I was referring the rfc4666 for M3UA and have few concerns regarding the DUPU SSNM message. The specification says that a DUPU indicates the unavailability of a certain user part.
If I may quote "The DUPU message is used by an SGP to inform concerned ASPs that a remote peer MTP3-User Part (e.g., ISUP or SCCP) at an SS7 node is unavailable"
I have two questions.
1. How these concerned ASPs are identified. Is it upon receiving a MTP-Transfer for a particular user part (say SCCP) or can it be sent periodically for a given ASP ?
2. I could not find any SSNM message that indicates a User Parts Availability. Am I wrong here to expect such a message and if so how come a concerned ASP know if a certain User Part is available at a given point code.
It would be an immense help if anyone could clarify the aforementioned concerns.