Check IP SLA udp jitter(codec) support!!!

Unanswered Question
Sep 13th, 2007

Hi all,

To calculate MOS we need to configure IP UDP jitter with some codec. What oid should be checked to know that device supports this operation?

Please help me!

Thanks ahead

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Joe Clarke Thu, 09/13/2007 - 08:56

Have a look at the rttMonApplSupportedRttTypesTable from the CISCO-RTTMON-MIB. Thu, 09/13/2007 - 09:15

You will need a bit of info as to the codec as to which DSCP value its suppose to use . For example G729 is expecting Class EF (or 45 if you like numerical values)

Here's a quick example of a collector hardcoded in IOS (you can use IPM to quickly deploy collectors acros lots of devices in a few minutes)

ip sla logging traps

ip sla 10

udp-jitter codec g729a


ip sla schedule 10 life forever start-time now ageout recurring

masur_fox_spr Fri, 09/14/2007 - 02:40

Thanks a lot.

But I need to check udp jitter support without creating this operation using SNMP. As I understand I need check some oid.

Please give some info about that.

Thanks ahead Fri, 09/14/2007 - 04:28

What you need to check on is the image's support for IPSLA. In the image documentation the reference you see the ability to configure "rtr". IOS by itsself out of the box does nothing until you configure it to do so. You have to configure a collector to generate the statistics that you will use to create a MOS score if you want to use the router as the data source.

If you dont want to use the router as a data source to calculate the MOS scores you're asking the wrong question. I monitor VoIP 3 different ways: internally using IPM, internally using statically configured collectors, and Concord to manage the data collection and externally using Concord and VQM.

That last part of my original reply WAS straight command line for IPSLA collector definition.

But what do I know, I only have some 15,000 VoIP call center reps. Your mileage may vary.

masur_fox_spr Fri, 09/14/2007 - 04:50

I am implementing some application that allows to monitor Voip QOS using jitter(codec) operation. To add router capable of running IP SLA I need to ensure that it supports jitter(codec) operation.

As I know jitter(codec) operation is extended jitter operation. That's why checking rttMonApplSupportedRttTypesTable isn't correct in my case. I need to ensure that device can run jitter(codec) to add it my infrastructure. How can i check it? Fri, 09/14/2007 - 05:07

You don't normally "run" a codec on your router or switch unless its a voice gateway and then its done it hardware. A codec is an abbreviation for Coder-Decoder. It's an analog-to-digital (A/D) and digital-to-analog (D/A) conversion process that creates packets that need to arrive in order on both sides of the connection with minimal delay and loss.

If its a voice gateway then its not IOS version that you'd be concerened with , but rater hardware because the encode/decode is done in hardware via DSPs (Digital Signal Processors) Cisco supports most of them including G.711, G.729, G.729a, and G.723.1.

Codec selection is a compression ratio choice and it should be based on "how good does it need to be". Local LAN to local LAN you can use minimal compression.

Joe Clarke Fri, 09/14/2007 - 05:41

If you poll the object I mentioned in my reply, you will see the list of operations the device supports. You do not need to create a collector for that.

masur_fox_spr Mon, 09/17/2007 - 05:01

Jitter(codec) extends jitter operation. I have checked jitter type from rttMonApplSupportedRttTypesTable but it does not help to know that devise support Jitter(codec) operation.

Do you have any ideas about that?

Joe Clarke Mon, 09/17/2007 - 08:05

If the IP SLA agent supports jitter and icmpJitter, it supports setting the jitter codec. If it only supports jitterAppl, then it does not.

Joe Clarke Mon, 09/17/2007 - 08:26

pathJitter is another operation that is supported on devices that support setting the codec for jitter operations.

masur_fox_spr Mon, 09/17/2007 - 08:30

So that means i can check jitter and pathJitter or jitter and icmpjitter presence to verify if this device supports jitter(codec) operation?

masur_fox_spr Tue, 09/18/2007 - 02:31


I cannot find id pathjitter(like voip(13),jitter(9))in RttMonRttType. What is id of pathjitter?

Please help me!

Thanks ahead

Joe Clarke Tue, 09/18/2007 - 08:10

Looks like the type currently only shows up on the CLI. The MIB mentions pathJitter, but has not defined an RttMonRttType for it yet.


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