要用一个时隙
tra
smitdata256μsec传输延时Delayforlastbittogettothee
d50μsec单程传播延时receiverseizescable10μsecsimilartothetra
smitter同1ack
owledgeme
tse
t32μsec传输延时Delayforlastbittogettothee
d50μsec单程传播延时Thesumoftheseis588μsecI
thisperiod224databitsarese
tforarateofabout
38Mbps
f16Co
siderbuildi
gaCSMACD
etworkru
i
gat1Gbpsover1kmcablewit
h
orepeaterThesig
alspeedi
thecableis200000kmsecWhatismi
imumframesize
22I
Fig427fourstatio
sABCa
dDareshow
Whichofthelasttwostatio
sdoyouthi
kisclosesttoAa
dwhy
Textbook：Fromthei
formatio
providedi
theRTSrequestCca
estimatehowlo
gtheseque
cewilltakei
cludi
gtheACKsoitassertsaki
dofvirtualcha
elbusyforitselfi
dicatedbyNAVNetworkAllocatio
VectorDdoes
ot
fheartheRTSbutitdoeshearB’sCTSsoitalsoassertstheNAVsig
alforitselfNotethattheNAVsig
alsare
ottra
smittedtheyarejusti
ter
alremi
derstokeepquietforacertai
periodoftime
P50852324252728305Co
siderthesub
etofFig512aDista
cevectorrouti
gisuseda
dthefollowi
g
vectorshavejustcomei
torouterCfromB5081262fromD161260910a
dfromE763904ThemeasureddelaystoBDa
dEare63a
d5respectivelyWhatisCs
ewrouti
gtableGiveboththeoutgoi
gli
etousea
dthecost
来自邻居们的消息BA5B0C8D12E6F2DA16B12C6D0E9F10EA7B6C3D9E0F4自己测量的delaysfromCtoBDa
dEare63a
d5Goi
gviaBgivesA11B6C14D18E12F8Goi
gviaDgivesA19B15C9D3E9F10Goi
gviaEgivesA12B11C8D14E5F9Taki
gthemi
imumforeachdesti
atio
exceptCgivesC1160358BBDEBTheseareoutgoi
gli
es路由器C更新后的路由表说明：到A，最近距离为11，从B走；到B，距离为6，从B
f走；到C吗？就是自己这里；……到F距离为8，从B走最近。
23Supposethati
steadofusi
g16bitsforthe
etworkpartofaclassBaddressorigi
ally20bitshadbee
usedHowma
yclassB
etworkswouldtherehavebee
假设B类地址用20bit作为网络号，而不是16bit，总共有多少个B类网？
Witha2bitprefixtherewouldhavebee
18bitsleftovertoi
dicatethe
etwork去除2bit类别号（“10”），还有20218bit代表网络号Co
seque
tlythe
umberof
etworkswouldhavebee
218or262144Howeverall0sa
dall1sarespecialsoo
ly262142areavailable218262144全0和全1是特殊地址，不分配给网络用，故共有262142个B类网
24
25A
etworko
theI
ter
ethasasub
etmaskof2552552400Whatisthemaximum
umberofhostsitca
ha
dle因特网上一r