultaneously

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Ethernet 802.3 Physical Layer Topology: Order in which stations receive

bits

Early Ethernet standards arranged stations

in a daisy chain Stations broadcast on the chain in both directions

All stations receive almost simultaneously

Original idea of bus

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Ethernet 802.3 Physical Layer Topology: Order in which stations receive

bits

Ethernet switches use a switched topology

Signal only goes to one station

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Ethernet 802.3 Physical Layer Ethernet began as a bus network

Some question whether Ethernet switching

is really Ethernet

However, hubs will be disappearing in the

next few years, and almost all Ethernet will

be switched

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Ethernet 802.3 Physical Layer

Recent Ethernet 802.3 Standards use

Unshielded Twisted Pair (UTP) Wiring or

Optical Fiber

For Small LANs with a Single Hub or

Switch, use UTP Exclusively

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Physical Layer 802.3 UTP

Standards Ethernet 802.3 10Base-T

Physical layer standard

Created by the 802.3 Working Group

10 Mbps

Baseband transmission

Insert signal directly into wire No channels

T means uses UTP twisted-pair wire

10 Mbps

802.3

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Physical Layer 802.3 UTP

Standards Ethernet 802.3 100Base-TX

100 Mbps

100Base-TX: Not just 100Base-T because other100Mbps UTP standards were created but werenot used significantly

Ethernet802.3

1000B

ase-T Gigabit Ethernet

Overkill for small LANs

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Physical Layer 802.3 UTP

Standards Wiring

Unshielded Twisted Pair Bundle of 4 pairs (only uses 2 pairs)

One pair to send

One pair to receive

Terminates in RJ-45 connector

Slightly larger than RJ-11 home phone connector

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Physical Layer 802.3 UTP

Standards Categories of UTP Wiring

Wiring Quality, Category 3 being lowest

For 10Base-T Categories 3, 4, or 5 are OK

However, most installed wiring is Cat 5

For 100Base-TX, Cat 5 is required

For Gigabit Ethernet,EnhancedCategory 5is recommended, although Cat 5 shouldwork if perfectly installed

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Physical Layer: 802.3 UTP Standards

Wiring

100 meters maximum UTP distance hub-to-

station or hub-switch

200 meters maximum distance between stations

100 m 100 m

200 m

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Physical Layer 802.3 Standards NIC-Hub Communication

NIC transmits on one pair (Pins 1&2)

Hub or switch transmits on another pair (Pins 3

& 6)

Other 4 wires are not used

To Hub or Switch (Pins 1&2)

From Hub or Switch (Pins 3&6)

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Physical Layer 802.3 Standards Upgrading from 10Base-T to 100Base-TX

Need new hub or switch

May have autosensing 10/100 ports that handle

either 10 Mbps or 100 Mbps NICs

Need new NICs

Only for stations that need more speed

No need to rewire This would be expensive