This might be what you're looking for, this is a SIP Profile parameter: <param name="NDLB-sendrecv-in-session" value="true"/> https://freeswitch.org/confluence/display/FREESWITCH/NDLB It may also be possible to re-write the SDP per call: https://freeswitch.org/confluence/display/FREESWITCH/Codec+Negotiation#Codec... ________________________________ From: FreeSWITCH-users <freeswitch-users-bounces@lists.freeswitch.org> on behalf of Oleg Belousov <obelousov@gmail.com> Sent: 12 September 2020 22:22 To: FreeSWITCH Users Help <freeswitch-users@lists.freeswitch.org> Subject: [Freeswitch-users] Add a=sendrecv onto sdp Hi. Please advise how I can add a=sendrecv parameter onto the SDP part of 183 Session progress. I'm using preAnswer in lua script to respond 183 with SDP to an invite. -- obelousov.tel<http://obelousov.tel>