HTTP/3 explained
  • README
  • English
    • Why QUIC
      • Remember HTTP/2
      • TCP head of line blocking
      • TCP or UDP
      • Ossification
      • Secure
      • Reduced latency
    • Process
      • IETF
      • Experience from HTTP/2
      • Status
    • Protocol features
      • UDP
      • Reliable
      • Streams
      • In Order
      • Fast handshakes
      • TLS 1.3
      • Transport and application
      • HTTP/3 over QUIC
      • Non-HTTP over QUIC
    • How QUIC works
      • Connections
      • Connections use TLS
      • Streams
      • 0-RTT
      • Spin Bit
      • User space
      • API
    • HTTP/3
      • HTTPS:// URLs
      • Bootstrap with Alt-svc
      • QUIC streams and HTTP/3
      • Prioritization
      • Server push
      • Comparison with HTTP/2
    • Common criticism
    • The specifications
    • QUIC future
  • Español
    • Por qué QUIC
      • ¿Te acuerdas de HTTP/2?
      • Bloqueo de cabeza de línea TCP
      • TCP o UDP
      • Osificación
      • Seguro
      • Datos tempranos
    • Proceso
      • IETF
      • La experiencia de HTTP/2
      • Estado
    • Características del protocolo
      • UDP
      • Transferencias de datos fiables
      • Flujos múltiples
      • Entrega en orden
      • Rápido establecimiento de comunicación
      • TLS 1.3
      • Nivel de transporte y aplicación
      • HTTP/3 sobre QUIC
      • No-HTTP sobre QUIC
    • Cómo funciona QUIC
      • Conexiones
      • TLS
      • Flujos
      • 0-RTT
      • Spin Bit
      • Espacio de usuario
      • API
    • HTTP/3
      • HTTPS:// URLs
      • Alt-svc
      • Flujos de QUIC y HTTP/3
      • Priorización
      • Push del servidor
      • Comparación con HTTP/2
    • Críticas habituales
    • Especificaciones
    • QUIC v2
  • Deutsch
    • Warum QUIC
      • Erinnerst du dich an HTTP/2?
      • TCP Head-of-line blocking
      • TCP oder UDP
      • Ossifikation
      • Sicherheit
      • Reduzierte Latenz
    • Prozess
      • IETF
      • Erfahrungen von HTTP/2
      • Status
    • Eigenschaften des Protokolls
      • UDP
      • Zuverlässige Datenübertragung
      • Streams
      • In-Order Ausliefung
      • Schnelle Handshakes
      • TLS 1.3
      • Transport und Anwendung
      • HTTP/3 über QUIC
      • Nicht-HTTP über QUIC
    • Wie QUIC funktioniert
      • Verbindungen
      • Verbindungen verwenden TLS
      • Streams
      • 0-RTT
      • Spin Bit
      • User-space
      • API
  • فارسی
    • چرا QUIC
      • آیا HTTP/2 را به یاد دارید؟
      • مسدود کننده سرِ صف TCP
      • TCP یا UDP
      • استخوان‌سازی (fa/Ossification)
      • امن
      • تأخیرِ کاهش یافته
    • پردازش
      • کارگروه مهندسی اینترنت (fa/IETF)
      • تجربه از HTTP/2
      • وضعیت
    • ویژگی‌های پروتکل
      • UDP
      • مطمئن
      • جریان‌ها
      • منظم
      • دست‌دهی‌های سریع
      • TLS 1.3
      • انتقال و کاربرد
      • پروتکل HTTP/3 بر روی QUIC
      • غیر HTTP بر روی QUIC
    • پروتکل QUIC چطور کار می‌کند
      • اتصال‌ها
      • اتصال‌ها از TLS استفاده می‌کنند
      • جریان‌ها
      • زمان تأخیر چرخشی صفر (fa/0-RTT)
      • بیت چرخشی
      • فضای کاربر
      • رابط برنامه‌نویسی کاربردی (fa/API)
    • پروتکل انتقال ابرمتن نگارش ۳ (fa/HTTP/3)
      • نشانی وب‌های HTTPS://
      • بوت اِسترپ با سرایندِ Alt-svc
      • جریان‌های QUIC و HTTP/3
      • اولویت بندی
      • فشارِ سرور
      • مقایسه با HTTP/2
    • نقدگریِ مرسوم
    • مشخصات
    • پروتکل QUIC نسخه ۲
  • Français
    • Pourquoi QUIC
      • Souvenez-vous de HTTP/2 ?
      • Blocage de tête de ligne TCP
      • TCP ou UDP
      • Ossification
      • Sécurisé
      • Latence réduite
    • La procédure
      • IETF
      • Expérience depuis HTTP/2
      • Statut
    • Caractéristiques du protocole
      • UDP
      • Fiable
      • Flux
      • Dans l'ordre
      • Handshakes rapides
      • TLS 1.3
      • Transport et application
      • HTTP/3 sur QUIC
      • Non-HTTP sur QUIC
    • Comment QUIC fonctionne
      • Connexions
      • Les connexions utilisent TLS
      • Flux
      • 0-RTT
      • Spin Bit
      • Espace utilisateur
      • API
    • HTTP/3
      • URLs HTTPS://
      • Amorçage avec Alt-svc
      • Flux QUIC et HTTP/3
      • Priorisation
      • Push serveur
      • Comparaison avec HTTP/2
    • Critique générale
    • Les spécifications
    • QUIC v2
  • Italiano
    • Perché QUIC
      • Ricordi HTTP/2 ?
      • Blocco ad inizio linea, "TCP head of line blocking"
      • TCP o UDP
      • Ossificazione
      • Sicuro
      • Latenza ridotta
    • Evoluzione
      • IETF
      • Esperienza da HTTP/2
      • Status
    • Caratteristiche del protocollo
      • UDP
      • Affidabile
      • Streams
      • Ordinato
      • Negoziazioni veloci
      • TLS 1.3
      • Trasporto e applicazione
      • HTTP over QUIC
      • Non-HTTP over QUIC
    • Come funziona QUIC
      • Connessioni
      • Connessioni su TLS
      • Streams
      • 0-RTT
      • Bit Rotante
      • User space
      • API
    • HTTP/3
      • URLs in HTTPS://
      • Bootstrap via Alt-svc
      • Gli streams QUIC e HTTP/3
      • Prioritizzazione
      • Server push
      • Paragone con HTTP/2
    • Critiche comuni
    • Le specifiche
    • QUIC v2
  • 日本語
    • なぜ QUIC なのか
      • HTTP/2、覚えていますか?
      • TCP head-of-line ブロッキング
      • TCP か UDP か
      • 硬直化
      • セキュア
      • レイテンシの軽減
    • これまでの歩み
      • IETF
      • HTTP/2 からの経験
      • 現在の状況
    • プロトコルの機能
      • UDP 上の転送プロトコル
      • 高信頼性のデータ転送
      • コネクションは複数のストリームを扱う
      • 到着順序の保証
      • 素早いハンドシェイク
      • TLS 1.3
      • トランスポートとアプリケーションレベル
      • HTTP/3 over QUIC
      • Non-HTTP over QUIC
    • QUIC の仕組み
      • コネクション
      • 接続で TLS を使う
      • ストリーム
      • 0-RTT
      • Spin Bit
      • ユーザー空間
      • API
    • HTTP/3
      • HTTPS:// の URL
      • Alt-svc を使ったブートストラップ
      • QUIC ストリームと HTTP/3
      • プライオリティ制御
      • Server push
      • HTTP/2 と比較した HTTP/3
    • よくある疑問点
    • The specifications (ja/仕様)
    • QUIC v2
  • 한국어
    • 왜 QUIC인가
      • HTTP/2를 기억하는가?
      • TCP HOL(ko/head of line) 블로킹
      • TCP or UDP
      • 고착화(ko/Ossification)
      • 안전
      • 감소된 지연시간
    • 과정
      • IETF
      • HTTP/2에서의 경험
      • 상태
    • 프로토콜 기능
      • UDP
      • 신뢰성
      • 스트림
      • 순서에 맞는 전송
      • 빠른 핸드쉐이크
      • TLS 1.3
      • 전송 계층과 애플리케이션 계층
      • QUIC을 통한 HTTP/3
      • QUIC을 통한 HTTP가 아닌 프로토콜
    • QUIC의 동작 방식
      • 연결
      • TLS을 사용하는 연결
      • 스트림
      • 0-RTT
      • 스핀 비트
      • 사용자 영역
      • API
    • HTTP/3
      • HTTPS:// URL
      • Alt-svc로 부트스트랩하기
      • QUIC 스트림과 HTTP/3
      • 우선순위 정하기
      • 서버 푸시
      • HTTP/3과 HTTP/2의 비교
    • 일반적인 비판
    • 명세
    • QUIC v2
  • Română
    • De ce QUIC
      • Vă mai aduceți aminte de HTTP/2?
      • Blocarea vârfului stivei în TCP
      • TCP sau UDP
      • Osificarea
      • Securitate
      • Timp de așteptare redus
    • Procesul
      • IETF
      • Experiența acumulată cu HTTP/2
      • Starea curentă
    • Funcționalitățile protocolului
      • UDP
      • Fiabilitate
      • Fluxuri
      • În aceeași ordine
      • Handshakes rapide
      • TLS 1.3
      • Nivelurile de aplicație și de transfer
      • HTTP/3 peste QUIC
      • Non-HTTP peste QUIC
    • Cum funcționează QUIC
      • Conexiuni
      • Conexiunile folosesc TLS
      • Fluxuri
      • 0-RTT
      • Spin Bit
      • User space
      • API
    • HTTP/3
      • Adresele HTTPS://
      • Bootstrap cu Alt-svc
      • Fluxurile QUIC și HTTP/3
      • Prioritizare
      • Server push
      • Comparația cu HTTP/2
    • Critici comune
    • Specificația
    • QUIC v2
  • 简体中文
    • 导言
    • 为什么需要QUIC
      • 回顾HTTP/2
      • TCP队头阻塞
      • 用TCP还是UDP
      • 协议僵化
      • 安全性
      • 减少延迟
    • 协议进展
      • IETF
      • HTTP/2的经验
      • 标准化进展情况
    • 协议特点
      • 基于UDP
      • 可靠性
      • 数据流
      • 有序交付
      • 快速握手
      • TLS 1.3
      • 传输层与应用层协议
      • QUIC之上的HTTP协议
      • QUIC之上的非HTTP协议
    • QUIC工作原理
      • 连接
      • 使用TLS的连接
      • 数据流
      • 0-RTT
      • 旋转比特位
      • 用户空间实现
      • API
    • HTTP/3
      • HTTPS:// URL
      • 使用Alt-svc自举
      • QUIC流与HTTP/3
      • 优先度
      • 服务器推送
      • 与HTTP/2的比较
    • 常见批评
    • 技术标准
    • QUIC v2
  • 繁體中文
    • 導言
    • 為什麼是QUIC
      • 回顧HTTP/2
      • TCP隊頭阻塞
      • TCP還是UDP
      • 協定僵化
      • 安全性
      • 減少延遲
    • 協定的進展
      • IETF
      • 從HTTP/2得到的經驗
      • 目前的狀況
    • 協定的功能
      • 基於UDP的傳輸層協定
      • 高度可靠的傳輸
      • 串流
      • 有序交付
      • 快速交握
      • TLS 1.3
      • 傳輸層與應用層協定
      • HTTP/3 over QUIC
      • Non-HTTP over QUIC
    • QUIC運作原理
      • 連接
      • 使用TLS的連接
      • QUIC串流
      • 0-RTT
      • Spin Bit
      • 用户空間
      • API
    • HTTP/3
      • HTTPS:// URL
      • 使用Alt-svc進行引導
      • QUIC串流與HTTP/3
      • 優先次序
      • 伺服器推送
      • 與HTTP/2的比較
    • 常見的錯誤批評
    • 技術標準
    • QUIC v2
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On this page
  • UDP will never work
  • UDP is slow in kernels
  • QUIC takes too much CPU
  • This is just Google
  • This is too small of an improvement

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  1. English

Common criticism

PreviousComparison with HTTP/2NextThe specifications

Last updated 4 years ago

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UDP will never work

A lot of enterprises, operators and organizations block or rate-limit UDP traffic outside of port 53 (used for DNS) since it has in recent days mostly been abused for attacks. In particular, some of the existing UDP protocols and popular server implementations for them have been vulnerable for amplification attacks where one attacker can make a huge amount of outgoing traffic to target innocent victims.

QUIC has built-in mitigation against amplification attacks by requiring that the initial packet must be at least 1200 bytes and by restriction in the protocol that says that a server must not send more than three times the size of the request in response without receiving a packet from the client in response.

UDP is slow in kernels

This seems to be the truth, at least initially. We can of course not tell how this will develop and how much of this is simply the result of UDP transfer performance not having been in developers' focus for many years.

For most clients, this "slowness" is probably never even noticeable.

QUIC takes too much CPU

Similar to the "UDP is slow" remark above, this is partly because the TCP and TLS usage of the world has had a longer time to mature, improve and get hardware assistance.

There are reasons to expect this to improve over time, and already . The question is how much this extra CPU usage will hurt deployers.

This is just Google

No it is not. Google brought the initial spec to the IETF after having proved, on a large Internet-wide scale, that deploying this style of protocol over UDP actually works and performs well.

Since then, individuals from a large number of companies and organizations have worked in the vendor-neutral organization IETF to put together a standard transport protocol out of it. In that work, Google employees have of course been participating, but so have employees from a large number of other companies that are interested in furthering the state of transport protocols on the Internet, including Mozilla, Fastly, Cloudflare, Akamai, Microsoft, Facebook and Apple.

This is too small of an improvement

That is not really a critique but an opinion. Maybe it is, and maybe it is too little of an improvement so close in time since HTTP/2 was shipped.

HTTP/3 is likely to perform much better in packet loss-ridden networks, it offers faster handshakes so it will improve latency both as perceived and actual. But is that enough of benefits to motivate people to deploy HTTP/3 support on their servers and for their services? Time and future performance measurements will surely tell!

we are seeing some improvements in this space