LAN Wiring, Physical Topology, And Interface Hardware

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LAN Wiring, Physical Topology, And Interface
Hardware

• Chaminade University
• Department of Computer Science and Computer
  Information Systems

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Goals

• In this chapter you will learn about
• LAN wiring
• Major Hardware components used in various wiring
  schemes
• Description of Hubs

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Network Interface Hardware
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Network Interface Hardware

• The CPU does not handle the transmission or
  reception of individual bits.
• The Network Interface Card (NIC) does that.
• Most NICs contain Direct Memory Access (DMA)
  that allows the NIC to operate independently of
  the CPU.

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Network Interface Hardware

• When the NIC finishes transmitting a packet, it
  uses the computers interrupt mechanism to inform
  the CPU.
• The NICs are designed to accommodate the
  mismatch in speed between the network and the
  computer.
• NICs function like an I/O device it is built
  for a specific network technology, and handles
  the details of frame transmission and reception.

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Network Interface Hardware
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Original Thick Ethernet Wiring
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Original Thick Ethernet Wiring

• The formal name for the scheme is 10Base5.
• The cable connecting a NIC to a transceiver is
  known as an Attachment Unit Interface (AUI)
  cable.
• The connectors on the NIC are known as AUI
  connectors.

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Connection Multiplexing
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Connection Multiplexing

• A multiplexer allows multiple computers to attach
  to a network through a single transceiver.
• This solves the problem of connecting multiple
  computers in a single room when (for example)
• The Ethernet cable is located in a hallway
  ceiling outside the room.

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Thin Ethernet Wiring
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Thin Ethernet Wiring (Thinnet)

• The formal name for the scheme is 10Base2.
• Generally cost less to install and operate than
  Thicknet.
• No need for external transceivers The hardware
  that performs the transceiver function is built
  into the NIC.
• A BNC connector is used.

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Thinnet and Thicknet

• Use coaxial cable (shield signals from the
  outside interference)
• Both require termination
• Both use bus topology.
• Similar electrical characteristics (resistance
  and capacitance)
• Signals propagate along the cables in the same
  way.

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Twisted Pair Ethernet

• Also known as TP Ethernet, was formally known as
  10BaseT (first version)
• Fast Ethernet is known as 100Base T.
• The wiring for Gigabit Ethernet is known as
  1000Base T.
• TP Ethernet uses multiplexing An Ethernet Hub is
  used.

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Twisted Pair Ethernet
Three computers connected to an Ethernet hub
using twisted pair wiring. Each computer has a
dedicated connection
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Twisted Pair Ethernet

• Electronic components in a hub emulate a physical
  cable, making the entire system operate like a
  conventional Ethernet.
• A typical hub has four or eight ports.
• Larger hubs can accommodate hundreds of
  connections.

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Wiring Offices
ThickNet
ThinNet
TP Ethernet
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Network Interface Cards
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Auto negotiation

• Original 10Base-T version of TP Ethernet operated
  at 10Mbps
• 100Base-T Ethernet operates at 100Mbps
• 1000Base-T Ethernet operates at 1 GBps.
• All use RJ-45 connectors
• 100Base-T is backward compatible and allows
  participants to negotiate a speed when a physical
  connection is first established.
• A NIC that supports 100Base-T and
  auto-negotiation is known as 10/100 Ethernet NIC.

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Categories of Wire
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Choosing a cable

• Cable should be appropriate for
• The intended data rate
• Distance
• Amount of electromagnetic noise
• Headroom
• Intended Costs

Headroom accommodating higher rates without
rewiring
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Wiring Schemes
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Wiring Schemes

• LocalTalk wiring scheme uses transceivers (lie
  Thick Ethernet)
• A particular LocalTalk wiring scheme uses hub
  technology
• The logical topology may differ from the physical
  topology.
• Hub wiring is often used with token passing
  rings.
• Hub wiring is sometimes referred to as ring in a
  box.