comments in-line

"Christer Holmberg (KI/LMF)" <[EMAIL PROTECTED]> wrote:
Hi,
 
Comments inline ([CHH])

 
Hi,
 
This is related to INVITE transaction on unreliable transport.
 
 UAC                                   UAS
------                                ------
-------------------------------> INVITE
<------------------------------- 300 Multiple choices
--------------------------------> ACK
<------------------------------- 500 Server internal error (before the Timer D fires)
--------------------------------> ACK
 
Suppose the "To-tag" in the second final response (500) sent by UAS is different than the one in the initial response (300),  
 
[CHH] Why would the UAS (I assume it's the same UAS sending both responses) send two different final responses to the INVITE? A UAS only sends one final response to the INVITE (or any request).
 
1. how should the UAC behave? 
 
[CHH] I would accept the 300, send the ACK, and most likely treat the 500 as a retransmit of the 300. 
 
[Rama] Once UAC has sent out an ACK, the transaction from its-stand-point ends. So now when a 500 comes in, it should treat it as 'call-leg does not exist' for that and just do a No-Op.
 
2. And what should be the value of the "To-Tag" in the ACK sent by UAC for 500 response? 
 
[CHH] I would retransmit the ACK I sent for the 300 response, using the same header values.
 
Regards,
 
Christer Holmberg
Ericsson Finland
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