HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual page 346

Setting Up Quality of Service
Configuring LLQ
Standard Packets per Second Voice Payload Size
G.711 50
G.722 50
G.723.1 33.3
G.728 100
G.729 50
7-34
Table 7-9. Example Bandwidth Calculations for VoIP
• 140 bytes
• 160 bytes
• 120 bytes
• 140 bytes
• 160 bytes
• 20 bytes
• 24 bytes
20 bytes
20 bytes
The necessary bandwidth depends on:
The size of the packet headers—Packet headers are 47 bytes for MLPPP
and MLFR connections as well as Frame Relay connections that use
fragmentation:
• 20 for the IP header
• 8 for the UDP header
• 12 for the RTP header
• 6 for the MLPPP or MLFR header
• 1 for the MLPPP or MLFR end-of-frame flag
If you use the MLPPP long sequence number format, the MLPPP header
is 8- bytes and the total size for packet headers is 49 bytes. For PPP
connections, the packet headers are 45 bytes.
Real-time Transport Protocol (RTP) compression (cRTP) reduces the IP
header from 40 bytes to 2 bytes (or 4 bytes with checksums), which
decreases necessary bandwidth.
The size of the voice payload—Each packet must have a set number of
bytes in its header no matter how large or how small its payload. As the
size of the voice payload increases, the proportion of bytes consumed in
overhead decreases and so does the necessary bandwidth. Combining
several samples in the same packet increases the size of the voice payload.
However, the decrease in required bandwidth comes at the price of higher
latency.
Total Size with MLPPP
or Frame Relay header
• 187 bytes
• 207 bytes
• 167 bytes
• 187 bytes
• 207 bytes
• 67 bytes
• 71 bytes
67 bytes
67 bytes
Per-Call Bandwidth
• 74.8 Kbps
• 82.8 Kbps
• 66.8 Kbps
• 74.8 Kbps
• 82.8 Kbps
• 17.8 Kbps
• 18.9 Kbps
• 53.6 Kbps
• 26.8 Kbps