[SIPForum-discussion] To-Tag in REGISTER message

[Partha Ray]

Hi Keerthi,

This is a good question. I have seen the answers given by other.

REGISTRAR should throw 403 in your case. I have seen the same earlier. When
the second register message comes in with no to-tag but incremented cseq,
then REGISTRAR validates the call-id(which is existing), from-tag(which is
there), cseq increased which tells about a subsequent register with
'response' calculated according to 'nounce' value) but can't see any to-tag.

But this is also depends on device implementation. Some manufacturer
implement this to challenge again. This means REGISTRAR would again send
401 with new 'nounce' value as they treat this as a new request because
of missing to-tag.

BR,
Partha


On Tue, Oct 30, 2012 at 4:17 AM, Keerthi Srinivasan <
keerthivarmansrinivasan at gmail.com> 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. 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)
>
> 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?
>
> --
> Regards,
> Keerthi
>
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