The SPDY protocol has been developed by Google since 2009. It is intended as an evolution of HTTP with better performance and network utilization.

1. Andreas Bjärlestam 2012-02-23

2. SPDY quick overview
• An evolution of HTTP
• Developed by Google since 2009
• Openly available spec

3. Why the hell would you want to
replace HTTP?

4. HTTP is fantastic
it has totally changed the world

5. but…

6. HTTP is over 20 years old
HTTP 1.1 is 12 years old

7. Webpages in 1999

9. Webpages in 2012

11. Mobile internet usage
source: svenskarnaoch internet 2011 https://www.iis.se/docs/SOI2011.pdf

12. This is how more and more of us
consume the web…

13. Often it feels a lot like…

14. People no longer have patience to
wait for slow pages

15. Web pages February 2012
• www.facebook.com - ca 100 http requests
• www.bostonglobe.com - ca 100 http requests
• www.svtplay.se - ca 90 http requests
• www.aftonbladet.se - ca 350 http requests
source: http://httparchive.org/

16. What does it look like over the
network fetching 100 resources?

18. Can you spot the problem?

19. Its all synchronous

20. How come an advanced page like
facebook.com loads in under 4
seconds when its all synchronous?

21. Hacky optimizations
CSS sprites
base64 images in data-urls
CSS concatenation
JavaScript concatenation

22. 6 x HTTP connections
HTTP/TCP
HTTP/TCP
HTTP/TCP
HTTP/TCP
HTTP/TCP
HTTP/TCP

23. What is the problem with this? Why
not even more?

24. Wasted resources

25. TCP Congestion control

26. 2 connections per host recommended
by HTTP 1.1 spec
6 connections in most browsers

27. Domain sharding
• www.bostonglobe.com - 59 connections
• www.svtplay.se - 22 connections
• www.aftonbladet.se - 118 connections
source: http://www.webpagetest.org

28. We kind of abuse TCP
when we open more
connections

29. and…

30. New TCP connections are slow

31. 3 way handshake

32. On my macbook
Ping 20ms ≈ 30ms to set up a
connection
On my mobile (3G)
Ping 300ms ≈ 450ms to set up a
connection

33. TCP Slow start
HTTP/TCP
HTTP/TCP
HTTP/TCP
HTTP/TCP
HTTP/TCP
HTTP/TCP

34. It turns out that page load time for a moderately
complex site is almost no faster over
20mbits/sec than over 2mbits/sec

35. So… we need to utilize our TCP
connections better

36. Enter

37. Don’t we break the web if we replace
HTTP?

38. Nope

39. The semantics of HTTP is kept

40. or in simpler words…
SPDY implements the HTTP API

41. HTTP -> SPDY
GET GET
PUT PUT
HEADERS HEADERS
POST POST
… …
Use of URLs Use of TCP Use of URLs Use of TCP

42. You can switch to SPDY with no
changes to your web application

43. SPDY runs over TCP and will not
require upgraded network
equipment

44. HTTP -> SPDY
HTTP
HTTP SPDY
TLS/SSL TLS/SSL
TCP/IP TCP/IP

45. Designed with
speed as
primary goal

46. 1 TCP connection
HTTP/TCP

47. But it will be on fire!
HTTP/TCP

48. SPDY is multiplexed

49. This is a typical HTTP session
GET
200 OK
GET
200 OK
GET
200 OK

50. Multiplexing
GET 1
GET 2
GET 3
200 OK 2
200 OK 3
200 OK 1

51. Stream priorities

52. SPDY is binary

53. Will be difficult to just fire up telnet
and hack away

54. Every decent site will be encrypted
and gzipped anyways

55. TLS/SSL is mandatory

56. Communication should be
secure by default
Users should not
have to care

57. Using SSL ensures that
communication over existing
proxies is not broken

58. ..but you will not be able to
use proxies for caching etc

59. Headers are compressed

60. How will the client know that it can
use SPDY towards a server?

61. NPN
TLS Next Protocol Negotiation

62. Server Push

63. Server Push

64. So is it worth it?

65. Google tested 25 of the
“top 100” sites

66. Average speedup
39% - 55%

67. SPDY could make your life easier
Less need for hacky optimizations
like CSS sprites, file
concatenations, domain sharding
etc

68. Should I add SPDY support to my
servers on Monday?

69. Probably not…

70. Implementations
• Apache mod_spdy
• Nginx – in roadmap
• node_spdy – requires node.js 0.7
• netty
• more…

71. Example…

72. Browsers
• Chrome (since version 6)
• Firefox 11 (turned off by default)
• (Amazon silk)

73. CDNs
• Strangeloop
• Contendo

74. CDNs
SPDY Your web
Browser
Gateway server

75. Google
• Support SPDY on most of their services
• 90% of their SSL traffic is over SPDY

76. Amazon silk
Silk SPDY SPDY HTTP The
Browser Gateway Internet

77. The spec
• Draft spec, version 3
• Plan is to submit it to IETF as input to HTTP2.0
• IETF HTTPbis WG chair recently proposed to
start work on HTTP2.0

78. Alternatives

79. HTTP Pipelining
• Not as effective as multiplexing
• Hard to implement in browser
• Opera is the only desktop browser that has a
full implementation enabled by default
• Android, IOS5 and Opera mobile browsers do
some amount of pipelining
• Not used by most proxies

80. Synchronous Pipelining Multiplexing
GET GET 1 GET 1
GET 2 GET 2
200 OK
GET 3 GET 3
GET
200 OK 200 OK 1 200 OK 2
GET 200 OK 2 200 OK 3
200 OK 3 200 OK 1
200 OK

81. Alternative transport protocols
• SCTP
• BEEP

82. Roundup
• ~ 50% Faster page loads than HTTP
• Backwards compatible with HTTP
• Better utilization of TCP
• Secured by default
• Binary + compressed
• Will likely be the base for HTTP2.0

83. Attributions
• http://en.wikipedia.org/wiki/File:US_Robotics_56K_M
odem_Front.JPG
• https://www.iis.se/docs/SOI2011.pdf
• http://www.flickr.com/photos/howi/6366423373/
• http://www.flickr.com/photos/wwarby/5110037138/
• http://www.flickr.com/photos/alicetragedy/497729529
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• http://www.flickr.com/photos/koltregaskes/624914973
/in/photostream/