Re: [p2pi] draft-livingood-woundy-p4p-experiences-02 posted

"Y. R. Yang" <yry@cs.yale.edu> Thu, 06 November 2008 02:40 UTC

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Date: Wed, 5 Nov 2008 21:40:15 -0500 (EST)
From: "Y. R. Yang" <yry@cs.yale.edu>
To: "Woundy, Richard" <Richard_Woundy@cable.comcast.com>
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Cc: p2pi@ietf.org, "Livingood, Jason" <Jason_Livingood@cable.comcast.com>
Subject: Re: [p2pi] draft-livingood-woundy-p4p-experiences-02 posted
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Hi Rich and others,

The access download of each swarm should be equal to the sum of those 
downloaded by the clients in each swarm. So if the number of downloads in 
each swarm is the same and the amount downloaded is the same, then each 
swarm should have the same access download.

First look at the amount downloaded. There are can be some differences due 
to duplicated chunks and the way we detected data chunks (there are also 
control data in the logs), but the difference appears to be small.

Now let's look at the number of downloads. During the test, each client is 
uniformly assigned to a swarm. Given the large number of clients, each 
swarm should have about the same number of clients. But there can be two 
factors for us to see different numbers of *reported* downloads: (1) some 
clients are old and may not report or the reporting of logs was not 
successful; and (2) different # of clients finished downloading (if a 
client does not finish downloading, it does not report. Laird, please 
correct me if I am wrong). I belive the first factor should be small due 
to uniform random assignment of peers to swarms.

I just looked at the data available. We did detect a smaller number of 
finished download with Random than with the P4P swarms. For example, from 
July 3 to July 10, detected # of finished download of Generic is about 5% 
more than than Random, and Coarse is 7% more than Random. From July 10 to 
July 17, Generic is 10.5% more than Random, and Coarse is 4.7% more. 
Looking at the traffic volume at Section 4.2, I see that Generic is about 
7% higher, and Coarse is about 8.5% higher. Note that # of finished 
download and volume are different due to duplicated chunks and missing 
logs.

So I would like to support the theory/guess of Rich that some users 
terminated the download prematurally and faster downloads may result in 
fewer such terminations. But it may also include factors in (1) 
differences in initial assignment due to random numbers; and (2) # of 
finished but non-reporting clients.

If you have any other suggestions, we will be more than happy to look into 
the available data more.

Richard

On Wed, 5 Nov 2008, 6:26pm -0500, Woundy, Richard wrote:

> My current theory/guess is that some users may terminated the download
> prematurely, eg due to user impatience. So faster downloads (e.g. thanks
> to P4P) may result in fewer user terminations.
> 
>  
> 
> Laird is checking the data to see if we can confirm that, or find
> another explanation.
> 
>  
> 
> -- Rich
> 
>  
> 
> ________________________________
> 
> From: Laird Popkin [mailto:laird@pando.com] 
> Sent: Wednesday, November 05, 2008 6:12 PM
> To: Robb Topolski
> Cc: Livingood, Jason; p2pi@ietf.org; Woundy, Richard
> Subject: Re: [p2pi] draft-livingood-woundy-p4p-experiences-02 posted
> 
>  
> 
> That's a good question, and Richard and I spoke about this yesterday.
> I'll be looking into the data to see what the cause is.
> 
> - Laird Popkin, CTO, Pando Networks
>   mobile: 646/465-0570
> 
> ----- Original Message -----
> From: "Robb Topolski" <robb@funchords.com>
> To: "Richard Woundy" <Richard_Woundy@cable.comcast.com>
> Cc: "Jason Livingood" <Jason_Livingood@cable.comcast.com>om>, p2pi@ietf.org
> Sent: Wednesday, November 5, 2008 5:42:51 PM (GMT-0500) America/New_York
> Subject: Re: [p2pi] draft-livingood-woundy-p4p-experiences-02 posted
> 
> I don't get the part where access network download consumption increased
> as a result of using P4P (section 4.2).  Can someone explain how that
> could happen?  
> 
> Robb
> 
> On Wed, Nov 5, 2008 at 2:29 PM, Woundy, Richard
> <Richard_Woundy@cable.comcast.com> wrote:
> 
> Reinaldo,
> 
> I can answer the easy questions. We will need some assistance from Pando
> (and Yale) for some of the other ones.
> 
> 
> >What was the file size in those experiments?
> 
> 21 megabytes. From section 2: "Pando distributed a special 21 MB
> licensed video file as in order to measure the effectiveness of P4P
> iTrackers."
> 
> 
> >How long would it take to download the file in the three different
> scenarios? I know that more consumed bandwidth in access might lead one
> 
> to conclude that file was downloaded faster...
> 
> To clarify, most of the raw data (download speed and Internet
> peering/transit traffic volumes) were collected by Pando Networks from
> their P2P clients, not collected by Comcast across its links. So my
> assumption is that the Pando client used the content size (21 MB), and
> divided by the download time to get the speed.
> 
> 
> >Was the file already seeded in Comcast's network? More specifically,
> how
> was file propagation done?
> 
> Any seeding happened outside of Comcast's network, and outside of
> Comcast's control. That's really a question for Pando.
> 
> 
> >Was PEX, DHT and others enabled in the clients?
> 
> Pando would know whether PEX was enabled. It would be safe to assume
> that with respect to this trial, DHT was NOT enabled, since Pando
> supplied the tracker. (The pTracker in the draft is a tracker operated
> by Pando.)
> 
> 
> >Was local peer discovery enabled in the clients?
> 
> Pando would know.
> 
> 
> >BTW, can broadcast/multicast peer discovery work in Cable networks?
> 
> Do you mean something like this:
> http://bittorrent.org/beps/bep_0026.html?
> 
> If so, peer discovery probably would not work over the typical last mile
> cable network. Maybe I'm wrong, but I see this protocol as intended for
> peer discovery within one's home network / LAN / WiFi network, not over
> a cable network.
> 
> 
> >So, were clients allowed to become seeders to the outside of Comcast's
> network?
> 
> Yes, they were.
> 
> As a related item, look closely at section 4.2. The amount of aggregate
> uploaded data from Comcast clients (per swarm) was about 140,000 MB. The
> amount of aggregate downloaded data from Comcast clients (per swarm) was
> about 60,000 MB or so. So the typical Comcast client uploaded more than
> twice the amount of data that it downloaded.
> 
> 
> >How much of the swarm was within Comcast and outside?
> 
> Most of the swarm was outside of Comcast. Unfortunately I don't have
> access to the size of the global swarm, but I would guess that Comcast
> clients represented no more than 15% of the swarm, and maybe as little
> as 5%. Those guesses are based on the behavior of the random swarm, e.g.
> Comcast clients uploaded to non-Comcast clients 94% of the time in the
> random swarm.
> 
> -- Rich
> 
> 
> -----Original Message-----
> From: p2pi-bounces@ietf.org [mailto:p2pi-bounces@ietf.org] On Behalf Of
> 
> Reinaldo Penno
> Sent: Wednesday, November 05, 2008 11:23 AM
> To: Livingood, Jason; p2pi@ietf.org
> Subject: Re: [p2pi] draft-livingood-woundy-p4p-experiences-02 posted
> 
> Hello Jason/Rich,
> 
> This is such an interesting draft. I'm surprised there are no questions
> about it. Maybe everybody else is part of P4P one way or another and I'm
> not
> in the 'in' crowd (;-) so I have questions.
> 
> * What was the file size in those experiments? Some post long ago said
> the
> file size in some P4P experiments was really small, as opposed to the
> top
> 100 torrents where the file size is ~1Gb. I was curious what is the
> optimization payback in terms of download time for large files as
> opposed
> small files.
> 
> * How long would it take to download the file in the three different
> scenarios? I know that more consumed bandwidth in access might lead one
> to
> conclude that file was downloaded faster but I'm not sure this is a
> straightforward conclusion.
> 
> * Was the file already seeded in Comcast's network? More specifically,
> how
> was file propagation done? All clients started from scratch and had to
> start
> pulling the file from some other side of the world and then exchanging
> pieces? This is mainly due to the discussion in 4.2.
> 
> * Was PEX, DHT and others enabled in the clients?
> 
> * Was local peer discovery enabled in the clients? BTW, can
> broadcast/multicast peer discovery work in Cable networks?
> 
> * If more clients finish downloading faster and become seeders you would
> think that for popular content Comcast's upstream bandwidth would
> increase
> due to the number of seeder in its network. So, were clients allowed to
> become seeders to the outside of Comcast's network? How much of the
> swarm
> was within Comcast and outside?
> 
> Thanks,
> 
> Reinaldo
> 
> On 11/3/08 12:49 PM, "Livingood, Jason"
> <Jason_Livingood@cable.comcast.com>
> wrote:
> 
> > For some reason the URL was cut to two lines - trying again:
> >
> >
> http://www.ietf.org/internet-drafts/draft-livingood-woundy-p4p-experienc
> > es-02.txt
> >
> >
> >
> >> -----Original Message-----
> >> From: p2pi-bounces@ietf.org [mailto:p2pi-bounces@ietf.org] On
> >> Behalf Of Livingood, Jason
> >> Sent: Monday, November 03, 2008 3:35 PM
> >> To: p2pi@ietf.org
> >> Subject: [p2pi] draft-livingood-woundy-p4p-experiences-02 posted
> >>
> >> A draft at
> >> http://www.ietf.org/internet-drafts/draft-livingood-woundy-p4p
> >> -experienc
> >> es-02.txt may be of interest to folks that have been
> >> interested in P2Pi and ALTO.  We have requested time on the
> >> ALTO agenda at IETF 73 to present this.
> >>
> >> Regards
> >> Jason
> >> _______________________________________________
> >> p2pi mailing list
> >> p2pi@ietf.org
> >> https://www.ietf.org/mailman/listinfo/p2pi
> >>
> > _______________________________________________
> > p2pi mailing list
> > p2pi@ietf.org
> > https://www.ietf.org/mailman/listinfo/p2pi
> 
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> 
> 
> 
> -- 
> Robb Topolski (robb@funchords.com)
> Hillsboro, Oregon USA
> http://www.funchords.com/
> 
> _______________________________________________ p2pi mailing list
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> 
> 
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