● 用路由器把一个网络分段，这样做的好处是___(61)___。
（61）A．网络中不再有广播通信，所有的数据都通过路由转发器转发
B．路由器比交换鸡更有效率
C．路由器可以对分组进行过滤
D．路由器可以减少传输延迟
● 划分虚拟局域网（VLAN）有多种方式，以下划分方式中，不正确的是___(62)___。
（62）A．基于交换机端口划分 B．基于网卡地址划分
C．基于用户名划分 D．基于网络曾地址划分
● 在距离矢量路由协议中，防止路由循环的技术是___(63)___。
（63）A．使用生成树协议删除回路
B．使用链路状态公告（LSA）发布网络的拓扑结构
C．利用水平分裂法阻止转发路由信息
D．利用最短通路优先算法计算最短通路
● 关于kerberos和PKI俩种认证协议的叙述中正确的是___(64)___，在使用kerberos认证时，首先向密钥分发中心发送初始票据___(65)___来请求会话票据，以便获取服务器提供的服务。
（64）A．kerberos 和PKI都是对称密钥
B．kerberos和PKI都是非对称密钥
C．kerberos是对称密钥 ，而PKI是非对称密钥
D．kerberos是非对称密钥，而PKI是对称密钥
（65）A．RSA B．TGT C．DES D．LSA
● when the system upon which a transport entity is running fails and subsequently reatarts, the ___(66)___ information of all active connections is lost. the affected connections become half-open, as the side that did not fail does not yet realize the promble.
The still active side of a half-open connections using a ___(67)___ timer. this timermeasures the time transport machine will continue to await an ___(68)___ of a transmitted segment after the segment has been retransmitted the maximum number of times. when the timer ___(69)___ ,the transport entity assumes that either the other transport entity or the intervening network has failed. as a result, the timer closes the connection, and signals an abnormal close to the TS user.
In the event that a transport entity fails and quickly restart, half-open connections can be teminated more quickly by the use of the RST segment. the failed side returns an RST I to every segment I that it receives. when the RST I reaches the other side, it must be checked for validity dased on the ___(70)___ number I, as the RST could be in response to an old segment .if the reset is valid,the transport entity performs an abnormal termination.
(66) A．data B．state C．signal D．control
(67) A．give-up B．abandon C．quit D．connection
(68) A．reset B．acknowledgment C．sequence D．synchroizer
(69) A．stops B．restarts C．expires D．abandons
(70) A．sequence B．acknowledgment C．connection D．message
● astute service providers realize that the continued support of legacy X.25 and asynchronous network elements using separate operations network is cost ___(71)___.for example, the maintenance of multiple networks can require additional staff. often, this staff must be trained on multiple vendor technologies, sometimes requiring parallel groups specializing in each ___(72)___ hence, additional maintenance procedures must be maintained and administrative records are ___(73)___ the duplication of trasport facilities to carry ___(74)___ network traffic is an inefficient use of resources and, not surprisingly, more technologies installed in a central office mean the necessity for more physical space, and an increase in power connections and power consumption. migration of these ___(75)___ network elements to IP-based DCns is alogical strategy .
(71) A．prohibitive B．feasible C．connective D．special
(72) A．line B．platform C．sever D．switch
(73) A．declined B．proliferated C．destroyed D．produced
(74) A．overlook B．overlie C．overlay D．overleap
(75) A．traditional B．dominancy C．redundancy D．legacy
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