完成计算机网络的图片webp替换
continuous-integration/drone/push Build is passing
Details
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@ -56,14 +56,14 @@ date: 2023-07-27T14:50:10+08:00
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* UDP没有拥塞控制,有利于实时应用(视频,语音)
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* UDP分组首部开销小,TCP有20B的首部开销,UDP仅有8B的开销
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* UDP是面向报文的,报文是UDP数据报处理的最小单位
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![](../../images/408/《计网》传输层/UDP协议.png)
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![](https://lychee.inksoul.top/uploads/original/d7/b7/a996e0f29f9b47e71e5445646933.webp)
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* 报文太长,UDP把报文交给IP层后,会导致分片
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* 报文太短,UDP把它交给IP层后,会使IP数据报的首部相对长度太大
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* 两者都会减低IP层的效率
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### 首部格式
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* ![](../../images/408/《计网》传输层/UDP首部格式.png)
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* ![](https://lychee.inksoul.top/uploads/original/f5/06/16a146c2069707d88758d0498950.webp)
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* 用户数据报UDP有两个字段:数据字段和首部字段
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* 首部字段只有8个字节,由四个字段组成,每个字段长度都是两个字节
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* 源端口:不是必须的,只有在需要对方回信时选用,不需要时可用全0
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@ -82,13 +82,13 @@ date: 2023-07-27T14:50:10+08:00
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* UDP校验和校验出UDP数据报是错误的,可以丢弃,也可以交付给上层,但是要附上错误报告
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* UDP校验和提供差错检测功能,在计算校验和时,要在UDP用户数据报之前增加12字节的伪首部
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* 伪首部既不向下传送也不向上递交,只是为了计算校验和
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* ![](../../images/408/《计网》传输层/UDP校验1.png)
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* ![](https://lychee.inksoul.top/uploads/original/e0/59/f7cde06c7a529e79cd323bc9cc87.webp)
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* 各字段内容
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* 源IP地址和目的IP地址:和IP数据一样,各占4个字节
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* 伪首部第3个字段是全零
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* 协议字段:UDP协议的协议字段值是17
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* UDP长度:UDP用户数据报长度,首部长度和数据部分长度之和
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* ![](../../images/408/《计网》传输层/UDP校验2.png)
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* ![](https://lychee.inksoul.top/uploads/original/53/5a/3eca4dceadbaddf40ed0479d2e25.webp)
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* 校验和过程
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* 将校验和字段置位0
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* 将伪首部和UDP用户数据报(首部和数据部分)看成是以16位为单位的二进制组成,依次进程二进制反码求和
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@ -112,14 +112,14 @@ date: 2023-07-27T14:50:10+08:00
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### TCP报文段
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![](../../images/408/《计网》传输层/TCP报文段1.png)
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![](https://lychee.inksoul.top/uploads/original/8e/13/949c8e19bca388a8749af4acae17.webp)
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* 一个TCP报文段 = 首部 + 数据部分
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* 首部的前20个字节是固定的
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* 后面有4n字节是根据需要而增加的选项
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* TCP首部的最小字节是20字节
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![](../../images/408/《计网》传输层/TCP报文段2.png)
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![](https://lychee.inksoul.top/uploads/original/90/80/17d149807692aa9bf116bd42af0e.webp)
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* 源端口和目的端口
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* TCP分用功能的实现
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@ -159,7 +159,7 @@ date: 2023-07-27T14:50:10+08:00
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### TCP连接(三次握手)
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![](../../images/408/《计网》传输层/TCP连接(三次握手).png)
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![](https://lychee.inksoul.top/uploads/original/c4/82/cbb6396ac649f4cd8b24e959d7e5.webp)
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* 第一次握手
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* 客户端向服务端发送请求,首部同步位SYN = 1,选择一个初始序号seq = x
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@ -179,7 +179,7 @@ date: 2023-07-27T14:50:10+08:00
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### TCP连接释放(四次握手)
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![](../../images/408/《计网》传输层/TCP连接(三次握手).png)
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![](https://lychee.inksoul.top/uploads/original/24/6a/1db75e1bf939add7dadd5515a6f9.webp)
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* 第一次握手
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* 客户端向服务端发出连接释放报文段->停止发送数据,主动关闭连接
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@ -242,16 +242,16 @@ date: 2023-07-27T14:50:10+08:00
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* 拥塞控制是指防止过多的数据注入网络,保证网络中的路由器或链路不致过载
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* 拥塞往往表现为通信时延的增加
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* 慢开始
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* ![](../../images/408/《计网》传输层/慢开始.png)
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* ![](https://lychee.inksoul.top/uploads/original/bc/2a/5d4c136424bb61130ecfc4843fa0.webp)
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* cwnd < ssthresh时,使用慢开始算法
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* 在达到慢开始门限ssthresh前,cwnd成线性增长
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* 拥塞避免
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* ![](../../images/408/《计网》传输层/拥塞避免.png)
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* ![](https://lychee.inksoul.top/uploads/original/fb/41/3df2bc1dbbc566bfb1728ec687aa.webp)
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* cwnd > ssthresh时,使用拥塞避免算法
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* cwnd每次增加1
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* 出现乘法减小时,ssthresh设置为当前cwnd的一半,cwnd设置为1,然后重新慢开始
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* 快重传/快恢复
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* ![](../../images/408/《计网》传输层/快重传.png)
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* ![](https://lychee.inksoul.top/uploads/original/67/f0/63f75c7dd5c8f427e782b80f67f5.webp)
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* 快重传
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* 当发送方连续收到3个重复的ack报文时,直接重传对方尚未收到的报文段
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* 不必等待那个报文段设置的重传计时器超时
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@ -6,11 +6,11 @@ date: 2023-07-28T14:35:45+08:00
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## 各报文常考内容
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![](../../images/408/《计网》大题/各报文常考内容.jpg)
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![](https://lychee.inksoul.top/uploads/medium/b3/d3/0070074ed8e21a622071de7fc6e0.webp)
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## 大题
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![](../../images/408/《计网》大题/大题1.jpg)
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![](https://lychee.inksoul.top/uploads/medium/99/99/538f2c27a80f309dcc6d6ce56e30.webp)
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(1)
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@ -46,7 +46,7 @@ u = $\frac{发送数据的时间}{从开始发送第一帧到收到第一个确
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---
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![](../../images/408/《计网》大题/大题2.jpg)
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![](https://lychee.inksoul.top/uploads/original/24/eb/7239b01e91d265632d9a8c8dc195.webp)
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(1)
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@ -66,7 +66,7 @@ u = $\frac{发送数据的时间}{从开始发送第一帧到收到第一个确
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---
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![](../../images/408/《计网》大题/大题3.jpg)
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![](https://lychee.inksoul.top/uploads/original/bf/04/3a3bfd9f282d6d92abc49620017c.webp)
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(1)
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@ -98,7 +98,7 @@ $2^7 = 128$ =>主机号占7位
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---
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![](../../images/408/《计网》大题/大题4.jpg)
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![](https://lychee.inksoul.top/uploads/original/d7/1a/0c01bacd344aec4b7c3d35742ff5.webp)
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(1)
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@ -123,7 +123,7 @@ $2^7 = 128$ =>主机号占7位
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---
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![](../../images/408/《计网》大题/大题5.jpg)
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![](https://lychee.inksoul.top/uploads/original/61/78/d4dc1370e36f8318d23029017ead.webp)
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(1)
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@ -146,7 +146,7 @@ R2转发P的源IP地址203.10.2.6,目的IP地址192.168.1.2
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---
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![](../../images/408/《计网》大题/大题6.jpg)
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![](https://lychee.inksoul.top/uploads/original/90/da/6538113f7e421feab16a30db0500.webp)
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(1)
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@ -167,7 +167,7 @@ R1,R2属于不同的自治系统,使用边界网关协议(BGP或BGP4)交
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---
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![](../../images/408/《计网》大题/大题7.jpg)
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![](https://lychee.inksoul.top/uploads/medium/85/aa/0abab959b630b44e22bda12b063f.webp)
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(1)
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@ -193,7 +193,7 @@ metric为10
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---
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![](../../images/408/《计网》大题/大题8.jpg)
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![](https://lychee.inksoul.top/uploads/original/f8/6b/9274732756d87870f5a9cf48496a.webp)
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(1)
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@ -219,7 +219,7 @@ R需提供NAT服务(网络地址转换服务)
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---
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![](../../images/408/《计网》大题/大题9.jpg)
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![](https://lychee.inksoul.top/uploads/medium/c3/2e/71b4f8722981822e621d40169583.webp)
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(1)
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@ -267,7 +267,7 @@ STTL = 40H = 64
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---
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![](../../images/408/《计网》大题/大题10.jpg)
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![](https://lychee.inksoul.top/uploads/medium/45/1f/29265e8b6d0cfa463b34dbd06a63.webp)
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(1)
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@ -289,7 +289,7 @@ SYN = 1,ACK =1,确认序号 =101
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---
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![](../../images/408/《计网》大题/大题11.jpg)
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![](https://lychee.inksoul.top/uploads/medium/1b/b4/066a05604dbffb9d5d358014d0d2.webp)
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(1)
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@ -322,7 +322,7 @@ IP数据报每经过一个路由器,TTL长度减1,并重新计算首部验
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---
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![](../../images/408/《计网》大题/大题12.jpg)
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![](https://lychee.inksoul.top/uploads/original/41/5b/b21a8f16f63ff6bdfa640bd5f6db.webp)
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(1)
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@ -16,7 +16,7 @@ date: 2023-07-27T19:15:08+08:00
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### 客户/服务器模型
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![](../../images/408/《计网》应用层/客户服务器模型.png)
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![](https://lychee.inksoul.top/uploads/original/4f/cc/3c80f8fa437cef1ad7ff67b740d5.webp)
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* 主要特点
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* 客户是服务请求方,服务器是服务提供方
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@ -36,7 +36,7 @@ date: 2023-07-27T19:15:08+08:00
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### P2P模型
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![](../../images/408/《计网》应用层/P2P模型.png)
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![](https://lychee.inksoul.top/uploads/original/4d/42/0acd65894457972eea621839a17a.webp)
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* 主要特点
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* 显著特点:对等节点之间有直接通信能力
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@ -56,13 +56,13 @@ date: 2023-07-27T19:15:08+08:00
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### DNS组成部分
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* 层次域名空间
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* ![](../../images/408/《计网》应用层/层次域名空间.png)
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* ![](https://lychee.inksoul.top/uploads/original/8f/21/866d6ac956e7c7b23bcaa8fa1a77.webp)
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* 顶级域名
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* 二级域名
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* 三级域名
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* 多个标号组成的完整域名总共不超过255个字符
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* 域名服务器
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* ![](../../images/408/《计网》应用层/域名服务器.png)
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* ![](https://lychee.inksoul.top/uploads/original/56/a3/8f52efed3d99185b0d1869fb7c71.webp)
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* 种类
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* 根域名服务器(.)
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* 顶级域名服务器
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@ -72,10 +72,10 @@ date: 2023-07-27T19:15:08+08:00
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* 域名服务器被设计为一种联机的分布式数据库系统,采用C/S模型
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* 域名解析过程
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* 递归查询
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* ![](../../images/408/《计网》应用层/递归查询.png)
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* ![](https://lychee.inksoul.top/uploads/original/e8/f0/719b6864b5231cf6043faab5e5ca.webp)
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* 本机向本地域名服务器的查询是递归查询
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* 递归迭代查询
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* ![](../../images/408/《计网》应用层/递归迭代查询.png)
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* ![](https://lychee.inksoul.top/uploads/original/29/65/2526cd605005a19ad49d63957884.webp)
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* 本地域名服务器向根域名服务器的查询是迭代查询
|
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* 流程
|
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* 主机m.xyz.com先向其本地域名服务器dns.xyz.com进行递归查询
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@ -123,7 +123,7 @@ date: 2023-07-27T19:15:08+08:00
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* 使协议更加简单和容易实现
|
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* 在传输文件的时候可以利用控制连接对文件的传输进行控制(如用户可以在文件传输过程中发生请求中止服务)
|
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|
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![](../../images/408/《计网》应用层/FTP工作时用到的TCP连接.png)
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![](https://lychee.inksoul.top/uploads/original/58/89/7854279692d13141a7406def5053.webp)
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* 控制连接
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* 作用
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@ -158,7 +158,7 @@ date: 2023-07-27T19:15:08+08:00
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* 邮件服务器,用来发送和接收邮件
|
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* 邮件发送协议SMTP【类似Push】和读取协议pop3【类似Pull】
|
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* 发送接收过程
|
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* ![](../../images/408/《计网》应用层/电子邮件发送接收过程.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/7d/a5/d2c88b33a0949839d90b6ba5d788.webp)
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|
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### 电子邮件格式
|
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@ -205,7 +205,7 @@ date: 2023-07-27T19:15:08+08:00
|
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|
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### Cookie
|
||||
|
||||
![](../../images/408/《计网》应用层/Cookie.png)
|
||||
![](https://lychee.inksoul.top/uploads/original/2b/73/4b91da8b45cc3ea7d2d3217dcc88.webp)
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|
||||
* Cookie是网站为了辨别用户身份,进行会话跟踪而存储在客户端上的数据
|
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* Cookie的组成
|
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@ -216,7 +216,7 @@ date: 2023-07-27T19:15:08+08:00
|
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|
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### HTTP操作过程
|
||||
|
||||
![](../../images/408/《计网》应用层/HTTP操作过程.jpg)
|
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![](https://lychee.inksoul.top/uploads/original/f7/0c/2b9ab4673c17f28798b6ff514fb7.webp)
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|
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* 浏览器分析链接指向页面的URL
|
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* 浏览器向DNS请求解析网址的IP地址
|
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@ -230,13 +230,13 @@ date: 2023-07-27T19:15:08+08:00
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### 持久连接和非持久连接
|
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|
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* 非持久连接
|
||||
* ![](../../images/408/《计网》应用层/非持久连接.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/50/81/acc5fb3142fa634d1d32bf15940b.webp)
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* 传输时间
|
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* 文档传输时间 + 两倍的往返时间RTT
|
||||
* connection状态
|
||||
* 标志为close,说明是非持久连接
|
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* 持久连接
|
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* ![](../../images/408/《计网》应用层/持久连接.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/7f/08/9650ad648fb8c0a56ced39405745.webp)
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* 传输时间
|
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* 共经历1个RTT延迟
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* connection状态
|
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@ -245,7 +245,7 @@ date: 2023-07-27T19:15:08+08:00
|
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|
||||
### HTTP的报文结构
|
||||
|
||||
![](../../images/408/《计网》应用层/HTTP的报文结构.jpg)
|
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![](https://lychee.inksoul.top/uploads/original/e6/a4/5bdbd6972015122d4258528f68fd.webp)
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||||
* 两类HTTP报文
|
||||
* 请求报文
|
||||
|
@ -260,4 +260,4 @@ date: 2023-07-27T19:15:08+08:00
|
|||
* POST【上传信息】
|
||||
* CONNECT【代理服务器】
|
||||
* 实例
|
||||
* ![](../../images/408/《计网》应用层/HTTP的报文结构实例.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/f9/49/fa827070c2645a6c19037b2b2bd7.webp)
|
|
@ -66,9 +66,9 @@ date: 2023-07-25T19:25:31+08:00
|
|||
* 计算比较复杂,但非常易于用硬件实现,因此被广泛应用于数据链路层
|
||||
* CRC具有纠错能力,但数据链路层只使用了他的检错功能,检测到帧出错直接丢弃
|
||||
* 计算举例
|
||||
* ![](../../images/408/《计网》数据链路层/CRC计算举例1.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/CRC计算举例2.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/CRC计算举例3.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/e1/50/4a84d2d0b7abb9cc1f79f90b1a68.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/e4/30/dc0f4a76b9f84824e5ced91c905b.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/f9/a0/16b20651d42998bbe4fe5090e19a.webp)
|
||||
* 纠错编码分类
|
||||
* 海明码
|
||||
* 实现原理
|
||||
|
@ -102,7 +102,7 @@ date: 2023-07-25T19:25:31+08:00
|
|||
|
||||
### 停止等待协议SW
|
||||
|
||||
![](../../images/408/《计网》数据链路层/停止-等待协议.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/16/ab/a5febf909cb8c63871668a7d7e6e.webp)
|
||||
|
||||
* 接收端检测到数据分组有误码时,将器丢弃并等待发送方的超时重传
|
||||
* 对于误码率较高的点对点链路,为使发送方尽快重传,可给发送方发生NAK(拒绝)分组
|
||||
|
@ -115,42 +115,42 @@ date: 2023-07-25T19:25:31+08:00
|
|||
* 超时计时器设置的重传时间一般略大于从发送方到接收方的平均往返时间
|
||||
* 在数据链路层点对点的往返时间好确认,重传时间好确认
|
||||
* 在运输层,由于端到端往返时间不确定,重传时间不好确认
|
||||
* ![](../../images/408/《计网》数据链路层/停止-等待协议的信道利用率.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/c5/fb/b3f8fc4cdac66c0c9d470ed30d83.webp)
|
||||
* 当往返时延RTT远大于数据帧发送时延TD时【如卫星链路】,信道利用率非常低
|
||||
* 若出现重传,则对于传送有用的数据信息来说,信道利用率还要降低
|
||||
* 为了克服该协议信道利用率低的缺点,可以使用GBN和SR协议
|
||||
* 这些协议也叫做自动重传请求ARQ
|
||||
* ARQ通过接收方请求发送方重传出错的数据帧来恢复出错的帧
|
||||
* 例题
|
||||
* ![](../../images/408/《计网》数据链路层/例题停止-等待协议.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/例题2停止-等待协议.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/3f/6a/bda6b308f82a6c99911955cbfa4d.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/42/9a/a68f65a345c60208709248827119.webp)
|
||||
|
||||
|
||||
### 回退N帧协议GBN【Go-back-N】
|
||||
|
||||
![](../../images/408/《计网》数据链路层/回退N帧协议.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/f3/9a/9b2b31a977e698f6af764b5a6665.webp)
|
||||
|
||||
![](../../images/408/《计网》数据链路层/详细回退N帧协议.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/b8/cc/3dadc9224db21ea05922af0f409b.webp)
|
||||
|
||||
* 例题
|
||||
* ![](../../images/408/《计网》数据链路层/例题1回退N帧协议.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/例题2回退N帧协议.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/例题3回退N帧协议.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/例题4回退N帧协议.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/84/90/8fed83384d764587e1a136528829.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/44/59/26ccbb8e86b2d45570cbe1acda86.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/e1/ee/2010d158835672f493cca837cc33.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/54/98/c3560327af2eea9bc7eb2508de3f.webp)
|
||||
|
||||
|
||||
### 选择重传协议SR
|
||||
|
||||
![](../../images/408/《计网》数据链路层/选择重传协议.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/f4/98/0b8355babe7447cb8336d4ded982.webp)
|
||||
|
||||
![](../../images/408/《计网》数据链路层/详细选择重传协议.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/94/1a/0eb7fc34d9635788797f691603e9.webp)
|
||||
|
||||
* 例题
|
||||
* ![](../../images/408/《计网》数据链路层/例题选择重传协议.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/6e/93/eabfa5bb82a8b51ac78fe9db366e.webp)
|
||||
|
||||
## 点对点协议PPP
|
||||
|
||||
![](../../images/408/《计网》数据链路层/点对点协议PPP.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/59/96/f39be426959a40528b6d8b6d4281.webp)
|
||||
|
||||
* PPP协议的组成
|
||||
* 链路控制协议LCP
|
||||
|
@ -173,14 +173,14 @@ date: 2023-07-25T19:25:31+08:00
|
|||
* 共享信道要着重考虑的一个问题就是如何协调多个发送和接受站点对一个共享传输媒体的占用,即MAC(Medium Access Control)
|
||||
* MAC的内容就是,采取一定的措施,使得两对结点之间的通信不会发生互相干扰的情况
|
||||
* 分类
|
||||
* ![](../../images/408/《计网》数据链路层/媒体接入控制.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/20/78/65cbdee06e930f96b2711f75bece.webp)
|
||||
* 要点
|
||||
* 随着技术的发展,交换技术的成熟和成本的减低,具有更高性能的使用点对点链路和链路层交换机的交换式局域网在有线领域已完全取代了共享式局域网,但由于无线信道的广播特性,无线局域网仍然使用的是共享媒体技术
|
||||
|
||||
## 静态划分信道
|
||||
|
||||
* 信道复用
|
||||
* ![](../../images/408/《计网》数据链路层/信道复用.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/73/16/8ff4265edc826be2cea399f42eaa.webp)
|
||||
* 复用是通信技术中的一个重要概念
|
||||
* 复用就是通过一条物理线路同时传输多路用户的信号
|
||||
* 当网络中传输媒体的传输容量大于多条单一信道传输的总通信量时
|
||||
|
@ -190,7 +190,7 @@ date: 2023-07-25T19:25:31+08:00
|
|||
|
||||
#### 频分多路复用FDM
|
||||
|
||||
![](../../images/408/《计网》数据链路层/频分多路复用.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/7b/4c/9739935f5d935ba1e996447c7cd8.webp)
|
||||
|
||||
* FDM的所有用户同时占用不同的频带资源并行通信
|
||||
* FDM和TDM的比较
|
||||
|
@ -201,7 +201,7 @@ date: 2023-07-25T19:25:31+08:00
|
|||
|
||||
#### 时分多路复用TDM
|
||||
|
||||
![](../../images/408/《计网》数据链路层/时分多路复用.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/b5/2e/1cb628ffceae5058c5fa8af8a0dc.webp)
|
||||
|
||||
* TDM的所有用户在不同的时间占用同样的频带宽度
|
||||
* TDM介质的位速率大于单个信号的位速率
|
||||
|
@ -211,7 +211,7 @@ date: 2023-07-25T19:25:31+08:00
|
|||
|
||||
#### 波分多路复用WDM
|
||||
|
||||
![](../../images/408/《计网》数据链路层/波分多路复用.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/27/a1/358339aadc75b657ef89a4f11a10.webp)
|
||||
|
||||
#### 超分多路复用CDM
|
||||
|
||||
|
@ -235,11 +235,11 @@ date: 2023-07-25T19:25:31+08:00
|
|||
* $S \cdot S = l$
|
||||
* $S \cdot \bar{S} = -l$
|
||||
* 例题
|
||||
* ![](../../images/408/《计网》数据链路层/例题1码分多路复用.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/例题2码分多路复用.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/例题3码分多路复用.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/例题4码分多路复用.jpg)
|
||||
* ![](../../images/408/《计网》数据链路层/例题5码分多路复用.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/72/e4/67da30382a6b64331c42a3405b7b.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/b7/5c/833ba6e564cd16f79e690e89e98a.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/64/96/c44f84b0e0d4fdda468ed0caa873.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/1d/92/f767d8e8201d68a4aa2d2e3a9b69.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/2c/1e/adc8e1459aba04c9516865ad2ee7.webp)
|
||||
|
||||
### 随机接入协议分类
|
||||
|
||||
|
@ -273,74 +273,74 @@ date: 2023-07-25T19:25:31+08:00
|
|||
|
||||
##### 多址接入MA、碰撞检测CD、载波监听CS的概念
|
||||
|
||||
![](../../images/408/《计网》数据链路层/多址接入MA.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/8d/9e/f2e540047270721f54064f19fe4e.webp)
|
||||
|
||||
* 不适用于无线网络
|
||||
|
||||
##### 征用期(碰撞期)
|
||||
|
||||
![](../../images/408/《计网》数据链路层/征用期(碰撞期.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/9f/93/49ca73e115cc370be42016cae9d5.webp)
|
||||
|
||||
##### 最大帧长
|
||||
|
||||
【首部+尾部+数据载荷最小开始=64,即最小帧长】
|
||||
|
||||
![](../../images/408/《计网》数据链路层/最大帧长.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/7f/83/89ffaafec724bd47a7ea438580ae.webp)
|
||||
|
||||
##### 信道利用率
|
||||
|
||||
![](../../images/408/《计网》数据链路层/信道利用率.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/f1/57/05dbc1cb5ed55835439da76d925f.webp)
|
||||
|
||||
* 信号传播延迟趋于0时,信道利用率接近100%
|
||||
|
||||
##### MA、CD、CS的协作
|
||||
|
||||
![](../../images/408/《计网》数据链路层/MA,CD,CS的协作.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/2b/42/c838e22ff5686182ab5d8516db29.webp)
|
||||
|
||||
##### 最小帧长
|
||||
|
||||
![](../../images/408/《计网》数据链路层/最小帧长.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/03/cd/3bb545456c021f497edd1533a286.webp)
|
||||
|
||||
##### 截断二进制的指数退避算法
|
||||
|
||||
![](../../images/408/《计网》数据链路层/截断二进制指数退避算法.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/40/ad/6cf10c0765a94027e5c365d914e9.webp)
|
||||
|
||||
* 考虑到了网络负载对冲突的影响
|
||||
|
||||
##### 帧发送流程
|
||||
|
||||
![](../../images/408/《计网》数据链路层/帧发送流程.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/64/9f/a7c9c0b023901afa43318b035a1d.webp)
|
||||
|
||||
|
||||
#### 无线局域网使用的协议【CSMA/CA】
|
||||
|
||||
##### CSMA/CA为什么不能用于无线网?
|
||||
|
||||
![](../../images/408/《计网》数据链路层/CSMACA为什么不能用于无线网.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/bc/24/65465d8e5191f4f60caf94353c7b.webp)
|
||||
|
||||
##### 帧间间隔IFS(InterFrame Space)
|
||||
|
||||
![](../../images/408/《计网》数据链路层/帧间间隔IFS(InterFrame%20Space.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/ba/01/2da5b1858f2a09d90d1fd13164eb.webp)
|
||||
|
||||
##### 退避算法工作原理
|
||||
|
||||
![](../../images/408/《计网》数据链路层/退避算法工作原理.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/30/18/4e5bd65f5a4c0ca700c87ab1a583.webp)
|
||||
|
||||
##### CSMA/CA是什么
|
||||
|
||||
![](../../images/408/《计网》数据链路层/CSMACA是什么.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/ca/c0/4414441687e2e1b444b689d16b2e.webp)
|
||||
|
||||
##### CSMA/CA的工作原理
|
||||
|
||||
![](../../images/408/《计网》数据链路层/CSMACA的工作原理.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/9a/35/db5d64a18911181380aa429a96d5.webp)
|
||||
|
||||
##### 退避算法示意
|
||||
|
||||
![](../../images/408/《计网》数据链路层/退避算法示意图.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/1d/6f/4341e0e4591bf3cd5fe828b0383f.webp)
|
||||
|
||||
##### 虚拟载波监听
|
||||
|
||||
![](../../images/408/《计网》数据链路层/虚拟载波监听.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/3e/e8/7d9727ea767d188d0bde4d8919db.webp)
|
||||
|
||||
#### 令牌传递协议
|
||||
|
||||
|
@ -356,19 +356,19 @@ date: 2023-07-25T19:25:31+08:00
|
|||
|
||||
### 基本概述
|
||||
|
||||
![](../../images/408/《计网》数据链路层/MAC地址的基本概述.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/60/08/9a036a6a56f2e1611ab92d69d5b2.webp)
|
||||
|
||||
### IEEE802局域网的MAC地址发送顺序
|
||||
|
||||
![](../../images/408/《计网》数据链路层/IEEE802.11局域网的MAC地址发送顺序.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/b0/eb/6c95cab6434db8e3a8316f8d0454.webp)
|
||||
|
||||
### IEEE802局域网的MAC地址格式
|
||||
|
||||
![](../../images/408/《计网》数据链路层/IEEE802.11局域网的MAC地址格式.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/af/04/1793299a703519be25f5ea210a36.webp)
|
||||
|
||||
### 以太网和802的MAC帧示意图
|
||||
|
||||
![](../../images/408/《计网》数据链路层/以太网和802的MAC帧示意图.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/original/a4/49/13df1051e5b9af7cba1569ecdb0d.webp)
|
||||
|
||||
## ARP(address resolution protocol)协议
|
||||
|
||||
|
@ -393,7 +393,7 @@ date: 2023-07-25T19:25:31+08:00
|
|||
|
||||
### 以太网交换机的概述
|
||||
|
||||
![](../../images/408/《计网》数据链路层/以太网交换机的概述.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/71/b8/5cd3488bc8a3f92a78a109b3c764.webp)
|
||||
|
||||
### 以太网交换机自学习和转发帧的过程
|
||||
|
||||
|
@ -401,19 +401,19 @@ date: 2023-07-25T19:25:31+08:00
|
|||
* 以太网交换机收到帧后,在帧交换表中查找帧的目的MAC地址所对应的接口号,然后通过该接口转发帧
|
||||
* 以太网交换机是一种即插即用的设备,刚上电启动时其内部的帧交换表是空的
|
||||
* 随着网络各主机间的通信,以太网交换机通过自学习算法自动逐渐建立起帧交换表
|
||||
* ![](../../images/408/《计网》数据链路层/以太网交换机自学习和转发帧的过程.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/6b/f1/362632b41c756255a4d807c1a56b.webp)
|
||||
* 例题
|
||||
* ![](../../images/408/《计网》数据链路层/例题以太网交换机自学习和转发帧的过程.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/89/0d/e4f5f7b5d756ad83b5a1e105ac50.webp)
|
||||
|
||||
### 以太网交换机生成树协议STP
|
||||
|
||||
![](../../images/408/《计网》数据链路层/以太网交换机生成树协议STP.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/91/4a/b906c1475e5f3762564410df34fd.webp)
|
||||
|
||||
### 集线器和交换机的对比
|
||||
|
||||
![](../../images/408/《计网》数据链路层/集线器和交换机的对比1.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/5b/77/75f40dd9b2140d33226ee58fb963.webp)
|
||||
|
||||
![](../../images/408/《计网》数据链路层/集线器和交换机的对比2.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/c0/bb/a5124a8327ce121ed3e89d74032d.webp)
|
||||
|
||||
## 局域网和广域网
|
||||
|
||||
|
@ -441,10 +441,10 @@ date: 2023-07-25T19:25:31+08:00
|
|||
* 有效共享网络资源
|
||||
* 简化网络管理
|
||||
* 提高网络安全性
|
||||
* ![](../../images/408/《计网》数据链路层/VLAN的概述.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/74/e6/c581caeeb70d4b4b88a293914982.webp)
|
||||
|
||||
### VLAN的实现机制
|
||||
|
||||
IEEE 802.1Q帧
|
||||
|
||||
![](../../images/408/《计网》数据链路层/VLAN的实现机制.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/medium/e9/c0/bac83ae41ed754651b90b52b4695.webp)
|
|
@ -103,11 +103,11 @@ date: 2023-07-24T16:46:37+08:00
|
|||
* 噪声干扰
|
||||
* 传输媒体的质量
|
||||
* 码元传输速率越大、信号传输距离越远、噪声干扰越大或传输媒体质量越差、波形失真越严重
|
||||
* ![](../../images/408/《计网》物理层/失真.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/30/d5/c570d19e2209682e0dae7d70d262.webp)
|
||||
* 码间串扰
|
||||
* 接收端收到的信号波形市区了码元之间清晰界限的现象
|
||||
* 具体的信道所能通过的频率范围是有限的
|
||||
* ![](../../images/408/《计网》物理层/码间干扰.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/b4/be/345a930762e12bbcee3cc98368f2.webp)
|
||||
* 奈氏准则
|
||||
* 在理想低通(无噪声、带宽受限)条件下,为了避免码间串扰,极限码元传输速率为2W Baud,W是信道带宽,单位是Hz
|
||||
* 带宽只有在奈氏准则和香农定理中单位是HZ,其余都是b/s
|
||||
|
@ -130,7 +130,7 @@ date: 2023-07-24T16:46:37+08:00
|
|||
|
||||
## 编码和调制
|
||||
|
||||
![](../../images/408/《计网》物理层/编码和调制.png)
|
||||
![](https://lychee.inksoul.top/uploads/original/d9/80/591e6a78f5d3b12399c98de73d5b.webp)
|
||||
|
||||
* 信道上传送的信号类型
|
||||
* 基带信号
|
||||
|
@ -152,7 +152,7 @@ date: 2023-07-24T16:46:37+08:00
|
|||
## 四种编码方式
|
||||
|
||||
### 数字数据编码为数字信号
|
||||
* ![](../../images/408/《计网》物理层/数字数据编码为数字信号.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/79/9e/6684672393168fd011f917ed450d.webp)
|
||||
* 归零编码
|
||||
* 信号电平在一个码元之内都要恢复到零的编码方式
|
||||
* 这种编码在传输过程中处于低电平的情况多,信道利用率低
|
||||
|
@ -178,7 +178,7 @@ date: 2023-07-24T16:46:37+08:00
|
|||
|
||||
### 数字数据调制为模拟信号
|
||||
|
||||
![](../../images/408/《计网》物理层/数字数据调制为模拟信号.png)
|
||||
![](https://lychee.inksoul.top/uploads/original/4e/8c/670cfa948e32d808dff8d9936f92.webp)
|
||||
|
||||
* 调幅
|
||||
* 即戴波的振幅随基带数字信号而变化,如0或1分别对应无载波或有载波输出
|
||||
|
@ -212,7 +212,7 @@ date: 2023-07-24T16:46:37+08:00
|
|||
|
||||
## 电路交换、报文交换、分组交换
|
||||
|
||||
![](../../images/408/《计网》物理层/三种交换的比较.png)
|
||||
![](https://lychee.inksoul.top/uploads/original/72/80/79b974ccf1b1920fe58ab1fc336c.webp)
|
||||
|
||||
* 电路交换
|
||||
* 电路交换需要建立一条专用的数据通信路径,这条路径上可能包含许多中间节点
|
||||
|
@ -317,7 +317,7 @@ date: 2023-07-24T16:46:37+08:00
|
|||
* 5-4-3规则
|
||||
* 网络标准中都对信号的延迟范围作了具体的规定,因而中继器只能在规定的范围内进行,否则会网络故障
|
||||
* 以太网有5个网段,4个网络设备,3个段连接计算机
|
||||
* ![](../../images/408/《计网》物理层/5-4-3规则.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/d6/65/9e60ffb27a73a9fef2b59ee7f28b.webp)
|
||||
* 集线器
|
||||
* 本质为一个多端口的中继器
|
||||
* 功能
|
||||
|
|
|
@ -71,7 +71,7 @@ date: 2023-07-26T11:37:50+08:00
|
|||
* 分组转发,处理通过路由器的数据流
|
||||
* 路由计算,通过和其他路由器进行路由协议的交互,完成路由表的计算
|
||||
* 路由器的组成
|
||||
* ![](../../images/408/《计网》网络层/路由器的组成.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/df/f2/0794d8841f20f5e74b97b0250c67.webp)
|
||||
* 路由选择部分
|
||||
* 路由选择处理机 + 路由选择协议 + 路由表
|
||||
* 控制部分,核心是路由选择处理机
|
||||
|
@ -93,14 +93,14 @@ date: 2023-07-26T11:37:50+08:00
|
|||
* 路由表总是用软件实现,转发表可以用软件也可以用邮件实现
|
||||
* 路由表不等于转发表,分组的实际转发是靠直接查找转发表,而不是直接查找路由表
|
||||
* 路由表中默认路由的目的地址和子网掩码都是0.0.0.0
|
||||
* ![](../../images/408/《计网》网络层/路由表.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/c7/4a/0d9dd18c287cae9e4bbb10b167bb.webp)
|
||||
|
||||
|
||||
## IP地址的基本知识
|
||||
|
||||
### IP地址的定义
|
||||
|
||||
![](../../images/408/《计网》网络层/IP地址定义.png)
|
||||
![](https://lychee.inksoul.top/uploads/original/d5/cc/6dc232b58d019b86495488efbdd7.webp)
|
||||
|
||||
* MAC的作用则是实现直连的两个设备之间通信,而IP负责在没有直连的两个网络之间进行通信传输
|
||||
* 源IP地址和目标IP地址在传输过程中是不会变化的(没有使用NAT网络情况下),只有源MAC地址和目标MAC一直在变化
|
||||
|
@ -112,7 +112,7 @@ date: 2023-07-26T11:37:50+08:00
|
|||
|
||||
#### 分类
|
||||
|
||||
![](../../images/408/《计网》网络层/分类编制的IPV4地址.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/original/8b/5c/ef9fffff5c4e1fa1a09f3839e4a5.webp)
|
||||
|
||||
* ABC类地址主要由网络号和主机号组成
|
||||
* 网络号标志主机/路由器所连接到的网络
|
||||
|
@ -142,15 +142,15 @@ date: 2023-07-26T11:37:50+08:00
|
|||
* C类地址254个太少了,B类地址65534个又太多了,不能很好地与显示网络匹配
|
||||
* 可用CIDR解决
|
||||
* 例题
|
||||
* ![](../../images/408/《计网》网络层/例题分类编制的IPV4地址.jpg)
|
||||
* 一般不适用的IP地址
|
||||
* ![](../../images/408/《计网》网络层/一般不使用的IP地址.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/bc/5e/2c33f657858ce08f219038820a13.webp)
|
||||
* 一般不使用的IP地址
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/53/e1/ed2cd8c619694b58902878ef9ccd.webp)
|
||||
|
||||
### 划分子网的IP地址
|
||||
|
||||
![](../../images/408/《计网》网络层/划分子网的IPV4地址.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/original/92/26/0726ebcfc604b5283a6fd0812626.webp)
|
||||
|
||||
![](../../images/408/《计网》网络层/划分子网的IPV4地址2.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/original/1f/18/bedb485bcbd45e3281472d20fed4.webp)
|
||||
|
||||
* 划分子网原因
|
||||
* 两级IP地址分类的地址空间流动率有时很低,用子网划分的方法来改善这个问题
|
||||
|
@ -174,9 +174,9 @@ date: 2023-07-26T11:37:50+08:00
|
|||
* 根据子网掩码可知从8位主机号中借用2位作为子网号
|
||||
* 由于子网网络地址被划分成2位,那么子网地址就有4个,分别是00、01、10、11
|
||||
* 划分后的4个子网如下图
|
||||
* ![](../../images/408/《计网》网络层/例题划分子网的IPV4地址.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/4e/dd/757c0b42b3e6813fb8f7bce3696d.webp)
|
||||
|
||||
### 无分类编制的IPV4地址【CIDR】
|
||||
### 无分类编址的IPV4地址【CIDR】
|
||||
|
||||
* 引入原因
|
||||
* CIDR消除了传统的A类,B类和C类地址,以及划分子网的概念
|
||||
|
@ -184,14 +184,14 @@ date: 2023-07-26T11:37:50+08:00
|
|||
* 一种归并技术,可以把小的网络汇聚成大的超网
|
||||
* 可以更加有效地分配IPV4的地址空间,并且可以在新的IPV6使用之前允许因特网的规模继续增长
|
||||
* 细节
|
||||
* ![](../../images/408/《计网》网络层/无分类编制的IPV4地址.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/2f/0f/583324a4889ce029dd6eabda92e9.png)
|
||||
* 路由聚合
|
||||
* 为了减少路由表的消耗,用路由聚合来聚合网络地址
|
||||
* 网络前缀越长,地址块越小,路由越具体
|
||||
* 最长前缀匹配:有多条路由可选的时候,选择网络前缀最长的那条
|
||||
* ![](../../images/408/《计网》网络层/路由聚合.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/96/93/1f97b6950131187d8e4baa5c946a.webp)
|
||||
* 例题
|
||||
* ![](../..images/《计网》网络层/例题无分类编制的IPV4地址.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/b8/69/ca03cd0985536b01a3a00f235e1b.webp)
|
||||
* 答案为C
|
||||
|
||||
### IPV4的应用规划
|
||||
|
@ -200,13 +200,13 @@ date: 2023-07-26T11:37:50+08:00
|
|||
* 使用同一个子网掩码来划分子网
|
||||
* 子网划分方式不灵活,只能划分出$2^n$个子网
|
||||
* 每个子网所分配的IP地址数量相同,容易造成IP地址浪费
|
||||
* ![](../../images/408/《计网》网络层/定长的子网掩码.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/1d/11/797ee374b8671497fd02b947fd55.webp)
|
||||
* 变长的子网掩码
|
||||
* 使用不同的子网掩码来划分子网
|
||||
* 子网划分方式灵活,可以按需分配
|
||||
* 每个子网所分配的IP地址数量可以不同,尽可能减少对IP地址的浪费
|
||||
* ![](../../images/408/《计网》网络层/变长的子网掩码1.jpg)
|
||||
* ![](../../images/408/《计网》网络层/变长的子网掩码2.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/25/3d/1445f92c3dff1173822e5cffbd97.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/43/23/a1e9c530c7e66edcbea41565fe2c.webp)
|
||||
|
||||
### IP数据报的发送和转发过程
|
||||
|
||||
|
@ -219,36 +219,36 @@ date: 2023-07-26T11:37:50+08:00
|
|||
* 出错,直接丢弃该IP数据报并通告源主机
|
||||
* 没有出错,直接进行转发
|
||||
* 根据IP数据报的目的地址,在路由表中查找匹配的条目
|
||||
* ![](../../images/408/《计网》网络层/路由器转发IP数据报.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/2d/e1/fd68f4805a925538d85b5f75a25f.webp)
|
||||
* 若找到匹配的条目,则转发给条目中指示的下一跳
|
||||
* 若找不到,则丢弃该IP数据报并通告源主机
|
||||
|
||||
### 静态路由配置及其可能产生的路由环路问题
|
||||
|
||||
* 静态路由配置
|
||||
* ![](../../images/408/《计网》网络层/静态路由配置.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/92/3b/3a7d185322e173c7d16f255fd7b4.webp)
|
||||
* 特定主机路由(默认路由)
|
||||
* ![](../../images/408/《计网》网络层/特定主机路由.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/47/c3/c7c397c85959c1142ea2d06b140e.webp)
|
||||
* 静态路由配置错误导致路由环路
|
||||
* ![](../../images/408/《计网》网络层/静态路由配置错误导致路由环路.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/9d/5b/d9cf8d5b68b8d22f28db70d0554d.webp)
|
||||
* 为了防止IP数据报在路由环路中永久兜圈,在IP数据报首部设有生存时间TTL字段
|
||||
* IP数据报进入路由器后,TTL字段的值减1
|
||||
* 若TTL的值不等于0,则被路由器转发,否则被丢弃
|
||||
* 聚合不存在的网络而导致的路由环路
|
||||
* ![](../../images/408/《计网》网络层/聚合不存在的网络而导致的路由环路.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/d7/43/383d61975df79cd5a1cfdb0e876b.webp)
|
||||
* 用黑洞路由条目配置解决
|
||||
* 网络故障而导致的路由环路
|
||||
* ![](../../images/408/《计网》网络层/网络故障而导致的路由环路.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/38/07/6961ec4a414337b7d40b7c6db4f9.webp)
|
||||
* 用黑洞路由条目配置解决该问题
|
||||
* 如果故障消失了,会暂时把黑洞路由条目设置为失效
|
||||
|
||||
### IPV6
|
||||
|
||||
![](../../images/408/《计网》网络层/IPV61.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/original/86/29/c06933f1dbe0e385d11ab465a813.webp)
|
||||
|
||||
![](../../images/408/《计网》网络层/IPV62.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/original/b1/aa/b5f6dad7b2d0c0e54fea69f907c9.webp)
|
||||
|
||||
![](../../images/408/《计网》网络层/IPV61.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/original/c3/c5/77e0dce75a8497bde251b703db2e.webp)
|
||||
|
||||
* IPV6地址的标识方法
|
||||
* IPV6地址长度是128位,是以每16位作为一组
|
||||
|
@ -276,34 +276,34 @@ date: 2023-07-26T11:37:50+08:00
|
|||
|
||||
### IPV4首部
|
||||
|
||||
![](../../images/408/《计网》网络层/IPV4首部.jpg)
|
||||
![](https://lychee.inksoul.top/uploads/original/d6/b9/c8c4f4032889d13e7ae295dbbc81.webp)
|
||||
|
||||
* 首部内容
|
||||
* 首部长度,总长度,片偏移的基本单位分别为4B,1B,8B
|
||||
* ![](../../images/408/《计网》网络层/首部内容.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/5d/c3/5756d438e1a3dfcaed341be58443.webp)
|
||||
* IPV4分片
|
||||
* 以太网MTU【最大传输单元】不超过1500
|
||||
* DF=1时,分组的长度又超过MTU时,丢弃该分组,并用ICMP差错报文向源主机报告
|
||||
* MF = 1,表示接受到的分片不是最后一个分片
|
||||
* 所有片中的有效数据核载都是8的倍数【偏移值的单位是8B】
|
||||
* 在目的主机中对分片后的数据报重组
|
||||
* ![](../../images/408/《计网》网络层/IPV4分片1.jpg)
|
||||
* ![](../../images/408/《计网》网络层/IPV4分片2.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/6b/8b/dcacae0aeb7f796b706cf20bc2bb.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/4a/5d/aeeb95984fd722d28bbfb5815031.webp)
|
||||
* 例题
|
||||
* ![](../../images/408/《计网》网络层/IPV4分片例题.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/1c/d6/f01a6c8585a2ce5565d52fbb9bb7.webp)
|
||||
|
||||
## 路由选择协议概述
|
||||
|
||||
* 静态路由选择/动态路由选择
|
||||
* ![](../../images/408/《计网》网络层/路由选择.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/6e/0f/2be6d1fbb6c98cff26960bf8778d.webp)
|
||||
* 路由协议的主要特点
|
||||
* 自适应-动态路由选择,能较好地适应网络状态的变化
|
||||
* 分布式-路由器之间交换路由信息
|
||||
* 分层次-将整个因特网划分为许多较小的自治系统
|
||||
* 分层次的路由选择协议
|
||||
* ![](../../images/408/《计网》网络层/分层次的路由选择协议.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/55/0d/a071fb917039c8beb108f7e36df2.webp)
|
||||
* 路由选择协议
|
||||
* ![](../../images/408/《计网》网络层/路由选择协议汇总.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/b7/e7/38c7b140c2ddfe3411b7bda3be54.webp)
|
||||
|
||||
### 三种路由协议比较
|
||||
|
||||
|
@ -319,45 +319,45 @@ date: 2023-07-26T11:37:50+08:00
|
|||
### 路由信息协议RIP的工作原理
|
||||
|
||||
* RIP基本概念
|
||||
* ![](../../images/408/《计网》网络层/RIP基本概念.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/57/ae/bd90b8b8eeb019862efa9332831e.webp)
|
||||
* RIP工作原理
|
||||
* ![](../../images/408/《计网》网络层/RIP工作原理.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/50/a0/318438ba02fad7b8b682e5b21413.webp)
|
||||
* RIP基本工作过程
|
||||
* ![](../../images/408/《计网》网络层/RIP基本工作过程.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/1f/b7/8f038bcb8fa4f51e649a87e94362.webp)
|
||||
* RIP路由条目更新规则
|
||||
* ![](../../images/408/《计网》网络层/RIP路由条目更新规则.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/10/7d/1a3973e35504ca0288039e907453.webp)
|
||||
* RIP坏消息传播得慢
|
||||
* ![](../../images/408/《计网》网络层/RIP坏消息传的慢的问题.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/29/e0/4683d4151ad74dc4a92b66d6157a.webp)
|
||||
|
||||
### 开放最短路径优先OSPF的基本工作原理
|
||||
|
||||
* OSPF基本概念
|
||||
* ![](../../images/408/《计网》网络层/OSPF基本概念.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/9a/32/72bd5285e47ac7e2390cfeeb74c9.webp)
|
||||
* 区域边界路由器:主干区域内,用于连接主干区域和其他下层区域的路由器
|
||||
* 主要在主干区域中的路由器都叫做主干路由器
|
||||
* 主干路由器可以兼做区域边界路由器
|
||||
* 自治系统有4类路由器,区域内部路由器,主干路由器,区域边界路由器,自治域边界路由器
|
||||
* 链路的代价
|
||||
* ![](../../images/408/《计网》网络层/链路的代价.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/f3/87/dda43409fb36f72f29c9084fd00a.webp)
|
||||
* 交互问候分组
|
||||
* ![](../../images/408/《计网》网络层/交互问候分组.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/22/30/1ee55990f36c17426ce08a4759d9.webp)
|
||||
* 计算最短路径的过程
|
||||
* ![](../../images/408/《计网》网络层/计算最短路径的过程.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/03/00/35dc743faa10d439c11c37a0ba13.webp)
|
||||
* 五种分组类型
|
||||
* ![](../../images/408/《计网》网络层/五种分组类型.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/30/e4/487f213dc0792dce70c8aeb1e409.webp)
|
||||
* OSPF的基本工作过程
|
||||
* ![](../../images/408/《计网》网络层/OSPF的基本工作过程.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/ec/b0/565836568df87eb2a8ce85e59ff1.webp)
|
||||
* DR和BDR
|
||||
* ![](../../images/408/《计网》网络层/DR和BDR.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/da/38/856556107a5d0b4149588c973801.webp)
|
||||
* 区域
|
||||
* ![](../../images/408/《计网》网络层/区域.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/c3/60/88bc7f661a24e412e223eba641fd.webp)
|
||||
* 总结
|
||||
* ![](../../images/408/《计网》网络层/内容总结.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/04/8d/36490ba79ab30f0aaeeac9687ecf.webp)
|
||||
|
||||
### 边界网关协议BGP的工作原理
|
||||
|
||||
* BGP交换的网络可达性信息,即:要到达某个网络所要结果的一系列自治系统/路径
|
||||
* ![](../../images/408/《计网》网络层/边界网关协议BGP的工作原理.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/59/b0/9b31b1912386977b198045bd7801.webp)
|
||||
|
||||
|
||||
## IP协议相关技术
|
||||
|
@ -365,22 +365,21 @@ date: 2023-07-26T11:37:50+08:00
|
|||
### ICMP【互联网控制报文协议】
|
||||
|
||||
* 概述
|
||||
* ![](../../images/408/《计网》网络层/ICMP概述.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/c9/06/a3cf13e5bad5191291aa00fb1c4f.webp)
|
||||
* 五种差错报文
|
||||
* ![](../../images/408/《计网》网络层/五种差错报文1.jpg)
|
||||
* ![](../../images/408/《计网》网络层/五种差错报文2.jpg)
|
||||
* ![](../../images/408/《计网》网络层/五种差错报文3.jpg)
|
||||
* ![](../../images/408/《计网》网络层/五种差错报文4.jpg)
|
||||
* ![](../../images/408/《计网》网络层/五种差错报文5.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/81/eb/f41d08805d9aff8b7ce6a92dfec2.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/aa/6a/a39a140f3eba141c8d104cbea275.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/46/f9/05a0e0025243a5c5d04454d2b1d7.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/ca/4d/ace88968c625f1bd9410fe706fcb.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/e6/16/09cfab38b456d4186229cb5b7fef.webp)
|
||||
* 不应该发送差错报文的情况
|
||||
* ![](../../images/408/《计网》网络层/不应该发送差错报文的情况.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/b3/1a/bc8e2771086a8a9464e27b4ca137.webp)
|
||||
* ICMP询问方式
|
||||
* ![](../../images/408/《计网》网络层/ICMP询问方式.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/03/da/b7f635deb9d791729e7605b3265e.webp)
|
||||
* ICMP应用
|
||||
* ![](../../images/408/《计网》网络层/ICMP应用1.jpg)
|
||||
* ![](../../images/408/《计网》网络层/ICMP应用2.jpg)
|
||||
* ![](../../images/408/《计网》网络层/ICMP应用3.jpg)
|
||||
* ![](../../images/408/《计网》网络层/ICMP应用4.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/62/d4/9a4e54dcb6a37d955758d1916946.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/31/e9/41776e9e0e812391384b032a1fd1.webp)
|
||||
|
||||
|
||||
### ARP协议【IP地址到MAC地址的映射】
|
||||
|
||||
|
@ -401,22 +400,22 @@ date: 2023-07-26T11:37:50+08:00
|
|||
### DHCP协议【动态主机配置协议】
|
||||
|
||||
* DHCP主要内容
|
||||
* ![](../../images/408/《计网》网络层/DHCP主要内容.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/ed/8a/86201b647999f2e89ea1ad2fe22d.webp)
|
||||
* DHCP过程
|
||||
* ![](../../images/408/《计网》网络层/DHCP过程.jpg)
|
||||
* ![](../../images/408/《计网》网络层/DHCP过程1.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/d5/c0/bc3028f4e2215a4d9630a534e0f6.webp)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/4e/b8/e5bc713996006500b10514598c17.webp)
|
||||
|
||||
### 虚拟专用网VPN和网络地址转换NAT
|
||||
|
||||
* 公有地址,私有地址
|
||||
* ![](../../images/408/《计网》网络层/公有地址,私有地址.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/e4/36/cc361eaf2af106659f214e159222.webp)
|
||||
* 虚拟专用网VPN
|
||||
* ![](../../images/408/《计网》网络层/虚拟专用网VPN.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/a4/bf/bcaaf628064fd03d153a94ae9ee3.webp)
|
||||
* 网络地址转换NAT
|
||||
* ![](../../images/408/《计网》网络层/网络地址转换NAT.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/medium/b6/96/cafd32ba79f44ee21b599f481aa0.webp)
|
||||
* NAT的表项需要由管理员来添加
|
||||
* NAT转换流程
|
||||
* ![](../../images/408/《计网》网络层/NAT转换流程.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/b6/23/0ef9c72450fde279c5f8605516a5.webp)
|
||||
* 上图有两个客户端192.168.1.10和192.168.1.11
|
||||
* 与服务器183.232.231.172进行通信,并且这两个客户端的本地端口都是1025
|
||||
* 此时,两个私有IP都转换IP为公有地址120.229.175.121,但以不同的端口号作为区分
|
||||
|
|
|
@ -145,7 +145,7 @@ date: 2023-07-24T13:31:22+08:00
|
|||
* 相互通信的两个计算机系统必须高度协调工作,这种协调是相当复杂的
|
||||
* 分层可以将庞大而复杂的问题转化为若干个较小的局部问题,而这些较小的局部问题就比较易于研究和处理
|
||||
* 实体、协议、服务和服务访问点
|
||||
* ![](../../images/408/《计网》计算机网络体系结构/实体协议图示.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/7a/c2/09276bd0dfe72d1623060be00ade.webp)
|
||||
* 实体
|
||||
* 表示任何可以发送或接受信息的硬件或软件进程。同一层的实体称为对等实体
|
||||
* 协议
|
||||
|
@ -196,7 +196,7 @@ date: 2023-07-24T13:31:22+08:00
|
|||
|
||||
### 两个主机通信的过程
|
||||
|
||||
![](../../images/408/《计网》计算机网络体系结构/主机通信过程.png)
|
||||
![](https://lychee.inksoul.top/uploads/original/b8/bb/f487b2c2762707619f8f8249fb19.webp)
|
||||
|
||||
1. 主机A先将其数据交给本机的第7层(应用层)。第5层加上必要的控制信息H7就变成了下一层的数据单元
|
||||
2. 第6层(表示层)收到数据单元后,加上本层的控制信息H6就变成了下一层的控制信息,依次类推
|
||||
|
@ -211,18 +211,18 @@ date: 2023-07-24T13:31:22+08:00
|
|||
### 三种网络模型
|
||||
|
||||
* OSI七层模型
|
||||
* ![](../../images/408/《计网》计算机网络体系结构/OSI七层模型.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/b8/bb/f487b2c2762707619f8f8249fb19.webp)
|
||||
* 表示层
|
||||
* 数据压缩、加密及数据描述,使得应用程序不必关系再各台主机中数据内部格式不同的问题
|
||||
* 会话层
|
||||
* 建立及管理会话
|
||||
* TCP/IP结构
|
||||
* ![](../../images/408/《计网》计算机网络体系结构/TCPIP结构.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/ec/ab/f5cee48f74cf75cba0e75717d2bd.webp)
|
||||
* 只有四层,相当于五层协议中数据链路层和物理层合并为网络接口层
|
||||
* TCP/IP体系结构不严格遵循OSI分层概念
|
||||
* 应用层可能会直接使用IP层或网络接口层
|
||||
* 五层协议结构
|
||||
* ![](../../images/408/《计网》计算机网络体系结构/五层协议结构.png)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/49/5a/f4dbbb292d4cdbabd56fcad4884a.webp)
|
||||
* 应用层
|
||||
* 通过应用进程间的交互来完成特定网络应用,数据单位为报文
|
||||
* 运输层
|
||||
|
@ -238,4 +238,4 @@ date: 2023-07-24T13:31:22+08:00
|
|||
* 物理层
|
||||
* 主要负责在物理线路上传输原始的二进制数据
|
||||
* 三个网络模型的对比
|
||||
* ![](../../images/408/《计网》计算机网络体系结构/三者的对比.jpg)
|
||||
* ![](https://lychee.inksoul.top/uploads/original/c2/65/bc2f1212f6dcc2b91ebf068f1ba3.webp)
|
|
@ -8,6 +8,7 @@ clone:
|
|||
|
||||
steps:
|
||||
- name: build
|
||||
pull: if-not-exists
|
||||
image: inksoul/hugo-rsync
|
||||
depends_on: [clone] # 依赖的步骤,
|
||||
volumes: #挂载数据卷
|
||||
|
|
Before Width: | Height: | Size: 71 KiB |
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Before Width: | Height: | Size: 213 KiB |
Before Width: | Height: | Size: 129 KiB |
Before Width: | Height: | Size: 169 KiB |
Before Width: | Height: | Size: 109 KiB |
Before Width: | Height: | Size: 183 KiB |
Before Width: | Height: | Size: 126 KiB |
Before Width: | Height: | Size: 226 KiB |
Before Width: | Height: | Size: 126 KiB |
Before Width: | Height: | Size: 164 KiB |
Before Width: | Height: | Size: 106 KiB |
Before Width: | Height: | Size: 220 KiB |
Before Width: | Height: | Size: 134 KiB |
Before Width: | Height: | Size: 137 KiB |
Before Width: | Height: | Size: 183 KiB |
Before Width: | Height: | Size: 115 KiB |
Before Width: | Height: | Size: 156 KiB |
Before Width: | Height: | Size: 363 KiB |
Before Width: | Height: | Size: 124 KiB |
Before Width: | Height: | Size: 114 KiB |
Before Width: | Height: | Size: 158 KiB |
Before Width: | Height: | Size: 24 KiB |
Before Width: | Height: | Size: 58 KiB |
Before Width: | Height: | Size: 178 KiB |
Before Width: | Height: | Size: 102 KiB |
Before Width: | Height: | Size: 115 KiB |
Before Width: | Height: | Size: 115 KiB |
Before Width: | Height: | Size: 200 KiB |
Before Width: | Height: | Size: 70 KiB |
Before Width: | Height: | Size: 327 KiB |
Before Width: | Height: | Size: 125 KiB |
Before Width: | Height: | Size: 288 KiB |
Before Width: | Height: | Size: 111 KiB |
Before Width: | Height: | Size: 380 KiB |
Before Width: | Height: | Size: 180 KiB |
Before Width: | Height: | Size: 364 KiB |
Before Width: | Height: | Size: 176 KiB |
Before Width: | Height: | Size: 268 KiB |
Before Width: | Height: | Size: 120 KiB |
Before Width: | Height: | Size: 419 KiB |
Before Width: | Height: | Size: 183 KiB |
Before Width: | Height: | Size: 227 KiB |
Before Width: | Height: | Size: 87 KiB |
Before Width: | Height: | Size: 408 KiB |
Before Width: | Height: | Size: 204 KiB |
Before Width: | Height: | Size: 267 KiB |
Before Width: | Height: | Size: 119 KiB |
Before Width: | Height: | Size: 476 KiB |
Before Width: | Height: | Size: 219 KiB |
Before Width: | Height: | Size: 288 KiB |
Before Width: | Height: | Size: 113 KiB |
Before Width: | Height: | Size: 329 KiB |
Before Width: | Height: | Size: 177 KiB |
Before Width: | Height: | Size: 404 KiB |
Before Width: | Height: | Size: 180 KiB |
Before Width: | Height: | Size: 249 KiB |
Before Width: | Height: | Size: 100 KiB |