NEC SL1100, Networking Manual

Page: 176 / 292

Issue 6.0 NEC SL1100
9 - 42 IP Multiline Station (SIP)

(.020 * 64000) /8 = 160 Bytes

Example of G.729 with a 30ms packet size

(.030 * 8000) /8 = 30 Bytes
Now that you have the voice payload in bytes you can calculate the overall
bandwidth including the layer 2 media. Below are some of the common layer
2 media types and their overhead.

Ethernet = 18 Bytes

802.1Q/P Ethernet = up to 32 bytes

PPP = 9 Bytes

Frame Relay = 6 Bytes

Multilink Protocol = 6 Bytes
Bandwidth Calculation
( [ Layer 2 ov IP/UDP/RTP Voice Payload ] /
Voice Payload ) * Default CODEC speed = Total Bandwidth
Example of a G.711 call over Ethernet using a 20ms packet size and not
using RTP header compression
(.020 * 64000) / 8 = 160 Bytes for Voice Payload
([ 18 + 40 + 160] / 160) * 64000 = 87200bps
If VAD is not enabled each side of the conversation would be streaming
87.2kbps in one direction for a total of 174.4kbps.