X
    X1_1ps Interface between ADMF and SGSN for all LI administrative messaging ADMF和SGSN間的接口
    X2_1ps、X_2ps Interface between the SGSN and DF2P for delivery of IRI SGSN和DF2P間的接口
    X3_1ps、X_2ps Interface between the SGSN and DF3P for delivery of IDP SGSN和DF3P間的接口