DSP Recommendation

Answered Question
May 8th, 2007

Can anyone help me out the a recommend DSP configuration?

We have a 2811 w/ a PVDM2-16 and a VIC2-4FXO card. I would like to best utilize the DSP resources for MOH, Transfer, and conferencing. We are running CME 4.0(3). We aren't doing any VoIP over the WAN with this site yet but would like to have this ability in the future. I have tried to use the DSP calculator but I really want to know what my options are for the DSP that I have, not vice versa.

Any help would be great!

I have this problem too.
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Correct Answer by rseiler about 9 years 6 months ago

Again, for all intents and purposes, a single 5510 DSP (PVDM2-16) will support *EITHER* 8 transcoding sessions *OR* 8 medium complexity audio calls (G.729a/G.729ab) *OR* 16 low complexity audio calls (G.711).

In my previous post I stated that you pretty much need to assume that a single DSP will only give you 8 channels to work with in most situations. Since it appears that you have 4 channels of hardware analog voice, which will automatically reserve 4 DSP channels, that leaves you with 4 channels for transcoding.

As long as you configure the voice-card 0 for 'codec complexity flex' on your router and expect all hardware analog calls to terminate as G.711, then you *COULD* configure 6 transcoding sessions with a single DSP. The worst case scenerio with this config is if any of the hardware analog calls terminate with a medium complexity codec you will loose 1 or 2 of your transcoding channels during the call(s).

Let me explain it this way, the 5510 DSP when running flex software is broken up into 16 logical channels. Each of the 16 DSP channels can handle a low complexity call (G.711 or fax passthru). A medium complexity call uses the equivalent resources of 2 DSP channels to terminate the call. A transcoding session to or from a medium complexity call (G.729a/G.729ab) from G.711 uses 2 DSP channels.

Have you ever used the DSP calculator on Cisco's web site?

http://www.cisco.com/cgi-bin/Support/DSP/dsp-calc.pl

CLI Information for Optimal results.

To match the DSP Calculator configuration with your router, enter the following commands in configuration mode in your Cisco 2811 router:

!Optimal Results

voice-card 0

codec complexity flex

!Set of Conferencing/Transcoding commands when used with PVDM2-XX DSPs:

sccp local

sccp ccm identifier version

sccp

!

sccp ccm group 999

bind interface

associate ccm priority 1

associate profile register

!

dspfarm profile transcode

maximum sessions 6

associate application SCCP

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gogasca Tue, 05/08/2007 - 18:31

Since you have, PVDM2-16.

You will have only either conference or xcoder&voice termination. not both. you will have to buy more DSPs...

mlitka Wed, 05/09/2007 - 05:51

OK. Are the resources shared then between transcoding and voice termination? Or do I have to set them up individually? Any recommendations there?

Chris Deren Wed, 05/09/2007 - 09:08

DSP can be shared between voice termination and transcoding sessions, but conference DSPs cannot be shared.

Chris

mlitka Wed, 05/09/2007 - 09:13

Can you provide an example? Is voice termination rolled up into the transcoding piece?

mlitka Thu, 05/10/2007 - 06:41

I am using FXO ports in this particular config:

sccp ccm group 1

bind interface Vlan406

associate ccm 1 priority 1

associate profile 1 register mtp001aa18f8108

!

dspfarm profile 1 transcode

codec g711ulaw

codec g711alaw

codec g729ar8

codec g729abr8

codec gsmfr

maximum sessions 8

associate application SCCP

I am unable to dial out with the maximum sessions set to 8 here. If I lower it I can then dial out on the FXO port through a pots dial peer.

mlitka Thu, 05/10/2007 - 06:56

Configured with max sessions 8:

SE_2811#show voice dsp

DSP DSP DSPWARE CURR BOOT PAK TX/RX

TYPE NUM CH CODEC VERSION STATE STATE RST AI VOICEPORT TS ABORT PACK COUNT

==== === == ======== ======= ===== ======= === == ========= == ===== ============

edsp 001 01 g711ulaw 0.1 IDLE 50/0/1.1

edsp 002 02 g729r8 p 0.1 IDLE 50/0/1.2

edsp 003 01 g711ulaw 0.1 IDLE 50/0/2.1

edsp 004 02 g729r8 p 0.1 IDLE 50/0/2.2

edsp 005 01 g729r8 p 0.1 IDLE 50/0/3.1

edsp 006 02 g729r8 p 0.1 IDLE 50/0/3.2

edsp 007 01 g729r8 p 0.1 IDLE 50/0/18.1

edsp 008 01 g729r8 p 0.1 IDLE 50/0/19.1

----------------------------FLEX VOICE CARD 0 ------------------------------

*DSP VOICE CHANNELS*

CURR STATE : (busy)inuse (b-out)busy out (bpend)busyout pending

LEGEND : (bad)bad (shut)shutdown (dpend)download pending

DSP DSP DSPWARE CURR BOOT PAK TX/RX

TYPE NUM CH CODEC VERSION STATE STATE RST AI VOICEPORT TS ABRT PACK COUNT

===== === == ========= ======= ===== ======= === == ========= == ==== ============

*DSP SIGNALING CHANNELS*

DSP DSP DSPWARE CURR BOOT PAK TX/RX

TYPE NUM CH CODEC VERSION STATE STATE RST AI VOICEPORT TS ABRT PACK COUNT

===== === == ========= ======= ===== ======= === == ========= == ==== ============

C5510 001 01 {flex} 8.4.1 alloc idle 0 0 0/0/0 02 0 46/0

C5510 001 02 {flex} 8.4.1 alloc idle 0 0 0/0/1 06 0 36/0

C5510 001 03 {flex} 8.4.1 alloc idle 0 0 0/0/2 10 0 36/0

C5510 001 04 {flex} 8.4.1 alloc idle 0 0 0/0/3 14 0 36/0

------------------------END OF FLEX VOICE CARD 0 ----------------------------

mlitka Thu, 05/10/2007 - 07:07

This is also a bit of the config under telephony-service

sdspfarm units 1

sdspfarm transcode sessions 16

sdspfarm tag 1 mtp001aa18f8108

twissam Sat, 05/12/2007 - 06:36

Hi Chris,

Are you sure? because SRND does not same the same. May be can share them as you said but 8 will be lost. i hope someone could explain this.

++++++++++++++++++++

1DSP=PVDM2-16=8 calls for voice termination= 8 transcoding sessions, even if we need only 4 or 2

Cisco Unified IP Phones use only the G.729a variants of the G.729 codecs. The default for a new

DSP farm profile is G.729a/G.729ab/G.711u/G.711a. Because a single DSP can provide only one

function at a time, the maximum sessions configured on the profile should be specified in multiples

of 8 to prevent wasted resources.

Reference SRND IP Telephony

+++++++++++++++++++++

Good day

rseiler Tue, 05/15/2007 - 14:20

The PVDM2-16 is a *SINGLE* DSP with 16 channels of G.711 audio codec or 8 channels of G.729a/G.729ab audio codec or 8x8 G.711 conferencing or 2x8 party mixed mode conferencing or 8 transcoding channels.

Note that in most cases you have either 8 channels of transcoding or 8 channels of medium complexity (G.729a/G.729ab) voice, depending on the analog voice hardware installed in the router. *NOT* both combined. Usually, the voice ports grab DSP channels and they cannot be freed, therefore *ONLY* the leftover DSP channels can be used for transcoding.

In your case, you have a max of 4 channels of transcoding available...

mlitka Wed, 05/16/2007 - 04:37

Per your calculations, how did you come up with the 4 channels of transcoding? How many channels of G.711, G.729a/G.729ab does that leave me? 12?

Correct Answer
rseiler Wed, 05/16/2007 - 09:06

Again, for all intents and purposes, a single 5510 DSP (PVDM2-16) will support *EITHER* 8 transcoding sessions *OR* 8 medium complexity audio calls (G.729a/G.729ab) *OR* 16 low complexity audio calls (G.711).

In my previous post I stated that you pretty much need to assume that a single DSP will only give you 8 channels to work with in most situations. Since it appears that you have 4 channels of hardware analog voice, which will automatically reserve 4 DSP channels, that leaves you with 4 channels for transcoding.

As long as you configure the voice-card 0 for 'codec complexity flex' on your router and expect all hardware analog calls to terminate as G.711, then you *COULD* configure 6 transcoding sessions with a single DSP. The worst case scenerio with this config is if any of the hardware analog calls terminate with a medium complexity codec you will loose 1 or 2 of your transcoding channels during the call(s).

Let me explain it this way, the 5510 DSP when running flex software is broken up into 16 logical channels. Each of the 16 DSP channels can handle a low complexity call (G.711 or fax passthru). A medium complexity call uses the equivalent resources of 2 DSP channels to terminate the call. A transcoding session to or from a medium complexity call (G.729a/G.729ab) from G.711 uses 2 DSP channels.

Have you ever used the DSP calculator on Cisco's web site?

http://www.cisco.com/cgi-bin/Support/DSP/dsp-calc.pl

CLI Information for Optimal results.

To match the DSP Calculator configuration with your router, enter the following commands in configuration mode in your Cisco 2811 router:

!Optimal Results

voice-card 0

codec complexity flex

!Set of Conferencing/Transcoding commands when used with PVDM2-XX DSPs:

sccp local

sccp ccm identifier version

sccp

!

sccp ccm group 999

bind interface

associate ccm priority 1

associate profile register

!

dspfarm profile transcode

maximum sessions 6

associate application SCCP

mlitka Fri, 05/18/2007 - 11:48

What part do the following statements play:

sdspfarm units 1

sdspfarm transcode sessions 16

sdspfarm tag 1 mtp001aa18f8108

in relation to what you have above? Do I still need these statements?

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