[SIPForum-discussion] Bye Method

[Paul Kyzivat]

On 6/19/15 3:39 PM, Suman Mohanty wrote:
> Hi All,
>
>      Can anyone explains  in which scenario we can send bye message
> after receiving the 180 ringing?

If A calls B and B returns 180 ringing, then there are good reasons for 
A to send BYE to B:

1) A changes mind about call and hangs up before getting a final response;

2) call is forked to B1 and B2. A decides to send BYE to B1 and wait on B2.

There aren't very good reasons for B to send BYE to A, because it is in 
a position to send a variety of final error responses that are more 
specific than Bye.

I don't *think* it is forbidden. A robust implementation should probably 
do the reasonable thing in this case. I would treat it as semantically 
equivalent to a 603 response. (But note that you still need to send an 
ACK to the INVITE.)

	Thanks,
	Paul