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List:       sip-implementors
Subject:    Re: [Sip-implementors] 487 after BYE on early dialog
From:       Paul Kyzivat <pkyzivat () cisco ! com>
Date:       2009-05-13 14:19:17
Message-ID: 4A0AD6E5.4060207 () cisco ! com
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Dale Worley wrote:
> On Tue, 2009-05-12 at 08:47 +0200, Damir Reic wrote:
>> If UAS receives BYE on early dialog and answers it with 200OK, does it have
>> to respond to initial invite with 487 (same as CANCEL was received)?
> 
> In RFC 3261 section 15.1.2, it says:
> 
>    The UAS MUST still respond to any pending requests received for that
>    dialog.  It is RECOMMENDED that a 487 (Request Terminated) response
>    be generated to those pending requests.

Elaborating:

The uas MUST send *some* final response to the INVITE.
487 is the recommended response, but others could be used.
For one thing, there could be a race, the the response could be in 
flight already when the BYE is received, so the UAC might get most any 
final response. If not, the UAC might still decide some other final 
response is more appropriate. For instance it might send some 5xx response.

	Thanks,
	Paul

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