单选题X.25网络的数据链路层使用LAPB的协议标准。在扩展模式下，该协议标准允许在收到应答前连续发送 (26) 帧数据。

单选题TCP软件可以提供 (15) 个不同的端口。

单选题对招标文件的响应存在非实质性的细微偏差的投标书，______。 A．不予淘汰，在订立合同前予以澄清、补正即可 B．不予淘汰，在评标结束前予以澄清、补正即可 C．不予淘汰，允许投标人重新报价 D．评标阶段予以淘汰

单选题在 Linux操作系统中，存放用户帐号加密口令的文件是（ ）

单选题某系统的进程状态转换如下图所示，图中1、2、3和4分别表示引起状态转换的不同原因，原因4表示{{U}}(7){{/U}}；一个进程状态转换会引起另一个进程状态转换的是{{U}}(8){{/U}}。

单选题在以太网中，最大传输单元(MTU)是______字节。 A．46 B．64 C．1500 D．1518

单选题关于Windows 2000服务器软件，以下哪些说法是正确的?( ) A．它提供了Windows 2000 Professional，以方便专业用户的操作 B．它不再使用域作为基本管理单位，以方便网络用户的漫游 C．它提供了活动目录服务，以方便网络用户查找 D．它使用全局组合本地组的划分方式，以方便用户对组进行管理

单选题在DHCP服务器配置过程中，可以把使用DHCP协议获取IP地址的主机划分为不同的类别进行管理，下面划分类别规则合理的是______。

单选题一个网络的地址为172.16.7.128/26，则该网络的广播地址是 （ ） 。

单选题假定一条线路每1/16s采样一次，每个可能的信号变化都运载3bit的信息，则传输速率是 (1) 。

单选题在Windows命令行窗口中进入nslookup交互工作方式，然后输入set type＝mx，这样的设置可以________。

单选题接收告警事件、分析相关信息、及时发现正在进行的攻击等事件的捕捉和报告操作是由管理代理通过 SNMP的 (46) 报文传输给管理进程的。

单选题在网络中分配 IP 地址可以采用静态地址或动态地址方案。下面关于两种地址分配方案的论述中错误的是（ ）。

单选题搭建试验平台、进行网络仿真是网络生命周期中______阶段的任务。

单选题图8-5给出了不同类型IPSec数据包的封装示意图。其中，(40)工作在隧道模式；(42)只支持报文源身份认证和数据完整性服务，不支持报文加密服务。

单选题A transport layer protocol usually has several responsibilities．One is to create a process-to-process communication；UDP uses (71) numbers to accomplish this．Another responsibility is to providecontrol mechanisms at the transport level．UDP does this task at a very minimal level．There is no flowcontrol mechanism and there is no (72) for received packet．UDP, however,does provide errorcontrol to some extent．If UDP detects an error in the received packet，it will silently drop it． The transport layer also provides a connection mechanism for the processes．The (73) must be able to send streams of data to the transport layer．It is the responsibility of the transport layer at (74) station to make the connection with the receiver,chop the stream into transportable units，numberthem，and send them one by one．It is the responsibility of the transport layer at the receiving end to waituntil all the different units belonging to the same process have arrived，check and pass those that are (75) flee，and deliver them to the receiving process as a stream．

单选题In the following essay, each blank has four choices. Choose the most suitable one from the four choices and write down in the answer sheet. The key to SNMP (71) is its simplicity. It has a small command set that does a good job of collecting information from (72) any network device. In a SNMP environment, (73) of the work is handled by the network management system. Devices that are being managed are not (74) with processing (75) that might affect their performance.