One way speech during VOIP call

Unanswered Question


We have an Avaya IP PBX connected to a 3825 by 4x E1's at Site A. This is connected to an 2MB MPLS wich in turn is connected to another 3825 and a TDM PBX via 4xE1's at site B.

All calls flow from site B to site A. During a conversation from site B the users will start to have one way speech during the call and will eventually hang up. The speech is heard flowing from site B to site A. The users at site B no longer hear the users at site A.

the proble effect approximatly 20% of all calls transversing any of the E1's

Call flow below. Codec is G729 over the MPLS. We have 4x PVDM2-64's in each router.

AvayaIPPhones--- AvayaIPPBX---4xE1--3825----MPLS----3825--4xE1--PBX


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Yes, it is not a routeing problem as all phones take the same route and some will have a one way issue during the call and other will not.

There is no clocking issues on the show controllers E1.

This has just recently started with no configuration changes. The one router is running an old 12.4.3 SPServices. I might try and change that.

Adam Frankel Mon, 11/12/2007 - 17:23
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You mention site A and site B in your problem description, but I do not see it in the call flow diagram.

Is this problem predictably reproducible among the same phones. Or if you get one way audio, can you hang up and call again and have it work?

(SITE A) AvayaIPPhones--- AvayaIPPBX---4xE1--3825----MPLS----3825--4xE1--PBX (SITE B)


Also if i run a show voice dsp i see the TX and RX packets counting. However they are sometimes not very equal, but i suppose this is the norm.

There are around 60 to 90 concurrent calls over this link and with a 15% problem ratio it is very hard to replicate the problem in a controlled state.

When the problem happen the exact same user will call again and it will be fine.


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