All things related to multicast

[Bill Owens <>]

On Fri, Mar 24, 2006 at 11:24:27AM -0500, Richard Mavrogeanes wrote:
> VBrick has never "intentionally" send non-standard SAP messages, but we
> do use some the SDP fields in novel ways. I think the question is about
> the keyword in the SDP, and in 2004 the firmware was changed so that the
> field was not empty.  Of course, not everyone upgrades, and there are
> thousands of VBricks out there still running with early versions of the
> code (some even with 1.0!).

I think there are three separate things crossing each other here:

 - At one point in the past, at least some VBrick SAP messages were 
sufficiently different from what the code in sdr and IP/TV expected that they 
wouldn't show up in the session list. I was under the impression that this 
was intentional because VBrick's stream format couldn't be decoded by the 
RTP-based tools, and it was a way to keep users of those tools from seeing 
streams they couldn't view. That's what the discussion was about in 2002, at 
any rate.

 - Ethereal has a problem with the a=keywds field being empty, which is what 
was fixed with the firmware update in 2004 (and didn't appear to affect any 
other apps; certainly, the ones I have don't complain)

 - The machine at 129.116.74.139, which may or may not be a VBrick, but has 
the reverse name vbrick-cma5136.communication.utexas.edu, is sending 
compressed SAP messages. That's triggering the errors on the Cisco router 
with 'ip sap listen' enabled, and it can't be decoded by Ethereal, but it is 
something that the standard allows. Someone with some mad Perl or Python 
skillz could probably decode the packet with zlib, but I tried that yesterday 
and couldn't :( 

Bill.