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4.3.3.3 Media Settings
Once a VoIP call is established, the Media channel is used for voice transmission. The
settings listed below configure the performance and operation of the Media channel.
1.
RTP Port (range)
– Audio stream is transmitted via Real Time Protocol (RTP) and at
least 4 ports are used per voice channel. The default port range is 16384 – 32768.
Specify the port range depending on your network environment if needed.
2.
Packet length (ms)
– This specify the length of a voice packet. The default packet
length is 20 ms.
3.
Jitter Buffer Mode
–
Three jitter modes are available. The
Fixed Mode
, which is
the default mode, is a simple first in first out mode, with a fixed jitter buffer delay.
By definition the jitter buffer depth is twice the jitter buffer delay. The
Sequential
Mode
is also a fixed jitter buffer delay mode, but in this mode the jitter buffer
function looks at the packet timestamp for dropped or out of sequence packet
problems. The data packets are sorted based on the packet timestamp. The
Adaptive Mode
optimizes the size of the jitter buffer delay and depth in response
to network conditions, in addition to the sequential mode.
4.
Media QoS
– QoS is also available for Media packets to improve voice quality. This
is rather significant in a network environment with large amount of data traffics. Both
IP TOS
and
DiffServ
methods are supported.
5.
Encryption
– For secure voice transmission, RC4 Encryption can be enabled for
media channel. Please make sure your service provider can support this encryption
method before enabling this feature.
6.
Symmetric RTP
– Enable the media channel to use symmetric RTP ports. Some
network environment demand the use of Symmetric RTP.
