Cisco WRP500 Administration Manual page 14

Special Requirements for Voice Deployments
R E V I E W D R A F T # 1 — C I S C O C O N F I D E N T I A L
example, in the case of a 2 Mbps uplink broadband connection, assume 1 Mbps. Limit the
uplink bandwidth in the Integrated Access Device to this value. This setting helps to maintain
the utilization levels below 60%, thus reducing jitter and packet loss.
• Use an additional broadband connection for voice services only. A separate connection is
required when the broadband connection services do not offer quality of service and when it is
not possible to apply the above mentioned utilization mechanism.
The available connection bandwidth determines the maximum number of simultaneous calls that the
system can support with the appropriate audio quality. Use this information to determine the maximum
number of simultaneous VoIP connections that the system can support.
For asymmetric connections, such as ADSL, the maximum number of calls is determined by the
upstream bandwidth. In general it is a good practice to use no more than 75% of the total available
bandwidth for calls. This provides space for data traffic and helps ensure good voice quality.
Some ITSP SIP trunk services limit the maximum number of simultaneous calls. Please check with your
Note
Service Provider to understand the maximum number of simultaneous calls each SIP trunk supports.
The following table provides the approximate bandwidth budget for different codecs.
Note The Cisco WRP500 supports only the G.711 and G.729 codecs.
Codec
G.711
G.726-4
0
G.726-3
2
G.726-2
4
G.726-1
6
G.729
For more information about bandwidth calculation, refer to the following web sites:
www.erlang.com/calculator/lipb/
www.bandcalc.com/
Cisco WRP500 Administration Guide
1-8
Approximate bandwidth
budget for each side of
conversation
110 kbps
87 kbps
79 kbps
71 kbps
63 kbps
55 kbps
Chapter 1 Product Overview and Deployment Guidelines
2 calls 4 calls 6 calls
220 kbps 440 kbps 660 kbps
174 kbps 348 kbps 522 kbps
158 kbps 316 kbps 474 kbps
142 kbps 284 kbps 426 kbps
126 kbps 252 kbps 378 kbps
110 kbps 220 kbps 330 kbps
8 calls
880 kbps
696 kbps
632 kbps
568 kbps
504 kbps
440 kbps