Subject: [p2pi] Mythbustering P2P traffic localization

From: Enrico Marocco <[email-masked]>
Date: Thu, 26 Feb 2009 16:50:09 +0100

Hello folks,

we have just submitted a draft that tries to summarize many discussions
about possible effects (and side-effects) of P2P traffic localization:
http://www.ietf.org/internet-drafts/draft-marocco-p2prg-mythbustering-00.txt

The document is very early and the conclusions may be controversial; any
comments, feedback and contributions to improve it will be greatly
appreciated.

Apologies for cross-posting, I'm sending this email to all the lists
where some of the discussions happened; please consider addressing any
follow-up to p2prg only.

-- 
Ciao,
Enrico

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From: Arnaud Legout <[email-masked]>
Date: Fri, 27 Feb 2009 11:44:23 +0100

[Should we limit the cross posting? I believe sending this thread to 4 
mailing lists is too much
(may be this is because I am subscribed to all four)]

Hi,

here is some feeback based on what we did in [Le Blond].

section 3
We show that we can achieve much higher savings than 80% of reduction. 
The direct implication of this
result is that you can still achieve significant savings with few peers 
per ISP (per torrent).

section 4
we explain the relation between peers download completion time and 
network congestion.
With large enough network congestion you can significantly improve the 
peers download completion time.
Therefore, it is likely that the different gains shown by field 
experiments report different level of congestion
of the underlying network during the experiments.

section 8.1
you write that we did simulations. We did not, we did experiments with 
real BitTorrent clients.

section 8.2
it is not clear what you mean in "as shown in [Le Blond], the right 
balance of randomness and
  locality depends on the P2P algorithm". We did not explore several P2P 
protocols, but only BitTorrent.
We show that BT is extremely robust to high locality (as long as there 
is enough randomness within each ISP).
We cannot conclude for any other P2P protocol.

"On the other hand, P2P systems not adopting the tit-for-tat approach
  (e.g. the eDonkey network) should not be damaged by locality-based"
It is not clear to me. Peer selection (tit-for-tat like choking algo in 
BT) is not the only one factor of efficiency, there is also piece 
diversity.
Edonkey/emule also use rarest first (but a less efficient peer selection 
algorithm). Therefore, as locality adversely impact
piece diversity, my bet is that Edonkey/emule will suffer from locality.

Regards,
Arnaud.

Enrico Marocco wrote:
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-- 
Arnaud Legout, Ph.D.

INRIA Sophia Antipolis - Planète  Phone : 00.33.4.92.38.78.15
2004 route des lucioles - BP 93   Fax   : 00.33.4.92.38.79.78
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---

From: Song Haibin <[email-masked]>
Date: Sat, 28 Feb 2009 15:47:41 +0800

Hi Arnaud,

>We cannot conclude for any other P2P protocol.

I guess if locality will weaken a swarm depends on in which proportion the
pieces of the resource the local peers have; and the balance of the cotent
pieces distribution among these local peers.

>piece diversity, my bet is that Edonkey/emule will suffer from locality.

What do you mean with "less efficient" by saying "Edonkey/emule also use
rarest first (but a less efficient peer selection algorithm)"?

Regards,
Song Haibin