DSP, PVDM & Media Resources

The Cisco High-Density Packet Voice Digital Signal Processor (DSP) Module (PVDM2) enables Cisco Integrated Services Routers to provide high-density voice connectivity, conferencing, and transcoding capabilities in Cisco IP Communications solutions. PVDM stands for packet voice DSP module; it is the Cisco product name for the module that provides digital signal processing resources to a system. DSP stands for Digital Signal Processor; it is a generic Industry terminology. A PVDM module could be staffed with one or multiple DSPs.

PVDM2-8 = 8ch (G), 4ch (H), 4ch (M)

PVDM2-16 = 16ch (G), 6ch (H), 8ch (M)

PVDM2-32 = 32ch (G), 12ch (H), 16ch (M)

PVDM2-48 = 48ch (G), 18ch (H), 24ch (M)

PVDM2-64 = 64ch (G), 24ch (H), 32ch (M)

G=g711     H=G723.1,G728, G729, Gt29b, iLBC      M= G711, G729a, G729ab, G726, G722, Fax Relay

PVDM2-16 is one DSP chip (32=2, 48=3, 64=4)
PVDM2-8 is one DSP chip but less processing capacity than the DSP on the 16.
PVDM2-8 contains one TNETV2505GGW DSP; other PVDM2 modules contain 1 to 4 TNETV2510GGW DSPs (referred to C5510 in command outputs)

Codec Complexity and Flex Mode:

You can configure each DSP separately as either medium complexity, high complexity, or flex mode (C5510 only).Configure with voice-card x.  Then codec complexity (flex | high | medium). The DSP treats all calls according to its configured complexity, regardless of the actual complexity of the codec of the call. A resource with configured complexity equal or higher than the actual complexity of the incoming call must be available, or the call will fail.

3725 with NM-HDV in slot 0
!
Gateway#conf t
Gateway(config)#voice-card 0
Gateway(config-voicecard)#codec complexity ?
high    Set codec complexity high. High complexity, lower call density.
medium  Set codec complexity medium. Mid range complexity and call  density.
<cr>
Gateway(config-voicecard)#end

2811 with PVDM2-16 installed on main board.
!
GW_2811#config terminal
Enter configuration commands, one per line. End with CNTL/Z.
GW_2811(config)#voice-card 0
GW_2811(config-voicecard)#codec complexity ?
flex    Set codec complexity Flex. Flex complexity, higher call density.
high    Set codec complexity high. High complexity, lower call density.
medium  Set codec complexity medium. Mid range complexity and call density.

GW_2811(config-voicecard)#end
GW_2811#

For example, if a call requires a high-complexity codec but the DSP resource is configured for medium complexity mode, the call will fail. However, if a medium-complexity call is attempted on a DSP configured for high complexity mode, then the call will succeed and Cisco IOS will allocate a high-complexity mode resource.

Voice cards that do not have C5510 DSPs can be configured only for medium or high complexity. Voice cards that are equipped with C5510 DSPs have an additional complexity option called flex complexity. Setting the codec complexity to medium or high sets the number of voice terminations per DSP to a static number. Flex mode has an advantage when calls of multiple codecs must be supported on the same hardware because flex mode can support more calls than when the DSPs are configured as medium or high complexity. However, flex mode does allow oversubscription of the resources, which introduces the risk of call failure if all resources are used. With flex mode it is possible to have fewer DSP resources than with physical TDM interfaces.

DSP Sharing & Farming:

DSP sharing and DSP farming has been used interchangeably. Cisco IOS dspfarm command is used for both DSP sharing and DSP farming. The DSP farming term was originally used to describe using DSPs as media resources for CallManager. DSP sharing allows C5510 DSPs to terminate a voice call from a voice port that is located in another hardware slot. This can reduce the possibility of oversubscription when using flex complexity. It can also make it easier to add DSPs to an existing gateway. It is physically much easier to add PVDM2s to an NM-HDV2 than it is to add them to the main board of an ISR.

• A local DSP is on the same voice card as the voice port.
• A remote DSP is on a different voice card than the voice port.
• The DSPs on the main board of an ISR are local to the High-Performance WAN Interface Card (HWIC) and Extension Voice Module (EVM) slots and are remote to the NM slots.
• DSP sharing supports only voice termination not transcoding.
• DSP sharing is supported on T1/E1 interfaces only.
• DSP sharing is supported on PVDM2s that are installed on the main board of 2800 and 3800 ISRs.
• DSP sharing is supported on NM-HDV2s that are installed in a 2800, 3700, or 3800 router.
• All voice cards that share DSPs must have synchronized clocks.

You should configure all voice cards that share DSPs for the same complexity.
GW_2811(config)#voice-card 0
GW_2811(config-voicecard)#dspfarm
GW_2811(config-voicecard)#end

Please refer to configuration for IOS Transcoding and Hardware Conferencing.

Transcoding & MTP Resources:

Transcoding can be configured on following devices:

• WS-X6608-T1/E1
• WS-SVC-CMM-ACT
• PVDM installed in NM-HDV
• PVDM2s installed in NM-HDV2
• PVDM2s installed in ISRs
• NM-HD-1V/2V/2VE (C5510)
• 1751/1760

Maximum number of transcoding sessions per device:

Device {Max Sessions}

WS-6608-T1/E1 {24 per port, 192 per module}
WS-SVC-CMM-ACT {64}
C549 {4}
C549 in 1751/1760  {2}
C5510 medium complexity {8}
C5510 high complexity {6}
c5510 flex complexity {16*}

* It is only possible to support 16 transcoding sessions when you are transcoding between two low- complexity codecs. Because this situation is rare, the practical maximum number of transcoding sessions per DSP is 8.

Note: Software-based MTPs can support two voice streams with the same packetization rates. If the voice streams use different packetization rates, a DSP is required. The number of software-based MTP sessions is CPU bound and varies per router platform. You can configure only the C5510 DSP to provide hardware-based MTP services. Each DSP can support 16 MTP sessions. If a call requires MTP services and no MTP is configured, a transcoder is used if available.

Conferencing:

You need to consider only one factor when calculating conference bridge DSP requirements: the number of conferences required.For example, the C5510 supports two mixed-mode conferences with up to eight participants each. Therefore, it is technically accurate to say that the C5510 supports 16 conference participants. But this does not mean we can have 4 conferences of 4 participants each. Number of DSPs required depends on number of Conferences. Particpants per conference are irrelevant.

Device {Max Conference – Max participant}

C549                               {1 – 6}
C5510 (G.711 only)           {8 – 8}
C5510 (G.729a/G.729)     {2 – 8}

E1 Card & PVDM:

How many DSPs/PVDM are required as per E1?

As a rule of thumb always consider One PVDM2-64 for 2 E1s. Each E1 takes up 30 channels (2×30 = 60 > 64). If you are using 1 x E1 then you may use one PVDM2-32.

A PVDM-12 or PVDM2 (32 or higher) can provide voice termination, transcoding, and conferencing simultaneously. The restriction on conferencing is per DSP, not per PVDM. The gateway does track the number of voice ports that are allocated to prevent oversubscription of DSPs. Even though the DSPs are not assigned to a specific voice port, the number of DSPs available for other purposes has been reduced.

You can also use Cisco DSP Calculator to find out DSP resources needed as per requirement.

Useful Commands:

sh voice dsp voice

show voice dsp group all

show dspfarm all

Show dspfarm dsp active

Gateway Outputs:

This is from a gateway which is using on-board PVDM-12 chips.

Show diag#

Slot 2:
High Density Voice Port adapter
Port adapter is analyzed
Port adapter insertion time unknown
EEPROM contents at hardware discovery:
Hardware Revision        : 1.1
Top Assy. Part Number    : 800-03567-01
Board Revision           : E0
Deviation Number         : 0-0
Fab Version              : 02
PCB Serial Number        : JAB04390KNG
RMA Test History         : 00
RMA Number               : 0-0-0-0
RMA History              : 00
Product (FRU) Number     : NM-HDV=
EEPROM format version 4
EEPROM contents (hex):
0x00: 04 FF 40 00 CC 41 01 01 C0 46 03 20 00 0D EF 01
0x10: 42 45 30 80 00 00 00 00 02 02 C1 8B 4A 41 42 30
0x20: 34 33 39 30 4B 4E 47 03 00 81 00 00 00 00 04 00
0x30: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
0x40: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
0x50: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
0x60: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF
0x70: FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF

HDV SIMMs: Product (FRU) Number: PVDM-12
SIMM slot 0: Empty.
SIMM slot 1: Empty.
SIMM slot 2: PVDM-12 SIMM present.
SIMM slot 3: PVDM-12 SIMM present.
SIMM slot 4: PVDM-12 SIMM present.
.

GWY01#sh voice dsp

DSP  DSP             DSPWARE CURR  BOOT                         PAK     TX/RX
TYPE NUM CH CODEC    VERSION STATE STATE   RST AI VOICEPORT TS ABORT  PACK COUNT
==== === == ======== ======= ===== ======= === == ========= == ===== ============
C549 007 01 {medium}  4.1.45 IDLE  idle      0  0 2/0:15    01     0 95382631/933
51746
02 {medium}  4.1.45 IDLE  idle         0 2/0:15    02     0 47552148/467
89172
03 {medium}  4.1.45 IDLE  idle         0 2/0:15    03     0 20910677/206
87231
04 {medium}  4.1.45 IDLE  idle         0 2/0:15    04     0 8394645/8321
251
C549 008 01 {medium}  4.1.45 IDLE  idle      0  0 2/0:15    05     0 3004228/3000
106
02 {medium}  4.1.45 IDLE  idle         0 2/0:15    06     0 983950/97893
8
03 {medium}  4.1.45 IDLE  idle         0 2/0:15    07     0 538659/54259
5
04 {medium}  4.1.45 IDLE  idle         0 2/0:15    08     0 2102367/2139
512
C549 009 01 {medium}  4.1.45 IDLE  idle      0  0 2/0:15    09     0 8154416/8309
524
02 {medium}  4.1.45 IDLE  idle         0 2/0:15    10     0 23548128/239
63817
03 {medium}  4.1.45 IDLE  idle         0 2/0:15    11     0 56429286/574
41003
04 {medium}  4.1.45 IDLE  idle         0 2/0:15    12     0 106057197/10
7984725

This is from another gateway using PVDM2-32 & PVDM2-16:

GW_WCH_01#sh voice dsp group all

DSP groups on slot 0:
dsp 1:
State: UP, firmware: 4.4.24
Max signal/voice channel: 16/16
Max credits: 240
Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 150, reserved credits: 0
Signaling channels allocated: 16
Voice channels allocated: 6
Credits used: 90
Voice channels:
Ch01: voice port: 0/0/0:15.29, codec: g711ulaw, credits allocated: 15
Ch02: voice port: 0/0/0:15.3, codec: g711alaw, credits allocated: 15
Ch03: voice port: 0/0/0:15.1, codec: g711alaw, credits allocated: 15
Ch04: voice port: 0/0/0:15.2, codec: g711alaw, credits allocated: 15
Ch05: voice port: 0/0/0:15.4, codec: g711alaw, credits allocated: 15
Ch06: voice port: 0/0/0:15.31, codec: g711alaw, credits allocated: 15

dsp 2:
State: UP, firmware: 4.4.24
Max signal/voice channel: 16/16
Max credits: 240
Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 225, reserved credits: 0
Signaling channels allocated: 16
Voice channels allocated: 1
Credits used: 15
Voice channels:
Ch01: voice port: 0/0/0:15.5, codec: g711alaw, credits allocated: 15

dsp 5:
State: UP, firmware: 4.4.24
Max signal/voice channel: 16/16
Max credits: 240
Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 240, reserved credits: 0
Signaling channels allocated: 2
Voice channels allocated: 0
Credits used: 0

DSP groups on slot 1:
This command is not applicable to slot 1

DSP groups on slot 2:
This command is not applicable to slot 2

0 DSP resource allocation failure

GW_WCH_01#sh voice dsp

DSP  DSP                DSPWARE CURR  BOOT                         PAK     TX/RX
TYPE NUM CH CODEC       VERSION STATE STATE   RST AI VOICEPORT TS ABORT  PACK COUNT
==== === == ======== ========== ===== ======= === == ========= == ===== ============

—————————-FLEX VOICE CARD 0 ——————————
*DSP VOICE 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 g711alaw     4.4.24 busy  idle      0  0 0/0/0:15  01    0    3128/3041
C5510 001 02 g711alaw     4.4.24 busy  idle      0  0 0/0/0:15  02    0  10125/10293
C5510 001 03 g711alaw     4.4.24 busy  idle      0  0 0/0/0:15  03    0    1432/1215
*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}       4.4.24 alloc idle      0  0 0/1/1     06    0         18/0
C5510 001 02 {flex}       4.4.24 alloc idle      0  0 0/1/0     06    0        442/0
C5510 001 03 {flex}       4.4.24 alloc idle      0  0 0/1/3     02    0         18/0
C5510 001 04 {flex}       4.4.24 alloc idle      0  0 0/1/2     02    0        110/0
————————END OF FLEX VOICE CARD 0 —————————-

GW_WCH_01#sh voice dsp active

DSP  DSP                DSPWARE CURR  BOOT                         PAK     TX/RX
TYPE NUM CH CODEC       VERSION STATE STATE   RST AI VOICEPORT TS ABORT  PACK COUNT
==== === == ======== ========== ===== ======= === == ========= == ===== ============

—————————-FLEX VOICE CARD 0 ——————————
*DSP ACTIVE VOICE CHANNELS*
DSP      DSPWARE           VOX DSP               SIG DSP            PAK   TX/RX
TYPE     VERSION CODEC    NUM CH TS VOICEPORT SLT NUM CH TS RST AI ABRT PACK COUNT
===== ========== ======== === == == ========= === === == == === == ==== ============
C5510 4.4.24 g711alaw 001 01 01 0/0/0:15  000 001 05 01   0  0    0  15825/15801
C5510 4.4.24 g711alaw 001 02 02 0/0/0:15  000 001 06 02   0  0    0  22822/23053
C5510 4.4.24 g711alaw 001 03 03 0/0/0:15  000 001 07 03   0  0    0  14129/14030
C5510 4.4.24 g711alaw 001 04 04 0/0/0:15  000 001 08 04   0  0    0    6865/5661
C5510 4.4.24 g711alaw 001 05 05 0/0/0:15  000 001 09 05   0  0    0    4636/4588
C5510 4.4.24 g711alaw 002 01 06 0/0/0:15  000 001 10 06   0  0    0    3141/3180
————————END OF FLEX VOICE CARD 0 —————————-