SIP custom fields

Hi all,

I’m trying to use an asterisk PBX to connect devices using a customized SIP version.

This devices use additional field both within INVITE method and 200OK.

I’ve experienced that asterisk act as a back to back entity and so re-generates the SIP messages from zero, removing all the custom fields.

Moreover I’ve used SIPAddHeader and I was able to copy and paste the custom fields within the INVITE Method… but my connections con’t comes up because additional headers are “removed” from 200OK message. So I guess SIPAddHeader is not the right way.

Is there a way to make these message pass through asterisk as they are? Moreover is MESSAGES not managed by asterisk?

Thank You in advance.