dec :: dtj :: dtj v09-02 1997

75 Pages·1997·7.3 MB·English

Editorial Tl1De( �ilTuclc l:ntiwljouranr eaflreieesd Thet dloi1111 .�t rter .tdem;o�Dfri kg.ist al
J�neC. Blaket'v,b na�inEgd itor journaplu blsihedq uarterly bvD igitla EquipmentC orpor.ui:\olnp:h .1SerHT.
HeleLn. P attersFodni,r or EquipmentC orpor,nion5,0 N agoPgar k, AlpluSwioAnlt,aV isat,D ECneDri,l ;rr.\L.,
Karhlc·tn M.S rersoEnd,ir or AK02-3/B3A,ct on,M A0 1720-9843. rhcD IGITALl ogoD, IIGTALC :S:JX.a nd
OpenV MS
H.1dr-copvs ubscriptionsc anb eo rdered lw
Circulation sending o checki nU .S.fu nd(sm adepa vable BSME isa t r.1ckmo.fuR-.'ikA1 ),1[,1 SIencc1.1 rill,
PCartohdeurcitMni.eoP nh illAidpmsi,n isrr�ror prrou aDbtli,esigh\seir5d re-4Ebo 0qvlu. i0a(pm0dne donrnteCG-s oeUrsnp$..oer6Sa rla0.ts f) iou not)brro s ouricr hs resi uepst cCoicoworMnpn.oer1d siai iusbatlson ri d.ria .r�l· odctLmo'o;l Hn·kD,1 c·sYcc l:oIMnpmca.c,ian lr w, h ol.l ,·
ChristJacs sviVPcro.o, d uctiEodni tor and5 75.0(n0o n-U.S.S !!5to)re ighit" uo.
ElizabMectChr aiTlv,p ogr•1phcr Universaindtc Yol elgep rotesasnodrP sh .D. CRYPTOCardi s,re\g istered rradenuorfk
Pc[(;rR .W oodburvI,l lustrator srudcimnst hee lecoiencgoinle eirng andc om­ CRYPTOC.udC orp<;ration.
puresrc ientecildes r eceicvoer nplimcnsruabr­v IBMi s. r1e gistered trademaorfIk n ternational
AdvisoBroy ard scriptoinsu ponre gucsr.D IGITcALus tomers Busine1s\s' i�cChiornpeor.;rs1io n.
SamueHl .h illeCrh,a irn1an allgleq<droul colo lnittafocr\girt ' ii:h se ubiascrcrc piotiuonrnset< p Urlaedrs eeen ncroautir,­·eIsn.t ;elln Pden tium :\rrcc" e ,i�trcrracdde nurk-.
SconE.C urler ofI nr eCi: ororparion.
Thon1JFs G annon Elcetronics ubscrpitoinsa rea vailaabrl e
DonaZl.dH a rbert noc hargeb ya ccessing URL i\'laciins.t r1oq.!, :is\t�h:r .:cd rradcm;olfAr'pk p le
Rich)a.r odlHinl�wsorrh hnp://www.digital.com/info/subCsocmrpiuptetr,iI onnc.
)amesE .K uenzel Thisse rviwcies lenld ane lectmraioln ic Micro\s\o'li:i,n Wdiondwowss,9 5,c md
WilliaAm.L ling nori�icniwohne nJ ne\v issuiesa vailable WindowNsT .1nn::e. istcrdc trJ<.kmJrks
Richafrl.d. ; 1ry on tnhreer nIer . oflv1it.:niCS(_())rflp ();.ltic)Jl.
AlanG . t'\cmcrh Singcloep ieasn db acki ssuceasnb eo rdered QuickSwiticsh n a.: !-'-i�rlr'-.".HI.TktmlJr k
RoberMt. S upnik bys enditnhge re questedi ssuev'osl umaen d ofQ uali.Steym i(ondw.ro.:r, f1K.
numbearn da c heck fo$r1 6,0(0n on-U.S.
R.Hnbuisso t rademarko fltunbu, Inc.
Sl8)e acrho r hep ublisheda-dbdyr esRse.c ent
issuatres a lsaov oaiblloen thlen r.eranrc r Sccur<:Kt'\eeyir s. 1rr l.dem.lrk ofDigir.1l
http://www.digital.com/info/dPtja.r hwavIsn,c .
DIG !TALe mployeesm avo rdesru bscrip­ SccuriiDsa r cgistntrc:dH knurk ofSe curity
tionst hrough ReaderCsho icea tU RL DynamiLTse chnologIinecs ,
hrtp://wcbrc.das.odrbe yce .ntceroinmg S/Kcvi s;re\g i,stcredt rademaortk' Bcll
VTX PROF!L E• Ht heO penVM5s ystem CommunicatiRo.ncss c.l1nrcc.h ,
prompr.
SPECi sar egistered rr.tderno;tl'frkShr aen d;ml
Inquiries,a ddrecshsa ngeasn,d c ompl­i
nu:nts.uHbys criorpdetrsic oannb es ent l\:.:rfOnEnv;.l1nlcucaC toiroponr.1 rion.
ror hcD igil'{a(l> cbnica!juurrnhael ar UNIXi s. r1c gisrerrrnald enuirnrk h el 1nictd
published-bva ddreosrsr heel ectronic St:.tltnocdr sh c:Cr< HIIHrliif.'"nu�.:s, e t.d. ·.xdu·s i\·t.·lv
maial ddresdst,j @digitalI.ncquoirmi.se rhroush X/Open CompI,. rudn-.
cana lsboe m adeb vc �llitnhge journal WJtcWho rdi s. 1r egisterrre.dl <klolfRl a<clJfkI
oFfcei ar9 78-264-7549. Dar,a·om Lrd.
Commentosn r hec onreontr' anv paper nad
requetssro conracrou rhoarrs\c 'c\ lcomed
andrn .1bye s cnrro r hem anaginge ditor. H
rhcp ubJisbcdo-rel llet\roc'n icm aiald rdess.
Co:p,Tgihr© 1997D igitalE quipment
Corpor;iHon.C op,·ing withoufte ies p cr­
rnirrpcrdo vidtehdas ru ccohpi esa rc made
t<uns ei ne ducationali nsrirubrvi! oancsu itY
memberasn d uen ordi stirbuted focro m­
mercial. ldV<llAHb<srrlagctein.s wircrhe dit
ofD igirEaqlu ipmenCto rporatiaount'hso r­
ship isp ermirred.
Thei nformi:�nrrh iejoonu ma/siusb ject
toc h,1n\g\c 'intohtoiacunerd s h ould nor
bec onstrueda sa c ommirrncbnyDr i gital
EquipmenCorr porationo rb vt heco mpan­
iehse reni represenDtiegtdali. E quipment
CoveDre sign Corpro.ltinn assumneos r esponsibfiolri ty
Tunndina�n dti rt:walba rct wod h:crive :1neyr rotrhs amary a ppeairnt hej ournal.
rcchnolotg(ie>rt n:ssu risnecgu re commu­
ISSN0 898-901X
nicnionbse tweernh cp ubliIcnt erneatn d
privant<e: tworOkusr.c ovedte·p icetnsc ap­ DocumentatNiuomnb erE C-P8429-18
sulataendd c rpytograipchayl. ,lcucrcdda ra Bookp roductionw asd oneb yQ uant.ic
as" unreadabnluemb"e rsr r:wcliinn< g1 Communicati1onn cs.,
protectriuvnen euln triela chingr heti rcwall.
The tirewf;u1lnlc tiaosn;ss\ cr eenr har
permiotnsl ayu thoriczLtn:tado p �sisn to
rhep r,i·aren etworwkh t:rpc.1·c ko<f:dtast 1
canb td:t :crypwticrdha k eyr h.inss hared
between thes endearn dr hrce ceiver.
DIGITALi mplcmcnraroifao rnusn nel
and� tirewallar c repsented inr hiiss sue.
Thec ovedre siginsb yi .tKinOd'aN eill
ofrhDcI GITALln dusrir.ll< ln(d3 raphic
DesigGnr oup.
Contents
Foerword PauJlC. o rmier 3
ALTAVITSA INTERNESTE CUIRTYA NDM AIL
TheA ltaVtiaTs unnelU:s intgh eI nternet KenneFt.AJhd ena ndE dwarPd.W obber 5
toE xtend CorpNoertawtorek s
Protteicnag P rivaNtetew orkT:h eA ltaViFsiteraw all JM.a rSkm itSchan,G .D oheyrO,tl ivJeL.er a hy, 17
andD ermoMt.T ynna
DevelpoinIgn terSnoeftt warAel:t aVtiaMs ail NicSkh ipman 33
ALPHA-BASWEODR KSTATIONFSO RN TA NDU NIX
DIGIATLP ersonWaolr ksttaionTsh:eD esigonf KentnheM .W eisasn dK ennetAh.H ouse 45
Hihg-performea,nL cow-coAsltp hSay stems
Desigonft he2 1174 MemoryC ontorllfeorr ReinhCa.Sr cdh umann 57
DIGTIALP ersonWaolr ktsations
FurtheRre adings 71
DtgttTaclc hnijco:udrn al Vol9. No.2 1997
Editor's
Introduction
DIGITALh asp ioneemraendy n e­t theeixrp erieinncd eesp loytihneg Housedi scutshsep rimarreya sofn(sx
workindgev elopmei.nn itts4s 0 -yearA ltaViTsutnan ewli thDinI GTIAL. initiJatw ihnogl nlye wd esigsni:m ul­
histoAr rye.c ednetv elmoepntA,l tVai sta, Onced ataar rives-almoisrts- atta neoursolt ya kaed vantagnee wo,f
hasc tpturtehdep opuliamra ginatidoens,t inatthieofi nr,e wailsalfi lteringh igh-performmeamnocreyt echnolo­
ase videnbcyewd o rldwide accersosuetste,hr a dte termiwnheisc dba ta gieasn dr oi mplemeantat l owc osr.
averaging 18mi llipoenrd ayt,ot h is packersw ilble a llowteodp asfrso m A newl,o w-coscto rleo gidces ign
Internseeta recnhgi ne.I ntroduicned r hcp ublict ot hep rivantcer vvork. wasn eederdof imctiaosrn h eC PU­
1995A,l taViisntdae xionftg h ee ntirelv !JrSkm ithS,c anD ohertOyl,l ie to-memoryi nterTfahecr ees.u lt,
Inter\nVeatms a dep ossibbyl6 e4 -birL eahya, ndO crT ynacno mpartey pes describbyeR de inhaSrcdh umann,
VLM Alphtae chnolTohgeyi .n dex offi rewaldlse;s crfiibre ewfaulnlc tionsw :ttsl 12e1 147 s ingle-ccohrileop g ic
proceetdosd aayta p acoef m oret han �ucahs a larsmy steamust,J 1cnticatiAoSnI,C f( )trh eA lphmai croprocessor.
6 millipoang epse rd ayD.I GIATL's andr eportianngd;p resentd etsJi1gcn Designweerrsea blteo m eett l1eir
Internet develohpomweenvtesr,, ofcheAiraFViirsetwata olDrl I GITAL owna ggrespseirvfeo rmagnoc:Ielb sv
gow elble yonsde arfcuhn ctions. UNIX.T heA ltaViFsitrae wcaolml­ f(xusionnrg e ductiiontn hsem ain
Businuessesrn se egdr eaitmJpyr oved prisbeost ha pplication-levelm eamnodr yl atentchyaw ta sa ttributable
securaintdyp r otecttioio nnt egratep �Kket-filftuenrcitnigo naanldi ty ro rhc memoryc ontroslulbesry stem
thep oweorf lntercnoentn ectivitiym plemetnhteps1 inci"ptlhcaw th ich andb yu sinagsm ucho ft her aw
inttoh ebiurs inesIstie sts h.i nse ed isn ote xprespselrym ititsde edn ied."b andwidotfth h eA lph2a1 164
thaitsa ddresisnet dl 1pea peorns Thed evelopmoefnt th eA ltVai sta CPU'sd atbau sa sp ossible.
tunneflisr,e waalnldes l,e ctrmoaniilc. Maiplr oduicspt r esenbtyeN di ck Subjetcotprsa peirnst hen ext
Additiopnaaplei rnst hies sfueea tureS hipmaansa c asset udiynt hei ssuesi ssoufer h.e fmoauli nIcu det he
high-perforlmoawn-cceo,s t Alphbae inegn ginewehrosd esipgrno ductpsa r:dSlCeSIlt echnolosghya,r ed
microprocebsassoewrdo- rkstationts( bJurs inuessesro sft heI nternet. desktsoopft waraen,da h igh­
wituhn iqudee sifgena tusruechs , He relasteevse oraftl h efu ndamentalp erformadnecbeu gger.
asa s ingle-ccohrilepo gAicS IC. assumptiaobnosue tn gineeprrion­g
"Tunnealn"d" firewaallr"se t rong jectthsa wte reo verturbnyet dh e
metaphorsr hadre vleopeurss et o engineertienagmt ;o re xample,
connotreh ek inodf s ecursiotftyw are produdcetf inihtiaodnc onvetinonally
necesstaorp ryor ecrb usinceosms­ starwtietJdtJ1 1 ct cclmiciaslsu teobs e
munications rraonvsetmrhi er teda ddresasneddn ows trared instead
InterneTtu.n nelipnrgo tedcattsa 11�atp lr1o dupcw-tc basep ri.c. eh t1retrl, JanCe. B lake
asi rt ravienlt sh ep ublIinct ernet ina ne ftorrore nsurper oduscitm ­ McmuMilFldJ:ti tor
byp rovidsiencgu ernec apsulatiopnl ictiottryh et argceuts tomtehre,y
withtihnes tandaTrCdP/ IPp roto­ imposetdh ep rinciopfsl iem plicity
colH.o wevears,K enA ldeann dT ed throughtolu1pter oject-simplicity
Wobbeerx plaaidnd,i tisoneaclu riitnyp r esentaitndi eosni,g innm, e th­
measuraersnc e cess,sa preycificalloyd,s :,: midni mplementation.
cryptograpsheiccuaerlnelc ya psulateAd low-cohsitg,h -performance
packeTrhse.a uthodress crhiobwe workstahtaisob ne end esignbeyd
secunreet work-rloeuvteilcn agn DIGITAL'wso rkstaetinogni neering
bea chievbeycd o mbinitnJg1w ee ll­ groupI.nt hefi rsotft wo papers
knownt echnoloogfti uensn elainndg aboutth eD IGITAPLe rsonal
secucrhea nneTlhse.p apeirn cludes\I VorkstaKrieonWn esi,sa sn dK enny
2 Di1,'.Tietc;hlnlJi ocuarln al Vol9. N o.2 1997
Foreword
Thep roducptrse senitnet dh is maturTeh.e sfea ctoqurisc kly led
issaurege o ode xamploefths e r esuJtst ot heD IGITALA ltaViFsitrae wall
thacta nb ea chieviened x tremely product.
shorpte rioodfts i me-stioxn ine DIGITALr espondteotd h imsa r­
months-whreens earpcrho,d uct ketd emanqdu ickilnyi,t imaolvliyn g
developmaenndts ,e rvigcreosu ps theS EALt echnoltooga sy t andalone
workt ogethteobr r inwgo rld-claspsr oduocntD IGITALU NIXp lat­
producttoms a rket. formTsh.e s amee ngineergirnogu p
Int hec asoeft heF irewparlold uctt,h adte veloptehdeS EALt echnology
researrocohtk h el eaeda rlwyh,i le totrJ 1See rvigcreosu spe amlessly
PauJlC. o rmier
theI nterwnaests tiulsle d almost movedt op roduecntg ineerfiinrgs,t
DirectorofEAnlgtiaVniesetra inl!,,
exclusibvyte hlesy c ientainfidtc e ch­int heI nternBeut sinGersos upa nd
niccaolm muniAst yo.n eo ft hefi rst latteort heA ltVai stGar oupT.h is
Fortu5ne0 c0o mpaniteocs o nnect smooth troafne sxfpeerr iea.Jln ocwee d
Int hiiss suwee,f ocuosnI nternet tot heI nternDeItG,I TAL quickly DIGITALto g ot om arkeatft ear
software prtohdaautrc cpt asr otf t he sawt het hretaott hes ecuroifti yt s shorsti,x -modmehv elopmceynctl e
AltVai stp:�o rtfoTlhieos.pe :� rticulanre twoarnkd i,n r esponmseem,b ers andt ob eo neo ft hef irvsetn dotros
producatrsnc otabbleec auosfet he ofi trse seagrrcohu dpe veloptehde oftaes rt .andalcoonmem,e rcfiirJeI­
fashiionwn h ich they have bieneint ial tfeicrhenwoallAolsg w yi.t h wJIpIr oduct.
develoapendd brougmhatr kteot . manyi nnov:�t.tihoinss ,t echnologyE ngineerhians.g l earnteid· om
Witht hec ommercIinatle rnseotf­ r wasr ecognibzyeD dI GITALc'uss ­ reseaarncdhc arritehdak tn owledge
w:�rien dusmtorvyi nqgu ickfrloym tomerasss ratc-ot:atnhdew -aasir nt :�nde xperietnhcreo usgehr vi:cmeds
nonexistteOnt cheem ostc ompetititvuer dne mandebdyt l1efmo r tohweni r directtotJ hye p roduecntg ineering
andf ast-moivnidnugs itnre yx istencues,e Wsh.i lteh icso mpletxec hnologcyo mmunitMyo.r eoveern,g ineering
enginehearvsre e cognitzheend e ed wass tiiUni tisn fanDcIyG,I TAL hasa daptietdps r ocetsoss r ::�cyo m­
foirn novataitao lnsl t agoefsp roductS erviwcaessa blreo d elivheirg h-endp etitwiivteh tihne I ntermnaertk et,
likT.o s ucceiendI ntersnoefttw are,s ecursiotlyu titoocn osm panitehsa t enabliDnIgG ITALt ob ea t echnol­
enginemeursstb ei nnovatboortsh desirteocd o nnetcott heI nternet. ogyl eadweirt tlh1eA ltVai stFai rewall
int echnolaongdiy n p rodudcetv el­ Nots urprisitnhgelscyeo, m paniesp roduocntD IGITAL UNIXa nd,
opmentI.n novatbieogni nwsi th alsnoe edetdoa ddretshses amen et­ morer ecenotnlt yh,e\ VindoNwTs
thceo nceptc oanntdi ntuherso ugh works ecuriistsyut ehsa DtI GITAL platform.
produdcetv elopmaenndto nto raceadsa c onsequeonfccoel lJlectiTnhge A ltaVirsutnan eolrs, e cure
delivteort yh ee ndu searn;d t he tot hep ubliincti- Jstructure. S't�arrttpuiranilgv n aettew oprrko duct (VPN),
cvcle continues. witthh ef irewtaelclh nolyto,hg e hass imirloaro ttsot hosoeft hef ire­
Fromt heb eginniofnt gh eIn ternetS EALF irewSaelrlv iwcaesb orn,a nd waltle chnolTougnyn.e liwnagsb orn
revolutDiIoGnI,T ALh :�sb eena DIGITAL becoanmeoe f t hev erfiyr st inr espontsoae n eefd ovri sitaotr s
significanti nIp nltaeyrneserot m vare Intersneectu rsiotmyv arper ovidersD.I GITALf aciltiots ieecsu rterlay­
ands olutidoenvse lopmeTnhte . Asm orea ndm oree netrprises versteh et rustiendt ernnaelt work
companys'usc ceissas t tributablceo nnectetdh eIt not ernaentd wituh ntrupsatckeedAtg sa.i tnh,e
to the manya dnidtv eecrhsnei callevx perietnhcees da mes eciutriys sues reseacrocmhm unirtoyo tkh el ead.
t::liengtrcodu ptsh aatr ef (JCusing DIGITALh adb eefna cinigtb,e came Witht het llllJleicionngc ept
theriers ourocned se velopsionftg­ evidetnhtab to thfi rewatlelc hnologrye verstehdai,ts a,c ceaslsl owferdo m
waraen ds olutionIsn tfeorrun seetr s.a ndt hem arkewte rbee ginnitnog theu ntrusetxetde rnnaelt \v(otrhke
DigiTteaclh njiocuarnl, ll Vol9. N u.2 1997 3
Inetrnetto)t het rustceodr porate wayt os olvDeI GITAL'mso bile­ Ash asb eenp rovewni tthh ese
netwoarnkd w itehn cryptaidodne d, workeprr oblem. productthsem, o detlh aitsg oodf or
ther udimentbaarsyti ostr o day's DIGITALS ervihcaesas l sboe gun thec ompanayn dt (t)hrec ustomer
produwcats p utf orward. too fkr1h er unnperlo duccto,u pled iso net haitn cludes
Then ewltyo nneIdn terneentg i­ ll'iintth( mnatsieornv ipcielso't • Researcihnecrbusa ting and
neerignrgo uwpa sr eadtyot akteh e experienacsae s so,l uctiooi ntc su s­ pilottihnetg e chnoliong y
technologya ndp rototfyoprel l'ardt,o mers-tshaem em odeuls ewdi th thel abs
putciinngta oc tiaon ne wi nstaonfc e thei nittiiarle ltle'cahlnlo logy. • Engineergirnogu pts"< lpipdrlov­
ther esearch-engipnaeretrnienrgs hiAps.D IGITALa ndt hei ndustrv totypianngdd eveloppirnogd uct
Asw ast hec aswei tthh ef irewaat lall,­ movef ·()riwnau rsdi ntgh eI nternet • Servigcreosu pdse velopai ng
enteedn gineegrrionugmp o vedt he JSa ne fkctbiuvsei nteososls ,t andards repeatasbolleu ttioocrnu stomers
initpiraodlu ctto m arket within asrcie xme rgitnhga DtI GITALi sh elp­ DIGITALwi lclo ntintuome o ve
monrbDsI.G ITALw aso ncaeg ain ingt od efinFeu.t urper oducatrsc technolorgaipeisdt liy- orme search
ablteo l eaidnt heI nternsept acaen d beindgc 1·dopbeads eodn t hes tan­ through producatnsdo nt os olutions,
dajm tfihresV tP N produtcots urfacdea rdasn di nclufdeea n1trheasat l lo11t·h uasc celerarthieun sgeo ftbe
int l1mea rkeotn,e t hactu rrenhtalsy othecro mpani"'ehso,m ayh avvee rv Internaesat m ainsrrebauns1i ness
manyc ompecirors. differseenctu rsittrva te:lgllidpe osl i­tooaln dh elpibnugs inestsaekse
As wasa lstoh ec aswei tthh efi re­ cietso,t akaed vantoafgt eh eI nterneatd vantaogfte h eI nterneatn db e
walDlI,G ITALr ecogniazg eodo d ina s ecuarned p roductive mannceorm.p etitiintv hee iorw nm arkets.
useo ft hitsech nology tos olve oofn e Them odeolf r esearch, product
itosw np robleTmhse.t elecommlldleu­velopmaenndts ,e rviIcIe'sO rking
caciocnoss otfsm ovindg1 eU .S-.b asedt ogetthoed re liivnenro vatciuvnej,n g­
salfeosr cteoh omeo ffiacnedsc on­ edgep roducatnsds olutitohnausts e
nectiintbg a cikn ot thec orpornaette­ theu biquiotfty h eI nterton esto lve
work were becoming excerscsailv-el.lc 'uToshrtelo dmp erro blewmisl l
information osregravniiczearsta ino nc ontintuoee x panDdI GITAL's
ap ilwoitt 2h, 00s0a lpeeso plues,i ng Internceatp abilaintdoi feksr ings.
locIanlt ercnoentn ectiaonndts h e A cornerstoofnt eh er esearch­
Intertnuentn teola uthentiucsaetres product-developmenmto-dseelr vices
tot heD IGITALc orpornaettew ork.i st het :-�leanntdm ind-soeftt h ep rod­
Thes olutwiaosnp erfebcetc autshee ucte ngineegrrionugpT .h ea dvan­
tunnseulp pltiheees n cvrpticoanp a­ tagoef k eepiinntga ctth ceo roef t he
bilitthyae tn surtehsep rivaocfcy o n­ Internaentd A ltaViesntgai neering
fidenbtuisailn deastsaa si tt raversesg rouptsh routghhee ntirtee chno­
thep ublniect worinkt i·astructulroeg.i ccyacltl hea Itp resehnetr hea s
Ther esuolfttsh pei lwoetr set ag­ enabltehdee ngineteorr se acqtu ickly
geriinngt ermosft hes avinigns toc hanging requiarnedmm aernktse t
telecommu1uccaotsiatonsnd ks e ep­ conditjTohnegs r.o uhpa sc onsistently
ingo uri nternneatlw osrekc ure. respondleld' t\i\'t0h m ajoprr oduct
Witht hipsi lionth andi,n formaciorne leapseerys e aarn ds omem inor
servimcoevse dt oo fttehret unnelinrge leanseeesd etdos atiJs pf)a•r ticular,
servitcooe t heirn tergnraolu passa signifdiecmaanntd .
4 DigiTteaclh njiocuarnla l Vol9. No.2 1997
I
KennetFh.Al den
EdwarP.dW obber
TheA ltaViTsutnan el:
Usintgh eI ntertnoe t
ExtenCdo rporate
Networks
Thep ubliIcn ternheatsb ecomea low-cost Thep ublIinct erniestf asbte cominaug b iquitaonuds
connectimoend iumf orj oinirnegm oteem ploy­ inexpensmievdieu mt <xc onnectrienmgo teem ploy­
eeso ro fficetsoa privaitnet raonerft ( xp ermitting
eeso ro fficteosa privaitnet ranaentd f orp er­
impromptu high-speed bceotnwneeebcnut siionness s
mittiinmgp rompthui gh-speceodn nections
partneTrhsi.gs a iinn c onnectiivsoi ftfysb eyta s ignifi­
betweebnu sinepsasr tneTrhsi.cs o nnectivity
canlto sisn s ecurihtoyw,e veTrh.e I nternisen to tori­
iso ffsebtya signifilcoasnistn s ecuriTthye. oust oerl ectrborneiack -ainndes a vesdropping.
AltaViTsutnan ela, D IGITApLro ducotf,f ers TheA ltaViTsutnan eal ,D IGITALp roducott,k rs
securnee twork-lervoeult ionvge rI nternet network-lraoyuetri onvge rs ecurIen ternceotn nec­
tionTsh.i asl lwos,t oerx amplaem ,o bilues etro c on­
connectiboync so mbinitnwgo w ell-known
necste curteolh yi osr h erc orpornaettew ourski ntgh e
networkitnegc hnologtiuensn:e lianngds ecure
Internet. Sai mciolraporrlaynt,ee t worcka ne mploy
channelTsh.ip sa pedri scustsheesd esigann d
theA ltaViTsutnan etlo s ecurelliynr ke motoef fices
implementatoifto hne A ltaViTsutnan ela nd witIhn ternceotn nectiAolntsh.o uoguhr p roduucste s
descriobuerse xperieinncd ee ployitnhge theI nterneftop ra ckettr anspaolrttlr, a fifisec n capsu­
producwti thiDnI GITAL. latewdi thicnry ptographisceaclulryce odn nections.
Becausteh eA ltaVisTtuan neli sa nct\vork-laycr
routecrl,i eanptp licatciaonrn usn w ithoumto difica­
tionM.o reoveoru,r p roducitsfi rewailnld ependent
andt herdocraenb eu sedi nc oncewritt mho stc om­
mon firewalTlhse.A ltaViTsutnan eslu pporbtost h
statciocn nectitoorn se motoeH iceasn di ntermittent
connectitoosn isn gle-user mCaucrhriennetislm.yp ,l e­
mentatioenxsi sfto rt heU NIX,W indows9 5a,n d
WindowNsT platforms.
Int hipsa pewre,b egi\nV iatno bv ervioeftw h eb en­
efitasn dp ittaplrless entbeydu sintgh eI nternteotr
privanteet \vocrokn nectiNveixttyw,.e descritbhee
desigonft hen et\vork proutsoecbdoy lt heA ltVai sta
Tunnewli,t ahp artictuolcauorsn t hes ecurciotnyc erns
thaJte dto t hidse sign.t hWeedn i scuhsosw w ei mple­
menteodu rd esigFni.n alwley b,r iefd1eys criobuer
experiedlelpcleo ytihnegt unneprlo duicnta h u·gceo r­
porantee tworpkr,o vipdeer formadnacteaa ,n dd iscuss
someo ft hes ecurriirys rkhsi tse chnoleongtya ils.
Overview
Beforreh eIn tcrnebte campee rvsaivceo,r poranteet ­
workwse reb uiltti -olme aseadn dd ial-in telephone
lineSsu.c hn etworckasr riseubd s rantcioasltf so bro th
communicatieoqnusi pmeanntd t elephosneer vice.
Usuallsye,c urity orne tlhieei dn accessiobfir lhiet y
physimceadli uma,n do vetrh ey eartsh,er isokfw iretap
hasp rovetdo b es ligwhhte nc omparetod p assword
DigiTtcadl11 1Jiocuarnl al Vol9. No.2 1997 5
T
crackionrgo thehri gher-l�elvtelt ahec rke.a sofno r intermedinaotdee ( "ma-nin-th-emiddlew"i)l nlo t
thiisst h�lamto stt elephosnyes teamrsbe o thp roprietariyn rentiorne�a1od1r lm yo di'tn hed atpao rtioonfts u n­
andc emrlylm anageda,n dt heayr et bcrdonroet e asy nelepdJ ckctTso. p revesnutc hu nwantetda mpering,
tos ubveirntt heb rgew ithoaus tu bst�lbnutdig:edt . we cryptographically secure encfaoprs ulated packers
TheI nternet borpipnogrst unJ.intdyc hallentgoe passJgoev ert hep ublince t\\'OArbks.t ractly, data
them odern corporate dneestiwgonrGeklr o.b :1clo n­ passeodv ert hisse curceh annealp pearosn ceJ nd
nectivmiatkye si tp ossibtlore e plaecxep ensilveea sed onlvo ncea tt her ccei,as·s eern tb y thes ender.
lineasn dc ommunicatieoqnusi pmenwti thI nternet furthermoarne a,t tackoebrs ervitnhgep ublniect ­
connectioHnosw.e vers,u chc onnectioLnKsk the workc annorte adt hicsb taT.h ustu,n neeln capsula­
physicsaelcr utiyo ft elepholnien eFsu.r thermore,t ione nsurtehsa ptr ivate-nedtawrorakg raumnsn ot
direccto nnectitoont he Internpeots ensu merous, interwaicttht l1rCo utianlgg oritohfmths e p ublinect ­
well-documensteecdu riptryo blemCs.o nscquent\l\'vO,wr hke,r easse curceh annels guatrhaanttth eete u n­
manoyr ganizatfiinodni stn ecessatroiy s olatthee ir neledda t�l airnrtiJ,flc··tco ma na uthenticsaotuerdc e
privanteet workbse hinfidr ewalls-filrtocurtienrgs andt haptr ivaicsmy a intained.
thatp lacceo nstrJionnt psa cketJsl lo\\r·oep da ss figurLed epicats se curruen neilno perJtiNoond.e s
betweepnr otectaenddp ublince tworkTsh.e p oliyc A andR ::ti"Ct unneeln dpointthsa,it s p,a ckerto uters
decisimoandse i nc onfigurfiinrge waalllwsa vism ·olve thafto rw�1rtdo� 1nfdr omta unnelreodu teNso.d eA
ad iffictulrta de-boetfwfe esne cuirrayn df unctionalitpvr.o cesdsaetsa graimnsp r ivten etworXka ndd eter­
Cryptogmraakpeihtspy o ssibtloee m ulatmeo sto f minewsh ichi,fa nys,h oulbde r outetdo p rivanteet ­
thep ropertoifpe hsy sicaslelcyu rwei rues inIgn ternet workY .No deA theenn c:1psulaaltslcu sc hd atagrams
coennectiWohnesn.e nc1psulaatta e sdu itapbrloet ocol ands endtsh ems ecuerlya croiststs u nneclo nnection
levl,c ryptographsieccauelrdld ya tcaJ. nb ea llowteod ton odeB .N odeB checktsh ei ntegroifet ayc ht rans­
trJ\'ersc firewallssu bswtiatnhroiwuaetla lkle·n ing missioann d thend ecapsulaatncds f clrll'tahred s
securpitoyl icHyo.w evert,h ee ncapsulaptriootno col cbtagrarom sn etworYk. 'T hep roceissss ymmetric,
mustr equinroei mplitcriutsi tnt her outneord easn d althoutghhi issn ott 1icrurcd.
linktsh amta keu pt hef �1borfit ch ei nsecunrcet \\'ork. Thesem ethodcsa nb eu sedt oc onnecatn ys orotf
To solvteh ipsr oblemt,h ep rotoceomlp loyebdy private nethwoowrekv;eo ru,r p roducitss p ecifically
theA ltaVisTtuan neuls esa symhesoifst \\\'\O' ell­designteodc onnecTtPn etworLkwst unneli!nPdg a u­
understonoedt workicnogn strutcutnsn:c nlgip roto­ gr<lrnGsi.v ernb cd ominanocfe! Pi nt hen etworrkn Jr­
colasn'd s ecurceh :mnels.2 kcrlpactheec, h oicoefn etwortky piese asTlhe'c .ho ice
ofp rotocforlo m\ \'hiroc cho nstruct tcuonnnneelc ­
ProtocDoels ign tionissm ored ifficTuhletr.ea rtch reoeb vioucs:: tn­
didareLsl:'U ,s erD ar:1graPmr otoc(olU DP)Jn,d
Inc omputenre tworktsu,n neliinstg h aec ot fc nGlpsu­ Tr<msmissCioonn trProolt ocol (TCP).
lationnge c ommunicaprtoitooncosl within anotShienrcI.eP i sa n etwork prottohceorilesn, o n otioonf
Fore xapmlaeD ,E Cnet-int-uInPn emli ghttL 1nsporrp ort-ICJ\dt'dCrIe ssing.i mpTlhiiteshs a ItP -in-tIuPn ­
D.EnCetd arargamso veJrn I nternePtr otoc(olP l )n et­ nelmsu stb e mplemetned vercyl osteot heo perating
wcorku sinIg Pd atagramIsn. t hiJsr r:mgemcInPt , systeamn,d a nvm ultiplexoifrn ugn neclo nnections
btargamsa ct onlayt raasn spmoercti 1J.nism-irsh ermeu stb ee xplicJidtdlcyd S.i ncoeu rg oal\\ 'fa(sJo ru r
non eed fora ctthinevo ed eisn t heI P netwtoori kn ter­ tunnelipnrgo ducttob ef irewaanldlo peratisnygs tem
preotr r om anipultahteee ncapsulaDtEeCdn etp ack­ independewnet r,e jectIe idIn 't :l\o·f�o hr1i ghe-rcl\e·l
ersA. t unneall onheo,w evecra,n nogtu �1ranrrhc<aeln t protocol.
NETWORKX 1 TIUPPN ANCKEELTE D l NETWORKY
\
\ -'-' \ -'-'
(
<( <(
� T NODEA �--� � . �f--NO1DE f-B -�1
a: a:
lL lL
)
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1--- ------1
T INTERNTE T
Figeu 1r
A SecuTruen nienlO perarion
Di�itT�elc hnijcoauln ul Vol9. 0:o. 1929 7
Thec hiocbec rweUeDnP a ndT CPd epenodns thattu nnelo nietnnsed epndo t pbaec kawgietdh
whetdhaetra gorrab mysts et rebaemsastp ptloty un ­ ord eepndeonnat s epcififiercw ailmplel metnatni.o
neliSnnicge. aopuiprcli aotinis hn erenctolnycn teionE ventu,ta hleelm yegrinsgt anddswa ilrplr ob.alpbyr e­
orieednT,tC Po fefras n atufirraw,lh ialneyU DP vafiorls tattuinnce lhso;w evneosr t,a anrddesx ifsort
desimgunsi tcn ludeex palnmi ecaifntorsr leiacbonl­e tarnsi(emnboti lues)e arnsd o urs olutrieomna ins
nectmiaonint ennca.eI na ddiinot,b ytset reeailmmsi ­queiv tilaeb.
natceo nstrcaaiunstbesydp ackbeoutn diaersso,
fargmenattiaonnd immauxsmi dzeert meiinoapnto se Implementation
fwe difcifuiletsF.u rrtmhoerbey,t set reeamnasb le
formso fc ryptogarnaddp ahaty c omprestshiaotn A sw ithm antyu nniemlp lnetmaetsi,wo'en p rovide
wouldb ea wkwatroid m pleumseinntg mdsaO.tfa grtaunneblyti rnignc gtk hioep ernagst yiesmt'rsot uign
corusteh fliesx iitbdyio lcnso cto mwei thcoousTttC .P layietnrof orwdarinpga ckteoat nse mluatneedwt ork
addasn elxyaterra r eolfi taarbnlsesm iiosann,d perd­eviTchei.s ddeovenisoc tter anpsamciktde itrse, c tly
packheera daerrlcrsa g .e burta tiheten rac psautltesh emd ataaws i truah ngi h­er
Thep revdisoicuuss lseinondnocs l eaadrv aagnteto levperlo tloT.ch oeA l:NtisTtuan neilm plnetmiaeotn
etihepror tocoopilto .n Wceoh steo i mepmlentth e coanittnhser em ajcoorpm onesnt:ht tenu nealp plica­
AtlaViTsuntnaeu ls iInPg-- iTnCiPno rdteosr i mlpi' f) toint,h per otohcaonllde, ar ntdh pees uodd-evidcrei ­
fierwaslcelu rypi otlyiA.s cs howinnF i ugr2e,a t unnel veTrh.em ajnfu nctioofn t thnuene la pipclatiitsoo n
connecutsiuoatnlr layv eartlsa eesostn efri eawlIln. inetrawcittt hh ues eorrs ystaedmm sitnriaatnodtro
prtaiccaer n,u nevli rtcuoanelnc tiiocsno pmoseodf moditf)rh sey streomtu intga btloem sa ekt unlneed
sevedritasiln TcCtP c onnieocnltsa iedn do--te.n d rouatvelasaj bTlhei.s aclomsdaoei a nnjtsad abtaasoef
'vVhcerT CPc onnejcotnmse etth,e iraseb iidrteicoln aaccaebplptea rtenndepro sia nntdm athcincgr yop­t
relparyo ctehsassth fl uefpsa ckienet ihste drie rcito.n garphkiecy Tsh.ep rotohcaonld ilmpelre mset nhte
Sucahr elsaeyr viicneuc dleiwdsi tmho sttri wealls.'t unneelnc aspuiloapntr otoacnoadll a ls socciraytpe­d
Wea losforf a eni neltlgienrtley at ahtp articiintph aet etso graTphhepy s.ue do-devidcirevi ersre spontsori ble
tuncnoenln ecptriootnoa cntodlh r eeofrael wlsmo ore rdeiercntgip ackteolrm·s t hleo cIaPls tatcokt h e
felxiilbyii ncth oosdisentagit nieonndo pnits. encaaptsiupolrno tohcaonlldea rn vdi vceer sa.
Byu siTnCgPc onnecatnirdoe nylsswa ,em iinmize Fiugre3 shows thhoecw o mopnesn otft he
thpeo lcihcayen srg equtiorpe emdri t ttuxnarnvse.eal J AltiasVTtuan nelc ooperate ttuo nlnpeerIdoP c ess
Altlh aitsn ecesissta ore yna blTeC Pc oncnteionsp ackTehtedsai .g radme piacs tisnu gslecerl- iaennadt
betwetehtneu nneendlp oiwnhti,ic oshn t hper ivatteu nnseelr vAeltrh.o utghhes ambea ssi-ucu cture
netwoarnktd,h ree l,w ahyihi cjss uto utstihdfieer e­ applsit eo taulnlne enldo pnits oftwatrheea,rr ese ub ­
wall(.No tteh raetl aaryleso gliyloc uatsidfier eatwlhle, s tandtfieifraeln bceetsw seienn-g suleearn sde rcvone­r
atlhoutghhem yi ghti mbpele entmeodn t hfier elwla figuiroantasn,db etwetehnUe N IXa ndW idnows
mach.iW)nh eethage ern eorrai nci tneilglernetyli as implnetmaetiFooernx sa.me p,tl hsei nugslveeer-r sion
usefdri,e wlatlr-avecronsneaclt iaolanwysos r igei nautsuarlulnoysn lwyh itlheue s eiras c ticvoennleyec dt.
ona l oaclcloyn tlerldon ewtrokF.u trherrmeTo,C P Ont hsee rsviedrt eht,eu nnealp pclaitiiasod n ea mon
conenctiroenqe ustasr ie nrqfeuenatn,dt heorreef proctehscasot n ntuiouslfyor c woanjniteoscrn te qesuts
TCPt ravleasrr smeao rter abcltteaol oagtt hfieer walla nsde rveixcinesgsct oinnecTthiefoo lnolswi.n tgh ree
thaanrd cat agrAaltmhso.u tghhfie r eawliln sdtuhrays sectdiiosncstu hsiesn dilvs iydsutaem components in
begtuond eveslatonprd dafsor I -Pint-uInPn 'eo"lu sr, detaani,dwl h earpep ropproniiatot uet, dj tffehree nces
chcoeio fI P-TiCnP- giuvste hsce laera dvaagnet betwteheVen"J Jiosuoftsw arceo nfigurations.
SINGEL-USER TUNNEL
TUNNEL RELAY FIRWEALL SERVER
I I
INTERNET
Figeu r2
Tunnweilt Ihn tieglelRnetl ay
DigiTr��chl nica)lo urn"l Vol9. No.2 1997 7
SIGNLE-USETRU NNEL TUNNELS ERVER
TUNNELA PPLCIATION
.
r
PROTOCOL PROTOCOL• I'" • , IPS TACK
HANDLER HANDLER
II
u
I
NETWORK NETWORK
PSEUDO-DEVICE DEVICE PSEUDO-DEVICE1 DEVICE
I
, r
Y. • INTERNET • • • ...
PRIAVTEN ETWORK
KEY:
ENCRYPTED
UNENCRYPTED
Figeu r3
Svstem CompoannednD tast Fal ow
TheT unnelA pplication Routing
Asm entiiontnh eIedmp lmeetnatisoeinco tonu,tr nu ­
Thep rimflamrcyt ioofrn h tcu nnaeplp licisa titoon new lo rbkysm anipiuoolnfta htsey streoimu nttga eb.l
preensatu seitrnre afc(eU IA)tl.h ouegahci hna snttiaI­n somoen meensnvs,tiu hrca s\V inodws95 t, heirse
tioofn utshieern e tr1fciess il ghdtiflfeyr etnhftel, m c­nof luliyne tgrantoetdi oofpn a ckreotiu nt(gos me­
tioonf t hea pipclatrieomnsa itnheS<1 111C. The timceasl IlPte r(dwJ raidngH)o.w evtehrei,rs seu pport
AJtaViPsetras Tounnanle' 9l7a s, inugslceeor-n figufroram ­uilptnleet wdoervkei. sEc ach nedtewvobirackes
tioonffe,r ass trtaotirgwhagrrda ipchuaslei trnre bce au nieqlauys siIgPnae drdde ssos tthhIaePts taccakn
(GU(ls)Fe ieug er4 )t haaltl otwhuses reorr egias tedre tmeiern whicdhevi cteou sweh etnar nsmitting
set ofr utnnaesrleg revts eerlsfe,orc mtt hsiesa tn,d packTehtAesl .atV iTsutnan epls eudoe-a dpepveiacrs
theens tabalnidts eha dro wnc onnectTihoen st.ot heo pernagst yistaesjm s uta notnheetrw ork
empshiaisos n s imlcpiiyA.t tunneclo nnectiboen dmeavyi Tchee.ri esa o ne-nteor -eolnasthibioept ween
starftoremed ih tearc ommalneidi n netrafcoer thet nunecolnn ectainopdns se ou-ddevDiucreicsn.og n ­
GUII.f GtUhIieus s etdos taatr utn ntehGleU, Iw in­ necteisaotbnsl himetnhtte,nu neaplp liaccattiivoant es
dowc abne m iniiezmda nidg noredt heeun nodtf i la p seuddeov-iacnedm odiieftsh reo iunttga btloe
thteu enlsne ssioTnh.e� l lpaiptciloongasli ltn ernegs tiicnluadneny e wrleyca habplrei vnaettew oorrn ke t­
eve,nr tesflceurcrtesns tt atthoeru gthh ues eirne tr­ \ovr.kT shea pplaitcitohner ne sttohroeerg sii nsatla te
fcaea,n ndo ftiietshu es oefre xcoenpeatvlie nItnts h.i s upotnem rinatoifto hcneo nnection.
congfiuratioonnlt,yrf acfi h-olmco aalp ipclatiiso nsT he tsuenrniveiselmp r l emeedin natr ciherrou ting
dierctoevdet rht eu nnaennldo, i bnountdu ncnoenl­ evniornmenEta.c she rtvyecprai lrloyu atnees n tIiPr e
nectrieoqsnut aersca cceedp.t cl-asCss ub\nverotk( 25a4dr dessbeumst)a ys puport
Int hsee rcvoenrfi agtuirrohnte,u nanpepll iicsa tipoarnt siuabelnt woorrkm sul tinpewltoer kass lwA.e l
sigfincialnymt oerc omplaitc.eT dhper imta.lrmtyci on tunnesle rcvaemnra nitamiuntl ipclonene ctiaonnds ,
oft hsee rverit sco ro edsetr rnuinceatcl c teos;J sut ho­ thiasc ocmisp libsyah sesndii gnadg i effreInPatd rdess
rizceilde n.Tt osa chitehvies s,e rtavhpeepr al tiiicosn toe acphsu edov-idceteu/ncnoennle ct.Ii Ppos neudo­
�l1sroe sspiobntlorie s isnucgr yopgatrphcirdcee ntiadlesv aidcrdee s:stbetos te hn dosft hrenu naerlac s signed
and imnaantiinagna tuhorizdaabttaia.soI enna did­ dyutmicaolrsl tya tiforcmaa l ployoo l'fI Pa drdesses
titonoa cpcteicnognn ectiato unnssn,ee rliv csea rp a­conotllrebdy t he sTehreov peertr.ia snyges mtc,om ­
bloef i ntiinagtt ihem.t h"Iewn o rrkogupt"u nnelb idn weitahr ouitnmga neamgenptr ogrsaumca hs
confiagtui,rto wnos ersvc eoropetroam taei ntaa ing atepde/<xr mtsa lnle cesrsoaurptyre o piaognAsa .t
permanceonntn e,cf tori oenxabmeptlweae c eonr po­dsicusisnte hdne e xste cteiaoctnhnu, n euls ecrabn e
ranteet waonradkr emootfefi lcoec aarlen ae wtork restrtiosc ptaee cdsi eofitfc ia Pd edsrsTebsia.sp proach
(ALN)A. t nunseelr ivaset rIl.- tIle1degdr ou-tietjrso b allonwest\ vomranka getroes s btlairsohiu ntpgo yl ic
is fortwoa pradc kfeortmts h e pronteetcwitotnerodk basedu soecnrl . a ssoTob itanfni er-iagnc ontorvoelr
thteu nannevdli vceer Wseao .fe frs ervteorbr ost rhh e ag ivteunn nceonlne ctitohnse,e rcvaeanrl so a run
UNIaXn d Wtihned oNwTse vniornments. packfielettr-ipnrgo grsaumca hss creteorn eds't trhiec t
IPp rotoecnotlesar niednx gi ttihntagnut n el.
DigitT,clclh nic)JoIu rnl,l Vol9. No.2 1997