[cisco-voip] Understanding DSP Resources

[Lelio Fulgenzi]

Someone mentioned that if you only have analog ports, i.e. FXS/FXO - you do 
not require DSPs. That was very interesting.

Lelio
--------------------------------------------------------------------------------
Lelio Fulgenzi, B.A.
Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
(519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
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----- Original Message ----- 
From: "James Buchanan" <jbuchanan at ctiusa.com>
To: <kenny.kant at running-config.com>; <cisco-voip at puck.nether.net>
Sent: Thursday, March 06, 2008 12:31 AM
Subject: Re: [cisco-voip] Understanding DSP Resources


> 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
>
>
>
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