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Chapter 51. Upgrading Older Ethernet Networks

Chapter 51. Upgrading Older Ethernet Networks

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thetypeofcable.

TheoriginalEthernetspecificationsusedcoaxialcablinginstead

oftwisted-pairwiringorfiber-opticcables.Ifyou'restillusing

oldernetworktechnologies,itmightbetimetoupgrade.Don't

getmewrong:Ifyouhaveaspecializedenvironment,suchas

automationcontrolonafactoryfloor,youmightnotneedto

upgradethistypeofnetworkbecausedatatransferswillbe

minisculewhencomparedtoanofficenetwork.However,this

chapterassumesthatyouhaveanofficenetwork,whichcaneat

upnetworkbandwidthattremendousrates.Notonlydoyou

havetoprovidefileserversforsuchmundanetasksasword

processingandotherdatafiles,butnewerapplicationssuchas

livevideostreamingcansend10BASE-2and100BASE-T

networkstothehistorypile.

Older10BASE-5networksusedacoaxialcable(referredtoby

thoseinthefieldasthicknet)asabackbone,andtappedinto

thiscable(usingwhatispopularlycalledavampiretap)todrop

asmallercoaxialcablesuchas10BASE-2(againwitha

nickname,thinnet)toeachuser'sworkstation.Inanoffice

environment,thistypeofnetworkisuntenabletoday.Worker

productivityismeasuredinhourlycosts.Evenafewminutes

downloadingadocumentfromafileserverorcreatingareport

basedondataonaremoteservercostsyoumoney.Foran

officenetwork,it'stimetoupgrade.



Note

Ofallthetypesofinstallednetworkstoday,factory

automationprobablyistheleastyouneedtoworry

aboutwhenitcomestoupgradingtothelatestwhizbangtechnology.Thesesystemstendtobestable

andusuallyuseshieldedcablingduetothenatureof

thefactoryfloor,whichcancontainhundredsof

machinetoolsthatcaninterferewithsimpletwistedpaircables.Upgradestosoftwareformanagement



consolestendtobefewandfarbetween.Ifitworks,

whychangeit?

Forexample,oneoftheoldestnetworking

technologies,ARCnet,isstillprovidingnetwork

servicestosomethingyouwillfindineverydaylife:

point-of-saleterminals.Inyourlocalhamburger

joint(Imeaninyourlocalfastfoodrestaurant),do

youneedtoupgradetothenewestversionof

Etherneteveryfewyears?Itdoesn'ttakealotof

bandwidthtotakeorders,displaythemonscreens

forthehiredhelp,andkeeptrackoftransactions

performedatthecashregister.



ThetopicofthischapteristheofficeLANandnetwork

enterprisenetwork.Newerapplications,fromvideo

conferencingtoemployeeswholiketowastetimebrowsing

throughtheInternet,requiremuchmorebandwidththanolder

Ethernettechnologiessuchas10BASE-2canprovide.







Upgradingfrom10BASE-2or10BASE-T

Twisted-pairwiringprettymuchreplaced10BASE-2manyyears

agoandwas,foralongtime,thenetworkingsolutionofchoice.

Hubsallowedforcentralizationofwiringandswitcheshelped

localizeerrorsduetofaultycablesornetworkadaptercards.

100BASE-TandgigabitEthernetsolutionsarenowthedefacto

standardsforcreatinganewnetwork.Ifyou'recreatinga

networkfromscratch,it'sbesttostartwiththelatestand

greatestifyourbudgetallows.

Like10BASE-2networks,youshouldaskyourselfwhyyou

wouldevenwanttooperatea10BASE-Tnetwork.Ifyoualready

haveoneinplace,continuingtoaddnewhubs,switches,and

routersmaymakesense,providedthislimitedbandwidth

(10Mbps)cansatisfythedemandsofyourusers/applications.

However,100BASE-T(alsoknownasFastEthernet)hasbeen

aroundformorethan5years,andisnowthemostwidelyused

versionofEthernetbetweenthewiringclosetandtheuser

desktop.

Formoreinformationaboutnetworktopologiesandhowthe

physicalnetworkshouldbelaidout,seeChapter3,"Network

DesignStrategies."



Forthisreason,thischapterskipsupgradingfrom10BASE-2to

10BASE-Tbecausesuchanupgradereallyisn'tagood

investment.Ifyou'regoingtoswallowtheexpenseofpulling

newcablingtoreplaceoldercoaxialcabling,there'snoreason

togoto10BASE-Ttoday.Category5(andabove)cablingcan

handleboth,andalmosteverynetworkadaptercardproduced

todaycanoperateat10Mbpsaswellas100Mbps.Afteryou've



upgradedthecableplant,youmightaswellgofortheadded

bandwidthof100Mbpsinstead.

Therestofthischapterquicklylooksatsomeofthethingsto

considerwhenplanningtoreplaceanolderEthernetnetwork

withmoremoderntechnology.



HardwareandSoftwareFactorstoConsiderfor

10BASE-2,10BASE-T,and100BASE-T

Obviously,it'sthehardwarethatyou'llhavetoreplacewhen

makingthiskindofupgrade.Networkprotocols,suchasTCP/IP,

don'tcarewhattheunderlyingphysicalnetworkismadeupof

aslongastheycangetdatasegmentsfromoneplaceto

another.However,youmightstillbeusingoldersoftware,andif

so,youmightwanttoconsiderupgradingitinadditiontothe

hardwarewhenyouplanforthiskindofupgrade.Asdiscussed

inotherpartsofthisbook,Novell'sNetWarehasbasicallylost

theLANenvironmenttoUnixandWindowsNT/2000and

Windows2003servers,muchlesstheWindowsXPclient,and

eventhemostrecentversionsofNetWarecanuseIP.For

NetWare6.X,IPisthemainprotocol,giventheemphasisthat

NovellnowputsonInternetaccess.Forthenetworkthatyou

use,whetheritbeabuilt-intechnologyaswithWindowsor

Unix/Linuxoranadd-onproductsuchasNetWare,theIP

protocolremainsanunderlyingfactor.

Forahistoricaloverview,10BASE-2and10BASE-Thavemore

differencesthanjustthetypeofcablestheyuse.Althoughboth

ofthemusethesamemessagingtechnique(CSMA/CD),their

topologiesarebasicallydifferent:10BASE-2usesabus

topology,whereas10BASE-T(and100BASE-T)installationsuse

astartopology,implementedbyaswitch,althoughyoumight

findanolderhubstillbeingused.Thedistancesthatcanbe

coveredbycablesegmentsarealsodifferent.Thenetwork

adapterstransmitsignalsatdifferentspeeds.Whenpreparing

foranupgrade,checkyournetworkinventorytodetermine

whichpartsofthehardwareyou'llhavetoupgradeinaddition

tothecabling.Themajorconsiderationsthatneedtobe

researchedwhenupgradingfrom10BASE-2toatwisted-pair

networkareasfollows:



NetworkcablesThefundamentaldifferencebetween

10BASE-2and10BASE-T/100BASE-Tisthemovefrom

coaxialcabletotwisted-pairwiring,usuallyCategory5

cables,althoughnewercablingisnowbeingdeployed.

Formoreaboutcablesandotherrelevantcomponents,referto

Chapter6,"WiringtheNetworkCables,Connectors,Concentrators,

andOtherNetworkComponents."



NetworktopologyYou'llbegoingfromalinearbus

topologytoastartopology.Thedistancescoveredby

10BASE-T/100BASETareshorterthanthoseallowedusing

10BASE-2.Butbecauseofthestartopologyandtheusesof

switches,you'llactuallyfinditeasiertogreatlyextendthe

reachofyournetwork.

NetworkadaptersOldernetworkadaptersmighthave

onlyaBNCconnectoronthem.You'llneedcardsthat

provideanRJ-45jackfor10BASE-Tor100BASE-T.This

connectorlooksmuchlikeanordinarytelephonejack,butis

slightlylarger.

NetworkcableconnectorsInsteadofBNCconnectors,

twisted-paircablingusesRJ-45connectors.

HubsandswitchesAlthougha10BASE-2networkallows

youtousemultiportrepeaters,nocentralwiringdevices

areactuallyrequired.Fora10BASE-T/100BASE-Tnetwork,

youneed(ataminimum)ahubtoactasawiring

concentrator.Althoughalonehubmightsufficeforasmall

networkwithalimitednumberofusers,youshouldreally

considerusingswitchesinsteadbecausetheyenableyouto

furtherextendthedistancescoveredbyaLAN.Anditis



veryunlikelyyou'llfindahubforsaletoday.

Tolearnmoreabouthowhubsandswitchesfunction,see"Bridges,

Repeaters,andHubs,"ontheupgradingandrepairingpcs.comWebsite

andChapter8,"NetworkSwitches."



Forexample,ifyou'reusingamultiportrepeater,replacingit

withamorefunctionalhuborswitchseemedanaturalthingto

doafewyearsago.However,rememberthatthetopologyrules

for10BASE-2and10BASE-Tnetworksspecifydifferent

maximumcablesegmentlengths,soyoumighthavetorelocate

wiringclosetsormakeotheraccommodationsifyourcurrent

distancesaretoolong:

Maximumsegmentlengthfor10BASE-2:185meters

Maximumsegmentlengthfor10BASE-T/100BASE-T:100

meters

Maximumnumberofdevicesona10BASE-2hubsegment:

30

Maximumnumberofdevicesona10BASE-T/100BASE-T

hubsegment:2(butoneoftheseisthehub,soeffectively,

just1)

Chapter13,"Ethernet:TheUniversalStandard,"coversinmore

detailthedifferentcablingdistancesyou'llneedtoconsider.



Today,however,usingswitchingtechnologytoreplacehubsis

abouttheonlyoptionyouhavetoday.Asstatedearlier,you'll

finditdifficult,ifnotimpossible,tofindahubonthemarket

today.Theyarelegacydevices.Ifyou'regoingtoupgradeyour

network,consideraswitchtobeahubreplacement.That

doesn'tmeanyouneedtodiscardhubsinsmallsegmentsof

yourLANifyoualreadyhavethem.Indeed,ifyouconnecta

fewcomputersthathaveminimalbandwidthrequirementsto

yourLAN,there'sreallynoneedtoreplaceahubwithaswitch.

Italldependsonhowyourusersmakeuseofthenetwork.If

nooneiscomplainingwithahubconnection(whichyou'llmost

likelyhaveconnectedtoaswitchupstream),don'tworryabout

replacingit.Todayit'susuallytheapplicationsthatdrivethe

needforadditionalnetworkbandwidth.Ifit'sworkingnowand

nooneiscomplaining,don'tchangeit.

Themainconsiderationhereisthetopologyrequirementsused

forearlierEthernetnetworks.Ifthecabledoesn'tprovidethe

distanceorbandwidthrequirementsyouneedtoday,you'llhave

toreplacethecablingtoaccommodatemodernnetworks.Ina

smallLANenvironment,thisusuallyisn'tthecase.Inalarger

environment,youmighthavetoreplacecablingtoreachthe

distancesyouneed,yetstillprovidethesamebandwidththat

olderequipment(suchashubs)cangivetousers.



NetworkCables

Because10BASE-2usesthinnetcoaxialcabling,thefirst

upgradeissueyoumustaddressisgettingtheappropriate

networkcabling.

Thisshouldbethesimplestdecisionyouhavetomake.

Althoughit'squitepossibletouseCategory3wiringto

constructa10BASE-T(andevena100BASE-T)network,the

onlygoodreasonIcanthinkoftodosowouldbethatyou

alreadyhavethewiringinplaceandcanuseitwithfew



modifications.Otherthanthat,ifyou'regoingtoinstalla

100BASE-Tnetworktoreplaceanetworkbasedoncoaxial

cables,youwouldbebetterservedtogoaheadanduse

Category5cablingorbetter.Why?Furtherdowntheroadyou

mightfindyourselfupgradingtoGigabitEthernetoreven10

GigabitEthernet.

BothofthesetechnologiesrequireCategory5cablesorhigher.

AlthoughitmightseemlikeGigabitEthernetissomethingthat's

farinthefuture,keepinmindthatmanynetwork

administratorsdidn'tthinkthatvideoondemandwouldbea

requirementtoday.It'seasytounderestimatethenetwork

bandwidththatyou'llneedforfuturerequirements.And

becauseinstallingthecablingisoneofthemostlabor-intensive

(andthusexpensive)componentsofanetworkupgrade,I

recommendthatwhenyoudecidetoupgradecabling,yougo

forthelatesttoprotectyourinvestmentfartherintothefuture.

Indeed,I'dsaythatyournetworkbackboneshouldalready

consistoffiber-opticcablingbecauseGigabitandthenewly

ratifiedstandardfor10GigabitEthernetoperatebestusing

thesecables.Bothcanuseordinarycoppercables,butonlyfor

veryshortdistancesusuallyinthewiringcloset.

Theamountofcableyouneedmightworkouttobealotmore

thanyouusedforthe10BASE-2network.Rememberthatinthe

bustopologythatthinnet(coaxial)networkssuchas10BASE-2

use,youcandaisychainoneworkstationtoanotherusinga

linearbus.A50-ohmterminatorterminateseachendofthe

bus.Thetotalamountofcableneededissimplythesumofall

thecablesthataredaisychainedtogether.Whenusingahubor

switch,youcanhavetwoworkstationssittingrightnexttoeach

other,bothhavinga100-metertwisted-wirecablegoingbackto

thehub.Becauseofthis,thetotalamountofcablingyou'llneed

isgenerallyalotmorethanyoudidwhenyouinstalled10BASE2technology.Yetconsiderthatthecostoftwisted-pairwiringis

nowalotlessexpensivethatitusedtobe.Theeconomiesof

scalealwaysprovideforthis.



Ifyouinsteaduseamultiportrepeateronanexisting10BASE-2

network,andifonlyonecomputerisattachedtoeachport,

you'llfindthatreplacingthecablesisasimplematterof

stringingCategory5(orgreater)cablesthroughthesameroute

usedbythecurrentcoaxialcables.Thenallyouneedtodois

replacetherepeaterwithaswitch.Ifyouhavesegmentsona

multiportrepeaterthathavemorethanonecomputerattached,

you'llhavetoplugeachcomputerintoaseparateportona

switch.Anotherpossibilityistoplacethesecomputersona

separateswitchandconnectittothenetworkbackbone.



Note

Anotherconsiderationishowyouoriginallyinstalled

yourcoaxialcables.Differentjurisdictionshavelaws

thatstatehowelectricalandnetworkcablescanbe

installed.They'regenerallyencasedinaconduitof

somesort,suchasametalpipe.Tryingtoplace

severalhundredCategory5cablesinasmallspace

thatoriginallycontainedjustoneortwocoaxial

cablesmightbeaproblem.Considerthiswhen

designingthetopologyofyournewnetwork.



Becauseyoumuststringcablefromacentrallocationtoeach

workstation,youneedtohaveaplaceyoucanuseasawiring

closettostoretheswitchandanyotherinterconnecting

equipmentusedtojointheLANtoalargernetwork.Again,if

youwereusingamultiportrepeaterinyour10BASE-2network,

allyouneedtodoafterstringingthecablesistoreplacethe

multiportrepeaterwithaswitch.Alsokeepinmindthatif

you'resimplyupgradingasmallofficeLAN(510computers),

youcanuseaninexpensiveoff-the-shelfswitchfromyourlocal

computerstoreandsimplyplaceitoutofthewaysomewhere



convenientintheoffice.

Forallpracticalpurposes,considermakingbackbone

connectionsusingfiber-opticcabling.Doingsowillgiveyoua

muchfasterconnectionbetweenLANstodayandbetterprepare

youforthefuture.Keepinmindthattheold80%/20%ruleno

longerapplies.Thisrulestatedthat80%ofnetworktraffic

remainedinthelocalLANand20%wassenttoanother

segmentoftheLAN.Today,it'smoretypicaltocentralizelarge

serversinacomputerroomandkeepLANsseparatedby

switches.BecausecomputersontheLANneedtoaccessthese

servers,andtheymightbeseparatedbymultipleswitchesor

evenrouters,youshouldconsiderthe80%/20%ruletobe

reversed.Now80%ofnetworktrafficisdirectedoutsideofthe

localLAN.



NetworkInterfaceCard(NIC)

Ifyouhadtheforesighttopurchasethekindofnetwork

adaptercardscalledcombocards,whichhaveconnectors

compatiblewithbothBNCconnectorsandRJ-45connectors

(seeFigure51.1),thisisonepieceofhardwareyoumightnot

necessarilyhavetoreplaceunlessthecardistoooldtouse

speedspast10Mbps.TheminimumrequirementfortheNICis

thatithaveareceptacletowhichyoucanplugintheRJ-45

connectorendofthecabletoconnecttheadaptertoahub.

However,ifyouplantoincorporateswitchesintothenetwork

andwantserverstousefull-duplexconnections,you'llprobably

havetogetanewercardforthesecomputers(mostoldercards

supportedonly10Mbpsandnot100Mbps).Oldercombocards

enabledyoutoupgradefromBNCconnectors(usedby10BASE2)to10BASE-T.NewercardsusethestandardRJ-45jackand

allowfor10/100Mbscommunications.Andtoday,mostofthese

cardssupportauto-negotiationandWakeonLAN(WOL)

technologies.So,ifyou'restillusingcombocards,youcan

continuetousethem,butwillmostlikelybelimitedtoa



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