Interfaces : Gn : Interface between SGSN and GGSN Gp : Interface between SGSN and GGSN in visitor PLMN Gr : Interface between SGSN and HLR Gs : Interface between SGSN and MSC
Gb : Interface between SGSN and BSS Gd : Interface between SGSN and SMS-GMSC/SGSN Gi : Interface between GGSN and PDN Gf : Interface between SGSN and EIR