dropbox/Computer-Network.html at master · gravitywp/dropbox · GitHub

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<?xml version="1.0" encoding="utf-8"?>
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en">
<head>
<!-- 2016-09-07 Wed 03:29 -->
<meta  http-equiv="Content-Type" content="text/html;charset=utf-8" />
<meta  name="viewport" content="width=device-width, initial-scale=1" />
<title></title>
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<meta  name="author" content="guozhen" />
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Copyright (C) 2012-2013 Free Software Foundation, Inc.

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<body>
<div id="content">
<div id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#orgheadline1">1. Router</a></li>
<li><a href="#orgheadline2">2. 协议划分</a></li>
</ul>
</div>
</div>
<p>
#+TITLE=Computer Network
</p>
<div id="outline-container-orgheadline1" class="outline-2">
<h2 id="orgheadline1"><span class="section-number-2">1</span> Router</h2>
<div class="outline-text-2" id="text-1">
<p>
路由器是一种计算机，但不是主机。是packet switching的关键构件。其任务是转发收到的分组。
</p>
<ul class="org-ul">
<li>分组转发技术
分组交换使用存储转发技术。通常我们把要发送的整块数据称为报文(message)。</li>
</ul>
</div>
</div>
<div id="outline-container-orgheadline2" class="outline-2">
<h2 id="orgheadline2"><span class="section-number-2">2</span> 协议划分</h2>
<div class="outline-text-2" id="text-2">
<ul class="org-ul">
<li>应用层
体系结构中的最高层，直接向用户进程提供服务。
应用层中的协议如: HTTP, SMTP, FTP</li>
<li>传输层
主要有一下两种协议:
<ul class="org-ul">
<li>TCP (Transmission Control Protocol)&#x2013;面向连接，数据传输的单位是报文段,能够提供可靠的交付。</li>
<li>UDP (User Datagram Protocol)&#x2013;无连接的，数据传输单位是用户数据报，不保证可靠的交付，(best-effort-delivery)</li>
</ul></li>
<li>网络层 network layer
负责为分组交换网上的主机提供通信服务。在发送数据时，网络层把运输层产生的报文段或用户数据封装成分组或包进行传送。在TCP/IP体系中，由于网络层
使用IP协议,因此分组也叫做IP数据报，或简称数据报。网络层中的另一个任务就是要选择合适的路由，是源主机运输层所传下来的分组，能够通过路由器找到
目的主机。
网络层的主要协议是无连接的IP(Internet Protocol)和许多路由选择协议。因此网络层又叫网技层或IP层。</li>
<li>数据链路层(data link layer)
两个主机间数据传输总是在一段一段的链路上传送的。连个相邻节点（主机和路由器之间或两个路由器之间）传送数据就是直接传送的(点对点)。这是就需要专门的链路层协议。
数据链路层将网络层中的数据。数据链路层将网络层交下来的IP数据报组装成帧(framing),在连个相邻节点间的链路上"透明"地传送帧(frame)中的数据。每一帧包括数据和必要
的控制信息(如同步信息,地址信息,差错控制等)。典型的帧长是几百字节到一千多字节。</li>
<li>物理层(physical layer)</li>
</ul>
</div>
</div>
</div>
<div id="postamble" class="status">
<p class="author">Author: guozhen</p>
<p class="date">Created: 2016-09-07 Wed 03:29</p>
<p class="validation"><a href="http://validator.w3.org/check?uri=referer">Validate</a></p>
</div>
</body>
</html>