Embedded Security Improvements to IPv6

Rochester Institute of Technology

RIT Scholar Works

Theses

Thesis/Dissertation Collections

2004

Embedded Security Improvements to IPv6

Mark Merlino

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Recommended Citation

Embedded

Security

Improvements

to

IPv6

By

Mark

Merlino

Thesis

submitted

in

partial

fulfillment

of

the

requirements

for the

degree

of

Master

of

Science in Information

Technology

Rochester

Institute

of

Technology

B. Thomas Golisano

College

of

Computing

and

Information

Sciences

Rochester Institute of Technology

B. Thomas Golisano College

of

Computing and Information Sciences

Master of Science in Information Technology

Thesis Approval Form

Student Name:

Mark Merlino

Thesis Title:

Embedded Security Improvements to Ipv6

Thesis Committee

Name

Signature

Date

Prof. Sharon Mason

Chair

Evelyn Rozanski. Ph.D

Committee Member

Thesis Reproduction Permission Form

Rochester Institute of Technology

B.

Thomas Golisano College

of

Computing and Information Sciences

Master of Science in Information Technology

Embedded Security Improvements to IPv6

I, Mark Merlino, hereby grant permission to

the

Wallace Library of the Rochester

Institute of Technology to reproduce my thesis in whole or in part. Any

reproduction must not be for commercial use or profit.

Table

of

Contents

Introduction 2

Networks 4

NetworkCommunications 7

Network Transmission Methods 14

Mediums 16

Electromagnetic Signals 21

Portal Devices 22

Internets 27

InternetService Providers 28

Domains 30

Communication Architectures 32

OSI Model 37

TCP/IP 40

Internet Protocol 42

Internet Protocol Version6 51

IntrusionsandDetections 63

Viruses 82

Security

Controls 90

Certificate

Authority

93

IP

Security

Architecture 98

Human Interaction 104

Hackers 108

Coding

Ethics 110

Spreading

ofViruses Ill

Profits form Virus Propagation 117

RoleofGovernment Agencies 120

VendorSupportofIPv6 126

Conclusion 131

Acronyms 134

Endnotes 136

Bibliography

140

AddendumA Figures 141

Introduction

Today'sbusinessesandhomeconsumershave spent vast amounts of_moneyandfinancial

resources on e-business commerce and enterprise solutions. Thesesolutionsandtheir

associated applications aredesignedtoacquire andbuildcustomerassociationsthatallow

businessto grow,frombothcorporate and personal consumer perspectives. E-business

andtheInformation

Technology

industry

havegrown

dramatically

overthelasttwo

decades allowingbusinessestoexpandintothecyber-tech world oftheInternet. Ina

short period of

time,

this technologicaldevelopment haspermittedcomputer

communicationsthroughvastnetworksusedforentertainment,

business,

andservices.

Forthesenetworks_{to operate,}specific standardsthatallow communicationto takeplace

arenecessary. Thesestandardshave changed

dramatically

asthe typeofinformationthat

is transmittedhas changed.Communications

involving

_merelyvoice anddataare no

longersufficient.

Today,

communication systemsthatinclude imageand video are

essential. Thistype ofinformation sharinghascreated newtechnologies thatallowdata

transfertosupport_{many hardware}and softwaredistributedsystems.

TCP/IP isaprotocolthatispartof a communication standardthatdefinesthe

groundworkfortheInternet. Thereare other communication_{standards, but}almost all

computer and software vendors nowutilizetheTCP/IPprotocol as part of an overall

networkthathandlescommunicationsbetweencomputers.Thesestandards permitbasic

services such aselectronicmail,file

transfer,

and remotelogincapabilities across large

numbersofclient/serversystems

to,

_{ultimately,provide end users withthe}

communicate and share datawith_virtuallyanyone connectedtoacomputer network. As

muchasthisprotocol providesincreasedcommunication_{capabilities,}ithasadownside.

Rangesofinherentproblemshave surfaced~ fromthe_system

being

fragiletoexternal

threats_arisingfromunauthorized use ofthisprotocoltoaccessbusinessandpersonal

computers. The originalconcept oftheInternetwas an

information-sharing

medium.The

developmentofthismediumwas shared_amongafew_{parties, the}governmentand

selected universities. Itwas _essentiallyarchitectedto transmitdata. Thecomplexities

seenwithtoday'sInternetevolvedfromtheseoriginal concepts.

They

alsoincorporate

updatesthataddresscriticalproblemsthatdevelopedthroughInternetusage.

Thebiggestconcernfortoday'suserissecurity.BecausetheInternetwas notdesigned

with_{security in}mind,itcontains_manyopeningsfor intrusions. As development

continued,changeswere madetoaddress_{these concerns,}buttherapid growthofInternet

usage prevented wholesalefixes from

taking

place inatimeframe thatwarranted secure

implementation.

Instead,

_somethingnew neededtobe devisedthatwouldaddress

securityalongwith other_{outstanding issues}suchasbandwidth andaddressing. This

solutionwas anew architected versionofthe

Internet,

knownasIPv6. Thisversionisto

replace

IPv4,

whichis currently inuse.Oneof

IPv6'

s mainintentions istoaddress

security issues

by incorporating

embedded_securitythatcan solve_manyofthecommon

privacyandencryptionproblemstowhichthecurrentIPv4is subject. Thegoal ofthis

thesisistoexploretheaspects ofthisnewarchitectureinrelationto_{the old,}andto

determinewhetheror not_{Internet security}issuescanbeminimized or eveneliminated

Networks

Computer

interoperability

isthemannerinwhich computers worktogetherasa

networked system.Forcomputerstowork

together,

they

needtoshareresources

connectedtogetherwith software andhardwarecomponentsthatmake_upanetwork. The

guidelinesthat thesenetworksfollowareknownas standards (expectedperformanceof

all networked_elements) and protocols(interactionoftheseelements).Network

architectures canbe_{designed in many}ways

depending

upon client needs.After

establishingclient_{requirements, then the type}ofnetwork canbe

determined,

from

software_operatingsystemsto thesoftware programs neededtoallow communication

betweenthehardwarecomponentsofthesystem. The Internetutilizesthesecomponents

inthesame network model. Internetcommunication accessis basedupontheTCP/IP

protocolandis_readilyused

by

_manycomputersystems astheirstandard_networking

protocol. Becauseofthe

flexibility

oftheTCP/IPprotocol,other protocols such as

Apple's File

Protocol,

Microsoft

NetBIOS,

andNovell IPXcanstillbeused.As indicated

earlier,networkscanbeconstructed_{in many different}fashions

depending

uponthe

architectural requirementsofthesystem. Examplesofdifferentnetworked systems are

shownbelow:

LAN's

-Asmall numberto_{many individual}computer clients connectedtoa

centralized computer(server).Theserver canbeequipped with specific software

thatis shared_amongindividualclients as well as specializedapplicationsthat

monitorand manageadditional programs.

Ethernet- These

systems are computersinterconnected

by

_cablingthatrunfrom

computer. Moreoften_{than not,}Ethernetcards arelocatedwithinthecomputer

expansion slots and are connected attheinterfacepoint wherethecableconnector

snaps intoplace. Thesecables_maybeattachedtoahub (made forthevarious

media

types)

that,

depending

upon_{signaling architecture,}canaccommodate_upto

agigabit signaltransmissionrate.

Token-Ring

- This

network configuration connectsthecomputers andperipherals

toseparate_{wiring hubs.} One disadvantageof a

Token-Ring

configurationis

that,

ifpower or connectionis

lost,

thedevicewillbe disconnected fromthesystem.

Structured

Wiring

- This

type of_wiringsystemprovidesastandardizedsystem

for_wiringa

building

toaccommodate alltypesof networks.

Cabling

canbe

locatedinpanelslocatedina centralizedareaforaccessthatexpands outto

specificnetwork connections inwalljacksasdesigned.

Peer-to-Peer- This

typeofnetworkdoesnot containadedicated server,but

insteadsharestheprocesses ofthenetworkedclients.File serverprograms can

stillbe loadedand_utilized,but

they

are resident on one ofthenetworked

computersand utilizetheresourcesdictated

by

theuser_usingthatparticular

computer.Thistypeofnetwork makesit easyforotherstoshare resources and

canbe economically satisfying ifthesystem remains_relativelysmall.

Enterprise- These

systems provide an overall management systemthatutilizes

software programs called agentstogatherinformationinaformat knownas a

MIB. This information istransferred toadditional_programs,which can

comprehendtheinformationon overall system performance and create

conditionsthatexceed specified

limits;

inventory

_existingsystems

by

_gathering

statisticsondata

transfer,

performdata

backups,

and alerttheappropriate system

Network

Communications

The

telegraph,

_{using Morse}Codeas it'smeans of_{sendingcommunications,}key- punch

terminals,

andBaudot'steletypewritercode arethebeginningsto today'sASCIIcode. It

is widelyaccepted,butnot_necessarilyuniversalin it'sacceptance as anetwork code.

IBMdevelopedand still usestheirown_code,EBCDICincurrentmainframes and

computers.Withincreasedcomputer_availabilityand subsequent_usage, it became

apparentthat

they

neededtoworktogetheras synchronized units.Continued

development began spawningnewtechnologiessuch astheInternet. Originalintentions

ofthe

Internet,

firstproposed

by

theARPAandlater developed

by

theDARPA

l,

were

designedas a

testing

methodfor_sendingpackets ofinformationover networks.Asthe

ARPA_network, orARPANETcontinuedto

develop,

modificationsallowedforincreased

usage,andexpandedfrompredominant_militaryusetocommercialvenues such as

universities. Thisworkledto thedevelopmentofan_{earlyprotocol, the}networkcontrol

program,andlater became TCP/IP

2. Quickly

itwas evidentthat thenetwork could not

handletheamount ofnetworktrafficit beganreceiving. Itwas also apparentthat

Network Administrators becamereluctanttosharetheirnetwork resourcesbecause of

concerns about security.

Clearly,

common

technologies,

or standards neededtobe

introducedtoallow communicationbetween differentnetworks._{The early} 1970's

showedhownew communication

functionality

couldbe_connected,regardless ofthe

operatingsystemplatform. The

ITU-T,

_alongwiththe

ISO,

ARPA,

and

DARPA,

developedthe initialconceptsof networking. Thesestandards would allow_anycomputer

version oftheTCP/IPprotocol and madeitavailable as publicsoftware. Becausethis

software was not_proprietary,both public and private sectors adopteditquickly.

Many

of

today'sversions oftheTCP/IPprotocolhavetheiroriginsfromthe

Berkeley University

release, as itsoonbecamethestandardfor datacommunicationsprotocols.

RapiddevelopmentoftheInternetforcedthedevelopmentoforganizationstomonitor

expansion and maintain control.These_{organizations,} or

bodies,

such astheIETF

establish guidelines3thatprotocolsfollow_{regarding implementation}as well asstandards

for fiitureresearch.The IETFis composed of an openinternational communityof

network

designers,

_{operators, vendors,} andresearchers concernedwiththeevolution of

theInternetarchitecture andthesmooth operation ofthe Internet. The IETFis broken

down into workinggroups and managed

by

Area Directorsthatare membersofthe

Internet

Engineering Steering

Group. The Area Directorsthatprovidearchitectural

oversightis knownastheLAB. The LABalsooversees appealswhenthereare registered

complaints. The IANAisthe central coordinatorfortheassignment ofuniqueparameter

valuesfor Internetprotocols. The IANA ischartered

by

theISOCtoact asthe

clearinghousetoassignand coordinatetheuse of numerousInternetprotocol parameters.

Withinthe_{LETF working group} are specific areas and chartersthatarefollowed. There

are 8 areasthatformthisgroup:

Applications,

General, Internet,

Operationsand

Management,

Routing,

Security, Sub-IP,

andTransport. Eachoftheseareasis

responsiblefora specific aspect oftheInternet.Forexample, theOperationsand

Management working group areahouses(orholds or_contains)additionalsub-areas.

These areas areassignedtospecific groups who will overseethem.V6ops isone such

area. Thecharter 4

The globaldeploymentofLPv6is_{underway,creating}anLPv4/LPv6 Internet

consistingof

LPv4-only,

LPv6-only

andLPv4/LPv6networks andnodes. This

deploymentmustbe_properlyhandledtoavoidthedivisionoftheInternet into

separateIPv4 andIPv6networks while _ensuringglobal_addressingand

connectivityforallIPv4andIPv6nodes. Thev6opsdevelops guidelinesforthe

operation of a sharedLPv4/LPv6 Internetand provides guidancefornetwork

operators onhowto

deploy

IPv6_{into existing}

LPv4-only

_networks,as well asinto

new networkinstallations.

Thev6ops_{working group}will:

1. Solicitinput fromnetwork operators and usersto

identify

operationalor

security issueswiththeLPv4/LPv6

Internet,

anddetermine solutions or

workaroundsto thoseissues. This includes

identifying

standards workthatis

neededinotherLETFWGsorareas and_workingwiththosegroups/areastobegin

appropriate work.Theseissueswillbe documented in InformationalorBCP

RFC's,

orin Internet-Drafts. For_example,importantpieces oftheInternet

infrastructuresuch as

DNS,

SMTPandSLPhavespecific operationalissueswhen

they

operateina sharedLPv4/LPv6network.Thev6opsWGwillcooperate with

therelevantareas andWGstodocumentthose

issues,

andfindprotocol or

operationalsolutionsto thoseproblems.

2. Provide feedbackto the_{IPv6 WG regarding}portions oftheIPv6specifications

that cause, or are

likely

_{to cause,}operational or_{security concerns,}and work with

3. Publish InformationalRFC'sthat

help

applicationdevelopers (withinand

outsidethe

LETF)

understandhowto

develop

LPversion-independent

applications. _{This working group}will work withtheApplicationsarea, among

others, to ensurethat thesedocumentsanswerthereal-world concerns of

applicationdevelopers. Thisincludes

helping

to

identify

IPv4dependencies in

existing LETFapplication protocols and_workingwith other areas and/or groups

withintheLETFtoresolvethem.

4. Publish Informational orBCPRFC'sthat

identify

potential_securityrisksinthe

operation of sharedLPv4/LPv6_networks, anddocumentoperational practicesto

eliminate or mitigatethoserisks. Thiswork willbe done incooperationwiththe

Security

areaand other relevantareasor_workinggroups.

5. Publish InformationalorBCP RFC'sthat

identify

and analyze solutionsfor

deploying

IPv6withincommonnetwork_{environments,} such as ISP Networks

(including

Core, HFC/Cable,

DSL &

Dial-up

_networks),Enterprise

Networks,

UnmanagedNetworks(Home/Small

Office),

andCellular Networks. These

documentsshould serve as useful guidestonetwork operators and users

regarding howto

deploy

IPv6withintheir_{existing IPv4networks,} as well as in

new networkinstallations.

6.

Identify

openoperational or_securityissueswiththe

deployment

scenarios

InformationalRFC's.

They

will worktofindworkarounds or solutionsto

basic,

IP-leveloperational or_securityissuesthatcanbe solved_{using widely}applicable

transition mechanisms,such as

dual-stack,

tunneling

ortranslation.Ifthe

satisfactoryresolution of an operational or_securityissuerequiresthe

standardization of a_new,widely-applicabletransitionmechanismthatdoesnot

properlyfit intoanyotherLETF WGorarea, thev6opsWGwillstandardizea

transitionmechanismtomeetthatneed.

7. Assume responsibilityfor_advancingthebasicIPv6transitionmechanism

RFC's alongthestandards_track,iftheir_{applicability}tocommondeployment

scenariosisdemonstrated in:

Transition Mechanisms(RFC

2893)

SET (RFC

2765)

NAT-PT(RFC

2766)

6to4 (RFC 3056 &

3068)

This includes updatingthese mechanisms,as_{needed, to}resolve problems.In

some_{cases, these}mechanisms maybedeprecated(i.e. movedto

Historic),

if

they

arenotfoundtobeapplicableto the deploymentsolutionsdescribed in

(5)

orif

seriousflawsare encounteredthatleadustorecommend againsttheiruse.IPv6

operationalanddeployment issueswith specific protocols ortechnologies(such

as

Applications,

Transport

Protocols,

Routing

Protocols,

DNSorSub-IP

those areas/groups,as_needed,and cooperate withthose areas/groups in

developing

and_reviewingsolutionstoLPv6operationalanddeployment

problems5.

Asof

August,

2003 this_grouphad_onlyone

RFC,

3574. RFC'sare papersdesignedas

informationtobeused

by

theInternetcommunity.

They

are notinthemselvesa_standard,

butare used as a referencein

helping

to

develop

Internetstandards.

Thisorganizationhas becomevitalas otherorganizations_utilizingtheTCP/LPprotocol

began

developing

theirown networks. The NSF established anetworkthatwas managed

jointly by

MCI,

Sprintlink,

andLBM. Withthiscooperative effort cametheformationof

ANS,

whichdevelopedaccessto theInternet

by

_{using NAP. This}allowed connectionto

multiple networksin both public and private sectors. Sincetheinitial designofthe

Internetdidnot anticipatethe_popularityandwidespreadusage_{that occurred,}ANS

becamevital. Itwas alsoimportant because it begantoaddresstheproblem of electronic

security

intrusions,

which werenot anticipated withtheinitial design.

Asthe_popularityoftheInternet_grew,sodidthepotentialforunwanted accesstocomputer

systems.Fora myriadof_reasons,intrudersbegan

discovering

waystoexploit software andthe

networksthattiethem together.

Controlling

specific computers allowedintruderstomasktheir

trueidentitiesandlaunchattacksthroughdonorcomputers,_causingdamage

by

_{changing data}or

destroying

componentssuch ashard drives.

Having

thelatestanti-virus software and_operating

systempatchescanminimize_{these risks,}butwill not

totally

eliminatethem. These

fixes

do

help

in

detection,

but

they

onlymasktheroot cause of_securitydesign

deficiencies.

_Achangeinthe

TCP/LPprotocol continues_{to evolve,many}oftheinherentrisks associated withitcanbe

removed.

Stillthatdoesnot alleviateissues_surroundingcurrent networked systems. Intoday's

environmentthe_majorityof attacksonsystems comefroma_relativelysmall numberofsoftware

vulnerabilities. Attackerscanbe_generallycountedon_{to take the easiest,}most exploitedroute,

using verysophisticatedtools tocompromise a system.

Often, they

searchtheInternetfor

Network Transmission Methods

Networktransmissionrefersto the

technology

and linesthat_carrythedata information.

Digitalservices such asISDNandDSLuse_existingtelephonenetworks.Othercommon

examplesincludecoaxial cable_modems,whichtransmitandreceivedataoverlocal TV

cables, twistedpair

(including

_shielded),andfiberoptic.Thesetypesofdatatransmission

linesusedevices such as

hubs,

_{switches, repeaters,}

bridges,

and routerstodirectand

providedifferent levels ofdata

handling

overthenetwork.

Essentially,

thisallows

applications onpersonalcomputers_{to engage,}

transfer,

anddelivervoice,

fax,

anddata

informationtoother personal computers. Each device hasa specific rolein

delivering

the

informationtoits desiredlocationwhile_maintainingthe

integrity

ofthe original message.

These

devices,

alsoknownasportal

devices,

areusedas pointsina networktomonitor

anddetect

incoming

breaches,

butalso posepotentiallinksthatcanbe vulnerableto

security intrusions.

Exploring

each_{component, the}mediumsthat_carrythe

information,

andthe_{information itself (electromagnetic signals)}that_makeupa network can expose

securityvulnerabilitiesthatexist withineach component ofthenetwork.

Datacommunicationsmediathattravel thesedifferentmediums canbecategorizedinthe

formof guidedorunguided.Guidedmedia_carryelectromagnetic signals_{along hardware}

such as coaxial cables, twistedpair, and opticalfiber. Unguidedmedia dealswith(or

encompasses)wireless communications. _{The quality}ofdatatransmissionsis

dependent

uponthemediumused andthecharacteristics oftheelectromagnetic signal.Both

transmissionshavecharacteristicsthatcanimpactthe transmissionquality.Inguided

electromagnetic signal.Forunguided_{media, the} signalstrengthismorecriticalthan the

transmitting

medium. Thereare_{basic factors}thatare

key

to

determining

correct

transmissionsystems:

Bandwidth

-generallythegreaterthe

bandwidth,

thegreaterthesignal_quality

Impairments

-canlimitsignaldistance

Interference

-overlappingsignals can impactor

destroy

signals

Receivers

Mediums

Thephysical aspect oftwistedpair mediums consists oftwoinsulatedcopper wires

twisted togetherina spiral. Thesearethenbundledtogether

by

thehundredsintoa

shielded cable.

They

haveatwistedcharacteristicbecauseittends toreduceinterference

betweenothertwistedpairs contained withinthecable.

Today,

twistedpairisthemost

common medium usedfor_{both analog}anddigitaltransmissions.Itisused_{extensively in}

telephoneand office networks as well as private residencesthatare connectedto thelocal

telephone exchanges. Theoriginal conceptofthe twistedpairwastosupportvoicetraffic

using analogsignals,butwiththeadventof_{the modem,}digital signalingcanbe

transmitted_alongthesewires._{Digital signaling}iscommoninofficesthatuselocal-area

networksto supportcomputer systems.Dataratescan_varywithtwistedpair_wiringwith

commontransferrates of_{approximately 10 Mbps}tohigh-endrates of_{approximately 100}

Mbpsfor_veryshortdistances. Thereare_{many factors}thatcandeterminerates from

geographicdistancesto thenumberofdevices connectedto thenetwork.

Twistedpair_{wiring has limitations}thatneedtobeconsidered. Distancesof5kilometers

ormorerequire amplifiersfor_analogsignals anddistancesof2 kilometersor more

require repeatersfor digitalsignals. Interferenceand noise can alsoimpactsignal strength

andclarity.Thisimpedancecanbeovercomewith_shieldingof metallicbraidor

sheathingthatsurroundsthewire.Becausetwistedpair_wiringisavailable in different

shieldedandunshielded_categories, designneedstobetakenintoconsiderationto

thoroughly

understandthenetwork requirements andtypesof peripheralsthatwillbe

Coaxialcables are constructed

differently

than twistedpair and allow agreater numberof

frequencies

tobetransmitted._{Both analog}anddigitalsignals canbetransmittedathigher

frequencies

anddatatransferratesthan typical twistedpair wiring.

Essentially,

coaxial

cableisa single copperinnerwire surrounded

by

a conductor and shielded with an outer

layer forprotection. Thisouter_protection,or_shielding, offers greaterinterference

protectionthanis offered

by

twistedpair wiring. _{Coaxial cabling}offers alarge varietyof

applications,fromtelevisionandtelephone systemstonetworked computersystems. The

advantages of coaxial cables includethe_abilitytoprovidehigh-speeddatatransfertoa

largenumber ofdevicesover shorterdistancessuch aslocal

building

complexes.For

longer distancescoaxial cables are similarto twistedpairinthat

they

require amplifiers

for_analogsignals and repeatersfor digitalsignals.Bothtwistedpairand coaxial cables

arelimited_only

by

theinherentphysical characteristics

they

possess.

Optical_{fiber technology,} as opposedto twistedpair and coaxial_{cabling has} created a

networking breakthrough incommunicationsystems. Itscharacteristics permitlong-range

communicationswiththeassociatedbenefitsof greater_{capacity from}a reduced cost

base. Opticalfibersconsist of a_{thin, flexible}medium(fibersthataremade fromvarious

gassesandplastic_materials)that transmitsanopticalimpulse.Thesefibers are

constructed

by

_creatingacore(twomediumsthathave differentrefraction

characteristics)surrounded

by

_claddingand a protectiveouterjacket. Optical_cabling

contains_{many independent}fibers ina single package withfarsuperior performance

The advantages offiberoptic overtwistedpair and coaxial mediums rangefrom:

Capacity

-Increased

bandwidth,

allowingdatarates of2 Gbpsover_many

kilometers havebeenachieved as comparedto100's ofMbpsoveradistanceof

upto2 kilometersforcoaxial cable and afewMbpsover adistanceof_uptoa

singlekilometerfortwistedpair.

SizeandCost

-Considerably

smallerin_size,itcantranslate_{into greatly}reduced

structural requirements_creating cost savings

during

installation. Optical fiber

doesnot require as_manyrepeaterswithinthenetwork.

Interference

-Fiberopticisnotimpacted

by

electromagneticfields so

interferenceandnoiseare_greatlyreduced.

Security

- Fiber

opticprovidesa muchhigher degreeof_{security because it is}

difficulttointercepttransmissionswithoutdetectioninthe typicalconstructs used

inpoint-to-pointmediums.

Asnetworked systems continueto evolve, fiberoptictechnologieswillbecomemore

prevalent.

They

are

increasingly

being

usedinthe telephone

industry

dueto thebenefits

ofincreased bandwidth capacityand greater routedistances. Thegreaterbandwidth

allowsforgreater_{capacity to}handletheincreaseddemandforvoice,

data, image,

and

videotransfer. Thegreaterdistancemeanslocalizednetworked systemsdonot needthe

addedrepeatersseenintwistedpairand coaxialsystems.

Finally,

the_{increased security}

offiberoptic _cablingfaroutweighsthevulnerabilities exhibited

by

twistedpair and

Othertechnologiessuch as wireless

(radio,

_microwave,and_satellite)do exist,but

they

present a_completelydifferent set of_securityissues.Forthepurposesofthis

discussion,

thefocuswillbeon guided mediums such as_{twisted pair,}coaxialandfiberopticcabling,

Electromagnetic

Signals

Allformsofdata transmission, either

by

_voice, dataor video useelectromagnetic signals

thataretransmittedovertheir_{corresponding}medium. Theinformation iscreated

by

a

source such as a computerterminal. Theinformationisconvertedintoan electromagnetic

signal, andthencarried over a_{transmission medium,} such asfiber optic_cable,fromthe

transmitter to thereceiver. Thereceiverthenretrievestheelectromagneticsignaland

[image:24.519.91.457.276.488.2]

reproducesit intotheoriginal(or_approximate) form inwhichtheinformationwas sent

(Figure 1).

Electromagnetic Signal (Data

Transmission)

A ?

Transmitter

or

Receiver

Transmitter

or

Receiver

Transmission

Information

(Computer)

Medium

(Cable)

Information

(Computer)

Figure 1 - Example_ofData Transmission

Electromagneticsignals (either analogor

digital)

canbe lookedatfromtwodifferent

perspectives. The firstsuchperspective,time-domain, is afunctionoftime.An_analog

Thewave ofthe_analogsignalis made_upofthreecomponents:

Amplitude

-strength ofthesignal

Frequency

-rate at whichthesignal repeats itself.Therange offrequenciesis

knownasthespectrum ofthesignal.

Phase

-positionintimewithina single period of a signal

Thereare nobreaksinan_analogsignal whereas adigitalsignal maintains aconstantlevel

fora period oftime thenchangestoanotherconstantlevel fora periodoftime.The

secondsuchperspectiveis adigitalsignalthatisrepresented

by

electromagneticpulses

represented

by

two

binary

digits,

0and1. Thewavelengthisthedistanceof a single cycle

andthebandwidthof asignalisthewidth ofthespectrum.This information iscritical

becausethereisa_{direct relationship between}theamount of

information,

and_capacityof

asignalandits bandwidth.

Essentially,

the greaterthe

bandwidth,

thegreatertheamount

ofinformationthatcanbetransmitted.Thereis onedownsidetoconsider with

bandwidth;

thegreaterit

is,

thegreatertheassociated cost.Mediumstransferinformation

atdifferentrates and,

depending

upon whichmediumis

being

_utilized,willdictate

bandwidthallocationandinformationtransfer. Mostbusinessnetworkshaveassociated

coststhatprohibit unlimitedspending.Thiscandictate howa specific networkwillbeset

up. Itwillalsodictate bandwidthsize anddatatransfer. Limitedbandwidthswilllimit

signal_strength,which can_potentiallycreatedistortions ornoise. These

distortions,

or

Portal

Devices

Portaldevicessuch as

bridges,

_{routers, gateways,}and repeaters connectlocalarea

networkstogetherand extendthedistancecapabilities ofthenetwork.Eachofthese

components offersdifferent degrees ofdata

handling

capabilities within anetwork.

Bridges aredevicesthatconnect_networks, filterdatapackets, and movethemforwardin

thenetwork. Bridgesoperate withintheData Link LayeroftheOSI Model.

They

can

readthespecific physical addressesofdevicesonthenetworkandfiltertheinformation

before moving itforwardtoanother network segment.Because

they

operate attheData

Link Layer_or,more _{specifically,}attheMAC sub-layer,

they

can clean an

incoming

signal, amplifyitand passitontothenextsegment as a cleansignal

(eliminating

signal

noise). This

filtering

_capabilityallowsbridgestoscan and reducetrafficbetween

segments,generatinga greaterdegree of_security

by

_selectingthespecificdata_signals, or

packets, thatneedtobe sent. Specificapplications of network architecturesrequire

differenttypesofbridges. The

following

are examples ofthesebridges:

Translating

Bridges

-Thesebridges linktosimilarMAClayerprotocols.Incases

where physical _{addressing is}similar,bridgescanbe developedtolinkbetween

MAC layerprotocolsthatare notidentical. Anexampleofthiswouldbe abridge

connectinganEthernetnetworktoaToken

Ring

network.

Learning

Transparent Bridge- Hasthe

capabilitiesto

identify

each network

segmentand creates addresstables thatoriginatefromthatspecific network

LocalBridges

-Thesearebridgesthathavealocalarea networkconnectedon

each side. Ifabridge

links

a network over a widearea,it isreferredtoasaremote

bridge. Eachofthesebridges hasvaryingcapabilities asfaras

transmitting

data

bandwidth. Remote bridges_generallyoperatewithlowerbandwidthcapabilities

thanlocal bridges.

Routerscan provide greater control ofdataflowtoanetworkas

they

becomemore

complex.Routers operate attheNetworklayer oftheOSImodel. Itworks

by

_openingthe

datapacketdeliveredattheMAClayeranddeterminesthe_{routing destination}

by

the

information supplied. Thisadditionalworksupplied

by

therouter requiresmore

processor

time,

_memory,andnetworkconnections.Typicalrouters can support_many

protocols _{simultaneously,}butthiscanleadtoincreaseduse of multiplethird_partyrouters

onthenetwork.

Routerswork

by forwarding

adatapacketto theappropriatenetworkdestination

determined

by

the tableofinformationthatwas created whenthe informationwas

received.Therearetwo typesoftables thatare created

by

_{the router,}static anddynamic.

The statictableisupdated_manuallyasthenetworkismodified whilethedynamictable

updates _{automatically}as routers communicate viatheRIP. Thiscommunicationbecomes

importantas networks continueto

develop

withincreaseddatatransfer speeds.Asrouter

technology

develops,

the_abilitytoanalyzedatatransferonmultiple network paths can

provide added

functionality

fornetworkload

balancing

anddata backups. This

securitycontrols neededtocircumventdata intrusions.

Security

prevention_maybeas

simple as_applyingpasswordprotectionthatrestricts accesstoaparticularnetwork,

workstation, or_server, or_maybeas elaborate as_usingfilterstolimitaccess tospecific

routers subnets.

Gateways operate at alllevelsoftheOSImodel.

They

can providecontent conversions

betweenmultiple environments and applications. Gatewayscontainboth hardwareand

software components and providebothconversionand_{routing duties}andcan supportfull

examination ofdatapackettransfer. Inother_words,

they

canbeusedinsituationsto

connect a networkthatcontainsdifferentplatforms and requiresdatatranslationorother

application support._{Examples may include connecting PC based}workstationstoa

mainframe computerorconnectionofdifferentmailbasedsystemsthatare allowedto

communicatewithone another.Therearedifferenttypesof gateways_that,

depending

uponthesystem_{architecture,} canbeused.

Repeaters amplifytheelectronic signalfromone networksegmenttoanother.

They

are

connectedtosimilar segmentsthat transmitsimilardatasignals. Repeatersoperate atthe

Physical LayeroftheOSI Modeland are notimpacted

by

high-levelprotocollayers.

Fromabasic_{perspective, the}purpose of a repeateristoextendthephysicallengthof a

networksegment. Thisremains oneofthe_primary

benefits,

butthereare potentialissues

such as:

Repeaters don'tfilterout signalnoise, so noiseis amplified and sent withthe

signal. Becausethisproblem_exists,there is_generallyalimitonthenumber of

As signals are generated overlarge

distances,

timedelayscanoccurwhichcan

generatetimeouterrors

-keeping

repeaters from

being

usedforremote links.

Internets

Asmentioned_earlier, DARPA's programhelped introduceand

develop

the

Internet,

as

we are accustomedto today. RFC 760

8,

publishedin

January, 1980,

was one ofthe

earlier specificationsthathelped definetheInternet. Itwasbaseduponfive earlier

versions oftheARPA Internet ProtocolSpecification.This specificationdescribesthe

Internet Protocolas aninterconnectedsystem of packet-switchedcomputer

communications networks.

Essentially,

theInternetisa conglomerate oflocalarea

networks connectedtogether

by

whatis knownas multiple45-622 Mbpsbackbone

circuitsthatare provided

by

afew dozencarriers acrossthecontinentalUnitedStates.

Thissystemis_{considerably larger if}considered(or looked at) froma worldwide

perspective.Therearefourmajor accesspoints inthecontinentalUnitedStates along

withmultipleMetropolitan AreaExchangeswherethesecircuits connect. Fromthese

points arehundredsofother carriersthatinterconnectathundredsof points_alongthese

routes. Eachofthese carriershasredundant connectionstopoints withintheUnited

Statesandpointsaroundtheworld. Asthesecarriers continue_{to expand,}network

Internet Service

Providers

Carriers,

orInternetService

Providers,

usedigital lines such astelephonelines froma localtelephone_companyor cablelines leased from localcable companiestoconnectto thebackbonecircuits. Thisis a convenient and_relatively inexpensive_waytoreachthe

'

end users. Thereare_currentlyother vendorsthatare

laying

milesuponmiles offiber optic_cabling, which at some pointwillreplacethecurrent mediums

being

used. Until

that point,

however,

existing ISP'swill continuetoutilizepresent resourcesuntilthecost differentials forcea change.

ISP's are comprised oftelecommunicationscorporationssuchastelephoneand cable

corporations,and othersthatare specializedintheInternetbusiness.

They

competewith eachothertoprovidetheend usersInternetaccess.

They

providehigh-speedconnections

WebServer

Proxy

Server

POPServer M

Wiring

Hub -*

Router

v

fe

Remote

Access

Router

^

w DNS Server

w

Backup

Server

W

i\

ir

Newsgroup

Server

Primary

access linesto

localtelephone/cable

companies

[image:32.519.46.479.77.332.2]

Authentication Server

Figure 2 - Example_ofHow

Domains

The structure oftheInternet's_{namingconvention,}orLP_addressing,canbecumbersome

tobothremember and use. Businessorganizationshave adoptedtheuse of acronymsto

identify

LPaddresses.Theseacronyms represent a networkdeviceand canbe easierto

rememberthananLPaddress. Forthisconcept_{to work,}aframeworkneedstobe

developedto_mapthesenamesto theirassociatedLP addresses.

Originally,

this

frameworkwas organized

by

theSRI Network Information Center. 9

They

managedthe

specified names inafilecalledHost.txtthatlistedthenames ofthenetworks and

gateways_alongwiththeirassociatedLPaddresses. Thisprocess worked_{adequately in}the

beginning

ofInternetusage,butas itgrew,

being

abletoadministerthisfile becamea

huge

(challenging,

overwhelming

task)

job requiring largeresources.Todealwiththis

problem_adequately,asystemknownastheDNSwasdevised. This system uses a

hierarchicalschemetocontrolthe_namingconventions. Theadvantage ofthissystem is

thatitallowsadministratorsthe_abilitytomanage networkdevices at a specificlevelof

thehierarchy. For

instance,

adomainmighthaveasubdomain as part ofits

tree,

_allowing

Figure3 - Example

of aDNSStructure

Theexamplein Figure 3 is arepresentationof ahierarchicalstructureofaDNSthat_may

existsomewhereintheInternet. TheRoot isthehighest-_{leveldomainlevelofthe tree}

represented

by

ORG (organizationsnot otherwiseidentified

by

other

domains),

MLL

(military

organizations),EDU (educational

institutions),

GOV

(government),

ARPA

(arpanet),

COM (commercial_{enterprises),}andCon (countries_usingtheISOstandard).

Eachoftheserootdomainshave subdomainlevelsofthe treewhich representdifferent

[image:34.519.50.452.40.392.2]

Nameservershavethe_{responsibility}of_controllingspecific zones ormultiple zonesand,

forthemost_{part,containing}theirowndatabasestructure.Nameserversinteractwith

other name servers

by

_sendingqueriesbackandforthvia

TCP,

whichatthemoment

providesthegreatest_reliabilityand efficiency. Thenext subdomainlevelinthe tree

shows

Company

Ewith

Bob, Sam,

and_{Joe representing}specific domainswithinthe

companystructure.This levelofthedomainisthelowestlevelofthedomainstructure

andis knownastheleafnodebecausethereare nodependenciesassociated withthe

domains. The_{DNS naming}convention requires each nametobeuniquewithinthe

specifichierarchical

level,

butcanuse repetitivenamesin different layers. Amajor

advantageoftheDNS systemsisthatitgivestheadministratorthe_abilitytoset

permissions and specific rightstospecificdomainsasneeded. _{The ability}tomanage

these_{domains helps increase security}

by

_settingaccess rights and

locking

downendusers

and

by

_controlling

incoming

and_outgoingnetworktraffic.Otheradvantages ofDNS is its

abilitytosupport mailapplications aswellas_{containing information}aboutlocal

Communication

Architectures

Communicationarchitectures allow a wide range of computer_{makes, models,} and

operatingsystemstocommunicate across a network or_manynetworks.Architecture

standards arebaseduponthe_verysimple requirementthatsystems needto transferdata.

Essentially, they

are manufacturer's conceptsfor_networkingtheirdevicestogether.

Froma simplistic_viewpoint, a communicationnetworkconsists of atleasttwo

communications centers

(computers)

and a mediumtoconnectthem.Thesecomputers

and medium connectionshaveassociatedtasksforwhich

they

areresponsible.For

example,Computer Awillinitiatea commandto thenetwork

indicating

aneedtoopen a

communicationlinktoComputer B. FilemanagementapplicationsonComputer A

ascertainthatComputer B is_readytoaccept adatatransferand needstobepreparedfor

file storage afterit has beenreceived. Once bothsystems agreeontransmissionanddata

integrity,

filetransfer takesplace.This illustratesthat_many steps(or

functions)

needto

takeplaceforasuccessfulexchange ofdata. Theseindividualprocesses canbe

implementedas a single command,or canbe broken down intodifferentcommands and

implemented

independently

fromeach other. In_{this example, these tasks} canbe broken

downintothree_tasks,whichare structured modules. Thesemodulesimplement

communicationsfunctionsand are referredtoas a protocol architecture asdepicted in

ComputerA ComputerB

File Transfer

Applications

^ k.

File Transfer

Applications

File andDataTransfer Commands

Communications

Transport

Communications

Transport

CommunicationExchanges

Network Access Network Access

[image:37.519.57.468.52.202.2]

CommunicationsNetwork

Figure 4 - Protocol Architecture

Thethree-layermodel isorganized as follows:network_{access,transport,}and application.

Theselayersare somewhatindependentwithfeaturesets particulartoeach.

Thenetwork accesslayer focusesontheexchangeofdatabetweenthecomputer and

network. Characteristicsofthislayer_{include providing}networkaddressesand_may

includespecialized services such as priorities.Thetransportlayerverifiesthat thedata

arrives inthesame orderitwas sent.Theapplicationlayercontainsthesoftware needed

tosupport_anyapplicationsinvolved inthe

transfer,

such asfiletransfer. Theselayers

illustrate hownetworktasks canbe brokenapartintoindividual

tasks,

independent from

each other.Theadvantages ofthis typeofdatastructure arethatvendors utilizedifferent

data

formatting

and exchange_{architectures, allowing}communicationfromvendorto

vendor without_creatingspecial purpose softwaretocommunicate. Commonstandards

promotethebenefitsfroma vendor's_{perspective, that}implementationoftheirsoftware

willbe_{widelyaccepted,}andfromtheconsumer's_{perspective, that}

they

will notbe

interconnected. Examples

of vendor architectures include Digital Network Architecture

(DEC),

AdvanceNet

(Hewlett

Packard),

Distributed Systems Architecture

(Honeywell),

Internet Packet

Exchange

(Novell

Netware),

andXerox Network Systems (XNS).

Today's standardizednetwork_{architectures,} or_protocols, such as

TCP/LP,

OSIorSNA

Systems Network

Architecture,

toname a

few,

weredevelopedtopermitallow

manufacturerstoattachcommunicationsdevicesof all makesand modelsto thenetwork

without

having

toredesignthenetwork eachtime. Thesemodels intheir_earlystages,

however,

didnot provide forreliable communications. Therewere noacknowledgments

asdatapacketstraveledfrompoint_{to point;}norwerethere acknowledgementsfromend

toendtransmissions. Therewas no error controlfeature for

data,

_onlyaheader

checksum. IftheICMPdetectedan_error, itwouldberecorded,buttherewere no re

transmissions. Itbecameclear_earlyonthatIPv4was not architected with_securityas a

priority. Itwas_onlyafteritsvulnerabilities were exposedthatmodifications became

neededtoprotecttheenduser. In

September, 1981,

RFC 79110 waspublished and

becamewhatisnowknownasIPv4. This specificationreplacedRFC

760,

which

describestheInternet's basicoperationsas follows:

1. TheInternetprotocolimplementstwobasicfunctions: addressingand

fragmentation.The Internetmodules usethe addresses carriedintheInternet

headertotransmitInternetdatagramstoward theirdestinations. Theselection of a

path fortransmissioniscalled routing. The Internetmodules usefieldsinthe

Internet headertofragmentand reassembleInternetdatagramswhen_{necessary for}

transmissionthrough"smallpacket"

2. Themodel of operationisthatanInternetmodule residesineachhost engagedin

Internetcommunication andineach_gatewaythatinterconnectsnetworks. These

modules share common rulesfor

interpreting

addressfieldsandfor

fragmenting

and_assemblingInternetdatagrams.In_{addition, these}modules

(especially

in

gateways)haveproceduresfor_{making routing decisions}andforotherfunctions.

3. The Internetprotocoltreats eachInternetdatagramas anindependent entity

unrelatedto_anyotherInternetdatagram. Thereare no connectionsorlogical

circuits(virtualorotherwise).

4. The Internet Protocolusesfour

key

mechanismsin providing itsservice: Typeof

Service,

Timeto

Live, Options,

andHeaderChecksum (thesemechanismsare

describedlater).

With Internetspecifications

becoming

_{standardized,virtually}all computervendors

today

supportTCP/LPastheInternetbasedprotocoltobeused. OSIandSNAare other

examples ofimportantarchitecture_supportingcommunications

functions,

butarenotas

predominant

today

as

they

once were. Allprotocol modelshavea_{corresponding}function withinits

layering

structuresimilarto theother models. For_example, TCPoperates atthe

OSIlayer

4,

andLPoperates attheOSI layer 3. Thesecommon protocols allowtasks

fromoneprotocoltocommunicatewith another protocol_seamlesslyto theend user.

Fromthesebasicmodels, otherprotocolshaveevolvedthat_supplyother

functionality

suchas

SMTP,

usedforelectronic_mail,

FTP,

to transfer

files,

and

SNMP,

fornetwork

management activities. Figure 5illustratesahigh-levelcomparisonbetweenarchitecture

Hardware

OSI Layers SNALayers TCP/IP Layers

Application

Layer

Transaction

ServicesLayer

Application

Layer Presentation

Layer

Presentation

Layer

Session Layer Data Flow

Layer

Transport

Layer

Transmission

Control Layer

Transport

Layer

Network Layer Data Path

Layer

Internet

Data Link

Layer

Data Link

Layer Network Layer

[image:40.519.62.412.60.411.2]

Physical Layer Physical Layer Physical Layer OS

OSI Model

The OSImodel was developed

by

theISOas a modelforprotocolarchitecture standards

andforother protocolstouse as a guide for development.Itis made_upofsevenlayers

thatprovidedifferent

functionality

at eachlayer.ThebasicintentoftheOSImodelwas

forother

developing

protocols to

develop

their

functionality

_usingthelayeredconcept,

withthehopethat_proprietaryimplementationsof specific protocolswould_{eventually be}

replaced. _{As many}functionalprotocolshave been developedandhave _consistentlyused

theOSIarchitectural_{model, the}conceptdidnot meetitsanticipatedgrowthand was

insteadreplaced

by

TCP/LP. Thereare a numberofreasonsfor_this,

including

the

complexityoftheseven-layer_approach,butthemostpredominantreasonwas,most

likely,

timing. The TCP/LParchitecturewastestedat a stable point whenbusinessneeded

anarchitecturethatwould addresstheneed of_operatingacrossmultiple networks. OSI

was stillin its developmentstages. Evenso, theOSImodeldid havemerit and was used

extensively.

The OSImodel,as_mentioned, isa seven-layered communications_protocol,

internetworkedtogethertocommon communicationdevices. Thedevelopmentofideas

behindtheOSImodelfollowedafew basicconcepts:

Eachlayerperforms itsownfunction.

Layersshouldbedevelopedwiththeintentoffutureprotocolstandardization.

Boundaries are_clearlyidentifiedbetween layers.

Develop

enoughlayerssothatspecificdatatransferfunctionscanbe

distinct,

and

The OSIlayersare:

Application

-enables accessto the OSIarchitecture structure andprovides

informational servicesfunctionality. Other functionsofthislayer includefile

transfer thatcanhandleservices such as electronic mail and

directory

look-ups.

Presentation

-dealswiththesyntax ofthedatatransmission

by

_performing

repeatabletasks.Anexample mightbea_specified,agreedupon_encodingservice

amongcomputers ondifferentnetworks.Thepresentationlayerverifies and

correctsthe

incoming

and_{outgoing data.}

Session- _{provides a structure}between_systemsthat_{allowconnections}and

terminations.

Transport

-enablesreliabledatatransport

by

_{monitoring data flow}and_providing

error_recovery

by

_makingsurethedataarrives correctly.Data may be divided

amongnetworkstoimprovetransportefficiency.

Network

-responsiblefor controllingtheoperation ofthesubnet

by

_{establishing,}

maintaining, and

terminating

connections

Data Link

-sends data framesofinformationacross thenetwork. Thislayeralso

checks fortransmissionerrors

by

_creating and_{recognizing data}frame

boundaries. The data linklayerwill solveissuesthatoccurifdatais

lost,

damaged,

orduplicated.

Physical

-responsibleforthebasictransmissionofdataoverthenetwork

medium.

Figure6depicts how datatransferoccurs intheOSImodel

by

eachdefinedservice

providingaservicetothelayeraboveit. This hierarchicalapproach allows eachlayerto

Sending

System

1

Receiving

System

t

ApplicationLayer Application Layer

IT

a

Presentation Layer Presentation Layer

V

A

Session Layer Session Layer

1

t

Transport Layer TransportLayer

1

t

Network Layer Network Layer

1

t

Data Link Layer Data Link Layer

1

t

Physical Layer Physical Layer

[image:43.519.69.459.50.465.2]

Data Transmission Path

TCP/IP

TCPpackages and preparesdatafortransfer.LPisresponsiblefor establishingthe

frameworkneededfor_gettingthedatatransferred _successfullyacrossthenetwork. It

allowstheexchange ofinformation between differenttypesof networksthatattachtoan

LPgateway.

Together,

TCP/LPisa protocol suitethatorganizes softwarecommunications

toshare resources across networks. ItistheInternet basedstandard andtheframework

for_manyother communication protocols.Withinthis protocol, data ispassedthrough

multiplelayersoftheprotocol architecturethatare identifiedtoa

device,

_operating

system,or specifictask. Thisprocess has beenstandardized

by

theLAB. WithintheLAB

are committees thatissue RFC'sandSTD's. Theadvantages of

having

acommon

protocol aretoallow computerswithdifferent operatingsystemstocommunicate.This

advantage alsohasadownside

by

_providingpotentialopeningsfor security intrusionsto

takeplace.Theselayers oftheprotocolhave different functions in data handling. The

current model oftheTCP/LPprotocol suite canbe groupedinto fiveseparatelayers.

These layersprovidedifferenttasks thatallowthe transferofdatafromonehostto

another. Theselayers canbe broken downas follows:

Application Layer

-physicalinterface betweenadevicesuch as a computer and

thenetwork.This layer defines_{the transmission medium, type}of signals _used,

rateatwhichdatais

transferred,

and_anyother characteristics associated with

movingtheinformationthrough thenetwork.

Transport Layer

-focusesonthedataexchangebetweenperipherals andthe

InternetLayer

-thesearetheprocedures or_{routing functions}thatallowdatato

betransmittedacross multiple networks.

NetworkAccess Layer- deals

withtheexchange ofdata

(accessing

and_routing)

betweencomputers andthenetworktowhich

they

are attached.

Physical Layer- deals

withthephysicalinterfacesbetweendatasenders and

receivers such as computers andthe transmissionmedium. Theconcerns ofthis

layersurround medium_{characteristics,} signal_{characteristics,}datatransfer rates,

Internet Protocol

LPisa connectionless servicethatpermits networktrafficbetween

hosts,

_usinga32-bit

address schemeto

identify

thehostcomputer and associated network. LPdoes nothave

the_capabilityto

identify

and_replytodatatransmissionerrors. Its designwasmeanttobe

transparent toorindependentof thenetwork.

If,

for_example, adatagramtransmission

passesthrougha router and violates an established aspect such as_{size, the}bufferswill

overflow and removethe_remainingdatagrams.Unlessahigher-levelprotocolsuch as

TCPrecoversthistypeof

information,

datagramscanbe

lost, duplicated,

or arriveinno

specific order.ThedesignofLPallowsfor easyinstallationand provides a robust

protocol,butas

indicated,

no error_recoveryordataflowanalysis.Theseresponsibilities

reside attheTCPlayer.

Whena computeris hooked upto theInternetthroughan

ISP,

an address isassignedthat

identifiesthatparticular computerto theworld.All devicesthatare connectedtoa

networkrequireanLPaddressthatconformstothe_{Internet Protocol naming}convention

Internet Connection

|

^

T

Router kW Hub w

h,

1f

Router ^^ Hub p

^

1 T

Router ^w Hub ^

PC

PC

PC

PC

PC

PC

PC

PC

PC

Printer

Figure7- Example _ofMultiple Devices ConnectedtoaNetwork

Requiring

anLP [image:47.519.110.401.30.507.2]

This namingconvention was devisedtoallow administratorsthe_abilitytocontrol

networks withintheirLANs. Thecurrent_addressingscheme withintheIPv4protocol

uses an address with32-bits. Whentraffic is initiatedthroughthenetwork

by

adevice

such as a_computer,itpasses through the transport

layer,

typically

TPCorUDP. The

addressis broken into_{two parts,}onethatidentifiesthesubnetworkandthe otherthat

identifiesthe node onthesubnet.Thedatatrafficis identified

by

aprotocolLD. Afterthe

receiving devicehasacknowledged_{it is ready}toreceivethedatatraffic, it ispassedto

thenetwork

layer,

whichtakes care ofthenetworkaddresses, orLP addresses. LP

addresses are usedtodeterminewherethe trafficistoberoutedintheInternetand are

identified

by

formatsknownasClasses. There arefourClasses:

A, B, C,

andD(Figure

8). Thefirstportions,or

bits,

oftheaddressindicatenetworkidentificationaddresses and

theremainderofthe classindicatesthenumberofhoststhatcanbeidentified inthe

network. Eachclass signifiesadifferentnetwork_addressingschemesthatwouldbe

ClassA

Network (7

bits)

Host Address (24

bits)

Maximumnumber of network numbers is 126

Maximumnumber ofhostnumbersis

16,

777,124

Nomenclature

-network.host.host.host

ClassB

10 _Network(14

bits)

_{Host Address(16}

bits)

Maximumnumber ofnetwork numbersis 16,384

Maximumnumberofhostnumbersis 65,534

Nomenclature

-network.network.host.host

Class C

110 _Network(21

bits)

_{Host Address (8}

bits)

Maximumnumber of networknumbers is 2,097,152

Maximumnumber ofhostnumbers is 254

Nomenclature

-network.network.network.host

[image:49.519.85.439.48.619.2]

Class D

Depending

upon network_{requirements,} other variations oftheseclassescanbechosen.

These are_specificallygearedtowards Internetusage. Ifa networkisnot_goingtobe

accessingthe

Internet,

thenchoosinga class willdependuponconsiderations such as

ratio of networks tohostmachines andfuturegrowth of

both,

networks andhost

machines.

Thedatasent

by

thehostcomputerthatisroutedthroughanetworkis knownas anLP

datagramorPDU. Thesedataunits canbe

divided,

orfragmented into_smaller, more

manageable units

by

afragmentationprocessthatis supportedintheLPprotocol.This is

neededbecausenodedeviceswouldberequiredtosolve incompatible PDUsizes

between devicesotherwise.Figure9shows howanLP

datagram,

or

PDU,

canbe broken

LPVersion Header Length

TypeofService

Total Length

Identifier

Flags Fragment Offset

TimetoLive

Protocol

HeaderChecksum

Source Address

Destination Address

Optionsand

Padding

Data

Figure9- IPv4 Datagram

IPv4 Datagramfielddescriptions:

LP Version

-identifiestheversionofLPinuse. Thisis containedinmost

protocolswiththecurrentversionat4or_commonlyreferredtoasIPv4. Thenext

generationis identifiedas

6,

orIPv6.

HeaderLength- thisfield

contains4bitsthatindicatethelengthofthe

datagram

header.

[image:51.519.142.395.49.387.2]

some vendorsdonotusetheTOSfieldintheirimplementationsof

LP,

but

increased

capabilities ofthe_{Internet may}promoteincreasedusage.

Total Length

-thisisthe totallengthofthedatagrammeasuredinoctetsand

includesthelengthoftheheaderand associateddata (determined

by

subtracting

theheaderlengthfromthe totallengthofthefield).

Identifier- controlsdatagramfragmentationandrepair_alongwithFlagsand

Fragment Offset. Thisfield identifies fragmentsinadatagram.

Flags

-thisfielddetermineswhetherthedatagramcanbe fragmented.

Fragment Offset

-contains avaluethatspecifies a position of afragmentwithin

theoriginaldatagram.

Time-to-Live

-measures amount oftime adatagram is inthenetwork

by

_addinga

valueto theparameter wheneveradatagrampassesthroughanLPnode suchas a

router.

Protocol

-identifies thenextlayerprotocolthatwill receivethedatagram.

Header Checksum

-detects anyerrors that_{may have}occurredinthe

header,

but

willstillrequire ahigher-levelprotocoltoperformerrorchecksonuserdata if

required.

Source Address

-containstheInternetsource addressinthedatagram.

DestinationAddress

-contains theInternetdestinationaddress inthedatagram.

Options

-notusedinall

datagrams,

butcanbeusedforspecific applications such

asnetwork managementanddiagnostics.

Padding

-ensuresthat thedatagramheaderisaligned correctly.

LPdatagrams

identify

hownetwork_{information is broken}downandevaluatedatits

lowest

level,

butalso hasspecific servicesthatitcanperformfordifferentvendor

products.

Depending

uponthenetwork_{architecture,} someLP services willnotbeutilized.

Wheninformation isreceived at a_router,LPverifiestheheadertodeterminethe type of

networktraffic itwillbeprocessing.

If,

forexample, theinformationisa

datagram,

the

router will passtheinformationontotheheadercheck,whichwillcheckforheader

length,

LPversion_numbers,message

length,

validheader_checksum,andtimeinthe

network

(making

surethisvalueisnot at zero). Iftheinformation isaccepted,itwillbe

passedto thenextLP

device;

iftheinformationisnot_accepted,itwillbe discarded.

LP alsohas differentways itcan routeinformationsuch as:

Sourcerouting,which allowstheupper-layerprotocoltodetermine howthe

routerswilldirectthedatagrams.

Looking

attheaddressesinthesource_routing

fieldtodeterminethenextLP destinationaccomplishesthis. Iftherequired

datagramfieldsindicatethat the_{routing list has beencompleted, then the}

destination LPaddressisused. Ifthe_{routing list has}notbeen_{completed, then the}

pointerincrements LPaddresses

by

oneto thenextaddressintheroute.

Route recordingis another examplewhereLPusesthenext addressinthedata

fieldtodeterminethenext_stepthedatagramwilltake. Thedifference here isthat

the_{receiving LP device}will addits LPaddresstotheroute. Thishappensafterthe

receiving LP devicechecksfield lengthstodetermine ifthe_{recording list is full.}If

themoduleis

full,

itwillforwardthedatagramwithout

inserting

an addressto the

next octetopening,wheretheaddressis insertedandthedatagram ismoved

Time _stampingthedatagramas itpassesthroughLP devicesisanother serviceof

LP. Thisallows for

tracking

thedataroute asitpassesthroughthenetworkand

showstheamount oftime ittakes toprocess data betweeneachLP device. The

Internet Protocol Version 6

The Internethasgrown so_rapidlythatit has forcedchangeinthe_waytheoriginalIPv4

protocol wasdesigned. Fromahistorical_perspective,Arpanetwasdesignedas apacket

switchingnetworkthatcontainedfournodes.Itwas designedat areducedscalebecause

theoriginal concept was for itsusein_research,designandeducationalarenas.As

visibilityoftheInternetgained_momentum, organizations otherthangovernmentand

educationtooknotice.The LETF began

looking

at proposalsthatwoulddefinethesize of

theaddress space requiredfortheconfiguration.Withthe_{understanding}that the Earth's

population would grow_{substantially,} andthebeliefthatanyone who wantstoaccessthe

Internetshouldbeabletodoso, technologicalprogressbecame imminent. After

taking

intoaccountthatusers_will,most

likely,

be accessingmultiple computers (not onlythe

ones on our

desktops,

butthosethatareincorporated intoour_everyday

lives),

itbecame

evidentthatanewversionoftheInternet Protocolwouldbeneededtocomprehendthe

addeddemand.

Essentially,

themajordifference between IPv4 andIPv6 n falls intothe

following

areas:

1. Expanded

Addressing

Capabilities: IPv6 increasestheLPaddress size from32

bitsto 128

bits,

tosupport morelevelsof_addressing

hierarchy,

a much greater

numberof addressable_nodes,and simpler auto-configuration of addresses. The

scalabilityof multicast_routingis improved

by

_addinga"scope"fieldtomulticast

addresses.Anda newtypeof address called an"anycastaddress"

is

defined,

used

2. HeaderFormatSimplification: SomeIPv4headerfieldshave been droppedor

made_optional,toreducethecommon-case_processingcost of packet

handling

and

tolimitthebandwidthcost oftheIPv6header.

3. Improved Supportfor Extensions andOptions: Changes inthe_{way LP header}

options are encoded allowsformore efficient

forwarding,

lessstringentlimits on

thelengthof_options,and greater

flexibility

for

introducing

new options inthe

future.

4. Flow

Labeling

Capability: Anew_{capability is}addedtoenablethe

labeling

of

packets

belonging

toparticulartraffic "flows"forwhichthesenderrequests

special

handling,

such as non-default_qualityofservice or "real-time"service.

5. Authenticationand

Privacy

Capabilities: Extensionstosupport_{authentication,}

data

integrity,

and

(optional)

data confidentialityarespecifiedfor IPv6.

Initialconceptsofthedesign began in

1991,

and

by

1995fourRFC's (Figure

10)

were

introduced. These RFC's

(1883-1886)

12weretobecomethenew version ofthe

Internet,

classifiedas

IPv6,

andwillincorporatenewfeatures thatcomprehendincreasedusage

andeliminate specific problemsthathaveevolvedin IPv4. Ipv6will address specific

issuessuchasaddress _space,inefficientoperations,and network architecturetechniques

that incorporategreater

functionality

andimprovedsecurity.

Many

ofthecharacteristics

oftheIPv4protocolwillberetainedforthe time

being,

because oftheir

dependencies

on

other related protocolsthathave been developed_extensivelytosupport_existing

transmissions suchas_video,

data,

and voice.

Considering

thatIPv4uses32-bitaddress

spaces, thenewconfigurationwould allowforsignificantexpansiontosupportthe

numerical_value,thereare_manypossible addressesthatcouldbeused,but partitioningof

thisaddress spaceinto similarIPv4classes

(A, B, C,

D)

has increasedspace

limitations,

especiallyintheclassC space whichhasthehighestnumber of networks associated with

it. Itspossibleto_{increase subnetting}more classes intoclass

C,

butthatwas not a viable

optionfortheLETFboard becauseclass networkshave fixed boundariesbetween

identificationof network and nodes.Whena network numberis assigned,allthehost

addressesforthatnetwork are assignedto thatnetwork.Forexample,ifa networkneeded

500_addresses, itwould notbeabletouse class Caddressesbecause itcontains_{only 25}