BT DSL service appears to be blocking third-party VoIP

[David Farber <dave () farber net>]

Begin forwarded message:

From: "Robert J. Berger" <rberger () ibd com>
Date: October 28, 2004 2:59:07 PM EDT
To: Dewayne Hendricks <dewayne () warpspeed com>, Dave Farber 
<dave () farber net>
Subject: BT DSL service appears to be blocking third-party VoIP

[If true, this is another example of why Transport and "Content" should 
not
be owned/operated by the same entity - Rob]

BT appears to be blocking third-party VoIP
David Beckemeyer http://bdt.com/david/

http://www.toyz.org/mrblog/archives/00000173.html

I've been biting my tongue on this since I first ran across it
several months back. But now I have to say something. If someone
can prove me wrong on this, fine, I'll post a retraction, but
now I'm going to say it: British Telecom appears to be
explicitly blocking VoIP for their DSL subscribers.

I've worked with an associate to examine the situation and all
signs point to an explicit blocking of VoIP. In Cisco ACL-speak,
it appears there is a rule somewhere in the BT network being
applied to inbound packets of the form:

deny udp any eq 5060 any

What this says is "block traffic coming from external hosts to
my DSL customer if it comes from port 5060." It turns out this
is exactly the type of packets that would come from a SIP
server. It appears these packets never make it from the SIP
server to the customer at all, so this is not an issue of the
customer-side firewall.

It does not appear to be a general issue with UDP or VoIP
packets either. If a server is configured to use a different
port (not the standard SIP port of 5060), it all works fine,
even using the exact same protocols.

What amazes me about this is how blatent it is. BT is actively
blocking just this one specific type of traffic. BT obviously
knows port 5060 is the SIP port and they know this will prevent
their customers from using many (most?) VoIP services. This
means this is an intentional and willful act. And they are not
even trying to hide it. They could be smart and just drop a
packet here and there or slow some down to mess with VoIP. But
no. They brazenly block it, flat out. In our faces. Take
that. What are you going to do about it?

In the US, I think we call it restraint of trade, but I have no
idea if such things apply in the UK.

--
Robert J. Berger - Internet Bandwidth Development, LLC.
Voice: 408-882-4755 eFax: +1-408-490-2868
http://www.ibd.com


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