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The Case for HTTP/2

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Slides to accompany my introduction to HTTP/2 talk from Texas JavaScript 2015

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The Case for HTTP/2

  1. 1. http://www.flickr.com/photos/arnybo/2679622216 The Case for HTTP/2 @AndyDavies #TXJS, July 2015
  2. 2. http://www.flickr.com/photos/7671591@N08/1469828976 HTTP/1.x doesn’t use the network efficiently
  3. 3. We’ve been hacking around some of the limitations https://www.flickr.com/photos/rocketnumber9/13695281
  4. 4. Each TCP connection only supports one request at a time* https://www.flickr.com/photos/39551170@N02/5621408218 *HTTP Pipelining is broken in practice
  5. 5. So browsers allowed us to make more requests in parallel Very Old browsers - 2 parallel connections Today’s browsers - 4 plus connections
  6. 6. To make even more parallel requests we split resources across hosts www.bbc.co.uk! static.bbci.co.uk! news.bbcimg.co.uk! node1.bbcimg.co.uk
  7. 7. Increasing the risk of network congestion and packet loss https://www.flickr.com/photos/dcmaster/4585119705
  8. 8. Every request has an overhead https://www.flickr.com/photos/tholub/9488778040
  9. 9. HTTP 1.x - Higher latency = slower load times PageLoadTime(s) 1 2 3 4 Round Trip Time (ms) 0 20 40 60 80 100 120 140 160 180 200 220 240 Mike Belshe - “More Bandwidth Doesn’t Matter (much)”
  10. 10. Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8 Accept-Encoding:gzip,deflate,sdch Accept-Language:en-US,en;q=0.8 Cache-Control:no-cache Cookie:NTABS=B5; BBC- UID=75620c7ca040deb7c0d3275d81c51c2361684a959e281319b3b5da4dab5958880Mozilla %2f5%2e0%20%28Macintosh%3b%20Intel%20Mac%20OS%20X%2010%5f9%5f1%29%20AppleWebKit %2f537%2e36%20%28KHTML%2c%20like%20Gecko%29%20Chrome%2f31%2e0%2e1650%2e63%20Safari %2f537%2e36; ckns_policy=111; BGUID=55b28cbc20d2e32f221f3ed0e1be9624c960f93b1e483329c3752a6d253efd40; s1=52CC023F3812005F; BBCCOMMENTSMODULESESSID=L-k22bbkde3jkqf928himljnlkl3; ckpf_ww_mobile_js=on; ckpf_mandolin=%22footer-promo%22%3A%7B%22segment%22%3Anull%2C%22end %22%3A%221392834182609%22%7D; _chartbeat2=ol0j0uq4hkq6pumu. 1389101635322.1392285654268.0111111111111111; _chartbeat_uuniq=1; ecos.dt=1392285758216 Host:www.bbc.co.uk Pragma:no-cache User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36 Headers sent with every request Contain lots of repeated data! and aren’t compressed
  11. 11. And small responses may not fill the TCP Congestion Window Could have sent more segments in this round-trip Small response
  12. 12. So we follow recipes e.g. Reduce Requests https://www.flickr.com/photos/nonny/116902484
  13. 13. Create CSS and JavaScript bundles ++++ = =
  14. 14. Create CSS and JavaScript bundles ++++ = =More to download and parse
  15. 15. Create CSS and JavaScript bundles ++++ = =More to download and parse x+! ! Whole bundle is invalidated if a single file changes
  16. 16. and mush images together as sprites
  17. 17. and mush images together as sprites To get just one sprite …
  18. 18. and mush images together as sprites Browser must download and decode the whole image To get just one sprite …
  19. 19. We override the browser’s priorities https://www.flickr.com/photos/skoupidiaris/5025176923
  20. 20. Embed binary* data using DataURIs url(data:image/ png;base64,iVBORw0KGgoAA AANSUhEUgAAABkAAAAZCAMAA ADzN3VRAAAAGXRFWHRTb2Z0d 2FyZQBBZG9iZSBJbWFnZVJlY WR5ccllPAAAAAZQTFRF/ wAAAAAAQaMSAwAAABJJREFUe NpiYBgFo2AwAIAAAwACigABt nCV2AAAAABJRU5ErkJggg==) = *dataURIs can be text too e.g. SVG
  21. 21. and inline ‘critical resources’ <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en-us"> <head> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <meta name="viewport" content="width=device-width, initial-scale=1.0" /> <link rel='stylesheet' href='http://fonts.googleapis.com/css?family=Open+Sans:400,300,600' typ <link rel="alternate" href="http://blog.yoav.ws/index.xml" type="application/rss+xml" title="Y <style> body { font-family: 'Open Sans', 'Helvetica Neue', Helvetica, sans-serif; color: rgb(72, 7 img { max-width: 100%; } .li-page-header { color: rgb(255, 255, 255); padding: 16px 0px; background-color: #8a1e1b; .container { position: relative; width: 90vw; max-width: 760px; margin: 0px auto; padding: .clearfix:before, .clearfix:after, .row:before, .row:after { content: '0020'; display: bl .row:after, .clearfix:after { clear: both; } .row, .clearfix { zoom: 1; }
  22. 22. There’s a tension between development and delivery https://www.flickr.com/photos/domiriel/7376397968
  23. 23. Build tools and optimisation services help plug gaps and won’t be going away…
  24. 24. But what if we could use the network more efficiently? https://www.flickr.com/photos/belsymington/4102783610
  25. 25. HTTP/2
  26. 26. HTTP/1.1 HTTP/2 https://http2.golang.org/gophertiles
  27. 27. HTTP/1.1 HTTP/2 Impressive! But is it a real world test? https://http2.golang.org/gophertiles
  28. 28. • HTTP methods, status codes and semantics remain the same! • Binary headers! • Header compression! • Multiplexed! • Server can push resources HTTP/2
  29. 29. Each request becomes a stream
  30. 30. That’s multiplexed over a single TCP connection to host HTTP/1.1 HTTP/2
  31. 31. Streams are divided into frames … Stream 1 DATA Stream 2 HEADERS Stream 2 DATA Stream 1 DATA … Stream 4 DATA Client Server
  32. 32. and prioritised using Weights and Dependencies https://nghttp2.org/blog/2014/04/27/how-dependency-based-prioritization-works/ Weight: 200 id: 2 Weight: 100 id: 4 Weight: 1 id: 6 Weight: 100 id: 12 Weight: 100 id: 8 Weight: 100 id: 10
  33. 33. and prioritised using Weights and Dependencies https://nghttp2.org/blog/2014/04/27/how-dependency-based-prioritization-works/ Weight: 200 id: 2 Weight: 100 id: 4 Weight: 1 id: 6 Weight: 100 id: 12 Weight: 100 id: 8 Weight: 100 id: 10 2/3 1/3 Low priority
  34. 34. Header compression https://http2.github.io/http2-spec/compression.html
  35. 35. Does it make any difference? Host: Ireland, Test Agent: Singapore, Cable
  36. 36. Does it make any difference? Host: Ireland, Test Agent: Singapore, Cable
  37. 37. What about when server and client are close? Host: Ireland, Test Agent: Ireland, Cable
  38. 38. and evenly matched when server and client are close Host: Ireland, Test Agent: Ireland, Cable
  39. 39. and evenly matched when server and client are close Host: Ireland, Test Agent: Ireland, Cable
  40. 40. Opportunities for new kinds of optimisations https://www.flickr.com/photos/inucara/14981917985
  41. 41. Browser Server Server! builds! page GET index.html <html><head>… Network! Idle Request other page resources Server push
  42. 42. Browser Server Server! builds! page GET index.html <html><head>… Request other page resources Push critical resources e.g. CSS Server push
  43. 43. Browser Server Server! builds! page GET index.html <html><head>… Request other page resources Push critical resource e.g. CSS Server push
  44. 44. Browser Server Server! builds! page GET index.html <html><head>… Request other page resources Push critical resource e.g. CSS Browser can reject push! but ! may have already received data Server push
  45. 45. Many opportunities for server push HTML CSS DOM CSSOM Render! Tree Layout PaintJavaScript Fonts and background images discovered when render tree builds Could we push them?
  46. 46. Multiplexing offers interesting possibilities too
  47. 47. How much of an image do we need to make it usable - 5%? Experiment by John Mellor at Google
  48. 48. Parallel version looks usable with just 15% of bytes
  49. 49. And almost complete with 25% of the image bytes!
  50. 50. Sequential version needs 80% of bytes to match up…
  51. 51. There are some questions over the user experience with progressive images Sequential version needs 80% of bytes to match up…
  52. 52. When do we kill off some HTTP/1.1 optimisation techniques? http://www.flickr.com/photos/tonyjcase/7183556158
  53. 53. Browser support for HTTP/2 is relatively good 40 Edge 9b39 30a a. Opera Mini doesn’t support HTTP/2 b. Server-Push not supported in beta
  54. 54. Server Support https://github.com/http2/http2-spec/wiki/Implementations Server implementations are getting there
  55. 55. Choose your server carefully… Does it respect stream and connection flow?! Does it support dependencies and weights?! Does it support server-push?! ! How does it help optimisation?
  56. 56. No content until DNS, TCP and TLS negotiation complete Efficient TLS is Important Session Resumption, Certificate Stapling and improvements in TLS v1.3 all help
  57. 57. Efficient TLS is Important istlsfastyet.com www.ssllabs.com/ssltestBulletproof SSL and TLS Ivan Ristic
  58. 58. https://www.flickr.com/photos/mariachily/3335708242 Still plenty of challenges…
  59. 59. Go explore! http://www.flickr.com/photos/atoach/6014917153
  60. 60. http://www.flickr.com/photos/auntiep/5024494612 ! @andydavies! ! andy.davies@nccgroup.trust ! ! http://slideshare.net/andydavies!

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