[Asterisk-Users] Port density: DS3 cards?

[Steven Critchfield]

On Thu, 2003-12-04 at 14:06, John Todd wrote:
> Obviously, there are no DS3 TDM cards that are currently compatible 
> with Zap channels.  (or are there?)
> 
> Does anyone know of an inexpensive DS3 card that could perhaps be 
> used with Asterisk if one were to try to port the Zap drivers to such 
> a card?  PCI, of course, would be the bus of choice.

Your first problem will be bus speeds. A single DS3 is 44.736Mbps. each
way. So if you double this and get the 89.472Mbps, you are going to be
coming close to the real limits of the 32/33mhz PCI bus without having
done any work on the data you are shuffling. So while it could be done
here, I'd start worrying about stability. Sure you could switch up to
faster PCI buses like the 64/66mhz bus, but then you will start limiting
what systems you can use. Then again, if you are putting that many
channels through a single machine, there wasn't many choices for the
hardware to begin with.

My question I guess would come down to why bring a DS3 into a PC when
you could get a multiplexer that took your DS3 and split it down to T1s
so you could use already developed hardware. You could then build in
some redundancy and if a machine goes down and takes a few T1s down with
it, you just route around it till you fix it.

Figure you could go 7 1U super micros with a TE410P in each one will get
you your 28 T1s. Then either make one machine do the work of traffic cop
and connect calls between T1s or point them down the line to other
machines that can then terminate the call. Since the traffic cop machine
wouldn't need to actually service calls but for a short period during
routing, if it were to fail it would just drop any calls it was in the
middle of routing and wouldn't route new calls. In this case you could
have a hot spare waiting in the wings to do a on fail dial here type
route and it could service the new calls. In this case you have 9u of
space used and no machine can take down more than 4 T1s worth of calls.
Ohh, you need to add 1u of space fore the multiplexer. So 10u of space
for a DS3 using currently available technology and software with a bit
of failover support.  
-- 
Steven Critchfield  <critch at basesys.com>