The original idea was mine, and it is possible, but so far nobody has
developed a special-purpose device to do this.
> At least on the surface it would seem to be possible. There could be some
> sticking point in the guts of the D channel protocol, but:
> a. the 16k D channel is packet switched and very low usage (just
> dialing info and status, etc). It is designed to be
> aggregated into larger pipes. I'd think 12 16k Ds wouldn't
> stress a signal 64k D in the pseudo PRI.
> b. you may have to just do 11 BRIs (for 22 Bs) or do 12 BRIs (for
> 24 Bs) and waste one B channel.
It'd take a reasonably smart box to combine 11 16K B channels from BRI's
into one 64K, but there's no problem with capacity- D channel signalling
is extremely low volume.
If you aggregate 11 BRIs (22 channels), and never send any signals for the
missing one B channel, the PRI hardware will most likely not even notice.
I suppose you could also try to make a number of NI-1 BRI's channels look
like an E-1 PRI connection and fit even more into one cable...
> Note: could it be that there is some problem with this D channel
> aggregation? Our BellSouth engineer (and others) continue to tell me that
> they have to reserve 3 channels (3x64) in the switches to support EVERY
> ISDN BRI they install. Is there a problem with the D channel protocol or a
> problem with the switch manufacturers' implementation, or a problem with
> the telco configuration of the equipment? (I vote the latter).
This is a problem with their switch hardware- they need to take 3 64K
channels for each BRI served by a switch that does not natively support ISDN,
if they bought better hardware they wouldn't have this problem.