RFC 3265 section 3.2.2 provides more clarity on the topic concerning 481
and administrative added subscriptions. However it doesn't clearly
indicate what should occur when NOTIFY already contained
subscription-state is terminated or how quickly a similar subscription
can be added back.
RFC 3265 section 3.2.2:
"If a NOTIFY request receives a 481 response, the notifier MUST remove
the corresponding subscription even if such subscription was
installed by non-SUBSCRIBE means (such as an administrative
interface).
If the above behavior were not required, subscribers receiving a
notify for an unknown subscription would need to send an error
status code in response to the NOTIFY and also send a SUBSCRIBE
request to remove the subscription. Since this behavior would
make subscribers available for use as amplifiers in denial of
service attacks, we have instead elected to give the 481 response
special meaning: it is used to indicate that a subscription must
be cancelled under all circumstances."
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