DSP

High Density Packet Voice Digital Signal Processor or DSP Modules (PVDM2), and (PVDM3) enables Cisco Integrated Services Routers to provide high-density voice connectivity, Conferencing, and Transcoding, and Media Termination. These resources are provided via the DSP Farm on the Router, and utilized by Call Manager.

PVDM2

  • PVMD2 8 Channel Packet Voice and Fax
  • PVDM2 16Channel Packet Voice and Fax
  • PVDM2 32 Channel Packet Voice and Fax
  • PVDM2 64 Channel Packet Voice and Fax

PVDM2 Codecs

  • High Complexity G.723, G.728, G.729, G.729b
  • Medium Complexity G.711, G.729a, G.729ab, G.726
  • Low Complexity

PVDM3

  • PVMD3 16 Channel High Density Voice, Video, Fax
  • PVDM3 32 Channel High Density Voice, Video, Fax
  • PVDM3 64 Channel High Density Voice, Video, Fax
  • PVDM3 128 Channel High Density Voice, Video, Fax
  • PVDM3 256 Channel High Density Voice, Video, Fax

PVDM3 Codecs

  • High Complexity G.728, G.729, G.729b
  • Medium Complexity G.729a, G.729ab, G.726, G.722, Fax Relay
  • Low Complexity G.711, Clear Channel, Modem Passthrough, Fax Relay

Conference Bridging

Conference Bridging with Cisco Unified Communications Manager is a software and hardware application that allows both ad hoc and meet-me voice conferencing. Each conference bridge can host several simultaneous, multiparty conferences.

Transcoding

Transcoding compresses and decompresses voice streams to match endpoint device capabilities. Transcoding is required when an incoming voice stream is digitized and compressed (by means of a codec) to save bandwidth, and the local device does not support that type of compression. The more important aspect of a transcoder is it’s ability to switch between codecs G.711 vs. G.729 for example.

Media Termination

A Media Termination Point software device allows Cisco Unified Communications Manager to relay calls that are routed through SIP or H.323 endpoints or gateways. You can allocate a media termination point device because of DTMF or RSVP requirements. When a media termination point is allocated for RSVP, you can insert it between any type of endpoint device, including SIP or H.323 devices.

Low Complexity Codecs

  • G.711, Fax Passthrough, Modem Passthrough, and Clear Channel

Medium Complexity Codecs 

  • G.726, G.729A, G.729AB, G.722, and T.38 Fax Relay

High Complexity Codecs

  • G.729, G.729B, G.723, G.728, iLBC, GSM-AMR, T.38 SG3 Fax, and Modem Relay

DSP Calculator

Cisco has a great online Tool called the DSP Calculator however using the Calculator requires a valid CCO login. So if you planning on using it you will have to create a CCO login if you don’t already have one.

SCCP or Skinny Call Control Protocol

The Skinny Client Control Protocol or SCCP is the Cisco standard for real-time calls and conferencing over Internet Protocol (IP). With SCCP a Cisco IP Phone can co-exist in an H.323 environment. When Cisco CallManager is coupled with an H.323 Gatekeeper or an MGCP Call Agent, a Cisco ATA or DSP Farm running SCCP interoperates with H.323 terminals on the far end to establish, control and clear audio calls.

Building The DSP Farm

R1#configure terminal
R1(config)#voice-card 0
R1(config)#dspfarm
R1(config)#dsp services dspfarm

Watch your identifier and priority. This should coincide with your Call Manager Group in the Device Pool configuration. In other words the Device Pool assigned to the Phones should coincide with either the Publisher or the Subscriber.

R1(config)#sccp local GigabitEthernet0/0.2
R1(config)#sccp ccm 192.168.1.20 identifier 1 priority 1 version 7.0
R1(config)#sccp ccm 192.168.2.20 identifier 2 priority 2 version 7.0

The following profile names must be built out in Call Manager underneath the Media Resources. You can use any name that makes sense to you but they need to match. This also makes future administrations much easier. You can also define your codec complexity and needs depending on the DSP resources you have available. Depending on your Gateway the DSP resources required may vary greatly. For example a PRI ISDN / PSTN Gateway is going to require a lot more DSP resources then a standard POTS Gateway. It’s almost a 1 to 1 DSP resources for every channel of ISDN PRI.

In order to provide Call Manager with DSP resources you must first create a DSP Farm on the Router, and register it via SCCP. Once the DSP Farm is up and running Call Manager can utilize the Transcoding, Media Termination, and Conferencing that the DSP Farm provides via the Device Pool.  

R1(config)#sccp ccm group 3
R1(config-sccp-ccm)#associate ccm 1 priority 1
R1(config-sccrp-ccm)#associate ccm 2 priority 2
R1(config-sccp-ccm)#associate profile 3 register R1-MTP
R1(config-sccp-ccm)#exit
R1(config)#
R1(config)#sccp ccm group 2
R1(config-sccp-ccm)#associate ccm 1 priority 1
R1(config-sccp-ccm)#associate ccm 2 priority 2
R1(config-sccp-ccm)#associate profile 2 register R1-CFB
R1(config-sccp-ccm)#exit
R1(config)#


R1(config)#sccp ccm group 1
R1(config-sccp-ccm)#associate ccm 1 priority 1
R1(config-sccp-ccm)#associate ccm 2 priority 2
R1(config-sccp-ccm)#associate profile 1 register R1-TRANS
R1(config-sccp-ccm)#exit
R1(config)#
R1(config)#dspfarm profile 1 transcode
R1(config-dspfarm-profile)#codec g711ulaw
R1(config-dspfarm-profile)#codec g711alaw
R1(config-dspfarm-profile)#codec g729ar8
R1(config-dspfarm-profile)#codec g729abr8
R1(config-dspfarm-profile)#codec g729r8
R1(config-dspfarm-profile)#maximum sessions 2
R1(config-dspfarm-profile)#associate application SCCP
R1(config-dspfarm-profile)#exit
R1(config)#
R1(config)#dspfarm profile 2 conference
R1(config-dspfarm-profile)#codec g711ulaw
R1(config-dspfarm-profile)#codec g711alaw
R1(config-dspfarm-profile)#codec g729ar8
R1(config-dspfarm-profile)#codec g729abr8
R1(config-dspfarm-profile)#codec g729r8
R1(config-dspfarm-profile)#codec g729br8
R1(config-dspfarm-profile)#maximum sessions 2
R1(config-dspfarm-profile)#associate application SCCP
R1(config-dspfarm-profile)#exit
R1(config)#
R1(config)#dspfarm profile 3 mtp
R1(config-dspfarm-profile)#codec g711ulaw
R1(config-dspfarm-profile)#maximum sessions software 250
R1(config-dspfarm-profile)#associate application SCCP
R1(config-dspfarm-profile)#exit
R1(config)#exit
R1#

Now that we have the DSP Farm up and running, and registered with Call Manager via MGCP lets take a look at status. Notice that Router R1 has a total of 2 PVDM’s one 16 channel and the other 32 channel for a grand total of 48 channels for Transcoding, Conferencing, and Termination.

R1#show voice dsp group all

DSP groups on slot 0:
dsp 1:
State: UP, firmware: 28.3.5
Max signal/voice channel: 16/16
Max credits: 240, Voice credits: 240, Video credits: 0
num_of_sig_chnls_allocated: 16
Transcoding channels allocated: 0
Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 240, reserved credits: 0
Signaling channels allocated: 16
Voice channels allocated: 0
Credits used (rounded-up): 0
Slot: 0
Device idx: 0
PVDM Slot: 0
Dsp Type: SP2600
dsp 7:

State: UP, firmware: 28.3.5
Max signal/voice channel: 32/32
Max credits: 480, Voice credits: 480, Video credits: 0
num_of_sig_chnls_allocated: 11
Transcoding channels allocated: 2
Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 219, reserved credits: 0
Signaling channels allocated: 11
Voice channels allocated: 0
Credits used (rounded-up): 0
Group: FLEX_GROUP_XCODE, complexity: HIGH
Shared credits: 0, reserved credits: 69
Transcoding channels allocated: 0
Credits used (rounded-up): 0
Group: FLEX_GROUP_CONF, complexity: CONFERENCE
Shared credits: 0, reserved credits: 192
Codec: CONF_G729, maximum participants: 8
Sessions per dsp: 5
Slot: 0
Device idx: 0
PVDM Slot: 1
Dsp Type: SP2600

DSP groups on slot 1:
This command is not applicable to slot 1
0 DSP resource allocation failure

Routing Switching Voice Firewall Wireless