HTTP 2.0 and QUIC


Protocols Of The (near) Future


Iliyan Peychev

2014

HTTP 1.1 has ISSUES



It is very latency sensitive.

The specification is huge.

Contains a lot of optional parts, for example  HTTP Pipelining.

HTTP 1.1

Latency kills and bandwidth is not everything:


HTTP 1.1 Pipelining


HTTP 1.1 PIPELINING


The server must send its responses in the same order that the requests were received.

So the entire connection remains first-in-first-out (FIFO)  and Head-of-line (HOL) blocking can occur.

DEVeloper workarounds

Bunch of hacks were invented:
  1. Image sprites.
  2. Sharding.
  3. Including resources directly in the page (inlining).
  4. Concatenating files.
  5. Combo services.
  6. Preloading resources.
  7. Reducing cookies size.
  8. Using cookie-free domains for components
  9. Using <link> instead @import
  10. Pack Components into a multipart document
 
(like email with attachments)

HTTP 1.1



HTTP 2.0 objectives


All existing should still work (aka. "We can't break the web!").

but 

Fix the root of the issues in HTTP 1.1

HTTP 2.0 protocol UPgrade


Upgrade in HTTP 1.1 is a header, which allows the server to send back a response using the new protocol when getting such a request over the old protocol.
However, this means a round-trip.

Solution?

A TLS extension for application layer protocol negotiation within the TLS handshake.

HTTP 2.0 FEATURES


It is binary protocol and it sends frames.

Each frame belongs to a stream.

Streams are multiplexed and they have priorities.

Server push.

One single connection to the server should be enough.

FRAME types

STREAMS



Streams are logical association.

They are bi-directional sequence of frames exchanged between the server and client.

One single connection may contain multiple open streams.

Connection



PRIORITIES and dependencies


Each stream has a priority.

The client specifies the importance of the stream.

It also has dependency.

A stream can be made dependent on another one.

Priorities might be changed runtime.
Example: the browser may request different resources on scrolling page down.

Header compression


HTTP 2.0 is stateless protocol too.

The client still has to send data to the server.

However, the headers in HTTP 2.0 are now compressed.

Header compression is stateful, using a single compression context for the entire connection.

The algorithm is called HPACK (Header Compression for HTTP/2)
(Note: The algorithm has been changed because of attacks like CRIME and BREACH)

DATA compression


Data frames are optionally compressed using GZip compression and each frame is individually compressed.

The state of the compressor is reset for each frame.

SERVER PUSH


"You ask for coffee, but I know you will then ask for a cigar, so get both now and don't bother me anymore."

This matches what we do now with inlining resources.

The client explicitly must allow it.

The client can terminate a stream via RST_STREM frame.

 

quic

Natural extension of SPDY/HTTP 2.0 research.

Multiplexing transport protocol.

Runs on top of UDP.

Goal: 0-RTT (round-trip time) connectivity overhead.

Has all the benefits of SPDY/HTTP 2.0, but...

No HOL Blocking!


No head-of-line blocking in QUIC:



Image source: QUIC @ Google Developers Live, February 2014

LATENCY Kills

 

Delay

User reaction

< 100 ms

instant

100 ms - 300 ms

reasonable

300 ms - 1 s

getting tedious

> 1 s

closes tab

TCP + TLS


TCP + TLS


Repeat connection - 200 ms 

New connection - 300 ms

QUIC


Repeat connection - 0 ms 

New connection - 100 ms

encryption


Comparable to TLS, with more efficient handshake.


Replay attack and IP Spoofing protection.

FOrward Error correction



you leave home - connection continues


Communication channels are not defined by IP+Port but by an ID.

You leave a WiFi zone and entering a mobile one but the connection continues.

wrap up


QUIZ


How will all that affect the way we develop and optimize applications now?

Remember the build process and the optimizations you probably do?

The hacks we do now

  1. Image sprites.
  2. Sharding.
  3. Including resources directly in the page (inlining).
  4. Concatenating files.
  5. Combo services.
  6. Preloading resources.
  7. Reducing cookies size.
  8. Using cookie-free domains for components
  9. Using <link> instead @import
  10. Pack Components into a multipart document
  
(like email with attachments)
How many of those will disappear?

HTTP 2.0 AND QUIC?



Thanks!




Questions?



Twitter: ipeychev
GitHub: ipeychev

2014

HTTP 2.0 and QUIC: Protocols Of The (near) Future -- and why they're important

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