164 ITG engineering guidelines
When a system equipped with an IP Trunk3.01 (and later) node serves as a
tandem switch in a network where some circuit-switched trunk facilities have
an excessively low audio level,Silence Suppression, if enabled, degrades
the quality of service by causing choppiness of speech.
Under tandem switching conditions where loss levelcannot compensate,
disable Silence Suppression using the TM 3.1 ITG ISDN TrunkNode
Properties DSP profile tab codec options sub-tab. See Step 8 on Step 8.
Disabling Silence Suppression approximately doublesLAN/WAN bandwidth
use. Disabling Silence Suppression consumes more real-time on the IP
trunk card.
Table17 "Silence Suppression disabled TLAN Ethernet and WAN IP
bandwidth usage per IP Trunk 3.01 (and later) " (page 113) shows the
bandwidth requirement when Silence Suppression is disabled. This does
not impact the data ratefor fax, since fax does not have Silence Suppression
enabled.

Fallback threshold

There are two parameters, the receive fallback threshold and the transmit
fallback threshold, which can be configuredon a per-site pair basis.
"Set QoS expectations" (page 139) and "Measure intranet QoS" (page
139) sections describe the process of determining the appropriate QoS
levelfor operating the IP Trunk 3.01 (and later) network. Site pairs can have
very different QoS measurements if some traffic flows are local, while other
traffic flows are inter-continental. Consider setting a higher QoS level for
the local sites compared to the international sites, thus keeping costs of
international WAN links down.
Normally,the fallback threshold in both directions is set to the same QoS
level. In site pairs where one direction of flow is more important, set up
asymmetric QoS levels.

Setting the QoS threshold for fallback routing

The QoS thresholds for fallback routing are configured in TM 3.1. A
threshold is configured for the "Receive fallback threshold" as well as the
"Transmitfallback threshold." The available thresholds are Excellent, Good,
Fair, and Poor.
Post-installation network measurements
The design process is continual, even after implementation of the IP Trunk
3.01 (and later) network and commissioning of voice services over the
network. Network changes in the following – IP Trunk 3.01 (and later) traffic,
general intranet traffic patterns, network policies, network topology, user
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21 December 2007
Copyright© 2007, Nor tel Networks
.