CHAPTER 1m
Introduction
Solutions to Review Questions and Exercises
m m m m m
ReviewmQuestions
1. Them fivem componentsm ofm am datam communicationm systemm arem them sender,m receive
r,
transmissionmmedium,mmessage,mandmprotocol.
2. Themadvantagesmofmdistributedmprocessingmaremsecurity,maccessmtomdistributedmdat
a-mbases,mcollaborativemprocessing,mandmfastermproblemmsolving.
3. Themthreemcriteriamaremperformance,mreliability,mandmsecurity.
4. Advantagesmofmammultipointmovermampoint-to-
pointmconfigurationm(typemofmconnec-
m tion)mincludemeasemofminstallationmandmlowmcost.
5. Linemconfigurationsm(ormtypesmofmconnections)marempoint-to-pointmandmmultipoint.
6. Wemcanmdividemlinemconfigurationminmtwombroadmcategories:
a. Point-to-point:mmesh,mstar,mandmring.
b. Multipoint:mbus
7. Inmhalf-duplexmtransmission,monlymonementitymcanmsendmatmamtime;minmamfull-
duplexmtransmission,mbothmentitiesmcanmsendmatmthemsamemtime.
8. Wemgivemanmadvantagemformeachmofmfourmnetworkmtopologies:
a. Mesh:msecure
b. Bus:measyminstallation
c. Star:mrobust
d. Ring:measymfaultmisolation
9. Themnumbermofmcablesmformeachmtypemofmnetworkmis:
a. Mesh:mnm(nm–m1)m/m2
b. Star:mn
c. Ring:mnm–m1
d. Bus:monembackbonemandmnmdropmlines
10. Them generalm factorsm arem size,m distancesm (coveredm bym them network),m structure,m a
nd
ownership.
1
,2
11. Anminternetmismanminterconnectionmofmnetworks.mThemInternetmismthemnamemofmam
spe-mcificmworldwidemnetwork
12. Amprotocolmdefinesmwhatmismcommunicated,minmwhatmwaymandmwhen.mThismprovi
desmaccuratemandmtimelymtransfermofminformationmbetweenmdifferentmdevicesmonma
mnet-m work.
13. Standardsmaremneededmtomcreatemandmmaintainmanmopenmandmcompetitivemmarketm
formmanufacturers,mtomcoordinatemprotocolmrules,mandmthusmguaranteemcompatibilit
ymofmdatamcommunicationmtechnologies.
Exercises
14. Unicodemusesm32mbitsmtomrepresentmamsymbolmormamcharacter.mWemcanmdefinem232md
iffer-mentmsymbolsmormcharacters.
15. Withm16mbits,mwemcanmrepresentmupmtom216mdifferentmcol
ors.m16.
a. Cablemlinks:mnm(nm–m1)m/m2m=m(6mm5)m/m2m=m15
b. Numbermofmports:m(nm–m1)m=m5mportsmneededmpermdevice
17.
a. Meshmtopology:mIfmonemconnectionmfails,mthemothermconnectionsmwillmstillmbemw
ork-ming.
b. Starmtopology:mThemothermdevicesmwillmstillmbemablemtomsendmdatamthroughmthem
hub;mtheremwillmbemnomaccessmtomthemdevicemwhichmhasmthemfailedmconnectionmt
omthemhub.
c. BusmTopology:mAllmtransmissionmstopsmifmthemfailuremisminmthembus.mIfmthemdrop
-linemfails,monlymthemcorrespondingmdevicemcannotmoperate.
d. RingmTopology:mThemfailedmconnectionmmaymdisablemthemwholemnetworkmunles
smitmismamdualmringmormtheremismamby-passmmechanism.
18. ThismismamLAN.mThemEthernetmhubmcreatesmamLANmasmwemwillmseeminmChapterm13.
19. Theoretically,minmamringmtopology,munpluggingmonemstation,minterruptsmthemring.mH
ow-
mever,mmostmringmnetworksmusemammechanismmthatmbypasses mthemstation;mthemringm
canmcontinuemitsmoperation.
20. Inmambusmtopology,mnomstationmisminmthempathmofmthemsignal.mUnpluggingmamstation
mhasmnomeffectmonmthemoperationmofmthemrestmofmthemnetwork.
21. SeemFigurem1.1
22. SeemFigurem1.2.
23.
a. E-
mailmismnotmanminteractivemapplication.mEvenmifmitmismdeliveredmimmediately,mit
mmaym stayminmthem mail-
boxmofmthemreceivermformamwhile.mItmismnotmsensitivemtomdelay.
b. Wemnormallymdomnotmexpectmamfilemtombemcopiedmimmediately.mItmismnotmveryms
ensi-mtivemtomdelay.
c. SurfingmthemInternetmismthemanmapplicationmverymsensitivemtomdelay.mWemexcept
mtomgetmaccessmtomthemsitem wemaremsearching.
24. Inmthismcase,mthemcommunicationmismonlymbetweenmamcallermandmthemcallee.mAmded
,i-m catedmlinemismestablishedmbetweenmthem.mThemconnectionmismpoint-to-point.
, 3
Figurem1.1m m SolutionmtomExercisem21
Hub
Station Station Station Station
Repeater Repeatmer
Station Station Station Station
Repeatmer
Station
Figurem1.2m m SolutionmtomExercisem22
Station Station
Repeater
Repeater
Station Station
25. Themtelephonemnetworkmwasmoriginallymdesignedmformvoicemcommunication;mthemI
nternetmwasmoriginallymdesignedmformdatamcommunication.mThemtwomnetworksmare
msimilarminmthem factmthatmbothmaremmademofminterconnections mofmsmallmnetworks.m
Themtelephonemnetwork,masmwemwillmseeminmfuturemchapters,mismmostlymamcircuit-
switchedmnetwork;mthemInternetmismmostlymampacket-switchedmnetwork.
Introduction
Solutions to Review Questions and Exercises
m m m m m
ReviewmQuestions
1. Them fivem componentsm ofm am datam communicationm systemm arem them sender,m receive
r,
transmissionmmedium,mmessage,mandmprotocol.
2. Themadvantagesmofmdistributedmprocessingmaremsecurity,maccessmtomdistributedmdat
a-mbases,mcollaborativemprocessing,mandmfastermproblemmsolving.
3. Themthreemcriteriamaremperformance,mreliability,mandmsecurity.
4. Advantagesmofmammultipointmovermampoint-to-
pointmconfigurationm(typemofmconnec-
m tion)mincludemeasemofminstallationmandmlowmcost.
5. Linemconfigurationsm(ormtypesmofmconnections)marempoint-to-pointmandmmultipoint.
6. Wemcanmdividemlinemconfigurationminmtwombroadmcategories:
a. Point-to-point:mmesh,mstar,mandmring.
b. Multipoint:mbus
7. Inmhalf-duplexmtransmission,monlymonementitymcanmsendmatmamtime;minmamfull-
duplexmtransmission,mbothmentitiesmcanmsendmatmthemsamemtime.
8. Wemgivemanmadvantagemformeachmofmfourmnetworkmtopologies:
a. Mesh:msecure
b. Bus:measyminstallation
c. Star:mrobust
d. Ring:measymfaultmisolation
9. Themnumbermofmcablesmformeachmtypemofmnetworkmis:
a. Mesh:mnm(nm–m1)m/m2
b. Star:mn
c. Ring:mnm–m1
d. Bus:monembackbonemandmnmdropmlines
10. Them generalm factorsm arem size,m distancesm (coveredm bym them network),m structure,m a
nd
ownership.
1
,2
11. Anminternetmismanminterconnectionmofmnetworks.mThemInternetmismthemnamemofmam
spe-mcificmworldwidemnetwork
12. Amprotocolmdefinesmwhatmismcommunicated,minmwhatmwaymandmwhen.mThismprovi
desmaccuratemandmtimelymtransfermofminformationmbetweenmdifferentmdevicesmonma
mnet-m work.
13. Standardsmaremneededmtomcreatemandmmaintainmanmopenmandmcompetitivemmarketm
formmanufacturers,mtomcoordinatemprotocolmrules,mandmthusmguaranteemcompatibilit
ymofmdatamcommunicationmtechnologies.
Exercises
14. Unicodemusesm32mbitsmtomrepresentmamsymbolmormamcharacter.mWemcanmdefinem232md
iffer-mentmsymbolsmormcharacters.
15. Withm16mbits,mwemcanmrepresentmupmtom216mdifferentmcol
ors.m16.
a. Cablemlinks:mnm(nm–m1)m/m2m=m(6mm5)m/m2m=m15
b. Numbermofmports:m(nm–m1)m=m5mportsmneededmpermdevice
17.
a. Meshmtopology:mIfmonemconnectionmfails,mthemothermconnectionsmwillmstillmbemw
ork-ming.
b. Starmtopology:mThemothermdevicesmwillmstillmbemablemtomsendmdatamthroughmthem
hub;mtheremwillmbemnomaccessmtomthemdevicemwhichmhasmthemfailedmconnectionmt
omthemhub.
c. BusmTopology:mAllmtransmissionmstopsmifmthemfailuremisminmthembus.mIfmthemdrop
-linemfails,monlymthemcorrespondingmdevicemcannotmoperate.
d. RingmTopology:mThemfailedmconnectionmmaymdisablemthemwholemnetworkmunles
smitmismamdualmringmormtheremismamby-passmmechanism.
18. ThismismamLAN.mThemEthernetmhubmcreatesmamLANmasmwemwillmseeminmChapterm13.
19. Theoretically,minmamringmtopology,munpluggingmonemstation,minterruptsmthemring.mH
ow-
mever,mmostmringmnetworksmusemammechanismmthatmbypasses mthemstation;mthemringm
canmcontinuemitsmoperation.
20. Inmambusmtopology,mnomstationmisminmthempathmofmthemsignal.mUnpluggingmamstation
mhasmnomeffectmonmthemoperationmofmthemrestmofmthemnetwork.
21. SeemFigurem1.1
22. SeemFigurem1.2.
23.
a. E-
mailmismnotmanminteractivemapplication.mEvenmifmitmismdeliveredmimmediately,mit
mmaym stayminmthem mail-
boxmofmthemreceivermformamwhile.mItmismnotmsensitivemtomdelay.
b. Wemnormallymdomnotmexpectmamfilemtombemcopiedmimmediately.mItmismnotmveryms
ensi-mtivemtomdelay.
c. SurfingmthemInternetmismthemanmapplicationmverymsensitivemtomdelay.mWemexcept
mtomgetmaccessmtomthemsitem wemaremsearching.
24. Inmthismcase,mthemcommunicationmismonlymbetweenmamcallermandmthemcallee.mAmded
,i-m catedmlinemismestablishedmbetweenmthem.mThemconnectionmismpoint-to-point.
, 3
Figurem1.1m m SolutionmtomExercisem21
Hub
Station Station Station Station
Repeater Repeatmer
Station Station Station Station
Repeatmer
Station
Figurem1.2m m SolutionmtomExercisem22
Station Station
Repeater
Repeater
Station Station
25. Themtelephonemnetworkmwasmoriginallymdesignedmformvoicemcommunication;mthemI
nternetmwasmoriginallymdesignedmformdatamcommunication.mThemtwomnetworksmare
msimilarminmthem factmthatmbothmaremmademofminterconnections mofmsmallmnetworks.m
Themtelephonemnetwork,masmwemwillmseeminmfuturemchapters,mismmostlymamcircuit-
switchedmnetwork;mthemInternetmismmostlymampacket-switchedmnetwork.
