【正文】 。小型機(jī)的反過(guò)來(lái)又可以連接到公司的主機(jī) ,它包含數(shù)據(jù)和程序都可接受。s mainframe, which contains data and programs accessible to all. 一個(gè)層次網(wǎng)絡(luò)是有用的在 集中組織。層次網(wǎng)絡(luò)允許各種電腦共享數(shù)據(jù)庫(kù)、處理能力和不同輸出設(shè)備。 Thus, the host at the top of the hierarchy could be a mainframe. The puters below the mainframe could be miniputers, and those below, microputers. The hierarc hical work allows various puters to share databases, processing power, and different output devices. 因此 ,主持人最高等級(jí)的可 以是一個(gè)主機(jī)。 The hierarchical work consists of several puters linked to a central host puter, just like a star work. However, these other puters are also hosts to other, smaller puters or to peripheral devices. (See Figure 921.) 層次網(wǎng)絡(luò)由多個(gè)計(jì)算機(jī)連接 到一個(gè)中央主機(jī)電腦 ,就像一個(gè)星形網(wǎng)絡(luò)。 A ring work is useful in a decentralized anization because it makes possible a distributed data processing system. That is,puters can perform processing tasks at their own dispersed locations,However, they also can share programs, data,and other resources with each other. 一個(gè)環(huán)網(wǎng)絡(luò)是有用的在一個(gè) 分散的組織 ,因?yàn)樗箍赡艿姆植际綌?shù)據(jù)處理系統(tǒng) 。這些大型機(jī)往往相當(dāng)獨(dú)立地運(yùn)作。用微型計(jì)算機(jī) ,戒指的安排是最常用的四種網(wǎng)絡(luò)。 沒(méi)有中央文件服務(wù)器或計(jì)算機(jī)。然而 ,一個(gè)總線(xiàn)網(wǎng)絡(luò)易于安裝和不昂貴的。這樣的安排是常見(jiàn)的共享數(shù)據(jù)存儲(chǔ)在不同的微型計(jì)算機(jī)。隨著信息形成適用于它。沒(méi)有主機(jī)。星是一種常見(jiàn)的拓?fù)浣Y(jié)構(gòu)為連接微機(jī)到主機(jī) ,允許訪問(wèn)一個(gè)組織的數(shù)據(jù)庫(kù)。s database. 一個(gè)特定的優(yōu)勢(shì)是 ,它星型 拓樸結(jié)構(gòu)可以用于支持分時(shí)系統(tǒng)。即 ,每個(gè)連接裝置 是問(wèn) (“調(diào)查 ”)是否有一個(gè)消息發(fā)送。 All munications pass through this central unit. Control is maintained by polling. That is, each connecting device is asked (polled) whether it has a message to send. Each device is then in turn allowed to send its message 所有通信通過(guò)這個(gè)中央單位 。 In a star work, a number of small puters or peripheral devices are linked to a central unit.(See Figure 918.) The central unit is the work hub and is typically a host puter or file server. 在一個(gè)星形網(wǎng)絡(luò) ,一些小型計(jì)算機(jī)或外圍設(shè)備被連接到一個(gè)中央單位。這樣的安排被稱(chēng)為網(wǎng)絡(luò)的拓?fù)浣Y(jié)構(gòu)。 CONFIGURATIONS A work can be arranged or configured in several different ways. This arrangement is called the work39。網(wǎng)絡(luò)配置描述物理安排網(wǎng)絡(luò)。 NETWORK ARCHITECTURE Network architecture describes how a work is arranged and how resources are coordinated and enpasses a variety of different work specifics, including work configurations and configurations describe the physical arrangement of the work. Network strategies define how information and resources are shared. 網(wǎng)絡(luò)體系結(jié)構(gòu)描述了一個(gè)網(wǎng) 絡(luò)安排和資源協(xié)調(diào)和共享。每個(gè) 包然后在互聯(lián)網(wǎng)上單獨(dú)發(fā)送 ,可能旅行不同的路線(xiàn)到一個(gè)共同的目標(biāo)。 Reformatting: Information sent or transmitted across the Inter usually travels through numerous interconnected works. Before the message is sent, it is reformatted or broken down into small parts called packets. Each packet is then sent separately over the Inter, possibly traveling different routes to one mon destination. At the receiving end, the packets are reassembled into the correct order. 重新格式化 :信息發(fā)送或通 過(guò)互聯(lián)網(wǎng)通常穿過(guò)眾多的互聯(lián)網(wǎng)絡(luò)。該系統(tǒng)使用一個(gè)域名服務(wù)器 (DNS),將基于文本的地址的 IP 地址。類(lèi)似于一個(gè)郵政服務(wù)使用地址送郵件 ,互聯(lián)網(wǎng)使用 IP 地址提供電子郵件和網(wǎng)站定位。本議定書(shū)的基本特點(diǎn)包括 :(1)確定發(fā)送和接收設(shè)備和 (2)重新格式化信息在互聯(lián)網(wǎng)上傳播。這些規(guī)則之間交換數(shù)據(jù)的計(jì)算機(jī)被稱(chēng)為協(xié)議。在接收端 ,包成正確的順序重新組裝。在消息被發(fā)送 ,這是重新格式化或分解成小的部分稱(chēng)為數(shù)據(jù)包。 (參見(jiàn)圖第 9 14個(gè) )。該系統(tǒng)使用一個(gè)域名服務(wù)器 (DNS),將基于文本 的地址的 IP 地址。類(lèi)似于一個(gè)郵政服務(wù)使用地址送郵件 ,互聯(lián)網(wǎng)使用 IP 地址提供電子郵件 和網(wǎng)站定位。本議定書(shū)的基本特點(diǎn)包括 :(1)確定發(fā)送和接收設(shè)備和 (2)重新格式化信息在互聯(lián)網(wǎng)上傳播。這些規(guī)則之間交換數(shù)據(jù)的計(jì)算機(jī)被稱(chēng)為協(xié)議。它能夠有效 滿(mǎn)足 今天大多數(shù)的通信需求 ,包括傳 輸高質(zhì)量的音頻和視頻。s munication needs, including transmitting highquality audio and video. Speeds are typically mbps, although much higher speeds are possible. “廣播 寬帶是用于大容量傳輸?shù)膸?。不像聲音帶和寬帶?中型帶寬通常不是私人使用的 。典型的速度是 56 至 96 kbps。微型計(jì)算機(jī)與標(biāo)準(zhǔn)調(diào)制解調(diào)器和撥號(hào)服務(wù)使用這個(gè)帶寬。 目前， 有三個(gè)類(lèi)別的帶寬。傳輸文本文檔 ,小帶寬可以接受 。 BANDWIDTH Bandwidth is a measurement of the width or capacity of the munication channel. Effectively, it means how much information can move across the munication channel in a given amount of time. For example, to transmit text documents, a slow bandwidth would be acceptable. However, to effectively transmit video and audio, a wider bandwidth is required. There are three categories of bandwidth. 帶寬是一個(gè)測(cè)量的寬度或容量的通信通道。 DATA TRANSMISSION Several factors affect how data is transmitted. These factors include bandwidth and protocols. 有 幾個(gè)因素影響數(shù)據(jù)傳輸 速度 。目前 ，此服務(wù)僅限于特定的大都市地區(qū) 開(kāi)放 。使用 3 g 蜂窩網(wǎng)絡(luò) ,設(shè)備 ,如手機(jī)和筆記本電腦 的 下載 速度可以維持在 400 至 700 kbps。而 老 舊 的衛(wèi)星服務(wù)不能上傳 (上行 )或?qū)?shù)據(jù)發(fā)送給衛(wèi)星 ,所以 不得不依靠緩慢的撥號(hào)連接 ,更新的雙向衛(wèi)星連接現(xiàn)在可用。雖然電纜在美國(guó) 家庭覆蓋率達(dá)到 90%。 此項(xiàng)技術(shù)仍 使用在大多數(shù)地區(qū)。 Digital subscriber line (DSL) uses existing telephone lines to provide highspeed connections. ADSL (asymmetric digital subscriber line) is one of the most widely used types of DSL. This technology is widely available in most areas. 數(shù)字用戶(hù)線(xiàn) (DSL)使用現(xiàn)有電話(huà)線(xiàn)提供高速連接。 These include DSL, cable modems, satellite,and cellular. For a parison of typical user connection costs and speeds,see figure 913 這些包括 DSL、電纜調(diào)制解調(diào)器、衛(wèi)星 ,和細(xì)胞。 While the special highspeed lines are too costly for most individuals,there are affordable connections that provide sig