Product Description

The Cisco Session Management Function (SMF) is one of the Control Plane Network Functions (NF) of the 5G core network (5GC). The SMF is responsible for the session management with the supported individual functions on a per-session basis.

A single instance of SMF can support some or all the functionality of the SMF. As specified in 3GPP TS 23.501, the SMF supports the following functionality:

  • Handles session management. For example, session establishment, modification and release, including the tunnel between the User Plane Function (UPF) and the access network (AN).

  • Handles user element (UE) IP address allocation and management, which includes an optional authorization.

  • Performs Dynamic Host Configuration Protocol for IPv4 (DHCPv4) and DHCPv6 functions, both as server and client.

  • Performs Allocation and Retention Priority (ARP) proxying and IPv6 Neighbor Solicitation Proxying functionality for the Ethernet PDUs. The SMF communicates with the ARP and the IPv6 Neighbor Solicitation Request by providing the MAC address. This address corresponds to the IP address that exists in the request.

  • Selects and controls the UPF for the Ethernet PDU sessions. The UP function includes controlling the UPF to proxy ARP or IPv6 Neighbor Discovery, and forwarding all ARP or IPv6 Neighbor Solicitation traffic to the SMF.

  • Configures Traffic Steering at the UPF to route traffic to the corresponding Data Network (DN).

  • Terminates interfaces toward the Policy Control Function (PCF).

  • Handles the Lawful Intercept (LI) for Session Manager (SM) events and interface to the LI system.

  • Controls and synchronizes the charging data collection at the UPF.

  • Terminates the SM parts of Non-Access-Stratum (NAS) messages.

  • Routes packets and ensures the delivery of information through the Downlink Data Notification (DDN).

  • Initiates the AN-specific SM information that is sent through the Access and Mobility Management Function (AMF) to AN over the N2 interface.

  • Determines the session and service continuity (SSC) mode of a session.

  • Provides the following roaming functionality:

    • Manages the local enforcement to apply Quality of Service (QoS) SLAs (VPLMN).

    • Collects charging data and supports the charging interfaces.

    • Supports communication with the external DN. The communication is for the transport of signaling for the PDU session authorization or authentication by an external DN.

The SMF also provides support for an enterprise mobile virtual network operator (MVNO) model, which enables a mobile network operator (MNO) to perform secondary authentication for the leased MVNO subscribers. Additionally, the SMF supports other MVNO features, but is not limited to, RADIUS Client, vDNN, and so on.