NEC Univerge SV9100 Manual page 324

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The bandwidth required for VoIP calls depends on several factors, including:

Number of simultaneous calls

Data Networking Protocol used

UNIVERGE SV9100 CCIS Network parameters

The more frames encapsulated into each packet, the less bandwidth is required.

This is because each packet transmitted has the same header size. Therefore, if

numerous very small packets are sent then bandwidth is also being used for a

large amount of header information. If we add several frames to the packet, less

packets are transmitted and therefore have less header information sent.

If we add many voice frames to each packet, less bandwidth is being used.

However, this does have disadvantages. If there is a large packet size, and a

particular voice packet is lost, this has a greater impact on the speech quality. If a

small quantity of voice frames per packet is being used, the effect of losing a

packet is reduced.

As a general rule: The more frames per packet, the less bandwidth is used, but

the quality is also lower.

Example 1: CODEC: G.729 Frame Size: 10ms Voice Frames per Packet: 2 Voice

Sample Size: 20ms (frame size x Voice Frames) Bandwidth Required: 24Kbps

Example 2: CODEC: G.729 Frame Size: 80ms Voice Frames per Packet: 8 Voice

Sample Size: 80ms (frame size x Voice Frames) Bandwidth Required: 12Kbps

Network Design Considerations