To deal with challenges of wireless broadband technologies, and maintain the leading edge of the 3rd Generation Partnership Project (3GPP) network, the 3GPP has formulated a Long Term Evolution (LTE) plan of a mobile communications network. Under the guidance of the LTE plan, the 3GPP has defined a new mobile communications network architecture, that is, an evolved packet system (EPS) wireless network architecture.
FIG. 1 is a schematic diagram of an EPS wireless network architecture in the prior art. As shown in FIG. 1, when user equipment (UE) accesses an EPS network by using a serving GPRS support node (SGSN), the UE may access a serving gateway (SGW) by using an S4 interface, and then, access a packet data network gateway (PDN-GW or PGW) by using an S5 interface. Functions of main network entities in the EPS network are described as follows:
An evolved universal terrestrial radio access network (E-UTRAN) is a network including multiple evolved NodeBs (eNodeB), and implements a wireless physical layer function, resource scheduling and radio resource management, and a radio access control and mobility management function. The eNodeBs are connected to an SGW by using a user plane interface (S1-U interface), and are configured to transmit user data; and are connected to a mobility management entity (MME) by using a control plane interface (S1-MME interface), and are configured to implement a radio access bearer control function by using an S1 Application Protocol (S1-AP).
The MME is mainly responsible for functions such as mobility management of the UE, session management, encryption and integrity protection of non-access stratum (NAS) signaling, management of a tracking area list (Tracking Area List), and PGW/SGW selection.
An SGW is mainly responsible for data transmission, forwarding, and route switching of the UE, and is used as a local mobility anchor when the UE is handed over between eNodeBs.
A PGW is an entry for an external network to send data to the UE, and is mainly responsible for IP address assignment of the UE, data packet filtering, rate control, charging information generation, and the like.
A policy and charging rules function (PCRF) entity determines a corresponding policy according to a network access limitation of a user, an operator policy, user subscription data, and information about a service that is being performed by the user, and provides the policy to a transmission gateway for execution, to implement policy and charging control.
Operator's IP services (Operator's IP Services) are implemented in the LTE network by using an IP multimedia subsystem (IMS) network. In addition, a packet switched streaming service (PSS) technology is a technology defined by the 3GPP and used to provide a streaming media service to a user. A PSS network architecture mainly includes a mobile terminal and a PSS server on a network side.
Data packets sent and received by the UE are transmitted in the EPS network by using an EPS bearer. For the convenience of description, the EPS bearer may also be referred to as a bearer in the following specification. Each UE may have multiple bearers, and different bearers can satisfy quality of service (QoS) requirements of different services. An eNodeB and an SGW may store information about each bearer, that is, a bearer context. The bearer context includes an SGW tunneling endpoint identifier (TEID) and an eNodeB TEID of each bearer. The SGW TEID is used for an uplink packet sent by the eNodeB to the SGW and the eNodeB TEID is used for a downlink packet sent by the SGW to the eNodeB. The eNodeB implements bearer context synchronization with an MME by using an S1-AP message, and the SGW implements bearer context synchronization with the MME by using a GPRS tunneling protocol-control plane (GTP-C) message, thereby implementing bearer context synchronization between the eNodeB and the SGW.
When receiving an uplink packet sent by the UE, the eNodeB may encapsulate the uplink packet of the UE into a GTP-U packet according to the bearer context. The GTP-U packet includes a GTP-U header, and the GTP-U header includes an SGW TEID. Because different bearers may use different SGW TEIDs, when receiving the GTP-U packet sent by the eNodeB, the SGW may determine, according to the GTP-U header, a bearer to which the GTP-U packet belongs. Similarly, when receiving a downlink packet sent to the UE, the SGW encapsulates the packet of the UE into a GTP-U packet. The GTP-U packet includes a GTP-U header, and the GTP-U header includes an eNodeB TEID. Therefore, when receiving the GTP-U packet sent by the SGW, the eNodeB can determine, according to the GTP-U header, a bearer to which the GTP-U packet belongs.
A mobile edge computing (MEC) platform is a logic network element deployed on the S1-U interface, and is located between the eNodeB and the SGW. The MEC platform mainly includes a traffic bus (traffic bus) and an application (application). The traffic bus is responsible for obtaining a data packet of the UE and forwarding the data packet to a corresponding application. After processing the data packet, the application sends the processed data packet to the traffic bus for routing.
Multiple types of applications may be installed on the MEC platform, to improve service experience of the user. The application on the MEC platform may capture an uplink packet sent by the UE, and modify, check, and forward the uplink packet of the UE, or may directly reply to the uplink packet sent by the UE. For example, a video buffering application may be installed on the MEC platform. When the UE sends a video request packet, the video buffering application processes the video request packet of the UE. If the video buffering application does not include a video requested by the UE, the video buffering application may forward the video request packet of the user to the SGW, or if the video buffering application stores a video requested by the UE, the video buffering application directly sends a video reply packet to the UE.
The applicants find that when the MEC platform directly replies to the uplink packet of the UE, the MEC platform cannot correctly perform GTP-U encapsulation, and consequently, cannot send a reply packet corresponding to the uplink packet of the UE to the eNodeB.