Presentation of the paper "Estimating Packet Loss Rate in the Access Through Application-Level Measurements", co-authored with Michela Meo, Antonio Servetti and Juan Carlos De Martin

1. ACM SIGCOMM Workshop on Measurements
Up and Down the Stack (W-MUST) 2012
Estimating Packet Loss Rate in the
Access Through Application-Level
Measurements
+
S.Basso* M.Meo A.Servettiǂ J.C.De Martin*
*Nexa Center for Internet & Society, DAUIN, Politecnico di Torino
+DET, Politecnico di Torino
ǂDAUIN, Politecnico di Torino
Helsinki, 17 August 2012

2. Rewind: Nexa Center and earlier
studies on network neutrality
● Nexa Center: academic research center that
studies the Internet from a multidisciplinary
point of view (technology, law, economics)
● January 2009 – legal analysis of 10 wired and
4 wireless Italian broadband ISPs contracts
(http://bit.ly/GQ6FEK)
● Decision to develop a software research
project to monitor network neutrality: Neubot
(http://neubot.org)
17 August 2012 Simone Basso – Politecnico di Torino 2

3. Neubot: the network neutrality
bot (active application-level tests)
● Neubot is a daemon that runs in the background and
periodically performs active tests towards servers provided
by Measurement Lab (http://measurementlab.net)
● Tests probe the end-to-end path between the user and the
server (including at least access and home network), aim at
saturating the bottleneck, run for a short amount of time (5-
10 s), emulate HTTP and BitTorrent, and perform goodput
and RTT measurements at application level
● Results are centrally collected, providing an application-
level characterization of what one can see, from the user
vantage point, using different protocols
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4. Rationale and issues of
application-level measurements
● Application-level tests are appealing because they are
simple, scalable and portable to other contexts
● Unfortunately, a lot of very useful packet-level
information is missing (e.g. retransmissions and other
TCP events)
● Of course, one cannot just compare (as in “which one is
better from the point of view of a human?”) two
measurements by the goodput alone, because the
goodput is inversely proportional to the RTT
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5. Idea: estimate packet loss rate
and use it for comparison
● We propose to invert the Mathis formula, to
estimate the packet loss rate (PLR) from RTT,
goodput and maximum segment size (MSS)
● In turn, the comparison between two
measurements will be performed in the
bidimensional (RTT, PLR) space
● The question is whether the estimation is
sufficiently robust, given that we are not working in
ideal conditions (e.g. short tests, simple RTT
estimation)
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6. Step #1: evaluation in a
testbed environment
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7. Testbed experiments results
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8. Step #2: evaluation with
controlled Internet experiments
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9. Controlled experiments results
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10. Step #3: evaluation in testbed
emulating an ADSL connection
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11. Results of testbed emulating
an ADSL connection
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12. Conclusion and future work
● It seems good enough for coarse grained
classification of application level performance
● The estimated PLR depends on the connection
speed (so that a “better” connection for the user
gets a lower PLR estimate)
● The estimated PLR still depends on the RTT:
does running tests with higher RTT for longer times
mitigates the problem?
● Does the model work reasonably for request-
response application-level patterns?
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13. Thank you for your attention!
Simone Basso (simone.basso@polito.it)
Nexa Center for Internet & Society (http://nexa.polito.it/)
Dept. of Computer and Control Engineering (DAUIN)
Politecnico di Torino, Italy
The Neubot project (http://neubot.org/)
http://twitter.com/neubot
http://facebook.com/neubot
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14. Appendix: Mathis formula
● MSS is the maximum segment size
● C is 0.93 for random losses and delayed ACKs
● RTT is the round trip time
● PLR is the packet loss rate
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