I am calculating the amount of bandwith that I have to reserve (QoS) on my WAN in order to support VOIP using the codec G.729 and H323. My WAN is built using Frame-Relay and since my CIR is 512 Kbps I will be using cRTP. Also note that I am using a PBX solution from Ericsson not Cisco, only my network components are from Cisco.
My calculation show me that I will need 12 Kpbs for each voice channel (please correct me if I am wrong). Now my question is how much bandwidth do I have to reserve for call control (signaling)
Here is the calculation you want to use:
20 - G729 byte payload
4 - layer 2 FR overhead
2 - compressed IP/RTP/UDP header
26 bytes * 8 (to get into bits) - 208
20ms sampling rate - 50 packets per second so 50 * 208 = 10400 bits per G729 call. If you're expecting 5 calls over the WAN, give the RTP priority queue 52k
2k, minimum allowed is 8k, so give it 8k for signaling.