Dear AMIT No Need to confuse,
GSM-MAP Belongs to ETSI.
IS41-MAP Belongs to ANSI.
ETSI-Handles GSM+WCDMA Related Issues and Makes Related Standards.
ANSI-Handles CDMA ( ONE,2000..ETC..ETC) Related Issues and Makes Related Standards.
ITU-T – ETSI & ANSI Are members.
ITU-T Mainly Concerns abt WORLD INTERCONNECTIVITY through any STANDARDS approved by it.
Thatswhy ISUP Comes Under ITU-T.
But still ISUP Has different EUROPE/AMERICAN/RUSSIAN Versions.
But during interconnection they will use common Standard specified by ITU.