19.2.1.3.1. General Notes 
While a DMC is active only SID (Silence Insertion Descriptor)/CN (Comfort
Noise) frames are sent on the master connection if involved components
are configured with VAD (see Section 2.3.3,
“Voice Activity Detection (VAD)”). Therefore this
master connection needs only a reduced bandwidth.
You can find the tables for bandwidth in the document “Gateways
HG 3500 and HG 3575”, Section 2.5.4,
“Required Bandwidth per Connection”
For additional information about bandwidth administration please refer
to the Resource Manager and AMO GKTOP.
By inserting SID/CN, analog background noise is simulated digitally
during silence to assure the listener that the link is active and operational.
The background noise RTP packets with CN flag are sent on the master
or slave connection once per second.