# 计算机网络

**Repository Path**: helloqiyuan/ComputerNetwork

## Basic Information

- **Project Name**: 计算机网络
- **Description**: null..................
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 1
- **Forks**: 0
- **Created**: 2025-07-22
- **Last Updated**: 2025-10-21

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# +计算机网络

**计划十天学一章**

# 第一章：计算机网络的概念

## 第一天：6.23 [1.0-1.1.3.1]

### 1.计算机网络的概念

![image-20250625172816821](pic/image-20250625172816821.png)

![image-20250625172909821](pic/image-20250625172909821.png)

#### 集线器

![image-20250625172948559](pic/image-20250625172948559.png)

#### 交换机

![image-20250625173120326](pic/image-20250625173120326.png)

#### 路由器(PS:不是家用路由器)

![image-20250625173203663](pic/image-20250625173203663.png)

![image-20250625173233379](pic/image-20250625173233379.png)

#### 网络服务提供商(ISP)&互联网

![image-20250625173337203](pic/image-20250625173337203.png)

#### 总结

![image-20250625173412384](pic/image-20250625173412384.png)

### 2.电路交换，报文交换，分组交换⭐

#### 电路交换技术(早期电话网络)

![image-20250625173552884](pic/image-20250625173552884.png)

![image-20250625173719826](pic/image-20250625173719826.png)

#### 报文交换技术(借鉴早期的电报网络)

![image-20250625173821658](pic/image-20250625173821658.png)

![image-20250625173948108](pic/image-20250625173948108.png)

#### 分组交换技术

![image-20250625174014110](pic/image-20250625174014110.png)

![image-20250625174119345](pic/image-20250625174119345.png)

#### "虚电路交换"技术(基于分组交换)

**基于分组交换，加上电路交换技术建立连接的过程 **

![image-20250625174200874](pic/image-20250625174200874.png)

##  第二天：6.25 [1.1.3.2-1.1.5.2]

### 1.三种交换方式的性能分析⭐

#### 电路交换

![image-20250625155215275](pic/image-20250625155215275.png)

#### 报文交换

![image-20250625155259069](pic/image-20250625155259069.png)

#### 分组交换

![image-20250625155317575](pic/image-20250625155317575.png)![image-20250625155332849](pic/image-20250625155332849.png)

### 2.计算机网络的分类

#### 按分布范围分类

![image-20250625152544611](pic/image-20250625152544611.png)

#### 按传输技术分类

![image-20250625153446777](pic/image-20250625153446777.png)

#### 按拓扑结构分类

![image-20250625153858349](pic/image-20250625153858349.png)

![image-20250625154113320](pic/image-20250625154113320.png)

#### 按使用者分类

![image-20250625154255589](pic/image-20250625154255589.png)

![image-20250625154341141](pic/image-20250625154341141.png)

![image-20250625154628452](pic/image-20250625154628452.png)

### 3.计算机网络的性能指标⭐

![image-20250625155438096](pic/image-20250625155438096.png)

#### 速率

![image-20250625155826757](pic/image-20250625155826757.png)

![image-20250625160455546](pic/image-20250625160455546.png)

#### 带宽

![image-20250625162106595](pic/image-20250625162106595.png)

![image-20250625161955435](pic/image-20250625161955435.png)![image-20250625162733816](pic/image-20250625162733816.png)

#### 吞吐量

![image-20250625162702122](pic/image-20250625162702122.png)

![image-20250625163127842](pic/image-20250625163127842.png)

#### 时延

![image-20250625163353045](pic/image-20250625163353045.png)

![image-20250625164735379](pic/image-20250625164735379.png)

#### 时延带宽积

![image-20250625165244287](pic/image-20250625165244287.png)

![image-20250625170244702](pic/image-20250625170244702.png)

![image-20250625170300418](pic/image-20250625170300418.png)

#### 往返时延RTT

![image-20250625170637728](pic/image-20250625170637728.png)

#### 信道利用率

![image-20250625171000311](pic/image-20250625171000311.png)

## 第三天：6.26 [1.2.1-1.2.3.1]

### 1.计算机网络分层结构

#### 引子:快递网络的五层体系结构

![image-20250626141318671](pic/image-20250626141318671.png)



#### 计算机网络体系结构

![image-20250626141344388](pic/image-20250626141344388.png)

#### 网络体系结构的概念

![image-20250626142124517](pic/image-20250626142124517.png)

#### 各层之间的关系

##### 水平关系



![image-20250626142803233](pic/image-20250626142803233.png)

##### 垂直关系

![image-20250626142901944](pic/image-20250626142901944.png)

#### 数据的传输过程

##### 水平视角

![image-20250626144444687](pic/image-20250626144444687.png)

##### 垂直视角

![image-20250626144545621](pic/image-20250626144545621.png)

#### PDU,SDU,PCI

![image-20250626144852735](pic/image-20250626144852735.png)

#### 协议的三要素

![image-20250626145347954](pic/image-20250626145347954.png)

#### 总结

![image-20250626145424419](pic/image-20250626145424419.png)

### 2.OSI参考模型

![image-20250626150445730](pic/image-20250626150445730.png)

**物联网叔会使用**

![image-20250626150729905](pic/image-20250626150729905.png)

#### #1物理层

![image-20250626151241421](pic/image-20250626151241421.png)

#### #2链路层

![image-20250626151837065](pic/image-20250626151837065.png)

#### #3网络层

![image-20250626152824124](pic/image-20250626152824124.png)

#### #4传输层

![image-20250626153210620](pic/image-20250626153210620.png)

![image-20250626153333344](pic/image-20250626153333344.png)

#### #5~#7

![image-20250626153631161](pic/image-20250626153631161.png)

#### 总结：各层数据传输单位⭐

![image-20250626154034421](pic/image-20250626154034421.png)

![image-20250626154110467](pic/image-20250626154110467.png)

## 第四天：7.10 [1.2.3.2-2.1.3.2]

### 1.TCP IP模型

![image-20250710145806126](pic/image-20250710145806126.png)

#### #1网络接口层

![image-20250710151011215](pic/image-20250710151011215.png)

#### #2网络层

![image-20250710152428199](pic/image-20250710152428199.png)

#### #3传输层

![image-20250710152240259](pic/image-20250710152240259.png)



#### #4应用层

![image-20250710150608242](pic/image-20250710150608242.png)

#### OSI模型 VS TCP/IP模型

![image-20250710151425346](pic/image-20250710151425346.png)

#### 总结

![image-20250710152626628](pic/image-20250710152626628.png)

![image-20250710153222297](pic/image-20250710153222297.png)

# 第二章：物理层

![image-20250710153810163](pic/image-20250710153810163.png)

### 1.通信基础的基本概念

![image-20250710154102949](pic/image-20250710154102949.png)

#### 信源，信宿，信号，信道

![image-20250710154415197](pic/image-20250710154415197.png)

#### 信号:数字信号，模拟信号

![image-20250710154622176](pic/image-20250710154622176.png)

![image-20250710155112472](pic/image-20250710155112472.png)

#### 码元⭐

![image-20250710161810009](pic/image-20250710161810009.png)

![image-20250710161844961](pic/image-20250710161844961.png)

##### 码元与比特的关系

![image-20250710161952843](pic/image-20250710161952843.png)

#### 速率：波特率和比特率⭐

![image-20250710162154521](pic/image-20250710162154521.png)

#### 总结

![image-20250710162303508](pic/image-20250710162303508.png)

### 2.信道的极限容量

![image-20250710162554478](pic/image-20250710162554478.png)

#### 带宽(回顾)

![image-20250710162810275](pic/image-20250710162810275.png)

#### 噪声

![image-20250710163304447](pic/image-20250710163304447.png)

#### 奈奎斯特定理⭐

![image-20250710163623387](pic/image-20250710163623387.png)

##### 例题

![image-20250710163721595](pic/image-20250710163721595.png)

#### 香农定理⭐

##### 信噪比

![image-20250710164103989](pic/image-20250710164103989.png)

![image-20250710164346652](pic/image-20250710164346652.png)

![image-20250710164444268](pic/image-20250710164444268.png)

##### 例题

![image-20250710164808764](pic/image-20250710164808764.png)

#### 奈奎斯特定理&香农定理⭐

![image-20250710165222701](pic/image-20250710165222701.png)

#### 总结

![image-20250710165513495](pic/image-20250710165513495.png)

#### *太阳风暴

![image-20250710165911830](pic/image-20250710165911830.png)

### 3.编码与调制

#### 编码&解码，调制&解调

![image-20250710170446292](pic/image-20250710170446292.png)

#### 常见的编码方法⭐

![image-20250710171907162](pic/image-20250710171907162.png)

![image-20250710171925075](pic/image-20250710171925075.png)

![image-20250710172515225](pic/image-20250710172515225.png)

##### 例题

![image-20250710172944683](pic/image-20250710172944683.png)

![image-20250710173428895](pic/image-20250710173428895.png)

#### 常见的调制方法⭐

![image-20250710174535620](pic/image-20250710174535620.png)

##### 让一个码元携带更多比特

![image-20250710174722849](pic/image-20250710174722849.png)

##### 例题

![image-20250710175326735](pic/image-20250710175326735.png)

#### 总结

![image-20250710175344019](pic/image-20250710175344019.png)

## 第五天：7.20 [2.2-3.3.1.2]

### 4.传输介质

![image-20250720132616914](pic/image-20250720132616914.png)

#### 导向型

##### 双绞线

![image-20250720133652531](pic/image-20250720133652531.png)

![image-20250720133600296](pic/image-20250720133600296.png)

##### 同轴电缆

![image-20250720133858166](pic/image-20250720133858166.png)

![image-20250720133943895](pic/image-20250720133943895.png)

##### 光纤

![image-20250720134240855](pic/image-20250720134240855.png)

![image-20250720134513777](pic/image-20250720134513777.png)

![image-20250720134605585](pic/image-20250720134605585.png)

#### 以太网对有线传输介质得命名规则

![image-20250720135142460](pic/image-20250720135142460.png)

#### 无线传输介质

![image-20250720140008298](pic/image-20250720140008298.png)

##### 微波通信(卫星通行)

![image-20250720140146650](pic/image-20250720140146650.png)

#### 物理层接口的特性

![image-20250720140320933](pic/image-20250720140320933.png)

#### 小结

![image-20250720140800825](pic/image-20250720140800825.png)

### 5.物理层设备

#### 中继器(Repeater)

![image-20250720141715546](pic/image-20250720141715546.png)

![image-20250720141650979](pic/image-20250720141650979.png)

#### 集线器(Hub)

![image-20250720142414751](pic/image-20250720142414751.png)

##### 冲突域

![image-20250720142435921](pic/image-20250720142435921.png)

##### 例题

![image-20250720142516738](pic/image-20250720142516738.png)

#### 集线器，中继器的一些特征

![image-20250720143056878](pic/image-20250720143056878.png)

![image-20250720143200159](pic/image-20250720143200159.png)

![image-20250720143334638](pic/image-20250720143334638.png)

![image-20250720143838698](pic/image-20250720143838698.png)

#### 小结

![image-20250720144219293](pic/image-20250720144219293.png)

# 第三章：数据链路层

![image-20250720145024640](pic/image-20250720145024640.png)

### 数据链路层的功能

![image-20250720145054030](pic/image-20250720145054030.png)

### 1.组帧

![image-20250720150920261](pic/image-20250720150920261.png)

#### 字符计数法

**-发送方在帧的数据部分的开头加一个定长计数字段(一般是八位)表示这个帧的字节数([1,255])，这个长字节数包括计数字段本身。**

**-接收方通过识别这个计数字段确认帧长**

![image-20250720150937297](pic/image-20250720150937297.png)

#### 字节填充法

**SOH：Start Of Header**

**EOT：End Of Transmission **

**-发送方在帧的数据部分的开头加上SOH字符以及在尾部加上EOT，分别作为帧的开头和结尾。若帧的数据部分出现SOH和EOT字符，则在其前面加一个ESC转义字符表示这是数据而不是SOH或EOT控制字符；若帧的数据部分出现ESC处理方法也是在其前面加一个ESC转义字符。**

**-接收方通过识别SOH和EOT确认一个帧的边界,每次遇到ESC都会将其后方的一个字节认为是数据而不是控制字符或转义字符。**

![image-20250720151652422](pic/image-20250720151652422.png)

![image-20250720151706503](pic/image-20250720151706503.png)

#### 零比特填充法

**-发送方在帧的数据部分的开头和结尾加上`01111110`表示帧开始和帧结束。若数据部分出现连续的`5`个`1`，发送方会在后面追加一个`0`，这样就不会出现连续的`6`个`1`，意义是与帧开始和帧结束字符区分。**

**-接收方发现帧的数据部分中存在连续的`5`个`1`，就会把其后的发送方追加的`0`删除，把帧恢复成原始的数据**

![image-20250720152412506](pic/image-20250720152412506.png)

#### 违规编码法

**数据链路层不做任何处理，数据链路层把帧交给物理层，以物理层信号不跳变的某一周期作为帧的开始或结束，此法需要曼彻斯特编码配合**

![image-20250720154219002](pic/image-20250720154219002.png)

#### 小结

![image-20250720155535765](pic/image-20250720155535765.png)

### 2.差错控制

![image-20250720160340609](pic/image-20250720160340609.png)

#### 检错编码 

##### 奇偶校验码

![image-20250720161339271](pic/image-20250720161339271.png)

![image-20250720161926418](pic/image-20250720161926418.png)

![image-20250720162144697](pic/image-20250720162144697.png)

##### 循环冗余校验码(CRC码)

![image-20250720162320357](pic/image-20250720162320357.png)![image-20250720164935196](pic/image-20250720164935196.png)

![image-20250720164918154](pic/image-20250720164918154.png)

![image-20250720165129159](pic/image-20250720165129159.png)

![image-20250720165842690](pic/image-20250720165842690.png)

![image-20250720165949606](pic/image-20250720165949606.png)

![image-20250720170013487](pic/image-20250720170013487.png)

![image-20250720170025600](pic/image-20250720170025600.png)

*循环的出处*

**前一个出错位得余数除以1101得出来的后一个出错位的余数**

![image-20250720170303965](pic/image-20250720170303965.png)

#### 纠错编码

##### 海明校验码

![image-20250720171453453](pic/image-20250720171453453.png)

![image-20250722135956986](pic/image-20250722135956986.png)

![image-20250722140401323](pic/image-20250722140401323.png)

![image-20250722140503872](pic/image-20250722140503872.png)

![image-20250722140851526](pic/image-20250722140851526.png)

![image-20250722140913510](pic/image-20250722140913510.png)

## 第六天：7.22 [3.3.2-3.4.5]

### 3.流量控制与可靠传输

#### 滑动窗口机制

![image-20250722142238465](pic/image-20250722142238465.png)

![image-20250722142317835](pic/image-20250722142317835.png)

![image-20250722142425422](pic/image-20250722142425422.png)

#### 停止-等待协议(S-W)

**S：Stop，W：Wait**

![image-20250722142733536](pic/image-20250722142733536.png)

##### 数据帧，确认帧，帧序号

![image-20250722143429183](pic/image-20250722143429183.png)

##### 正常情况

**发送方发送一个数据帧`Data1`，随后接收方接收到`Data1`，接收方的滑动窗口后移，然后发送一个确认帧`ACK1`，发送方接收到确认帧`ACK1`之后滑动窗口后移进行后续数据帧的发送**

![image-20250722144044801](pic/image-20250722144044801.png)

##### 数据帧丢失

**发送方发送`数据帧`时会同时设置一个计时器，若`数据帧`因网络噪声等原因丢失导致接收方没有收到`数据帧`，此时计时器会因长时间没收到`确认帧`而再次发送`数据帧`，直到发送方收到`确认帧`才会窗口后移进行后续发送。**

![image-20250722144934025](pic/image-20250722144934025.png)

##### 确认帧丢失

**发送方发送`数据帧1`，接收方接收到`数据帧1`，接收方的窗口后移，与此同时发送一个`确认帧1`。若因网络原因导致`确认帧1`丢失，导致发送方计时器超时，发送方会再次发送`数据帧1`，因为接收方需要的是`数据帧2`且已经接收过了`数据帧1`，所以接收方会丢弃`数据帧1`并再次给发送方发送一个`确认帧1`**



*<b>帧受损</b>的情况和确认帧丢失的情况类似 ，就是接收方发现帧错误，随后丢弃帧，不返回确认帧*



![image-20250722144024570](pic/image-20250722144024570.png)

##### 给帧编号的原因

![image-20250722145856554](pic/image-20250722145856554.png)

##### 小结

![image-20250722150258954](pic/image-20250722150258954.png)

####  后退N帧协议(GBN)

**GBN：Go-Back-N**

![image-20250722150455799](pic/image-20250722150455799.png)

##### 正常情况

![image-20250722151604048](pic/image-20250722151604048.png)

##### 数据帧丢失

**在数据帧`E`传输时出现问题导致接收方没有收到`E`，但是发送方还会继续发送数据帧`F`,此时接收方收到窗口之外的帧`F`，直接丢弃并返回最后一个正确接收到的帧的确认帧`D`，随后发送方会从`D`之后的帧开始重新传**

![image-20250722151530950](pic/image-20250722151530950.png)

##### 确认帧丢失

**接收方接收到所有帧时会返回确认帧`ACK2`，但是因网络原因发送方没有收到`ACK2`，于是会重新发送帧`ABC`，此时接收方收到窗口之外的帧会返回最后一个正确收到的帧`C`的确认帧`ACK2`。发送方收到`ACK2`后得知`ABC`已经成功发送则会滑动窗口至后续帧**

![image-20250722151649403](pic/image-20250722151649403.png)

##### 为什么要Wt + Wr <= 2^n?

$$
W_T + W_R \leq 2^n
$$

![image-20250722152711736](pic/image-20250722152711736.png)

##### 小结

![image-20250722153126740](pic/image-20250722153126740.png)

#### 选择重传协议(SR)

**SR：Selective Repeat**

![image-20250722153654239](pic/image-20250722153654239.png)

![image-20250722154452338](pic/image-20250722154452338.png)

##### 正常境况

![image-20250722154558886](pic/image-20250722154558886.png)

##### 数据帧丢失

![image-20250722154906648](pic/image-20250722154906648.png)

![image-20250722154944582](pic/image-20250722154944582.png)

![image-20250722155004282](pic/image-20250722155004282.png)

![image-20250722155019276](pic/image-20250722155019276.png)

![image-20250722155035491](pic/image-20250722155035491.png)

##### 数据帧错误

![image-20250722155146944](pic/image-20250722155146944.png)

![image-20250722155300261](pic/image-20250722155300261.png)

![image-20250722155408098](pic/image-20250722155408098.png)

##### 确认帧丢失

![image-20250722155621085](pic/image-20250722155621085.png)

![image-20250722155649487](pic/image-20250722155649487.png)

![image-20250722155710658](pic/image-20250722155710658.png)

##### 为什么要Wt + Wr <= 2^n?

![image-20250722160017096](pic/image-20250722160017096.png)

![image-20250722160036865](pic/image-20250722160036865.png)

##### 小结

![image-20250722160055245](pic/image-20250722160055245.png)

#### 三种协议的信道利用率⭐

![image-20250722160247527](pic/image-20250722160247527.png)

##### S-W协议的信道利用率

![image-20250722161044803](pic/image-20250722161044803.png)

![image-20250722161157861](pic/image-20250722161157861.png)

![image-20250722161730656](pic/image-20250722161730656.png)

##### GBN，SR协议的信道利用率

![image-20250722162238441](pic/image-20250722162238441.png)

![image-20250722162456670](pic/image-20250722162456670.png)

![image-20250722164450605](pic/image-20250722164450605.png)



**滑动窗口协议**

![image-20250722165134191](pic/image-20250722165134191.png)

**ARQ协议，连续ARQ协议**

![image-20250722165253911](pic/image-20250722165253911.png)

![image-20250722170044116](pic/image-20250722170044116.png)

##### 小结

![image-20250722170101610](pic/image-20250722170101610.png)

## 第七天：7.25 [3.5.1.1-3.5.1.2]

### 4.介质访问控制

![image-20250725142139197](pic/image-20250725142139197.png)

![image-20250725142230436](pic/image-20250725142230436.png)

#### 信道划分

![image-20250725142423699](pic/image-20250725142423699.png)

##### 时分复用(TDM)

![image-20250725142803177](pic/image-20250725142803177.png)![image-20250725143130881](pic/image-20250725143130881.png)![image-20250725143317430](pic/image-20250725143317430.png)

##### 频分复用(FDM)

![image-20250725143904593](pic/image-20250725143904593.png)

![image-20250725144213530](pic/image-20250725144213530.png)

![image-20250725144428907](pic/image-20250725144428907.png)

##### 码分复用(CDM)

![image-20250725144725390](pic/image-20250725144725390.png)

![image-20250725144738304](pic/image-20250725144738304.png)![image-20250725145824068](pic/image-20250725145824068.png)

![image-20250725145806970](pic/image-20250725145806970.png)

##### 小结

![image-20250725150532780](pic/image-20250725150532780.png)

## 第八天：7.27 [3.5.2.1-3.5.3]

#### 随机访问

![image-20250727133333802](pic/image-20250727133333802.png)

##### ALOHA协议

**ALOHA：Additive Links On-line Hawaii Area(夏威夷地区在线附加链路)**

![image-20250727134629608](pic/image-20250727134629608.png)

**纯ALOHA**

![image-20250727134557300](pic/image-20250727134557300.png)

**时隙ALOHA**

![image-20250727134656064](pic/image-20250727134656064.png)

##### CSMA协议

**CSMA：Carrier Sense Multiple Access（载波侦听多路访问）**

![image-20250727135007980](pic/image-20250727135007980.png)

**1-坚持CSMA协议**

![image-20250727135559821](pic/image-20250727135559821.png)

**非坚持CSMA协议**

![image-20250727140154063](pic/image-20250727140154063.png)

**p-坚持CSMA协议**

![image-20250727140605318](pic/image-20250727140605318.png)

##### ALOHA和CSMA小结

![image-20250727140741956](pic/image-20250727140741956.png)

##### CSMA/CD协议

**CD：Collision Detection(冲突检测)**

![image-20250727141255159](pic/image-20250727141255159.png)

![image-20250727143103660](pic/image-20250727143103660.png)

**关于争用期**

![image-20250727144416851](pic/image-20250727144416851.png)

**关于最短帧长**

![image-20250727145456748](pic/image-20250727145456748.png)

![image-20250727145624878](pic/image-20250727145624878.png)

##### CSMA/CA协议

**CA：Collision Avoidance(冲突避免)**

![image-20250727150348689](pic/image-20250727150348689.png)

![image-20250727151045118](pic/image-20250727151045118.png)

**AP**

![image-20250727151517276](pic/image-20250727151517276.png)

![image-20250727152215359](pic/image-20250727152215359.png)

![image-20250727153523049](pic/image-20250727153523049.png)

**信道预约机制**

![image-20250727154003441](pic/image-20250727154003441.png)

![image-20250727153950446](pic/image-20250727153950446.png)

**例题**

![image-20250727154600027](pic/image-20250727154600027.png)

![image-20250727154613883](pic/image-20250727154613883.png)

#### 轮询访问

![image-20250727161805943](pic/image-20250727161805943.png)![image-20250727162447304](pic/image-20250727162447304.png)

![image-20250727161735300](pic/image-20250727161735300.png)

##### MAU：令牌环网的集中控制站

![image-20250727162016769](pic/image-20250727162016769.png)

![image-20250727162004687](pic/image-20250727162004687.png)

##### 小结

![image-20250727162333071](pic/image-20250727162333071.png)

## 第九天：7.30 [3.6.0-3.8]

### 5.局域网与IEEE 802

#### IEEE组织

![image-20250729203540111](pic/image-20250729203540111.png)



#### 局域网(LAN)

**LAN：Local Area Network**

<img src="pic/image-20250729210636253.png" alt="image-20250729210636253" style="zoom:200%;" />

##### 有线局域网(IEEEE 802.3)

![image-20250729211741318](pic/image-20250729211741318.png)

![image-20250729211322052](pic/image-20250729211322052.png)

**同轴电缆-半双工**

![image-20250729211450010](pic/image-20250729211450010.png)

**双绞线-半双工&全双工**

![image-20250729211628248](pic/image-20250729211628248.png)

![image-20250729211834199](pic/image-20250729211834199.png)

![image-20250729213049799](pic/image-20250729213049799.png)

![image-20250729214410297](pic/image-20250729214410297.png)

![image-20250729214658416](pic/image-20250729214658416.png)

![image-20250729215007896](pic/image-20250729215007896.png)

##### VLAN(IEEE 802.1Q)

![image-20250729215504256](pic/image-20250729215504256.png)

![image-20250730134450847](pic/image-20250730134450847.png)

![image-20250730134841685](pic/image-20250730134841685.png)

![image-20250730135320199](pic/image-20250730135320199.png)

![image-20250730135455018](pic/image-20250730135455018.png)

![image-20250730135725571](pic/image-20250730135725571.png)

**802.1Q帧的结构**

![image-20250730135927491](pic/image-20250730135927491.png)

**小结**

![image-20250730140550515](pic/image-20250730140550515.png)

##### 无线局域网(IEEEE 802.11)

![image-20250730140946908](pic/image-20250730140946908.png)

**网桥(Portal)**

![image-20250730142208882](pic/image-20250730142208882.png)

**802.11无线局域网的基本概念**

![image-20250730142158023](pic/image-20250730142158023.png)

![image-20250730142359746](pic/image-20250730142359746.png)

**802.11帧**

![image-20250730142652661](pic/image-20250730142652661.png)

![image-20250730144950821](pic/image-20250730144950821.png)

**例题**

![image-20250730145150098](pic/image-20250730145150098.png)

**小结**

![image-20250730145554148](pic/image-20250730145554148.png)

***拓展**

![image-20250730150330830](pic/image-20250730150330830.png)

#### 广域网(WAN)

没有

#### 以太网交换机

##### 自学习功能

![image-20250730153105436](pic/image-20250730153105436.png)

##### 两种交换方式

![image-20250730153649682](pic/image-20250730153649682.png)

![image-20250730153810542](pic/image-20250730153810542.png)

##### 小结

![image-20250730153913905](pic/image-20250730153913905.png)

# 第四章：网络层

## 第十天：8.1 [4.1-4.2.1]

### 0.网络层的功能

![image-20250801152607662](pic/image-20250801152607662.png)

![image-20250801145812701](pic/image-20250801145812701.png)![image-20250801150456041](pic/image-20250801150456041.png)

### 1.IPv4分组

#### 各协议之间的服务关系

![image-20250801154250368](pic/image-20250801154250368.png)

#### IP数据报(IP分组)的格式⭐

##### 第一行

![image-20250801154907442](pic/image-20250801154907442.png)

![image-20250801155203732](pic/image-20250801155203732.png)

**IP数据报的"分片"**

![image-20250801155821927](pic/image-20250801155821927.png)

![image-20250801160640114](pic/image-20250801160640114.png)

![image-20250801160806952](pic/image-20250801160806952.png)

##### 第二行

![image-20250801163745356](pic/image-20250801163745356.png)

![image-20250801162705403](pic/image-20250801162705403.png)

![image-20250801163051760](pic/image-20250801163051760.png)

##### 第三行

![image-20250801163728778](pic/image-20250801163728778.png)

##### 第四，五行

![image-20250801163909064](pic/image-20250801163909064.png)

#### 小结

![image-20250801164216350](pic/image-20250801164216350.png)

## 第十一天：8.3 [4.2.2-4.2.3]

### 2.IPv4地址的发展

![image-20250804154920202](pic/image-20250804154920202.png)

#### 1.最初的IP地址分类方案

![image-20250803135212858](pic/image-20250803135212858.png)

![image-20250803140032234](pic/image-20250803140032234.png)

![image-20250803142210316](pic/image-20250803142210316.png)

#### 特殊的IP地址

![image-20250803143546268](pic/image-20250803143546268.png)

#### 2.子网划分与子网掩码

**未使用子网划分**

![image-20250803160656190](pic/image-20250803160656190.png)

**使用子网划分**

![image-20250803160640548](pic/image-20250803160640548.png)

##### 小结

![image-20250803160952311](pic/image-20250803160952311.png)

##### 主机发送IP数据报的过程

![image-20250803161021680](pic/image-20250803161021680.png)

##### 路由器转发一个IP数据报的过程

![image-20250803161104331](pic/image-20250803161104331.png)

##### 子网掩码的CIDR记法

![image-20250803161250336](pic/image-20250803161250336.png)

## 第十二天：8.4 [4.2.4-4.2.7]

#### 3.无分类编址 CIDR

##### 总览

![image-20250804142613441](pic/image-20250804142613441.png)

##### 无分类编址 CIDR

![image-20250804143134144](pic/image-20250804143134144.png)

##### 定长子网划分和变长子网划分

![image-20250804143841466](pic/image-20250804143841466.png)

![image-20250804143850224](pic/image-20250804143850224.png)

![image-20250804145129198](pic/image-20250804145129198.png)

###### 例题

![image-20250804150050692](pic/image-20250804150050692.png)

![image-20250804150912013](pic/image-20250804150912013.png)

##### 小结

![image-20250804151122347](pic/image-20250804151122347.png)

##### 路由聚合

![image-20250804152307766](pic/image-20250804152307766.png)

###### 最长前缀匹配原则

![image-20250804152809791](pic/image-20250804152809791.png)

##### 骚图

![image-20250804154621291](pic/image-20250804154621291.png)

#### 4.NAT 网络地址转换

**NAT：Network Address Translation**

##### 端口号

![image-20250804155542820](pic/image-20250804155542820.png)

##### 要点

![image-20250804160345027](pic/image-20250804160345027.png)

##### 骚图

![image-20250804163642170](pic/image-20250804163642170.png)

#### ARP 地址解析协议

**ARP：Address Resolution Protocol**

![image-20250804170746284](pic/image-20250804170746284.png)

##### 小结

![image-20250804170340702](pic/image-20250804170340702.png)

![image-20250804170445958](pic/image-20250804170445958.png)

##### *拓展：ARP分组的格式

![image-20250804170907128](pic/image-20250804170907128.png)

## 第十三天：8.7 [4.2.8-4.4.2]

#### DHCP 动态主机配置协议

**DHCP：Dynamic Host Configuration Protocol**

##### DHCP在应用层

![image-20250807132049066](pic/image-20250807132049066.png)

##### DHCP工作原理

![image-20250807135704328](pic/image-20250807135704328.png)

##### 小结

![image-20250807140012873](pic/image-20250807140012873.png)

#### ICMP 网际控制报文协议

**ICMP：Internet Control Message Protocol**

##### ICMP在网络层

![image-20250807140322087](pic/image-20250807140322087.png)

##### 差错报告报文

###### 终点不可达

![image-20250807141547428](pic/image-20250807141547428.png)

###### 时间超时

![image-20250807141853723](pic/image-20250807141853723.png)![image-20250807142104722](pic/image-20250807142104722.png)

###### 参数问题

![image-20250807142247551](pic/image-20250807142247551.png)

###### 改变路由(重定向)

![image-20250807142554796](pic/image-20250807142554796.png)

###### *源点抑制

![image-20250807142832061](pic/image-20250807142832061.png)

##### 询问报文

###### 回送请求，回送回答

![image-20250807143553044](pic/image-20250807143553044.png)

![image-20250807143623668](pic/image-20250807143623668.png)

###### 时间戳请求，时间戳回答

![image-20250807143952076](pic/image-20250807143952076.png)

###### 小结

![image-20250807144614974](pic/image-20250807144614974.png)

##### traceroute(tracert)

**Windows用tracert**

![image-20250807150510470](pic/image-20250807150510470.png)

### 3.IPv6

#### 从IPv4到IPv6

![image-20250807151542632](pic/image-20250807151542632.png)

#### IPv6的冒号十六进制记法

![image-20250807151814512](pic/image-20250807151814512.png)

#### IPv6地址压缩记法

![image-20250807152318345](pic/image-20250807152318345.png)

##### 例题

![image-20250807152547524](pic/image-20250807152547524.png)

![image-20250807152728419](pic/image-20250807152728419.png)

![image-20250807152822767](pic/image-20250807152822767.png)

#### IPv6地址资源的分配

![image-20250807153039661](pic/image-20250807153039661.png)![image-20250807153558903](pic/image-20250807153558903.png)

![image-20250807154110038](pic/image-20250807154110038.png)

#### IPv6地址的分类

![image-20250807155057993](pic/image-20250807155057993.png)

##### 例题

![image-20250807155320787](pic/image-20250807155320787.png)

#### 小结

![image-20250807155716182](pic/image-20250807155716182.png)

### 4.路由算法

#### 总览

![image-20250807155856691](pic/image-20250807155856691.png)

#### 路由算法，路由协议的关系

![image-20250807160351894](pic/image-20250807160351894.png)

#### 路由算法的分类

![image-20250807160626715](pic/image-20250807160626715.png)

##### 距离-向量路由算法

![image-20250807162718100](pic/image-20250807162718100.png)

![image-20250807161359533](pic/image-20250807161359533.png)

![image-20250807162031529](pic/image-20250807162031529.png)

###### 例题

![image-20250807162538248](pic/image-20250807162538248.png)

##### 链路状态路由算法

![image-20250807163214331](pic/image-20250807163214331.png)

![image-20250807163338708](pic/image-20250807163338708.png)

#### 小结

![image-20250807163458871](pic/image-20250807163458871.png)

### 5.分层次的路由协议

![image-20250807163944564](pic/image-20250807163944564.png)

![image-20250807164309020](pic/image-20250807164309020.png)

#### 关于自治系统的一些拓展

![image-20250807165014975](pic/image-20250807165014975.png)

![image-20250807165207242](pic/image-20250807165207242.png)

#### 小结

![image-20250807165304020](pic/image-20250807165304020.png)

### 6.RIP路由算法

*RIP:Routing Information Protocol路由信息协议*

#### RIP的基本概念

![image-20251021170942017](pic/image-20251021170942017.png)

#### RIP的规定

![image-20251021171020108](pic/image-20251021171020108.png)

#### RIP的工作过程

##### 0时刻

![image-20251021171151039](pic/image-20251021171151039.png)

![image-20251021171239133](pic/image-20251021171239133.png)

##### 30时刻

![image-20251021171302353](pic/image-20251021171302353.png)

##### 60时刻

![image-20251021171351492](pic/image-20251021171351492.png)

##### 90时刻(已收敛)

![image-20251021171415492](pic/image-20251021171415492.png)

![image-20251021171121132](pic/image-20251021171121132.png)

![image-20251021171048252](pic/image-20251021171048252.png)

### 7.OSPF路由算法

*OSPF:Open Shortest Path First开放最短路径优先协议*

#### OSPF的基本概念

![image-20251021172433732](pic/image-20251021172433732.png)

#### 基本原理

![image-20251021174922237](pic/image-20251021174922237.png)

![image-20251021174949526](pic/image-20251021174949526.png)

#### 其他特点

##### 自定义代价

![image-20251021175015805](pic/image-20251021175015805.png)

##### 多路径

![image-20251021175107300](pic/image-20251021175107300.png)

##### 鉴别黑路由

![image-20251021175123227](pic/image-20251021175123227.png)

##### 支持子网划分和无分类编址

![image-20251021175135421](pic/image-20251021175135421.png)

##### 洪范状态序号

![image-20251021175153843](pic/image-20251021175153843.png)

![image-20251021175206439](pic/image-20251021175206439.png)

#### 小结

![image-20251021175413181](pic/image-20251021175413181.png)

## 第十四天：8.13 [5.1-5.2.2]

# 第五章：传输层

### 0.传输层概述

#### 端口号的概念

![image-20250813133733493](pic/image-20250813133733493.png)

#### 进程，端口号，传输层协议之间的关系

![image-20250813134905034](pic/image-20250813134905034.png)

#### 熟知端口号

![image-20250813135644497](pic/image-20250813135644497.png)

****

#### 有连接的传输VS无连接的传输

![image-20250813140339459](pic/image-20250813140339459.png)

#### 可靠传输VS不可靠传输

**猜测：有连接中能分为可靠传输和不可靠传输，有`收到回复`认为是可靠传输**

****

![image-20250813140709443](pic/image-20250813140709443.png)

#### 概述

![image-20250813141646767](pic/image-20250813141646767.png)

### 1.UDP

#### UDP协议 UDP数据报 UDP首部

![image-20250813143213600](pic/image-20250813143213600.png)

#### UDP数据格式

![image-20250813143834249](pic/image-20250813143834249.png)

##### 小结

![image-20250813144348946](pic/image-20250813144348946.png)

#### UDP检验

##### 一种新的差错检验方法

**把原始按16bit分，然后做加法得到中间结果，把这个中间结果取反就是16bit的校验和**

![image-20250813145155575](pic/image-20250813145155575.png)![image-20250813145208977](pic/image-20250813145208977.png)

##### UDP检验(发送方的传输层)

![image-20250813150514934](pic/image-20250813150514934.png)

##### UDP检验(发送方的传输层)

![image-20250813150820343](pic/image-20250813150820343.png)

##### 小结

![image-20250813151403641](pic/image-20250813151403641.png)

##### 补充

**UDP的校验和是伪首部+首部+数据部分，IP数据报的首部校验和是只有首部**

![image-20250813151658118](pic/image-20250813151658118.png)

## 第十五天：8.15 [5.3.1-5.3.3.2]

### 2.TCP

#### TCP协议框架

![image-20250815133553026](pic/image-20250815133553026.png)

![image-20250815134327830](pic/image-20250815134327830.png)

#### TCP报文段⭐

##### 序号(ack) 确认号(ack_seq) ACK

![image-20250815135350017](pic/image-20250815135350017.png)

##### 数据偏移 保留 填充

**数据偏移表示的是TCP首部的长度，其后的保留字段没什么用** 

![image-20250815135900630](pic/image-20250815135900630.png)

##### *URG PSH RST

![image-20250815140955493](pic/image-20250815140955493.png)

##### SYN FIN

![image-20250815141447775](pic/image-20250815141447775.png)

##### 窗口

![image-20250815142022331](pic/image-20250815142022331.png)

![image-20250815142011449](pic/image-20250815142011449.png)

##### *校验和

![image-20250815142156268](pic/image-20250815142156268.png)

##### 选项->MSS

![image-20250815142808502](pic/image-20250815142808502.png)

##### 小结

![image-20250815143114801](pic/image-20250815143114801.png)

#### TCP连接管理

##### 回顾：TCP首部

![image-20250815143450415](pic/image-20250815143450415.png)

##### 建立连接(三次握手)

![image-20250815150522990](pic/image-20250815150522990.png)

###### 符号位角度



![image-20250815144732794](pic/image-20250815144732794.png)



![image-20250815145723483](pic/image-20250815145723483.png)

例题

![image-20250815145625690](pic/image-20250815145625690.png)

###### TCP状态角度



**![image-20250815145922831](pic/image-20250815145922831.png)**

###### 耗时角度

![image-20250815150339044](pic/image-20250815150339044.png)

##### 释放连接(四次挥手)

###### 符号位角度

![image-20250815151109144](pic/image-20250815151109144.png)

###### TCP状态角度

![image-20250815151124562](pic/image-20250815151124562.png)

例题

![image-20250815151831014](pic/image-20250815151831014.png)

###### 耗时角度

![image-20250815152311313](pic/image-20250815152311313.png)

![image-20250815152528366](pic/image-20250815152528366.png)

例题

![image-20250815153107522](pic/image-20250815153107522.png)

##### 小结

![image-20250815153502350](pic/image-20250815153502350.png)

## 第十六天：8.18 [5.3.4-5.3.5]

#### TCP可靠传输，流量控制

##### 回顾：TCP首部的相关

![image-20250818144206439](pic/image-20250818144206439.png)

##### 重点体会：确认号，接收窗口大小

![image-20250818144546515](pic/image-20250818144546515.png)

##### 重点体会：累计确认

![image-20250818154200366](pic/image-20250818154200366.png)

##### 重点体会：捎带确认

![image-20250818154241074](pic/image-20250818154241074.png)

##### 重点体会：超时重传机制

![image-20250818154427754](pic/image-20250818154427754.png)![image-20250818154441103](pic/image-20250818154441103.png)

##### TCP传输的底层原理

![image-20250818150226916](pic/image-20250818150226916.png)

##### 一个端口可以建立多个TCP连接

![image-20250818150413201](pic/image-20250818150413201.png)

##### 快重传机制

![image-20250818160750974](pic/image-20250818160750974.png)

![image-20250818160802042](pic/image-20250818160802042.png)

###### 例题

![image-20250818161214505](pic/image-20250818161214505.png)

##### 小结

![image-20250818161314764](pic/image-20250818161314764.png)

![image-20250818154838958](pic/image-20250818154838958.png)

## 第十七天：8.19 [5.3.6]

#### TCP拥塞控制

##### TCP拥塞控制，TCP流量控制的区别与联系

![image-20250819133852325](pic/image-20250819133852325.png)

##### 拥塞控制的四种算法

![image-20250819133957937](pic/image-20250819133957937.png)

##### 拥塞控制考题特点

![image-20250819135030067](pic/image-20250819135030067.png)

##### 慢开始，拥塞避免⭐

![image-20250819140221957](pic/image-20250819140221957.png)

###### 例题

![image-20250819141618336](pic/image-20250819141618336.png)

![image-20250819142731081](pic/image-20250819142731081.png)

##### 快重传，快恢复

![image-20250819143727453](pic/image-20250819143727453.png)

![image-20250819143922641](pic/image-20250819143922641.png)

## 第十八天：8.23 [6.0-6.5.2]

# 第六章：应用层

### 0.应用层概述

![image-20250823132142105](pic/image-20250823132142105.png)

![image-20250823132244887](pic/image-20250823132244887.png)

### 1.网络应用模型

![image-20250823133223022](pic/image-20250823133223022.png)

#### C/S模型

![image-20250823134043112](pic/image-20250823134043112.png)

#### P2P模型

![image-20250823134558660](pic/image-20250823134558660.png)

### 2.DNS系统

![image-20250823135112206](pic/image-20250823135112206.png)

#### 域名

![image-20250823140404115](pic/image-20250823140404115.png)

#### 域名服务器

![image-20250823153645105](pic/image-20250823153645105.png)

![image-20250823142002956](pic/image-20250823142002956.png)

#### 域名解析过程

![image-20250823142312740](pic/image-20250823142312740.png)![image-20250823143733188](pic/image-20250823143733188.png)

### 3.FTP文件传输协议

![image-20250823144008873](pic/image-20250823144008873.png)![image-20250823144208711](pic/image-20250823144208711.png)

#### FTP工作原理

![image-20250823144657635](pic/image-20250823144657635.png)![image-20250823145321620](pic/image-20250823145321620.png)![image-20250823145425495](pic/image-20250823145425495.png)

### 4.电子邮件

![image-20250823145854573](pic/image-20250823145854573.png)

#### 组成结构

![image-20250823150455520](pic/image-20250823150455520.png)

![image-20250823150605951](pic/image-20250823150605951.png)

#### SMTP：简单邮件传送协议

![image-20250823150925407](pic/image-20250823150925407.png)![image-20250823151535642](pic/image-20250823151535642.png)

#### MIME：SMTP的扩充

![image-20250823151821076](pic/image-20250823151821076.png)

#### POP3：邮局协议

![image-20250823152028069](pic/image-20250823152028069.png)

#### IMAP：网际报文存取协议

![image-20250823152243553](pic/image-20250823152243553.png)

#### 基于万维网的电子邮件

![image-20250823152424353](pic/image-20250823152424353.png)

### 5.HTTP和万维网

#### 浏览网页的过程

![image-20250823161104573](pic/image-20250823161104573.png)

#### HTTP协议的工作方式

##### 非持续连接

![image-20250823161512157](pic/image-20250823161512157.png)![image-20250823161544800](pic/image-20250823161544800.png)

##### 持续连接：非流水线

![image-20250823161640247](pic/image-20250823161640247.png)

![image-20250823161657159](pic/image-20250823161657159.png)

##### 持续连接：流水线

![image-20250823161715940](pic/image-20250823161715940.png)

##### 小结

![image-20250823162227812](pic/image-20250823162227812.png)

#### HTTP报文格式

![image-20250823163854785](pic/image-20250823163854785.png)

![image-20250823164031966](pic/image-20250823164031966.png)

##### 例题

![image-20250823164419843](pic/image-20250823164419843.png)

##### 小结

![image-20250823164724416](pic/image-20250823164724416.png)

# 最后一页

![image-20250823164806487](pic/image-20250823164806487.png)