Sunil,
Its not clear to me if you have a question for sip-implementors, or a
question for IMS-implementors.
The reg event package provides a way to monitor the status of *all* the
registrations for a particular AoR. The fact that a UA has unregistered
itself (or been unregistered) does not mean it has no interest in other
registrations. If indeed it has no further interest it is certainly free
to terminate its subscription. But it is the one that can determine the
continued need, not the registrar.
For instance, I can certainly imagine a "backup" UA that monitors
registrations on an AoR, and only registers itself if it sees that there
are no other registrations.
And from a practical perspective, a subscription to the reg event
package is the way a UA can learn that it has been unregistered and
might want to try registering again. If the subscription is terminated
at the time the registrar terminates the registration, then the
notification of unregistration can't be sent.
Thanks,
Paul
On 1/13/2011 7:24 AM, Sunil wrote:
> Hi All,
>
> According to the 3GPP 24.229 spec,
>
> Upon successful de-registration UA should not delete the dialog for
> Subscription to reg event package if it had subscribed.
>
>
> Exerts from 24.229:
> ------------------------------------------------------------------------------------------------------------------------------------
> Prior to sending a REGISTER request for deregistration, the UE
> shall release all dialogs related to the public user identity that is
> going to be deregistered or to one of the implicitly registered public
> user identities.
>
> However:
> - if the dialog that was established by the UE subscribing
> to the reg event package used the public user identity that is going to
> be deregistered ; and
> - this dialog is the only remaining dialog used for
> subscription to reg event package;then the UE shall not
> release this dialog.
> -----------------------------------------------------------------------------------------------------------------------------------------
>
> What is the use of keeping this dialog when registration itself is
> removed as Subscription to reg event package tells about the
> registration status.Upon successful de-registration UA knows that its
> registration status for that user is terminated.So is it not right to
> delete the Subscription to reg event package on deregistration ?
>
> Also from the same spec,it tells that if signaling security is
> involved(IPsec/tls),on deregistration security associations will be
> deleted and further messages can not be received. So if UA does keep the
> dialog
> even after deregistration and the server tries to send NOTIFY WITH
> TERMINATED STATE ,it won't reach the UA as already security associations
> are deleted.
> -------------------------------------------------------------------------------------------------------------
> When the UE has received the 200 (OK) response for the REGISTER
> request of the only public user identity currently registered with its
> associated set of implicitly registered public user identities (i.e. no
> other is registered), the UE removes the security association
> established between the P-CSCF and the UE. Therefore further SIP
> signalling (e.g. the NOTIFY request containing the deregistration
> event)
> will not reach the UE.
> ---------------------------------------------------------------------------------------------------------------------------------------
>
> So it makes sense to delete the Subscription to reg event package on
> deregistration without waiting for NOTIFY WITH TERMINATED STATE .
>
>
> Please opine.
>
>
> Regards,
> Sunil
>
>
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