Estimating Packet Loss Rate in the Access Through Application

ACM SIGCOMM Workshop on MeasurementsUp and Down the Stack (W-MUST) 2012

Estimating Packet Loss Rate in the Access Through Application-Level

Measurements

*Nexa Center for Internet & Society, DAUIN, Politecnico di Torino+DET, Politecnico di TorinoǂDAUIN, Politecnico di Torino

S.Basso* M.Meo+ A.Servettiǂ J.C.De Martin*

Helsinki, 17 August 2012

17 August 2012 Simone Basso – Politecnico di Torino 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)

http://bit.ly/GQ6FEK

http://neubot.org/


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

http://measurementlab.net/


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


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)


Step #1: evaluation in atestbed environment


Testbed experiments results


Step #2: evaluation with controlled Internet experiments


Controlled experiments results


Step #3: evaluation in testbed emulating an ADSL connection


Results of testbed emulatingan ADSL connection


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?


Thank you for your attention!

Simone Basso ([email protected])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

mailto:[email protected]

http://nexa.polito.it/

http://neubot.org/

http://twitter.com/neubot

http://facebook.com/neubot


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

Documents

Estimating Packet Loss Rate in the Access Through Application