Content for  TS 23.316  Word version:  18.5.0

The 5G QoS parameters specified in clause 5.7.2 of TS 23.501 are applicable to wireline access network, with the following differences:

• The parameters defined in clause 4.5.1.2 are applicable for the wireline access network related PDU sessions.
• UE-AMBR is not applicable to wireline access. The AMF should not provide the subscribed UE-AMBR to the W-AGF.

The wireline access networks may exhibit QoS control mechanisms and related thresholds, such as QoS class specific maximum bit rates, which the W-AGF needs to be aware of, in order to provide appropriate mapping of the QoS characteristics of the 5G QoS flows to the wireline technology specific QoS parameters. These wireline access characteristics are considered to be relevant for a specific wireline access subscription, and correspond to RG level QoS information in the 5GC. While the wireline access characteristics are important for implementing the end to end QoS mechanisms, across the 5G-RG/FN-RG, the W-5GAN and the 5GC, they only need to be acted on in the 5G-RG/FN-RG and the W-5GAN. In the case of 5G-RG serving the AUN3 devices, the RG Level Wireline Access Characteristics stored in 5G-RG's subscription includes a maximum bit rate for the aggregated traffic of the 5G-RG and of the AUN3 devices served by this 5G-RG. In order to support the W-AGF in implementing the mapping between 5G QoS parameters and wireline access specific parameters, the AMF may provide the RG Level Wireline Access Characteristics (RG-LWAC) to the W-AGF at the time of the RG registration. When the UDM notifies the AMF of the updated RG-LWAC via Nudm_SDM_Notification service, the AMF may update the RG-LWAC to the W-AGF via NGAP UE Context Modification procedure. Given that the 5GC does not act on these parameters, their structure is out of scope in 3GPP specifications and they are handled as a transparent data container. BBF and CableLabs may define the content and structure of this container for their own use. The UE subscription data parameters RG Level Wireline Access Characteristics are defined in clause 8.1.1.

IP address allocation is performed as described in clause 5.8.2.2 of TS 23.501, with the differences and additions described in this clause. Stateless IPv6 Address Autoconfiguration applies with the differences described in clause 4.6.2.4. In addition to the IP address management features described in clause 5.8.2.2 of TS 23.501 the 5GC network functions and RG support the following mechanisms:

1. IPv6 address allocation using DHCPv6 may be supported for allocating individual /128 IPv6 address(es) for a PDU Session. The details of IPv6 address allocation using DHCPv6 are described in clause 4.6.2.2.
2. The details of Prefix Delegation are described in clause 4.6.2.3.
3. IPv6 Prefix Delegation using DHCPv6 may be supported for allocating additional IPv6 prefixes for a PDU Session.

The mechanisms in a. and b. above are only applicable for IPv6 and IPv4v6 PDU Session types. The requested IPv6 address or set of IPv6 Prefixes may be (as defined in clause 5.8.2.2.1 of TS 23.501):

• allocated from a local pool in the SMF or
• obtained from the UPF. In that case the SMF shall interact with the UPF via N4 procedures to obtain a suitable IP address/Prefix, or
• obtained from an external server.

When obtaining the IP address from the UPF, the SMF provides the UPF with the necessary information allowing the UPF to derive the proper IP address (e.g. the network instance, IP version, size of the IP address or Prefix the UPF is to allocate). The SMF may also provide IP configuration parameters (e.g. MTU value) to the 5G-RG, as described in clause 5.6.10 of TS 23.501. In this clause, unless specified otherwise, the RG may correspond either to a 5G RG or to a FN RG.

Optionally, and instead of using Stateless IPv6 Address Autoconfiguration, individual 128-bit IPv6 address(es) may be assigned to a PDU Session. In this case, after PDU Session Establishment, the SMF sends a Router Advertisement message (solicited or unsolicited) towards the RG. The SMF shall set the Managed Address Configuration Flag (M-flag) in the Router Advertisement messages to indicate towards the RG that IPv6 Address allocation using DHCPv6 is available, as described in RFC 4861. In that case the IPv6 address of the RG is allocated using DHCPv6 Identity Association for Non-temporary Addresses (IA_NA) and mechanisms defined in RFC 8415. The SMF may receive a Router Solicitation message, soliciting a Router Advertisement message. When using DHCPv6 address allocation, a prefix (e.g. /64) may be allocated for the PDU Session at PDU Session Establishment from which the /128 addresses are selected. The SMF determines the size of the prefix for a PDU Session to a specific DNN and S-NSSAI based on subscription data and local configuration. The individual /128 address(es) allocated to the RG as part of DHCP IA_NA procedure are then selected from the prefix allocated to the PDU Session. For statically assigned prefix, the subscription data in UDM for a DNN and S-NSSAI includes the prefix. Alternatively, individual 128-bit address(es) are allocated for the PDU Session without allocating a prefix to the PDU Session and provided to the RG as part of DHCP IA_NA procedure. When a prefix is allocated to the PDU Session, the SMF provides the prefix to the PCF instead of each /128 address. When individual /128 address(es) are allocated without allocating a prefix to the PDU Session, the SMF provides the /128 bits address(es) to PCF. Whether the SMF allocates a prefix for the PDU Session or individual 128-bit addresses is transparent to the RG and W-5GAN. If Prefix Delegation (as described in clause 4.6.2.3) is also supported, a SMF may receive both DHCP options for IA_NA and IA_PD together in a single DHCPv6 message. An SMF may provide a reply to both IA_NA and IA_PD in the same message or alternatively process the DHCPv6 IA_NA before the DHCPv6 IA_PD. The SMF may receive multiple different IA_NA related DHCP requests within the same PDU Session. When IPv6 Address Allocation using DHCPv6 is used, 5GC does not support IPv6 multi-homing for enabling SSC mode 3 and PDU Sessions with multiple PDU Session Anchors.

In addition to what is the specified in clause 5.8.2.2.4 of TS 23.501, there is following difference:

• UE is replaced by 5G-RG and FN-RG.
• For IPv6 stateless IPv6 address autoconfiguration or IPv6 address allocation using DHCPv6, the SMF determines the maximum size of the prefix that may be allocated for the PDU Session based on subscription data and local configuration.
• If IPv6 address allocation using DHCPv6 is used, the DHCPv6 message may include a request for a delegated prefix (IA_PD) together with a request for an IPv6 address (IA_NA). Alternatively, a delegated prefix may be requested after an IPv6 address has been assigned using IA_NA.
• If the DHCPv6 request indicates support for prefix exclusion via the OPTION_PD_EXCLUDE option code in an OPTION_ORO option and if the SMF accepts this option, the SMF delegates a prefix excluding the default prefix with help of OPTION_PD_EXCLUDE. Prefix exclusion procedures shall follow RFC 6603.

Stateless IPv6 Address Autoconfiguration applies as described in clause 5.8.2.2.3 of TS 23.501 with the differences described below. When the W-AGF is serving an FN-RG, the W-AGF may include in the PDU Session Establishment Request an interface identifier of the FN-RG IPv6 link-local address associated with the PDU Session. If the SMF receives an interface identifier in the PDU Session Establishment Request message, the SMF provides this interface identifier value as the UE interface identifier in the PDU Session Establishment Accept message. To ensure that the link-local address used by the FN-RG does not collide with the link-local address of the SMF in this case, the SMF selectes a different link-local address for use as the SMF link local address for the PDU Session. If the PDU Session Establishment Request message does not contain an interface identifier, the SMF selects interface identifier for the UE, and SMF link-local address, as described in clause 5.8.2.2.3 of TS 23.501. In case of wireline access, independent of whether SMF received an interface identifier in the PDU Session Establishment Request message or not, the SMF includes the SMF link local address in the PDU Session Establishment Accept message.