6.12 NBIFOM Routing rule

23.2033GPPPolicy and charging control architectureRelease 17TS

6.12.1 General

The NBIFOM routing rule comprises the information about the UE request to associate an access type to a service data flow filter. The NBIFOM routing rules are provided by the PCEF to the PCRF during IP‑CAN session establishment or modification.

The PCEF derives NBIFOM routing rules based on the Routing Rules received from the UE (when UE-initiated NBIFOM mode applies) or based on requests from the UE to have the network create / modify / delete Routing Rules (when Network-initiated NBIFOM mode applies), as described in TS 23.161 [43].

Table 6.12 lists the information contained in an NBIFOM routing rule, including the information name, the description and whether the PCEF may modify this information in an updated version of the rule. The Category field indicates if a certain piece of information is mandatory or not.

Table 6.12: The NBIFOM routing rule information

Information name	Description	Category	PCEF permitted to modify in an update
Routing Rule identifier	Uniquely identifies the routing rule within an IP‑CAN session.	Mandatory	No
Routing information	This clause defines the method for detecting packets belonging to a flow and the route for the flow.
Routing Rule Priority	Determines the order, in which the routing filters are applied.	Mandatory	Yes
Routing Filter	A packet filter for the detection of IP flows.	Mandatory	Yes
Routing Access Information	The access type that the matching IP flows intend to use.	Mandatory	Yes

The Routing Rule identifier shall be unique for a NBIFOM routing rule within an IP-CAN session. It is set to the Routing Rule identifier assigned by the UE when UE-initiated NBIFOM mode applies as specified in TS 23.161 [43] or by the PCRF when Network-initiated NBIFOM mode applies.

The Routing Rule Priority defines in what order the NBIFOM routing rules are used by the PCRF to determine where to route a service data flow. The Routing Rule Priority is set according to the information provided by the UE as specified in TS 23.161 [43].

The Routing Filter comprises a single packet filter, containing information for matching IP flows. The format of the routing filter is the same as the service data flow filter described in clause 6.2.2.2. The Routing Filter is set according to the information provided by the UE as specified in TS 23.161 [43].

The Routing Access Information indicates the IP-CAN type that the IP flows matching the Routing Filter of this NBIFOM routing rule intend to use.

6.12.2 NBIFOM Routing rule operations

NBIFOM routing rule operations consist of creation, modification and removal of a NBIFOM routing rule.

At creation of a NBIFOM routing rule, the PCEF provides the NBIFOM routing rule information to the PCRF. The PCRF checks if there is a PCC Rule with a corresponding service data flow template installed in the PCEF. If it is so, the PCRF updates the Allowed Access Type in this PCC Rule according to the Routing Access Information. Otherwise a new PCC Rules is created with a service data flow filter equal to the Routing Filter, a precedence according to the Routing Rule Priority and the Allowed Access Type set to the Routing Access Information and then installed in the PCEF.

NOTE: If the Routing Filter is partially overlapping with a service data flow template of an installed PCC rule, it is up to the operator policy whether to reject the NBIFOM routing rule or whether to create a new PCC rule for this NBIFOM routing rule. In the latter case, this new PCC rule shall have the same parameters (except the rule name and the SDF template) and a higher precedence. The PCRF shall also ensure that relevant PCC rule modifications are applied for both PCC rules.

The PCRF shall store the relation between the Routing Rule identifier and the corresponding PCC rule. The PCRF may also reject a NBIFOM routing rule according to operator policy.

The modification of a NBIFOM routing rule to change the Routing Filter or the Routing Rule Priority triggers the PCRF to modify the service data flow filter or precedence in the corresponding installed PCC Rule accordingly.

The modification of a NBIFOM routing rule to change the Routing Access Information triggers the PCRF to change the Allowed Access Type in the corresponding installed PCC Rule accordingly.

The removal of a NBIFOM routing rule triggers the PCRF to remove the corresponding PCC Rule if the PCC rule creation was triggered by this NBIFOM routing rule. Otherwise, the PCRF removes only the Allowed Access Type in this PCC Rule.