[Serusers] "stun" parameters in Contact HF

Hi all, I'm testing a new UA and I've got a Contact Header Field format in REGISTER msg I'm not aware of: REGISTER sip:/sip.mydomain.com/:5060 SIP/2.0. Via: SIP/2.0/UDP *0.0.0.0:0;*branch=z9hG4bK2497750963. From: <sip:/pstn_number/@/sip.mydomain.com/>;tag=3670695360. To: <sip:/pstn_number/@/sip.mydomain.com/>. Call-ID: 2377110845(a)192.168.1.4. CSeq: 1 REGISTER. Contact: <sip:/pstn_number/*@0.0.0.0:0;**stun=4*>. max-forwards: 70. expires: 3600. user-agent: oSIP/Linphone-1.1.0-IMVP. Allow: INVITE, ACK, CANCEL, OPTIONS, BYE, REFER, NOTIFY, INFO. Content-Length: 0. i.e. ip:port is no longer in Contact or Via Header Fields and a stun=4 parameter is specified in Contact HF Have you got any clue on RFC reference for this behaviour? How can I handle this on SER? (SER fills location table as follows: username: /pstn_number/ domain: /sip.mydomain.com/ contact: sip:/pstn_number/@0.0.0.0:0;stun=4 received: sip:/UA_ip_address/:5060 ) THX, Mety