Re-anchoring with SMF re-selection

A method performed in a first Session Management Function, SMF, in a core network of a cellular communications system to perform re-anchoring with SMF re-selection, the method comprising:

• receiving a trigger related to a User Equipment, UE, Protocol Data Unit, PDU, session, wherein the trigger comprises one of an Application Function, AF, request or a Domain Name System, DNS, query from the UE;
• responsive to receiving the trigger, determining, based on the trigger, that a current PDU Session Anchor, PSA, for the UE PDU session is to be relocated, and that relocation requires an SMF re-selection, wherein determining based on the trigger comprises determining that a new UE location is outside a service area of the first SMF, that DNS-triggered or AF-requested Data Network Access Identifier, DNAI, is to be supported with distributed anchor, that the first SMS does not control any local PSA, or that an AF requests a DNAI that is not controlled by the first SMF;
• and
• initiating re-establishment of the UE PDU session, wherein initiating comprises conveying, to an Access and Mobility Management Function, AMF, Edge Computing, EC, dynamic context information relevant for a new UE PDU session;
• wherein the EC dynamic context information comprises one or more of:
• information about a Data Network Access Identifier (DNAI) for a new User Equipment (UE) Protocol Data Unit (PDU) session.

A network node for implementing a first Session Management Function, SMF, for a core network of a cellular communications system where the first SMF is enabled to perform re-anchoring with SMF re-selection, the network node comprising:

• a network interface;
• and
• processing circuitry associated with the network interface, the processing circuitry configured to:
• receive a trigger related to a User Equipment, UE, Protocol Data Unit, PDU, session, wherein the trigger comprises one of an Application Function, AF, request or a Domain Name System, DNS, query from the UE;
• responsive to receiving the trigger, determine, based on the trigger, that a current PDU Session Anchor, PSA, for the UE PDU session is to be relocated, and that relocation requires an SMF re-selection, wherein the processing circuitry is configured to determine based on the trigger by being configured to determine that a new UE location is outside a service area of the first SMF, that DNS-triggered or AF-requested Data Network Access Identifier, DNAI, is to be supported with distributed anchor, that the first SMS does not control any local PSA, or that an AF requests a DNAI that is not controlled by the first SMF;
• and
• initiate re-establishment of the UE PDU session, wherein initiating comprises conveying, to an Access and Mobility Management Function, AMF, Edge Computing, EC, dynamic context information relevant for a new UE PDU session;
• wherein the EC dynamic context information comprises one or more of:
• information about a Data Network Access Identifier (DNAI) for a new User Equipment (UE) Protocol Data Unit (PDU) session;
• one or more traffic filters;
• N6 routing information;
• DNS configuration information;
• Subscribed AF information;
• or
• related local policies.

A method performed in an Access and Mobility Management Function, AMF, in a core network of a cellular communications system to perform re-anchoring with Session Management Function, SMF, re-selection, the method comprising:

• receiving Edge Computing, EC, dynamic context information from a first SMF, the EC dynamic context information comprising information about a Data Network Access Identifier (DNAI) for a new User Equipment (UE) Protocol Data Unit (PDU) session;
• selecting a second SMF for the new UE PDU session for the UE based on the EC dynamic context information, comprising using the DNAI when selecting the second SMF for the new UE PDU Session;
• and
• transmitting the EC dynamic context information to the second SMF.

A network node for implementing an Access and Mobility Management Function, AMF, for a core network of a cellular communications system where the AMF is enabled to perform re-anchoring with Session Management Function, SMF re-selection, the network node comprising:

• a network interface;
• and
• processing circuitry associated with the network interface, the processing circuitry configured to:
• receive Edge Computing, EC, dynamic context information from a first SMF, the EC dynamic context information comprising information about a Data Network Access Identifier (DNAI) for a new User Equipment (UE) Protocol Data Unit (PDU) session;
• select a second SMF for the new UE PDU session for the UE based on the EC dynamic context information, comprising using the DNAI when selecting the second SMF for the new UE PDU Session;
• and
• transmit the EC dynamic context information to the second SMF.

A network node for implementing a second Session Management Function, SMF, for a core network of a cellular communications system where the second SMF is enabled to perform re-anchoring with SMF re-selection, the network node comprising:

• a network interface;
• and
• processing circuitry associated with the network interface, the processing circuitry configured to:
• receive Edge Computing, EC, dynamic context information from an Access and Mobility Management Function, AMF, the EC dynamic context information comprising information about a Data Network Access Identifier (DNAI) for a new User Equipment (UE) Protocol Data Unit (PDU) session;
• and
• establish the new UE PDU Session for the UE based on the EC dynamic context information, comprising selecting a PDU Session Anchor (PSA) for the new UE PDU Session and configuring the PSA for the new PDU Session.