An apparatus implementing a first network function and comprising a processor and a memory, the memory storing instructions that, when executed by the processor, cause the apparatus to perform operations comprising: receiving, by the first network function from a wireless transmit / receive unit, WTRU, a first message, wherein the first message is indicative of an operation requested to be performed with a network slice, the operation comprising at least one of a slice registration or a protocol data unit, PDU, session establishment; sending, by the first network function to a second network function, a second message, wherein the second message is indicative of a request for a determination of whether a threshold related to the operation is met; receiving, by the first network function from the second network function, a first response indicative of the determination of whether the threshold is met; and sending, by the first network function to the WTRU, a second response comprising an indication of whether the operation is allowed; wherein: the threshold is associated with at least one of a maximum number of WTRUs that can be registered with the network slice or a maximum number of PDU sessions that can be established with the network slice; when the operation comprises a slice registration, the second response comprises an indication that the operation is rejected as a result of the network slice having attained the maximum number of registered WTRUs; and when the operation comprises a PDU Session Establishment, the second response comprises an indication that the operation is rejected as a result of the network slice having attained the maximum number of PDU Sessions. receiving, by the first network function from a wireless transmit / receive unit, WTRU, a first message, wherein the first message is indicative of an operation requested to be performed with a network slice, the operation comprising at least one of a slice registration or a protocol data unit, PDU, session establishment; sending, by the first network function to a second network function, a second message, wherein the second message is indicative of a request for a determination of whether a threshold related to the operation is met; receiving, by the first network function from the second network function, a first response indicative of the determination of whether the threshold is met; and sending, by the first network function to the WTRU, a second response comprising an indication of whether the operation is allowed; wherein: the threshold is associated with at least one of a maximum number of WTRUs that can be registered with the network slice or a maximum number of PDU sessions that can be established with the network slice; when the operation comprises a slice registration, the second response comprises an indication that the operation is rejected as a result of the network slice having attained the maximum number of registered WTRUs; and when the operation comprises a PDU Session Establishment, the second response comprises an indication that the operation is rejected as a result of the network slice having attained the maximum number of PDU Sessions. the threshold is associated with at least one of a maximum number of WTRUs that can be registered with the network slice or a maximum number of PDU sessions that can be established with the network slice; when the operation comprises a slice registration, the second response comprises an indication that the operation is rejected as a result of the network slice having attained the maximum number of registered WTRUs; and when the operation comprises a PDU Session Establishment, the second response comprises an indication that the operation is rejected as a result of the network slice having attained the maximum number of PDU Sessions.