SwitchingtoVoIP
ByTheodoreWallingford
...............................................
Publisher:O'Reilly
PubDate:June2005
ISBN:0-596-00868-6
Pages:502

TableofContents|Index

Moreandmorebusinessestodayhavetheirreceivephoneservice
throughInternetinsteadoflocalphonecompanylines.Many
businessesarealsousingtheirinternallocalandwide-area
networkinfrastructuretoreplacelegacyenterprisetelephone
networks.Thismigrationtoasinglenetworkcarryingvoiceand
dataiscalledconvergence,andit'srevolutionizingtheworldof
telecommunicationsbyslashingcostsandempoweringusers.The
technologyoffamiliesdrivingthisconvergenceiscalledVoIP,or
VoiceoverIP.

VoIPhasadvancedInternet-basedtelephonyaviablesolution,
piquingtheinterestofcompaniessmallandlarge.Theprimary
reasonformigratingtoVoIPiscost,asitequalizesthecostsof
longdistancecalls,localcalls,ande-mailstofractionsofa
pennyperuse.Buttherealenterpriseturn-onishowVoIPempowers
businessestomoldandcustomizetelecomanddatacomsolutions
usingasingle,cohesivenetworkingplatform.Thesebusiness
driversaresocompellingthatlegacytelephonyisgoingthewayof
thedinosaur,yieldingtoVoiceoverIPasthedominantenterprise
communicationsparadigm.

Developedfromreal-worldexperiencebyaseniordeveloper,
O'Reilly'sSwitchingtoVoIPprovidessolutionsforthemost
commonVoIPmigrationchallenges.Soifyou'reanetwork
professionalwhoismigratingfromatraditionaltelephonysystem
toamodern,feature-richnetwork,thisbookisamust-have.You'll
discoverthestrengthsandweaknessesofcircuit-switchedand
packet-switchednetworks,howVoIPsystemsimpactnetwork
infrastructure,aswellassolutionsforcommonchallengesinvolved
withIPvoicemigrations.Amongthechallengesdiscussedand
projectspresented:


buildingasoftPBX
configuringIPphones
ensuringqualityofservice
scalability
standards-compliance
topologicalconsiderations
coordinatingacompletesystem?switchover?
migratingapplicationslikevoicemailanddirectory
services
retro-interfacingtotraditionaltelephony
supportingmobileusers
securityandsurvivability
dealingwiththechallengesofNAT

Tohelpyougraspthecoreprinciplesatwork,Switchingto
VoIPusesacombinationofstrategyandhands-on"how-to"that
introduceVoIProutersandmediagateways,variousmakesofIP
telephoneequipment,legacyanalogphones,IPTablesandLinux

firewalls,andtheAsteriskopensourcePBXsoftwarebyDigium.
You'lllearnhowtobuildanIP-basedorlegacy-compatiblephone
systemandvoicemailsystemcompletewithe-mailintegrationwhile
becomingfamiliarwithVoIPprotocolsanddevices.Switchingto
VoIPremainsvendor-neutralandadvocatesstandards,not
brands.Someofthestandardsexploredinclude:

SIP
H.323,SCCP,andIAX
Voicecodecs
802.3af
TypeofService,IPprecedence,DiffServ,andRSVP
802.1a/b/gWLAN


IfVoIPhasyourattention,likesomanyothers,thenSwitching
toVoIPwillhelpyoubuildyourownsystem,installit,andbegin
makingcalls.It'stheonlythingleftbetweenyouandamodern
telecomnetwork.


SwitchingtoVoIP
ByTheodoreWallingford
...............................................
Publisher:O'Reilly
PubDate:June2005
ISBN:0-596-00868-6
Pages:502

TableofContents|Index
















































Copyright
dedicationDedication
Foreword
Preface
Audience
AssumptionsMadeinThisBook
Conventions
WheretoGetMore
SafariEnabled
HowtoContactUs
Acknowledgments
Chapter1.VoiceandData:TwoSeparateWorlds?
Section1.1.ThePSTN
Section1.2.KeySystemsandPBXs

Section1.3.LimitsofTraditionalTelephony
Section1.4.VoIPintheHome
Section1.5.VoIPinBusiness
Section1.6.VoIP'sChangingReputation
Section1.7.KeyIssues:VoiceandData:TwoSeparateWorlds
Chapter2.VoiceoverData:ManyConversations,OneNetwork
Section2.1.VoIPorIPTelephony
Section2.2.DistributedVersusMainframe
Section2.3.KeyIssues:VoiceoverData:ManyConversations,OneNetwork
Chapter3.LinuxasaPBX
Section3.1.FreeTelephonySoftware













































































Section3.2.InstallingLegacyInterfaceCards
Section3.3.CompilingandInstallingAsterisk
Section3.4.MonitoringAsterisk
Section3.5.KeyIssues:LinuxasaPBX

Chapter4.Circuit-SwitchedTelephony
Section4.1.RegulationandOrganizationofthePSTN
Section4.2.ComponentsofthePSTN
Section4.3.CustomerPremisesEquipment
Section4.4.TimeDivisionMultiplexing
Section4.5.Point-to-PointTrunking
Section4.6.LegacyEndpoints
Section4.7.Dial-PlanandPBXDesign
Section4.8.KeyIssues:Circuit-SwitchedTelephony
Chapter5.EnterpriseTelephonyApplications
Section5.1.ApplicationTerminology
Section5.2.BasicCallHandling
Section5.3.AdministrativeApplications
Section5.4.MessagingApplications
Section5.6.AdvancedCall-HandlingApplications
Section5.7.CTIApplications
Section5.8.KeyIssues:TelephonyApplications
Chapter6.ReplacingtheVoiceCircuitwithVoIP
Section6.1.The"Dumb"Transport
Section6.2.VoiceChannels
Section6.3.Project6.1.SetUpCustomCodecSelectionandEnablean
IndependentCallPath
Section6.4.KeyIssues:ReplacingtheVoiceCircuitwithVoIP
Chapter7.ReplacingCallSignalingwithVoIP
Section7.1.VoIPSignalingProtocols
Section7.2.H.323
Section7.3.SIP
Section7.4.IAX
Section7.5.MGCP
Section7.6.CiscoSCCP

Section7.7.HeterogeneousSignaling
Section7.8.KeyIssues:ReplacingCallSignalingwithVoIP
Chapter8.VoIPReadiness
Section8.1.AssessingVoIPReadiness
Section8.2.BusinessEnvironment















































































Section8.3.NetworkEnvironment
Section8.4.ImplementationPlan
Section8.5.KeyIssues:VoIPReadiness
Chapter9.QualityofService
Section9.1.QoSPastandPresent
Section9.2.Latency,PacketLoss,andJitter
Section9.3.CoS
Section9.4.802.1qVLAN

Section9.5.QualityofService
Section9.6.ResidentialQoS
Section9.7.VoiceQoSonWindows
Section9.8.BestPracticesforQualityofService
Section9.9.KeyIssues:QualityofService
Chapter10.SecurityandMonitoring
Section10.1.SecurityinTraditionalTelephony
Section10.2.SecurityforIPTelephony
Section10.3.AccessControl
Section10.4.SoftwareMaintenanceandHardening
Section10.5.IntrusionPreventionandMonitoring
Section10.6.Project10.3.LoggingandControllingVoIPPacketswithiptables
Section10.7.KeyIssues:SecurityandMonitoring
Chapter11.TroubleshootingTools
Section11.1.VoIPTroubleshootingTools
Section11.2.TheThreeThingsYou'llTroubleshoot
Section11.3.SIPPacketInspection
Section11.4.Interoperability
Section11.5.Project11.3.TraceBothEndsofaCallSetupwithLogComparison
Section11.6.When,Notif,YouHaveProblems...
Section11.7.SimulatingMediaLoads
Section11.8.KeyIssues:TroubleshootingTools
Chapter12.PSTNTrunks
Section12.1.Dial-ToneTrunks
Section12.2.RoutingPSTNCallsatConnectPoints
Section12.3.TimingTrunkTransitions
Section12.4.KeyIssues:PSTNTrunks
Chapter13.NetworkInfrastructureforVoIP
Section13.1.LegacyTrunks
Section13.2.VoIPTrunks

Section13.3.Project13.1UseDial-PlantoConnecttoMultipleVoIPNetworks










































































Section13.4.WANDesign
Section13.5.DisasterSurvivability
Section13.6.Metro-AreaLinks
Section13.7.FirewallIssues
Section13.8.Peer-by-PeerCodecSelection
Section13.9.Project13.2.BuildanInteractiveDirectoryonaSIPDisplayPhone
Section13.10.KeyIssues:NetworkInfrastructureforVoIP
Chapter14.TraditionalAppsontheConvergedNetwork
Section14.1.FaxandModems
Section14.2.FireandBurglarySystems
Section14.3.SurveillanceSystemsandVideoconferencing
Section14.4.VoiceMailandIVR
Section14.5.EmergencyDispatch/911
Section14.6.KeyIssues:TraditionalAppsontheConvergedNetwork
Chapter15.WhatCanGoWrong?
Section15.1.CommonProblemSituations
Section15.2.KeyIssues:WhatCanGoWrong?

Chapter16.VoIPVendorsandServices
Section16.1.SoftphonesandInstantMessagingSoftware
Section16.2.Skype
Section16.3.OtherDesktopTelephonySoftware
Section16.4.DeveloperToolsandSoftPBXSystems
Section16.5.VoIPServiceProviders
Section16.6.TelephonyHardwareVendors
Chapter17.AsteriskReference
Section17.1.HowAsteriskIsSupported
Section17.2.Asterisk'sConfigurationFiles
Section17.3.AsteriskDial-Plan
Section17.4.AsteriskChannels
Section17.5.TheAsteriskCLI
Section17.6.IntegratingAsteriskwithOtherSoftware
Section17.7.KeyIssues:AsteriskReference
AppendixA.SIPMethodsandResponses
AppendixB.AGICommands
AppendixC.AsteriskManagerSocketAPISyntax
Glossary
Colophon
AbouttheAuthor



Colophon

Index


SwitchingtoVoIP

byTedWallingford
Copyright©2005O'ReillyMedia,Inc.Allrightsreserved.
PrintedintheUnitedStatesofAmerica.
PublishedbyO'ReillyMedia,Inc.,1005GravensteinHighway
North,Sebastopol,CA95472.
O'Reillybooksmaybepurchasedforeducational,business,or
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ourcorporate/institutionalsalesdepartment:(800)998-9938or

Editor:

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ProductionEditor:

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InteriorDesigner:

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PrintingHistory:




June2005:

FirstEdition.

NutshellHandbook,theNutshellHandbooklogo,andthe
O'ReillylogoareregisteredtrademarksofO'ReillyMedia,Inc.
SwitchingtoVoIP,theimageofhyacinthmacaws,andrelated
tradedressaretrademarksofO'ReillyMedia,Inc.


Manyofthedesignationsusedbymanufacturersandsellersto
distinguishtheirproductsareclaimedastrademarks.Where
thosedesignationsappearinthisbook,andO'ReillyMedia,Inc.
wasawareofatrademarkclaim,thedesignationshavebeen
printedincapsorinitialcaps.
Whileeveryprecautionhasbeentakeninthepreparationofthis
book,thepublisherandauthorassumenoresponsibilityfor
errorsoromissions,orfordamagesresultingfromtheuseof
theinformationcontainedherein.
ISBN:0-596-00868-6
[M]


Dedication
ToKelly,mycharmingwifeandtheindispensablerecipientofso
manyofmyVoIPcalls.


Foreword
ThisistheyearofVoIP!Sowaslastyear,andtheyearbefore

that,andtheyearbeforethat....Okay,sowhat'stherealstory?
IsVoIPreallygoingtohappen?TheansweristhatVoIPhas
beenslowlyhappeningallthistime.Bitbybit,industryby
industry,thistechnologyhasbeencreepingintohomesand
businesseseverywhere.
Asatechnology,VoIPisaprettysimpleideausepacketswitcheddataencapsulationinsteadofthetried-and-truetimedivisionmultiplexed(TDM),circuit-switchedmethodsthat
telephonyhasusedsinceitscreation.Sinceitscreation?Isthat
anexaggeration?TDMtelephonytodayisessentiallyjustan
electronicversionofthe"cordboard"thattheold-time
operatorsusedtoconnectonecallerwithanother.Advancesin
packetcommunicationtechnologiesarenowmakingthatmodel
obsolete,permittingmoreefficientuseofbandwidthresources
whileprovidingmobilityandtheintegrationofvoice,presence,
andotherinformation.
IfVoIPissogreat,whyhasitbeensoslowtocatchon?First,
ascurrentlystandardized,VoIPismorecomplicatedto
administerandsetupthanatraditionaltelephoneline.Second,
whileVoIP'stechnicalmeritsareimpressive,TDMtechnologyis
globallydeployed."Coppermaybeburied,butit'snotdead,"
thesayinggoes.Inordertobesuccessful,VoIPmustbe
interoperablewiththisestablishedtechnology.Finally,until
recently,VoIPwasmoreexpensivetodeploythantraditional
telephony.Today,thankstocompetitionenabledbyopen
standardsandmorerecentlyopensourcetechnologiessuchas
Asterisk,thecostofaVoIPsystemisnotonlycompetitivewith
TDM,butinmanycaseslessexpensive(aswellitshouldbe).
ThekeytoevaluatingwhenVoIPmayormaynothelpyou,and
tohavingsuccessfulVoIPdeploymentswhereitdoeshelp,is



understandingthetechnologies,protocols,andtools(including
opensourceplatformssuchasAsterisk,forwhichIcan'tresist
includingasecond,shamelessparentheticalplug).Itisthegoal
ofthisbooktoeducateandinformyou,toputcontrolinyour
hands,andtosaveyoufromasmuchfrustrationaspossible!
OriginalauthorandmaintainerofAsterisk
FounderandpresidentofDigium
MarkSpencer


Preface
VoiceoverIPisafamilyoftechnologiesthathassweeping
implicationsforeverybodywhousestelephones,theInternet,
faxmachines,email,andtheWeb.VoIPborrowsfrom,and
enhances,manydisciplinesofcommunicationstechnology;it
promisestorevolutionizethemostfamiliarofthese
technologies,thetelephone.TheInternetProtocol,analog
telephony,digitaltelephonyandT1circuits,digitalaudiosignal
processing,high-availabilitynetworking,andahostofother
concernsarealltouchedbygrowingbordersofthevast,
ambitiousrealmofVoIP.
VoIPhasfounditswayintobusinessphonesystems,desktop
messagingsoftware,andresidentialtelephonyservice.Your
mortgageorinsurancecompany'swebsitemayofferyouthe
abilitytocommunicatebyVoIPwithacustomerservicerep
usingyourcomputer.YoumaysubscribetoVoIP-based
telephoneserviceslikePacket8,AT&TCallVantage,Vonage,or
BroadvoxDirectasareplacementforyourold,traditionalphone
service.
Inthelate1990s,VoIPwaslaudedasawaytosaveonlongdistancechargesbycallingGrandmaandGrandpausingaPC

withaheadsetandamicrophone.Buttoday'sdefinitionofVoIP
isfarbroader.HundredsofthousandsofVoIP-baseddevicesare
inuseintheUnitedStates,andfast-growingshipmentsofVoIPcompatibletelephonesystemshaverevitalizedthedata
networkingindustry.ThenextevolutionarystepfortheInternet
istobecomereliableenoughtoreplacetheglobaltelephone
networkasweknowit.
So,VoIPisadisruptivetechnologyfamilythatpromisesto
revolutionizethewaywecommunicate,whiledrivingdecreases
inthecostofthatcommunicationandincreasesinthespeed,
reliability,andavailabilityoftheInternetitself.That'swhatVoIP


does.Butyou'rereadingthisbookbecauseyouwanttoknow
howitdoesit.Here'swhatyou'llencounterwhilereading
SwitchingtoVoIP:
Adefinitionofpublicandprivatelegacyvoicesystemsanda
quickreviewoftheirevolution
Adescriptionofthecoretechnologiesofdigital
telephonysampling,pulsecodemodulation,timedivision
multiplexing,trunking,andcallsignaling
ExamplesofhowVoIPnetworksoverlayIPnetworksand
howvoiceapplicationsresidewithintheOSInetworkmodel
AnexplanationofwhymanyearlyVoIPadopters'
implementationsdidn'tliveuptoexpectations
AnintroductiontothetwosubsetsofVoIPstandards:audio
transmissionandsignaling
IntroductionstoSIP,H.323,andothersignaling
specificationsthatarecommonlyusedinIPtelephony
SomepracticalstrategiesforjustifyingVoIPadoptionina
businessscenario

AnintroductiontoIPhardphones,analogtelephone
adapters,softPBXservers,andtheotherdevicesthatmake
VoIPsystemstick
Strategiesfordealingwithquality-of-serviceissues,
includingpolicy-based,protocol-based,andpractice-based
approachestoensuringtip-topoperationalqualityofaVoIP
network


InformationaboutinterfacingVoIPsystemswithtraditional
phoneequipmentandthepublictelephonesystembyway
ofanalogtrunksandT1lines
Thebasicsofenforcinglow-layersecurityinaVoIP
environment,withexamplesforIPTablesfirewalls
TipsforgaugingVoIPreadinessonanenterprisenetworkor
overanInternetpathway
Scenariosthatdescribewhatnetworktechnologieswork
bestforvoicesystems,andhowtocompensatewith
quality-of-servicemeasuresacrossthosethatdon'tworkso
wellforvoice
Dozensofpractical,hands-onprojectsthatyoucanuseto
buildthepiecesofyourVoIPnetworkwhilelearningwhich
standardsandpracticeswillworkbestforyourparticular
environment
Anumberoftroubleshootingscenariostohelpyoudeal
with,andavoid,themostcommonmistakesthataremade
whenimplementingthistechnology
Ahandyvendorreferencethatwillputyouintouchwiththe
keysoftware,hardware,andserviceplayersintheVoIP
business

Areferenceforthebasicconfiguration,SIPinterfacing,and
legacyinterfacingoftheworld'smostpopularopensource
telephoneserver,Asterisk


Audience
Thoughthisbookpresentsafairamountoftheory,wehave
gonetogreatlengthstokeepthematerialaspracticalas
possible.Ithasbeenwrittensothatyoucanreadachapter,
applythatchapter,andcomebacktolearnmore.IT
professionals,alargepieceofthisbook'stargetaudience,are
oftenthetypeofpeoplewholearnbestbydoing,sothat'show
thematerialispresented.Infact,you'llnoticethatthebook
looksattelephonymorefromapacketnetworkingengineer's
perspectivethanfromatelephonenetworkengineer's
perspective,evengoingsofarastoapplytheOSImodelto
telephonesystems,whichwereinventeddecadesbeforethe
OSImodelwas.
Butanybodywho'snewtoVoIPshouldgetahandleonits
terminologies,implications,andscopebyreadingthisbook.IT
managers,telecommunicationsdirectors,andhands-onCIOs
willallbenefitfromtheproper(andonemightsayrefreshing)
perspectivethisbookhastowardVoiceoverIPnotthetextbook
perspectiveofalegacytelephonesystemengineer,butthe
hands-onviewpointofanIPnetworkingprowhorecently
completedanumberoflegacy-to-VoIPsystemconversions.In
thiscase,itcantrulybesaidthatIamcastfromthesame
moldasmyreaders.
ProspectiveVoIPadopters,Cisco-certifiednetworkspecialists,
andthosewithapersuasiontowardopenstandardsmaywant

toreadthisbookonaccountofitsvendorneutrality.Linux,
Windows,andMacsolutionsarediscussed,whileCisco,
Grandstream,Digium,andotherhardwarevendorsplay
prominentrolesinthehands-onprojects.Thisisnoaccident.
Theworldoftelephonyisamultivendordomaininwhich
interoperabilityiscriticalandfailureofcompetingvendors'
systemstoworktogether,unlikedesktopcomputing,is
unacceptable.Thisbookthereforeadvocatesstronglyfor


internationalstandardsratifiedbytheInternational
TelecommunicationsUnion,theInternetEngineeringTaskForce,
andotherbodies.

RegardingAsterisk
AsteriskisanopensourcetelephonyserverthatrunsonLinux,
FreeBSD,andMacOSX.Itwaschosenasaplatformfor
illustratingmanyoftheexamplesinthisbookforseveral
reasons.Itsupportsmanyofthestandardsneededtoteach
VoIPsignalingconcepts;itrunsonregular,easy-to-getPC
equipment;andperhapsmostimportantly,it'sfree.Ifyouwant
toexperimentwithVoIPwithoutspendingalotonhardware,
Asteriskisagreatstartingpoint.Andwhilecommercial
solutionshavetheirplace,youmightalsofindthatAsteriskisa
worthwhileendsolution.You'llfindapartialAsteriskreference
andappendixesattheendofthebook.


AssumptionsMadeinThisBook
Thisbookassumessomefamiliaritywithdatanetworking.It

reviewsTCP/IPaddressingandtheseven-layerOSInetwork
model,butproceedwithcautionifthesetopicsaren'talready
familiartoyou.Eachchapterbuildsupontheconcepts
describedinthepreviouschapters,sothebookisintendedto
bereadinorder.


Conventions
Mostdefinitionsaregivenuponfirstencounteringanewterm.
There'saglossaryincludedincaseyoumissadefinitionorjust
needarefresher.
Carrierisawordthatisreferredtoinmanydifferentways
throughoutthebook.Sometimesitmeansaphonecompany,
othertimesitreferstoadatalinksystem.Whereverawordhas
twopotentialmeanings,thecontextshouldtellyouwhich
meaningisappropriate.
Inmostcases,examplesareprovidedintermsofNorth
Americanstandardsandpractices.Whereappropriate,
EuropeanorAsianequivalentsarementioned.
Kilobitisabbreviatedask,whilekilobitspersecondshowsup
askbps.Thesameconventionisusedformega-andgigaprefixeswhereapplicable.Forthesakeofclarity,manyauthors
willdefinewhetherkilomeans1,000or1,024.Thisisan
importantdistinction,butyoudon'tneedtoworrymuchabout
ithere.It'ssafetoassumeamultipleof1,000whenkilois
used.Thatis,64kilobitsisexactly64,000bitsandsoon.
Thefollowingtypographicalconventionsareusedinthisbook:

Plaintext
Indicatesmenutitles,menuoptions,menubuttons,and
keyboardaccelerators(suchasAltandCtrl).


Italic


Indicatesnewortechnicalterms,systemcalls,URLs,
hostnames,emailaddresses,filenames,fileextensions,
pathnames,anddirectories.

Constantwidth
Indicatescommands,options,switches,variables,
attributes,keys,functions,types,objects,HTMLtags,
macros,thecontentsoffiles,ortheoutputfrom
commands.

Constantwidthbold
Showscommandsorothertextthatshouldbetyped
literallybytheuser.

Constantwidthitalic

Showstextthatshouldbereplacedwithuser-supplied
values.

Thisiconsignifiesatip,suggestion,orgeneralnote.

Thisiconindicatesawarningorcaution.


WheretoGetMore
Thereare1,000-pagebooksabouttelephonesystems,and

thereare50-pagereferencepamphletsaboutasingleprotocol,
likeSIP.Whenwritingabooklikethis,it'sachallengetostrike
abalancebetweentheunwieldytomethat'sfilledwith
countlessdetailsoftrivialimportandacrash-courseFAQthat
tellsyoujustenoughtogetstarted.Ononehand,there's
nebulousreferencematerial,andontheother,there'snot
enoughdetailbutlotsofconciseness.
Toaddressthis,thebookisratherdetailedoncertainsubjects
andratherbriefandconciseonothers.Ifyou'relookingfor
moreinformationinaspecialarea,O'Reillyoffersotherbooks
thatmayhelpyou,includingnarrowbutdetailedbooksabout
T1circuits,datacommunicationstheory,networksecurity,and
Ethernet.SafariOnlineisO'Reilly'sweb-basedlibraryofbooks,
aninvaluabletoolthatcanalsoprovidemoredepth.
InformationonO'Reilly'sprintedbooksandSafariareavailable
at.


SafariEnabled

WhenyouseeaSafari®Enabledicononthecoverof
yourfavoritetechnologybook,itmeansthebookisavailable
onlinethroughtheO'ReillyNetworkSafariBookshelf.
Safarioffersasolutionthat'sbetterthane-books.It'savirtual
librarythatletsyoueasilysearchthousandsoftoptechnology
books,cutandpastecodesamples,downloadchapters,and
findquickanswerswhenyouneedthemostaccurate,current
information.Tryitforfreeat.



HowtoContactUs
Pleaseaddresscommentsandquestionsconcerningthisbookto
thepublisher:
O'ReillyMedia,Inc.
1005GravensteinHighwayNorth
Sebastopol,CA95472
(800)998-9938(intheUnitedStatesorCanada)
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Wehaveawebpageforthisbook,wherewelisterrata,
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/>Tocommentorasktechnicalquestionsaboutthisbook,send
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Acknowledgments
MyfirstnoncurricularwritingwasashortsciencefictionstoryI
wroteafterhavingbeeninspiredbymythird-gradeteacher's
readingaloudtomyclass.ThebookhereadtouswasThe
Lion,theWitch,andtheWardrobebyC.S.Lewis.So,Iowea
thankyoutoMr.DennisStreich,mythird-gradeteacher,for
givingmearespectforthesocialandeducationalimportanceof
themediumofbooks.WhileIcan'tblameanyofmybadwriting
habitsonthesetwogentlemen,Icancertainlycreditthemwith
helpingtocultivatemyloveofthewrittenwordevenwhenit's

aboutageekysubjectlikeVoIP.
Morerecently,myreadingandwritinghavebeenofanentirely
differentsortthevocationalsort.WhenIworkedforJ.Walter
ThompsoninDetroit,IwasflippedacopyofO'ReillyMedia's
epicmasterpiecesendmailbyoneoftheguysIworkedwith.
Thisbookwasagodsend.Ifanybodycouldtranslateadeadly
topiclikesendmailconfigurationintotermsIcouldunderstand,
itwasBryanCostalesandEricAllman,theauthorsofthat
highlyimportantbook.Theaccessibilityandorganicapproach
ofsendmailwerecommontomostO'Reillybooks,Ilater
noticed.WhetheritwasPracticalPostgreSQLorRealBASIC:The
DefinitiveGuide,Ihadaneasiertimelearningfromthese
"animalbooks"thanIhadfromothers.
WhengiventheopportunitytowriteaboutVoiceoverIPfor
O'Reilly,itwasaneasydecision.Ihadjustcompletedthefirst
phaseofanambitioustelephonyconversiononalarge
constructioncontractor'snetwork,andIwaslookingfor
standards-advocatingdocumentationtohelpmearchitectthe
nextphase.Theproblemwas,allthedecision-making
intelligenceformyprojectwasprovidedbytheVoIPequipment
vendorsandtheirsalespeopleCisco,Avaya,Nortel,Mitel,NEC,
andsoon.CiscowasbashingAvaya,andAvayawasbashing
Nortel,adnauseum.Iwaslookingfortheneutral,standards-