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G.723 bandwidth calculations

Hi,

I have a problem to understand a calculations for G.723 bandwidth.

According to following link to Cisco doc. there are 6.3Kbps codec bit rate ,24 Byte payload size and 18,4 Kbps Bandwith at full rate on Serial link.

http://www.cisco.com/warp/public/788/pkt-voice-general/bwidth_consume.html

1.So, The packet per Sec rate is:

6300bit/(24*8)=32,8 Pac/Sec

According to ITU standard the packet rate is 30 Msec. I tested it with analyzer, and router send it every 30 msec. But 1sec/32,8 Pps is 30,48 Msec

So, what is a write Packet rate and bandwith consumption for G.723?

1 REPLY
New Member

Re: G.723 bandwidth calculations

Hi,

the calculation of bandwidth goes like this:

Cisco says Payload size : 24 bytes, Bandwidth utilization (includes payload RTP/UDP/IP + MLPPP headers) : 18.4 kbps, RTP/UDP/IP headers : 40 bytes, MLPPP header : 6 bytes, 1 packet is sent every 30 msec. So using all these informations, it leads to this calculation.

Payload bandwidth : 24bytes * 8 bits * 33,33 packets per sec = 6.4 Kb/s

Headers Bandwidth : (40bytes + 6 bytes) * 8 bits * 33,33 packets per sec = 12.26 Kb/s

Total bandwidth = 12.26 Kb/s + 6.4 Kb/s = 18.6 Kb/s

This result is pretty close to what Cisco is telling in his chart (18.4 Kb/s) and value was rounded.

So the packet rate is trully 1 packet each 30 msec but let keep in mind that this parameter is ajustable in the Call Manager.

Hope this help!

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