the "sip-session-expires" trigger early

Created by: lizhenghn123

I use unimrcp for server. When then client is "keep-alive" connection, but not send sip option msg.

I find that if client don't send option for heartbeat， unimrcp would re-send some sip signal to client.

I modify the "sip-session-expires" from 600(default value) to 189216000(3 years), wish the unimrcp don't send any sip msg by itself. But i find that the "sip-session-expires" timer would trigger earlier other than 3 years.

So did i miss some thing? Can you give me some advice ? Thanks a lot!