Section: 8.3 International Mobile Subscriber Identity (IMSI)
Content: International Mobile Subscriber Identity (IMSI) is transferred via GTP tunnels. The sending entity copies the value part of the IMSI into the Value field of the IMSI IE. IMSI is defined in 3GPP TS 23.003[ Numbering, addressing and identification ]  [2]. Figure 8.3-1: IMSI Octets 5 to (n+4) represent the IMSI value in international number format as described in ITU-T Rec E.212 [64], encoded as TBCD digits, i.e. digits from 0 through 9 are encoded "0000" to "1001". When there is an odd number of digits, bits 8 to 5 of the last octet are encoded with the filler "1111". The maximum number of digits is 15.