HTFP是WWW的核心，它是一个(59)协议，当访问一个URL为http://www. ccidedu.com.cn/index.htm的网页时，浏览器首先向(60)请求解析http://www.ccidedu. com. cn的IP地址。获得解析后的IP地址后，浏览器通过(61)端口与服务器建立(62)连接。随后浏览器发送取文件命令(63)。服务器响应并将文件index.htm发送给浏览器，最后释放连接。

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Flow control is a function that prevents network congestion by ensuring that(71)do not overwhelm(72)with data. There are three commonly used methods for handling network congestion.(73)is used by network devices to temporarily store bursts of excess data in memory until they can be processed. (74)are used by receiving devices to help prevent their buffers from overflowing.(75)is a flow -control scheme in which the source device requires an acknowledgment from the destination after a certain number of packets have been transmitted.

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The purpose of the requirements definition phase is to produce a clear, complete, consistent, and testable (66) 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 (67) that it must meet. The starting point is usually a set of high-level requirements from the (68) that describe the project or problem.

 In either case, the requirements definition team formulates an overall concept for the system and the defines (69) 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 (70) requirements for the system from the highlevel 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.