IP Phone packet loss

[jsaad]

I'm using G.729 with VAD for my 8 IP phones. I believe that is the lowest packet size for IP phones but we are still having some lost packets during a conversation. We have a T1 with cable modems at the remote locations. Is there a better choice for a IP codec?

 

[DigitelD]

I assume that you are running the IP phones on DSL? If so, QOS cannot be guaranteed.

SHK Certified (School of Hard Knocks)
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[jsaad]

well, not dsl, the phones are connected over a VPN via a cable modem internet service. the bcm is on a full T1. we're using cisco pix 503 and 506 units.

I have all sorts of alarm entries for inter jitter arrival warning etc.

 

[markelbcm]

Like DigitelD made mention of.. QoS is not available end-to-end
when the traffic traverses the internet. Even thou your traffic is encrypted (which by the way, adds more overhead
to the traffic) its zipping across the public internet and
subject to packet loss, latency, no Layer3 QoS.. just a basic
"best effort" to get your packets from A -> B.

Your bang on for the Codes!

I've had many experiences with this problem and have come
to understand and except such issues when sending VoIP over
the Net in a Tunnel (IPsec).



Feature ** RLS: The feature code to fix annoying phone support problems!!

 

[MagnaRGP]

Turn off VAD and change to G.729. VAD icreases processing time and latency.

Also, if your BCM is not near the edge of the network, you can have QoS issues if your LAN is not truly QoS enabled.

I know that this sounds counter-intuitive, but try setting your codec to G.711 for one user and test. It only uses ~175k per call, but adds no latency to processing where G.729 requires heavy processing and can add quite a bit of latency.

Finally, try changing the payload and jitter buffer sizes. I would recommend a smaller payload (especially in G.729)and no more than a medium jitter buffer.