Aastra Telecom 41-001343-02 manual Out-of-Band Dtmf and Dtmf Method, RTP Encryption

		Global SIP Settings
15	118	AMR (G.722.2) (Licensed feature for 6735i, 6737i,
		6863i, 6865i, and 6867i only)
16	119	AMR-WB (G.722.2) (Licensed feature for 6735i,
		6737i, 6863i, 6865i, and 6867i only)

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 and DTMF Method

The IP phones support out-of-band Dual-Tone Multifrequency (DTMF) mode as referenced in 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.

An additional feature on the IP phone allows you to select the DTMF method that the phone uses to send DTMF digits from the IP phone via INFO messages. You can set the DTMF method as Real-Time Transport Protocol (RTP), SIP INFO, or both. You can configure the DTMF method on a global or per-line basis using the configuration files or the Aastra Web UI.

The matrix below details DTMF behavior when the out-of-band DTMF and DTMF method settings are configured in vari- ous scenarios:

Web UI Setting/Configuration Parameter Setting		DTMF Behavior
DTMF Method/	Force RFC2833 Out-of-Band DTMF/	SIP INFO	In-Band DTMF	Out-of-Band DTMF
sip dtmf method	sip out-of-band dtmf			(RFC2833)
RTP (0)	Disabled (0)	No	Yes	No
RTP (0)	Enabled (1)	No	No	Yes
SIP INFO (1)	Disabled (0)	Yes	No	No
SIP INFO (1)	Enabled (1)	Yes	No	Yes
RTP and SIP INFO (2)	Disabled (0)	Yes	Yes	No
RTP and SIP INFO (2)	Enabled (1)	Yes	No	Yes

RTP Encryption

The IP Phones include support for Secure Real-time Transfer Protocol (SRTP), using Session Description Protocol Security (SDES) key negotiation, for encryption and authentication of RTP/RTCP messages sent and received by the Aastra IP phones on your network.

As administrator, you specify the global SRTP setting for all lines on the IP phone. You can choose among three levels of SRTP encryption, as follows:

•SRTP Disabled (default): IP phone generates and receives non-secured RTP calls. If the IP phone gets called from SRTP enabled phone, it ignores SRTP tries to answer the call using RTP. If the receiving phone has SRTP only enabled, the call fails; however, if it has SRTP preferred enabled, it will accept RTP call.

•SRTP Preferred: IP phone generates RTP secured calls, and accepts both secured and non-secured RTP calls. If the receiving phone is not SRTP enabled, it sends non-secured RTP calls instead.

•SRTP Only: IP phone generates and accepts RTP secured calls only; all other calls are rejected (fail).

You can override the global setting as necessary, configuring SRTP support on a per-line basis. This allows IP phone users to have both secured and unsecured lines operating on the same phone.

41-001343-02 REV04 – 05.2014 4-79