G.729 voip bandwidth calculation in QoS

Unanswered Question
Jun 19th, 2008

I am trying to calculate how much bandwidth should put in the priority queue in the Frame Relay WAN for 8xG.729 calls.

I understand that the bandwidth for each call is (payload size+L2 overhead)*packets/s. For the G.729, by default it has 20 bytes payload and 50 packets per second.

But I am confused about the overhead.

In the QoS SRND3.3 page 1-15, it says MLP overhead is 13bytes, and FRF.12 has 8 bytes.

But from http://www.cisco.com/warp/public/788/pkt-voice-general/bwidth_consume.htm,

it says both MLPPP and FRF.12 have 6 bytes of overhead. In voice bandwidth calculator, it also says 6 bytes overhead for both MLPPP and RF.12.

So which one I should trust, the SRND or cisco web site?

Also for cRTP, all documents says the overhead is 2 bytes or 4 bytes. Then should I use 2 or 4?

Thanks!

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Chris Deren Thu, 06/19/2008 - 17:41

These values will not make a dramatic difference, simply use ~27 kbps per G729 call over Frame Relay, and multiply it by the number of calls you want to allow between the sites (I would suggest ensuring it by implementing CAC).


HTH,


Chris

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