Nortel ISDN Signaling Link, Описание, установка и эксплуатация, Страница: 141 / 380

ITG Engineering Guidelines Page 141 of 378
ITG Trunk 2.0 ISDN Signaling Link (ISL) Description, Installation and Operation
ITG network inventory and configuration
You must record the current ITG design and log all adds, moves and changes
to the ITG network that occur. The following data must be kept:
• ITG site information
— location
— dialing plan
— IP addressing
• Provisioning of ITG nodes - number of cards and ports
• ITG node and card parameters
— fall back threshold level
— codec image
— voice and fax payload
— voice and fax playout delay
— audio gain, echo cancellor tail delay size, silence suppression
threshold
— software version
User feedback
Qualitative feedback from users helps confirm if the theoretical QoS settings
match what end users perceive. The feedback can come from a Helpdesk
facility, and must include information such as time of day, origination and
destination points, and a description of service degradation.
The fall back threshold algorithm requires a fixed ITG system delay of 93 ms,
which is based on default ITG settings and its delay monitoring probe
packets. The fall back mechanism does not adjust when ITG parameters are
modified from their default values. Users can perceive a lower quality of
service than the QoS levels at the fall back thresholds when:
• Delay variation in the intranet is significant. If the standard deviation of
one-way delay is comparable with the voice playout maximum delay, it
means that there is a population of packets that arrive too late to be used
by the ITG node in the playout process.