Re: [sipcore] About SUBSCRIBE method's performance and Out-of-Dialog notification suggestion:

["Worley, Dale R (Dale)" <[e-mail]>]

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From: [e-mail] [[e-mail]] On Behalf Of [e-mail] [[e-mail]]

we can make a new type of subscription which would tear down the dialog after the SUBSCRIBE(and the first NOTIFY), while send the subsequent notification out-of-dialog.
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I do not see that much saving could be obtained using the new method.  The notifier would still need to maintain knowledge of the pseudo-subscription, as it needs to know that it must send NOTIFYs.  The subscriber would still need to maintain knowledge of the pseudo-subscription, as it needs to be able to interpret the received NOTIFYs, and it needs to refresh the pseudo-subscription.

The only savings that I can identify are that if the intermediate elements maintain state regarding subscription dialogs.  The simple solution to such overhead is for the intermediate elements *to not maintain state regarding subscription dialogs*, either by being proper proxies (and thus not maintaining state regarding *any* dialog), or by not Record-Routing themselves during the creation of subscription dialogs (and thus not needing to retain state regarding subscription dialogs).

In either method, the notifier would need to know a URI that routes directly to the subscriber.  In a subscription with no Record-Routes, it would of necessity be the Contact URI in the SUBSCRIBE.  In the new method, it could be defined in another way, but the SUBSCRIBE Contact URI seems to be sufficient.  In either method, the best solution seems to be for the subscriber to have a GRUU to use as its Contact URI.

Dale