vpn active RATs,

Make-before-break with dual radio. Assuming suffi-cient access coverage areas overlap between thenew and the currently active RATs, a timely handover trigger to the new RAT allows performing ina make-before-break fashion network entry andthe establishment of IP connectivity over the newRAT (using the second radio), while maintaininga quality application session over the old RAT (viathe active radio). The IP mobility anchor switchesthe data path tunnel from the old RAN to the newRAN after processing the mobility binding registration message from the new RAN (e.g., the corresponding GTP message for LTE, or thePMIP/CMIP message for non-3GPP technologies).This reduces the possibility of a potential trafficinterruption gap up to the order of a mobility registration roundtrip delay between the UE and themobility anchor. Further improvements are possible using bicasting methods during handover(e.g., MIP-defined simultaneous bindings with DLbicasting) and by applying intelligent handover buffering algorithms, controlled and timed by theCM in juxtaposition with the make-before-breakprocedures.• Intelligent buffering during handover. When the UEperforms a make-before-break network entry andthe mobility anchor switches the data path tunnels from the old RAN to the new RAN, transientUL packets over the old RAN can be lost, andtransient DL packets over the old RAN can arriveout of order, especially on handover from 3G toLTE, where the new leg is faster. Proper bufferingschemes in the UL and DL directions allow suchpacket loss and reordering to be addressed.Specialized per flow buffering may be necessaryfor handovers with QoS. Additional DL datastream synchronization algorithms may beneeded in the case of DL bicasting.