A network slice technology divides a physical network into a plurality of network slice instances. In each network slice instance, a network function is customized and tailored and a corresponding network function is orchestrated and managed based on a service scenario requirement. A network and management are customized, so that a customized requirement of each service of a consumer and an enterprise is better satisfied, and a plurality of services are implemented relatively independently while the services share one broadband network infrastructure. The customized requirement includes coverage, duration, a capacity, a speed, a delay, reliability, security, availability, and the like. Each network slice instance may be considered as a core network architecture. A network slice instance may be applied to mobile broadband, multimedia, massive machine type communication, and critical machine type communication.
In the prior art, in a same public land mobile network (PLMN), a user equipment (UE) may access only one network slice instance, or may access a plurality of network slice instances and simultaneously use different services provided by the plurality of network slice instances. In a home routed roaming scenario, when UE roams to a visited public land mobile network (VPLMN), a service requested by the UE needs to be jointly provided by the VPLMN and a home public land mobile network (HPLMN). In a scenario in which a network slice technology is supported, the service requested by the UE needs to be jointly provided by two slice instances of the VPLMN and the HPLMN.
In the scenario in which the UE roams and the network slice technology is supported, a network slice selection method needs to be provided, so that the two PLMNs can select proper network slice instances to provide the service to the UE, and user experience of the roaming UE is ensured in the scenario in which the network slice technology is supported.