Re: [ppsp] I-D Action: draft-ietf-ppsp-peer-protocol-02.txt

Riccardo Petrocco <r.petrocco@gmail.com> Mon, 16 July 2012 13:47 UTC

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Date: Mon, 16 Jul 2012 15:48:32 +0200
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From: Riccardo Petrocco <r.petrocco@gmail.com>
To: arno@cs.vu.nl
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Subject: Re: [ppsp] I-D Action: draft-ietf-ppsp-peer-protocol-02.txt
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Hi,

As Arno explained in the previous mail, LEDBAT was chosen to increase the
on-line
time of seeders.
The main problem with any P2P systems is the supply of bandwidth. With an
oversupplied
swarm, there is usually no problem in delivering the stream on time. If the
users don't see
any drop in performance by keeping on seeding content they already watched,
they might
stay longer in the swarm.

Wesley is definitely right, as for live-streaming LEDBAT is not the best
candidate.
I wonder if we can keep LEDBAT, as it's the ideal cc for file sharing and
VoD content, and
adjust it's queuing target delay value, to act as TCP, in case of a
live-streaming swarm.


BR,
Riccardo

2012/7/16 Arno Bakker <arno@cs.vu.nl>

> On 16/07/2012 08:11, zhangyunfei wrote:
> > Same impression as Wes. To the best of my knowledge, LEDBAT is designed
> > to be for "lower priority" apps, who is mainly running on top of TCP (at
> > least UDP and TCP are co-functioning and can switch each other). It
> > seems ppsp apps are neither"lower priority"apps when competing with
> > other traffics nor requiring both UDP and TCP running and switching.
> > So a UDP+cc(needn't considering the TCP effect) solutions seems
> appropriate.
> >
>
> Hi
>
> I think LEDBAT is useful for seeding (VOD) peers. Once they have
> downloaded the content they should ideally contribute back to the P2P
> network, but without causing disturbance for their user.
>
> It can also be useful in networks which currently have overcapacity. In
> that case, downloading at higher than the bitrate is effective use of
> resources (a megabit/s not used is a megabit/s lost), but the
> faster-than-required download should not infere with other activities of
> the user. I.e. LEDBAT should limit it when required, whilst not dropping
> the speed below approx. bitrate.
>
> Riccardo knows more about this, so perhap he can comment.
>
> CU,
>     Arno
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