msisdn  IE 

This parameter refers to one of the ISDN numbers assigned to a mobile subscriber in accordance with CCITT Recommendation E.213. In an IP Multimedia Core Network, if no MSISDN is available, the HLR shall populate this parameter with the dummy MSISDN value (see clause 3 of 3GPP TS 23.003).

Reference: TS 29.002-f30   View