PVDM capacity questions

Answered Question
Feb 20th, 2008

Question 1

I have a 2801 with (1) PVDM2-16 and (2) VWIC2-4FXO cards. With this hardware configuration I should have 8 available PVDM channels...right? So why can't I add one conference session, for example:

!

dspfarm profile 1 conference

maximum sessions 1

!

My only option for maximum sessions is "0"

Question 2.

I have a different 2801 that doesn't have any VWICs on it but it does have (1) PVDM2-16. This gateway has a conference profile that allows "maximum sessions 8". The CCM SRND states that the PVDM2 can support 8 participants (I assume per session???). 8 Participants x 8 Sessions = 64. Obviously these numbers don't add up. What am I missing here????

I have this problem too.
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Correct Answer by MARTIN STREULE about 8 years 11 months ago

One PVDM2-16 has one DSP chip on the PVDM module.

One separate chip is needed for conferencing. You need at least another PVDM2-8.

If you actually use the DSP calculator (I guess nobody does) you see that the minimum requirement for this is

1 PVDM2-16 and 1 PVDM2-8.

No config can save you...

/Martin

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MARTIN STREULE Thu, 02/21/2008 - 00:23

Answer 1:

2 x 4 FXO card = 8 calls = 16 channels (send&receive)

You need at least another PVDM2-8 for conferencing.

Answer 2:

One DSP chip can support 8 sessions (G711) or 2 sessions (G729) with max. 8 participants.

That's the way it is. The numbers are for calls only, not conferences.

Two things to remember:

You have to change the service parameter in CUCM to allow 8 participants.

The entire DSP chip is used for conference exclusively.

Hope that helps somehow.

I hope you know the DSP calculator:

http://www.cisco.com/pcgi-bin/Support/DSP/cisco_prodsel.pl

Cheers,

Martin

Paolo Bevilacqua Thu, 02/21/2008 - 14:42

Actually, for pvdm2-xx the suffix number (8, 16 32, 48, 64) can be taken directly as the number of voip calls that can be some with g711 and other low/medium complexity codecs. There is no need to divide by two.

For confirmation, use the dsp calculator on cisco website, also useful to determine conferencing dsp sizing.

Jaime Valencia Thu, 02/21/2008 - 22:10

did you enabled the dsp services dspfarm on the right voice card?

if you enable the services in a card where no PVDMs are you won't be able to use them for CFB or XCODING

do a sh diag to verify on which card the dsps are and enable the dspfarm services on that card, then try again

you can do a sh voice dsp to look at the current allocation and determine if you still have free channels

HTH

Correct Answer
MARTIN STREULE Fri, 02/22/2008 - 00:07

One PVDM2-16 has one DSP chip on the PVDM module.

One separate chip is needed for conferencing. You need at least another PVDM2-8.

If you actually use the DSP calculator (I guess nobody does) you see that the minimum requirement for this is

1 PVDM2-16 and 1 PVDM2-8.

No config can save you...

/Martin

robert-knapp Fri, 02/22/2008 - 13:39

Thanks! I didn't know that you need a separate chip. Now it all makes sense.

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