Aastra Telecom 53I, 57I CT, 55I manual Customized Codec Settings, Out-of-Band Dtmf, Attribute Value

Configuring Network and Session Initiation Protocol (SIP) Features

Global SIP Settings

Silsupp is used to enable or disable silence suppression. Voice Activity Detection (VAD) on the IP phones is used to determine whether each individual packet contains useful speech data. Enabling silsupp results in decreased network bandwidth, by avoiding sending RTP packets for any frame where no voice energy was detected by the VAD.

You must enter the values for this feature in list form as shown in the following example:

payload=8;ptime=10;silsupp=on; payload=0;ptime=10;silsupp=off

The valid values for creating a Codec preference list are as follows.

Customized Codec Settings

Attribute	Value
payload	0 for G.711 u-Law
	8 for G.711 a-Law
	18 for G.729a
ptime (in milliseconds)	5, 10, 15, 20.......90
silsupp	on
	off

You can specify a customized Codec preference list on a global-basis using the configuration files or the Aastra Web UI.

Out-of-Band DTMF

The IP phones support out-of-band Dual-Tone Multifrequency (DTMF) mode according to RFC2833. In the Aastra Web UI, you can enable or disable this feature as required. The "out-of-band DTMF" is enabled by default.

In out-of-band mode, the DTMF audio is automatically clamped (muted) and DTMF digits are not sent in the RTP packets.

You can configure out-of-band DTMF on a global-basis using the configuration files or the Aastra Web UI.

Configuring the IP Phones

41-001160-00, Release 2.1, Rev 04 4-67