Product Overview and Deployment Guidelines
Special Requirements for Voice Deployments
Cisco Small Business WRP400 Administration Guide
12
1
•
Internet Telephony Service Provider (ITSP) for Voice Over IP telephone service,
supporting a “bring your own device” model
•
A computer with Microsoft Windows XP or Windows Vista for system
configuration
Special Requirements for Voice Deployments
Voice deployments have special requirements that you must meet to ensure voice
quality.
•
“Bandwidth for Voice Deployments,” on page 12
•
“NAT Mapping for Voice over IP Deployments,” on page 14
•
“Local Area Network Design for Voice Deployments,” on page 14
Bandwidth for Voice Deployments
You can choose from several types of broadband access technologies to provide
symmetric or asymmetric connectivity to a small business. These technologies
vary on the available bandwidth and on the quality of service. For voice
deployments, it is generally recommended that you use broadband access with a
Service Level Agreement that provides quality of service. If there is not a Service
Level Agreement with regard to the broadband connection quality of service, the
downstream audio quality may be affected negatively under heavy load
conditions (bandwidth utilization beyond 80%).
To eliminate or minimize this effect, Cisco recommends one of the following
actions:
•
For broadband connections with a bandwidth lower than 2 Mbps, perform the
call capacity calculations by assuming a bandwidth value of 50% of the
existing broadband bandwidth. For 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.