论坛站务软件水平考试华为认证计算机等级PMP认证思科认证Photoshop3DMAX编程语言移动开发系统运维产品运营淘宝营销办公软件Ps修图云计算大数据摄影就业

<p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　为帮助考生备考2022年软考<span style="margin: 0px; padding: 0px; box-sizing: border-box; color: rgb(255, 0, 0);"><span style="margin: 0px; padding: 0px; box-sizing: border-box; font-weight: 700;"><a href="http://www.kokojia.com/package-203.html" target="_blank" style="margin: 0px; padding: 0px; box-sizing: border-box; cursor: pointer; text-decoration-line: none; color: rgb(51, 122, 183); background-color: transparent;"><span style="margin: 0px; padding: 0px; box-sizing: border-box; color: rgb(255, 0, 0);">网络工程师考试</span></a></span></span>，课课家小编为大家整理了2022年网络工程师考试知识点(四十一)：IP数据报格式，相信对大家备考复习会有帮助。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　很多考生在备考2022年网络工程师考试，课课家小编为大家整理了2022年网络工程师考试知识点(四十一)：IP数据报格式，供考生备考复习。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　一个IP数据报时由首部和数据两部分所组成的。首部的前一部分为固定长度，共20字节。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　常考的几个字段：</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(1)版本：占4位，指的是IP协议的版本。目前广泛使用的IP协议版本号为4。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(2)首部长度，典型的IP数据报首部长度是20字节。那么首部长度这个字段的值就是5。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(3)区分服务：默认情况下一直没有使用过，是用在QOS中。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(4)总长度：总长度指首部和数据之和的长度，超过下层MTU值的时候，必须分片，其中以太网的MTU为1500字节。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(5)标识：相同的标识字段的值使分片后的各数据报片最后能正确地重装成为原来的数据报。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(6)标志：标志字段中的最低位为MF MF=1表示后面“还有分片”的数据报。MF=0表示这已是若干数据报片中的最后一个。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　标志字段中间的一位记为DF，意思是“不能分片”。只有当DF=0时，才允许分片。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(7)片偏移：分片在原分组中的相对位置片，偏移以8个字节为偏移单位。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(8)生存时间：表明数据报在网络中的生命。路由器在转发数据报之前就把TTL值减1。值减小到零，就丢弃这个数据报，不再转发。数据报在网络中能经过的路由器的理论最大数值是255。是由发送端设置这个字段。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(9)协议：目的主机的IP层知道应将数据部分上交给哪个上层协议。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(10)首部校验和(11)源地址(12)目的地址</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(13)选项字段用来支持其他功能。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);">　　(14)首部不是4字节整数倍的时候，就用全0的填充字段补齐成为4字节的整数倍。</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; line-height: 26px; color: rgb(51, 51, 51); white-space: normal; box-sizing: border-box; font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; background-color: rgb(255, 255, 255);">　　&gt;&gt;&gt;&gt;&gt;&gt;点击进入<span style="margin: 0px; padding: 0px; box-sizing: border-box; color: rgb(255, 0, 0);"><span style="margin: 0px; padding: 0px; box-sizing: border-box; font-weight: 700;"><a href="http://www.kokojia.com/activity-ruankao.html" target="_blank" style="margin: 0px; padding: 0px; cursor: pointer; text-decoration-line: none; color: rgb(51, 122, 183); box-sizing: border-box; background-color: transparent;"><span style="margin: 0px; padding: 0px; box-sizing: border-box; color: rgb(255, 0, 0);">软考报名专题</span></a></span></span></p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; line-height: 26px; color: rgb(51, 51, 51); white-space: normal; box-sizing: border-box; font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; background-color: rgb(255, 255, 255);">&nbsp;</p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; line-height: 26px; color: rgb(51, 51, 51); white-space: normal; box-sizing: border-box; font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; background-color: rgb(255, 255, 255);"><span style="margin: 0px; padding: 0px; box-sizing: border-box; color: rgb(255, 0, 0);"><span style="margin: 0px; padding: 0px; box-sizing: border-box; font-weight: 700;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;"><span style="margin: 0px; padding: 0px; box-sizing: border-box;">　　相关推荐：<a href="http://bbs.kokojia.com/ruankao/89368/" target="_blank" style="margin: 0px; padding: 0px; cursor: pointer; color: rgb(0, 174, 239);">2022年网络工程师考试知识点汇总</a></span></span></span></span></span></span></span></span></span></span></span></span></p><p style="margin-top: 0px; margin-bottom: 10px; padding: 0px; box-sizing: border-box; color: rgb(51, 51, 51); font-family: &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; white-space: normal; background-color: rgb(255, 255, 255);"><br/></p>

论坛站务软件水平考试华为认证计算机等级PMP认证思科认证Photoshop3DMAX编程语言移动开发系统运维产品运营淘宝营销办公软件Ps修图云计算大数据摄影就业