Through which two procedures does a direct tunnel session change to a two-tunnel session?
(Choose two.)
A.
Iu-release request procedure initiated by RNC
B.
GTPU-error indication by the RNC to the GGSN
C.
UE-initiated secondary PDP context activation
D.
successful GGSN-initiated PDP modification procedure
E.
successful UE-initiated PDP modification procedure
F.
periodic RAU procedure triggered by the UE