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CREST CRT syllabus - extra questions and answers
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CREST CRT syllabus - extra questions. and answers
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CREST CRT SYLLABUS - EXTRAQUESTIONS AND ANSWERS
What uis uTETRA? u- uCorrect uAnswer u- uTerrestrial uTrunked uRadio u(TETRA; uformerly
uknown uas uTrans-European uTrunked uRadio) uis ua uprofessional umobile uradio uand utwo-
way utransceiver uspecification. uTETRA uwas uspecifically udesigned ufor uuse uby
ugovernment uagencies, uemergency uservices, u(police uforces, ufire udepartments,
uambulance) ufor upublic usafety unetworks, urail utransport ustaff ufor utrain uradios, utransport
uservices uand uthe umilitary.
What uis uMPLS? u- uCorrect uAnswer u- uMultiprotocol uLabel uSwitching u(MPLS) uis ua utype
uof udata-carrying utechnique ufor uhigh-performance utelecommunications unetworks uthat
udirects udata ufrom uone unetwork unode uto uthe unext ubased uon ushort upath ulabels urather
uthan ulong unetwork uaddresses, uavoiding ucomplex ulookups uin ua urouting utable.
5 uCommon uICMP umessages? u- uCorrect uAnswer u- u1. uPing urequest/reply u(8, u0), u2.
udestination uunreachable u(3), u3. uredirect u(5), u4. utimestamp u(13) uand utimestamp ureply
u(14), u5. utime uexceeded u(11)
Why uwas uISO u31000:2009 ucontentious uin uits udefinition uof urisk? u- uCorrect uAnswer u-
uOne uof uthe ukey uparadigm ushifts uproposed uin uISO u31000 uis ua ucontroversial uchange
uin uhow urisk uis uconceptualised. uUnder uthe uISO u31000:2009 uand ua uconsequential
umajor urevision uof uthe uterminology uin uISO uGuide u73, uthe udefinition uof u"risk" uis uno
ulonger u"chance uor uprobability uof uloss", ubut u"the ueffect uof uuncertainty uon uobjectives"
u... uthus ucausing uthe uword u"risk" uto urefer uto upositive upossibilities uas uwell uas unegative
uones. u- uWikipedia
What uis uthe umain u2G ustandard? u- uCorrect uAnswer u- uGSM
What uis uthe umain u2.5G ustandard? u- uCorrect uAnswer u- uGPRS u2.5G u("second uand ua
uhalf ugeneration") uis uused uto udescribe u2G-systems uthat uhave uimplemented ua upacket-
switched udomain uin uaddition uto uthe ucircuit-switched udomain. uIt udoes unot unecessarily
uprovide ufaster uservice ubecause ubundling uof utimeslots uis uused ufor ucircuit-switched
udata uservices u(HSCSD) uas uwell.
The ufirst umajor ustep uin uthe uevolution uof uGSM unetworks uto u3G uoccurred uwith uthe
uintroduction uof uGeneral uPacket uRadio uService u(GPRS). uCDMA2000 unetworks
usimilarly uevolved uthrough uthe uintroduction uof u2.5G. uIts uapproach ucentred uon uthe uuse
uof upacket udata. uUp uuntil uthis utime uall ucircuits uhad ubeen udedicated uto ua ugiven uuser
uin uan uapproach uknown uas ucircuit uswitched, ui.e. uwhere ua ucomplete ucircuit uis uswitched
ufor ua ugiven uuser. uThis uwas uinefficient uwhen ua uchannel uwas uonly ucarrying udata ufor ua
usmall upercentage uof uthe utime. uThe unew upacket uswitched uapproach urouted uindividual
, upackets uof udata ufrom uthe utransmitter uto uthe ureceiver uallowing uthe usame ucircuit uto ube
uused uby udifferent uusers. uThis uenabled ucircuits uto ube uused umore uefficiently uand
ucharges uto ube umetered uaccording uto uthe udata utransferred.
What uis uthe umain u2.75G ustandard? u- uCorrect uAnswer u- u2.75G u(EDGE)
See ualso: uEnhanced uData uRates ufor uGSM uEvolution
GPRS unetworks uevolved uto uEDGE unetworks uwith uthe uintroduction uof u8PSK
uencoding, uWhile uthe usymbol urate uremained uthe usame uat u270.833 usamples uper
usecond, ueach usymbol ucarried uthree ubits uinstead uof uone. uEnhanced uData urates ufor
uGSM uEvolution u(EDGE), uEnhanced uGPRS u(EGPRS), uor uIMT uSingle uCarrier u(IMT-
SC) uis ua ubackward-compatible udigital umobile uphone utechnology uthat uallows uimproved
udata utransmission urates, uas uan uextension uon utop uof ustandard uGSM. uEDGE uwas
udeployed uon uGSM unetworks ubeginning uin u2003—initially uby uAT&T uin uthe uUnited
uStates.
EDGE uis ustandardized uby u3GPP uas upart uof uthe uGSM ufamily uand uit uis uan uupgrade
uthat uprovides ua upotential uthree-fold uincrease uin ucapacity uof uGSM/GPRS
unetworks.The u2G udigital uservice uprovided uvery uuseful ufeatures, usuch uas ucaller uID,
ucall uforwarding, uand ushort umessaging.
What uhigh uspeed udata uaccess uprotocol udo u3G uand u4G uuse? u- uCorrect uAnswer u-
uHigh uSpeed uPacket uAccess u(HSPA) uis uan uamalgamation uof utwo umobile uprotocols,
uHigh uSpeed uDownlink uPacket uAccess u(HSDPA) uand uHigh uSpeed uUplink uPacket
uAccess u(HSUPA), uthat uextends uand uimproves uthe uperformance uof uexisting u3G
umobile utelecommunication unetworks uutilizing uthe uWCDMA uprotocols. uA ufurther
uimproved u3GPP ustandard, uEvolved uHigh uSpeed uPacket uAccess u(also uknown uas
uHSPA+), uwas ureleased ulate uin u2008 uwith usubsequent uworldwide uadoption ubeginning
uin u2010. uThe unewer ustandard uallows ubit-rates uto ureach uas uhigh uas u337 uMbit/s uin
uthe udownlink uand u34 uMbit/s uin uthe uuplink. uHowever, uthese uspeeds uare urarely
uachieved uin upractice.
What ukey ugeneration udoes uGSM uuse? u- uCorrect uAnswer u- uA8: uGSM umakes uuse uof
ua uciphering ukey uto uprotect uboth uuser udata uand usignaling uon uthe uvulnerable uair
uinterface. uOnce uthe uuser uis uauthenticated, uthe uRAND u(delivered ufrom uthe unetwork)
utogether uwith uthe uKI u(from uthe uSIM) uis usent uthrough uthe uA8 uciphering ukey
ugenerating ualgorithm, uto uproduce ua
ciphering ukey u(KC). uIt uis uoperator-dependent. uIn umost uproviders uthe uA3 uand uA8
ualgorithms uare ucombined uinto ua usingle uhash ufunction uknown uas uCOMP128. uThe
uCOMP128 ucreates uKC uand uSRES, uin ua usingle uinstance.
What uauthentication ualgorithm udoes uGSM uuse? u- uCorrect uAnswer u- uA3: uFirstly, ua
u128 ubit urandom unumber u(RAND) uis utransmitted uto uthe umobile ustation uover uthe uair
uinterface. uThe uRAND uis upassed uto uthe uSIM ucard, uwhere uit uis usent uthrough uthe uA3
uauthentication ualgorithm utogether uwith uthe uKI. uThe uoutput uof uthe uA3 ualgorithm, uthe
usigned uresponse u(SRES) uis utransmitted uvia uthe uair uinterface ufrom uthe umobile ustation
uback uto uthe unetwork. uThe uA3 ualgorithm uis ua uone-way ufunction. uThat umeans uit uis
ueasy uto ucompute uthe uoutput uparameter uSRES uby
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