TCP协议为了实现可靠的服务，采用三次握手协议来建立连接。另外，其协议规定，在确认信息中捎带(24)的序号以减少通信量。

Kerberos was developed at (1) in 1998s．It was named after the three-headed watchdog in classical Greek mythology that guards the gates to Hades．The name is apt because Kerberos is a(2)process，depending on a thrid—party service called the(3)to verify one computer’S identity to another and to set up (4) for a secure connection between them．Basically，Kerberos works because each computer shares a secret with the KDC，which has two components：a Kerberos authentication server and a (5)server．If a KDC doesn’t know the requested target server，it refers the authentication transaction to(6)that does．Kerberos is a network(7)protocol that allows one computer to(8)its identity to another across an insecure network through an exchange of encrypted messages．Once identity is verified，kerberos provides the two computer with (9) for a secure communication session．Kerberos authenticates the identity and encrypts their communications through (10)．

Networks can be interconnected by different devices．In the physical layer，networks can be connected by(66)or Hubs, which just move the bits from one network to an identical net-work. One layer up we find bridgas and swiehes, which operate at data link layer. They can accept(67), examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two netwoks. If two networks have(68)network layer, the router may be able to translate between the packet formats. In the transport layer we find transport gateway, which can interface between the two transport connections. Finally, in the application layer, application gateways translate message(69). As an example, gateways between Internet e-mail and X.400 e-mail must(70) the e-mail message and change various header fields.

下列叙述中正确的是(23)。

以下关于VoIP的描述不正确的是(60)。

图1-1是一个软件项目的活动图，其中顶点表示项目里程碑，连接顶点的边表示包含的活动，边上的值表示完成活动所需要的时间，则关键路径长度为______。

以下安全协议中，用来实现安全电子邮件的仂、议是______。

在单指令流多数据流计算机(SIMD)中，各处理单元必须(1)。

Kerberos的设计目标不包括(51)。

以下给出的地址中，与地址218.16.0.19/28同属于一个子网的主机地址是(48)。

以下ACL语句中，含义为“允许172．1 68．0．0／24网段所有PC访问10．1．0．10中的FTP服务”的是__________。(2010年上半年试题)

某网络结构如下图所示。在Windows操作系统中，Serverl通过安装(1)组件创建Web站点。PCI的用户在浏览器地址栏中输入www.abc.com后无法获取响应页面，管理人员在Windows操作系统下可以使用(2)判断故障发生在网络A内还是网络A外。如果使用ping61．102．28．77命令对服务器Serverl进行测试，响应正常，则可能出现的问题是(3)。(2008年上半年试题)

正交调幅(QAM)编码是将载波信号的__________改变。

快速以太网100BAST-T所采用的媒体控制方式是(36)。100BAST-FX采用的编码方案是(37)。千兆以太网的最大帧长是(37)，最小帧长是(38)，它使用4对5类双绞线主要用于(40)。

在操作系统文件管理中，通常采用__________来组织和管理外存中的信息。(2010年下半年试题)

通过交换机连接的一组工作站(57)。

以下给出的地址中，不属于网络222．15．64．0／20的主机地址是__________。(2008年下半年试题)

网络管理系统的实现方式有(10)。

ARPAnet is a wide area network(WAN)．A network that connected Department of Defense research sites across(1)．Created in 1 969 with funding from the Advanced Research Projects Agency(ARPA)．Undergoing constant research and development in the early—to mid一1970s，ARPAnet(2)aS the test bed for the development of(3)(the protocols that make the Internet possible)．A major goal of the ARPAnet project was to increase the military’s command and control capability by enabling communication across a variety of physically (4)media，including satellites．An allied goal was to create a robust network：(5)withstanding outages，such as those that might result from a nuclear exchange．ARPAnet met these objectives，but it also (6) its creators：It was found in short order that most ARPAnet users (7) use the network for(8)，such as electronic mail and discussion groups．Initially，the ARPAnet was available only to government research institutes and to universities holding Department of Defense(DoD)research contracts．In 1 983，ARPAnet was(9)into a high—security military network(Milnet)and an ARPAnet that was recast as a research and development network．Although it formed the (10) of the Internet，it was decommissioned in 1 990．

RMON和SNMP的主要区别是__________。(2011年下半年试题)