Format & purpose of 'Generic IMSI' sent in SRIack from NPLR/MNP-SRF??

[qazmlp]

I would like to know the exact format and the purpose of the 'Generic IMSI' sent in the SRIack message sent from the NPLR/MNP-SRF to the GMSC.

Following is an excerpt from the 3GPP 23.066 document:
----------
The IMSI returned by an NPLR is a generic IMSI, i.e. it is not tied necessarily to the Subscriber. MCC and MNC values in this IMSI shall point to the Subscription Network of the B Subscriber.
----------

I assume the NPDB will contain the MNP data in the following format.
 - <Generic-IMSI-for-recipient-Network-1>
     |
      ---- Ported MSISDN-1(Re-routing number, Portability status)
     |
      ---- Ported MSISDN-2(Re-routing number, Portability status)
 - <Generic-IMSI-for-recipient-Network-2>
   .....

How does the Generic IMSI look like? Is it of MCC+MNC format or the complete IMSI i.e. MCC+MNC+MSIN?  From my pov, the MSIN here does not make sense.

Does anybody have the information on it?

Also, why exactly this parameter is sent, when the recipient network can easily be identified using the MNP re-routing number?

[qazmlp]

Does anybody have some information on 'generic IMSI'?

[RussCrush]

Here is what I know about Generic IMSIs, and why they are used.

The reason for the Generic IMSI is that when the SRI_ACK is generated, the true IMSI may not be known, and the (Mandatory) generic IMSI is sent, along with an RN, to direct the call towards a Call Processor application that will process the call further. This is done when an application Service is used, and prevents exposing subscriber data to the third party. It is also used to prevent multiple dipping of the NPDB. The use of the generic IMSI ensures that the call is directed to the Call processor before the actual dip to the NPDB is made.

The Generic IMSI is usually a combination of the Network element (MCC and MNC) of where the application is located, and the MSISDN itself. Example:

 MSISDN in CDPA is 447870123456. The Generic IMSI would be something like 234209990123456, with the "999"being the ID of the Call Processor application.

 The call would be passed to the network, and presented to the call processor application, which would then query the NPDB for final routing.

Hope that helps!