Section: 6.1.2.3 Network slice constraints
Content: The 5G system shall support a mechanism to prevent a UE from trying to access a radio resource dedicated to a specific private slice for any purpose other than that authorized by the associated third-party. NOTE 1: UEs that are not authorized to access a specific private slice will not be able to access it for emergency calls if the private slice does not support emergency services. The 5G system shall support a mechanism to configure a specific geographic area in which a network slice is accessible, i.e. a UE shall be within the geographical area in order to access the network slice. The 5G system shall support a mechanism to limit a UE to only receiving service from an authorized slice. For a UE authorized to access to multiple network slices of one operator which cannot be simultaneously used by the UE (e.g. due to radio frequency restrictions), the 5G system shall minimize service interruption time when the UE changes the access from one network slice to another network slice. (e.g. based on changes of active applications). For traffic pertaining to a network slice offered via a relay node, 5G system shall use only radio resources (e.g. frequency band) allowed for the network slice. NOTE 2: Allowed radio resources (e.g., frequency band) may be different for direct network connections (between UE and NG-RAN) than for backhaul connections (between the relay node and the NG-RAN). The 5G system shall support a mechanism to prevent a UE from registering with a network slice when the maximum number of UEs for that slice are registered. The 5G system shall support a mechanism to prevent a UE from establishing a new data session within a network slice when the maximum number of data sessions for that slice are established. NOTE 3: Based on national/regional regulations and operator policy, exemptions can be provided for UEs configured for priority services (e.g., MPS) and for priority service sessions.