1 Ethernet Wiring Qutaibah Malluhi CSE Department Qatar University.

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Ethernet Wiring

Qutaibah MalluhiCSE DepartmentQatar University

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Network Interface Cards

CPU can't process data at network speeds – Computers use special purpose hardware for network

connection Typically a separate card in the backplane

– Network adapter card or network interface card (NIC) – Connector at back of computer then accepts cable to physical

network NIC is built for one kind of physical network

– Ethernet interface can't be used with token ring – ATM interface can't be used with FDDI

Some NICs can be used with different, similar hardware – Thick, thin and 10Base-T Ethernet – 10Mbps and 100Mbps Ethernet

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NICs

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NIC and CPU

NIC processes network frames independent of the CPU

Looks like any other I/O device to system CPU – System CPU forms message request – Sends instructions to NIC to transmit data – Receives interrupt on arrival of incoming data

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Ethernet Wiring

Network technology not limited to one style of connection

Ethernet Technologies– Three wiring schemes

correspond to three generations

– All run same link speed of 10Mbps

– All use same frame format– All are Ethernet

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Original Ethernet Wiring - Thicknet

Used thick coaxial cable -- Called thicknet Formal name 10Base5 -- Each segment can be up to 500m and

100 stations AUI cable (or transceiver or drop cable connects from NIC to

transceiver AUI cable carries digital signal from NIC to transceiver Transceiver generates analog signal on coax Wires in AUI cable carry digital signals, power and other control

signals Requires termination to avoid signal reflectance

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Connection of a station to the medium using 10Base5

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Connection Multiplixers

Transceivers can be inconvenient – e.g., workstations in a lab

Connection multiplexor connects multiple computers to a single transceiver

Connection multiplexor completely invisible to attached computers

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Thin Ethernet Wiring - Thinnet

Uses thinner coax– cheaper and easier to install than thick Ethernet coax

Transceiver electronics built into NIC– NIC connects directly to network medium

Coax cable uses BNC connector Formal name 10Base2 -- Each segment can be up to 200m and 30 stations

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Connection of stations to the medium using 10Base2

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Thinnet Illustration

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Hub-based 10BaseT

Uses a hub -- Replaces thick coax with hub Formal name 10BaseT -- Each segment can be

up to 100m and runs on twisted pair Called 10Base-T, twisted pair or TP Ethernet Replaces AUI cable with twisted pair cable

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Connection of stations to the medium using 10Base-T

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10BaseT illustration

Sometimes called ``Ethernet-in-a-box''

Effectively a very short Ethernet with very long AUI cables

Can be connected into larger Ethernets

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Office Ethernet Wiring

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Comparing Ethernet Wiring Schemes

Thicknet:– Separate transceiver allows computer to be changed or

disconnected without disrupting other communication – Transcievers are inconvenient

» located in difficult to reach place » Finding malfunctioning transceiver can be hard

Thinnet– Lower cost than thicknet. Coax takes minimum cabling – Disconnecting one computer (or one loose connection)

can disrupt entire network 10Base-T

– Hub wiring centralizes management and makes it easier

– Bottom line - 10BaseT most popular because of cost

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Extending Ethernet

More details in the next chapter Example:

– Multiple Ethernet segments can be connected using repeaters (no more than four => total length 2,500m).

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Wiring Scheme Adapters

AUI to Thinnet AUI to 10BaseT

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Logical and Physical Topologies

Physically– Original Ethernet used bus topology– Modern Ethernet uses star topology

In fact, modern Ethernet is– Physical star– Logical bus– Called star-shaped bus

Distinguish between logical and physical topologies– 10BaseT logical topology is a bus; wiring topology is a

star – Token Ring logical topology is a ring; wiring topology is

a star» Token Ring hub: Ring-in-a-box

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Summary

Network interface card (NIC) – connects computer system to network – operates independently of the system CPU– Typically uses interrupts to interact with CPU

Many physical wiring schemes are available for a logical network topology

Three basic Ethernet wiring schemes– 10Base5, 10Base2, and 10BaseT

10Base-T is a logical bus and a physical star