apability to support independent measurements for different frequency ranges. If per-UE gap is used, the decision on the gap configuration is taken by the MN. If per-FR gap is used, in EN-DC and NGEN-DC, the MN decides the gap configuration for FR1, while the SN decides the gap configuration for FR2; in NE-DC and NR-DC, the MN decides both the FR1 and FR2 gap configurations. 4.3.4.1.4 Security-Related Aspects A UE can be configured with MR-DC only after security activation in the MN. The security key used by the UE depends on whether the bearers are terminated in the MN or in the SN. For bearers terminated in the MN, the UE is configured to use the master security key. For bearers terminated in the SN, the UE is configured to use the secondary security key, which is derived from the master security key being used with the MN. In 5G, integrity protection, which was only applied to SRBs in 4G, can be also used for user-plane data on a PDU session basis. This is also applicable to MR-DC, where all DRBs belonging to the same PDU session have the same user-plane integrity protection config- uration (i.e. on or off), no matter whether a PDU session is served by both MN and SN in MR-DC with 5GC. Considering that in NR an intra-gNB handover does not necessarily require a security key change (i.e. in cases where gNB-CU is not changed), whenever the MN is a gNB (i.e. in 4 NG-RAN Architecture NE-DC and NR-DC), a PCell change without a security key change does not require a sec- ondary security key change. Similarly, whenever the SN is a gNB (i.e. in EN-DC, NGEN-DC, and NR-DC), for a Primary Secondary Cell Group Cell (PSCell) change that does not require a corresponding master security key change (e.g. when there is no simultaneous PCell han- dover in EN-DC and NGEN-DC), a secondary security key refresh is not required if the PDCP termination point of the SN is not changed. On the other hand, in NE-DC, a PSCell change always requires a secondary security key change. 4.3.4.2 User Plane Both MN and SN network nodes have user-p