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

"Robb Topolski" <robb@funchords.com> Sun, 09 November 2008 21:06 UTC

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Date: Sun, 9 Nov 2008 13:06:35 -0800
From: "Robb Topolski" <robb@funchords.com>
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Subject: Re: [p2pi] draft-livingood-woundy-p4p-experiences-02 posted
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It seems like a broken statistic given this experiment.

If it were tightly controlled (and thus less Internet-like), all of
the downloads would have completed and the download byte amounts would
be virtually the same.

One might argue that there is virtue to these observations because a
downloader who cancels a slow download is a bad thing, because they
ultimately did not get what they attempted to download.

But is there virtue in an aborted download?  If they canceled the
download in frustration or because they simply couldn't stay connected
to the swarm long enough before being forced to quit by some other
personal oe obligation, then one could say that an aborted download is
a band thing. OTOH, an incomplete download is a good thing when a
downloader may have changed his mind (wanted to hear/see/do something
else) with less bandwidth wasted. There's just no way to know why the
user aborted the download.

Even if we did know, this experiment doesn't deal with other possible
P4P-advantaged uses such as streaming-P2P video delivery (a mode more
prone to user "taste-testing" before completing a download than
traditional file-transfer models).

Robb

2008/11/6 Ye WANG <wangye.thu@gmail.com>om>:
> Hi Haibin,
>
> Yes, the Random swarm has notable smaller finished downloads than Generic or
> Coarse Grained during the period.
>
> Since the swarm sizes (# downloading peers) are roughly equal across all
> five swarms (Richard explained this in details), we suspect that a portion
> of slow peers terminate/discard their downloads.  This is almost the same
> hypothesis pointed out by Rich Woundy.
>
> Another evidence is we do notice significantly slower peers in Random swarm,
> e.g., the slowest Random peer took 7268s (>2hours) to download the video,
> but the slowest Generic took 2725s (<1hour), the slowest Corase Grained took
> 3114s (<1hour).   Hours of downloading may make users impatient.  If the
> "tail" peers in Random swarm could suffer much lower download rates,
> presumably, the number of "terminated" peers may be larger in Random swarm.
>
> On Thu, Nov 6, 2008 at 4:09 AM, Song Haibin <melodysong@huawei.com> wrote:
>>
>> Hi Richard and all,
>>
>> >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.
>>
>> Song Haibin: From section 4.1, we can see that "The results of the trial
>> indicated that P4P can improve the speed of downloads to P2P clients", so
>> if
>> the statistics data is collected during a certain period (from July 2 to
>> July 17, 2008), then the download will be increased than the random swarm.
>> I
>> don't think each swarm has downloaded the same amount of chunk files
>> during
>> the statistic period.
>
>
>>
>>
>> Best Regards,
>> Song Haibin
>> Email: melodysong@huawei.com
>> Skype: alexsonghw
>>
>>
>>
>> >-----Original Message-----
>> >From: p2pi-bounces@ietf.org [mailto:p2pi-bounces@ietf.org] On Behalf Of
>> > Y.
>> R.
>> >Yang
>> >Sent: Thursday, November 06, 2008 10:40 AM
>> >To: Woundy, Richard
>> >Cc: p2pi@ietf.org; Livingood, Jason
>> >Subject: Re: [p2pi] draft-livingood-woundy-p4p-experiences-02 posted
>> >
>> >
>> >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
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>> >> _______________________________________________
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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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-- 
Robb Topolski (robb@funchords.com)
Hillsboro, Oregon USA
http://www.funchords.com/
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