Method, Apparatus, and System for Establishing Session

Abstract

Embodiments of the present invention relate to the field of communications technologies, and in particular, to a method, an apparatus, and a system for establishing a session, to resolve a problem in the prior art that efficiency is low because an AMF entity needs to reselect an SMF entity when forwarding a first message. The method includes: receiving, by a mobility management function AMF entity, a first message sent by user equipment UE, where the first message carries identifier information, the identifier information is used to instruct the AMF entity to send the first message to a session management function SMF entity, and the first message is used to instruct the SMF entity to re-establish a session with the UE based on the identifier information by using a first user plane function UPF entity; and sending, by the AMF entity based on the identifier information, the first message to the SMF entity associated with the identifier information. The embodiments of the present invention are applied to a system for establishing a session.

1 . An apparatus, comprising:
 at least one processor; and   a memory coupled to the at least one processor and configured to store programming instructions that, when executed by the at least one processor, cause the apparatus to:
 establish a first protocol data unit (PDU) session by communicating with a session management function (SMF) entity; 
 receive a first message indicating a PDU session re-establishment from an access and mobility management function (AMF) entity, wherein the first message comprises a first PDU session identifier (ID) of the first PDU session; 
 make a determination that a session and service continuity (SSC) mode for the first PDU session is a mode in which a network allows the apparatus to establish a new PDU session before an old PDU session is released, wherein the old PDU session and the new PDU session have a same data network (DN); 
 transmit, in response to the determination, a second message comprising a PDU session establishment request and the first PDU session ID; and 
 establish a second PDU session by communicating with the SMF entity. 
   
     
     
         2 . The apparatus of  claim 1 , wherein the first message comprises a PDU session release time of the first PDU session. 
     
     
         3 . The apparatus of  claim 2 , wherein the first message indicates that the apparatus is to release the first PDU session within the PDU session release time. 
     
     
         4 . The apparatus of  claim 1 , wherein the second message comprises a second PDU session ID of the second PDU session. 
     
     
         5 . The apparatus of  claim 1 , wherein the first message comprises a cause value indicating the PDU session re-establishment. 
     
     
         6 . The apparatus of  claim 1 , wherein the first PDU session is served by a second user plane function (UPF), and wherein the second PDU session is served by a first UPF. 
     
     
         7 . The apparatus of  claim 1 , wherein the AMF entity stores an association between the first PDU session ID and an SMF ID associated with the SMF entity. 
     
     
         8 . The apparatus of  claim 1 , wherein when executed by the at least one processor, the programming instructions further cause the apparatus to release the first PDU session. 
     
     
         9 . The apparatus of  claim 1 , wherein the first PDU session ID indicates that the AMF entity selected the SMF entity for establishing the second PDU session. 
     
     
         10 . The apparatus of  claim 1 , wherein the first PDU session and the second PDU session have a same DN. 
     
     
         11 . A method, comprising:
 establishing a first protocol data unit (PDU) session by communicating with a session management function (SMF) entity;   receiving a first message indicating a PDU session re-establishment from an access and mobility management function (AMF) entity, wherein the first message comprises a first PDU session identifier (ID) of the first PDU session;   making a determination that a session and service continuity (SSC) mode for the first PDU session is a mode in which a network allows establishing a new PDU session before releasing an old PDU session, wherein the old PDU session and the new PDU session have a same data network (DN);   transmitting, in response to the determination, a second message comprising a PDU session establishment request and the first PDU session ID; and   establishing a second PDU session by communicating with the SMF entity.   
     
     
         12 . The method of  claim 11 , wherein the first message comprises a PDU session release time of the first PDU session. 
     
     
         13 . The method of  claim 11 , wherein the second message comprises a second PDU session ID of the second PDU session. 
     
     
         14 . The method of  claim 11 , wherein the first message comprises a cause value indicating the PDU session re-establishment. 
     
     
         15 . The method of  claim 11 , wherein the first PDU session is served by a second user plane function (UPF), and wherein the second PDU session is served by a first UPF. 
     
     
         16 . The method of  claim 11 , wherein the AMF entity stores an association between the first PDU session ID and an SMF ID associated with the SMF entity. 
     
     
         17 . The method of  claim 11 , further comprising releasing the first PDU session. 
     
     
         18 . The method of  claim 11 , wherein the first PDU session ID indicates that the AMF entity selected the SMF entity for establishing the second PDU session. 
     
     
         19 . The method of  claim 11 , wherein the first PDU session and the second PDU session have a same DN. 
     
     
         20 . A computer program product comprising instructions stored on a non-transitory computer-readable medium that, when executed by a processor, cause an apparatus to:
 establish a first protocol data unit (PDU) session by communicating with a session management function (SMF) entity;   receive a first message indicating a PDU session re-establishment from an access and mobility management function (AMF) entity, wherein the first message comprises a first PDU session identifier (ID) of the first PDU session;   make a determination that a session and service continuity (SSC) mode for the first PDU session is a mode in which a network allows the apparatus to establish a new PDU session before an old PDU session is released, wherein the old PDU session and the new PDU session have a same data network (DN);   transmit, in response to the determination, a second message comprising a PDU session establishment request and the first PDU session ID; and   establish a second PDU session by communicating with the SMF entity.