计网第五次作业讲课稿.doc

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1、计网第五次作业精品文档ReviewQuestions:1.Whataresomeofthepossibleservicesthatalink-layerprotocolcanoffertothenetworklayer?Whichoftheselink-layerserviceshavecorrespondingservicesinIP?InTCP?链路层协议提供给网络层的服务有哪些？哪些是给IP的？哪些是给TCP的？Linkaccess,framing,reliabledeliverybetweenadjacentnodes,

2、flowcontrol,errordetection,errorcorrection,half-duplexandfull-duplex.InIP:framing,errordetection.InTCP:framing,reliabledeliverybetweenadjacentnodes,errordetection,half-duplexandfull-duplex.2.IfallthelinksintheInternetweretoprovidereliabledeliveryservice,wouldtheTCPre

3、liabledeliveryserviceberedundant?Whyorwhynot?不会多余，因为TCP保证的是传输层的数据传送，而link提供稳定可靠传输保证链路层的传输稳定，二者不完全重叠，所以TCP可靠传输也不会多余。3.InSection5.3,welistedfourdesirablecharacteristicsofabroadcastchannel.WhichofthesecharacteristicsdoesslottedALOHAhave?Whichofthesecharacteristicsdoesto

4、kenpassinghave?4.SupposetwonodesstarttotransmitatthesametimeapacketoflengthLoverabroadcastchannelofrateR.Denotethepropagation收集于网络，如有侵权请联系管理员删除精品文档delaybetweenthetwonodesasdprop.Willtherebeacollisionifdprop

5、一个分组还没离开B，所以发生碰撞。7.SupposenodesA,B,andCeachattachtothesamebroadcastLAN(throughtheiradapters).IfAsendsthousandsofIPdatagramstoBwitheachencapsulatingframeaddressedtotheMACaddressofB,willC’sadapterprocesstheseframes?Ifso,willC’sadapterpasstheIPdatagramsintheseframestoth

6、enetworklayerC?HowwouldyouranswerschangeifAsendsframeswiththeMACbroadcastaddress?不会，C会拆封帧从而读取报头的MAC，因为每一个host的MAC都唯一，C读取到数据报中的MAC和自己的不一样就不会继续拆封数据报，不会投递给C。当使用LAN口广播地址的时候，C的适配器就会拆封帧，向C传递数据。8.HowbigistheMACaddressspace?TheIPv4addressspace?TheIPv6addressspace?2^48，2^32，2

7、^128.9.WhyisanARPquerysentwithinabroadcastframe?WhyisanARPresponsesentwithinaframewithaspecificdestinationMACaddress?收集于网络，如有侵权请联系管理员删除精品文档因为新加入网络的主机是不知道路由器的IP的，自己也没有IP，所以只能广播才能得到IP。因为每个主机的MAC地址都是唯一的，而ARP建立转发表的时候会带上MAC地址。12.InCSMA/CD,afterthefifthcollision,whatisthep

8、robabilitythatanodechoosesK=4?TheresultK=4correspondstoadelayofhowmanysecondsona10MbpsEthernet?可能，因为第五次K的取值范围是0-(2^5-1)即0-31。Bittim