North American Network Operators Group

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RE: Comcast blocking p2p uploads

  • From: Andrew Odlyzko
  • Date: Fri Oct 19 16:38:14 2007

Has anyone (any lawyers here on the list?) investigated the legality
of this action?  With the FCC eliminating common carriage limits on
ISPs, it seems that blocking traffic to/from particular IP addresses,
etc., is acceptable.  But from this description of Comcast's activities,
it appears that they are using active measures to interfere with their
customers' actions (fooling their customers' equipment into believing the 
machines at the other end have terminated the interactions).  Could not 
this be construed as violating DMCA and a dozen other laws that have been
invoked against malicious hackers?

Andrew Odlyzko


  > On Fri Oct 19, Scott Berkman wrote:

  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.

    -Scott

  -----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]
  Web: http://www.nauticom.net

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


  http://www.nytimes.com/aponline/technology/AP-Comcast-Data-Discrimination.
  ht
  ml
  http://www.nytimes.com/aponline/technology/AP-Comcast-Data-Discrimination-
  Te
  sts.html

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


  		--Steve Bellovin, http://www.cs.columbia.edu/~smb