6.3 IP flow mobility within a PDN connection

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

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

6.3.1 General

6.3.2 Network-initiated IP flow mobility

6.3.2.1 Routing Rules signalled via 3GPP access

In the case of network-initiated NBIFOM mode, the following procedures are applicable for S2a-SCM, S2a-MCM or S2b when target network is 3GPP access.

In the following signalling flow, the PDN GW moves one or more IP flow(s) by providing a Routing Rule with access type 3GPP. The routing rule is sent via E-UTRAN in this case.

Figure 6.3.2.1-1: Network-initiated IP flow mobility within a PDN connection via E-UTRAN using GTP

1. The UE is connected simultaneously to 3GPP and Trusted/Untrusted WLAN access.

2. When dynamic PCC is applied for the PDN connection, the H-PCRF determines based on policy information and current UE state that session modification should be initiated to move specific flows. The PCRF provides PCC Rules with access type information to the PDN GW during an IP-CAN session modification procedure. The PDN GW determines that new Routing Rules / Modified Routing Rules need to be sent to the UE based on the received PCC Rules.

When dynamic PCC is not applied, the PDN GW may determine based on local policies that new Routing Rules / Modified Routing Rules need to be sent to the UE.

3. The PDN GW sends the Created /Modified Routing Rules within Create/Update/Delete Bearer Request to the Serving GW. If bearer resources need to be established or modified due to the PCC rules received in step 2, the bearer operations may be performed in this step

4. The bearer modification,dedicated bearer activation or dedicated bearer deactivation procedure between the MME and the UE is performed as described in TS 23.401 [4]. 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. This cause value may be used by the network to determine when/if this IP flow mobility operation can be requested again. The UE applies the accepted routing rules and acknowledges the applied rules in the message sent to the MME.

5. The MME sends Create/Update/Delete Bearer Response indicating the accepted Routing Rules to the PDN GW via the Serving GW.

6. The PDN GW indicates to the PCRF whether the PCC Rule could be enforced or not. This corresponds to the completion of the PCEF-initiated IP‑CAN session modification procedure as defined in TS 23.203 [3], proceeding after the completion of IP‑CAN bearer signalling.

7. Appropriate S2a/S2b resource release/modification procedures are executed for the resources associated with the flows that were removed from the Trusted or Untrusted WLAN access as described in TS 23.402 [2]. For S2a-SCM, dedicated bearer over S2a is not supported when IP flow mobility is used.

Figure 6.3.2.1-2: Network-initiated IP flow mobility within a PDN connection via GERAN/UTRAN using GTP

1. The UE is connected simultaneously to GERAN/UTRAN and Trusted/Untrusted WLAN access.

When dynamic PCC is not applied, the PDN GW may determine based on local policies that new Routing Rules / Modified Routing Rules need to be sent to the UE.

3. The PDN GW sends the Created /Modified Routing Rules within Create/Update/Delete Bearer Request to the Serving GW/SGSN. If bearer resources need to be established or modified due to the PCC rules received in step 2, the bearer operations may be performed in this step.

4. The dedicated bearer activation or bearer modification or dedicated bearer deactivation procedure between the MME and the UE is performed as described in TS 23.060 [5]. 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. This cause value may be used by the network to determine when/if this IP flow mobility operation can be requested again. The UE applies the accepted routing rules and acknowledges the applied rules in the message sent to the SGSN.

5. The SGSN sends Create/Update/Delete Bearer Response indicating the accepted Routing Rules to the PDN GW via the Serving GW.

6.3.2.2 Routing Rules signalled via Trusted WLAN access

6.3.2.2.1 Single-connection mode

In single-connection mode, the PDN GW sends the routing rules over 3GPP access independent of access type, as described in clause 6.3.2.1.

6.3.2.2.2 Multi-connection mode

In the following signalling flow, the PDN GW provides new or updated Routing Rule(s) with access type WLAN via GTP and WLCP procedures. The routing rule is sent via TWAN access in this case. This may result in that IP flows routed over 3GPP access are now routed over WLAN, or vice versa.

Figure 6.3.2.2.2-1: Network-initiated IP flow mobility within a PDN connection over TWAN access using GTP

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

2. If dynamic PCC is applied for the PDN Connection the PCRF determines based on policy information and current UE state that session modification should be initiated to move specific flows. The PCRF provides PCC Rules with access type information to the PDN GW during an IP-CAN session modification procedure. The PDN GW determines that new Routing Rules / Modified Routing Rules need to be sent to the UE based on the received PCC Rules.

If dynamic PCC is not applied the PDN GW may determine based on local policies that new Routing Rules / Modified Routing Rules need to be sent to the UE.

3. The PDN GW sends the new or updated Routing Rules within Create/Update/Delete Bearer Request to the TWAN. If bearer resources need to be established or modified due to the PCC rules received in step 2, the bearer operations may be performed in this step.

4. The TWAN sends a WLCP PDN Connection Modification Request message to the UE, including the Routing Rules.

5. The UE may decide to 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. This cause value may be used by the network to determine when/if this IP flow mobility operation can be requested again. The UE applies the accepted routing rules and acknowledges the applied rules in a WLCP PDN Connection Modification Response message to the TWAN.

6. The TWAN sends Create/Update/Delete Bearer Response to the PDN GW.

7. The PDN GW indicates to the PCRF whether the PCC Rules could be enforced or not. This corresponds to the completion of the PCEF-initiated IP‑CAN session modification procedure as defined in TS 23.203 [3].

8. Appropriate 3GPP resource release/modification procedures are executed as described in TS 23.401 [4] for the resources (bearers) associated with the Routing Rules that were removed from 3GPP access.

6.3.2.3 Routing Rules signalled via Untrusted WLAN access

In the following signalling flow, the PCRF identifies and moves specific flows from 3GPP to WLAN.

Figure 6.3.2.3-1: IP flow mobility within a PDN connection with negotiation via untrusted WLAN access

1. The UE is connected simultaneously to 3GPP and WLAN accesses and establishes multiple IP flows of the same PDN connection.

2. If dynamic PCC is applied for the PDN Connection, the PCRF determines based on policy information and current UE state that session modification should be initiated to move specific flows. The PCRF provides PCC Rules with access type information to the PDN GW during an IP-CAN session modification procedure.

3. The PDN GW determines that new or modified Routing Rules need to be sent to the UE based on the received PCC Rules. The PDN GW sends the new or updated Routing Rules within Create/Update/Delete Bearer Request to the TWAN. If bearer resources need to be established or modified due to the PCC rules received in step 2, the bearer operations may be performed in this step.

4. The ePDG initiates an IKEv2 INFORMATIONAL request, which includes the modified routing rule to indicate the updated routing rule to be used by the UE. 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. This cause value may be used by the network to determine when/if this IP flow mobility operation can be requested again.

5. The UE responds with a IKEv2 INFORMATIONAL response, acknowledging the new routing rules and applies the corresponding filters

6. The ePDG sends a Create/Update/Delete Bearer Response to the PDN GW.

7. The WLAN access specific resource release, setup or modification may be performed based on the modified traffic selector in WLAN access network.

8. The PDN GW indicates to the PCRF whether the Routing Rules could be enforced or not.

9. Appropriate 3GPP resource release/modification procedures are executed for the resources associated with the new or updated PCC rules.

6.3.3 UE-initiated IP flow mobility

6.3.3.1 Routing Rules signalled via 3GPP access

In the following signalling flows, they are applied to UE-initiated NBIFOM mode. The UE moves one or more IP flow(s) by providing a Routing Rule with access type 3GPP to update the routing rules via NAS and GTPv2 procedures. The routing rule is sent via E-UTRAN in this case.

Figure 6.3.3.1-1: UE-initiated IP flow mobility within a PDN connection via E-UTRAN using GTP

1. The UE is connected simultaneously to 3GPP and WLAN accesses and establishes multiple IP flows of the same PDN connection.

2. The UE sends to the MME a Request Bearer Resource Modification message, which includes the Routing Rules requested by the UE.

4-5. The MME forwards the Routing Rules to the PDN GW via the Serving GW.

6. When dynamic PCC is applied for the PDN connection, the PDN GW initiates an IP-CAN Modification procedure and provides the Routing Rules in a notification to the PCRF. The PCRF may reject the IP flow mobility requests from UE due to subscription limitations. When the network rejects an IP flow mobility 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 mobility operation can be requested again.

7. The PDN GW performs the dedicated Bearer activation procedure or bearer modification procedure as described in TS 23.401 [4], and indicates which the Routing Rule has been accepted.

8. Appropriate S2a/S2b resource release / modification procedures are executed for the resources associated with the flows that were removed from the Trusted or Un-trusted WLAN access as described in TS 23.402 [2]. For S2a-SCM, dedicated bearer over S2a is not supported when IP flow mobility is used.

In the following signalling flows, they are applied to UE-initiated NBIFOM mode. The UE moves one or more IP flow(s) by providing a Routing Rule with access type 3GPP to update the routing rules via PDP context and GTPv2 procedures. The routing rule is sent via GERAN/UTRAN in this case.

Figure 6.3.3.1-2: UE-initiated IP flow mobility within a PDN connection via GERAN/UTRAN using GTP

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

2-3. The UE sends to the SGSN a Modify PDP Context Request message, which includes the Routing Rules requested by the UE.

7. The PDN GW performs the Secondary PDP context activation or PDP context modification procedure as described in TS 23.060 [5], and indicates the Routing Rule has been accepted.

6.3.3.2 Routing Rules signalled via Trusted WLAN access

6.3.3.2.1 Single-connection mode

In single-connection mode, the UE sends the routing rules over 3GPP access as described in clause 6.3.3.1.

6.3.3.2.2 Multi-connection mode

In the following signalling flow, the UE provides new or updated routing rules with access type WLAN to the PDN GW via WLCP and GTPv2 procedures. The routing rule is sent via TWAN access in this case.

Figure 6.3.3.2.2-1: UE-initiated IP flow mobility within a PDN connection from 3GPP access to TWAN 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 Routing Rules requested by the UE.

3. The TWAN sends a Bearer Resource Command message to the PDN GW. The message includes the Routing Rules.

4. The PDN GW initiates the IP-CAN Session Modification Procedure with the PCRF. In this request, the PDN GW provides the Routing Rules 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 IP flow mobility requests from UE. When the network rejects an IP flow mobility 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 sends to the TWAN an Update/Create Bearer Request which acknowledge of the Routing Rules. If bearer resources need to be established or modified due to the PCC rules received in step 4, the bearer operations may be performed in this step.

5a. The TWAN sends a WLCP PDN Connection Modification Request to the UE which acknowledge of the Routing Rules.

6 The UE sends a WLCP PDN Connection Modification Response to the TWAN.

7. The TWAN sends an Update/Create Bearer Response to the PDN GW.

8. A TWAN specific resource allocation/modification procedure may be executed in this step. The details of this step are out of the scope of 3GPP.

9. Appropriate 3GPP resource release / modification procedures are executed for the resources associated with the flows that were removed in the 3GPP access as described in TS 23.401 [4].

6.3.3.3 Routing Rules signalled via Untrusted WLAN access

The UE can move one or more IP flow(s) from the 3GPP access to the WLAN access. The UE should update the routing rules via the WLAN access.

Figure 6.3.3.3-1: IP flow mobility within a PDN connection initiated over WLAN access

1. The UE is connected simultaneously to 3GPP and WLAN accesses and establishes multiple IP flows of the same PDN connection as described in clauses 6.2.

2. The UE sends the IKEv2 INFORMATIONAL request to the ePDG, which includes the updated routing rules 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 updated routing rules. The ePDG includes the default EPS bearer ID (i.e. Linked Bearer ID) based on the mapping between the Security Association and the PDN connection. The ePDG sends the updated routing rules to the PDN GW.

4. The PDN GW initiates the IP-CAN Session Modification Procedure with the PCRF. In this request, the PDN GW provides the updated routing rules to the PCRF. The PCRF may reject the IP flow mobility requests from UE. When the network rejects an IP flow mobility request, the network provides a certain 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 sends an Update/Create Bearer Request message to the ePDG which includes the accepted routing rules.

5a. The ePDG sends an IKEv2 INFORMATIONAL Request message to the UE which includes the accepted routing rules.

6. The UE sends the IKEv2INFORMATIONAL response to the ePDG.

7. The ePDG sends an Update/Create Bearer Response message to the PDN GW.

8. Appropriate 3GPP resource release/modification procedures are executed for the resources associated with the flows that were modified or removed in the 3GPP access.

9. The PDN GW indicates to the PCRF whether the PCC decision could be enforced or not.