本书以易于理解、方便上手的方式，使用贴近用户的实例来解释 HTTP/2 协议。本书首先介绍为什么要升级到 HTTP/2 以及升级的方法 ；然后逐步深入，详细解释了 HTTP/2 协议本身及其对Web 开发的影响 ；之后介绍了部分高级内容，如流状态、HPACK 等 ；最后探讨了 HTTP 的未来。本书对于 Web 开发者和运维工程师来说是一本很有价值的参考书。

Barry Pollard 是一位专业软件开发者，在开发、支持软件和基础架构方向拥有近20年的行业经验。他对Web技术，性能调优，安全以及技术实践非常感兴趣。他的博客是https://www.tunetheweb.com，您也可以在Twitter上找到他@tunetheweb。
郑维智，Akamai公司高级企业架构师，专注于公司的主要客户及战略合作伙伴。他也是Web性能优化和HTTP/2的布道者，为Akamai的产品开发团队提供技术建议和客户反馈。

第1部分　向HTTP/2靠拢
第1章　万维网与HTTP....................................................................................................3
1.1　万维网的原理 .......................................................................................................3
1.1.1　因特网与万维网 .......................................................................................4
1.1.2　打开网页时会发生什么 ...........................................................................5
1.2　什么是HTTP .........................................................................................................9
1.3　HTTP的语法和历史 ...........................................................................................16
1.3.1　HTTP/0.9 .................................................................................................16
1.3.2　HTTP/1.0 .................................................................................................17
1.3.3　HTTP/1.1 .................................................................................................23
1.4　HTTPS简介 .........................................................................................................29
1.5　查看、发送和接收HTTP消息的工具 ...............................................................32
1.5.1　浏览器开发者工具 .................................................................................32
1.5.2　发送 HTTP 请求 .....................................................................................34
1.5.3　其他工具 .................................................................................................35
总结 ..............................................................................................................................36
第2章　通向HTTP/2之路...............................................................................................37
2.1　HTTP/1.1和当前的万维网 .................................................................................38
2.1.1　HTTP/1.1 根本的性能问题 ....................................................................40
2.1.2　HTTP/1.1 管道化 ....................................................................................42
2.1.3　网络性能瀑布流图 .................................................................................43
2.2　解决HTTP/1.1性能问题的方案 .........................................................................45
2.2.1　使用多个 HTTP 连接 .............................................................................46
2.2.2　发送更少的请求 .....................................................................................49
2.2.3　HTTP/1 性能优化总结 ...........................................................................50
2.3　HTTP/1.1的其他问题 .........................................................................................50
2.4　实际案例 .............................................................................................................51
2.4.1　示例网站 1: amazon.com .......................................................................52
2.4.2　示例网站 2 ： imgur.com .........................................................................56
2.4.3　这个问题究竟有多严重 .........................................................................57
2.5　从HTTP/1.1到HTTP/2 ........................................................................................58
2.5.1　SPDY .......................................................................................................58
2.5.2　HTTP/2 ....................................................................................................61
2.6　HTTP/2对Web性能的影响 .................................................................................62
2.6.1　展示 HTTP/2 能力的绝佳示例 ..............................................................62
2.6.2　对 HTTP/2 提升性能的期望 ..................................................................65
2.6.3　HTTP/1.1 的一些性能变通方法可能是反模式 ....................................70
总结 ..............................................................................................................................70
第3章　升级到HTTP/2. ..................................................................................................72
3.1　HTTP/2的支持 ....................................................................................................72
3.1.1　浏览器对 HTTP/2 的支持 ......................................................................73
3.1.2　服务器对 HTTP/2 的支持 ......................................................................78
3.1.3　兼容不支持 HTTP/2 的情况 ..................................................................80
3.2　网站开启HTTP/2的方法 ....................................................................................81
3.2.1　在 Web 服务器上开启 HTTP/2..............................................................81
3.2.2　反向代理实现 HTTP/2 ...........................................................................84
3.2.3　通过 CDN 实现 HTTP/2 ........................................................................87
3.2.4　小结 .........................................................................................................89
3.3　常见问题 .............................................................................................................89
总结 ..............................................................................................................................93
第2部分　使用HTTP/2
第4章　HTTP/2协议基础...............................................................................................97
4.1　为什么是HTTP/2而不是HTTP/1.2 ....................................................................97
4.1.1　使用二进制格式替换文本格式 .............................................................99
4.1.2　多路复用代替同步请求 .......................................................................100
4.1.3　流的优先级和流量控制 .......................................................................103
4.1.4　首部压缩 ...............................................................................................104
4.1.5　服务端推送 ...........................................................................................105
4.2　如何创建一个HTTP/2连接 ..............................................................................105
4.2.1　使用 HTTPS 协商 .................................................................................106
4.2.2　使用 HTTP upgrade 首部 .....................................................................113
4.2.3　使用先验知识 .......................................................................................116
4.2.4　HTTP Alternative Services ....................................................................117
4.2.5　HTTP/2 前奏消息 .................................................................................117
4.3　HTTP/2帧 ..........................................................................................................119
4.3.1　查看 HTTP/2 帧 ....................................................................................119
4.3.2　HTTP/2 帧数据格式 .............................................................................126
4.3.3　HTTP/2 消息流示例 .............................................................................128
4.3.4　其他帧 ...................................................................................................143
总结 ............................................................................................................................148
第5章　实现HTTP/2推送.............................................................................................149
5.1　什么是HTTP/2服务端推送 ..............................................................................149
5.2　如何推送 ...........................................................................................................153
5.2.1　使用 HTTP link 首部推送 ....................................................................153
5.2.2　查看 HTTP/2 推送 ................................................................................156
5.2.3　使用 link 首部从下游系统推送 ...........................................................159
5.2.4　更早推送 ...............................................................................................162
5.2.5　使用其他方式推送 ...............................................................................168
5.3　HTTP/2推送在浏览器中如何运作 ..................................................................171
5.3.1　查看推送缓存如何工作 .......................................................................172
5.3.2　使用 RST_STREAM 拒绝推送 ...........................................................175
5.4　如何实现条件推送 ...........................................................................................176
5.4.1　在服务端跟踪推送的资源 ...................................................................176
5.4.2　使用 HTTP 条件请求 ...........................................................................176
5.4.3　使用基于 cookie 的推送 ......................................................................177
5.4.4　使用缓存摘要 .......................................................................................178
5.5　推送什么 ...........................................................................................................179
5.5.1　你能推送什么 .......................................................................................179
5.5.2　应该推送什么 .......................................................................................180
5.5.3　自动化推送 ...........................................................................................181
5.6　HTTP/2推送常见问题 ......................................................................................182
5.7　HTTP/2推送对性能的影响 ..............................................................................184
5.8　对比推送和预加载 ...........................................................................................185
5.9　HTTP/2推送的其他应用场景 ..........................................................................188
总结 ............................................................................................................................190
第6章　HTTP/2优化....................................................................................................192
6.1　HTTP/2对Web开发者的影响 ...........................................................................192
6.2　一些HTTP/1.1优化方法是否成了反模式 .......................................................194
6.2.1　HTTP/2 请求依然有开销 .....................................................................194
6.2.2　HTTP/2 不是没有限制 .........................................................................197
6.2.3　越大的资源压缩越有效 .......................................................................199
6.2.4　带宽限制和资源竞争 ...........................................................................201
6.2.5　域名分片 ...............................................................................................202
6.2.6　内联资源 ...............................................................................................203
6.2.7　总结 .......................................................................................................203
6.3　在HTTP/2下依然有效的性能优化技术 ..........................................................204
6.3.1　减少要传输的数据量 ...........................................................................204
6.3.2　使用缓存防止重复发送数据 ...............................................................211
6.3.3　Service Worker 可以大幅减少网络加载 .............................................215
6.3.4　不发送不需要的内容 ...........................................................................216
6.3.5　HTTP 资源暗示 ....................................................................................217
6.3.6　减少最后 1 公里的延迟 .......................................................................219
6.3.7　优化 HTTPS ..........................................................................................219
6.3.8　和 HTTP 无关的性能优化技术 ...........................................................222
6.4　同时对HTTP/1.1和HTTP/2做优化 ..................................................................222
6.4.1　计算 HTTP/2 流量 ................................................................................223
6.4.2　在服务端检测 HTTP/2 支持 ................................................................224
6.4.3　在客户端检测 HTTP/2 支持 ................................................................228
6.4.4　连接合并 ...............................................................................................228
6.4.5　还要为 HTTP/1.1 的用户优化多久 .....................................................230
总结 ............................................................................................................................231
第3部分　HTTP/2进阶
第7章　高级HTTP/2概念.............................................................................................235
7.1　流状态 ...............................................................................................................236
7.2　流量控制 ...........................................................................................................239
7.2.1　流量控制示例 .......................................................................................240
7.2.2　在服务器上设置流量控制 ...................................................................244
7.3　流优先级 ...........................................................................................................244
7.3.1　流依赖关系 ...........................................................................................245
7.3.2　流权重 ...................................................................................................248
7.3.3　为什么优先级策略如此复杂 ...............................................................251
7.3.4　Web 服务器和浏览器中的优先级策略 ...............................................252
7.4　HTTP/2一致性测试 ..........................................................................................255
7.4.1　服务端一致性测试 ...............................................................................255
7.4.2　客户端一致性测试 ...............................................................................258
总结 ............................................................................................................................258
第8章　HPACK首部压缩.............................................................................................259
8.1　为什么需要首部压缩 .......................................................................................259
8.2　压缩的运作方式 ...............................................................................................261
8.2.1　查表法 ...................................................................................................262
8.2.2　更高效的编码技术 ...............................................................................263
8.2.3　Lookback( 反查 ) 压缩 .........................................................................264
8.3　HTTP正文压缩 .................................................................................................265
8.4　HTTP/2的HPACK首部压缩 .............................................................................267
8.4.1　HPACK 静态表 .....................................................................................268
8.4.2　HPACK 动态表 .....................................................................................269
8.4.3　HPACK 首部类型 .................................................................................269
8.4.4　Huffman 编码表 ...................................................................................275
8.4.5　Huffman 编码脚本 ...............................................................................276
8.4.6　为什么 Huffman 编码不总是最佳的 ..................................................278
8.5　HPACK压缩实例 ..............................................................................................279
8.6　客户端和服务端对HPACK的实现 ..................................................................285
8.7　HPACK的价值 ..................................................................................................287
总结 ............................................................................................................................287
第4部分　HTTP的未来
第9章　TCP、QUIC和HTTP/3....................................................................................291
9.1　TCP的低效率因素，以及HTTP ......................................................................292
9.1.1　创建 HTTP 连接的延迟 .......................................................................293
9.1.2　TCP 拥塞控制对性能的影响...............................................................295
9.1.3　TCP 低效率因素对 HTTP/2 的影响 ...................................................303
9.1.4　优化 TCP ...............................................................................................307
9.1.5　TCP 和 HTTP 的未来...........................................................................313
9.2　QUIC .................................................................................................................313
9.2.1　QUIC 的性能优势 ................................................................................315
9.2.2　QUIC 和网络技术栈 ...........................................................................316
9.2.3　什么是 UDP，为什么 QUIC 基于它 ..................................................317
9.2.4　标准化 QUIC ........................................................................................320
9.2.5　HTTP/2 和 QUIC 的不同 .....................................................................322
9.2.6　QUIC 的工具 ........................................................................................325
9.2.7　QUIC 实现 ............................................................................................327
9.2.8　你应该使用 QUIC 吗 ...........................................................................327
总结 ............................................................................................................................328
第10章　HTTP将何去何从..........................................................................................329
10.1　关于HTTP/2的争议，以及它没有解决的问题 ............................................330
10.1.1　反对 SPDY 的观点 .............................................................................330
10.1.2　隐私问题和 HTTP 中的状态 .............................................................332
10.1.3　HTTP 和加密 ......................................................................................337
10.1.4　传输协议的问题 .................................................................................340
10.1.5　HTTP/2 太过于复杂 ...........................................................................344
10.1.6　HTTP/2 是一种权宜之计 ...................................................................345
10.2　HTTP/2的实际应用 ........................................................................................345
10.3　HTTP/2的未来版本，HTTP/3或者HTTP/4会带来什么 ..............................347
10.3.1　QUIC 是 HTTP/3 吗 ...........................................................................347
10.3.2　更进一步改进 HTTP 二进制协议 ....................................................348
10.3.3　在传输层之上进一步优化 HTTP ......................................................348
10.3.4　什么时候会需要新的 HTTP 版本 .....................................................351
10.3.5　如何引入未来版本的 HTTP ..............................................................352
10.4　将HTTP当作一个更通用的传输协议 ...........................................................352
10.4.1　使用 HTTP 语义和消息来传递非 Web 流量 ....................................353
10.4.2　使用 HTTP/2 二进制成帧层 ..............................................................354
10.4.3　使用 HTTP 启动另一个协议 .............................................................355
总结 ............................................................................................................................359
附录A　将常见Web服务器升级到HTTP/2...................................................................360