Chapter 3:Networking MediaChapter 3:Networking Media

Learning ObjectivesLearning Objectives

Define and understand technical terms related to cabling, including attenuation, crosstalk, shielding, and plenum

Identify three major types of both network cabling and wireless network technologies

Understand baseband and broadband transmission technologies and when to use each

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Learning Objectives

Decide what kinds of cabling and connections are appropriate for particular network environments

Describe wireless transmission techniques used in LANs

Describe signaling technologies for mobile computing

Network Cabling:Tangible Physical Media Provides a medium across which network

information can travel in the form of a physical signal, whether it is a type of electrical transmission or some sequence of light pulses

Primary Cable Types

Coaxial cable Twisted-pair (TP) cable

Unshielded (UTP)Shielded (STP)

Fiber-optic

General Cable Characteristics

Bandwidth rating Maximum segment

length Maximum number of

segments per internetwork

Maximum number of devices per segment

Interference susceptibility

Connection hardware Cable grade Plenum rating Bend radius Material costs Installation costs

Primary Techniques for Sending Signals across a Cable Baseband transmission Broadband transmission

Baseband Transmission

Uses digital signals sent over a cable without modulation

Sends binary values (0s and 1s) as pulses of different voltage levels

Entire bandwidth of the cable is used to transmit a single data signal

Limits any single cable strand to half-duplex transmission

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Baseband Transmission

Signal flow can be bi-directional Uses repeaters to restore the signal to its

original strength and quality before retransmitting it to another cable

Broadband Transmission

An analog transmission technique which may use multiple communication channels simultaneously

Each data channel is represented by modulation on a particular frequency band, for which sending or receiving equipment must be tuned

Signal flow is one-way only; two channels are necessary for computers to send/receive data

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Broadband Transmission

Uses amplifiers to detect weak signals, strengthen those signals, and then rebroadcast them

Primary approaches to supporting two-way broadband communications Mid-split broadband Dual-cable broadband

Offers higher bandwidths, but generally more expensive than baseband systems

The Importance of Bandwidth

The faster the connection, the better

Coaxial Cable

Uses a center conductor -- wrapped by an insulating layer, surrounded by a braided wire mesh and an outer jacket or sheath -- to carry high-bandwidth signals such as network traffic or broadcast television frequencies

Coaxial Cable

Uses shielding to increase the viability of the signals that pass through a cable by absorbing stray electronic signals or fields

Less susceptible to interference and attenuation than twisted-pair cabling, but more so than fiber-optic

A connector must cap each end of the cable, and a terminator must screw into each end

Types of Coaxial Cable for Ethernet Thin Ethernet (thinnet, thinwire,

cheapernet, 10Base2) Thick Ethernet (thicknet, thickwire,

10Base5)

Thinwire Ethernet

Thin, flexible cable about 0.2” in diameter Easy to work with Relatively inexpensive to build or buy Well suited for small or constantly changing

networks Uses BNC T-connectors to attach directly to

networking devices and computers’ network adapter cards

Thinwire Ethernet

Radio Government (RG) Specifications Coaxial cable designation that reflects

coaxial cable’s original use as a conveyance for radio frequency data and signals

Radio Government (RG) Specifications

Thinwire Ethernet Cable

Thickwire Ethernet

Uses a rigid cable about 0.4” in diameter (“frozen yellow garden hose”)

Rarely used except as a backbone for a new network installation (due to expense, large diameter, and lack of flexibility)

Uses a vampire tap to attach a device to the cable, which in turn attaches to a transceiver; transceiver attaches to a drop or transceiver cable that plugs into an attachment unit interface (AUI)

Attaching to Thinwire Ethernet Cable

Attaching to Thickwire Ethernet Cable

Running Thickwire Cable

Thickwire Ethernet Cable

Coaxial Cable Characteristics

Can handle moderate to serious bandwidth

Supports intermediate to moderately long cable runs

Relatively affordable Resistant to interference; relatively safe

from electronic “eavesdropping”

Twisted-pair Cable

Consists of one or more pairs of insulated strands of copper wire twisted around one another

Importance of twists Improve resistance to interferenceLimit the influence of crosstalk

Types of TP Cable

Unshielded twisted-pair (UTP) Contains one or more pairs of insulated wires within an

enclosing insulating sheath Follows the ANSI/EIA/TIA 568 standard Prone to crosstalk

Shielded twisted-pair (STP) Encloses each pair of wires within a foil shield, as well as

within an enclosing insulating sheath Supports higher bandwidth over longer distances than UTP Has no set of standards

Types of TP Cable

Twisted-pair Network Cabling Schemes Commonly employ RJ-45 telephone

connectors Typical elements (often in a wiring center)

Punchdown blocksPatch panelsWall platesJack couplers

RJ-45 Connector

Patch Panels and Punchdown Blocks

10BaseT’s Networking Characteristics

Fiber-optic Cable

Uses pulses of light sent along a light-conducting fiber at the heart of the cable to transfer information

Sends data in one direction only; two cables are required to permit data exchange in both directions

Consists of a slender cylinder of glass fiber(s), called the core, surrounded by a concentric layer of cladding material and then by an outer sheath

Fiber-optic Cable

Primary Types of Fiber-optic Cables Single-mode cables

Include only one glass fiber at the core Cost more Work with laser-based emitters but span the longest

distances Multi-mode cables

Incorporate two or more glass fibers at the core Cost less Work with light emitting diodes (LEDs) but span

shorter distances

Fiber-optic Cable Advantages

Immune to interference Highly secure; eliminates possibility of

electronic eavesdropping Good medium for high-bandwidth, high-

speed, long-distance data transmissions

Fiber-optic Cable Drawbacks

High cost Difficult installation

Fiber-optic Cable Characteristics

Fiber-optic Media Connectors

ST (straight tip) SC (straight connection) MIC (medium interface connector) SMA (subminiature type A)

Cable Selection Criteria

Bandwidth Budget Capacity Environmental considerations Placement Scope Span

Comparison of General Cable Characteristics

The IBM Cabling System

Numeric cabling designations (Type 1 through Type 9) developed by IBMTypes 2 and 9 are the most commonly used

networking cables IBM cable connector is the unique feature;

any two connectors are able to plug into each other

IBM Cable Types

Wireless Networking: Intangible Media Depends on transmission at some kind of

electromagnetic frequency through the atmosphere to carry data transmissions from one networked device to another

Appears most frequently in conjunction with wired networks

Capabilities of the Wireless World Creates temporary connections to existing wired

networks Establishes back-up or contingency connectivity

for existing wired networks Extends a network’s span beyond the reach of

wire- or fiber-optic-based cabling Permits certain users to roam with their

machines, within certain limits

Commercial Applications for Wireless Networking Ready access to data for mobile professionals Delivery of network access into isolated facilities Access in environments in which layout and

settings change constantly Improved customer services in busy areas Network connectivity in facilities where in-wall

wiring would be impossible to install or prohibitively expensive

Types of Wireless Networks

Local area networks (LANs) Extended LANs Mobile computing

Wireless LAN Applications

Still necessary to attach a network interface to a computer, but the interface attaches to an antenna and an emitter rather than to a cable

Requires an access point device to bridge wireless components and the wired network

Wireless Access Point Device

Wireless LAN Transmission

Most common frequencies used Radio: 10 KHz to 1 GHz Microwave: 1 GHz to 500 GHz Infrared: 500 GHz to 1 THz

Primary technologies used Infrared Laser Narrowband, single-frequency radio Spread-spectrum radio

Broadcast Medium Principles

Inverse relationship between frequency and distance

Direct relationship between frequency and data transfer rate and bandwidth

Higher-frequency technologies often use tight-beam broadcasts and require a clear line of sight between sender and receiver to ensure correct delivery

Infrared LAN Technologies

Use infrared light beams to send signals between pairs of devices

Have high bandwidth; work well for LAN applications

Require a line of sight between sender and receiver

Kinds of Infrared LANs

Line-of-sight networks Reflective wireless networks Scatter infrared networks Broadband optical telepoint networks

Laser-based LAN Technologies

Require a clear line of sight between sender and receiver

Devices are subject to many of the same limitations as infrared but are not as subject to interference from visible light sources

Narrow-band, Single-frequency Radio LAN Technologies Use low-powered, two-way radio

communications Require no line-of-sight between sender

and receiver

Narrow-band, Single-frequency Wireless LAN Characteristics

High-powered, Single-frequency LAN Characteristics

Spread-spectrum LAN Technologies Address weaknesses of single-frequency

communications Use multiple frequencies simultaneously; improve

reliability and reduce susceptibility to interference Make eavesdropping more difficult

Two main kinds Frequency-hopping Direct-sequence modulation

Spread-spectrum LAN Characteristics

Wireless Extended LAN Technologies Wireless bridge

A pair of devices, typically narrow-band and tight beam, that relay network traffic from one location to another

Available using spread-spectrum radio, infrared, and laser technologies

Can span distances from hundreds of meters up to 25 miles

Wireless Extended LAN Characteristics

Microwave Networking Technologies Can deliver higher transmission rates than radio-

based systems Transmitters and receivers must share a

common, clear line of sight Usually require FCC approval and licensing More expensive than radio systems Two types

Terrestrial Satellite

Terrestrial Microwave

Uses line-of-sight communication between pairs of Earth-based transmitters and receivers to relay information

Expensive; usually positioned well above ground level

Terrestrial Microwave LAN/WAN Characteristics

Satellite Microwave

Uses geosynchronous satellites to send and relay signals between sender and receiver

Usually leased for an exorbitant fee

Satellite Microwave WAN Characteristics

High-speed Wireless Networking Technologies IEEE 802.11 Wireless Networking

Standard Cellular packet radio networking Cellular Digital Packet Data (CDPD) Narrow-band sockets

Chapter Summary

Network cabling Primary cable types

Twisted-pair (unshielded and shielded) and coaxial conductive cables

Fiber-optic cables Cabled network transmission schemes

BroadbandBaseband

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Chapter Summary

Wireless networking Provides cable-free LAN access Extends span of LANs Provides WAN links Supports mobile computing needs Uses a variety of electromagnetic frequency ranges

Narrow-band and spread-spectrum radio Microwave Infrared Laser transmission

Chapter 4:Network Interface Cards

Chapter 4:Network Interface Cards

Learning ObjectivesLearning Objectives

Describe what role a network adapter card plays in networked communications

Explain how network adapters prepare data for transmission, accept incoming network traffic, and control how networked communications flow

Understand the variety of configurable options for network adapters and describe common settings

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Learning Objectives

Describe important characteristics for selecting adapter cards

Recount network adapter enhancements that can improve performance

Explain the role of driver software in network adapters

Network Interface Card Basics

Crucial tasks performed by a NICEstablishes and manages the computer’s

network connectionTranslates digital computer data into signals

(appropriate for the network medium) for outgoing messages; translates signals into digital computer data for incoming messages

From Parallel to Serial, and Vice Versa A network adapter grabs outgoing transmissions

from the CPU in parallel form and recasts them into their serial equivalents Parallel transmission

Spreads individual bits of data across multiple, parallel data lines to transmit them simultaneously, rather than according to an ordinal and temporal sequence

Serial transmission Sends each bit’s worth of data (or its analog equivalent) one

at a time, one after another, in sequence

Reverses the process for incoming messages

From Parallel to Serial, and Vice Versa

From Parallel to Serial, and Vice Versa Memory is an important component on a

network adapter that acts as a holding tank, or buffer

Bus width Number of parallel lines that make up a bus

Transceiver A device that transmits and receives network

information

An Ethernet NIC

From Parallel to Serial, and Vice Versa NIC packages all the bits into orderly

collections called packets and then transmits individual packets serially onto the network medium

Using a network address, the NIC determines whether the computer is the appropriate recipient of data sent

Summary of NIC Basics

Manages and controls network access Creates a physical link between a computer and

a network medium Handles data transfers to and from the network

and CPU and translates which forms such data can take between parallel and serial representation

Interacts with the medium to determine when data transmission is permissible

PC Buses

Specialized collections of parallel lines in a PC used to ship data between the CPU and peripheral devices

Primary bus architectures ISA (Industry Standard Architecture) EISA (Extended ISA) MCA (Micro Channel Architecture) PCI (Peripheral Component Interface) AGP (Accelerated Graphics Port)

Primary Bus Architectures

Other PC Interfaces Used for Networking USB (Universal Serial Bus) FireWire (also known as IEEE 1394)

Principles of NIC Configuration

Plug and Play architecture Manual configuration involves working with three

types of PC settings: Interrupt request line (IRQ) Base I/O port Base memory address

Two ways of setting hardware configurations Jumper blocks DIP (dual inline package) switches

Setting Hardware Configurations

Interrupt Request Lines (IRQs)

Any of 16 unique signal lines between the CPU and the bus slots on a PC

Define the mechanism whereby a peripheral device can stake a claim on the PC’s attention

Most Common PC IRQs

Base I/O Port

The memory address where the CPU and an adapter check for messages that they leave for each other

Must be unique

Common NIC Base I/O Port Assignments

Base Memory Address (membase) Starting address for NIC’s buffer space Bounded by size of the buffer’s extent

Making the Network Attachment

Importance of matching the adapter you choose with the medium to which it must attach

When a network adapter supports more than one media type, selecting the one to use becomes another configuration optionNormally involves changing DIP switches or

shifting a jumper block

Choosing Network Adapters for Best Performance Identify the physical characteristics the

card must match Consider other hardware-enhancement

options to help improve overall network performance

Hardware-enhancement Options Direct Memory Access (DMA) Shared adapter memory Shared system memory Bus mastering RAM buffering On-board co-processors Security features Traffic management or grooming Improved fault tolerance

Considerations when Purchasing a Network Adapter Bus width Bus type Memory transfer Special features required Bus mastering Vendor factors

Special-purpose NICs

Interfaces for wireless networks Interfaces for diskless workstations (a.k.a.

thin clients), which must access the network to load an operating system as they boot up Support remote boot or remote initial program

load

Wireless Adapter Components

Indoor antenna and antenna cable Software to enable the adapter to work

with a particular network environment Diagnostic software to check initial

installation or to troubleshoot thereafter Installation software

Remote Boot Adapters

Some include a chip socket for Boot PROM (programmable read-only memory)

Once a diskless workstation finishes booting, it can use the network to read and write additional needed data

Driver Software

Permits a network adapter to communicate with a computer’s operating system

Recommendations Ensure that a valid driver is available for your

operating system before purchasing an adapter Obtain the latest driver version before installing a

network adapter Make regular driver upgrades part of your network

maintenance routine

Major Driver Vendor Standards

NDIS (Network Device Interface Specification)

WDM (Win32 Driver Model) ODI (Open Data-link Interface)

Installing a New Network Connection

Chapter Summary

What a network interface does and how it works

How to install and configure network adapters

How to select an appropriate adapter for your situation