[cisco-voip] Voice breaking randomly in some calls

[Ruben Montes (Europe)]

Hello,

 

we're installing a VoIP solution in Algeria. We have VSAT connections
between Algeria and Madrid. We have a CCM 4.1(3)SR4d

cluster (pub+sub) in Algeria connecting with an Intercluster trunk with
a CCM cluster in Madrid: all the calls go through

Madrid. There are two types of calls in Madrid:

 

- On-net: between all the IP phones of the company

- Off-net: all the other calls to external numbers

 

We're using G729 and a Location of 192kbps in the trunk. We are
classifying and marking the traffic entering the VSAT in

our WAN router and the service provider is applying the QoS mechanisms.

 

We are suffering random problems in the quality of the voice: sometimes,
the voice breaks. When this happens, we have 

noticed by pressing "?" twice in the phone, that suddenly we have lost
around 300 received packets. However, the person 

who is talking with you in the other side can hear your voice all the
time. This happens maybe once or twice and then conversation continues.

 

This is ONLY happening with OFF-NET calls, I mean, when talking to an IP
phone in Madrid (ON-NET), we don't have any problem.

When the call is OFF-NET, the call is processed by the voice gateways in
Madrid that connect to a PBX via QSIG, or to

the PSTN via n x PRI E1.

 

As you can see, I haven't given you many technical details or
configurations because there are so many elements involved

that I prefer to give you a high level view of the problem to know your
opinion. We can later digger a little bit in

the details.

 

We have talked with the Satellite service provider, and they say that
they're not losing packets, which I think is true.

 

>From my point of view, there are two options left:

 

1. As we are having only problems in the voice path from Madrid to
Algeria, maybe a QoS misconfiguration in the WAN

router in Madrid affecting only the voice calls originated from the
voice gateways (the calls with the ip phones are working)

properly)?

 

2. Any DSP, IOS, resources problem in the customer voice gateways in
Madrid?

 

Thanks in advance,

 

Ruben

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