Abstract: A service continuity implementation method, a related device, and a system, where a mobility management device may select a 5G gateway for a 5G user equipment handed over to a 4G network, and establish a session with the 5G gateway. The 5G gateway may send a 5G-related parameter to the user equipment in advance. Therefore, after the user equipment moves from the 4G network to a 5G network, service continuity is maintained, that is, a service in the 4G network continues to be maintained in the 5G network.

Abstract: A communication method is applied to a scenario in which a terminal moves from a first preset area of a first network to a second preset area of a second network. The method includes that a first core network device in the first network determines that Evolved Packet System (EPS) fallback of the terminal is triggered, and sends first information to a second core network device in the second network. The first information includes a first identifier or first indication information. The first identifier identifies a first dedicated bearer corresponding to the terminal. The first dedicated bearer includes a voice dedicated bearer or a video dedicated bearer. The first indication information indicates that the terminal falls back to the second network using an EPS fallback procedure.

Abstract: A communication method and apparatus, where the method includes: A first mobility management network element in a first network obtains information about N intermediate session management network elements that are capable of serving a terminal in the first network, and determines that a combined intermediate session management network element (which is capable of providing session management in the first network and in a second network) in the N intermediate session management network elements is a first intermediate session management network element corresponding to a first session of the terminal in the first network, such that overall communication efficiency of the network is improved. For example, network address resources are reduced to simplify network planning and deployment complexity, a quantity of nodes in the network is reduced to simplify network operation and maintenance workload, and signaling between the nodes in the network is reduced to reduce network service load.

Abstract: A service continuity implementation method, a related device, and a system, where when a user equipment is attached to a 2/3G network, a serving node device determines that the user equipment has a 5G capability or a user corresponding to the user equipment is a 5G user. Then, the serving node device selects a 5G gateway for the user equipment, and establishes a session with the 5G gateway. In this way, when the user equipment subsequently moves to a 5G network, the same 5G gateway serves the user equipment, and an address of the user may remain unchanged when the user equipment moves from the 2/3G network to the 5G network, thereby implementing service continuity of the user.

Abstract: A service continuity implementation method, a related device, and a system, where a mobility management device may select a 5G gateway for a 5G user equipment handed over to a 4G network, and establish a session with the 5G gateway. The 5G gateway may send a 5G-related parameter to the user equipment in advance. Therefore, after the user equipment moves from the 4G network to a 5G network, service continuity is maintained, that is, a service in the 4G network continues to be maintained in the 5G network.