HTTP/2.0 101 Introduction

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HTTP/2.0 101 Introduction @BastianHofmann

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https://www.ﬂickr.com/photos/duncan/3171592427/

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https://commons.wikimedia.org/wiki/File:Internet1.jpg#/media/File:Internet1.jpg

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https://www.ﬂickr.com/photos/neilsingapore/3567378586/

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HTTP/0.9 http://www.w3.org/Protocols/HTTP/AsImplemented.html 1991

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HTTP/1.0 https://tools.ietf.org/html/rfc1945 1996

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HTTP/1.1 http://tools.ietf.org/html/rfc2616 1999

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HTTP/1.1 http://tools.ietf.org/html/rfc2616 http://tools.ietf.org/html/rfc7230 http://tools.ietf.org/html/rfc7231 http://tools.ietf.org/html/rfc7232 http://tools.ietf.org/html/rfc7235 http://tools.ietf.org/html/rfc7234 http://tools.ietf.org/html/rfc7233 2014

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https://www.ﬂickr.com/photos/offshore/1433329174/

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No content

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http://www.impressivewebs.com/importance-of-website- performance-sources/

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Average page size

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http://www.soasta.com/blog/page-bloat-average-web-page-2-mb/

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Average asset count

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http://httparchive.org/trends.php

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The internet gets slower and slower

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https://www.ﬂickr.com/photos/91026431@N05/8497636527/

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Slow connections

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High latency

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https://ﬂic.kr/p/KpBcj

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It’s hard work to keep a page fast

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Lots of hacks around HTTP needed

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It needs to get better

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SPDY

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HTTP/2 http://tools.ietf.org/html/rfc7540 http://tools.ietf.org/html/rfc7541 2015

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New possibilities for web applications

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Increased performance

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Old truths may not be valid anymore

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HTTP/1.1 in detail

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User enters URL

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DNS lookup

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TCP connection

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TLS handshake

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This already takes time

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Finally: HTTP

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HTTP request

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GET / HTTP/1.1 Host: www.researchgate.net

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GET /home HTTP/1.1 Host: www.researchgate.net pragma: no-cache dnt: 1 accept-encoding: gzip, deflate, sdch accept-language: de-DE,de;q=0.8,en- US;q=0.6,en;q=0.4 user-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2478.0 Safari/537.36 accept: text/html,application/xhtml +xml,application/xml;q=0.9,image/webp,*/*;q=0.8 cache-control: no-cache cookie: …

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https://www.ﬂickr.com/photos/40987321@N02/5580348753/

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HTTP response

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HTTP/1.1 200 OK Content-Type: text/plain Content

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HTTP/1.1 200 OK Date: Sun, 16 Aug 2015 11:21:31 GMT Content-Type: text/html; charset=utf-8 Transfer-Encoding: chunked Connection: keep-alive Cache-Control: must-revalidate, no-cache, no-store, post-check=0, pre-check=0, private X-Correlation-Id:... expires: Thu, 19 Nov 1981 08:52:00 GMT pragma: no-cache X-UA-Compatible: IE=Edge X-Frame-Options: SAMEORIGIN P3P: CP="..." X-Content-Type-Options: nosniff X-XSS-Protection: 1; mode=block Strict-Transport-Security: max-age=7200 Content-Security-Policy: … Content-Encoding: gzip

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HTTP/2

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For the user it works the same

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No changes in Headers, Semantics etc

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Almost no changes in Headers, Semantics etc

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Protocol (h2) is established during TLS handshake

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:authority: www.researchgate.net :method: GET :path: / :scheme: https :status: 200 Content-Type: text/plain Content

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Changes on transport level

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TLS only

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Binary instead of textual

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Multiple requests are multiplexed over one TCP connection

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Server Push

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Header compression

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Smaller requests and responses

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Less roundtrips

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Headers are received early (1st packet)

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HTTP Response body

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HTML response

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DOM parsing

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Rendering

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Asset fetching

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Applying CSS

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Executing JS

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https://www.ﬂickr.com/photos/hangdog/10991275/

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Blocking HTML rendering

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CSS

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CSS triggers repaints

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JS can manipulate the DOM

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JS can access attributes set by CSS

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HTTP/1.1 200 OK Content-Type: text/html <script src="app.js" /> <script> // some JS

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Lots of assets

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HTTP/1.1

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Every request one TCP connection

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Connection Keep Alive

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Every request blocks one TCP connection

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Network congestion

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Concurrent connection limits

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http://www.browserscope.org/?category=network

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Domain sharding

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http://c5.rgstatic.net/proﬁle.css http://c4.rgstatic.net/icon.png

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Shards should be persistent

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http://c5.rgstatic.net/proﬁle.css http://c4.rgstatic.net/icon.png

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Additional handshakes and connections

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Network congestion

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TCP Slow Start

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https://de.wikipedia.org/wiki/Transmission_Control_Protocol#/media/File:TCPSlowStartundCongestionAvoidance.svg

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Ideal number of shards

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https://codeascraft.com/2014/02/19/reducing-domain- sharding/

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Page sizes

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Less content

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GZIP

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Image compression

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Minification

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CSS

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HTML

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Debugging problems

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Sourcemaps

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=> More requests

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Less requests

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Concatenation

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https://c5.rgstatic.net/c/a9b943a25d126865806885d2fd94b5f9/javascript/combo/lib/yui3/ array-extras/array-extras-min.js&lib/yui3/oop/oop-min.js&lib/yui3/attribute-core/attribute- core-min.js&lib/yui3/event-custom-base/event-custom-base-min.js&lib/yui3/event-custom- complex/event-custom-complex-min.js&lib/yui3/attribute-observable/attribute-observable- min.js&lib/yui3/attribute-extras/attribute-extras-min.js&lib/yui3/attribute-base/attribute-base- min.js&lib/yui3/attribute-complex/attribute-complex-min.js&lib/yui3/base-core/base-core- min.js&lib/yui3/base-observable/base-observable-min.js&lib/yui3/base-base/base-base- min.js&lib/yui3/pluginhost-base/pluginhost-base-min.js&lib/yui3/pluginhost-conﬁg/pluginhost- conﬁg-min.js&lib/yui3/base-pluginhost/base-pluginhost-min.js&lib/yui3/classnamemanager/ classnamemanager-min.js&lib/yui3/dom-core/dom-core-min.js&lib/yui3/dom-base/dom-base- min.js&lib/yui3/selector-native/selector-native-min.js&lib/yui3/selector/selector-min.js&lib/ yui3/node-core/node-core-min.js

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https://c5.rgstatic.net/c/a9b943a25d126865806885d2fd94b5f9/mainbundle.js

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Spritemaps

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How to bundle

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Over fetching

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90% CSS unused

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Under fetching

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Cache invalidation

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HTTP/2

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Only 1 connection

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Fully multiplexed

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No domain sharding needed

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Low overhead for a request

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No concatenation needed

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Better cache hit ratio

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More granular loading

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Less development overhead

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No content

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https://www.ﬂickr.com/photos/ksayer/5614813296/

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Critical rendering path

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What is visible?

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What is critical?

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HTTP/1.1

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Inline critical assets

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Either inline always

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Caching?

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First request

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HTTP/1.1 200 OK Content-Type: text/html … your critical css

content

load main.css async set cookie that other css was loaded

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Subsequent request (if Cookie set)

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HTTP/1.1 200 OK Content-Type: text/html // loaded from cache

content

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Flushing critical stuff early

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Traditional approach

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Browser Server GET css & js HTTP/1.1 200 OK Content-Type: text/html GET /foo.html </head><body></body></html>

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https://developer.mozilla.org/en-US/docs/Web/HTTP/ Controlling_DNS_prefetching

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https://developer.mozilla.org/en-US/docs/Web/HTTP/ Link_prefetching_FAQ

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HTTP supports streaming

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Browser Server GET /foo.html HTTP/1.1 200 OK Content-Type: text/html </head> GET css & js

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No content

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Problems

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Headers are already sent

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Redirects

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window.location = "...";

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No content

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Proxies, servers, load balancers may buffer content

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Browsers may wait before starting to render HTML

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AJAX?

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JSON

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No content

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Caching what assets are needed

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GET /literature.AddPublicationsDialog HTTP/1.1 200 OK Content-Type: application/json { "data": {...}, "css": ["AddPublicationsDialog.css"], "js": ["AddPublicationsDialogView.js"], "html": ["addConferencePaperSelection.html"] }

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localStorage.setItem( "literature.AddPublicationsDialog", { "css": ["AddPublicationsDialog.css"], "js": ["AddPublicationsDialogView.js"], "html": ["addConferencePaperSelection.html"] } );

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No content

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No content

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HTTP/2

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Server push

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Prioritize critical assets

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Browser Server Push CSS & JS :status: 200 Content-Type: text/html </head><body></body></html> GET /foo.html

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spdy.createServer(options, function(req, res) { // push JavaScript asset (/main.js) to the client res.push( '/main.js', {'content-type': ‚application/javascript'}, function(err, stream) { stream.end('alert("hello from push stream!")'); } ); // write main response body and terminate stream res.end( 'Hello World! ' ); }).listen(443); https://www.igvita.com/2013/06/12/innovating-with-http-2.0-server-push/

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Headers X-Associated-Content

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Automated learning

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Great

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When can I use it?

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Browser support

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http://caniuse.com/#feat=http2

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Server support

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Nginx https://www.nginx.com/blog/nginx-1-9-5/

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https://httpd.apache.org/docs/2.4/mod/mod_http2.html Apache httpd

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Who is using it already?

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chrome://net-internals/#http2

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Performance best practices will evolve

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Monitor and test

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Expect more frequent HTTP protocol iterations

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Stay up to date

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https://joind.in/talk/13140

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http://twitter.com/BastianHofmann http://lanyrd.com/people/BastianHofmann http://speakerdeck.com/u/bastianhofmann [email protected]