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Cisco PVDM2 and PVDM3 DSP Credit/MIPs allocation

 

 

 

 

INTRODUCTION

I have over the years heard of cisco dsps using MIPs/credits but I never quite understood how they work. What I know like many of you is that I can tell how many number of channels a dsp can support based on the PVDM part number.

e.g PVDM2-32 can support 32 channels; PVDM3-64 can support 64 channels and so on. In actual fact these computations depends largely on the dsp complexity mode.

e.g A PVDM2-32 can support 32 channels or 32 G711 calls, using the default flex dsp mode. If the dsp complexity is changed to high, these values are significantly altered.

Example: A PVDM2-32 that supports 32 channels in flex mode, will only support 16 channels in when the dsp complexity is changed to high. Mysteries abound in cisco world! Our job often times is to solve these riddles.

So what is the magic behind all this mathematics? I hope you like maths! We will be doing a lot of it here! I have always wanted to know how these computations work and in here I attempt to share my findings.

You may want to ask why bother knowing these details when we have the cisco dsp calculator. Here are my thoughts on this

  • It’s similar to asking why do you need to know SQL to query/update CUCM database when we already have the CUCM admin page to do that. The answer is obvious; something’s can’t be done from the ccm admin page.
  • From a design point dsp calculator is very effective and should be used, however when things break then this direct knowledge becomes essential
  • As far as I know, the dsp calculator does not take into consideration dsp pooling. Hence you could end up with an over the size resources or “not so cost effective solution” when you could have used existing resources.

 

DSP CREDITS

Before we begin, it’s important to establish this fact. Each PVDM is equipped with a number of DSPs or cores. The higher the number of DSP, the greater the processing power of that PVDM. That obviously is not rocket science. But what is is this: Each dsp/cores within a Cisco PVDM is allocated a fixed amount of what is called “credits”. This is the “biggy!” The power of a DSP depends on the amount of credit that is allocated to it.

PVDM3 and PVDM2 DSP modules use a credit-based system. Each module is assigned a fixed number of "credits" that represent a measure of its capacity to process media streams. Each media operation, such as voice termination, transcoding, and so forth, is assigned a cost in terms of credits. As DSP resources are allocated for a media processing function, its cost value is subtracted from the available credits. A DSP module runs out of capacity when the available credits run out and are no longer sufficient for the requested operation

 

The table below shows the relations between PVDM, DSP and Credits allocated to each dsp

 

PVDM

Number of DSP

Credits/DSP or Credits/Core

PVDM3-16

1

240

PVDM3-32

1

480

PVDM3-64

2

480

PVDM3-128

3

480

PVDM3-192

5

480,645 (read PVDM3-192 section)

PVDM3-256

6

645

PVDM2-8

1/2

120

PVDM2-16

1

240

PVDM2-32

2

240

PVDM2-48

3

240

PVDM2-64

4

240

 

 

 

How to Determine Credits Allocated to A DSP

 

PVDM3-Credits

The obvious question is this, how do we know the allocated Credit to a particular DSP. This is very important as you can see that the allocated credit to each DSP vary depending on what PVDM it is on. The answer is in two folds

1. The popular and most useful command showing dsp related information

 

“Show voice dsp group all”

 

Please refer to this document to understand the output of this command in detail.

 

https://supportforums.cisco.com/docs/DOC-29151

 

LABUK-02S-ERT01#Show voice dsp group all (for a PVDM3-128)

  • DSP groups on slot 0:
    dsp 1:
    State: UP, firmware: 28.3.3
    Max signal/voice channel: 43/43
    Max credits: 645, Voice credits: 645, Video credits: 0
    num_of_sig_chnls_allocated: 30

Transcoding channels allocated: 6

Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 451, reserved credits: 0

Signaling channels allocated: 30
Voice channels allocated: 0
Credits used (rounded-up): 0
Group: FLEX_GROUP_XCODE, complexity: HIGH
Shared credits: 0, reserved credits: 194
Transcoding channels allocated: 0
Credits used (rounded-up): 0
Slot: 0
Device idx: 0
PVDM Slot: 0
Dsp Type: SP2600

dsp 2:
State: UP, firmware: 28.3.3
Max signal/voice channel: 43/43
Max credits: 645, Voice credits: 645, Video credits: 0
num_of_sig_chnls_allocated: 12

Transcoding channels allocated: 14

Group: FLEX_GROUP_VOICE, complexity: FLEX
Shared credits: 193, reserved credits: 0
Signaling channels allocated: 12
Voice channels allocated: 0
Credits used (rounded-up): 0
Group: FLEX_GROUP_XCODE, complexity: HIGH
Shared credits: 0, reserved credits: 452
Transcoding channels allocated: 0
Credits used (rounded-up): 0
Slot: 0
Device idx: 0

dsp 3:

State: UP, firmware: 28.3.3

Max signal/voice channel: 42/43

Max credits: 645, Voice credits: 645, Video credits: 0

num_of_sig_chnls_allocated: 18

Transcoding channels allocated: 0

Group: FLEX_GROUP_VOICE, complexity: FLEX

Shared credits: 276, reserved credits: 0

Signaling channels allocated: 18

Voice channels allocated: 0

Credits used (rounded-up): 0

Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 369

Codec: CONF_G729, maximum participants: 8

Sessions per dsp: 7

Slot: 0

Device idx: 0

PVDM Slot: 0

Dsp Type: SP2600

 

From the output of the above command we can see that each core/dsp in a PVDM3-128 has a fixed credit of 645. This information is obtained from the “Max credits:645” Line

2. The second way is to use another not so popular command on the IOS: “show voice dsp capabilities slot x dsp y”, where x=PVDM slot and y=dsp number on PVDM

#show voice dsp capabilities slot 0 dsp 1 (PVDM3-128)

DSP Type: SP2600 -43

Card 0 DSP id 1 Capabilities:

Credits 645 , G711Credits 15, HC Credits 32, MC Credits 20,

FC Channel 43, HC Channel 20, MC Channel 32,

Conference 8-party credits:

G711 40 , G729 92 , G722 92 , ILBC 129

 

This command showed us the maximum credit for this dsp, which we can see is consistent with the output of the show voice dsp group all command.

 

Let’s look at another example: PVDM3-64

 

LABUK-01S-ERT01#show voice dsp group all

DSP groups on slot 0:

dsp 1:

State: UP, firmware: 26.3.8

Max signal/voice channel: 32/32

Max credits: 480-----------------------We see that 480 credit is allocated to each dsp in a PVDM3-64

num_of_sig_chnls_allocated: 32

Transcoding channels allocated: 10

Group: FLEX_GROUP_VOICE, complexity: FLEX

Shared credits: 41, reserved credits: 0

Signaling channels allocated: 2

Voice channels allocated: 0

Credits used (rounded-up): 0

Group: FLEX_GROUP_XCODE, complexity: HIGH

Shared credits: 0, reserved credits: 343

Transcoding channels allocated: 0

Credits used (rounded-up): 0

Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 96

Codec: CONF_G729, maximum participants: 8

Sessions per dsp: 5

Slot: 0

Device idx: 0

PVDM Slot: 0

Dsp Type: SP2600

dsp 2:

State: UP, firmware: 26.3.8

Max signal/voice channel: 32/32

Max credits: 480

num_of_sig_chnls_allocated: 32

Transcoding channels allocated: 0

Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 480

Codec: CONF_G729, maximum participants: 8

Sessions per dsp: 5

Slot: 0

Device idx: 0

PVDM Slot: 0

Dsp Type: SP2600

 

Now we see that the credit on each dsp varies depending on the PVDM it resides in.

PVDM2-Credits

On the PVDM2s, the credit allocated to each dsp in the PVDMs is 240 except for the PVDM2-8 which has 120 credits.

 

#show voice dsp group all (PVDM2-64, showing only the first dsp)

dsp 1:

State: UP, firmware: 4.4.20

Max signal/voice channel: 16/16

Max credits: 240

Group: FLEX_GROUP_VOICE, complexity: FLEX

Shared credits: 180, reserved credits: 0

Signaling channels allocated: 16

Voice channels allocated: 3

Credits used: 60

Voice channels:

Ch02: voice port: 0/0/0:23.23, codec: g711ulaw, credits allocated: 30

Ch03: voice port: 0/0/0:23.20, codec: g711ulaw, credits allocated: 15

Ch04: voice port: 0/0/0:23.19, codec: g711ulaw, credits allocated: 15

Group: FLEX_GROUP_XCODE, complexity: MEDIUM

Shared credits: 0, reserved credits: 0

Transcoding channels allocated: 0

Credits used: 0

 

THE PVDM3-192

 

The PVDM3-192 has a total of 5 dsps in it. In the table above you can see that the number of credits is 480,645. The reason for this is that this PVDM is built as follows:

 

PVDM3-128 + PVDM3-64.

 

This PVDM is a combination of PVDM3-128 and PVDM3-64, hence since dsp of PVDM3-128 has 645 credits and each dsp of the PVDM3-64 has 480 credits

DSP Channel Calculations/Voice Termination

 

PVDM3

 

Now that we understand and know how many credits each dsp has, we can then go on to attempt to understand how each dsp and corresponding PVDM support a “X” amount of voice channels.

 

The total amount of voice channels a dsp can support is dependent on two factors:

 

1. Maximum Credits

2. DSP complexity mode.

 

To understand more about DSP complexity mode, please refer to this document:

 

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/7x/media.html#wp1045532

 

The amount of credit consumed by a single call or channel depends on the dsp complexity mode and on the dsp itself. The credits used for calls vary from DSP to DSP on the PVDM3. So question is how can we find out?

The powerful command “show voice dsp capabilities” is the answer.

Example1 (DSP1 on a PVDM3-128)

 

LABUK-01-ERT01#sh voice dsp capabilities slot 0 dsp 1

DSP Type: SP2600 -43

Card 0 DSP id 1 Capabilities:

Credits 645 , G711Credits 15, HC Credits 32, MC Credits 20,

FC Channel 43, HC Channel 20, MC Channel 32,

Conference 8-party credits:

G711 40 , G729 92 , G722 92 , ILBC 129

Example2 (DSP1 on a PVDM3-64)

 

LABUK-0115S-ERT01#sh voice dsp capabilities slot 0 dsp 1

DSP Type: SP2600 -32

Card 0 DSP id 1 Capabilities:

Credits 480 , G711Credits 15, HC Credits 34, MC Credits 22

FC Channel 32, HC Channel 14, MC Channel 21,

Conference 8-party credits:

G711 36 , G729 96 , G722 96 , ILBC 120

 

This table shows the credit allocation for PVDM3 dsps

 

PVDM

PVDM3-16

PVDM3-64

PVDM3-128

G711 credits

15

15

15

HC Credits

24

34

32

MC Credits

20

22

20

 

PVDM2

 

NB: MIPS is the same as credits

 

PVDM2-8 Signaling
- 8 calls per DSP for G711 (flex mode only)
- 4 calls for other medium and all high complexity codecs.
- 120 MIPS in FLEX Mode

 

PVDM2-16 - Signaling
- 16 calls for G711 (flex mode only)
- 8 calls for the other medium complexity codecs and g711 in medium complexity mode
- 6 calls per DSP for high complexity codecs
- 240 MIPS in flex mode
- G711 uses 15 MIPS per call (240 MIPS / 15 MIPS per call = 16 calls per DSP)
- The codecs under the High Complexity category use 40 MIPS per call.
- The codecs under the medium complexity category use 30 MIPS per call.
- The D channel doesn't count for resources
- Each FXO or FXS port takes 1 channel

-Each Pri slots also count for 1 channel

 

DSP Channel Allocation Example

So now that we have established these facts let’s look at an example.

 

How many channels does a PVDM3-128 support in flex mode (uses G711 for analysis) and in High complexity mode (HC)

 

Flex mode:

 

Max credit/dsp =645. G711 credit =15, hence 645/15= 43.

So each dsp will support 43 channels/voice calls. However we know that this PVDM has 3 dsps in it, hence if we multiply 43*3=129 channels. So that’s not right because it’s a PVDM3-128. The way this is then done is this.

 

Dsp1=43, dsp2=43, dsp3-42 channels, making a total of 128 channels.

 

This is what we see from the output of the show voice dsp group all command for the dsp3

 

dsp 3:

State: UP, firmware: 28.3.3

Max signal/voice channel: 42/43-------------------------------Max signal=42 out of a possible 43

Max credits: 645, Voice credits: 645, Video credits: 0

num_of_sig_chnls_allocated: 18

Transcoding channels allocated: 0

Group: FLEX_GROUP_VOICE, complexity: FLEX

Shared credits: 276, reserved credits: 0

Signaling channels allocated: 18

Voice channels allocated: 0

Credits used (rounded-up): 0

Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 369

Codec: CONF_G729, maximum participants: 8

Sessions per dsp: 7

Slot: 0

Device idx: 0

PVDM Slot: 0

Dsp Type: SP2600

 

High Complexity Mode: (HC)

Max credit/dsp=645, HC credit=32, hence 645/32=20 (rounded off to the lowest number). Hence with dsp we will have 20*3=60 channels

 

So we see that a PVDM3-128 in HC will only support less than half this capacity if the dsp mode is changed to High.

 

The show voice dsp group all command shows exactly this:

 

#sh voice dsp group all

 

DSP groups on slot 0:

dsp 1:

State: UP, firmware: 28.3.3

Max signal/voice channel: 20/20-------------Channels reduced to 20

Max credits: 645, Voice credits: 645, Video credits: 0

num_of_sig_chnls_allocated: 20

Transcoding channels allocated: 0

Group: FLEX_GROUP_VOICE, complexity: HIGH------With HC mode

Shared credits: 630, reserved credits: 0

Signaling channels allocated: 20

Voice channels allocated: 1

Credits used (rounded-up): 15

Voice channels:

Ch01: voice port: 0/0/0:15.1, codec: g711ulaw, credits allocated: 15

Slot: 0

Device idx: 0

PVDM Slot: 0

Dsp Type: SP2600

 

PVDM2-16

 

Example 2: How many channels does a PVDM2-16 support in both flex and HC mode.

for a PVDM2-16 DSP in Flex mode it will support 16 channels. Following from our calculations:

 

Each dsp=240 credit, G711 credt (flex mode)=15, 240/15=16

 

In HC mode, HC credit (e.g G729 codec)=30 credits, hence 240/30 = 8.

 

Hence we see that the channel capacity is halved.

 

PRI Configuration, Analogue Voice port and DSP allocation

 

One of the most significant aspect of this is that you won’t be able to enable more voice ports that the total number of channels your dsp can support especially when the dsp complexity mode is anything other than flex. This is regardless of the actual codec you use on your voice calls.

 

E.g assuming we have a PVDM3-16 which has 20 credits. If we set our dsp complexity mode to high, we will only have 8 channels. Now if we use G711 on our calls, for 8 calls we will have a total of 8*15=120 credits. So we should have additional 120 credits left. But what you will discover is that you will only be able to configure only 8 pri time slots or 8 analogues voice ports. This is because the dsp capacity is calculated based on its configured dsp complexity mode not on the actual codec used for the call.

E.g

 

DSP groups on slot 0:

dsp 1:

State: UP, firmware: 26.8.1

Max signal/voice channel: 43/43

Max credits: 645

num_of_sig_chnls_allocated: 43

Transcoding channels allocated: 0

Group: FLEX_GROUP_VOICE, complexity: FLEX

Shared credits: 624, reserved credits: 0

Signaling channels allocated: 43

Voice channels allocated: 1

Credits used (rounded-up): 21

Voice channels:

Ch01: voice port: 0/0/1:15.1, codec: g729r8, credits allocated: 20 (in flex mode, g729 uses 20credits)

 

A single g729 call in this codec complexity mode(HC) uses 33 credits

 

DSP groups on slot 0:

dsp 1:

State: UP, firmware: 28.3.3

Max signal/voice channel: 20/20

Max credits: 645, Voice credits: 645, Video credits: 0

num_of_sig_chnls_allocated: 20

Transcoding channels allocated: 0

Group: FLEX_GROUP_VOICE, complexity: HIGH

Shared credits: 612, reserved credits: 0

Signaling channels allocated: 20

Voice channels allocated: 1

Credits used (rounded-up): 33

Voice channels:

Ch01: voice port: 0/0/0:15.1, codec: g729r8, credits allocated: 32

Slot: 0

Device idx: 0

PVDM Slot: 0

Dsp Type: SP2600

 

 

TRANSCODING and CONFERENCING Credit Allocation

 

Now that we understand credit allocation and channel capacity on each dsp, let’s look out how this affects media resources provisioning in a gateway.

 

Each media resource is allocated a fixed credit depending on the dsp that will be used. This is similar to the voice termination we have just covered.

 

To find out the credits assigned to each media resource we use the command

 

“Show voice dsp capabilities”

 

#sh voice dsp capabilities slot 0 dsp 1 (PVDM3-128)

DSP Type: SP2600 -43

Card 0 DSP id 1 Capabilities:

Credits 645 , G711Credits 15, HC Credits 32, MC Credits 20,

FC Channel 43, HC Channel 20, MC Channel 32,

Conference 8-party credits:

G711 40 , G729 92 , G722 92 , ILBC 129

 

#sh voice dsp capabilities slot 0 dsp 1 (PVDM3-32)

DSP Type: SP2600 -32

Card 0 DSP id 1 Capabilities:

Credits 480 , G711Credits 15, HC Credits 34, MC Credits 22,

FC Channel 32, HC Channel 14, MC Channel 21,

Conference 8-party credits:

G711 36 , G729 96 , G722 96 , ILBC 120

 

Conferencing:

 

On a PVDM3-128, each 8 party conference uses 92 (actually about 92.25) credits for a G729 conference and 40 credits for a G711 conference. Hence for a total of 4 G729 conference sessions we will have 92*4 =368 approximated to 369.

 

On dsp3, 18 channels were allocated for voice which totalled 276 credits, leaving only 369 credits. Hence when you try to configure max sessions for your conference you will only have 4 sessions available.

 

Transcoding:

 

The credit used by each transcoding session/channel will depend on the complexity of the transcoder. Transcoding uses the same credits as the complexity mode for voice termination.

 

e.g On a PVDM3-128

HC Credits =32, MC Credits =20

 

In this example from the output of the show voice dsp capabilities, HC credit=32 (actually 32.25)

 

Hence to have a total of 14 transcoding sessions, you will need 14*32.25 credits = approx. 452 credits.

 

PVDM3-64 DSP ALLOCATION EXAMPLE

 

Let’s look at another example of resource allocation on a PVDM3-64 dsp.

 

This example uses the following configurations

 

#sh run | b dspfarm profile

dspfarm profile 1 transcode

codec g711ulaw

codec g711alaw

codec g729ar8

codec g729abr8

codec g729r8

maximum sessions 10

associate application SCCP

!

dspfarm profile 2 conference

codec g711ulaw

codec g711alaw

codec g729ar8

codec g729abr8

codec g729r8

codec g729br8

maximum sessions 6

associate application SCCP

 

voice-port 0/1/0

trunk-group SRSTPSTN 1

supervisory disconnect dualtone mid-call

input gain 1

output attenuation -3

cptone GB

timeouts call-disconnect 5

timeouts wait-release 5

connection plar opx 200

impedance complex2

!

voice-port 0/1/1

trunk-group SRSTPSTN 2

supervisory disconnect dualtone mid-call

input gain 1

output attenuation -3

cptone GB

timeouts call-disconnect 5

timeouts wait-release 5

connection plar opx 200

 

Let’s start by looking at the dsp capabilities on this PVDM

 

#sh voice dsp capabilities slot 0 dsp 1

DSP Type: SP2600 -32

Card 0 DSP id 1 Capabilities:

Credits 480 , G711Credits 15, HC Credits 34, MC Credits 22

FC Channel 32, HC Channel 14, MC Channel 21,

Conference 8-party credits:

G711 36 , G729 96 , G722 96 , ILBC 120-

 

We can see that

  • HC credits=34 (actually 34.33)
  • G729 8-part conference =96
 

Now let’s see how the dsp allocation was done..

 

#sh voice dsp group all (1 dsp used for voice, xcoding and conferencing)

DSP groups on slot 0:

dsp 1:

State: UP, firmware: 26.3.8

Max signal/voice channel: 32/32

Max credits: 480

num_of_sig_chnls_allocated: 32

Transcoding channels allocated: 10------------------------10 xcoding channels at 34.33 credits/channel

Group: FLEX_GROUP_VOICE, complexity: FLEX

Shared credits: 41, reserved credits: 0

Signaling channels allocated: 2---------------------------2 channels for 2 voice ports

Voice channels allocated: 0

Credits used (rounded-up): 0

Group: FLEX_GROUP_XCODE, complexity: HIGH

Shared credits: 0, reserved credits: 343

Transcoding channels allocated: 0

Credits used (rounded-up): 0

Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 96---------------------1 conference session

Codec: CONF_G729, maximum participants: 8

Sessions per dsp: 5

Slot: 0

Device idx: 0

PVDM Slot: 0

Dsp Type: SP2600

 

dsp 2:

State: UP, firmware: 26.3.8

Max signal/voice channel: 32/32

Max credits: 480

num_of_sig_chnls_allocated: 32

Transcoding channels allocated: 0

Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 480

Codec: CONF_G729, maximum participants: 8

Sessions per dsp: 5

Slot: 0

Device idx: 0

PVDM Slot: 0

Dsp Type: SP2600

 

Analysis…

 

We can see the following:

 

Dsp 1:

  • Max credits: 480
  • Signaling channels allocated: 2 (This is for the two voice-ports)
  • Group: FLEX_GROUP_XCODE, complexity: HIGH

Shared credits: 0, reserved credits: 343 (a total of 343 credits were reserved for 10 transcoding sessions. This figure is calculated as 34.33*10 rounded up to 343

 

  • Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 96 (A total of 96 credits was reserved for 1 G729 conference)

 

Now observe that the remaining 5 conference sessions will be allocated to dsp 2.

 

DSP2:

  • Max credits: 480
  • Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 480

 

Each G729 conference takes 96 credits, 480/96=5. Hence we have the total of 6 conference sessions provisioned as configured.

 

Difference between PVDM2 and PVDM3

 

The example above shows one the major difference between PVDM2 and PVDM3. In a PVDM2, dsp conferencing can’t not be shared with any other dsp. When a dsp is allocated for conferencing, it is dedicated; this is because a special firmware is loaded unto the dsp.

 

Example

 

dsp 1:

State: UP, firmware: 4.4.20

Max signal/voice channel: 16/16

Max credits: 240

Group: FLEX_GROUP_VOICE, complexity: FLEX

Shared credits: 210, reserved credits: 0

Signaling channels allocated: 0

Voice channels allocated: 1

Credits used: 30

Voice channels:

Ch01: voice port: 0/0/0:23.1, codec: g711ulaw, credits allocated: 30

 

dsp 2:

State: UP, firmware: 1.0.6

Max signal/voice channel: 16/16

Max credits: 240

Group: FLEX_GROUP_CONF, complexity: CONFERENCE

Shared credits: 0, reserved credits: 240

Conference session: 2

Credits used: 0

 

We can see that the dsp2 above was dedicated for conferencing and the firmware on it is different to the other dsp. Even though there are just 2 conference sessions, the whole of 240 credits were reserved.

 

 

 

DSP Hunting Order

 

Cisco IOS searches for dsp to allocate for either voice termination, transcoding and conference in a particular order. To know the hunt order you can use the following command

 

“show voice dsp sorted-list slot x” where x is the slot number

 

#sh voice dsp sorted-list slot 0

DSP id selection list for different service for Card 0:

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

Note: analog voice ports allocate DSPs with least credits

to most credits during boot up for this voice card

Voice :01,02,03

Conf 0 :03,02,01

Xcode :01,02,03

 

From the Above, dsp1,2 and 3 will be used for voice termination, dsp3,2,1 will be used for Conferencing. This is the reason why you see that even though the second and first dsps have credits available on them, conferencing is allocated to the 3rd DSP. Then when the credits on that dsp is not enough for the conference sessions, dsp2 will be used and so on.

 

DSP Numbering:

 

Sometimes when we have a combination of dsps, we do see often times some funny numbering and we don’t quite understand how these came about.

 

PVDM3 Only

 

On a PVDM3 only installation, each PVDM slot is numbered for the maximum amount of dsp that it can accommodate, even if there are fewer dsps installed.

 

Example Let’s look at this combination

 

 

Slot0: PVDM3-256

Slot1:PVDM3-16

Slot1:PVDM3-64

 

This is how the dsp will be numbered..

 

Slot0:

Dsp1,2,3,4,5,6

 

Slot1:

dsp7

 

Slot2:

dsp13,14

 

The reason behind this is this…slot 1 can take a maximum of 6 dsps but only 1 dsp has been installed, so the numbering for the other 5 is kept intact. Hence cisco IOS count 7,8,9,10,11,12 and then IOS goes to the next number which is 13.

 

PVDM2 only

 

On a PVDM2, the maximum dsp you have is 4. So each dsp is numbered to account for this even if the number of dsp is less.

 

Lets look at this combination

 

Slot0: PVDM2-32

Slot1:PVDM2-64

Slot2:PVDM2-16

 

This is how the dsp will be numbered

 

Slot0:

Dsp1,2,

 

Slot1:

dsp5,6,7,8

 

Slot3:

Dsp 9

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Last update:
‎08-28-2017 10:28 PM
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Comments
Cisco Employee

Deji, my friend, awesome doc! +5! Thanks for taking the time and effort to come up with this for the community!!

Great DOC!!!!

VIP Super Bronze

Thanks Harmit. I just thought this was one area where the documentation was a bit scarce.

VIP Super Bronze

Thanks leonardo

New Member

Excellent doc!

New Member

Great doc, very useful!!!!!!!!!

New Member

Yes I agree a very good document. I had run out of DSP resources and HW conferencing had shutdown or could not support enough sessions. This was a very useful document and helped my understanding as to what may have happened. Thank you...I have it fixed now.

Cisco Employee

Very good doc, everything is well explained.

Looking at the table wth credits, is it true that if i use 2 different PVDM3-16 (one for each slot) i have more sessions available than using one PVDM3-32, if i am using hig complex code?

Thanks

V

VIP Super Bronze

V,

No you wouldnt have more sessions, they will essentially be the same. each PVDM3-16 has 240 credits, with 2 of them you will have a total of 480 credits. Each PVDM3-32 has 480 credits. So you will end up with the same number of sessions

Cisco Employee

I am not sure about that, since looking at the DSP calculator, a PVDM3-32 can handle max 14 high complex codec calls, that probably is the result of credits/credits allocation per DSP that means 480/34 (34 is the value for PVDM3-64) that is 14 calls.

While using 2 PVDM3-16 the total is 240/24 + 240/24 = 20 calls


VIP Super Bronze

V,

You are infact correct. I totally ignored the fact that the credit allocation/dsp for each HC calls is different for these two. So Yes with two PVDM3-16 you will get a total of 20 calls and with a single PVDM3-32 you will get 14 calls. But that woundlt be a  best practice/design approach because you will be loosing slots and therefore cound impact on scalability should you need more PVDMs.

Cisco Employee

Yes totally agree with you.

In fact the DSP calculator is built to answer with a focus on the Slot Optimization, and the result is that if i ask for 15 HC calls it reports PVDM3-64.

Anyway in my case i have platform pre-ordered and stocked with PVDM3-16 on board, so i need to undertand how to add sessions in the best way.

Thanks

V

VIP Super Bronze

V,

You are correct. DSP calculator optimises slot/PVDM allocation..which makes sense. Cases like yours is is why I wrote the document. It helps you in ways the dsp calculator cant. I am glad you dound it useful. Dont forget to rate it though! Give as much as it has helped you

Cisco Employee

Awesome doc.....

New Member

Good Stuff man!

New Member

According to the examples and the output from the PVDM3-128 DSP capabilities, shouldn't the first table display that PVDM3-128 capacity per DSP is 645 credits instead of 480 ?

Regards

VIP Super Bronze

You are correct, that m ust have been a typo..Thanks for bringing it to my attention..

Ayodeji,

As always, Excellent Document. !

New Member

Thank you very much for your help. It's very very useful to me!

 

One question: could it be completed including video capabilities?

 

New Member

HI Ayodeji

 

Could you please make me understand the following thing ?

 

Shared credits: 270, reserved credits: 0

 

Credits used (rounded-up): 60

 

Does it mean I still can use 210 credits ?

 

PVDM Details 

 

NAME: "PVDM3 DSP DIMM with 64 Channels on Slot 0 SubSlot 4", DESCR: "PVDM3 DSP DIMM with 64 Channels"
PID: PVDM3-64 

 

 

The configuration is like this :

 

dsp 1:
  State: UP, firmware: 32.1.4
  Max signal/voice channel: 32/32
  Max credits: 480, Voice credits: 330, Video credits: 150
  num_of_sig_chnls_allocated: 22
  Transcoding channels allocated: 0
  Group: FLEX_GROUP_VOICE, complexity: FLEX
    Shared credits: 270, reserved credits: 0
    Signaling channels allocated: 22
    Voice channels allocated: 4
    Credits used (rounded-up): 60
    Voice channels:
      Ch02: voice port: 0/0/0:15.31, codec: g711ulaw, credits allocated: 15
      Ch03: voice port: 0/0/0:15.23, codec: g711ulaw, credits allocated: 15
      Ch04: voice port: 0/0/0:15.9, codec: g711ulaw, credits allocated: 15
      Ch05: voice port: 0/0/0:15.24, codec: g711ulaw, credits allocated: 15
  Slot: 0
  Device idx: 0
  PVDM Slot: 0
  Dsp Type: SP2600

 

 

 

 

Regards

 

Rohit

New Member

Ayodeji,

Thanks for the great KT. I am not an expert in this field. My question is regarding the MIPS/credits use , have a confusion[might be a big blunder] that will those credits would be used by PRI calls where no transcoder invoked?

VIP Super Bronze

Hi Manzoor

If the credits have already been allocated for transcoding sessions, then it will be reserved for that purpose and cant be used for voice calls even if there are no transcoding sessions taking place.

Don't forget to rate the document!!

New Member

Hi,

 

Very good document.  Is there something that matches table 3 in this document for PVDM3 modules?

 

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/cminterop/configuration/15-mt/dia-15-mt-book/vc-enh-confr-vgr.html#GUID-5AD10E4B-0499-4DC5-B513-2B0EF35E002D