5G-NR Network Function

5G-NR Network Function


The 5G System architecture consists of the following network functions (NF).

Service-based interfaces: This Service based interface is connected to each interface.

The 5G System Architecture contains the following service-based interfaces:

SBI Interface 
Namf   Service-based interface exhibited by AMF
Nsmf   Service-based interface exhibited by SMF
Nnef   Service-based interface exhibited by NEF
Npcf   Service-based interface exhibited by PCF
Nudm   Service-based interface exhibited by UDM
Naf   Service-based interface exhibited by AF
Nnrf   Service-based interface exhibited by NRF
Nnssf   Service-based interface exhibited by NSSF
Nausf   Service-based interface exhibited by AUSF
Nudr   Service-based interface exhibited by UDR
Nudsf   Service-based interface exhibited by UDSF
N5g-eir    Service-based interface exhibited by 5G-EIR
Nnwdaf   Service-based interface exhibited by NWDAF
Ni-nef        Service-based interface exhibited by I-NEF
Nchf        Service-based interface exhibited by CHF
Nucmf        Service-based interface exhibited by UCMF

Reference points

The 5G System Architecture contains the following reference points:

The 5G system reference Point interface us a set if Point to point interfaces which inter connect those Network Elements.

  • N1:        Reference point between the UE and the AMF.
  • N2:        Reference point between the (R)AN and the AMF.
  • N3:        Reference point between the (R)AN and the UPF.
  • N4:        Reference point between the SMF and the UPF.
  • N6:        Reference point between the UPF and a Data Network.
  • NOTE 1:        The traffic forwarding details of N6 between a UPF acting as an uplink classifier and a local data network are not specified in this Release of the specification.
  • N9:        Reference point between two UPFs.
  • The following reference points show the interactions that exist between the NF services in the NFs. These reference points are realized by corresponding NF service-based interfaces and by specifying the identified consumer and producer NF service as well as their interaction in order to realize a particular system procedure.
  • N5:        Reference point between the PCF and an AF.
  • N7:        Reference point between the SMF and the PCF.
  • N8:        Reference point between the UDM and the AMF.
  • N10:        Reference point between the UDM and the SMF.
  • N11:        Reference point between the AMF and the SMF.
  • N12:        Reference point between AMF and AUSF.
  • N13:        Reference point between the UDM and Authentication Server function the AUSF.
  • N14:        Reference point between two AMFs.
  • N15:        Reference point between the PCF and the AMF in the case of non-roaming scenario, PCF in the visited network and AMF in the case of roaming scenario.
  • N16:        Reference point between two SMFs, (in roaming case between SMF in the visited network and the SMF in the home network).
  • N16a:        Reference point between SMF and I-SMF.
  • N17:        Reference point between AMF and 5G-EIR.
  • N18:        Reference point between any NF and UDSF.
  • N19:        Reference point between two PSA UPFs for 5G LAN-type service.
  • N22:        Reference point between AMF and NSSF.
  • N23:        Reference point between PCF and NWDAF.
  • N24:        Reference point between the PCF in the visited network and the PCF in the home network.
  • N27:        Reference point between NRF in the visited network and the NRF in the home network.
  • N28:        Reference point between PCF and CHF.
  • N29:        Reference point between NEF and SMF.
  • N29i:        Reference point between I-NEF and SMF in the VPLMN.
  • N30:        Reference point between PCF and NEF.
  • NOTE 2:        The functionality of N28 and N29 and N30 reference points are defined in TS 23.503 [45].
  • N31:        Reference point between the NSSF in the visited network and the NSSF in the home network.
  • NOTE 3: in some cases, a couple of NFs may need to be associated with each other to serve a UE.
  • In addition to the reference points above, there are interfaces/reference point(s) between SMF and the CHF. The reference point(s) are not depicted in the architecture illustrations in this specification.
  • NOTE 4:        The functionality of these interface/reference points are defined in TS 32.240 [41].
  • N32:        Reference point between SEPP in the visited network and the SEPP in the home network.
  • NOTE 5:        The functionality of N32 reference point is defined in TS 33.501 [29].
  • N33:        Reference point between NEF and AF.
  • N34:        Reference point between NSSF and NWDAF.
  • N35:        Reference point between UDM and UDR.
  • N36:        Reference point between PCF and UDR.
  • N37:        Reference point between NEF and UDR.
  • N38:        Reference point between I-SMFs.
  • N40:        Reference point between SMF and the CHF.
  • NOTE 6:        The reference points from N40 up to and including N49 are reserved for allocation and definition in TS 23.503 [45].
  • N50:        Reference point between AMF and the CBCF.
  • N51:        Reference point between AMF and NEF.
  • N51i:        Reference point between I-NEF and the AMF in the VPLMN.
  • N52:        Reference point between NEF and UDM.
  • N53:        Reference point between the I-NEF and the NEF.
  • N55:        Reference point between AMF and the UCMF.
  • N56:        Reference point between NEF and the UCMF.
  • N57:        Reference point between AF and the UCMF.
  • N58:        Reference point between AF and the NEF


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