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 lo g all a dds, moves a nd chan ges
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 co nfir m if the the oret ical QoS se ttings
match what end us ers perceive. The fee dback can come fr om a Helpdesk
facility, and must include information such as time of day, origin ation and
destination points, and a description of service degradation.
The fall back threshold algorithm requires a fixe d ITG system dela y of 93 ms,
which is based on default ITG settings and its delay monitoring probe
packets. The fall back mech an i sm d oe s no t adju s t when IT G pa r ame t ers are
modified from their default values. Users can perceive a lower quality of
service than the QoS levels at the fall back thr esholds when:
• Delay variation in the intranet is significant. If the standard deviation of
one-way delay is comparable with the voice playout m aximum 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.