[Serusers] Security methods for PSTN termination of SIP calls

Hi, When providing PSTN termination of calls that originate from a SIP source how do you go about validating the identity of where the calls originated from - the SIP Proxy or the SUA. PSTN ---- SIP Proxy 1--- + --- SIP Proxy 2 ---- PSTN So the calls originate from the PSTN in a country, get transported across the internet and terminated in a different country via another company. Other than source IP address, what method could you use to validate the origin of the calls? Also in question is security for trunk services for companies that simply want to terminate calls out onto the PSTN. How can you setup a trust relationship between the two proxies? Is any one here in a similar situation?? Regards, Alan ------------------------------------------------------------------------------------------------------- This email, and any files transmitted with it, is copyright and may contain confidential information. The contents are intended for the use of the addressee(s) only. Unauthorized use may be unlawful. If you receive this email by mistake, please advise sender immediately. The views of the author may not necessarily constitute the views of Telco Electronics Limited. Nothing in this mail shall bind Telco Electronics Limited in any contract or obligation. Telco Electronics Limited 6-8 Oxford Court Brackley Northants NN13 7XY Tel 01280 761600 Fax 01280 841174