●  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 network. One layer up we find bridges and switches, 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 networks, If two networks have  （68）  network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between 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.

试卷相关题目

• 1●  以下不属于中间件技术的是 （65） 。

  A.Java RMI

  B.CORBA

  C.DCOM

  D.Java Applet

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• 2●  将双绞线制作成交叉线（一端按EIA/TIA 568A线序，另一端按EIA/TIA 568B线序），该双绞线连接的两个设备可为 （64） 。

  A.网卡与网卡

  B.网卡与交换机

  C.网卡与集线器

  D.交换机的以太口与下一级交换机的UPLINK口

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• 3●  许多网络通信需要进行组播，以下选项中不采用组播协议的应用是 （62） 。在IPv4中把 （63） 类地址作为组播地址。

  A.VOD

  B.Netmeeting

  C.CSCW

  D.FTP

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• 4●  以太网100BASE-TX标准规定的传输介质是 （61） 。

  A.3类UTP

  B.5类UTP

  C.单模光纤

  D.多模光纤

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• 5●  在缺省配置的情况下，交换机的所有端口 （59） 。连接在不同交换机上的，属于同一VLAN的数据帧必须通过 （60） 传输。

  A.处于直通状态

  B.属于同一VLAN

  C.属于不同VLAN

  D.地址都相同

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• 6●  The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable  （71）  of the technical requirements for the software product.During the requirements definition phase, the requirements definition team uses an iterative process to expand a broad statement of the system requirements into a complete and detailed specification of each function that the software must perform and each  （72）  that it must meet.The starting point is usually a set of high-level requirements from the  （73）  that describe the project or problem.In either case, the requirements definition team formulates an overall concept for the system and then defines  （74）  showing how the system will be operated, publishes the system and operations concept document, and conducts a system concept review（SCR）.Following the SCR, the team derives  （75）  requirements for the system from the high level requirements and the system and operations concept. Using structured or object-oriented analysis, the team specifies the software functions and algorithms needed to satisfy each detailed requirement.

  A.function

  B.definition

  C.specification

  D.statement

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