To enable network load distribution when virtualizing a network function.

A pass transistor network (362) is provided for implementing the pass network function in accordance with this decomposition.

A UE can selectively access a PLMN according to the network function activating states of different PLMNs; therefore, the network performance and utilization of network resources are improved.

The access terminal may be configured to change the session state at a first network function and send a message to a second network function to indicate that the session state has been changed.

This data-model incorporates a set of logical-nodes encapsulating network function and/or network devices, and are arranged in a hierarchy for centralised control and/or monitoring.

By using the invention, the network configuration information can be verified effectively, the burden of network managers can be lightened and carrying out the network service and function normally can be ensured.