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Community Member

Seeing RX on the phone change from 20 to 10ms

Hi, I just put in a 3845 MGCP gateway. For calls that connect to this gateway that use G729, I notice that when I look at call stats on the phone, the whenever the PSTN side stops talking, the RX size goes from 20ms to 10ms. It almost sounds like VAD kicking in, but my gateway has NO MGCP VAD defined on it. G711u calls are fine.

The Call Mgrs are 4.1.3 sr2 and the Gateway is 12.4.5a.

Thanks.

2 REPLIES
Cisco Employee

Re: Seeing RX on the phone change from 20 to 10ms

Hello,

Is this behavior giving problems with call quality?

Can you please put in the following configs:

no mgcp vad

mgcp codec g729r8 packet 20

See if that helps.

Thanks!

Also, attach a

debug mgcp packet

show run

show ver

for a G729 call.

Community Member

Re: Seeing RX on the phone change from 20 to 10ms

Had a similar problem through a IPIPGW. It turned out that the culprit was g729b. Because the phones supported 729b (which has VAD on) that it was negotiating this. There is a service parameter to turn off 729b support in CCM. Once this was done the problem of changing RX size went away. This may not be the same problem for you but its worth a try..

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