Nortel Remote Office 9150 Installation And Administration Manual page 74

Remote Office 9150 description
Transitions are transparent to the users and can take place during a live call.
The one exception is in the event of a complete network failure.
Note: A slight degradation in voice quality can occur during the transition.
4. An IP test is run to determine if the QoS has been restored on the IP
network. See "Offline IP network measurements" on page 49.
5. When the IP QoS exceeds the Y threshold, the system waits for duration Q
to ensure that the QoS is stable enough to resume service on the IP network.
6. If the QoS continues to exceed the Y threshold, all active calls are moved
back to the IP network and all new calls are placed over the IP network.
Quality of Service traffic measurements
As each voice packet is sent over the IP network, the Remote Office 9150 unit
monitors the following QoS parameters:
average packet delay
The delay is calculated using the following statistics gathered from the
Remote Office 9150 unit's voice jitter attenuation buffer:
minimum packet holding time in the jitter buffer
maximum packet holding time in the jitter buffer
peak holding time in the jitter buffer
time-stamp values in the packet header
By accumulating these statistics over time, the Remote Office 9150 unit can
calculate an average packet delay value through the IP network. As the
system detects an increase in the average packet delay, it references the
signal degrade threshold to determine when the transition to the PSTN
connection should be made.
See Chapter 7, "Administration" for a detailed description of statistics.
lost packets
Lost packet statistics are calculated by accumulating the following packet
header and voice decoder statistics:
voice decoder underrun
voice decoder overrun
out-of-sequence packet reception
48
Standard 1.0
Remote Office 9150