Force asterisk to resend SDP upon receiving 200 OK


can any one guide me how to force my asterisk box (v11.3) to (re)send SDP upon receiving “200 OK with SDP” from far-end ?

SIP only requires that when the OK is in response to INVITE and the INVITE didn’t include SDP. There is no option to override the SIP standard.

Asterisk will add SDP on re-invites, so you may be able to engineer a situation where there is a prompt re-invite.

What is the problem that you are really trying to solve with non-compliant behaviour?

I have to comply to a non-Standard Huawei switch that require SDP in “200 OK”, though we have already sent SDP in the INVITE

If you have sent an INVITE, it is illegal to send OK in the same transaction.

Do you really mean the ACK and that the Huawei is insisting on late offer, and is ignoring the early offer?

Re-sending the SDP would not really be right in that case, as some of the SDP may have to be changed as a result of their offer; SDP in an ACK is sent in response mode, not in the offer mode used for INVITE, or at least should be (at least some versions of Asterisk are flawed in this area, but that may have been fixed since 1.6.).

I would add that late offer exists for the benefit of the UAC, not for the benefit of the UAS. It actually causes problems for the UAS as it cannot cleanly reject the call and has to accept it and then immediately issue BYE. As such HuaWei are doing themselves a dis-service if they require it when acting as a UAS.

Yeah, there is no way to currently do this and a better description would be needed to understand exactly when and where the softswitch would like the SDP.

I will request far-end to comply to standard :slight_smile: