Wide Area Network (Wan) Quality Of Service - Linksys SPA921 - Cisco - IP Phone Installation And Configuration Manual

Preparation
System Design Considerations
SPA9000 Voice System Installation and Configuration Guide for Setup Wizard
Codec Approximate bandwidth
budget for each side of
conversation
G.726- 63 kbps
16
G.729 55 kbps
For more information about bandwidth calculation, refer to the following web sites:
www.erlang.com/calculator/lipb/
www.bandcalc.com/

Wide Area Network (WAN) Quality of Service

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. 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.
2 calls 4 calls
126 252
kbps kbps
110 220
kbps kbps
3
6 calls 8 calls
378 504
kbps kbps
330 440
kbps kbps
32