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.
NAT Enable this option when the PBX uses a public IP address. The feature is enabled by default.
Note: If you manually set up Linkus server, make sure the desired extension's NAT is enabled, or the extension user can not access Linkus when he or she is out of local network.
SRTP Enable SRTP for voice encryption.