Nortel ISDN Signaling Link, Description, Installation And Operation

Page: 79 / 380

ITG Engineering Guidelines Page 79 of 378
ITG Trunk 2.0 ISDN Signaling Link (ISL) Description, Installation and Operation
where loss level cannot compensate, silence suppression should be disabled
using the MAT ITG ISDN Trunk Node Properties DSP profile tab codec
options sub-tab. See Step 8 on page 203.
Disabling silence suppression approximately doubles LAN/WAN bandwidth
use. Disabling silence suppression consumes more real-time on the ITG card.
Table 6 shows the bandwidth requirement when silence suppression is
disabled.
Note that this does not impact the data rate for fax, since it does not have
silence suppression enabled to begin with.
Simultaneous voice traffic with silence suppression
When voice services with multi-channel requirements are extensively used in
an ITG network, such as Conference, Music-on-hold, and
Message-Broadcasting, additional voice traffic peaks to the IP network will
be generated due to the simultaneous voice traffic bursts on multiple channels
on the same links.
In those cases, even when silence suppression is enabled on the ITG card, the
more conservative bandwidth calculations of Table 6 with silence
suppression disabled is recommended to calculate the portion of the
bandwidth requirement that is caused by simultaneous voice traffic.