Gotcha! I finally understand HTTP/2

Daniela Matos de Carvalho

SEIUM 2017 @Braga

sericaia

who-am-i

What are we facing globally?

Why http 1.1 is not enough?

Different access

(https://www.webworldwide.io/ for details) 

Different access

Different bandwidth

Different latency

Latency and Bandwidth

(image source: High Performance Browser Networking - Ilya Gregorik)

Latency and Bandwidth

(image source: High Performance Browser Networking - Ilya Gregorik)

Goal

 low latency

high throughput

HTTP/2 for the rescue!

HTTP

The Hypertext Transfer Protocol

HTTP

1991

1st proposal by Tim Berners-Lee

request and response between client and server

1 TCP connection per request

standard

HTTP

0.9         1.0         1.1         2

What happens when a request is made?

DOM, CSSOM and JS

render tree

"styles at the top,

scripts at the bottom"

How much time does it take to send a request from New York to London?

...but let's focus on the browser!

Browser Optimizations

DNS pre-resolve

<link rel="dns-prefetch" href="//google.com" />

TCP pre-connect

<link
    href='https://fonts.google.com'
    rel='preconnect'
    crossorigin
/>

Resource prefetching

<link rel="prefetch" href="image.png" />

Page pre-rendering *hint*

<link rel="prerender" href="https://yld.io" />

Document-aware optimization

Learn navigation patterns

...and many other optimizations

HTTP 1.1

keep-alive connections

HTTP Pipelining (HTTP 1.1)

(image source: High Performance Browser Networking - Ilya Gregorik)

HTTP Pipelining (HTTP 1.1)

head-of-line blocking

Solution/workaround we use today

multiple TCP connections

Domain sharding

{sh1, sh2, sh3, sh4, sh5, sh6}.yld.io

Concatenation

myscript.js

anotherscript.js

stylesheet.css

bundle.js

Spriting

.default {
  background-image: url('image.png');
  background-repeat: no-repeat;
  width: 40px;
  height: 60px;
  background-position: 0 0;
}

GOAL

Decrease latency

(again!)

Introducing HTTP/2

Introducing HTTP/2

Introducing HTTP/2

published in 2015

based on SPDY

extends HTTP 1.x

Introducing HTTP/2

(image source: High Performance Browser Networking - Ilya Gregorik)

new Binary framing layer

Introducing HTTP/2

(image source: High Performance Browser Networking - Ilya Gregorik)

HTTP/2 features

1. Stream prioritization

2. Server push

3. Header compression

4. Flow control

HTTP/2 features

1. Stream prioritization

1

12

1

4

HTTP/2 features

1. Stream prioritization

1

12

1

4

dependencies and weights

index.html

styles.css

script1.js

script2.js

HTTP/2 features

2. Server push

(image source: High Performance Browser Networking - Ilya Gregorik)

HTTP/2 features

2. Server push

(image source: High Performance Browser Networking - Ilya Gregorik)

PUSH_PROMISE

RST_STREAM

SETTINGS

...

HTTP/2 features

3. Header

Compression

(HPACK)

(image source: High Performance Browser Networking - Ilya Gregorik)

HTTP/2 features

4. Flow Control

SETTINGS

WINDOW_UPDATE

DATA

HTTP/2 Implementations

https://github.com/http2/http2-spec/wiki/Implementations

HTTP/2 Implementations

https://github.com/http2/http2-spec/wiki/Implementations

How can I understand if a server talks HTTP/2?

(Dev Tools > Network tab)

The easy way...

(Dev Tools > Network tab)

The easy way...

....but, c'mon HTTPS!

The easy way...

browser does the hard work for us

Meet Wireshark

Meet Wireshark

Meet Wireshark

1st task - 'Decrypt' TLS

2nd task - Inspect!

Decrypt TLS

Decrypt TLS

add env var

add key location on Wireshark SSL preferences

export SSLKEYLOGFILE=~/Users/sericaia/keys/sslkeylog.log

... and let's inspect!

... and let's inspect!

... and let's inspect!

TCP handshake!

... and let's inspect!

HTTP/2 frames

HTTP/2 frames

GET https://http2.golang.org/gophertiles?latency=200

HTTP/2 frames

https://http2.golang.org/gophertiles?latency=200

Analysing a stream

https://www.wireshark.org/docs/dfref/h/http2.html

Analysing a stream: Stream ID

Analysing a stream: Protocol

Analysing a stream: HEADERS, WINDOW_UPDATE

Analysing a stream: HEADERS

Analysing a stream: DATA (finnally!)

DATA frame with the contents (image)

Analysing a stream: End stream

Wireshark helped to understand HTTP/2

HTTP/2 usage

(source: https://w3techs.com/technologies/details/ce-http2/all/all)

Sites using HTTP/2 only recently:

• quora.com

• 9gag.com

• spotify.com

• mercadolivre.com.br

• slack.com

11.3% of the trafic is served using HTTP/2

how to adopt HTTP/2?

how to adopt HTTP/2?

...

However,

some performance tricks are no longer needed...

Concatenation

Spriting

No longer needed...

Resource Inlining

One connection!

No longer needed...

Domain Sharding

How to start?

Incremental migrations!

Conclusions

• HTTP/2 is here to stay
• Strongly depends on browser and server implementations
• Complex but interesting protocol
• Wireshark may help to debug
• Expected to be globaly used soon
• HTTP 1.x is going to still need to be supported for some years

Still interested in protocols?

QUIC

(https://www.chromium.org/quic)

IPFS

(https://ipfs.io/)

Gotcha! I finally understand HTTP/2

Daniela Matos de Carvalho

SEIUM 2017 @Braga

sericaia

That's it!