Printer (e.g., the Subscription Object is canceled when the associated Job completes and is no longer in the Job Retention or Job History phase; see the "ippget-event-life (integer(15:MAX))" attribute discussion in section 8.1).
However, the Printer MAY decide to terminate Event Wait Mode at any time, including in the first response. In this case, the Printer MUST return the "notify-get-interval" operation attribute. This attribute indicates that the Printer wishes to leave Event Wait Mode and the number of seconds in the future that the Notification Recipient SHOULD try the Get-Notifications operation again. The Notification Recipient MUST accept this response and MUST disconnect. If the Notification Recipient does not disconnect, the Printer SHOULD do so.
From the Notification Recipient's view, the response appears as an initial burst of data, which includes the Operation Attributes Group and one Event Notification Attributes Group per Event Notification that the Printer is holding. After the initial burst of data, if the Notification Recipient has selected the Event Wait Mode option to wait for additional Event Notifications, the Notification Recipient receives occasional Event Notification Attribute Groups. Proxy servers may delay some Event Notifications or cause time-outs to occur. The client MUST be prepared to perform the Get-Notifications operation again when time-outs occur.
Each attribute is encoded by using the IPP rules for encoding attributes [RFC2910] and MAY be encoded in any order. Note: the Get-Jobs response in [RFC2911] acts as a model for encoding multiple groups of attributes. See section 11 for the encoding and transport rules.
The following groups of attributes are part of the Get-Notifications
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