it rewrites the ip port (the private ip port of the device sent with it's contact info is replaced with the ip port of the public address of that related client) _____ From: serusers-bounces(a)iptel.org [mailto:serusers-bounces@lists.iptel.org] On Behalf Of Yi Zheng Sent: Tuesday, January 24, 2006 1:54 AM To: ser sip Subject: [Serusers] NAT travesal: force_rport() what does it do? Hi, I am reading to understand the different solutions for NAT travesal. For nathelper+RTP proxy solution, what does the force_rport() function do? Is it rfc3581 compliant? Does it mean that the client needs to understand "received" and "rport" in the Via header? Thanks, - ming