Avaya Application Solutions Deployment Manual page 280

IP Telephony network engineering overview
The critical objective factors in assessing IP Telephony quality are delay, jitter, and packet loss.
To ensure good and consistent levels of voice quality,
lists Avaya's suggested network requirements. These requirements are true for both LAN only
and for LAN and WAN connections.
Table 66: Factors that affect voice quality
Network factor
Delay
(one-way between
endpoints)
Jitter
(variability of the delay
between endpoints)
Packet loss
(maximum packet/
frame loss between
endpoints)
1. All measurement values are between endpoints because this document assumes that IP Telephony is
not yet implemented. All values therefore reflect the performance of the network without endpoint
consideration.
2. Also, "business-communication quality" is defined as less than toll quality, but much better than
cell-phone quality.
For more information see
280 Avaya Application Solutions IP Telephony Deployment Guide
1
Measurement
A delay of 80 ms or less can, but may not, yield the best
quality.
A delay of 80 ms to 180 ms can yield
business-communication quality. Business-communication
quality is much better than cell-phone quality, and is
well-suited for the majority of businesses.
Delays that exceed 180 ms might still be quite acceptable
depending on customer expectations, analog trunks used,
codec type, and so on.
20 ms, or less than half the sample size, for the best quality.
Note:
This value has some latitude, depending on the
Note:
type of service that the jitter buffer has in
relationship to other router buffers, the packet size
used, and so on.
<1% can yield the best quality, depending on many factors.
<3% should give business-communications quality, which is
much better than cell-phone quality.
>3% might be acceptable for voice, but might interfere with
signaling.
Voice quality network
Table 66: Factors that affect voice quality
2
requirements.
2