gNB_out : (gNB, B)(GTP: TEID T)(A,Z)          -> Interface N3
                                                 unchanged IPv4/GTP
SRGW_out: (SRGW, S1)(U2::1, C1; SL=2)(A,Z)    -> H.M.GTP4.D function
S1_out  : (SRGW, C1)(U2::1, C1; SL=1)(A,Z)
C1_out  : (SRGW, U2::1) (A,Z)                 -> PSP
UPF2_out: (A,Z)                               -> End.DT4 or End.DT6