DSP Assignment Question

[Jacob Webb]

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?

[Manish Gogna]

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

[Jacob Webb]

Hi Manish,

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

[Manish Gogna]

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

[Jacob Webb]

One more question for you, Manish. 

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

[Manish Gogna · Accepted solution]

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

[Jacob Webb]

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?

[Manish Gogna]

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

Manish

[Jacob Webb]

Thanks for all your help Manish.