6.4 NBIFOM IP Flow Mapping

23.1613GPPNetwork-Based IP Flow Mobility (NBIFOM)Release 17Stage 2TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

6.4.1 UE Requested IP Flow Mapping via 3GPP access

This procedure is only used in Network-initiated NBIFOM mode when the UE wants to request the network to apply specific mappings of IP flows to 3GPP access. The network provides Routing Rules to the UE for this IP flow unless the request from the UE is not allowed by the subscription.

Figure 6.4.1-1: UE requested IP flow mapping via E-UTRAN

This procedure is similar to 6.3.3.1-1 with the following differences:

Step 2-5: The UE sends a Request Bearer Resource Modification message to the network, which includes the mapping information of an IP flow to 3GPP access.

Step 6: When dynamic PCC is applied for the PDN connection, the PDN GW initiates an IP-CAN Modification procedure and provides the Routing Rule(s) for this IP flow according to the mapping information in a notification to the PCRF. The PCRF may reject the IP flow mapping request from UE. When the network rejects an IP flow mapping request, the network provides a certain cause value to the UE indicating why the request was rejected. This cause value may be used by the UE to determine when/if this IP flow mapping can be requested again.

The PDN GW sends corresponding Routing rule(s) to the UE in Bearer Modification response.

Figure 6.4.1-2: UE requested IP flow mapping via GERAN/UTRAN access

This procedure is similar to 6.3.3.1-2 with the following differences:

Step 2-5: The UE sends a Modify PDP Context Request message to the network, which includes the mapping information of an IP flow to 3GPP access.

Step 5: When dynamic PCC is applied for the PDN connection, the PDN GW initiates an IP-CAN Modification procedure and provides the Routing Rule(s) for this IP flow according to the mapping information in a notification to the PCRF. The PCRF may reject the IP flow mapping request from UE. When the network rejects an IP flow mapping request, the network provides a certain cause value to the UE indicating why the request was rejected. This cause value may be used by the UE to determine when/if this IP flow mapping can be requested again.

Step 6. The PDN GW initiates the Secondary PDP context activation or EPS Bearer modification procedure as described in TS 23.060 [5], and including the Routing Rule(s).

When the SGSN receives Create Bearer Request or Update Bearer Request message from the SGW, the SGSN sends Request Secondary PDP Context Activation or Modify PDP Context Request to the UE as described in TS 23.060 [5], including the Routing Rules received from the SGW. The SGSN also sends a Modify PDP Context Accept message to the UE in order to stop the timer which is set after Step 2.

The UE may accept or reject the Routing Rules. When the UE rejects the Routing Rules, the UE provides a cause value indicating why the request was rejected. The UE applies the accepted routing rules and acknowledges the applied rules in Activate Secondary PDP Context Request or Modify PDP Context Accept message.

The PDN GW sends corresponding Routing rule(s) to the UE in Bearer Modification response.

6.4.2 UE Requested IP Flow Mapping via Trusted WLAN access

6.4.2.1 Single-connection mode

In single-connection mode, the UE sends the request for IP flow mapping over 3GPP access as described in clause 6.4.1.

6.4.2.2 Multi-connection mode

This procedure is only used in NW-initiated NBIFOM mode when the UE wants to request the NW to apply a specific mapping of an IP flow to TWAN access. The NW provides Routing Rules to the UE for this IP flow.

Figure 6.4.2.2-1: UE Requested IP Flow Mapping via Trusted WLAN access using GTP

1. The PDN Connection is active simultaneously over 3GPP access and WLAN accesses.

2. The UE sends a WLCP PDN Modification Command message to the TWAN, which includes the IP Flow mapping information requested by the UE.

3. The TWAN sends a Bearer Resource Command message to the PDN GW. The message includes the requested IP Flow mapping information.

4. The PDN GW initiates the IP-CAN Session Modification Procedure with the PCRF. In this request, the PDN GW provides the requested IP Flow mapping information to the PCRF. The PCRF analyses the received Routing Rules, makes a policy decision and provides new or updated PCC rules to the PDN GW with corresponding access type information. The PCRF may reject the requests from UE. When the network rejects a request, the network provides a cause value to the UE indicating why the request was rejected. The UE should be able to determine, based on the cause value provided with the rejection, how to handle the flow mapping, e.g. whether or not the request may be retried at a later stage.

5. The PDN GW decides to update the Routing Rules based on the received PCC Rules. This step is the same as steps 3-8 in Figure 6.3.2.2.2-1.

6.4.3 UE Requested IP Flow Mapping via Untrusted WLAN access

This procedure is only used in network-initiated mode when the UE wants to request the network to apply a specific mapping of an IP flow to untrusted WLAN access. The network provides Routing Rules to the UE for this IP flow.

Figure 6.4.3-1: UE Requested IP Flow Mapping via untrusted WLAN access using GTP

1. The PDN Connection is active simultaneously over 3GPP access and WLAN accesses.

2. The UE sends an IKEv2 INFORMATIONAL Request message to the ePDG, which includes the IP Flow mapping information requested by the UE.

2a. The ePDG sends an IKEv2 INFORMATIONAL Response message to the UE.

3. The ePDG sends a Bearer Resource Command message to the PDN GW. The message includes the requested IP Flow mapping information.

5. The PDN GW decides to update the Routing Rules based on the received PCC Rules. This step is the same as steps 3-9 in Figure 6.3.2.3-1.