3Com 3C10111C - NBX 100 - Modular Exp Base Installation Manual page 59

Installation Questions 59
Silence Suppression
Silence suppression enables you to reduce network traffic. When silence
suppression is enabled, the NBX device detects silence in the audio
stream, such as a pause in conversation, and stops sending packets. The
receiving NBX device generates white noise for the periods represented
by silence indicator packets so that the listener does not hear true silence
and worry that the call has been disconnected. The receiving NBX device
can be another 3Com telephone, or for external calls, it can be an Analog
Line Card port or a channel on a Digital Line Card.
A careful listener might notice the difference between generated and
actual background noise, so silence suppression is turned off by default.
Silence Suppression settings result in compromises to audio quality. Do
not enable Silence Suppression unless you are trying to solve bandwidth
constraint issues.
You can enable or disable silence suppression for the entire system or for
individual telephones and line card ports.
NBX System Quality of Service
Quality of Service (QoS) is a way to allocate resources in data switches
and routers so that data can be prioritized, with the most time-critical
data receiving higher priority. At Layer 2, the NBX system supports
Ethernet 802.1Q, "Standard for Virtual Bridged Local Area Networks,"
and its associated specification, 802.1P, "Standard for Local and
Metropolitan Area Networks, Supplement to Media Access Control
(MAC) Bridges: Traffic Class Expediting and Dynamic Multicast Filtering."
These IEEE Ethernet standards define how Ethernet packets can be
prioritized.
At Layer 3, the NBX supports IP Precedence, also called IP Type Of Service
(ToS), to specify the class of service for each packet. The default
hexadecimal value for NBX system IP ToS settings is 0xb8.