We need a SIP B2BUA implementing which will talk secure SIP on one side and SIP on the other - to allow us to connect clients which will only speak secure SIP to an IP PABX which only speaks vanilla SIP. The SIPX stack (from [url removed, login to view]) implements SIP and Secure SIP. There's an example B2BUA at [url removed, login to view] but it's got a number of limitations, including answering incoming calls immediately so as to be able to present call progress tones. We need ours to support early media.
Any questions, please post to the project discussion board or PM.