According to the UML schema on 5.1, the "confirm the address before the subscription..." is not clear :
We suppose this part is used to verifiy/confirm that the url callback by the subscriber is valid.
The notify call from NE to subscriber is not documented. We suppose is the "confirm" call ?
We suppose that the subscribe_CB(token) arrow is from PE to subcriber OR we suppose that there are a missing subscribe_CB, a function callback provide by the NE for the subscriber if the arrow stay in the same direction.
According to the UML schema on 5.1, the "confirm the address before the subscription..." is not clear :
We suppose this part is used to verifiy/confirm that the url callback by the subscriber is valid.