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
1-8
Cisco WRP500 Administration Guide
Chapter 1 Product Overview and Deployment Guidelines
Special Requirements for Voice Deployments
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.
Note
Some ITSP SIP trunk services limit the maximum number of simultaneous calls. Please check with your
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.
For more information about bandwidth calculation, refer to the following web sites:
www.erlang.com/calculator/lipb/
www.bandcalc.com/
Codec
Approximate bandwidth
budget for each side of
conversation
2 calls
4 calls
6 calls
8 calls
G.711
110 kbps
220 kbps
440 kbps
660 kbps
880 kbps
G.726-4
0
87 kbps
174 kbps
348 kbps
522 kbps
696 kbps
G.726-3
2
79 kbps
158 kbps
316 kbps
474 kbps
632 kbps
G.726-2
4
71 kbps
142 kbps
284 kbps
426 kbps
568 kbps
G.726-1
6
63 kbps
126 kbps
252 kbps
378 kbps
504 kbps
G.729
55 kbps
110 kbps
220 kbps
330 kbps
440 kbps
