If an incoming SETUP message is offered with addressing information (i.e. either DDI or sub-addressing or the appropriate part of the called party number), the following actions will occur:
a) If a number or sub-address is assigned to a user, then the information in a Called party number or Called party subaddress information element of the incoming call shall be checked by the user against the corresponding part of the number assigned to the user or the user's own sub-address. In case of a mismatch, the user shall ignore the call. In the case of match, the compatibility checking described in B.3.2 through B.3.3 will follow.
b) If a user has no assigned number or sub-address., then the Called party number and Called party subaddress information element shall be ignored. Then, compatibility checking described in B.3.2 and B.3.3 will follow.
NOTES
1. According to user's requirements,compatibility checking can be performed in various ways from the viewpoint of execution order and information to be checked, e.g. first assigned number/sub-address and then compatibility or vice versa.
2. If an incoming call, offered with addressing information, is always to be awarded to the addressed user, all users connected to the same passive bus should have an assigned number or sub-address.