[asterisk-users] 407 Proxy Authentication Required

[unplug]

There is a problem between 2 asterisk servers in message 407.  In the
normal flow, it should something like diagram1.  However, in my case,
I got the situation as diagram 2 and the call dropped finally.  Does
anyone have the same problem with me?  How to solve the problem?
Anyone can help?

UA1	AST1	AST2	UA2
----INVITE-->
<---407----
---ACK------>
----INVITE-->
	-----INVITE-->
		-----INVITE-->
-----------continue as normal----------
diagram1


UA1	AST1	AST2	UA2
----INVITE-->
<---407----
---ACK------>
----INVITE-->
	-----INVITE-->
	<-----407-----
	-----ACK------>
----------call drop after timeout---------
diagram2