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Chapter 53. Adding Wireless Networking to a LAN

Chapter 53. Adding Wireless Networking to a LAN

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Note

Threeindustry-standard802.11implementationsare

currentlycertifiedbytheWi-FiAlliance.IEEE

802.11b,theoriginalWi-Fistandard,runsat11Mbps

anduseschannelsinthe2.4GHzfrequencyband.

IEEE802.11adiffersinspeed(54Mbps)and

frequency(5GHzband).IEEE802.11g,themost

popularWi-Fistandard,runsatupto54Mbps(like

802.11a)butusesthesame2.4GHzfrequencyband

as802.11bandcanco-existonthesamenetworkas

802.11bhardware.Currently,802.11gandvarious

proprietaryextensionsofthisstandardarethemost

commonstandardforSOHOwirelessnetworks.

802.11aisusedprimarilyincorporatewireless

networksoralongsideof802.11gindualbandSOHO

implementations.802.11bisusedprimarilyinolder

networks,orbysomespecializeddevices.802.11bis

nolongerwidelyavailablefornewinstallations.



Youcanreadmoreaboutthe802.11standardsinChapters19,

"IEEE802.11b:Wi-FiPioneer;"20,"FasterService:IEEE802.11a;"

and21,"TheIEEE802.11gStandard."







WhyGoWireless?

Wirelessnetworkinghasitsplaceinthehome,smalloffice,and

enterpriseenvironments.YoucanuseaninexpensiveAccess

Pointtocreateanetworkofjustafewcomputers,oryoucan

usemultiplewirelessAccessPoints(APs)throughoutalarge

companytofurtherenablemobilityofyournetworkedclients.

Therearemanygoodreasonstousewirelessnetworking.First,

it'saquickwaytosetupapeer-to-peernetworkthatisneeded

foronlyashortperiodoftime,suchasinahomeofficewhere

youonlyhavetwoorthreecomputersthatneedalinkandyou

don'twanttoberunningnetworkcablesthroughyourwalls.

Youcanalsousewirelessnetworkingtoconnectacomputer

andanotherdevice,suchasaprinter(usingeitherbuilt-in

wirelessnetworkingorawirelessprintserver),adigitalcamera,

orahandhelddevicesuchasaPDA.

Forthehomeenvironment,wirelessnetworkingmaybethe

perfectchoicebecauseitnotonlyeliminatesthenecessityof

pullingcables,butalsogivesyouflexibilityinwhereyoulocate

yourequipment.Forexample,althoughyoumighthaveset

asideaportionofyourhousetouseforyourhomeoffice,it's

nicetobeabletotakethelaptopintothelivingroom(orouton

thedeckinthebackyard)andworkwhileyou'rewatchingthat

favoriteTVshow.Wirelessnetworkingmakesthissimple.

Anotheruseforwirelesstechnologyisthetradeshow

environment.Ifyouneedtonetworkseveralcomputersand

possiblyaprinterortwo,anetworkusingawirelessAccess

Pointcanbeaquickwaytogetyourboothupandrunningina

hurry.Thisalsocanbeusedataclientsiteifyou'reinthe

consultingbusinessanddon'twanttoconnectyourcomputers

toyourclient'snetwork.Indeed,itcanbeaneasywaytoget

yourcomputersintotheclient'sofficebecausethey'llhaveno

up-frontworktodotoprovideyouwithnetworkingservices.



Finally,youcanuseawirelessnetworktoextendthereachof

yourexistingLAN.Accesspointscanbeconnectedtoawired

LANtoprovideaningresspointforwirelessclients.OnaSOHO

network,youcanreplaceanexistingrouterwithawireless

router.Bothwiredandwirelessrouterstypicallyincorporatea

multi-port10/100Ethernetswitch,soyoucanuseasingle

devicetocreateamixedwired/wirelessnetwork.

However,justbecauseit'spossibledoesn'tmeanit'snecessary.

Someplacesinacorporatenetworkthatyoumightfind

wirelessnetworkAPsagoodideainclude

ConferenceroomsUsersoftenbringlaptopcomputersto

meetingstotakenotes.Usingwirelessnetworkingina

conferenceroomcanallowthatlaptoptolocateinformation

thatexistselsewhereontheLANthatmightbeuseful

duringthemeeting.Nomore"I'llgetbackwithyouonthat"

excuses.

TemporaryworkgroupsAnAccessPointcanbeuseful

whenyouneedtobringintemporaryworkers,usingspace

that'sotherwisenotwiredfornetworkaccess.Because

manymanufacturingplantshaveseasonalpeaksand

slumps,thismightbeanidealwaytoquicklysetupnew

clientsonanetworkwithouttheexpenseofhavingtogo

throughtheprocessofprovidingswitchesandcablerunsto

allpartsofyourbuilding.Instead,asinglecableruncanbe

usedforanAPthatcanserveavariablenumberofclients

onanas-neededbasis.Ifyouchoosethisapproach,make

sureyouselectanAPcapableofhandlingthemaximum

numberofworkerswhowillconnecttoitatonetime.

Generally,corporateorenterprise-levelAPsaredesignedto

supportamuchhighernumberofsimultaneoususersthan

SOHOAPs.IfyouanticipateneedingtosupportVPN

connections,makesureyoudeterminethemaximum

numberofVPNuserswhowillusetheAPatthesametime,



andselectamodelthatmeetsthatrequirementaswell.

MobileusersForuserswhomainlyworkwithalaptopand

areusuallyontheroadsuchassalespeopleawireless

solutionmightbeagoodidea.Whentheuserreturnstothe

officeforashorttime,adockingstationcanserveto

connectthelaptoptothewirednetwork.However,a

dockingstationbasicallymeansreservingadeskaswell

andoverheadcanbeexpensiveintoday'scompetitive

market.Instead,asingleofficewithafewdesksandanAP

canservealargenumberoftransientworkers.

FactoryfloorLaptopsarenottheonlycomputersthatcan

beusedinawirelessnetwork.ManyPDAsandothersmall

handhelddevicesareavailablethatcanuseWi-Finetwork

cards.Onafactoryfloor,wheremobilityisimportant,it's

easiertouseasmallportabledevicethanitistosetupa

seriesofPCsthroughouttheplant.Becausemany

manufacturingplantsneedtoreconfigurethefactoryfloor

onaperiodicbasistoretoolfornewproducts,wireless

networkingcanagainprovetobeacostsaver.

InChapters18,"IntroductiontoWirelessNetworking,"and19,you

canfindinformationonhowtoextendanetworkwithwireless

technology.



Anotherplacethatwirelessnetworkingcanserveauseful

purposeisforoutdooractivities.I'veworkedatmanyplaces

thathaveoutdoorlocationsthatemployeescanuseat

lunchtime.Theseareasalsocanbecomfortableplacestohold

meetings.Sometimesjustgettingoutoftheofficecanboost

employeemoraleandtakingthenetworkoutsidecan,asnoted

previously,makemeetingsmoreproductive.Therearemany

otherusesforwirelessnetworks,andnewideasarebeing



createdeveryday.



Note

Inadditiontothedeploymentofwirelessnetworking

intheSOHOandenterprisecorporateenvironment,

wirelessnetworkingisfindingitswayintomany

publicspaces.Atthistime,manyhotelsalready

offerwirelessnetworkingforguestsandmeeting

roomclients,alongwiththeplug-indial-upaccess

thathasbecomethenorm.Publiclibraries,airports,

coffeeshops,truckstops,andafewentirecities

offeravarietyoffreeorpaidwirelessaccess

services.Althoughit'sstillusefultofindoutin

advancewhereyoucangetwirelessaccessasyou

travelaroundthecityorthecountry,whoprovides

it,andhowmuchitcosts,youcaneasilystayin

touchasyoutravel.







ChoosingLocationsforAccessPoints

JustasyouneedtotestnewnetworkconfigurationsorPC

configurationsinalaboratorybeforerollingthemoutfor

productionusage,youneedtoevaluatetheplacementofAPs

shouldyoudecidetogetintowirelessnetworking.Wi-Fi

providesforroamingcapabilities,butitalsoenablesyouto

restrictuserstoselectedAPsifyouchoosetodoso.First,

decidehowyouwanttousewirelessnetworkingandwhich

usersitcanbeusedbyinaproductivemanner.Next,decide

howmanyAPsyouneedandwheretoplacethem.

You'llhavetodosomeexperimentation.Readthevendor's

documentationtogetthebasicsofthecoverageareathatthe

productiscapableof,keepinginmindthatthisisonlyageneral

figure.Forexample,you'llfindthatmostAPsarecapableof

coveringlargerdistancesoutside,ratherthaninside,because

therearefewerstructuralcomponents,suchasbricksorsteel

beams,thatcanblockthesignal.Youshouldtakeavendor's

specificationsaboutitsparticularproductwithagrainofsalt.

Yourmileagecanvary.

Ifyouusewirelessnetworkinginsideandwanttocoverthe

entirebuilding,you'llhavetotesttoseeexactlyhowfarthe

coverageisforeachAP.Alsonotethatseveralfactorscan

influencetheperformanceyou'llgetnomatterwhereyouplace

theAP.Forexample,eachAPiscapableofsupportingonlya

limitednumberofusersbeforetheavailablebandwidthbegins

tobecomesaturated.Although802.11ghardwareistheoverall

favoriteinSOHOandpublic-accessnetworks,thehigher

frequencyusedby802.11aenablesittosupportmoreusers

thanwith802.11g.Formaximumspeedandflexibilityinyour

businessnetwork,usingdual-mode802.11a/802.11gwireless

APsandadaptersisrecommended.

Anotherthingtoconsiderissourceofinterference,suchas



microwaveovensandotherwirelessdevices.Ifyouemploy

Bluetoothdevices,youneedtobecarefulbecauseBluetooth

caninterferewithWi-Fi2.4GHz(802.11band802.11g)devices

whenusedatdistancesof2cmorlessordistancesgreaterthan

10cm(forexample,auserwithaBluetoothkeyboard/mouseor

aBluetoothwirelessheadsetusingacomputerwithan802.11g

wirelessnetworkadaptermighthaveproblems).Although

Bluetoothhasbeenimprovedwithtechnologysuchasadaptive

frequencyhopping(firstintroducedinBluetoothversion1.2)to

trytominimizeinterference,theuseofBluetoothinclose

proximityto2.4GHzWi-Fidevicescanvirtuallyshutdownthe

2.4GHzWi-Fidevices.IfyouplantouseWi-FiandBluetooth

devicesinyourorganization,considerusing802.11aordualband802.11a/802.11gwirelessAPsandadapters.802.11a

doesnotusethesamefrequencyas802.11gorBluetooth.



Note

RichardQuinnellprovidesanexcellentsummaryof

thecurrentchallengesfacingWi-Fi2.4GHzand

BluetoothoperationsincloseproximityinhisAugust

2005article"WiFiandBluetoothFightfor

Bandwidth."Finditonlineat

www.edn.com/article/CA629312.html.



AnotherpopularSOHOandofficedeviceisthe2.4GHzcordless

telephone.Thesetelephonesoperateinthesamebandas

2.4GHzwirelessnetworksandcancauseproblemswhenused

inthevicinityofwirelessnetworkingdevices.Consider

upgradingto5.8GHzwirelessphonesifyouuse2.4GHzWi-Fi

wirelessnetworkhardware.Ifyoualsouse5GHz(802.11a)

wirelessnetworking,don'tworry:5.8GHzphonesdonotcause

significantinterferencewith5GHzWi-Fi(802.11a)wireless



networks.

Sometypesofwirelessmousedevicesandkeyboardsalso

presentariskofconflict.AllBluetooth-baseddevices,including

wirelessmousedevicesandkeyboards,usethe2.4GHzband,

asdomanynon-Bluetoothimplementationsfromvarious

vendors.Tohelppreventconflicts,manyofthesedevices

supportmultiplechannels.UsethecontactinformationinTable

53.1todetermineifaparticular2.4GHzinputdevicemight

conflictwithyourexisting2.4GHzdevices.

Table53.1.2.4GHzWirelessInputDevices(NonBluetooth)

Vendor



WebSite



ProductType



ModelName/Number



Adesso



www.adesso.com



Keyboardwith

integrated

touchpad



WirelessSlimTouchMini

WKB-4000US



Belkin



www.belkin.com



Keyboard,

mouse,and

entertainment

remote



MediaPilotF8E838



CherryCorp



www.cherrycorp.com Keyboardand



mouse



CyMotionPROWireless

Desktop,M85-20850



CreativeLabs



www.creative.com



Keyboardand

mouse



CreativeDesktop

Wireless9000Pro



Gyration



www.gyration.com



Keyboardand

mouse



GO2.4OpticalAir

Mouse,andeitherFullSizeKeyboardSuite

GC1205FKMorCompact

KeyboardSuite

GC1105CKM











Mouse



GO2.4AirMouse

GC1005M



Tip

Ifawirelessmouseorkeyboardhasamaximum

rangeofsixfeetorless,ituses27MHztechnology.A

wirelessmouseorkeyboardwithamaximumrange

of25feetorfurtheruses2.4GHztechnology.Check

thedevice'sspecificationstodetermineifthedevice

usesBluetoothoraproprietaryimplementation.



Table53.1listsmanypopularnon-Bluetoothinputdevicesthat

usethe2.4GHzRFband.

Andkeepthatmicrowaveoveninthebreakroomwellshielded!

Youcanpurchaseaninexpensivedeviceatmostconsumer

discountstoresthatcanmeasuretheamountofmicrowave

radiationthat'sleakingfromamicrowaveoven.Youmightfind

thatsimplyreplacinganoldmicrowaveovenwithanewer

modelcuresanyinterferenceproblems.Andbecausemostwork

placesdon'tneedatop-of-the-linemicrowavethatcanzapa

bakedpotatoinjustafewminutes,gowithalow-endmodel

thatuseslesspower.







SecurityIssues

Usingwirelesstechnologyopensupthepossibilityofsecurity

breaches.Thoroughlyreadthedocumentationthatcomeswith

yourchoiceofdevicestofindoutwhatkindofsecurityfeatures

canbeenabled.It'sprobablybesttoassociatethewireless

networkadaptersyoubuywithoneormoreAPs,dependingon

theworkhabitsoftheuser.Alsonotethatmanydevicescome

withdefaultsettingsandthattheseareknowntoanyonewho

ownsasimilardeviceorwhocarestolookuptheinformation

ontheInternet.Tohelppreventsecurityproblems,implement

securityproceduressuchassettingupuniquepasswordson

eachAP,usingyourownSSIDsratherthanusingthedefault

namethatthewirelessvendorprovides,anddisablingSSID

broadcast.

Changeanydefaultsettingsusedtomatchupwirelessadapters

andAccessPointstouseavalueotherthanthedefault.Usethe

securityfeaturesofyouroperatingsystemtomonitorwireless

users.Forexample,I'dbemoreconcernedwithaWindows

2000orWindowsXPuser'sresourceaccesspermissionsifthe

clientcomputerusesawirelessnetworkcardthanIwouldbeif

itwerewireddirectlytothenetwork.WindowsXP,becauseitis

designedtoautomaticallyconnecttoanunsecuredwireless

network,makesitveryeasytoconnect,butitmeansthatusing

wirelesssecuritysettingsarenolongeraluxury.Ifyouwantto

keepunauthorizedusersoffyourwirelessnetwork,youmust

enablethestrongestformofwirelesssecuritysupportedby

yourwirelessAPandwirelessadapters.

Althougholderwirelessnetworkhardwareusedonlythefirst

WirelessEquivalencyProtocol(WEP)securitystandard,this

standardisnotstrongenoughfortoday'snetworks.WEPuses

fixed-lengthstatickeys,andevenifthenewer128-bitor

corporate-level256-bitencryptionisusedratherthantheolder

64-bitencryption,WEPiseasytocrack.Manytoolsare



availableonlinethatcanbeusedtocircumventWEPencryption,

sodon'tbetyourbusinessonit.

Wi-FiProtectedAccess(WPA)anditsimprovedsibling,WPA2,

providemuchgreaterwirelessnetworksecuritythanWEP.Both

canbeusedwithRADIUSauthenticationserversonyour

corporatenetworkforevengreatersecurity.EveninaSOHO

environment,WPAandWPA2arefarmorecrack-resistantthat

WEP.IfyoustillhavehardwarethatdoesnotsupportWPA,

considerreplacingitifyoucannotupgradeitsdriversor

firmwaretosupportWPA.

Rememberthatit'seasiertoeavesdroponawirelessnetwork

becauseyoudon'thavetomakeanyconnectionstoacable,as

inawirednetwork.Radiowavesareoutthereforanyonewithin

rangeofyourtechnologytopickup.

YoucanlearnmoreaboutwirelesssecurityinChapter23,"Other

WirelessTechnologies."



Inanycase,it'seasytosetupauditingforimportantresources

andtoreviewthemusingtheEventViewerinWindows2000/XP

andWindowsServer2003.Nomatterhowsafeyouthinkyour

networkis,there'snoexcusefornotauditing(andcheckingthe

audits)toensurethatyoursecuritymeasuresareworking.

Lookingforsuchthingsasalargenumberofloginfailurescan

alertyoutosomeonetryingtobreakintoyourwireless

network.UnixandLinux(usingthesyslogutility)canalsobe

usedtolookforsystemauditinginformation.Thesyslogutility

canbeconfiguredtoalsosendalerts,byemailandother

means,sothatyoucanbeinformedquicklyofanypossible

securitybreaches(orattempts).



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Chapter 53. Adding Wireless Networking to a LAN

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