A packet exchange method, comprising: obtaining, by a first device, a packet by using a Network Convergence Protocol, NCP, layer of the first device, wherein the packet is a packet used for fixed mobile convergence, FMC, multi-connection aggregation or a packet used for FMC multi-connection management; and sending, by the first device, the packet to an NCP layer of a second device by using the NCP layer of the first device, wherein the NCP layer is located at or on top of a data link layer of a user plane, and the NCP layer of the first device and the NCP layer of the second device form a direct data exchange channel between the first device and the second device, and wherein the NCP layer is configured for performing: carrying an internet protocol, IP, packet, wherein transfer performance of the IP packet is ensured by using a transparent transmission mode; carrying a packet sequence number header in FMC multi-connection aggregation to support functions of multi-connection aggregation and splitting; carrying multi-connection management information to implement functions of steering and switching between a plurality of FMC connections; carrying private network awareness information, whereby the core network device senses a status and a service of a private network; carrying private network control information, whereby the core network device controls quality of service, QoS, and a virtual local area network, VLAN, plan of a private network; and supporting NCP layer nesting; and the first device is a terminal and the second device is a core network device, or the first device is a core network device and the second device is a terminal; wherein the private network is a Wireless Fidelity, Wi-Fi, network and/or a Bluetooth network between the terminal and one or more other terminal devices, wherein each of the one or more other terminal devices is connected to the terminal by using Wi-Fi or Bluetooth. obtaining, by a first device, a packet by using a Network Convergence Protocol, NCP, layer of the first device, wherein the packet is a packet used for fixed mobile convergence, FMC, multi-connection aggregation or a packet used for FMC multi-connection management; and sending, by the first device, the packet to an NCP layer of a second device by using the NCP layer of the first device, wherein the NCP layer is located at or on top of a data link layer of a user plane, and the NCP layer of the first device and the NCP layer of the second device form a direct data exchange channel between the first device and the second device, and wherein the NCP layer is configured for performing: carrying an internet protocol, IP, packet, wherein transfer performance of the IP packet is ensured by using a transparent transmission mode; carrying a packet sequence number header in FMC multi-connection aggregation to support functions of multi-connection aggregation and splitting; carrying multi-connection management information to implement functions of steering and switching between a plurality of FMC connections; carrying private network awareness information, whereby the core network device senses a status and a service of a private network; carrying private network control information, whereby the core network device controls quality of service, QoS, and a virtual local area network, VLAN, plan of a private network; and supporting NCP layer nesting; and the first device is a terminal and the second device is a core network device, or the first device is a core network device and the second device is a terminal; wherein the private network is a Wireless Fidelity, Wi-Fi, network and/or a Bluetooth network between the terminal and one or more other terminal devices, wherein each of the one or more other terminal devices is connected to the terminal by using Wi-Fi or Bluetooth.