5G/NR - Network Architecture - SMF       







SMF stands for Session Management Function. Simply put, it collects all the informations related to PDU session management from various network components (e.g, UPF, PCF, UDM) and controls / orchastrates those network components based on request from AMF.


Followings are the name of each network component.

    AMF     Access and Mobility Management Function ==> Equivalent to MME in 4G

    AUSF    Authentication Server Function

    DN       Data Network

    NEF      Network Exposure Function

    NRF      Network Repository Function

    NSSF    Network Slice Selection Function

    PCF      Policy Control Function ==> Equivalent to PCRF in 5G

    (R)AN   (Radio) Access Network

    SMF     Session Management Function

    UDM     Unified Data Management ==> Equivalent to HSS in 4G

    UPF      User Plane Function ==> Equivalent to PGW in 4G

    SMSF   SMS Function

    SEAF    SEcurity Anchor Function ==> part of AMF function

    ARPF    Authentication credential Repository and Processing Function

    SIDF    Subscription Identifier De-concealing Function




SMF Functionality


Based on 23.501-6.2.2, the functionality of AMF is descrbed as follows.

  • enforcement of the policy decisions related to service data flow detection
  • authorized QoS
  • charging
  • gating
  • traffic usage reporting
  • packet routing and forwarding
  • traffic steering
  • PDU Session Establishement (23.502-4.3.2)
    • a UE initiated PDU Session Establishment procedure.
    • a UE initiated PDU Session handover between 3GPP and non-3GPP.
    • a UE initiated PDU Session handover from EPS to 5GS.
    • a Network triggered PDU Session Establishment procedure.




UE-Initiated PDU Sesstion Establishment Process



< 23.502 - Figure UE-requested PDU Session Establishment for non-roaming and roaming with local breakout >





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