VoIP DSP module

biggynet
biggynet used Ask the Experts™
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I am trying to get the right parts for my VoIP router. Basically, I am doing the dial-peer feature. I am planning to use the Cisco 1941. I need to get two voice cards (VWIC??) and I am not a voice guy, so I am not sure if I need a DSP module or not.
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Senior Systems Engineer
Commented:
Yes you need a DSP, depending on how many calls, conferences and codec conversions you have going on depends on how many dsp's you need.
below is a link to the number of dsp's you can put in each router.
The 1941 can have a maximum of 0, this is not good!
Im not sure if you can buy a 1941 with dsp onboard so you might want to try a show inv.

http://www.cisco.com/en/US/prod/collateral/routers/ps10538/qa_c67_553891_ps10537_Products_Q_and_A_Item.html

To know how many dsp's you need got to this link
http://www.cisco.com/cgi-bin/Support/DSP/dsp-calc.pl
I dont have a login so i cant check its working.

Author

Commented:
I have 3 sites so that would be possible 2 voice calls. I checked the Cisco site and it said that the PVDM2 or 3 for the Cisco 2900 series supports all types of codec and the minimum is the PVDM2-8. I have  calls. So do I need the DSP card? Also, how do I know what type of codec I am using? I just plug my analog phone to the router and configure dial-peer pots and VoIP.
Top Expert 2007
Commented:
Hey there,

you will need a different router, The 1900 series doesn't support voice cards or the right ios version to do what you are refering to.

http://www.cisco.com/en/US/products/ps10538/products_relevant_interfaces_and_modules.html#vic

Cisco does sell the 2901 in a voice bundle that will have a DSP module and the correct software then you would add the voice cards as needed.

Hope this helps
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greg wardSenior Systems Engineer
Commented:
How many calls can it support

http://www.cisco.com/en/US/prod/collateral/routers/ps5854/product_data_sheet0900aecd8016e845_ps3115_Products_Data_Sheet.html

Also you need more pvdms if you want conferences.

If you want to do calls using a vic-fxs then you need pvdms in all routers.
Why not set up 7941's then you only need one voice router.
As above the 1941 does not look to be suitable.

Commented:
Hi! This solution has been very useful for me today.
But I still have doubts. Hope you can help me.
My actual Carrier (who deliver us E1's with the CISCO router included) says it is possible to implement VoIP without using DSP's in the branch office router. The carrier solution designer says it is a way to do it with a bandwith cost not really defined.  
On the other hand, the engineer who is right now setting the Call Manager and checking routers capacity, says it's not possible to do it.
Who is right? Is there a way to implement VoIP without DSP's?
Thanks in advance.
greg wardSenior Systems Engineer

Commented:
Yes it is possible.
Is it possible for you: i dont know your set up, so i can t answer.
what does a PVDM do http://www.cisco.com/en/US/prod/collateral/modules/ps3115/qa_c67_553073_ps10537_Products_Q_and_A_Item.html
Can it be software

http://toritsejuokpotse.wordpress.com/2012/06/07/cucm-media-resources-the-non-journalistic-kind-pt-1/
The term media resources encompass a combination of cucm entities that perform functions like terminating media streams, mixing media streams, converting between compression types, amongst other things. They can be either software or hardware based and can be provided either by an IOS router or from the CUCM server.
Typical MR’s include:

Media Termination Points
Conference Bridges
Annunciators
Transcoders
Music-on-Hold

hope that helps

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