RFC 3921:Extensible Messaging and Presence Protoco...
RFC-Ref

subscriber


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... 2778 [IMP-MODEL], these entities are subscribers). This broadcast model does not apply to subscription-related presence stanzas ...
... unavailable presence MUST be broadcasted by the server to all subscribers. ...


... subscription lasts across sessions; indeed, it lasts until the subscriber unsubscribes or the subscribee cancels the previously-granted subscription. Subscriptions are managed within ...



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