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Content for  TS 23.261  Word version:  16.0.0

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5.4  IP flow mobility within a PDN connectionWord‑p. 15

5.4.1  General

This clause specifies the IP flow mobility procedures within a PDN connection. In these procedures the UE is assumed to simultaneously connect via a 3GPP access and a WLAN access. The UE is using both the accesses for the same PDN connection. Subsequently, the UE adds/modifies/deletes/moves between accesses IP flows using DSMIPv6 messages.
Non-roaming, home routed roaming and Local Breakout cases are supported by this procedure. The AAA proxy and vPCRF shown in Figure 5.4.2-1 are only used in the case of home routed roaming and Local Breakout. In non-roaming scenarios, the AAA proxy and vPCRF are not involved.
The optional interaction steps between the gateways and the PCRF in the procedures only occur if dynamic policy provisioning is deployed in EPC. These steps are not present when the solution is applied to I-WLAN mobility architecture according to TS 23.327.
There are two scenarios, depending on UE initiates the QoS establishment in the target access or the network performs the QoS establishment when the IP flow is moved.
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5.4.2  IP flow mobility within a PDN connection with network-initiated dynamic PCC

In this scenario the UE moves one or more IP flow(s) from one access to the other access and network-intiated dynamic PCC is used is used to set up or remove appropriate resources.
(not reproduced yet)
Figure 5.4.2-1: IP Flow Mobility and network initiated dynamic PCC
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Step 1.
The UE is simultaneously connected to a 3GPP access and a WLAN access based on the procedures specified in clauses 5.2 and 5.3. Based on current routing rules some traffic is routed through the 3GPP access and some other traffic through the WLAN access.
Step 2.
The UE sends a Binding Update (HoA, BID, FID) as specified in RFC 5555, RFC 5648 and RFC 6089 to the HA to install a new routing rule or to modify the routing address of an existing routing rule to route the respective traffic (identified by the included FID) through one particular access (identified by the included BID) or to remove an existing routing rule. In case of new routing rule with a new FID mobility option, the UE includes the routing filter description.
Step 3.
In case the HA function is implemented in EPC, the PDN GW sends an IP-CAN session modification request to the PCRF. In this request the PDN GW provides the updated routing rules to the PCRF. The PCRF stores the updated mapping between routing addresses and SDFs.
Step 4.
If the HA function is implemented in EPC, based on the successful establishment of resources in the WLAN access, the PCRF sends an acknowledgement to the PDN GW, including updated PCC rules if appropriate.
Step 5.
The HA sends a Binding Acknowledgment (Lifetime, HoA, BID, FID) as specified in RFC 5555, RFC 5648 and RFC 6089, to indicate which routing rules requested by the UE are accepted.
The PDN GW/HA may send message 5 before receiving the reply from PCRF in message 4.
Step 6.
If the HA function is implemented in EPC, based on the IP-CAN session modification request, the PCRF ensures that the relevant QoS rules are installed in the target access or the relevant QoS rules are uninstalled from the source access. For non-3GPP access, this is done by a GW control session and QoS rules provision procedure as specified in TS 23.203.
Step 7.
If the HA function is implemented in EPC, appropriate EPS resource release procedures are executed for those resources that were moved away from the 3GPP source access or appropriate EPS resource allocation procedures are executed for those resources that were moved onto the 3GPP access, as specified in TS 23.402. This procedure may be triggered by the PCRF via a GW control session and QoS rules provision procedure if PMIPv6 is used on S5 and it may be triggered by the PDN GW in case GTP is used on S5.
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5.4.3  IP flow mobility within a PDN connection with UE-initiated resource requestWord‑p. 16

In this scenario the UE requests for resources in the target access with UE-initiated procedures and when the resources are provided, the UE moves one or more IP flow(s) to the target access.
(not reproduced yet)
Figure 5.4.3-1: IP Flow Mobility and UE initiated resource request
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Step 1.
The UE is simultaneously connected to a 3GPP access and a WLAN access based on the procedures specified in clauses 5.2 and 5.3. Based on current routing rules some traffic is routed through the 3GPP access and some other traffic through the WLAN access.
Step 2.
Before moving an IP flow currently routed over WLAN to the 3GPP access, the UE requests appropriate resources in the 3GPP access. This is done as specified in clause 5.4.5 of TS 23.401 or in clause 9.2.2.1.1 or 9.2.2.1.1A of TS 23.060. In this procedure the UE includes the packet filters related to the requested resources. In this step if the HA function is implemented in EPC, the PDN GW may interact with the PCRF to trigger the appropriate PCC decision. The PCRF can authorize the resource establishment but since there is no change in the routing rules provided by the PDN GW.
Step 3.
The UE sends a Binding Update (HoA, BID, FID) as specified in RFC 5555, RFC 5648 and RFC 6089 to the HA to install a new routing rule or to modify the routing address of an existing routing rule to route the respective traffic (identified by the included FID) through one particular access (identified by the included BID) or to remove an existing routing rule. In case of new routing rule with a new FID mobility option, the UE includes the routing filter description.
Step 4.
In case the HA function is implemented in EPC, the PDN GW sends an IP-CAN session modification request to the PCRF. In this request the PDN GW provides the updated routing rules to the PCRF. The PCRF stores the updated mapping between routing addresses and SDFs.
Step 5.
If the HA function is implemented in EPC, based on the successful establishment of resources in the WLAN access, the PCRF sends an acknowledgement to the PDN GW, including updated PCC rules if appropriate.
Step 6.
The HA sends a Binding Acknowledgment (Lifetime, HoA, BID, FID) as specified in RFC 5555, RFC 5648 and RFC 6089, to indicate which routing rules requested by the UE are accepted.
The PDN GW may send message 6 before receiving the reply from PCRF in message 5.
Step 7.
If the HA function is implemented in EPC, based on the IP-CAN session modification request, the PCRF ensures that the resources associated with the routing filters moved to the 3GPP access are released. This is done by a GW control session and QoS rules provision procedure as specified in TS 23.203.
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5.5  Removal of an access from a PDN connectionWord‑p. 18

5.5.1  UE-initiated removal of an access from a PDN connection

In this scenario, the UE is attached to a 3GPP access and a WLAN access and is using both the accesses for the same PDN connection. Subsequently, the UE moves all IP flows associated with one access to another access and disconnects from the one access (e.g. due to loss of coverage or by an explicit detach).
The optional interaction steps between the gateways and the PCRF in the procedures only occur if dynamic policy provisioning is deployed in EPC. These steps are never present when the solution is applied to I-WLAN mobility architecture according to TS 23.327.
(not reproduced yet)
Figure 5.5-1: Removal of one access from the PDN connection
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Step 1.
The UE is simultaneously connected to a 3GPP access and a WLAN access based on the procedures specified in clauses 5.2 and 5.3. Based on current routing rules some IP flows are routed through the 3GPP access and some other IP flows through the WLAN access.
Step 2.
The UE decides to move all IP flows to one access and to disconnect from the other access (e.g. due to loss of coverage, based on internal trigger, based on updated policies from ANDSF).
  1. If UE disconnects one access (either a home link or a foreign link) and maintains the other access which is the foreign link, the UE sends a Binding Update (Lifetime, HoA, BID) to the HA with lifetime set to 0 to remove the BID of the access it disconnects from. Or, alternatively, the UE sends a Binding Update (HoA, BID) over the maintained foreign link to the HA with lifetime set to non-zero, the BID of the maintained foreign link, and "O" flag set.
  2. If the UE disconnects the WLAN access which is a foreign link and maintains only the 3GPP access which is the home link, the UE sends a Binding Update with lifetime 0 without any BID. This de-registration Binding Update can be sent from any available access.
Step 3.
In case the HA function is located in the PDN GW, the PDN GW initiates the IP-CAN session modification procedure with the PCRF. In this procedure, the PDN GW removes the routing address related to the removed BID associated with the IP-CAN session.
Step 4.
The HA sends a Binding Acknowledgment (Lifetime, HoA, BID) as specified in RFC 5555, RFC 5648 and RFC 6089.
Step 5.
If the HA function is located in the PDN GW, as part of the IP-CAN session modification procedure initiated in step 3, the PCRF ensures that the relevant QoS rules for the SDFs are installed in the target BBERF. This is done by a GW control session and QoS rules provision procedure as specified in TS 23.203.
Step 6.
If in step 2 the UE has removed the BID associated with the 3GPP access and maintained the BID for the WLAN access, the PDN GW shall initiate the PDN GW Initiated PDN Disconnection procedure in 3GPP access as defined in TS 23.402, clause 5.6.2.2 or the PDN GW Initiated Bearer Deactivation procedure as defined in TS 23.401, clause 5.4.4.1. The PDN GW shall set the release cause to 'RAT changed from 3GPP to Non-3GPP' to avoid the MME remove the PDN GW ID from the HSS. In case of I-WLAN mobility architecture and the UE has removed the BID associated with the 3GPP access, the UE may initiate PDP Context Deactivation as described in TS 23.060.
If the BID associated with the WLAN access is removed, according to TS 23.402 the security associations between the UE and the HA should not be immediately deleted. As the security associations were created dynamically using IKEv2 they will be automatically deleted when they expire. Similarly, for I-WLAN mobility architecture, the H2 session between the HA and the AAA Server should not be immediately deleted. The H2 session will be deleted by the HA immediately after security associations are deleted. In case of I-WLAN mobility architecture, the UE may initiate release of the IKEv2 security association with the PDG according to TS 23.234.
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5.5.2  HA-initiated removal of an access from a PDN connectionWord‑p. 19

In this scenario, the UE is attached to a 3GPP access and a WLAN access and is using both the accesses for the same PDN connection. The HA disconnects the UE from the one access (e.g. due to change of subscription).
The optional interaction steps between the gateways and the PCRF in the procedures only occur if dynamic policy provisioning is deployed in EPC. These steps are never present when the solution is applied to I-WLAN mobility architecture according to TS 23.327.
(not reproduced yet)
Figure 5.5-2: Removal of one access from the PDN connection
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Step 1.
The UE is simultaneously connected to a 3GPP access and a WLAN access based on the procedures specified in clauses 5.2 and 5.3. Based on current routing rules some IP flows are routed through the 3GPP access and some other IP flows through the WLAN access.
Step 2.
The HA sends a BRI message including a BID mobility option to remove only one of the binding registered for the UE as defined in RFC 5846.
Step 3.
The UE replies with a BRA message and removes the BID indicated by the HA as defined in RFC 5846.
Step 4.
In case the HA function is located in the PDN GW, the PDN GW initiates the IP-CAN session modification procedure with the PCRF. In this procedure, the PDN GW removes the routing address related to the removed BID associated with the IP-CAN session.
Step 5.
If the HA function is located in the PDN GW, as part of the IP-CAN session modification procedure initiated in step 3, the PCRF ensures that the relevant QoS rules for the SDFs are installed in the target BBERF. This is done by a GW control session and QoS rules provision procedure as specified in TS 23.203.
Step 6.
If in step 2 the HA has removed the BID associated with the 3GPP access and maintained the BID for the WLAN access, the PDN GW shall initiate the PDN GW Initiated PDN Disconnection procedure in 3GPP access as defined in TS 23.402, clause 5.6.2.2 or the PDN GW Initiated Bearer Deactivation procedure as defined in TS 23.401, clause 5.4.4.1. The PDN GW shall set the release cause to 'RAT changed from 3GPP to Non-3GPP' to avoid the MME remove the PDN GW ID from the HSS. In case of I-WLAN mobility architecture and the UE has removed the BID associated with the 3GPP access, the UE may initiate PDP Context Deactivation as described in TS 23.060.
If the BID associated with the WLAN access is removed, according to TS 23.402 the security associations between the UE and the HA should not be immediately deleted. As the security associations were created dynamically using IKEv2 they will be automatically deleted when they expire.
For I-WLAN mobility architecture, the H2 session between the HA and the AAA Server should not be immediately deleted. The H2 session will be deleted by the HA immediately after security associations are deleted. In case of I-WLAN mobility architecture, the UE may initiate release of the IKEv2 security association with the PDG according to TS 23.234.
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5.6  Addition of one access for multiple PDN connections to the same APNWord‑p. 21

When a UE having multiple PDN connections to the same APN via one access attaches to a second access, the UE needs to decide which of the multiple PDN connections the UE has would use both accesses simultaneously.
When the UE having multiple PDN connections to the same APN via a 3GPP access attaches to a WLAN, the UE shall perform DSMIPv6 procedures only for the PDN connections for which it will use IP flow mobility.
When the UE having multiple PDN connections to the same APN via the WLAN attaches to the 3GPP access, the UE should only establish the PDN connections for which it will use IP flow mobility. However, due to the restriction that the UE cannot indicate which PDN connection is to establish, the UE shall repeat UE PDN Connectivity Request until the desired PDN connections have been established and shall perform DSMIPv6 procedures for the desired PDN connections.
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5.7  Detach and PDN disconnection procedures

When the UE is attached to the same PDN through two accesses and a detach or PDN disconnection procedure is required, the following considerations apply:
When the UE is attached to I-WLAN architecture through 3GPP and WLAN accesses and a detach or PDN disconnection procedure is required, similar considerations as above apply with reference to the procedures described in TS 23.327 and TS 23.060.
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$  Change historyWord‑p. 22


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