Presentation for W3C BR

1. Measuring latency
from the browser
Paper presented at #WebBR2015
Agustín Formoso - LACNIC Labs
simon.lacnic.net

2. @proyectosimonhttp://simon.lacnic.net
Agenda
• O projeto
• Latencia, Javascript, e TCP
• Os testes
• Próximos pasos

3. @proyectosimonhttp://simon.lacnic.net
The project

4. @proyectosimonhttp://simon.lacnic.net
The project
The problem
• Connectivity in LAC is good but not
optimal
• Presence of IXPs, but inter-country
connectivity still has to be improved
• Information about connectivity is not
easy to find or updated
The solution
• Objective
Provide representative and up-to-date
connectivity measurements to anyone
interested in them
• How
Latency measurements from many
origins, to many destinations, via
different protocols

5. @proyectosimonhttp://simon.lacnic.net
The project
Reports
BR <—> BR
BR <—> MX BR <—> Region
Connectivity information regarding a certain
country against
• The country itself
• Other countries
• The LAC region

6. @proyectosimonhttp://simon.lacnic.net
Latency
One way
• Two clocks
• Clocks sync
• Hard
RTT
• One clock
• Easier
• Everything running in one endpoint
(the application)
• Send packet and time the RTT
• Paths!

7. @proyectosimonhttp://simon.lacnic.net
Why bother with the browser?
Pros
• Standard and widely-used
technologies
• Ran at the end user
• Can trigger measurements
automatically
• Scales fast
Cons
• Browser and operating system
combination differences
- TCP connections are handled differently
by browser and OS combination!
- Browser Javascript engines vary
- OSes handle processes differently
• Need of normalising different
environments!

8. @proyectosimonhttp://simon.lacnic.net
Why bother with the browser?

9. @proyectosimonhttp://simon.lacnic.net
Why bother with the browser?
Cons
• Where is the delay happening?
• Do we need to know where is it
happening?
• Black-box test them!

10. @proyectosimonhttp://simon.lacnic.net
Latency, Javascript
and TCP

11. @proyectosimonhttp://simon.lacnic.net
Latency, Javascript and TCP
Some code
$.jsonp({
type: 'GET',
url: 'http://mytestpoint.net/1442778041426',
error: function () {
rtt = (+new Date - ts);
}
});
ts = +new Date;

12. @proyectosimonhttp://simon.lacnic.net
Latency, Javascript and TCP
Connection establishment
• TCP connection overhead
• One time only
• Keep it open

13. @proyectosimonhttp://simon.lacnic.net
Latency, Javascript and TCP
Successive “GETs”
• Used every time after TCP
connection has been made

14. @proyectosimonhttp://simon.lacnic.net
Latency, Javascript and TCP
Successive “GETs”
• High level HTTP RTT
• t0, t1, d1, d2
• data
t0
t1
}d1
}d2
If
d1→0 and
d2→0
then
t1 - t0→RTT (http)

15. @proyectosimonhttp://simon.lacnic.net
Latency, Javascript and TCP
Successive “GETs”
• High level HTTP RTT
• t0, t1, d1, d2
• data
“RTT (http)”

16. @proyectosimonhttp://simon.lacnic.net
Latency, Javascript and TCP
Comparison
• Tester running at the client
• tcpdump running at the client
• Save both tcpdump and tester
output
~200 ~210

17. @proyectosimonhttp://simon.lacnic.net
The tests

18. @proyectosimonhttp://simon.lacnic.net
The tests
Testing our tool in Browserstack
• Cloud-based testing service
aimed at web developers to
check the look & feel and
responsiveness of their sites
• We use it to run our Javascript
tool over many different OS and
browser combination
• We used automated Selenium
tests

19. @proyectosimonhttp://simon.lacnic.net
The tests
Javascript tool
• Ran in the virtual instance
• Fixed origin, fixed destination
• Simple HTTP GET
• Time the RTT
• Parallel sessions with a reference environment always present

20. @proyectosimonhttp://simon.lacnic.net
The tests
The data: first glance
~360~350

21. @proyectosimonhttp://simon.lacnic.net
The tests
The data: time anomalies

22. @proyectosimonhttp://simon.lacnic.net
The tests
The data: serious time anomalies

23. @proyectosimonhttp://simon.lacnic.net
The tests
The data: IQR filtering

24. @proyectosimonhttp://simon.lacnic.net
The tests
The data: second glance
11 ms

25. @proyectosimonhttp://simon.lacnic.net
The tests
The data: adjusting it
+11 ms

26. @proyectosimonhttp://simon.lacnic.net
The tests
Normalising results
Windows 7
Windows
8.1
OS X Windows XP Windows 8
Chrome family 0 +1.9 -7.2 -1.4 +0.1
Firefox
family
-3.9 -2.8 -11.4 -4.8 -5.6
Our reference environment[Results are in ms]

27. @proyectosimonhttp://simon.lacnic.net
The tests
Normalising results
• Two distinct behaviours
- Firefox vs. Chrome
- OS X versus the rest
[Lighter blue means faster]

28. @proyectosimonhttp://simon.lacnic.net
Still…
• Uncertainties on virtualisation software
• No tests for mobile or Linux yet (~8% of seen traffic)

29. @proyectosimonhttp://simon.lacnic.net
Test conclusions
• The browser: great tool for delivering large-scale measurements but
- Huge variety
- Measurement noise can be high

30. @proyectosimonhttp://simon.lacnic.net
LAC regional
matrix
[Lighter blue means faster]
• Origins on the left
• Destinations on the top

31. @proyectosimonhttp://simon.lacnic.net
Next steps

32. @proyectosimonhttp://simon.lacnic.net
Next steps
WebResourceAPI

33. @proyectosimonhttp://simon.lacnic.net
Next steps
WebResourceAPI
• connectStart
• connectEnd
• RTT = connectEnd - connectStart
(kind of)

34. @proyectosimonhttp://simon.lacnic.net
Next steps
Doing HTTP HEAD
• No data payload!
• Get rid of big 404 pages.
}payload

35. @proyectosimonhttp://simon.lacnic.net
Next steps
• We need more tests! (currently at ~1.5K daily)
• More information at AS level
• Customised reports
• traceroutes (currently ICMP Pinging only)

36. Obrigado!
Perguntas
/LACNIC/simon Colabore!
@proyectosimon Compartilhe!
simon.lacnic.net Visite!
agustin@lacnic.net
@aguformoso