VoIP Quick Facts

10 Jun

  1. Voice header is normally 40 bytes, which consists of IP + UDP + RTP (20+8+12). Bandwidth requires to send 40-byte packets at 50 packets per second is 16kbps
  2. RTP hear can be compressed from 40 bytes to 2 or 4 bytes, it is called cRTP
  3. G729a payload is 8kbps, The header (IP+UDP+RTP) takes 16kbps, the total bandwidth for a G729a call is 24kbps
  4. Each voice payload consists of 20ms of voice payload on Cisco IOS devices, which means 50 packets per second.
POPULAR VOICE CODECS AND PAYLOAD BANDWIDTH REQUIREMENTS
Codec Bit Rate for Payload (no header) (in kbps) Size of payload (20-ms Default in Cisco IOS Software)
G.711 Pulse Code Modulation (PCM) 64 160 bytes
G.726 ADPCM 32 80 bytes
G.729 8 20 bytes
G.723.1 ACELP 5.3 20 bytes

 

UPDATED BANDWIDTH REQUIREMENTS FOR VARIOUS TYPES OF VOICE CALLS
Bandwidth Consumption, Including L2 Overhead Layer 3 Bandwidth Consumption
802.1Q Ethernet (32 Bytes of L2 Overhead) PPP (9 Bytes of L2 Overhead) MLP (13 Bytes of L2 Overhead) Frame-Relay (8 Bytes of L2 Overhead) ATM (Variable Bytes of L2 Overhead, Depending on Cell-Padding Requirements)
G.711 at 50 pps 80 kbps 93 kbps 84 kbps 86 kbps 84 kbps 106 kbps
G.711 at 33 pps 75 kbps 83 kbps 77 kbps 78 kbps 77 kbps 84 kbps
G.729A at 50 pps 24 kbps 37 kbps 28 kbps 30 kbps 28 kbps 43 kbps
G.729A at 33 pps 19 kbps 27 kbps 21 kbps 22 kbps 21 kbps

 

ONE-WAY DELAY BUDGET GUIDELINES
1-Way Delay (in ms) Description
0–150 ITU G.114’s recommended acceptable range
0–200 Cisco’s recommended acceptable range
150–400 ITU G.114’s recommended range for degraded service
400+ ITU G.114’s range of unacceptable delay in all cases

Source: http://ccdewiki.wordpress.com/2013/06/10/voip-quick-facts/

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