第三章学习笔记：HTTP2协议

tcp/Web 协议详解与抓包实战/3、HTTP2协议.md

@@ -0,0 +1,349 @@
+> [TOC]
+
+# 1、HTTP/1.1 发展中遇到的问题
+
+## 1.1、发生的变化
+
+![image-20220813224604630](assets/image-20220813224604630.png)
+
+## 1.2、高延迟问题
+
+![image-20220813224625917](assets/image-20220813224625917.png)
+
+![image-20220813224836311](assets/image-20220813224836311.png)
+
+## 1.3、巨大的头部
+
+![image-20220813225004647](assets/image-20220813225004647.png)
+
+## 1.4、HTTP1.1的优化
+
+![image-20220813225037932](assets/image-20220813225037932.png)
+
+## 1.5、HTTP/1.1 不支持服务器推送消息
+
+![image-20220813225126902](assets/image-20220813225126902.png)
+
+# 2、HTTP2特征概述
+
+## 2.1、提出背景
+
+![image-20220813225242683](assets/image-20220813225242683.png)
+
+* http2协议可以在http协议下，也可以在TLS-SSL协议下使用。
+* 浏览器强制要求HTTP2只能被HTTPS解析，也就是使用TLS-SSL协议。
+
+## 2.2、特性
+
+![image-20220813225444351](assets/image-20220813225444351.png)
+
+![image-20220813225530773](assets/image-20220813225530773.png)
+
+# 3、在TCP上从HTTP1升级到HTTP2
+
+## 3.1、HTTP/2 是不是必须基于TLS/SSL 协议？
+
+![image-20220816210600245](assets/image-20220816210600245.png)
+
+## 3.2、h2与h2c
+
+![image-20220816210746090](assets/image-20220816210746090.png)
+
+## 3.3、H2C：不使用 TLS 协议进行协议升级
+
+![image-20220816213310417](assets/image-20220816213310417.png)
+
+![image-20220816213409707](assets/image-20220816213409707.png)
+
+# 4、h2如何建立会话？
+
+## 4.1、通讯过程
+
+![image-20220816213628014](assets/image-20220816213628014.png)
+
+![image-20220816213640440](assets/image-20220816213640440.png)
+
+## 4.2、服务器端选择协议
+
+![image-20220816213815311](assets/image-20220816213815311.png)
+
+# 5、Stream、Message、Frame 间的关系
+
+## 5.1、定义
+
+![image-20220816214002799](assets/image-20220816214002799.png)
+
+## 5.2、Stream、Message、Frame 间的关系
+
+![image-20220816214249616](assets/image-20220816214249616.png)
+
+![image-20220816214702279](assets/image-20220816214702279.png)
+
+## 5.3、传输中无序
+
+![image-20220816214729430](assets/image-20220816214729430.png)
+
+* 同一个stream必须是有序的
+* 跨越stream可以是无序的
+
+![image-20220816214902643](assets/image-20220816214902643.png)
+
+# 6、帧格式：Stream流ID的作用
+
+## 6.1、对比websocket
+
+![image-20220816215016793](assets/image-20220816215016793.png)
+
+![image-20220816215110251](assets/image-20220816215110251.png)
+
+## 6.2、作用
+
+![image-20220816215232321](assets/image-20220816215232321.png)
+
+![image-20220816215240030](assets/image-20220816215240030.png)
+
+![image-20220816215249933](assets/image-20220816215249933.png)
+
+![image-20220816215256014](assets/image-20220816215256014.png)
+
+# 7、帧格式：帧类型及设置帧的子类型
+
+## 7.1、定义
+
+![image-20220816215731117](assets/image-20220816215731117.png)
+
+* 帧长度
+* 帧类型
+* 帧标记
+* 帧的id
+* 帧数据
+
+## 7.2、帧的类型
+
+![image-20220816215758282](assets/image-20220816215758282.png)
+
+![image-20220816215805092](assets/image-20220816215805092.png)
+
+## 7.3、setting设置帧
+
+* 可以设置多个key-value
+
+![image-20220816215958065](assets/image-20220816215958065.png)
+
+![image-20220816220048816](assets/image-20220816220048816.png)
+
+# 8、HPACK 如何减少HTTP 头部的大小？
+
+## 8.1、定义
+
+![image-20220816220720751](assets/image-20220816220720751.png)
+
+## 8.2、静态字典
+
+![image-20220816220747802](assets/image-20220816220747802.png)
+
+![image-20220816220927312](assets/image-20220816220927312.png)
+
+![image-20220816220843281](assets/image-20220816220843281.png)
+
+## 8.3、动态字典
+
+动态表包含以**先进先出**的顺序维护的 header 字段列表。动态表中的第一个条目和最新条目在最低索引处，而动态表的最旧条目在最高索引处。
+
+动态表最初是空的。当每个 header 块被解压缩时，将添加条目。动态表可以包含重复的条目（即，具有相同名称和相同值的条目）。因此，解码器不得将重复的条目视为错误。
+
+编码器决定如何更新动态表，因此可以控制动态表使用多少内存。为了限制解码器的存储需求，动态表的 size 受到严格限制。
+
+解码器在处理 header 字段表示列表时更新动态表。
+
+# 9、HPACK 中如何使用Huffman树编码？
+
+## 9.1、原理
+
+![image-20220816221321050](assets/image-20220816221321050.png)
+
+ ## 9.2、构造过程
+
+![image-20220816221558274](assets/image-20220816221558274.png)
+
+# 10、HPACK 中整型数字的编码
+
+这里编码的是索引位置，即使下文11章节所说的索引表下标
+
+## 10.1、小于31
+
+![image-20220816230238907](assets/image-20220816230238907.png)
+
+## 10.2、大于31
+
+![image-20220816230356798](assets/image-20220816230356798.png)
+
+![image-20220816230421388](assets/image-20220816230421388.png)
+
+![image-20220816230523265](assets/image-20220816230523265.png)
+
+# 11、HPACK 中HEADER 的编码格式
+
+## 11.1、HEADER帧的格式
+
+![image-20220816230631593](assets/image-20220816230631593.png)
+
+![image-20220816230701522](assets/image-20220816230701522.png)
+
+## 11.2、动态表
+
+![image-20220816230731894](assets/image-20220816230731894.png)
+
+## 11.3、字面编码
+
+![image-20220816230813032](assets/image-20220816230813032.png)
+
+## 11.4、格式
+
+![image-20220816230857683](assets/image-20220816230857683.png)
+
+![image-20220816231045912](assets/image-20220816231045912.png)
+
+![image-20220816231317892](assets/image-20220816231317892.png)
+
+![image-20220816231327159](assets/image-20220816231327159.png)
+
+![image-20220816231628647](assets/image-20220816231628647.png)
+
+![image-20220816231647378](assets/image-20220816231647378.png)
+
+![image-20220816231657774](assets/image-20220816231657774.png)
+
+## 11.5、动态表控制
+
+![image-20220816231728498](assets/image-20220816231728498.png)
+
+# 12、服务器端的主动消息推送
+
+## 12.1、价值
+
+![image-20220816232717019](assets/image-20220816232717019.png)
+
+![image-20220816232729367](assets/image-20220816232729367.png)
+
+![image-20220816232913454](assets/image-20220816232913454.png)
+
+## 12.2、帧格式
+
+![image-20220816233032609](assets/image-20220816233032609.png)
+
+## 12.3 可以禁用
+
+![image-20220816233326240](assets/image-20220816233326240.png)
+
+# 13、stream的状态变迁
+
+## 13.1、stream特性
+
+![image-20220816233654866](assets/image-20220816233654866.png)
+
+## 13.2、message特性
+
+![image-20220816233732465](assets/image-20220816233732465.png)
+
+## 13.3、发送例子
+
+![image-20220816233807759](assets/image-20220816233807759.png)
+
+![image-20220816233818110](assets/image-20220816233818110.png)
+
+## 13.4、stream状态的变化
+
+![image-20220816233905535](assets/image-20220816233905535.png)
+
+# 14、RST_STREAM帧及常见错误码
+
+## 14.1、定义
+
+![image-20220816234215070](assets/image-20220816234215070.png)
+
+## 14.2、常见的错误码
+
+![image-20220816234234494](assets/image-20220816234234494.png)
+
+![image-20220816234241382](assets/image-20220816234241382.png)
+
+![image-20220816234247670](assets/image-20220816234247670.png)
+
+# 15、不同请求的优先级
+
+## 15.1、Priority 优先级设置帧
+
+![image-20220816234332719](assets/image-20220816234332719.png)
+
+## 15.2、优先级
+
+![image-20220816234537477](assets/image-20220816234537477.png)
+
+![image-20220816234913183](assets/image-20220816234913183.png)
+
+* exclusive：是否独占
+
+# 16、不同于 TCP 的流量控制
+
+## 16.1、为什么需要？
+
+![image-20220817205611078](assets/image-20220817205611078.png)
+
+![image-20220817210023672](assets/image-20220817210023672.png)
+
+## 16.2、如何进行？
+
+![image-20220817210119059](assets/image-20220817210119059.png)
+
+## 16.3、流量控制帧
+
+![image-20220817210326885](assets/image-20220817210326885.png)
+
+## 16.4、流控制窗口
+
+![image-20220817210516483](assets/image-20220817210516483.png)
+
+## 16.5、并发流
+
+![image-20220817210535722](assets/image-20220817210535722.png)
+
+# 17、HTTP/2 的问题
+
+## 17.1、TCP 以及 TCP+TLS 建链握手过多的问题
+
+![image-20220817210751019](assets/image-20220817210751019.png)
+
+## 17.2、多路复用与 TCP 的队头阻塞问题
+
+![image-20220817210827738](assets/image-20220817210827738.png)
+
+## 17.3、TCP的问题
+
+![image-20220817210845887](assets/image-20220817210845887.png)
+
+# 18、七层负载均衡做了些什么？
+
+## 18.1、四层负载均衡
+
+![image-20220817211116912](assets/image-20220817211116912.png)
+
+## 18.2、七层负载均衡协议转换举例
+
+![image-20220817211157133](assets/image-20220817211157133.png)
+
+## 18.3、协议转换
+
+![image-20220817211448937](assets/image-20220817211448937.png)
+
+## 18.4、WAF 防火墙
+
+![image-20220817211544225](assets/image-20220817211544225.png)
+
+## 18.5、负载均衡算法
+
+![image-20220817211644003](assets/image-20220817211644003.png)
+
+## 18.6、缓存功能
+
+![image-20220817211702271](assets/image-20220817211702271.png)