North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

RE: Comcast blocking p2p uploads

  • From: Scott Berkman
  • Date: Fri Oct 19 17:14:55 2007

I agree, they have been doing this in select locations for some time.  I
live in Atlanta and have seen this happening for about the 3 months, but I
have friends in the suburbs that have (or had) no issues.  I imagine they
have been deploying their traffic shaping in more and more headends.  Here
is some actual operational details:

It is reported that Comcast is using an application from Sandvine to
throttle BitTorrent traffic. Sandvine breaks every (seed) connection with
new peers after a few seconds if it's not a Comcast user. This makes it
virtually impossible to seed a file, especially in small swarms without
any Comcast users. Some users report that they can still connect to a few
peers, but most of the Comcast customers see a significant drop in their
upload speed.

The throttling works like this: A few seconds after you connect to someone
in the swarm the Sandvine application sends a peer reset message (RST
flag) and the upload immediately stops. Most vulnerable are users in a
relatively small swarm where you only have a couple of peers you can
upload the file to. Only seeding seems to be prevented, most users are
able to upload to others while the download is still going, but once the
download is finished, the upload speed drops to 0. Some users also report
a significant drop in their download speeds, but this seems to be less
widespread. Worse on private trackers, likely that this is because of the
smaller swarm size

Although BitTorrent protocol encryption seems to work against most forms
of traffic shaping, it doesn't help in this specific case.

Comcast is making no effort to determine if the traffic they are blocking
is legal or not.  No one blocks all web traffic because some sites have
illegal content or questionable/undesired material.

Personally I think this is inappropriate behavior for an ISP and I hope it
causes a mass exodus of Comcast customers.


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
Clinton Popovich
Sent: Friday, October 19, 2007 3:02 PM
To: 'Steven M. Bellovin'; [email protected]
Subject: RE: Comcast blocking p2p uploads

This is old news man, that's been happening for at least 3 months now.

Clinton Popovich
Systems Administrator
Nauticom Internet Services - An NPSI Company
2591 Wexford-Bayne Road, Suite 400
Sewickley, PA 15143
Tel: 724-933-9540
Fax: 724-933-9888
Email: [email protected]

-----Original Message-----
From: [email protected] [mailto:[email protected]xx] On Behalf Of
Steven M. Bellovin
Sent: Friday, October 19, 2007 2:51 PM
To: [email protected]
Subject: Comcast blocking p2p uploads

Not a lot more I can say, other than argghhh!

		--Steve Bellovin,