Advanced Settings of SIP Extension

This topic describes the advanced settings of a SIP extension.

Note: The SIP configurations require professional knowledge of SIP protocol. Incorrect configurations may cause calling issues on the SIP extension.
Setting Description
DTMF Mode Set the mode for sending DTMF tones.
  • RFC4733 (RFC2833): DTMF will be carried in the RTP stream in different RTP packets.
  • Info: DTMF will be carried in the SIP info messages.
  • Inband: DTMF will be carried in the audio signal.
  • Auto: If the device supports RFC4733 (RFC2833), PBX will choose RFC4733 (RFC2833), otherwise the PBX will choose Inband.
Transport Select one or multiple transport protocols: UDP, TCP, TLS.
Note:
  • The TCP option is available only when the SIP TCP Port is enabled (Path: PBX Settings > SIP Settings > General > Basic), and it is selected by default together with UDP.
  • The TLS option is available only when the TLS is enabled (Path: PBX Settings > SIP Settings > TLS).
  • When multiple protocols are selected, the following priority rules are applied:
    • Linkus UC Clients: TLS > TCP > UDP
    • IP Phone: Uses the phone's specified protocol if available; if not specified, follows the same priority as Linkus UC Clients (TLS > TCP > UDP).
Qualify Enable this option to send SIP OPTION packet to SIP device to check if the device is up.
T.38 Support Enable or disable T.38 fax for the extension.
Note: Enabling T.38 will add performance cost. We recommend that you disable T.38.
SRTP Enable SRTP for voice encryption.