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Re: Fwd: SlashDot: "Comcast Gunning for NAT Users"

  • From: E.B. Dreger
  • Date: Thu Jan 31 17:53:00 2002

> Date: Thu, 31 Jan 2002 16:09:47 -0600
> From: Eric A. Hall <[email protected]>

(Put "SlashDot" in the title, and the thread suffers the

> "Bill Woodcock" <[email protected]> wrote:
> > Can you think of a way of doing it reliably?  Anything that
> > provides anything more than a guess?
> Several ways:
>   Comcast has a mail server, they could poke at the HELO
>   banners and other identifiers.

Can be overridden by an SMTP proxy.  Relay the message, drop the
old "Received:" lines, and perhaps mutate the message ID.

>   HTTP proxies indicating that multiple browsers are in use,
>   especially if multiple platforms (Win95, WinXP, as simple

Can also be overriden by Squid, among others.

>   More than ~4 simultaneous TCP connections open at once.

I'm known to download four or five large tarballs, run a couple
rsync sessions, and browse the Web with multiple browser
windows... all simultaneously.

> None of those would be bothered by firewalls or other
> legitimate devices, and would probably all be within a
> legally-defensible purview of ~analysis.

Perhaps... but false negatives and positives alike are trivial.

[ snip ]

> This is hard because they are selling bandwidth ("watch
> video") so they can't really cap the downloads, and they are
> selling always-on so they can't measure by time conveniently
> either. So they try to get the "bandwidth hogs" through
> contractual means. Comcast prohibits VPNs, and prohibits
> ~"attaching to another network", as examples. If you use too
> much bandwidth, they will use these to drop your service.

There it is... how many bits is the customer actually moving?

As for the person who mentioned modifying Linux IP code to alter
the port range... it's a simple set of sysctl tunables in BSD
(at least FreeBSD).


Brotsman & Dreger, Inc. - EverQuick Internet Division
Phone: +1 (316) 794-8922 Wichita/(Inter)national
Phone: +1 (785) 865-5885 Lawrence

Date: Mon, 21 May 2001 11:23:58 +0000 (GMT)
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