Section: 5.28.5.2 5GS DetNet node reporting
Content: The TSCTSF may provide exposure information to the DetNet controller using information collected from the 5GS entities. The exposure information can be used by the DetNet controller to build up the network topology information. The exposure may be based on IETF RFC 8343 [151] and IETF RFC 8344 [152]. The TSCTSF may collect the information from the UPF/NW-TT via parameters in PMIC as defined in clause 5.28.3.1. For the device side ports, the TSCTSF collects information using parameters provided from SMF to TSCTSF via PCF as described in clause 6.1.3.23b of TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [45]. When the MTU size for IPv4 or IPv6 is not provided to TSCTSF for a port, the TSCTSF may use a pre-configured default value for IPv4 or IPv6. In the case of network side ports, the TSCTSF may collect information on the type of the interface (defined in IETF RFC 8343 [151], with values defined in IETF RFC 7224 [153]) associated with the port. In the case of device side ports, which correspond to the PDU Sessions that are reported to the TSCTSF, the default value of "3GPP WWAN" (wwanPP) for the interface type is assumed. The TSCTSF can differentiate network side ports as they are reported from the NW-TT within UMIC/PMIC, while device side ports correspond to the PDU Sessions, reported to the TSCTSF in the associated AF sessions. For device side ports also information on IP addresses or IP prefixes not directly assigned to the port but reachable via the port may be provided. On the device side ports, these are related to Framed Routes, i.e. a range of IPv4 addresses or IPv6 prefixes reachable over a single PDU Session, as defined in clause 5.6.14, or prefixes delegated by IPv6 prefix delegation as defined in clause 5.8.2.2. This additional information helps both the TSCTSF and the DetNet controller to map flows to the correct UE address as described in clause 5.28.5.3. For the network side ports, the TSCTSF may also collect information on the link layer address and neighbor IP nodes. The ports are identified by the port number within the 3GPP system. The port number may also be used to generate interface identifiers towards the DetNet controller that are unique within the 5GS node. NOTE 1: One possibility to generate unique interface identifiers towards the DetNet controller is to use the port number as the if-Index as defined in IETF RFC 8343 [151]. Based on the if-Index, an interface name is generated, e.g. by using the if-Index as a string, possibly adding a substring prefix or postfix based on configuration. The if-Index and the name of the interface contain essentially the same information, but both can be provided, since the name is used as the key in the YANG model, while if-Index is usually considered as the basis for interface management of IP nodes. The TSCTSF may use the user-plane node ID provided by the UPF to generate an identifier of the 5GS node that is provided to the DetNet controller. NOTE 2: The 5GS node identification can be realized by providing an identifier of the 5GS node to the DetNet controller, or the TSCTSF can use different termination points (addresses) for the signalling between the DetNet controller and the TSCTSF. For network side ports, the information is transferred in PMIC between the NW-TT and the TSCTSF. For device side ports, the information is transferred without relying on PMIC, using parameters from the SMF via the PCF to the TSCTSF.