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locally prefered bittorrent
From: David Farber <dave () farber net>
Date: Fri, 18 Jul 2008 03:39:54 -0700
________________________________________ 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 If not for you, please return. Any use other than the intended recipient is unauthorized. ------------------------------------------- Archives: https://www.listbox.com/member/archive/247/=now RSS Feed: https://www.listbox.com/member/archive/rss/247/ Powered by Listbox: http://www.listbox.com
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- locally prefered bittorrent David Farber (Jul 18)