软件水平考试（中级）网络工程师上午（基础知识）试题模拟试卷1

(16)

(14)

(15)

(13)

(11)

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 the defines(74)showing how the system will be operated, publishes the system and operation concept documents, 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 operations concept. Using structured or object-oriented analysis, the team specifies the software functions and algorithms needed to satisfy each detailed requirements.

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(6)

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 swiches, 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.

(5)

两个码子之间的海明距为(22)。码是由码子组成的集合，一个码的海明距离指的是(23)。若一个码要求检测3位错，则该码的海明距离应为，(24)。

(3)

若信号带宽为40Hz，理想信道可以达到的最大码元速率为(17)。若码元可以取8种离散值，则一个码元携带的信息量为(18)比特，此时，理想信道传输信号带宽为40Hz的数据速率为(19)。

(2)