Hello, I am trying to register with a Deutsche Telekom SIP Trunk. The Deutsche Telekom technical documentation states that the client must set the following SIP header fields: For an initial REGISTER without Authentication Challenge the SIP Header fields - Security-Client: sdes-srtp;mediasec - Proxy Request: mediasec - Requirement: mediasec shall be included. The platform replies with SIP 401 Unauthorised and contains the SIP header fields - Security server: msrp-tls;mediasec - Security server: sdes-srtp;mediasec - Security server: dtls-srtp;mediasec with indication of the possible encryption methods. For the following REGISTER with Authentication Challenge, in addition to the originally included SIP header fields Security-Client, Proxy-Require, Require the SIP header fields - Security Check: msrp-tls;mediasec - Security check: sdes-srtp;mediasec - Security check: dtls-srtp;mediasec shall also be included. According to RFC3261, the Security-Verify header fields can also be combined as a single header field. I have seen, that the Sofia-Stack has implemented these Fields. But I have not found a way to set these header fields in the REGISTER message. (For the INVITE messages I'm using the set action sip_h_*; not sure if this is correct. There I have the Problem, that I'm not able to set the SDP Attribute a=3ge2ae:requested) Regards, Johannes