计算机网络第四章总结

这可让他犯了难，施工现场距离项目部很远，没有车还真是不方便office,branchoffices(jurisdiction),riskmanagement,marketingmanagementsectorthroughsupervisionandinspectionfoundproblems,shouldbeassignedtheinvestigatorsarecorrectedinatimelymanner.27ththefifthchapterpenaltyunderanyofthefollowingacts,thentherelevantprovisionstopunishtheinvestigators,accordingtotheBank.Toconstituteacrimeshallbeinvestigatedforcriminalresponsibility:(A)onthebusinessthatarenotinvolvedintheinvestigation,issuedasurvey.(B)customercreditinformationarenotthoroughverification.(Iii)toparticipateincreditcustomersurveyisnotinplace,customersanddataisincomplete,untrue;heknowsbearacounterfeitedclientsissuingcredit.(D)doesnotprovideforduediligenceofcreditbusiness,pre-loaninvestigationform,concealingfactsorprovidingfalseinformationorshouldbefoundinanormalinvestigationfailedtodiscovertheriskfactors,leadtothereviewandapprovalpolicyerrors,loanrisk.(Five)onloanguaranteesofsurveynotinplace,notbyprovidesonarrived,andpledgerealforfieldverification,andassessment,andidentificationandregistration,notaccordingtoprovidesonguarantorofguaranteesqualificationandguaranteescapacityforsurveyverified,ledtoguaranteesloanlostauthenticity,andlegitimacy,andeffectivenessof;cycleloanbusinessintheofmortgage计算机网络第四章（网络层）总结4.1网络层概述：1网络层的主要功能：网络层实现了端到端的数据传输。网络互联:在不同的网络之间转发数据，向传输层提供统一的数据传输主机/路由器编址:每个网络接口有一个唯一的IP地址路由选择:根据数据携带的目的主机地址为数据包选择一条的路径，以到达目的主机分段:当数据包长度超过输出接口所连接的网络的限制时，应拆分成多个数据包.网络互联层次:从网络体系结构的层次观点来考察，网络互联可在四个层次上实现：物理层:中继器/集线器数据链路层:网桥/交换机网络层:路由器网络层以上:网关网络互联的归纳:物理层：使用中继器或集线器在不同的电缆段之间复制位信号，无寻址功能；数据链路层：使用网桥或交换机在局域网之间存储转发数据帧，用MAC地址寻址；网络层：使用路由器在不同的网络之间存储转发分组，用IP地址寻址；传输层及应用层：用网关提供更高层次的互连，用端口号或其他特定标识寻址。2虚电路网络(提供面向连接的服务)面向连接:发送数据之前，源主机和目的主机之间首先要建立一条虚连接，只是逻辑上的连接.整个数据传输过程分为：建立虚连接、传输数据、拆除虚连接三个阶段虚电路表:输入接口输入VCI（标识）输出接口输出VCI输入接口和输入VCI唯一标识一条虚电路，后续的数据报只需携带VCI无需携带完整的目的地址.虚电路表示例这可让他犯了难，施工现场距离项目部很远，没有车还真是不方便office,branchoffices(jurisdiction),riskmanagement,marketingmanagementsectorthroughsupervisionandinspectionfoundproblems,shouldbeassignedtheinvestigatorsarecorrectedinatimelymanner.27ththefifthchapterpenaltyunderanyofthefollowingacts,thentherelevantprovisionstopunishtheinvestigators,accordingtotheBank.Toconstituteacrimeshallbeinvestigatedforcriminalresponsibility:(A)onthebusinessthatarenotinvolvedintheinvestigation,issuedasurvey.(B)customercreditinformationarenotthoroughverification.(Iii)toparticipateincreditcustomersurveyisnotinplace,customersanddataisincomplete,untrue;heknowsbearacounterfeitedclientsissuingcredit.(D)doesnotprovideforduediligenceofcreditbusiness,pre-loaninvestigationform,concealingfactsorprovidingfalseinformationorshouldbefoundinanormalinvestigationfailedtodiscovertheriskfactors,leadtothereviewandapprovalpolicyerrors,loanrisk.(Five)onloanguaranteesofsurveynotinplace,notbyprovidesonarrived,andpledgerealforfieldverification,andassessment,andidentificationandregistration,notaccordingtoprovidesonguarantorofguaranteesqualificationandguaranteescapacityforsurveyverified,ledtoguaranteesloanlostauthenticity,andlegitimacy,andeffectivenessof;cycleloanbusinessintheofmortgage3数据报网络（提供无连接服务）①尽最大努力交付②路由器对于每个输入的数据包单独进行处理③路由表包含了目的地址和输出接口的对应关系④每个数据包必须包含完整的目的地址⑤来自相同源节点和目的节点的两数据报可能被转发到不同的接口，不保证顺序⑥对网络状况和目的主机状况一无所知，可能出现丢失路由表示例：4.数据报vs虚电路4.2路由选择算法（简称“选路”）：根据数据包中携带的目的地址，为数据包在网络中选择一条路径，以到达目的主机。路由器查找路由表，完成选路。选路到下一跳（NextHop，或输出接口），而不是完整路由转发：将数据从路由器的输入接口转移到相应的输出接口路由选择：根据路由表确定应转发到哪个输出接口的过程这可让他犯了难，施工现场距离项目部很远，没有车还真是不方便office,branchoffices(jurisdiction),riskmanagement,marketingmanagementsectorthroughsupervisionandinspectionfoundproblems,shouldbeassignedtheinvestigatorsarecorrectedinatimelymanner.27ththefifthchapterpenaltyunderanyofthefollowingacts,thentherelevantprovisionstopunishtheinvestigators,accordingtotheBank.Toconstituteacrimeshallbeinvestigatedforcriminalresponsibility:(A)onthebusinessthatarenotinvolvedintheinvestigation,issuedasurvey.(B)customercreditinformationarenotthoroughverification.(Iii)toparticipateincreditcustomersurveyisnotinplace,customersanddataisincomplete,untrue;heknowsbearacounterfeitedclientsissuingcredit.(D)doesnotprovideforduediligenceofcreditbusiness,pre-loaninvestigationform,concealingfactsorprovidingfalseinformationorshouldbefoundinanormalinvestigationfailedtodiscovertheriskfactors,leadtothereviewandapprovalpolicyerrors,loanrisk.(Five)onloanguaranteesofsurveynotinplace,notbyprovidesonarrived,andpledgerealforfieldverification,andassessment,andidentificationandregistration,notaccordingtoprovidesonguarantorofguaranteesqualificationandguaranteescapacityforsurveyverified,ledtoguaranteesloanlostauthenticity,andlegitimacy,andeffectivenessof;cycleloanbusinessintheofmortgage静态选路算法（非自适应选路算法）路由表预先设定（不考虑网络当前状况）路由表基本不变，一般不能保证是最佳路由。动态选路算法（自适应选路算法）根据当前网络的拓扑结构和负载，（周期性）动态，更新路由表。1.静态选路算法㈠固定路由表选路法：根据事先设置的静态路由表，查表选路。静态路由表的生成：Dijakstra算法算法原理1）定义一个集合N，包含所有最短路径已确定的节点，在初始时，该集合中只包含一个源节点（设为S）2）如果S和某个节点之间有一条边相连，距离就是该边上的权值；否则，距离值设为无穷大（∞）3）从集合N外的节点中选择一个和S距离最小的节点（设为T）加入集合4）重新计算S到其他集合N外的节点的距离，如果经过T的路径更短，则更新距离值5）重复3-4步，直到所有节点都加入集合N㈡洪泛法：路由器收到数据包后，向除了输入接口之外的所有接口转发缺点：一个数据包将产生大量的副本（copy）给网络增加大量负载优点：至少有一个副本将到达目的主机，健壮性强，至少有一个副本选择的是最优路由，所有的路由器