Station-wagons and electrons

cd /pub cat beer > /dev/bluesmoon Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Not stuck in a cloud of volcanic ash Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Didn’t get sidetracked on my way here Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Didn’t go on an extended vacation Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Almost not allowed in Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Philip Tellis geek yahoo @bluesmoon http://bluesmoon.info/ philip@bluesmoon.info Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Station wagons and Electrons Philip Tellis / philip@bluesmoon.info Yahoo! London Pub Night – May 27, 2010 – Wallacespace Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Never underestimate the bandwidth of a station wagon speeding down the motorway – Andrew S Tanenbaum? Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Should you fly a 747 or a 737? A 747 seats 400+ passengers A 737 seats about 150 Both take about the same time to fly from FRA to LHR A 747 takes longer to load and unload The best selling aircraft to date is the 737 This analogy would have been much cooler if the Concorde still flew Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Bandwidth and Latency How much data can you transfer at once v/s How quickly can you get your data across Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

But bandwidth is easy Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Shannon’s Theorem S C = B × log2 (1 + ) N C – Channel capacity in bps B – Bandwidth in Hz S – Signal strength N – Noise strength – S/N measured in dB Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Bandwidth can be bought Bandwidth has increased steadily over time Networks, hard drives, memory, CPU, system bus, everything. Bandwidth can be parallelised Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Diminishing returns The beneﬁts of increased bandwidth diminish as you get fatter Ref: More bandwidth doesn’t matter (much) – Mike Belshe Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

How fast is the internet? YUI Blog measured bandwidth at 1Mbps and latency of 262ms Ref: Analysing Bandwidth & Latency – YUI Blog Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Blink The average human eye takes 300-400ms to blink Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

How fast is the internet? Akamai measured average global bandwidth at 1.7Mbps Ref: State of the Internet – Akamai Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

ISPs Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

UK ISPs Keep in mind that the Internet latency from the UK to the US is 90-100ms Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Latency – not so easy to sell Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Speed Limits 3 × 108 m /s – in vacuum 2 × 108 m /s – in ﬁbre =⇒ 26.42ms × 2 (roundtrip from BOS to LON) Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Round-trip It should take a packet around 53ms to go from Boston to London and back It actually takes around 90ms for a packet to go from Boston to London and back This is pretty good as far as approaching theoretical limits goes Ref: It’s the latency, stupid – Stuart Cheshire Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

But then again... Never underestimate the data-transfer capabilities of a Galaxy class starship travelling at Warp 9.875 and ﬁtted with a computer that sounds like Majel Barett Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Latency isn’t sexy When was the last time you saw a TV commercial mention latency? Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

ISPs Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

UK ISPs Keep in mind that the Internet latency from the UK to the US is 90-100ms Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Latency v/s Bandwidth Improving latency tends to improve perceived bandwidth Improving bandwidth utilisation can potentially worsen latency Larger/complex packets take more time to assemble This is the difference between a 737 and a 747 Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Getting around latency problems Don’t add latency – It’s bad enough without us adding to it Caching – Bring the data closer to where it’s needed Parallelise – Reduce the number of serial roundtrips Predict – Get data before it’s needed Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

If you can, stuff everything into one call Have a look at search.yahoo.com load up in ﬁrebug Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Parallelise where possible Downloading a script blocks page load, so do it in the background instead Browsers will download 4-8 resources from a host in parallel, take advantage of that Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Predict what’s next and fetch it If you know what the user will do next, pre-fetch it Yahoo! Search page pre-loads sprites and Javascript for the results page Log analysis can tell you which pages are most popular, and pre-fetch those Ref: Preload CSS & JS without execution – Stoyan Stefanov Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Measure your user’s bandwidth & latency Javascript code to measure your user’s bandwidth & latency http://bluesmoon.info/perf-tests/bw/bw-test-1.3.zip http://github.com/bluesmoon/netperf-js It’s what we used on the YUIBlog test Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Useful tools for performance analysis YSlow – Firefox/Firebug plugin from Yahoo! PageSpeed – Firefox/Firebug plugin from Google PageTest – Web page testing tool ShowSlow – Automated YSlow runs against your URL Fiddler – Web debugging Proxy Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Further reading developer.yahoo.com/performance – Yahoo! code.google.com/speed/page-speed/docs/rules_intro.html – Google slideshare.net/stoyan/the-business-of-performance – Stoyan Stefanov stevesouders.com/blog/ – Steve Souders phpied.com – Stoyan Stefanov Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Stay tuned... Coming this summer... to an interweb near you Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Stay tuned... BOOMERANG 2010 06 24 STARRING: JAVASCRIPT, APACHE, YAHOO SCRIPT: BLUESMOON, PRODUCTION: TOM CROUCHER, CHOREOGRAPHY: CROCKFORD http://developer.yahoo.net/blog Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Photo credits flickr.com/photos/sully_aka__wstera2/4538240734/ flickr.com/photos/gertcha/4168724489/ flickr.com/photos/30720140@N08/4290289036/ flickr.com/photos/dharmasphere/253277654/ flickr.com/photos/gi/117771718/ flickr.com/photos/siennaisalive/4436708323/ flickr.com/photos/vlastula/300102949/ flickr.com/photos/electrichamster/3160580687/ flickr.com/photos/burnblue/308441464/ Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Contact me Philip Tellis yahoo geek @bluesmoon http://bluesmoon.info/ slideshare.net/bluesmoon philip@bluesmoon.info Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

Thank you Yahoo! London Pub Night – May 27, 2010 – Wallacespace Station wagons and Electrons

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Station-wagons and electrons

by Philip Tellis

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