On 10/30/12 7:17 AM, Keerthi Srinivasan wrote:
> All,
>
> When UA sends REGISTER request to the server it does not contain the To-Tag
> and Server is accepts the Registration (200 OK) will have the To-Tag.
>
> If the Refresh or Deregister does not have the To-Tag in the REGISTER
> message.
REGISTER is peculiar. It uses to- and from- tags, callid, and CSeq like
a dialog. But it otherwise isn't a true dialog.
This pseudo-dialog isn't of any great utility according to what is
specified in 3261. There is nothing to prevent you from forgetting it
and starting over with a new from-tag and callid in a subsequent
REGISTER to refresh a particular contact. Doing so might bother some
implementations even though it is conforming.
BUT, that "dialog" is significant to the way a registrar manages GRUUs.
(RFC 5627). In particular it determines when temporary gruus expire.
> Is the server will accept the Refresh or Deregister REGISTER
> message or will send 482 Loop Detected as per the RFC3261 (8.2.2.2 Merged
> Requests)
Well, if you sent your refresh with the same from-tag and callid and
cseq, and you sent it soon enough, then you *might* get caught up in
this. But if you do that then you have a really broken implementation.
If you aren't setting up the registration pseudo-dialog state, including
remembering from-tag, to-tag, callid, next valid cseq, etc., then when
you send the next REGISTER you should be treating it as *new* and
assigning a *new* from-tag, callid, and cseq.
Thanks,
Paul
> Here is the RFC3261 content:
> 8.2.2.2 Merged Requests
>
> If the request has no tag in the To header field, the UAS core MUST
> check the request against ongoing transactions. If the From tag,
> Call-ID, and CSeq exactly match those associated with an ongoing
> transaction, but the request does not match that transaction (based
> on the matching rules in Section 17.2.3), the UAS core SHOULD
> generate a 482 (Loop Detected) response and pass it to the server
> transaction.
>
> The same request has arrived at the UAS more than once, following
> different paths, most likely due to forking. The UAS processes
> the first such request received and responds with a 482 (Loop
> Detected) to the rest of them.
>
> Is the Server MUST reject or Accept the Refresh / Deregister REGISTER
> request?
>
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