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Reply To: Voice Packet Size

#33201
Alex Yuen
Guest

Calculation of Bandwidth in VoIP

No. of Frames 1 2 3 4 5 6 7 8 9 10 11 12 13
No. of bytes for RTP 12 12 12 12 12 12 12 12 12 12 12 12 12
No. of bytes for VDP 8 8 8 8 8 8 8 8 8 8 8 8 8
No. of bytes for IP 20 20 20 20 20 20 20 20 20 20 20 20 20
No. of bytes for ETHERNET 14 14 14 14 14 14 14 14 14 14 14 14 14
No. of bytes for voice 10 20 30 40 50 60 70 80 90 100 110 120 130
Packet Size (bytes) 64 74 84 94 104 114 124 134 144 154 164 174 184
Sampling at (ms) 10 20 30 40 50 60 70 80 90 100 110 120 130
Bytes in seconds 6,400 3,700 2,800 2,350 2,080 1,900 1,771 1,675 1,600 1,540 1,491 1,450 1,415
Link Speed (kbps) 51.20 29.60 22.40 18.80 16.64 15.20 14.17 13.40 12.80 12.32 11.93 11.60 11.32
Required Bandwidth for 1 DSP (M) 2.458 1.421 1.075 0.902 0.799 0.730 0.680 0.643 0.614 0.591 0.573 0.557 0.544

The link speed changes from 18.8 kbps to 14.17 kbps for 4 to 7 frames, the link speed only drops in the range of 1 to 2 kbps. The required bandwidth for 4 to 7 frames will between 0.68M to 0.90M

The voice quality, with coding quality and latency control at the gateway, as well as latency and jitter control in the network will depends of no. of frames in the packet. ITU-T G.114 recommendation for end-to delay in a voice network should be 150ms.

To ensure end-to-end QoS for voice traffic while making optimal use of network bandwidth, Manufacturer should offer a comprehensive set of QoS capabilities, will Lucent provides a set of software in this aspects.