QUIC进入IETF最后征求意见，互联网的又一次巨大飞跃

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"在 2020 年 10 月 22 日，Cloudflare 发布一篇官方博文《 "},{"type":"link","attrs":{"href":"https:\/\/blog.cloudflare.com\/last-call-for-quic\/","title":null,"type":null},"content":[{"type":"text","text":"A Last Call for QUIC, a giant leap for the Internet"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 》。这篇文章宣告了在 IETF（互联网工程任务组）发展近 4 年后，描述 QUIC 和 HTTP\/3 的文件系统的草案 32 被纳入 IETF 最后征求意见。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"IETF QUIC 工作组联合主席 Lucas Pardue 表示，“对于工作组来说，这是一个重要的里程碑。现在，我们将告诉整个 IETF 社区，我们已经几乎完成了工作，欢迎他们的最终审核。”"}]},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/3f\/3f8379fecc129d9b0a8faf922118c32f.png","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"腾讯 TEG 云架构平台部专家工程师，腾讯云CLB研发负责人罗成对 InfoQ 记者说：“last call 意味着 QUIC 在社区范围内的公开讨论即将结束。在接下来的几周时间有可能发布正式的 RFC。QUIC RFC 如果定稿，对于后续 QUIC 协议的工程化和开源社区的支持也将有极大的推动作用，QUIC 的使用将会越来越普及。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"如果你访问一个启用了 HTTP\/3 的网站，比如 "},{"type":"link","attrs":{"href":"https:\/\/cloudflare-quic.com","title":null,"type":null},"content":[{"type":"text","text":"https:\/\/cloudflare-quic.com"}],"marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}]},{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" 。你会看到响应头包含 Alt-Svc: h3-29=\"…。一旦最后征求意见完成且RFC发布，你就会看到网站简单返回Alt-Svc: h3=\"…。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"QUIC 源起"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"Quic，全称为 quick udp internet connection，即快速 UDP 网络连接。最初，它是一种由谷歌开发的网络传输协议，2013 年实现。据悉，QUIC 使用 UDP 协议，在两个端点间创建连线，且支持多路复用连线。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"据罗成介绍，一直以来，谷歌对用户的 web 访问速度非常重视，投入很大：2012 年，谷歌开始实验性研究 QUIC 协议，目的是提升用户使用谷歌搜索的访问速度。当时，一起研发的还有一个协议——SPDY，即HTTP2的前身。但是，SPDY是基于TCP实现的，存在一些无法克服的缺陷。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"“所以，谷歌希望另起炉灶，完全抛开 TCP，使用 UDP 来实现一套可靠的快速的传输协议。”他说。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"2013 年，QUIC 协议开始在数百万 Chrome 用户上进行实验；2015 年，QUIC 的收益和演进路线已经非常明确。2015 年 6 月，QUIC 的网络草案被正式提交至互联网工程任务组（IETF）。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"IETF 则在 2016 年正式成立 QUIC 工作组，对 QUIC 协议草案进行讨论和改进。最终，2018 年 10 月，互联网工程任务组 HTTP 及 QUIC 工作小组正式将基于 QUIC 协议的 HTTP（HTTP over QUIC）重命名为 HTTP\/3，成为互联网下一代标准传输协议，引起业界极大的兴趣。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"罗成表示，“在国内，腾讯也很早就开始了对 QUIC 的研发，2015 年，开始研发 QUIC 协议；2016 年，在内部大规模使用；2017 年，我们在腾讯云的 CLB 负载均衡器和 CDN 产品上发布了对 QUIC 的支持。也是继谷歌之后，第二家这么早大规模使用 QUIC 协议的互联网厂商。“"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"QUIC 协议和 HTTP\/3 的影响"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"在罗成看来，QUIC 的普及会对互联网带来三方面的影响："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"第一，提升整个互联网的访问速度。因为协议本身支持 ORTT 建立连接、多路传输等特性。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"第二，提升互联网的传输安全。因为 QUIC 传输的内容默认都是加密的，这对人们的隐私保护非常重要。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"第三，由于 QUIC 基于应用层实现，减少了对操作系统内核和中间设备的依赖。QUIC 也能推动互联网流量工程和拥塞控制算法的快速演进，进一步促进访问速度、QOS、流量成本等方面的优化。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"据了解，只要在访问速度、访问安全以及网络健壮性有要求的领域，QUIC 都能带来明显的作用，比如云游戏、音视频、页面浏览、搜索引擎、广告加载等。"}]},{"type":"image","attrs":{"src":"https:\/\/static001.geekbang.org\/infoq\/71\/7197767485c632023886c438b4f16f11.jpeg","alt":null,"title":null,"style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"具体说来，服务端和 App 在支持 QUIC 协议后，用户访问同样的业务会更快、更安全、更顺畅。比如，在无需任何修改的情况下，App 的访问速度提升 15%以上；WiFi 切换到 4G 或 5G 时，你不会感觉到卡顿。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"根据罗成的解释，QUIC 之所以能更快，原因有三："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"QUIC 协议支持 ORTT 握手建连。QUIC 基于 UDP 传输，不像 TCP 需要三次握手来建立连接。而在安全传输层面，它以前使用 QUIC crypto 协议，现在支持 TLS 1.3 协议，都能实现更高比例的 ORTT 安全建连。相比 HTTP\/2 协议，建立连接的 RTT(round trip time)从 2-3 个直接减少到 0-1 个，这意味着 QUIC 发送第一个数据包时有了几百毫秒的优势。此外，QUIC 的 ORTT 还能实现更多的定制。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"QUIC 改进的拥塞控制算法。一方面，协议层做了更明确的限制也能携带更多的信息，比如严格递增的序列号、更准确的 ack delay、更大范围的 sack 范围等。另一方面，由于 QUIC 基于应用层实现，可以有更大的扩展性。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"QUIC 支持多路复用且减少了队头阻塞。HTTP\/2 虽然也支持多路复用，但是由于 TCP 协议的 head of line block（队头阻塞），导致多路复用的效果也打了折扣。但是，QUIC 可以避免这样的拥塞，因为它基于应用层实现，协议栈能允许部分已经完成的 stream 进行交互，不会因为丢了几个包就导致后面的 stream 也被阻塞。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"在安全性上，由于 QUIC 协议默认使用了安全传输协议，实现了证书认证、秘钥协商、内容加密、一致性校验等安全功能。这对人们的隐私保护也会很彻底，而被中间者劫持的可能性也非常低。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"在连接迁移方面，罗成举了一个例子。用户经常在移动网络下切换，家里用 WiFi 看直播，一出门，WiFi 就断了，只能连上 4G。由于网络断了，直播一定会中断几秒钟。如果使用 QUIC 的连接迁移后，用户从 WiFi 切换到 4G，他不会感到卡顿。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"“其主要原理就是 QUIC 的连接迁移功能。连接没有中断，用户的数据传输也没有中断。但是，连接中断的概念虽然容易理解，在服务端支持上却比较困难，比如腾讯云CLB就需要 4 层负载均衡、7 层负载均衡以及进程间联动，还包括进程重启以及平滑退出时的设计。”他说。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"企业面临的挑战"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"无论是安全性，还是用户体验，QUIC 协议和 HTTP\/3 对企业都是更好的选择。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"但是，罗成对 InfoQ 记者表示，“大规模使用 QUIC 的话，会有很多挑战。”"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"挑战一，如何实现 QUIC 协议的支持。由于 QUIC 协议非常复杂，且 RFC 尚未定稿，导致目前缺乏一个成熟通用的服务框架支持。并且，一些开源的框架也很不完善，比如 Nginx、MSQUIC 等。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"挑战二，QUIC 非常消耗 CPU 资源，这会极大增加服务器成本。不管是默认加解密，还是 UDP 协议栈以及 QUIC 协议栈，相比传统的基于 TCP 的协议，比如 HTTPS，要增加一倍以上的机器成本。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"挑战三，QUIC 的运营工具非常欠缺，问题排查非常困难。QUIC 协议比较新，而类似 TCP 的 tcpdump、wireshark 等工具都不完善。另外，由于 QUIC 协议的序列号都进行了加密，协议栈也是重新在用户态实现的，所以以前 UDP\/TCP 的一些抓包和分析工具都失效了，需要重新开发。比如，用户丢的包，以前用 tcpdump，外加 wireshark 就能分析在哪丢的包、为什么丢包，但是这无法适用于 QUIC，因为不仅传输层帧格式变了，而且帧的头部是加密的，传统工具都无法解析。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"写在最后："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":" "}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"color","attrs":{"color":"#494949","name":"user"}}],"text":"QUIC协议不仅给互联网用户带来全新的体验，更快的访问，而且更加安全。对于它的意义，正如IETF QUIC 工作组联合主席 Lucas Pardue所说，“新协议是互联网的一个巨大飞跃，因为它带来了新的机遇和创新。”"}]}]}