In order to support traffic offloading or support SSC mode 3, the session management function SMF may control the data channel of the PDU session, so that the PDU can continuously match multiple N6 interfaces. UPF interrupts each of these ports (the end of N6 is UPF) , that is, it supports a PDU session anchor function. Each PDU session anchor supports a PDU session and provides different access to the same DN. Therefore, there are two main optional traffic grooming solutions: ① Give a PDU session Use uplink classifier; ② Use an IPv6 multi-homing for a PDU session.
1) Upstream classifier – artificially constructing multiple session channels (applicable to Internet protocol version 4 (IPv4), IPv6 and Ethernet session types>
For IPv4, IPv6, and Ethernet session types: SMF inserts an “upstream classifier” in the data path of a PDU session.
Upstream classifiers are supported by UPF and are used to logically divert some traffic (local traffic) to match the traffic filters provided by SMF. The insertion or removal of upstream classifiers is determined by SMF and is controlled by SMF (N4 and UPF functions) ).SMF may decide to insert a UPF-supported upstream classifier into the PDU session path, or it may remove the classifier from the PDU session data path. The insertion and removal can be during the PDU session establishment process or after the establishment is completed. Proceed.SMF may include more than one UPF to support upstream classifier functionality.
However, the UE is unaware of the traffic conversion made by the uplink classifier, and will not participate in the insertion and removal of the classifier. (UE awareness may be added in the future). For IP type PDU sessions, the UE combines the PDU After the session has an IPv4 address, there will be multiple anchor points for the PDU session. In this way, multiple PDU anchor points can provide multiple paths to the same data network. Specifically
The structure diagram is shown in Figure 15 (see Figure 5.6.4.2-1 of the 23.501 protocol in literature [9]): LoRa gateway
2〉Use IPv6 multi-homing for PDU sessions
Multi-homing PDU sessions. PDU session multi-homing is only available for IPv6 types. A PDU session may be associated with multiple IPv6 prefixes. Such multi-homing PDU sessions provide access to the data network through more than one PDU anchor (IPv6 ). Different user plane paths lead to different PDU anchor point branch outputs in a common UPF. This is the so-called UPF supporting “branch point function”.
The branch point provides forwarding of uplink traffic to different PDU anchor points, and at the same time merges the downlink data flow to the UE (actually, it combines the traffic from
Data from different PDU anchor points are merged and forwarded to the UE).
The branch point function is supported by UPF and is used to logically divert some traffic to match the traffic filter provided by SMF. The insertion or removal of upstream classifiers is determined by SMF and is controlled by SMF (N4 and UPF functions). SMF More than one UPF may be included to support the upstream classifier function (same as the upstream classifier). The details are shown in Figure 16 and Figure 17. Figure 17 shows the diagram of access to the local data network (see the 23.501 protocol in [9] Multi-homing model in case 5.6.4.3-2).
Features of using multiple IPv6 prefixes:
The source prefix of 1PDU. UPF supports the branch point function is
SMF configured, used to disperse uplink traffic among IP anchors, which are based on source prefix (selection method: UE selection or routing-based
information and references received on the network side).
IETF RFC 4191, used to influence the UE to select the source prefix. 3 This multi-homing PDU session supports first-receiver-segment service continuity and SSC mode 3.