From: NTT COMWARE Hidehisa Matsutani <[EMAIL PROTECTED]>
(1) What do you think of the sequence?
Is UAC allowed to send BYE just after it sends INVITE(session timer
refresh)? Or should UAC send after the INVITE transaction?
(In the other words, F2 should be sent after F1 transaction is completed,
shouldn't it?)
(2) If the sequence is allowed, when should UAC stop the re-transmission
for the INVITE?
I think the re-transmission should be stopped when BYE transaction is
started, -- after F2.
Someone says re-transmission should be stopped after 200(BYE) is
received, -- after F3.
Which is better do you think?
UAC UAS
| |
The session has been already established
==========================
| |
| F1 |
|--------------------->| INVITE(Session timer refresh)
| F2 |
|--------------------->| BYE
| F3 |
|<---------------------| 200(BYE)
| F4 |
|--------------------->| INVITE(re-transmit of F1)
| F5 |
|<---------------------| 481(INVITE)
| : |
| : |
| F6 |
|<---------------------| 481(INVITE) re-transmit of F5
| |
In support of Paul -- There seems to be no reason that the UAC can't
send a BYE while the re-INVITE is pending. (It can't send the BYE
before getting at least a provisional response from an original
INVITE, but that is because until it receives a response, it doesn't
know the to-tag, and so it is impossible send a BYE within the
dialog.)
The UAC, upon receiving the BYE, will terminate the dialog. The UAC,
upon receiving the 200 to the BYE could abandon the INVITE, I suppose,
but it would be poor design to do so.
But when the UAS receives the retransmission of the INVITE, it is
out-of-sequence, since the UAS has already processed the BYE. So it
must reject the INVITE with a 500 response. I believe that the
sequence-check must be done before any semantic processing of the
request, so it can't be argued that a 481 response is acceptable.
Dale
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