5 Network Function

23.3163GPPRelease 18TSWireless and wireline convergence access support for the 5G System (5GS)

5.0 General

This clause specifies the definition network function specific for W-AGF and the delta to network function defined in TS 23.501 [2].

5.1 Network Function Functional description

5.1.1 W-AGF

The functionality of W-AGF in the case of Wireline 5G Access network includes the following:

– Termination of N2 and N3 interfaces to 5G Core Network for control – plane and user-plane respectively.

– Handling of N2 signalling from SMF (relayed by AMF) related to PDU Sessions and QoS.

– Relaying uplink and downlink user-plane packets between the 5G-RG and UPF and between FN-RG and UPF. This involves:

– Enforcing QoS corresponding to N3 packet marking, taking into account QoS requirements associated to such marking received over N2.

– N3 user-plane packet marking in the uplink.

– Supporting AMF discovery and selection defined in TS 23.501 [2] clause 6.3.5 where the 5G-S-TMSI is not used for AMF selection since the wireline AS layer can only carry the GUAMI.

– Termination of wireline access protocol on Y4 and Y5.

– In the case of FN-RG the W-AGF acts as end point of N1 on behalf of the FN-RG.

In the case of Wireline 5G Broadband Access network the definition of W-AGF functionalities is specified in BBF TR-456 [9] and WT-457 [10].

NOTE: The W-AGF is specified as AGF (Access Gateway Function) in BBF TR-456 [9] for supporting 5G-RG and FN-RG and as FMIF (Fixed Mobile Interworking Function) for supporting FN-RG only in the case of presence of BNG in WT-457 [10]. Both cases for FN-RG support, i.e. AGF and FMIF, have identical interfaces towards 5GC, i.e. it is transparent to 5GC whether AGF or FMIF is used and no difference between AGF or FMIF cases is defined in this specification.

In the case of Wireline 5G Cable Access network the definition of W-AGF functionalities is specified by Cablelabs WR-TR-5WWC-ARCH [27].