I just stumbled on a friendly document by the opposition, and it would be nice to have something with our name on it.
Go to
http://www.biamp.com/support.php
and get the June newsletter.
It also mentions IMPLICIT CobraNet channels, which is a cool feature.

Past archives, June of 06, not the current June newsletter.

Their 'implicit' channels seem to make use of Cobranet private bundles. I've seen some information on private bundles in Cirrus' documentation, but I don't know much about them and have never encountered them.
The diagram on page three showing the use of redundant Cobranet connection states that STP is required for the link between the primary and secondary switches to work correctly. That statement is incorrect.

NION has the high capacity, low latency XDAB bus for exchanging audio between different NION chassis that is not targeted at specific user defined end points . i.e. audio that is part of an overall design that spans multiple NION chassis.  BiAmp does not have an XDAB type of interconnect with which to exchange large amounts of ultra low latency audio between chassis so they use private bundles instead.
Private bundles have the same characteristics as normal bundles except they are a little more difficult to set up and the conductor does not issue permissions for them. They are a 'back channel' private connection between two devices.  I  can't think of a good reason to use private bundles when using NION or MediaMatrix.

Steve-
Just to play the Devil's Advocate...
When you are building a distributed system with NIONs (and do not have access to XDAB channels between the NIONs), it would be pretty cool to be able to configure and use the private bundles.
But, is there anything to be gained by using private bundles rather than Unicast/Multi-Unicast bundles?

Thanks to all that had input into the Working with CobraNet appendix in the latest issue of Knowledge Centre!!!
Exactly what I had in mind!!
Chapter 6 on XDAB is also great. Thanks Steve!

Josh,
There is no good reason to use private bundles in most cases. They are more difficult to set up as you need to deal with MAC addresses.
The only possible reason I can think of to use them is this: Private bundles are not supposed to require permissions from the conductor.
In a LARGE system the conductor must keep track of many devices which adds additional loading to its processor. And there are also a finite number of devices that can be issued permissions within the size of one beat packet. Use of private bundles should basically remove the need for the conductor to deal with the private bundles. Having said that,  this is how private bundles are supposed to work. When I tried using them a few years back the conductor was still issuing permissions. This was pointed out to engineering and I was told that it was fixed but I cannot find a reference to this fix in the firmware release notes. I will run an experiment on this and verify if it indeed works as expected. If it has been fixed then the fix would probably be in 2.9.14 or later. I'll get back to this forum with the results of the test as soon as it is completed.

I ran the private bundle experiment and found that the conductor is still issuing permissions for private bundles.  This has not been fixed so use of private bundles provides zero marginal performance benefit.   In that case I can see no valid reason at all to use private bundles.
The reason that BiAmp probably uses them is because they need to make connections between their chassis and want to make sure that the bundles used to do this will have no chance of also being selected by the user.

This polite request may have got lost in the private bundles discussion.
One more thing on the wonderful, great (have I made myself clear?) "Working with CobraNet" appendix, could it be made available as a separate pdf, to make it easier to send to the relevant people?
I had another request from a network administrator, and would love to just sling him the document.
Alternatively, if we could unlock the pdf, we could pull it out ourselves.
Thanks.

Regarding the 'private bundle' discussion, I think one point is being overlooked.  The BiAmp software allows wiring between two points to be automatically assigned to a CobraNet bundle so the user doesn't have to configure the Output from one box, the bundle number, the input on another box and the bundle number.  It does it all automatically, quickly and is very easy to follow the signal flow in the software.
In my opinion, the mechanism of transport is inconsequential - it could be done using private bundles, unicast or multicast.  The method of configuration is very easy in some applications (but not all).

Please see my edit above.