Re: [sipcore] Comments on draft-ietf-sipcore-sip-push-04

[[e-mail] (Dale R. Worley)]

Roman Shpount <[e-mail]> writes:
> I have suggested in another thread that proxy should return minimum
> interval after which it expects to trigger a push notification for
> registration (something like pn-refresh SIP URL parameter in Contact
> registration response). Based on this SIP UA can try to schedule the
> re-registration. If SIP UA successfully re-register before proxy triggers
> push notification, then push notification will be avoided. If UA does not
> re-register either due to mobile OS limitations or OS scheduling failure,
> proxy will trigger the push notification to wake the client and trigger the
> re-registration.

It seems to me that an effective way to parameterize this (possibly in
an extension, as Christer discusses), is a parameter that specifies how
long before registration expiration the proxy/registrar should
push-notify the UA.  This approach has some advantages:

The UA is likely to know the time delays involved (the PN service's
delays, the UA's device's wake-up delays, the internal delays in the
UA).

If the registrar allows less time for the registration than the UA has
requested, the time of the PN is moved to compensate.

Some exceptional value of the parameter can indicate "PN for
reregistration is not needed".

Since the PN is triggered by the near-expiration of the registration, if
the registration is renewed before that point for any reason, the
scheduled PN for reregistration is automatically postponed.

Dale