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New Member

DSP Assignment Question

I have 2 fractional T1s (16 B-Channels), 4 BRIs and a 2-port FXO (I only plan to use one).  While adding the timeslots for the PRIs I ran out of DSPs so I had to steal some from XCode and CFB.  I now have only 4 XCode, 1 CFB, and no MTP configured on the router.  This is an MGCP gateway connected to CUCM 8.6.2.

My question is, do I really even need hardware XCode and CFB if this is local to my CUCM?  Can't I just handle all the conferencing and transcoding on the server?

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Accepted Solutions
Cisco Employee

DSP Assignment Question

It will depend on the number of codecs you define under the transcoder , the less codecs you define, more sessions you are able to configure. The total number of dsp's available on the router is the first consideration. A nice tool that you can use - DSP calculator

http://www.cisco.com/web/applicat/dsprecal/dsp_calc.html?utm_source=twitterfeed&utm_medium=twitter

Let me know if this answers your queries.

Manish

8 REPLIES
Cisco Employee

DSP Assignment Question

Hi Jacob,

Transcoding can only be configured on Routers using DSP resources. CUCM can provide you MTP / CFB and MOH resources but not transcoder. Also, CUCM MTP and CFB can only handle g711 codec.

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/7_0_1/ccmsys/a05dsp.html

HTH

'

Manish

New Member

DSP Assignment Question

Hi Manish,

So, do you think it would be wise to remove CFB completely and assign the extra DSPs to transcoding?

Cisco Employee

DSP Assignment Question

Hardware CFB uses dedicated DSP's, they won'y share the dsp channels with any other resource like a pri or transcoder. If your calls are using g711 codec for conferences then surely its a good idea to remove hardware CFB.

Manish

New Member

DSP Assignment Question

One more question for you, Manish. 

If I have 32 PRI timeslots and 8 BRI channels, how many transcoder sessions should I have available?

Cisco Employee

DSP Assignment Question

It will depend on the number of codecs you define under the transcoder , the less codecs you define, more sessions you are able to configure. The total number of dsp's available on the router is the first consideration. A nice tool that you can use - DSP calculator

http://www.cisco.com/web/applicat/dsprecal/dsp_calc.html?utm_source=twitterfeed&utm_medium=twitter

Let me know if this answers your queries.

Manish

New Member

DSP Assignment Question

Hi Manish,

That does help.  I guess I still don't fully understand DSP.  For trasncoding my profile looks like:

dspfarm profile 33 transcode 

codec g729abr8

codec g729ar8

codec g711alaw

codec g711ulaw

codec g729r8

maximum sessions 4

associate application SCCP

Does the maximum sessions 4 mean I can transcode up to 4 protocols or 4 calls?

Cisco Employee

DSP Assignment Question

It is basically four calls involving any combination of these codecs specified in the dspfarm profile.

Manish

New Member

DSP Assignment Question

Thanks for all your help Manish.

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