Thanks for the link to your paper.
I had a few questions about the locality discussion in the paper.
Going by the discussion in Section 3.3.2 and Section 4.1, I get the
following impression. In the experiments, increased locality has the
effect of increased number of peers in the same ISP. That is, the
population of peers is somehow unaffiliated to ISPs and locality seems
to determine the number of ISPs per peer. Locality seems to be defined
in terms of the number of inter-ISP links and the number of peers per
ISP seem to change with that. Excerpt from 3.3.2:
In all the experiments that evaluate the robustness of high
locality values, for 8 inter-ISP connections the locality values
range from 99% (for 100 peers and 10 ISPs) to 99.998% (for
10 000 peers and 5 000 peers per ISP), and for 80 inter-ISP
connections, the locality values range from 90% (for 100
peers and 10 ISPs) to 99.98% (for 10 000 peers and 5 000
peers per ISP).
Is my understanding right? Or did I misinterpret the text?
I feel judging impact on download performance should ideally consider
the impact of lack of peers that participate in a swarm within the local
ISP. If I am an end-user, my concern would be more that I may not find
enough peers if a high degree of locality is enforced. I feel it is
important to add experiments that capture the problem of lack of peers
due to locality policy.
There were a few other minor questions that the paper may want to
clarify. There seem to be up to 100 bittorrent clients per node. Could a
'local download' result in two clients on the same node talking to each
other and could that lead to artificially low download times?
The other question is about the bottleneck simulation (page 5, col 2).
This is somewhat different from a real n/w having throttling some place
in the network. The paper describes a per-node throttling mechanism. In
your experiment, if an ISP spans across nodes (lets say has 200 peers),
does the Linux 'tc' traffic controller policy make sure there is no
throttling between nodes that belong to the same ISP? This might again
complicate the read on download times for local downloads.
Thanks,
Satish
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
Of
> Arnaud Legout
> Sent: Wednesday, December 03, 2008 7:50 AM
> To: Marshall Eubanks
> Cc: Le Blond, Stevens ; [email protected]
> Subject: Re: [alto] Paper on "Pushing BitTorrent Locality to the
Limit"
>
> Hi Marshall,
>
> Marshall Eubanks wrote:
> > This is not a simulation, but an experiment run on the Grid'5000
> > network with 1700 nodes. Since the lead author is subscribed to the
> > ALTO list, I am going to wonder publicly if it would be
> > possible (and sensible) to test any ALTO solution with this
> > experimental setup.
>
> I am not sure what you mean by "test an ALTO solution", but for sure
we
> can run (and are running) additional experiments
> with real data.
> Can you give a bit more details on which kind of experiments you would
> like to perform?
>
> Regards,
> Arnaud
>
>
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