locally prefered bittorrent

[David Farber <dave () farber net>]

________________________________________
From: kevinmarks () mac com [kevinmarks () mac com]
Sent: Friday, July 18, 2008 2:49 AM
To: David Farber
Cc: ip
Subject: Re: [IP] READ  Marketplace story on FCC and Comcast

If you want locality preferred, I suggest you encourage adoption of
this protocol locally:

http://www.bittorrent.org/beps/bep_0026.html

On Jul 13, 2008, at 5:51 PM, David Farber wrote:

> ________________________________________
> From: Dr. Lawrence Roberts [lroberts () anagran com]
> Sent: Sunday, July 13, 2008 8:38 PM
> To: DV Henkel-Wallace; lroberts () anagran com
> Cc: David Farber
> Subject: Re: [IP] Marketplace story on FCC and Comcast
>
> DV,
> Re "all it can get":
> Today TCP/IP networks use as the basic fairness, "all flows get
> equal capacity". This is a result of our thinking in the early days
> where each person had one flow in each direction like a voice call.
> But today, an application can start up 100 or 1000 flows. Each flow
> gets "all it can", perhaps 100 Kbps. So do other users on the same
> cable or DSLAM. But the P2P application started 100 flows so it
> gets 10 Mbps and the other users still get 100 Kbps. That is
> fairness as the network works today. If you wished your FTP to
> operate at 10 Mbps, you also could start 100 flows and send a part
> of the file in each one. Then others would do this and soon all
> your flows would be operating at 10 Kbps since the cable is
> overloaded and must slow them all down. This is the problem we face
> today with P2P. It is better at getting capacity than any normal
> application. So a few users get most of the capacity.
>
> Re modeling:
> The problem is simple to model after observing the behavior of P2P
> programs. It is at layers 3 & 4 not 7. The P2P application finds a
> list of other users with a movie the user wants. It opens a flow to
> get part of the movie from the first other site. There is no
> concern about closeness in the net, in fact a majority of these
> flows go overseas. Then it opens a flow to another site and starts
> getting another part of the movie. It keeps doing this so long as
> it keeps increasing its total throughput or runs out of sites. When
> many P2P applications are in the same University, they all add
> flows out across the Internet access (since close is unlikely) and
> soon the Ineternet trunk is congested, and reduces the rate of
> every flow. The P2P applications then generate more flows at the
> lower rate and push the normal users rate down. In the end, 5% of
> the users have got 95% of the capacity and the average user is
> operating at 5% of the rate he could have without the P2P. Thats
> how it works today. Yes it would be better to share within the
> campus LAN  but there is no incentive to do this for the
> application. Nor does it know which users are close in general.
>
> Larry
>
>
> At 03:22 PM 7/13/2008, DV Henkel-Wallace wrote:
> From: Dr. Lawrence Roberts [lroberts () anagran com]
> Sent: Saturday, July 12, 2008 11:43 PM
>
> ...In fact, as I have been testing and modeling P2P I find it taking
> up even higher fractions of the capacity as the total capacity
> expands. This is because each P2P app. can get more capacity and it
> is designed to take all it can. ...But raise the capacity per user
> and the capacity of the upstream choke point and watch out! P2P can
> consume virtually any capacity.
>
> Dr Roberts, I am afraid I don't understand.  Any server application is
> designed to take (i.e. provide) all it can, and these applications are
> merely combinations of servers and clients.    Somehow nobody
> complains that an ftp server is "using all the bandwidth it can" nor
> usually do people complain about users "ftping to their site all that
> they can."
>
> I'm curious about your modeling.  It's not really possible to
> adequately model the behavior of anything at layer 7 (which at the end
> of the day is really all these apps are) in a conventional lab
> setting, but I presume you have the university traffic to work with.
> It does seem to me that universities might be ideal communities of
> interest: presumably if they're downloading ISOs it's mostly the same
> ISOs; if they're downloading movies or whatnot it's likely mostly the
> same.  Do you see this?  Is there much internal sharing (and thus
> presumably decreased use of the backbone)?  Does the network
> management prevent the P2P system from understanding who's "close" (or
> are the apps merely poorly written)?
>
> Thanks!
> -d
>
>
>
> Dr. Lawrence G. Roberts,  Ph:+1 650-906-8746,  W:
> www.anagran.com<http://www.anagran.com/>, E:    lroberts () anagran com
> Founder, Chairman, Chief Architect, Anagran, Inc., 580 Pastoria
> Ave., Sunnyvale, CA 94085 USA
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