Techniques are provided to inform a mobile packet core of the access network/radio access technology (AN/RAT) change with the use of in-band signaling along the user plane and hence reduce signaling between radio access network and mobile packet core network. A new extension header content is defined to signal the AN/RAT change information, Cell Group changes and acknowledging the same. Further still, a method is provided to handle AN change notification for split bearer scenarios by introducing a split bearer flag for the mobile packet core to be notified of the predominant access type serving the subscriber data session in 5G Non-Stand Alone (NSA) Option-3, Option-3A and Option-3X, so that static or dynamic configurations can be applied by the mobile core network accordingly.