HTTP/2, HTTP/3 and QUIC Kristian A. Hiorth University of Oslo, Norway September 7, 2020
IN5150: HTTP/2, HTTP/3 and QUIC Kristian A. Hiorth Dept. of Informatics University of Oslo [Photo: Jason Coates]
Overview: first, a look back at legacy HTTP, followed by what HTTP/2 does differently, and finally the future of HTTP with QUIC Legacy HTTP HTTP/2 QUIC and HTTP/3 1
Legacy HTTP HTTP/2 QUIC and HTTP/3
The Web, and HTTP with it, is pretty old 1989/1990 World wide web invented at CERN 2 [Photo: Geni @ Wikimedia Commons]
The Web, and HTTP with it, is pretty old 1989/1990 World wide web invented at CERN May 1996 HTTP/1.0 formalised in RFC 1945 one request ⇔ one (TCP) connection 2 [Photo: Geni @ Wikimedia Commons]
The Web, and HTTP with it, is pretty old 1989/1990 World wide web invented at CERN May 1996 HTTP/1.0 formalised in RFC 1945 one request ⇔ one (TCP) connection January 1997 HTTP/1.1 in RFC 2068 persistent connections by default request pipelining max. 2 connections per server 2 [Photo: Geni @ Wikimedia Commons]
Then came two decades of HTTP/1.1 patches June 1999 HTTP/1.1 updated, given proposed standard status in RFC 2616 3
Then came two decades of HTTP/1.1 patches June 1999 HTTP/1.1 updated, given proposed standard status in RFC 2616 ... Countless RFCs (or not) specifying extensions 3
Then came two decades of HTTP/1.1 patches June 1999 HTTP/1.1 updated, given proposed standard status in RFC 2616 ... Countless RFCs (or not) specifying extensions June 2014 HTTP/1.1 reformalised as RFCs 7230 – 7235 concurrent connection limit relaxed 3
HTTP/1.1 pipelined requests remain serial 4
Web developers came up with creative workarounds to decrease page load times Spriting with CSS: #home a:hover { background: url('img_navsprites_hover.gif') 0 -45px; } #prev a:hover { background: url('img_navsprites_hover.gif') -47px -45px; } #next a:hover { background: url('img_navsprites_hover.gif') -91px -45px; } [Photo: W3schools] 5
Web developers came up with creative workarounds to decrease page load times Inlining Place content directly in HTML; data: URLs. {background-image:url("data:image/png;base64,iVBOAA...")} 6
Web developers came up with creative workarounds to decrease page load times Inlining Place content directly in HTML; data: URLs. {background-image:url("data:image/png;base64,iVBOAA...")} Sharding Spread contents among many domain names to circumvent connection limits. 6
Legacy HTTP HTTP/2 QUIC and HTTP/3
HTTP/2 was the first major revision to HTTP since 1999 ◮ Originated as Google’s SPDY experimental protocol 7
HTTP/2 was the first major revision to HTTP since 1999 ◮ Originated as Google’s SPDY experimental protocol ◮ RFCs 7540 and 7541 published in May 2015 7
HTTP/2 was the first major revision to HTTP since 1999 ◮ Originated as Google’s SPDY experimental protocol ◮ RFCs 7540 and 7541 published in May 2015 ◮ HTTP semantics stay the same 7
HTTP/2 was the first major revision to HTTP since 1999 ◮ Originated as Google’s SPDY experimental protocol ◮ RFCs 7540 and 7541 published in May 2015 ◮ HTTP semantics stay the same ◮ Framing and on-the-wire behaviour see major changes 7
To understand the impetus for HTTP/2, we need to look at Head of Line blocking 8
To understand the impetus for HTTP/2, we need to look at Head of Line blocking [Photos: Vibeke Friis, A. Wee] 8
The main innovation in HTTP/2 is a better defined and more flexible framing concept HTTP/1.1 No proper framing concept. Response runs on and on until it is done. 9
The main innovation in HTTP/2 is a better defined and more flexible framing concept HTTP/1.1 No proper framing concept. Response runs on and on until it is done. HTTP/2 Clearly defined frames, of several distinct types. Binary format. 9
Framing enables multiplexing several logical streams onto a single HTTP/2 connection +-----------------------------------------------+ | Length (24) | +---------------+---------------+---------------+ | Type (8) | Flags (8) | +-+-------------+---------------+-------------------------------+ |R| Stream Identifier (31) | +=+=============================================================+ | Frame Payload (0...) ... +---------------------------------------------------------------+ 10
HTTP/2 also contains other features intended to improve performance ◮ Stream priorities and dependencies 11
HTTP/2 also contains other features intended to improve performance ◮ Stream priorities and dependencies ◮ Header compression using HPACK 11
HTTP/2 also contains other features intended to improve performance ◮ Stream priorities and dependencies ◮ Header compression using HPACK ◮ Streams are resettable 11
HTTP/2 also contains other features intended to improve performance ◮ Stream priorities and dependencies ◮ Header compression using HPACK ◮ Streams are resettable ◮ Server push 11
The HTTP/2 spec does not mandate TLS encryption, but in practice it is mandatory Discovery of HTTP/2 capability at the server side during TLS handshake using Application Layer Protocol Negotiation (ALPN). 12
Legacy HTTP HTTP/2 QUIC and HTTP/3
HTTP/3 is simply the mapping of HTTP/2 onto a QUIC transport QUIC has transport-level features that obviate the need for some of HTTP/2’s application layer features. 13
To properly eliminate HOL blocking, HTTP/2 is not enough, because TCP itself suffers from HOL blocking No “clean” way of eliminating TCP-level HOL blocking. 14
To properly eliminate HOL blocking, HTTP/2 is not enough, because TCP itself suffers from HOL blocking No “clean” way of eliminating TCP-level HOL blocking. 14
QUIC brings in the features everyone in the Web space wanted for improving latency, just done better ◮ Multistreaming without HOL blocking. 15
QUIC brings in the features everyone in the Web space wanted for improving latency, just done better ◮ Multistreaming without HOL blocking. ◮ In-order, reliable delivery per stream . 15
QUIC brings in the features everyone in the Web space wanted for improving latency, just done better ◮ Multistreaming without HOL blocking. ◮ In-order, reliable delivery per stream . ◮ Shorter handshakes, immediate data (“0-RTT”) without hacks. 15
QUIC brings in the features everyone in the Web space wanted for improving latency, just done better ◮ Multistreaming without HOL blocking. ◮ In-order, reliable delivery per stream . ◮ Shorter handshakes, immediate data (“0-RTT”) without hacks. ◮ TLS encryption always mandatory. 15
QUIC brings in the features everyone in the Web space wanted for improving latency, just done better ◮ Multistreaming without HOL blocking. ◮ In-order, reliable delivery per stream . ◮ Shorter handshakes, immediate data (“0-RTT”) without hacks. ◮ TLS encryption always mandatory. ◮ In-band connection identifier, separate from IP pseudoheader → connection migration 15
QUIC brings in the features everyone in the Web space wanted for improving latency, just done better ◮ Multistreaming without HOL blocking. ◮ In-order, reliable delivery per stream . ◮ Shorter handshakes, immediate data (“0-RTT”) without hacks. ◮ TLS encryption always mandatory. ◮ In-band connection identifier, separate from IP pseudoheader → connection migration ◮ Userspace implementation atop UDP, easier to develop, iterate. 15
QUIC encrypts everything to make interference harder Interference from middleboxes can cause headaches with TCP, HTTP/1.1. 16
QUIC encrypts everything to make interference harder Interference from middleboxes can cause headaches with TCP, HTTP/1.1. QUIC solution: hide (almost) everything! 16
QUIC encrypts everything to make interference harder Interference from middleboxes can cause headaches with TCP, HTTP/1.1. QUIC solution: hide (almost) everything! Exception: 1 single “spin bit” to allow RTT derivation. 16
QUIC streams do not suffer from HOL blocking and can be prioritized UDP datagrams carrying QUIC frames are delivered immediately, even out of order → No HOL blocking at transport layer. 17
QUIC streams do not suffer from HOL blocking and can be prioritized UDP datagrams carrying QUIC frames are delivered immediately, even out of order → No HOL blocking at transport layer. Stream prioritization as part of QUIC (still a bit fuzzy in the specs). 17
QUIC connections are congestion controlled Still based on TCP congestion control. 18
QUIC tries to be future-proof and easier to change Version negotiation when setting up connection. 19
HTTP/3 adapts the HTTP/2 framing and protocol to take advantage of QUIC Multistreaming drop HTTP-level multistreaming, use QUIC streams instead. 20
HTTP/3 adapts the HTTP/2 framing and protocol to take advantage of QUIC Multistreaming drop HTTP-level multistreaming, use QUIC streams instead. Special control streams Separate request/response streams from header streams 20
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