OReilly TCPIP network administration 3rd edition apr 2002 ISBN 0596002971

Tableof
•
Contents
• Index
• Reviews
Reader
•
Reviews
• Errata

TCP/IPNetworkAdministration,3rd
Edition
ByCraigHunt

Publisher :O'Reilly
PubDate :April2002
ISBN :0-596-00297-1
Pages :746
Slots :1



Thiscompletehands-onguidetosettingupandrunninga
TCP/IPnetworkstartswiththefundamentals:what
protocolsdoandhowtheywork,howaddressesand
routingareused,andhowtosetupyournetwork
connection.Thebookalsocoversadvancedrouting
protocolsandprovidestutorialsonconfiguringimportant

networkservices.Theexpandedthirdeditionincludes
sectionsonSamba,Apachewebserver,networksecurity,
andmuchmore.




TCP/IPNetworkAdministration,3rd
Edition

ByCraigHunt
Tableof
•
Publisher :O'Reilly
Contents PubDate :April2002
• Index
ISBN :0-596-00297-1
Pages :746
• Reviews
Slots :1
Reader
•
Reviews
• Errata



Copyright

Dedication



Preface



Audience



Organization



UnixVersions



Conventions



We'dLiketoHearfromYou



Acknowledgments

Chapter1.OverviewofTCP/IP



Section1.1.TCP/IPandtheInternet



Section1.2.ADataCommunicationsModel



Section1.3.TCP/IPProtocolArchitecture



Section1.4.NetworkAccessLayer



Section1.5.InternetLayer



Section1.6.TransportLayer

Section1.7.ApplicationLayer



Section1.8.Summary




Chapter2.DeliveringtheData



Section2.1.Addressing,Routing,andMultiplexing



Section2.2.TheIPAddress



Section2.3.InternetRoutingArchitecture



Section2.4.TheRoutingTable

Section2.5.AddressResolution






Section2.6.Protocols,Ports,andSockets



Section2.7.Summary




Chapter3.NetworkServices



Section3.1.NamesandAddresses



Section3.2.TheHostTable



Section3.3.DNS

Section3.4.MailServices



Section3.5.FileandPrintServers



Section3.6.ConfigurationServers



Section3.7.Summary




Chapter4.GettingStarted



Section4.1.ConnectedandNon-ConnectedNetworks



Section4.2.BasicInformation

Section4.3.PlanningRouting



Section4.4.PlanningNamingService



Section4.5.OtherServices



Section4.6.InformingtheUsers



Section4.7.Summary




Chapter5.BasicConfiguration



Section5.1.KernelConfiguration

Section5.2.StartupFiles



Section5.3.TheInternetDaemon



Section5.4.TheExtendedInternetDaemon



Section5.5.Summary




Chapter6.ConfiguringtheInterface



Section6.1.TheifconfigCommand



Section6.2.TCP/IPOveraSerialLine

Section6.3.InstallingPPP



Section6.4.Summary




Chapter7.ConfiguringRouting



Section7.1.CommonRoutingConfigurations



Section7.2.TheMinimalRoutingTable



Section7.3.BuildingaStaticRoutingTable



Section7.4.InteriorRoutingProtocols



Section7.5.ExteriorRoutingProtocols

Section7.6.GatewayRoutingDaemon



Section7.7.Configuringgated



Section7.8.Summary




Chapter8.ConfiguringDNS




Section8.1.BIND:UnixNameService



Section8.2.ConfiguringtheResolver



Section8.3.Configuringnamed

Section8.4.Usingnslookup



Section8.5.Summary




Chapter9.LocalNetworkServices



Section9.1.TheNetworkFileSystem



Section9.2.SharingUnixPrinters



Section9.3.UsingSambatoShareResourceswithWindows



Section9.4.NetworkInformationService

Section9.5.DHCP



Section9.6.ManagingDistributedServers



Section9.7.PostOfficeServers



Section9.8.Summary




Chapter10.sendmail



Section10.1.sendmail'sFunction



Section10.2.RunningsendmailasaDaemon

Section10.3.sendmailAliases



Section10.4.Thesendmail.cfFile



Section10.5.sendmail.cfConfigurationLanguage



Section10.6.RewritingtheMailAddress



Section10.7.Modifyingasendmail.cfFile



Section10.8.Testingsendmail.cf



Section10.9.Summary

Chapter11.ConfiguringApache



Section11.1.InstallingApacheSoftware



Section11.2.ConfiguringtheApacheServer



Section11.3.Understandinganhttpd.confFile



Section11.4.WebServerSecurity



Section11.5.ManagingYourWebServer



Section11.6.Summary




Chapter12.NetworkSecurity

Section12.1.SecurityPlanning



Section12.2.UserAuthentication



Section12.3.ApplicationSecurity



Section12.4.SecurityMonitoring



Section12.5.AccessControl



Section12.6.Encryption



Section12.7.Firewalls

Section12.8.WordstotheWise



Section12.9.Summary





Chapter13.TroubleshootingTCP/IP



Section13.1.ApproachingaProblem



Section13.2.DiagnosticTools



Section13.3.TestingBasicConnectivity



Section13.4.TroubleshootingNetworkAccess

Section13.5.CheckingRouting



Section13.6.CheckingNameService



Section13.7.AnalyzingProtocolProblems



Section13.8.ProtocolCaseStudy



Section13.9.Summary




AppendixA.PPPTools



SectionA.1.Dial-UpIP

SectionA.2.ThePPPDaemon



SectionA.3.chat




AppendixB.AgatedReference



SectionB.1.ThegatedCommand



SectionB.2.ThegatedConfigurationLanguage



SectionB.3.DirectiveStatements



SectionB.4.TraceStatements



SectionB.5.OptionsStatements

SectionB.6.InterfaceStatements



SectionB.7.DefinitionStatements



SectionB.8.ProtocolStatements



SectionB.9.staticStatements



SectionB.10.ControlStatements



SectionB.11.AggregateStatements




AppendixC.AnamedReference

SectionC.1.ThenamedCommand



SectionC.2.named.confConfigurationCommands



SectionC.3.ZoneFileRecords




AppendixD.AdhcpdReference



SectionD.1.Compilingdhcpd



SectionD.2.ThedhcpdCommand



SectionD.3.Thedhcpd.confConfigurationFile

AppendixE.AsendmailReference



SectionE.1.Compilingsendmail



SectionE.2.ThesendmailCommand



SectionE.3.m4sendmailMacros



SectionE.4.Moresendmail.cf





AppendixF.Solarishttpd.confFile



AppendixG.RFCExcerpts

SectionG.1.IPDatagramHeader



SectionG.2.TCPSegmentHeader



SectionG.3.ICMPParameterProblemMessageHeader



SectionG.4.RetrievingRFCs




Colophon



Index


Copyright©2002,1998,1992CraigHunt.Allrightsreserved.
PrintedintheUnitedStatesofAmerica.
PublishedbyO'Reilly&Associates,Inc.,1005GravensteinHighway
North,Sebastopol,CA95472.

O'Reilly&Associatesbooksmaybepurchasedforeducational,
business,orsalespromotionaluse.Onlineeditionsarealsoavailablefor
mosttitles().Formoreinformationcontactour
corporate/institutionalsalesdepartment:800-998-9938or

TheO'ReillylogoisaregisteredtrademarkofO'Reilly&Associates,Inc.
Manyofthedesignationsusedbymanufacturersandsellersto
distinguishtheirproductsareclaimedastrademarks.Wherethose
designationsappearinthisbook,andO'Reilly&Associates,Inc.was
awareofatrademarkclaim,thedesignationshavebeenprintedincaps
orinitialcaps.TheassociationbetweenthelandcrabandTCP/IP
networkadministrationisatrademarkofO'Reilly&Associates,Inc.
Whileeveryprecautionhasbeentakeninthepreparationofthisbook,
thepublisherandtheauthorassumenoresponsibilityforerrorsor
omissions,orfordamagesresultingfromtheuseoftheinformation
containedherein.


Dedication
ToAlana,thebeginningofanewlife.


Preface
ThefirsteditionofTCP/IPNetworkAdministrationwaswrittenin1992.In
thedecadesince,manythingshavechanged,yetsomethingsremain
thesame.TCP/IPisstillthepreeminentcommunicationsprotocolfor
linkingtogetherdiversecomputersystems.Itremainsthebasisof
interoperabledatacommunicationsandglobalcomputernetworking.The
underlyingInternetProtocol(IP),TransmissionControlProtocol,and
UserDatagramProtocol(UDP)areremarkablyunchanged.Butchange

hascomeinthewayTCP/IPisusedandhowitismanaged.
Aclearsymbolofthischangeisthefactthatmymother-in-lawhasa
TCP/IPnetworkconnectioninherhomethatsheusestoexchange
electronicmail,compressedgraphics,andhypertextdocumentswith
otherseniorcitizens.Shethinksofthisas"justbeingontheInternet,"but
thetruthisthathersmallsystemcontainsafunctioningTCP/IPprotocol
stack,managesadynamicallyassignedIPaddress,andhandlesdata
typesthatdidnotevenexistadecadeago.
In1991,TCP/IPwasatoolofsophisticatedusers.Network
administratorsmanagedalimitednumberofsystemsandcouldcounton
theusersforacertainleveloftechnicalknowledge.Nomore.In2002,
theneedforhighlytrainednetworkadministratorsisgreaterthanever
becausetheuserbaseislarger,morediverse,andlesscapableof
handlingtechnicalproblemsonitsown.Thisbookprovidesthe
informationneededtobecomeaneffectiveTCP/IPnetworkadministrator.
TCP/IPNetworkAdministrationwasthefirstbookofpracticalinformation
fortheprofessionalTCP/IPnetworkadministrator,anditisstillthebest.
Sincethefirsteditionwaspublishedtherehasbeenanexplosionof
booksaboutTCP/IPandtheInternet.Still,toofewbooksconcentrateon
whatasystemadministratorreallyneedstoknowaboutTCP/IP
administration.Mostbooksareeitherscholarlytextswrittenfromthe
pointofviewoftheprotocoldesigner,orinstructionsonhowtouse
TCP/IPapplications.Allofthosebookslackthepractical,detailed
networkinformationneededbytheUnixsystemadministrator.Thisbook


strivestofocusonTCP/IPandUnixandtofindtherightbalanceof
theoryandpractice.
IamproudoftheearliereditionsofTCP/IPNetworkAdministration.In
thisedition,IhavedoneeverythingIcantomaintaintheessential

characterofthebookwhilemakingitbetter.Dynamicaddress
assignmentbasedonDynamicHostConfigurationProtocol(DHCP)is
covered.TheDomainNameSystemmaterialhasbeenupdatedtocover
BIND8and,toalesserextent,BIND9.Theemailconfigurationisbased
oncurrentversionofsendmail8,andtheoperatingsystemexamplesare
fromthecurrentversionsofSolarisandLinux.Theroutingprotocol
coverageincludesRoutingInformationProtocolversion2(RIPv2),Open
ShortestPathFirst(OSPF),andBorderGatewayProtocol(BGP).Ihave
alsoaddedachapteronApachewebserverconfiguration,newmaterial
onxinetd,andinformationaboutbuildingafirewallwithiptables.
Despitetheadditionaltopics,thebookhasbeenkepttoareasonable
length.
TCP/IPisasetofcommunicationsprotocolsthatdefinehowdifferent
typesofcomputerstalktoeachother.TCP/IPNetworkAdministrationisa
bookaboutbuildingyourownnetworkbasedonTCP/IP.Itisbotha
tutorialcoveringthe"why"and"how"ofTCP/IPnetworking,anda
referencemanualforthedetailsaboutspecificnetworkprograms.


Audience
ThisbookisintendedforeveryonewhohasaUnixcomputerconnected
toaTCP/IPnetwork.[1]Thisobviouslyincludesthenetworkmanagers
andthesystemadministratorswhoareresponsibleforsettingupand
runningcomputersandnetworks,butitalsoincludesanyuserwhowants
tounderstandhowhisorhercomputercommunicateswithother
systems.Thedistinctionbetweena"systemadministrator"andan"end
user"isafuzzyone.Youmaythinkofyourselfasanenduser,butifyou
haveaUnixworkstationonyourdesk,you'reprobablyalsoinvolvedin
systemadministrationtasks.
[1]Muchofthistextalsoappliestonon-Unixsystems.Manyofthefileformatsand

commandsandalloftheprotocoldescriptionsapplyequallywelltoWindows9x,Windows
NT/2000,andotheroperatingsystems.Ifyou'reanNTadministrator,youshouldread
WindowsNTTCP/IPNetworkAdministration(O'Reilly).

Overthelastseveralyearstherehasbeenarashofbooksfor"dummies"
and"idiots."Ifyoureallythinkofyourselfasan"idiot"whenitcomesto
Unix,thisbookisnotforyou.Likewise,ifyouareanetwork
administration"genius,"thisbookisprobablynotsuitableeither.Ifyoufall
anywherebetweenthesetwoextremes,however,you'llfindthisbookhas
alottooffer.
Thisbookassumesthatyouhaveagoodunderstandingofcomputers
andtheiroperationandthatyou'regenerallyfamiliarwithUnixsystem
administration.Ifyou'renot,theNutshellHandbookEssentialSystem
AdministrationbyÆleenFrisch(publishedbyO'Reilly&Associates)will
fillyouinonthebasics.


Organization
Conceptually,thisbookisdividedintothreeparts:fundamentalconcepts,
tutorial,andreference.Thefirstthreechaptersareabasicdiscussionof
theTCP/IPprotocolsandservices.Thisdiscussionprovidesthe
fundamentalconceptsnecessarytounderstandtherestofthebook.The
remainingchaptersprovidea"how-to"tutorial.Chapter4Chapter7
discusshowtoplananetworkinstallationandconfigurethebasic
softwarenecessarytogetanetworkrunning.Chapter8Chapter11
discusshowtosetupvariousimportantnetworkservices.Chapter12
andChapter13coverhowtoperformtheongoingtasksthatare
essentialforareliablenetwork:securityandtroubleshooting.Thebook
concludeswithaseriesofappendixesthataretechnicalreferencesfor
importantcommandsandprograms.

Thisbookcontainsthefollowingchapters:
Chapter1givesthehistoryofTCP/IP,adescriptionoftheprotocol
architecture,andabasicexplanationofhowtheprotocolsfunction.
Chapter2describesaddressingandhowdatapassesthroughanetwork
toreachtheproperdestination.
Chapter3discussestherelationshipbetweenclientsandserversystems
andthevariousservicesthatarecentraltothefunctionofamodern
internet.
Chapter4beginsthediscussionofnetworksetupandconfiguration.This
chapterdiscussesthepreliminaryconfigurationplanningneededbefore
youconfigurethesystemsonyournetwork.
Chapter5describeshowtoconfigureTCP/IPintheUnixkernel,andhow
toconfigurethesystemtostartthenetworkservices.
Chapter6tellsyouhowtoidentifyanetworkinterfacetothenetwork
software.ThischapterprovidesexamplesofEthernetandPPPinterface


configurations.
Chapter7describeshowtosetuproutingsothatsystemsonyour
networkcancommunicateproperlywithothernetworks.Itcoversthe
staticroutingtable,commonlyusedroutingprotocols,andgated,a
packagethatprovidesthelatestimplementationsofseveralrouting
protocols.
Chapter8describeshowtoadministerthenameserverprogramthat
convertssystemnamestoInternetaddresses.
Chapter9describeshowtoconfiguremanycommonnetworkservers.
ThechapterdiscussestheDHCPconfigurationserver,theLPDprint
server,thePOPandIMAPmailservers,theNetworkFileSystem(NFS),
theSambafileandprintserver,andtheNetworkInformationSystem
(NIS).

Chapter10discusseshowtoconfiguresendmail,whichisthedaemon
responsiblefordeliveringelectronicmail.
Chapter11describeshowtheApachewebserversoftwareisconfigured.
Chapter12discusseshowtoliveontheInternetwithoutexcessiverisk.
Thischaptercoversthesecuritythreatsintroducedbythenetwork,and
describestheplansandpreparationsyoucanmaketomeetthose
threats.
Chapter13tellsyouwhattodowhensomethinggoeswrong.Itdescribes
thetechniquesandtoolsusedtotroubleshootTCP/IPproblemsand
givesexamplesofactualproblemsandtheirsolutions.
AppendixAisareferenceguidetothevariousprogramsusedto
configureaserialportforTCP/IP.Thereferencecoversdip,pppd,and
chat.
AppendixBisareferenceguidetotheconfigurationlanguageofthe
gatedroutingpackage.


AppendixCisareferenceguidetotheBerkeleyInternetNameDomain
(BIND)nameserversoftware.
AppendixDisareferenceguidetotheDynamicHostConfiguration
ProtocolDaemon(dhcpd).
AppendixEisareferenceguidetosendmailsyntax,options,andflags.
AppendixFliststhecontentsoftheApacheconfigurationfilediscussed
inChapter11.
AppendixGcontainsdetailedprotocolreferencestakendirectlyfromthe
RFCsthatsupporttheprotocoltroubleshootingexamplesinChapter13.
ThisappendixexplainshowtoobtainyourowncopiesoftheRFCs.


UnixVersions

MostoftheexamplesinthisbookaretakenfromRedHatLinux,
currentlythemostpopularLinuxdistribution,andfromSolaris8,theSun
operatingsystembasedonSystemVUnix.Fortunately,TCP/IPsoftware
isremarkablystandardfromsystemtosystem,andbecauseofthis
uniformity,theexamplesshouldbeapplicabletoanyLinux,SystemV,or
BSD-basedUnixsystem.Therearesmallvariationsincommandoutput
orcommand-lineoptions,buttheseshouldnotpresentaproblem.
Someoftheancillarynetworkingsoftwareisidentifiedseparatelyfrom
theUnixoperatingsystembyitsownreleasenumber.Manysuch
packagesarediscussed,andwhenappropriateareidentifiedbytheir
releasenumbers.Themostimportantofthesepackagesare:
BIND
OurdiscussionoftheBINDsoftwareisbasedonversion8running
onaSolaris8system.BIND8istheversionoftheBINDsoftware
deliveredwithSolaris,andsupportsallofthestandardresource
records.Therearerelativelyfewadministrativedifferencesbetween
BIND8andthenewerBIND9releaseforbasicconfigurations.
sendmail
Ourdiscussionofsendmailisbasedonrelease8.11.3.Thisversion
shouldbecompatiblewithotherreleasesofsendmailv8.


Conventions
Thisbookusesthefollowingtypographicalconventions:
Italic
isusedforthenamesoffiles,directories,hostnames,domain
names,andtoemphasizenewtermswhentheyareintroduced.
Constantwidth
isusedtoshowthecontentsoffilesortheoutputfromcommands.It
isalsousedtorepresentcommands,options,andkeywordsintext.

Constantwidthbold
isusedinexamplestoshowcommandstypedonthecommandline.
Constantwidthitalic
isusedinexamplesandtexttoshowvariablesforwhichacontextspecificsubstitutionshouldbemade.(Thevariablefilename,for
example,wouldbereplacedbysomeactualfilename.)
%,#
Commandsthatyouwouldgiveinteractivelyareshownusingthe
defaultCshellprompt(%).Ifthecommandmustbeexecutedasroot,
itisshownusingthedefaultsuperuserprompt(#).Becausethe
examplesmayincludemultiplesystemsonanetwork,theprompt
maybeprecededbythenameofthesystemonwhichthecommand
wasgiven.
[option]
Whenshowingcommandsyntax,optionalpartsofthecommandare
placedwithinbrackets.Forexample,ls[-l]meansthatthe-l


optionisnotrequired.


We'dLiketoHearfromYou
Wehavetestedandverifiedalloftheinformationinthisbooktothebest
ofourability,butyoumayfindthatfeatureshavechanged(oreventhat
wehavemademistakes!).Pleaseletusknowaboutanyerrorsyoufind,
aswellasyoursuggestionsforfutureeditions,bywriting:
O'Reilly&Associates,Inc.
1005GravensteinHighwayNorth
Sebastopol,CA95472
(800)998-9938(intheUnitedStatesorCanada)
(707)829-0515(internationalorlocal)

(707)829-0104(fax)
Thereisawebpageforthisbook,wherewelisterrata,examples,orany
additionalinformation.Youcanaccessthispageat:
/>Tocommentorasktechnicalquestionsaboutthisbook,sendemailto:

Formoreinformationaboutbooks,conferences,ResourceCenters,and
theO'ReillyNetwork,seeourwebsiteat:

TofindoutwhatelseCraigisdoing,visithiswebsite,
.


Acknowledgments
Iwouldliketothankthemanypeoplewhohelpedinthepreparationof
thisbook.Allofthepeoplewhocontributedtothefirstandsecond
editionsdeservethanksbecausesomuchoftheirinputlivesoninthis
edition.Forthefirsteditionthat'sJohnWack,MattBishop,Wietse
Venema,EricAllman,JeffHonig,ScottBrim,andJohnDorgan.Forthe
secondeditionthat'sEricAllmanagain,BryanCostales,CricketLiu,Paul
Albitz,TedLemon,ElizabethZwicky,BrentChapman,SimsonGarfinkel,
JeffSedayao,andÆleenFrisch.
Thethirdeditionhasalsobenefitedfrommanycontributorsasurprising
numberofwhomareauthorsintheirownright.Theysetmestraight
aboutthetechnicaldetailsandimprovedmyprose.Threeauthorsare
duespecialthanks.CricketLiu,oneoftheauthorsofthebestbookever
writtenaboutDNS,providedmanycommentsthatimprovedthesections
onDomainNameSystem.DavidCollier-Brown,oneoftheauthorsof
UsingSamba,didacompletetechnicalreviewoftheSambamaterial.
CharlesAulds,authorofabest-sellingbookonApacheadministration,
providedinsightsintoApacheconfiguration.Allofthesepeoplehelped

memakethisbookbetterthanearliereditions.Thanks!
AllthepeopleatO'Reilly&Associateshavebeenveryhelpful.Deb
Cameron,myeditor,deservesaspecialthanks.Debkepteverything
movingforwardwhilebalancingthedemandsofabeautifulnewborn
daughter,BethanyRose.EmilyQuillwastheproductioneditorand
projectmanager.JeffHolcombandJaneEllinperformedqualitycontrol
checks.LeanneSoylemezprovidedproductionassistance.TomDinse
wrotetheindex.EdieFreedmandesignedthecover,andMelanieWang
designedtheinteriorformatofthebook.NeilWallsconvertedthebook
fromMicrosoftWordtoFramemaker.ChrisReilleyandRobertRomano's
illustrationsfromtheearliereditionshavebeenupdatedbyRobert
RomanoandJessamynRead.
Finally,IwanttothankmyfamilyKathy,Sara,David,andRebecca.They
keepmyfeetonthegroundwhenthepressuretomeetdeadlinesis


drivingmeintoorbit.Theyarethebest.


Chapter1.OverviewofTCP/IP
AllofuswhouseaUnixdesktopsystemengineers,educators,scientists,
andbusinesspeoplehavesecondcareersasUnixsystemadministrators.
Networkingthesecomputersgivesusnewtasksasnetwork
administrators.
Networkadministrationandsystemadministrationaretwodifferentjobs.
Systemadministrationtaskssuchasaddingusersanddoingbackups
areisolatedtooneindependentcomputersystem.Notsowithnetwork
administration.Onceyouplaceyourcomputeronanetwork,itinteracts
withmanyothersystems.Thewayyoudonetworkadministrationtasks
haseffects,goodandbad,notonlyonyoursystembutonothersystems

onthenetwork.Asoundunderstandingofbasicnetworkadministration
benefitseveryone.
Networkingyourcomputersdramaticallyenhancestheirabilityto
communicateandmostcomputersareusedmoreforcommunicationthan
computation.Manymainframesandsupercomputersarebusycrunching
thenumbersforbusinessandscience,butthenumberofthesesystems
inusepalesincomparisontothemillionsofsystemsbusymovingmailto
aremotecolleagueorretrievinginformationfromaremoterepository.
Further,whenyouthinkofthehundredsofmillionsofdesktopsystems
thatareusedprimarilyforpreparingdocumentstocommunicateideas
fromonepersontoanother,itiseasytoseewhymostcomputerscanbe
viewedascommunicationsdevices.
Thepositiveimpactofcomputercommunicationsincreaseswiththe
numberandtypeofcomputersthatparticipateinthenetwork.Oneofthe
greatbenefitsofTCP/IPisthatitprovidesinteroperablecommunications
betweenalltypesofhardwareandallkindsofoperatingsystems.
Thename"TCP/IP"referstoanentiresuiteofdatacommunications
protocols.Thesuitegetsitsnamefromtwooftheprotocolsthatbelongto
it:theTransmissionControlProtocol(TCP)andtheInternetProtocol(IP).
TCP/IPisthetraditionalnameforthisprotocolsuiteanditisthename


usedinthisbook.TheTCP/IPprotocolsuiteisalsocalledtheInternet
ProtocolSuite(IPS).Bothnamesareacceptable.
Thisbookisapractical,step-by-stepguidetoconfiguringandmanaging
TCP/IPnetworkingsoftwareonUnixcomputersystems.TCP/IPisthe
leadingcommunicationssoftwareforlocalareanetworksandenterprise
intranets,anditisthefoundationoftheworldwideInternet.TCP/IPisthe
mostimportantnetworkingsoftwareavailabletoaUnixnetwork
administrator.

ThefirstpartofthisbookdiscussesthebasicsofTCP/IPandhowit
movesdataacrossanetwork.Thesecondpartexplainshowtoconfigure
andrunTCP/IPonaUnixsystem.Let'sstartwithalittlehistory.


1.1TCP/IPandtheInternet
In1969theAdvancedResearchProjectsAgency(ARPA)fundeda
researchanddevelopmentprojecttocreateanexperimentalpacketswitchingnetwork.Thisnetwork,calledtheARPAnet,wasbuilttostudy
techniquesforprovidingrobust,reliable,vendor-independentdata
communications.Manytechniquesofmoderndatacommunicationswere
developedintheARPAnet.
Theexperimentalnetworkwassosuccessfulthatmanyofthe
organizationsattachedtoitbegantouseitfordailydata
communications.In1975theARPAnetwasconvertedfroman
experimentalnetworktoanoperationalnetwork,andtheresponsibilityfor
administeringthenetworkwasgiventotheDefenseCommunications
Agency(DCA).[1]However,developmentoftheARPAnetdidnotstopjust
becauseitwasbeingusedasanoperationalnetwork;thebasicTCP/IP
protocolsweredevelopedafterthenetworkwasoperational.
[1]DCAhassincechangeditsnametoDefenseInformationSystemsAgency(DISA).

TheTCP/IPprotocolswereadoptedasMilitaryStandards(MILSTD)in
1983,andallhostsconnectedtothenetworkwererequiredtoconvertto
thenewprotocols.Toeasethisconversion,DARPA[2]fundedBolt,
Beranek,andNewman(BBN)toimplementTCP/IPinBerkeley(BSD)
Unix.ThusbeganthemarriageofUnixandTCP/IP.
[2]Duringthe1980s,ARPA,whichispartoftheU.S.DepartmentofDefense,became
DefenseAdvancedResearchProjectsAgency(DARPA).WhetheritisknownasARPAor
DARPA,theagencyanditsmissionoffundingadvancedresearchhaveremainedthe
same.

AboutthetimethatTCP/IPwasadoptedasastandard,thetermInternet
cameintocommonusage.In1983theoldARPAnetwasdividedinto
MILNET,theunclassifiedpartoftheDefenseDataNetwork(DDN),anda
new,smallerARPAnet."Internet"wasusedtorefertotheentirenetwork:
MILNETplusARPAnet.


In1985theNationalScienceFoundation(NSF)createdNSFNetand
connectedittothethen-existingInternet.TheoriginalNSFNetlinked
togetherthefiveNSFsupercomputercenters.Itwassmallerthanthe
ARPAnetandnofaster:56Kbps.Still,thecreationoftheNSFNetwasa
significanteventinthehistoryoftheInternetbecauseNSFbroughtwithit
anewvisionoftheuseoftheInternet.NSFwantedtoextendthenetwork
toeveryscientistandengineerintheUnitedStates.Toaccomplishthis,
in1987NSFcreatedanew,fasterbackboneandathree-tierednetwork
topologythatincludedthebackbone,regionalnetworks,andlocal
networks.In1990theARPAnetformallypassedoutofexistence,andin
1995theNSFNetceaseditsroleasaprimaryInternetbackbone
network.
TodaytheInternetislargerthaneverandencompasseshundredsof
thousandsofnetworksworldwide.Itisnolongerdependentonacore(or
backbone)networkorongovernmentalsupport.Today'sInternetisbuilt
bycommercialproviders.Nationalnetworkproviders,calledtier-one
providers,andregionalnetworkproviderscreatetheinfrastructure.
InternetServiceProviders(ISPs)providelocalaccessanduserservices.
ThisnetworkofnetworksislinkedtogetherintheUnitedStatesatseveral
majorinterconnectionpointscalledNetworkAccessPoints(NAPs).
TheInternethasgrownfarbeyonditsoriginalscope.Theoriginal
networksandagenciesthatbuilttheInternetnolongerplayanessential

roleforthecurrentnetwork.TheInternethasevolvedfromasimple
backbonenetwork,throughathree-tieredhierarchicalstructure,toa
hugenetworkofinterconnected,distributednetworkhubs.Ithasgrown
exponentiallysince1983doublinginsizeeveryyear.Throughallofthis
incrediblechangeonethinghasremainedconstant:theInternetisbuilt
ontheTCP/IPprotocolsuite.
Asignofthenetwork'ssuccessistheconfusionthatsurroundstheterm
internet.Originallyitwasusedonlyasthenameofthenetworkbuiltupon
IP.Nowinternetisagenerictermusedtorefertoanentireclassof
networks.Aninternet(lowercase"i")isanycollectionofseparate
physicalnetworks,interconnectedbyacommonprotocol,toformasingle
logicalnetwork.TheInternet(uppercase"I")istheworldwidecollectionof
interconnectednetworks,whichgrewoutoftheoriginalARPAnet,that


usesIPtolinkthevariousphysicalnetworksintoasinglelogicalnetwork.
Inthisbook,both"internet"and"Internet"refertonetworksthatare
interconnectedbyTCP/IP.
BecauseTCP/IPisrequiredforInternetconnection,thegrowthofthe
InternetspurredinterestinTCP/IP.Asmoreorganizationsbecame
familiarwithTCP/IP,theysawthatitspowercanbeappliedinother
networkapplicationsaswell.TheInternetprotocolsareoftenusedfor
localareanetworkingevenwhenthelocalnetworkisnotconnectedto
theInternet.TCP/IPisalsowidelyusedtobuildenterprisenetworks.
TCP/IP-basedenterprisenetworksthatuseInternettechniquesandweb
toolstodisseminateinternalcorporateinformationarecalledintranets.
TCP/IPisthefoundationofallofthesevariednetworks.

1.1.1TCP/IPFeatures
ThepopularityoftheTCP/IPprotocolsdidnotgrowrapidlyjustbecause

theprotocolswerethere,orbecauseconnectingtotheInternetmandated
theiruse.Theymetanimportantneed(worldwidedatacommunication)
attherighttime,andtheyhadseveralimportantfeaturesthatallowed
themtomeetthisneed.Thesefeaturesare:
Openprotocolstandards,freelyavailableanddeveloped
independentlyfromanyspecificcomputerhardwareoroperating
system.Becauseitissowidelysupported,TCP/IPisidealforuniting
differenthardwareandsoftwarecomponents,evenifyoudon't
communicateovertheInternet.
Independencefromspecificphysicalnetworkhardware.Thisallows
TCP/IPtointegratemanydifferentkindsofnetworks.TCP/IPcanbe
runoveranEthernet,aDSLconnection,adial-upline,anoptical
network,andvirtuallyanyotherkindofphysicaltransmission
medium.
AcommonaddressingschemethatallowsanyTCP/IPdeviceto
uniquelyaddressanyotherdeviceintheentirenetwork,evenifthe
networkisaslargeastheworldwideInternet.