[Bloat] Unleashing Tor, BitTorrent & Co.: How, to Relieve TCP Deficiencies in Overlays

[Florian Tschorsch]

Hi Everyone,

I recently came across your project about bufferbloat. It seems that you 
are following similiar aims as we did in one of our contributions.

We analyzed the effects and implications of TCP interferences in overlay 
networks cuased by saturated interface queues. Further we show that 
traffic shaping mechanisms alone are not enough and thus propose a 
methodology to overcome this issue.


Abstract: In TCP-based overlay applications, the TCP connections of one 
peer typically share one physical Internet link. Using real-world 
experiments, we demonstrate that this can lead to undesirable 
interactions, causing significant throughput loss. We argue that such 
effects should be taken into account in the design of overlay networks, 
and identify readily deployable countermeasures. In a first step, we show 
that with existing operating system QoS functionality some relief is 
possible. Yet, this alone is not fully effective if peers communicate 
bidirectionally, due to piggybacked ACKs. We propose to separate 
bidirectionally used overlay links into two independent TCP connections, 
and demonstrate the effectiveness of this strategy.


A more in-depth discussion, including experimental results etc., has 
been accepted as a paper to last year's IEEE LCN conference (Marks, 
Tschorsch, Scheuermann: "Unleashing Tor, BitTorrent & Co.: How to 
Relieve TCP Deficiencies in Overlays"). An extended version of this 
paper (even more results...) is available as a technical report here:

http://www.cn.uni-duesseldorf.de/publications/library/Marks2010b.pdf


If you have further questions, please do not hesitate to ask.


Cheers, Florian.


-- 
Florian Tschorsch
Mobile and Decentralized Networks
Heinrich-Heine-University
Universitätsstr. 1, D-40225 Düsseldorf

Building 25.12, Room 02.43
Phone +49 211 81 11635
Fax +49 211 81 11638

tschorsch at cs.uni-duesseldorf.de
http://www.cn.uni-duesseldorf.de