禁止重複登陸：
kamailio.cfg中，將if (!save("location"))改成if (!save("location","0x04"))，重啓服務即可
響鈴超時：
# ----- tm params -----
# auto-discard branches from previous serial forking leg
modparam("tm", "failure_reply_mode", 3)
# default retransmission timeout: 30sec
modparam("tm", "fr_timer", 5000)
# default invite retransmission timeout after 1xx: 120sec
modparam("tm", "fr_inv_timer", 120000)