[cisco-voip] Understanding DSP Resources

[James Buchanan]

Hello,

Good questions. 

On the first, DSPs never come built into the board on ISR routers.

On the second, you are correct on that. Different types of calls and
different codec complexities require different numbers of DSP channels.

On the third, DSPS are used for providing hardware conferencing
resources to 1) lessen the burden on the Callmanager server, 2) save WAN
bandwidth by offloading conferencing to a local site. DSPs may also be
used to provide a media termination point when one is required. MTP
resources are used for supplementary services such as DTMF and call
transfer in certain scenarios, such as when a SIP provider is being
used. Again, having the MTP on the router lessens the burden on the
Callmanager server.

DSPs are always required to do transcoding, etc., on the ISR.

I would suggest as good reading the SRND for pretty much any version of
CallManager, but the one for UCM 6.X will be most informative.
http://www.cisco.com/go/srnd will get you there.

Thanks,

James

-----Original Message-----
From: cisco-voip-bounces at puck.nether.net
[mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of Kenny Kant
Sent: Wednesday, March 05, 2008 11:21 PM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] Understanding DSP Resources

I have a basic question on the general purpose of DSP's  and when they
are required.  From reading on this list and NetPro and other books I
understand that DSP (Digital Signal Processors ? ) are hardware chips
that come shippped on SIMM type modules.  Do they ever come built onto
the board on the newer ISR's  ?

The main purpose of these chips are to "encode" calls that come in over
PSTN interfaces into PCM audio that can be then transmitted via voice
call? Correct?  This is why sizing DSP's to match your incoming PSTN
sourced channels is important.  ???

Another function of these things are to transcode streams to and from
higher compression streams such as G729.00  These are done via DSP
farms.  I hear alot about DSP farms used for conferencing ..etc what are
some other purposes here.  In general, if you are not doing advanced
call conferencing and/or transcoding is there a need for DSP's in CME
system for general calls ephone to ephone ?

Last, can a ISR do any type of transcoding in software? or are DSP's
always required?


Thanks for helping out a newbie :)

Kenny



_______________________________________________
cisco-voip mailing list
cisco-voip at puck.nether.net
https://puck.nether.net/mailman/listinfo/cisco-voip