Re: [Bloat] bufferbloat effects on throughput

[Paolo Valente <paolo.valente@unimore.it>]

Il giorno 27/apr/2015, alle ore 14:13, Toke Høiland-Jørgensen <toke@toke.dk> ha scritto:

> Paolo Valente <paolo.valente@unimore.it> writes:
> 
>> Thanks. So, if I understood correctly, average throughput may or may
>> not be affected, but large throughput fluctuations will always occur
>> in the presence of bufferbloat.
> 
> I'm always wary of saying 'always', but I'd hazard an 'often' ;)
> 
>> Sorry for my usual refrain, but … any pointers to tests, results,
>> papers and the like?
> 
> Hmm, not sure if there's any papers dealing specifically with this.
> However, it's quite easy to provoke this behaviour. Compare, for
> instance,
> 
> http://files.toke.dk/bufferbloat/rrul-pfifo_fast-all_scaled.pdf
> 
> with
> 
> http://files.toke.dk/bufferbloat/rrul-fq_codel-all_scaled.pdf
> 
> The two top graphs on each are throughput (download and upload
> respectively).
> 

Thanks. The results shown in your graphs seem unmistakable …

One question: how can one be sure (if it is possible) that the fluctuation of the throughput of a TCP flow on a given node is caused by bufferbloat issues in the node, and not by other factors (such as, e.g., systematic drops in some other nodes along the path followed by the flow, with the drops possibly even caused by different reasons than bufferbloat)?

Thanks,
Paolo

> For the aggregate behaviour, I had some data on that in my presentation
> at the IETF in Hawaii:
> 
> http://www.ietf.org/proceedings/91/slides/slides-91-iccrg-4.pdf
> 
> -Toke


--
Paolo Valente                                                 
Algogroup
Dipartimento di Fisica, Informatica e Matematica		
Via Campi, 213/B
41125 Modena - Italy        				  
homepage:  http://algogroup.unimore.it/people/paolo/