Method and apparatus for reassignment of access and mobility management function in communication system

An access and mobility management function (AMF) entity for performing AMF reallocation in a communication system, the AMF entity comprising:

• a transceiver configured to communicate with another network entity;
• and
• a controller operatively coupled with the transceiver, wherein the controller is configured to:
• receive a registration request message from a user equipment (UE),
• obtain a first security context for the UE from a previous AMF,
• transmit, to a network slice selection function (NSSF), a first request message including at least one of a first parameter requesting a public key of an AMF to be reallocated or a second parameter requesting a token related to the AMF to be reallocated,
• receive, from the NSSF, a first response message including information indicating a target AMF set and at least one of a public key of the target AMF set or the token,
• generate a security context container including a second security context for a target AMF based on the first security context,
• encrypt the security context container using the public key,
• transmit the encrypted security context container and at least one of additional information related to encryption of the security context container and the token to the target AMF through a radio access network related to the UE,
• receive a first registration request message from a first UE,
• obtain a third security context for the first UE from a first previous AMF,
• transmit, to the NSSF, a third request message including a third parameter requesting a public key of an AMF to be reallocated,
• receive, from the NSSF, a third response message including information indicating a first target AMF set,
• transmit, to a network repository function (NRF), a fourth request message including a fourth parameter requesting a token related to the AMF to be reallocated,
• receive, from the NRF, a fourth response message including a token related to the first target AMF set,
• generate a first security context container including a fourth security context for a first target AMF based on the third security context,
• encrypt the first security context container using the public key, and
• transmit the encrypted first security context container and at least one of additional information related to encryption of the first security context container and the token to the first target AMF through a first radio access network related to the first UE.