14 Interworking with DN (Ethernet)

29.5613GPP5G SystemInterworking between 5G Network and external Data NetworksRelease 17Stage 3TS

When support of Ethernet PDU type data is provided at the N6 interface, the SMF and UPF may support ARP proxying as specified in IETF RFC 1027 [35] and/or IPv6 Neighbour Solicitation Proxying as specified in IETF RFC 4861 [33] functionality. Based on operator configuration, during the PDU session establishment, the SMF may request the UPF acting as the PDU Session Anchor to proxy ARP/IPv6 Neighbour Solicitation or to forward the ARP/IPv6 Neighbour Solicitation traffic from the UPF to the SMF.

Ethernet Preamble, Start Frame Delimiter (SFD) and Frame Check Sequence (FCS) are not sent over 5GS:

– For UL traffic the UE strips the Preamble, SFD and FCS from the Ethernet frame, those fields shall be added by the UPF acting as the PDU Session Anchor.

– For DL traffic the UPF acting as the PDU Session Anchor shall strip the Preamble, SFD and FCS from the Ethernet frame.

IP address is not allocated by the SMF to the UE for this PDU Session. The UPF shall store the MAC addresses, received from the UE, and associate those with the appropriate PDU Session.

NOTE 1: The UE can operate in bridge mode with regard to a LAN it is connecting to the 5GS, thus different MAC addresses can be used as source address of different frames sent UL over a single PDU Session (and destination MAC address of different frames sent DL over the same PDU Session)

NOTE 2: Entities on the LAN connected to the 5GS by the UE can have an IP address allocated by the external DN, but the IP layer is considered as an application layer which is not part of the Ethernet PDU Session.

NOTE 3: In this Release of the specification, only the UE connected to the 5GS is authenticated, not the devices behind such UE.

When a PDU Session of Ethernet PDU type is authorized by a DN, the DN-AAA server may, as part of authorization data, provide the SMF with a list of allowed MAC addresses (maximum 16) for this PDU Session. When such a list has been provided for a PDU Session, the SMF sets corresponding filtering rules in the UPF(s) acting as PDU Session Anchor for the PDU Session and the UPF discards any UL traffic that does not contain any of these MAC addresses as a source address.

Figure 14-1: Protocol stacks for Ethernet PDU type data (user plane) for N6 reference point