It should not change during the call. The rules prohibit that. The only way to change the remote target address within a dialog is, ironically, via a reinvite and/or response, but that would need to come from the UA itself.

Your best bet to ensure that the NAT pinhole to the endpoint does not go away during the call is some sort of keepalive, be it the NAT "ping" functionality of the nathelper module or the in-dialog OPTIONS pings from the dialog module. That should keep the NAT mapping refreshed.

If the endpoint still becomes unreachable, there's not much you can do. Nothing that would conform to the protocol state machine, anyway. :-)

--
Alex Balashov | Principal | Evariste Systems LLC
303 Perimeter Center North, Suite 300
Atlanta, GA 30346
United States

Tel: +1-800-250-5920 (toll-free) / +1-678-954-0671 (direct)
Web: http://www.evaristesys.com/, http://www.csrpswitch.com/

Sent from my Nexus 10.
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