VoIP Jitters & Phantom Calls

genXrcist · January 2011

hello!

I've not even begun my CVOICE training so I'm really a newbie when it comes to VoIP. Would someone please tell me what the major causes of jitter and phantom/echo calls on a Cisco Unified Communications system?

I have a customer with 100% Cisco gear running UC and they are having these types of issues sporadically. The customer is fed up with their current network provider's inability to resolve this issue so we're looking to refer a partner company of ours to do business with them but before we do that I wanted to be able to speak more intelligently about the problems.

I can read websites and manuals as well as anyone else but I thought I would pose this question in general to see if there was a consensus on the most likely causes for these types of problems.

Thanks!!

chmorin · January 2011

Generally jitter is caused by a delay in the voice traffic, and the packets being received with to many gaps between or other similar issues. The resolution is usually a QoS implementations at bottle necks.

Echo calls could possibly be a issue with their echo-canceling resources found in the gateway... i think. I'm pulling that out of my head from a paragraph I read somewhere (I assume) since I have not experienced an echo problem before.

I'm going to have to ask for a more elaborate description on what 'phantom calls' refer to.

If I had to pull a resolution out of my butt right now I'd say analyze the gateway's resources and make sure it has allocated enough spots for data over the WAN to be sent, enough PRI resources, and enough DSP resources.

Daniel333 · January 2011

Keep your ping times below 150ms from phone to callmanager. Also if you have ping times that jump around a lot you'll get messed up calls.

That is 50ms then 90ms, then 120ms, then 50ms would be worse than just having 120ms times.

chmorin · January 2011

Daniel333 wrote: »

Keep your ping times below 150ms from phone to callmanager. Also if you have ping times that jump around a lot you'll get messed up calls.

That is 50ms then 90ms, then 120ms, then 50ms would be worse than just having 120ms times.

This is also true. While the 150ms rule only applies one-way, you would rather have a consistent stream of audio than a constantly changing one.

genXrcist · January 2011

chmorin wrote: »

Generally jitter is caused by a delay in the voice traffic, and the packets being received with to many gaps between or other similar issues. The resolution is usually a QoS implementations at bottle necks.

Echo calls could possibly be a issue with their echo-canceling resources found in the gateway... i think. I'm pulling that out of my head from a paragraph I read somewhere (I assume) since I have not experienced an echo problem before.

I'm going to have to ask for a more elaborate description on what 'phantom calls' refer to.

If I had to pull a resolution out of my butt right now I'd say analyze the gateway's resources and make sure it has allocated enough spots for data over the WAN to be sent, enough PRI resources, and enough DSP resources.

Thank you for the quick responses! I'm still trying to wrap my mind around QoS so I will read up more about that.

As for phantom calls by that I mean a phone call will ring into a phone and when they pick it up, there's no one there. Happens to frequently to be considered prank calls.

Thanks for the tip on ping times, I will ask about that!

VoIP Jitters & Phantom Calls

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