Cisco IP SLA: c5510 or c549 DSP

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Nicholas Matthews Wed, 12/24/2008 - 07:10
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The PVDM is a DSP. The DSP turns RTP packets into analog audio. It is the part of the router that is responsible for creating voice packets.

You can do a 'show diag | i FRU' to see if you have any DSPs. NM-HDVs will have c549s, and other modules have the PVDM2-X.

You will only need PVDMs for the voice SLA, you should be able to do UDP echoes, pings, and the likes without DSPs.



emorgan Wed, 01/21/2009 - 10:25
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Hi, I have just configured a voip-rtp SLA on a 2821 with 12.4(20)T. I have FXO and PRI ports for testing purposes.

If i use say source-port 0/2/0, it assigns a 5510 DSP channel to this test.

What happens if a call comes in that FXO port while the test is being performed? Do I need to dedicate a port for SLA?

What about if I have a PRI instead. Do I need to reserve something like the last PRI channel for SLA so there are no conflicts with incoming/outgoing calls? (like source-port 0/3/0:22)

Last question... unlike udp-jitter, the CLI will not accept DSCP tags ("tos 184" for dscp EF). What is the default dscp and can it be changed?

My preliminary config:

ip sla 3099

voip rtp x.x.x.x source-voice-port 0/2/3 codec g729a duration 20 advantage-factor 0

frequency 180

history hours-of-statistics-kept 4

ip sla schedule 3099 life forever start-time now



emorgan Wed, 01/21/2009 - 10:35
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Correction, I am running 12.4(15)T4. Will test again on 12.4(20)T soon.

Nicholas Matthews Wed, 01/21/2009 - 11:20
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I'm not familiar with the functionality using the voice-port rather than IP address.

However, both of these issues (DSP allocation/DSCP marking) do not exist if you use a source IP address instead of voice port.

The command reference isn't particularly helpful either. I would start by using the IP source, and use the voice port if there is something about the function of the IP address that doesn't suit your requirements.




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