5 I-WLAN mobility procedures

24.3273GPPGeneral Packet Radio System (GPRS) and 3GPP I-WLAN aspectsMobility between 3GPP Wireless Local Area Network (WLAN) interworking (I-WLAN) and 3GPP systemsRelease 12Stage 3TS

5.1 Initial attach

5.1.1 General

The attach procedure is performed by the UE when connecting to GPRS systems or to 3GPP I-WLAN. After completion of the attach procedure, H1 PDN attach may be performed. Through H1 PDN attach, the UE receives all the required parameters and information enabling the continuity of the session. The information is retrieved through the following procedures:

– Discovery of the home agent address: the UE needs to discover the IPv6 address and eventually the IPv4 address of the HA.

– Security association establishment: if not on its home link, the UE needs to establish IPsec security associations with the HA in order to secure the DSMIPv6 signalling as specified in 3GPP TS 33.402 [14]. IKEv2, defined in IETF RFC 4877 [8], is used to establish IPsec security association.

– IPv6 home network prefix assignment and home link detection: the UE needs to be assigned an IPv6 Network Prefix of its home network in order to configure a global unicast home address to be used in DSMIPv6 and to perform the home link detection.

IPv4 home address assignment: optionally, a dual-stack UE can also request to be assigned an IPv4 home address to be used for example for IPv4-only applications.

– Initial binding registration: unless the home link detection procedure indicates the UE is at home, the UE sends a Binding Update message to perform its initial registration with the HA.

If the UE is an IFOM capable UE, the DSMIPv6 H1 PDN attach includes also the IFOM capability discovery.

5.1.2 UE procedures

5.1.2.1 General

When connecting to GPRS systems, the UE shall perform the GPRS attach procedure and establish a PDP context as described in 3GPP TS 24.008 [4]. During the PDP context activation procedure, the UE may request the HA IP address(es) and the Home Network Prefix. If the home network prefix is pre-configured or obtained from the GGSN, the UE shall perform the home link detection procedure as described in subclause 5.1.2.4. If the UE is on its home link, the UE shall not perform the H1 PDN attach. If the UE is not on the home link or does not have a HNP yet, the UE shall discover the HA address as described in subclause 5.1.2.2 if the UE does not have the HA address, and then shall perform the H1 PDN attach procedure.

When connecting to the 3GPP I-WLAN, the UE shall perform the I-WLAN automatic network selection procedure as described in 3GPP TS 24.234 [5]. During the tunnel setup to the PDG, the UE may request a HA IP address or a HNP, or both, as described in annex B. If the home network prefix is pre-configured in the UE or obtained from the PDG as described in annex B, the UE shall perform the home link detection procedure as described in subclause 5.1.2.4. If the UE is on its home link, the UE shall not perform the H1 PDN attach. If the UE is not on the home link or does not have a HNP yet, the UE shall discover the HA address as described in subclause 5.1.2.2 if the UE does not already have the HA address, and then perform the H1 PDN attach procedure.

The H1 PDN attach procedure involves the following tasks:

– IPsec security associations’ establishment and IPv6 home network prefix assignment;

– home link detection, if this procedure was not performed during the attachment; and

– initial binding registration if the UE is not at its home link.

5.1.2.2 Discovery of the Home Agent address

The first procedure the UE needs to perform for DSMIPv6 initial attach is the discovery of the node acting as the HA.

The UE discovers the IPv6 address and optionally the IPv4 address of the HA in one of the three following ways:

– via DNS as defined in 3GPP TS 24.303 [3];

– during the PDP context activation procedure in GERAN or UTRAN accesses via the Protocol Configuration Options as defined in 3GPP TS 24.008 [4] if the HA IP address is available in the GGSN; or

– via IKEv2 during tunnel setup with PDG for 3GPP I-WLAN as defined in annex B if the HA IP address is available in the PDG.

If the HA IP address(es) are available in the GGSN, the GGSN shall return the HA IP address(es) in the Protocol Configuration Options during the PDP context activation procedure when attaching to the GERAN or UTRAN accesses. If the HA IP address(es) are not available in the GGSN, the UE shall discover the HA IP address(es) by DNS if the UE wants to perform the handover to 3GPP I-WLAN.

If the UE requests the HA IP address(es) during the IPsec tunnel setup to PDG in 3GPP I-WLAN connection and if the HA IP address(es) are available in the PDG, the PDG shall return the HA IP address(es) in IKEv2 configuration payload attributes as defined in annex B. If the HA IP address(es) are not available in the PDG, the UE shall discover the HA IP address(es) by DNS before performing the H1 PDN attach.

The UE shall support the HA discovery based on DNS and on Protocol Configuration Options. The UE may support the HA discovery based on IKEv2.

The HA IP address(es) may also be pre-configured in the UE.

5.1.2.2a IFOM capability discovery

An IFOM capable UE shall perform HA IFOM capability discovery, i.e. an IFOM capable UE shall discover whether the HA supports IFOM or not. The procedures for IFOM capability discovery are the same as those defined in 3GPP TS 24.303 [3].

5.1.2.3 Security association establishment and IPv6 home network prefix assignment

The UE shall perform the security association establishment with the HA as specified in 3GPP TS 24.303 [3]. For this procedure the UE shall support IKEv2 protocol and EAP over IKEv2 as described in IETF RFC 5996 [9]. The detailed procedure and supported extensions for this step are specified in 3GPP TS 24.303 [3]. The UE may use either EAP-SIM or EAP-AKA for authentication purposes.

During the IKEv2 exchange, the UE shall request an IPv6 home network prefix as specified in 3GPP TS 24.303 [3]. The UE shall then auto-configure an IPv6 home address from the received prefix and create child SA as specified in 3GPP TS 24.303 [3].

In the IKEv2 signalling the UE should indicate the APN the UE wants to connect to in the IDr payload as specified in 3GPP TS 24.303 [3].

The UE shall use the PDN Identifier notify payload as described in 3GPP TS 24.303 [3].

5.1.2.4 Home link detection

The DSMIPv6 home link detection function is used by the UE to detect if, for a specific PDN, an access interface is on the home link from DSMIPv6 perspective. The home link detection function for a specific PDN connection shall be performed whenever the UE receives a new IPv6 prefix, either at initial attach or after a handover.

The UE is informed of the IPv6 prefix associated with a specific access interface. If the UE is connected to GPRS systems, the UE knows the IPv6 prefix via the IPv6 address autoconfiguration as described in 3GPP TS 29.061 [6]. If UE is connected to the 3GPP I-WLAN, it knows the IPv6 prefix via IPv6 address autoconfiguration as described in 3GPP TS 29.161 [7].

In the scenarios considered in this specification, the Home Network Prefix associated to the PDN connection can be assigned:

  • via Protocol Configuration Options from the GGSN in GPRS systems as specified in 3GPP TS 24.008 [4];
  • via IPsec security associations bootstrap with the PDG in I-WLAN as specified in annex B;
  • via the establishment of IPsec security associations with the HA as specified in 3GPP TS 24.303 [3] subclause 5.1.2.2; or
  • the HNP may also be pre-configured in the UE.

NOTE: If a pre-configured HNP is available, the UE can use it for home link detection. However the UE cannot use it for the IPv6 address autoconfiguration.

The home link detection procedure performed by the UE is specified in 3GPP TS 24.303 [3].

If the UE detects it is in the home link for this specific PDN over the access interface, the UE shall not perform the H1 PDN attach. If the UE detects it is not on the home link, the UE shall perform IKEv2 procedure for security associations setup and IPv6 prefix and optionally IPv4 HA assignment if the UE does not have a valid security association with the HA, and then the UE shall send a Binding Update as specified in 3GPP TS 24.303 [3].

If the IFOM capable UE performs the Home Network Prefix discovery via Protocol Configuration Option, the IFOM capable UE shall perform in the ACTIVATE PDP CONTEXT REQUEST message both Home Network Prefix discovery and the IFOM capability discovery.

5.1.2.5 Initial binding registration and IPv4 home address assignment

After establishing the security association and obtaining the IPv6 home network prefix and after performing the home link detection, if not on the home link, the UE shall send a Binding Update message as specified in 3GPP TS 24.303 [3] to register its IPv6 home address with its care-of address.

The UE may also request in the Binding Update an IPv4 home address based on the procedure specified in 3GPP TS 24.303 [3].

The initial binding registration procedure for IFOM capable UE configured for IFOM is described in 3GPP TS 24.303 [3].

5.1.3 Network procedures

5.1.3.1 GPRS systems aspects

During the PDP context activation procedure in GERAN or UTRAN accesses, if the HA IP address(es) and the HNP are available in the GGSN, the GGSN shall provide them to the UE via the Protocol Configuration Options as defined in 3GPP TS 24.008 [4]. If the HA is IFOM capable and the UE performed HA IFOM capability discovery within the Protocol Configuration Options information element, the GGSN shall provide the IFOM capability indicator to the UE via the Protocol Configuration Options as defined in 3GPP TS 24.008 [4].

5.1.3.2 3GPP I-WLAN aspects

During the IPsec tunnel establishment, if the UE requests the HA IP address(es) or the HNP, or both, and if they are available in the PDG, the PDG shall provide them to the UE via the dedicated IKEv2 attributes as defined in annex B. The HA IP address(es) are referred to the W-APN for which the IPsec tunnel is set-up and which was inserted in the "IDr" payload of the IKE_AUTH request message to the PDG.

5.1.3.3 HA procedures

5.1.3.3.1 Security association establishment and IPv6 home network prefix assignment

The HA shall support the IKEv2 protocol and EAP over IKEv2 as described in IETF RFC 5996 [9]. If the HA is IFOM capable, the HA shall perform IFOM capability discovery as part of security association procedure. The HA procedures for security association establishment, IPv6 home network prefix assignment and IFOM capability discovery are specified in 3GPP TS 24.303 [3].

5.1.3.3.2 Initial binding registration and IPv4 home address assignment

The HA procedures for initial binding registration and IPv4 home address assignment are specified in 3GPP TS 24.303 [3].

In addition, if the HA has the GGSN APN information, the HA shall send the APN to the UE in the Binding Acknowledgement message using the 3GPP Vendor-Specific Access Point Name as specified in annex A.

5.2 Handover

5.2.1 General

The handover procedure is performed by the UE when it is moving from GERAN or UTRAN accesses to 3GPP I-WLAN and vice-versa.

5.2.2 Handover from GPRS systems to 3GPP I-WLAN

5.2.2.1 UE procedures

When the UE is connected to the GPRS systems and wants to move to 3GPP I-WLAN, the UE if it has not already selected a PLMN via I-WLAN shall perform:

1) WLAN UE I-WLAN Selection procedure as described in subclause 5.2.1 in 3GPP TS 24.234 [5];

2) automatic PLMN selection as described in subclause 5.2.4 in 3GPP TS 24.234 [5].

The UE shall then:

a) initiate the tunnel establishment procedure towards the PDG as described in 3GPP TS 24.234 [5] if it has not already done so, and

b) perform the home link detection as described in subclause 5.1.2.4:

– If the UE is not on the home link and does not know the HA IP address, it shall perform the HA discovery procedure as specified in subclause 5.1.2.2 and then perform the H1 PDN attach procedure with the HA. If the UE already knows the HA IP address but has not established security associations with the HA, the UE shall perform the H1 PDN attach with the HA after the attachment to the 3GPP I-WLAN. If the UE has already a valid binding at the HA, the UE shall send a Binding Update message to inform the HA of its new Care-of-Address, as specified in 3GPP TS 24.303 [3]. During the handover, the UE keeps using the GERAN or UTRAN accesses.

– If the UE is on the home link, the UE shall send a Binding Update with lifetime set to 0 to remove the binding at the HA as specified in 3GPP TS 24.303 [3].

Once the handover is completed, the UE should deactivate the PDP context and may initiated a detach procedure in the GPRS system.

The additional procedures to be performed in case of handover to 3GPP I-WLAN for IFOM capable UE configured for IFOM are described in the handover subclause of 3GPP TS 24.303 [3].

5.2.2.2 Network procedures

5.2.2.2.1 3GPP I-WLAN aspects

Once the UE is connected to the 3GPP I-WLAN and if the UE is on the home link for the PDN connection, the 3GPP I-WLAN shall ensure that the UE obtains the IP address, which is the same as the Home Address, during the establishment of the IPsec tunnel with the PDG.

5.2.2.2.2 HA aspects

Upon receiving of the Binding Update message from the UE, the HA shall behave as described in 3GPP TS 24.303 [3].

5.2.3 Handover from 3GPP I-WLAN to GPRS systems

5.2.3.1 UE procedures

When the UE is connected to the 3GPP I-WLAN and wants to move to GPRS systems, the UE shall perform the attach and PDP context activation procedures as described in 3GPP TS 24.008 [4]. The APN provided by the UE in the PDP context activation procedure is used by the SGSN to allocate the GGSN. When the HA and the GGSN are collocated, the UE shall be connected to the GGSN that contains the HA function allocated in 3GPP I-WLAN. For that purpose, the UE shall use the received APN in the Binding Acknowledgement message during H1 PDN attach for performing the PDP context activation procedure. If no APN is received in the Binding Acknowledgement message during H1 PDN attach, the UE shall use the pre-configured APN, if available, for performing the PDP context activation procedure.

Once the UE is attached to the GPRS system and after performing the PDP context activation procedure, it will receive a new PDP address as a Care-of-Address. The UE shall then perform the home link detection procedure as specified in subclause 5.1.2.4:

– If the UE is not in the home link and does not know the HA address, the UE shall perform the HA address discovery procedure as specified in subclause 5.1.2.2 and then perform the H1 PDN attach procedure with the HA. If the UE already knows the HA address but does not have a valid binding at the HA, the UE shall perform the H1 PDN attach procedure with the HA after the attachment to the GPRS system. If the UE has already a valid binding at the HA, the UE shall send a Binding Update message as specified in 3GPP TS 24.303 [3].

– If the UE is on the home link, the UE shall send a Binding Update with lifetime set to 0 to remove the binding at the HA as specified in 3GPP TS 24.303 [3].

Once the handover is completed, the UE should initiate tunnel disconnection from the 3GPP I-WLAN.

The additional procedures to be performed in case of handover to GPRS systems for IFOM capable UE configured for IFOM are described in the handover subclause of 3GPP TS 24.303 [3].

5.2.3.2 Network procedures

5.2.3.2.1 GPRS systems aspects

Once the UE is connected to the GPRS system and if it is on the home link for a PDN connection, the GPRS system shall ensure that the UE keeps the same Home Address during the PDP context activation procedure.

5.2.3.2.2 HA aspects

Upon receiving of the Binding Update message from the UE, the HA shall behave as described in 3GPP TS 24.303 [3].

5.3 Detach

5.3.1 General

The DSMIPv6 detach is performed by the UE to tear down the IP tunnel between the UE and the HA and the respective IKEv2 session or by the network to inform the UE that it does not have access to a specific PDN through DSMIPv6 any longer. After the detach procedure, the UE still has IP connectivity provided by the access network.

5.3.2 UE procedures

5.3.2.1 Network-initiated detach

The network-initiated detach is based on the usage of the Binding Revocation Indication (BRI) message. When the UE receives a BRI, it shall proceed as described in 3GPP TS 24.303 [3].

5.3.2.2 UE-initiated detach

To detach from a specific PDN to which it is connected through a DSMIPv6 session, the UE shall de-register the DSMIPv6 binding and tear down the IPsec security association as specified in 3GPP TS 24.303 [3].

5.3.3 Network procedures

5.3.3.1 GPRS systems aspects

Network detachment of the UE connected to GPRS systems is performed as described in 3GPP TS 24.008 [4]. This procedure is independent from H1 reference point procedures.

5.3.3.2 3GPP I-WLAN aspects

Network detachment of the UE connected to a 3GPP I-WLAN is performed as described in 3GPP TS 24.324 [5]. This procedure is independent from H1 reference point procedures.

5.3.3.3 HA aspects

Once the HA receives a trigger for network-initiated detach procedure or a Binding Update with lifetime field set to 0, the HA shall proceed as described in the Dual-Stack Mobile IPv6 detach procedure in 3GPP TS 24.303 [3].

5.4 Protection of DSMIPv6 tunnel traffic

5.4.1 General

UE and HA may create a child security association using the IKEv2 session established as described in subclause 5.1.2.3. This child security association is used to cipher or integrity protect, or both, all data traffic exchanged within the DSMIPv6 tunnel. The profiles for tunnel mode IPsec ESP are defined in 3GPP TS 33.234 [19]. The procedure is initiated by the HA and may be initiated at any time after the security association between UE and HA has been set up. The support of this procedure is optional for both the HA and the UE.

5.4.2 UE procedures

When the UE receives a CREATE_CHILD_SA request from the HA with selectors indicating the DSMIPv6 tunnel traffic, the UE should reply with a CREATE_CHILD_SA response selecting the preferred transform proposed by the HA as specified in IETF RFC 5996 [9].

If the child SA is created successfully, the UE shall start ciphering or integrity protecting, or both, all the uplink packets in the DSMIPv6 tunnel as negotiated with the HA during the CREATE_CHILD_SA procedure.

The UE may stop ciphering or integrity protecting, or both, the DSMIPv6 tunnel traffic. In order to do that, the UE shall delete the respective child security association by sending an INFORMATIONAL request message including the DELETE payload as specified in IETF RFC 5996 [9]. The protocol ID shall be set to 3 in order to indicate that only the ESP SA shall be removed.

5.4.3 HA procedures

After establishing the IPsec security association with the UE as described in subclause 5.1.3.3, the HA may optionally trigger the creation of a child security association to protect the traffic send via the DSMIPv6 tunnel.

In order to activate the protection of DSMIPv6 tunnel traffic, the HA shall initiate the creation of a child security association sending a CREATE_CHILD_SA request message to the UE. In the CREATE_CHILD_SA message the HA shall request for an ESP security association; the HA shall also set the SA payload depending if integrity protection or ciphering, or both, are needed as described in IETF RFC 5996 [9]. The traffic selectors shall be set as described in subclause 5.2.4 of IETF RFC 3776 [11].

If the child security association is created successfully, the HA shall start ciphering or integrity protecting, or both, all the downlink packets in the DSMIPv6 tunnel as negotiated with the UE during the CREATE_CHILD_SA procedure.

At any time the HA may stop ciphering or integrity protecting, or both, the DSMIPv6 tunnel traffic. In order to do that, the HA shall delete the respective child security association by sending an INFORMATIONAL request message including the DELETE payload as specified in IETF RFC 5996 [9]. The protocol ID shall be set to 3 in order to indicate that only the ESP SA shall be removed.

5.5 Attach to an additional system

5.5.1 General

The operations defined within this subclause apply to IFOM capable UE configured for IFOM and to HA supporting IFOM.

The attach to an additional system procedure is performed by a UE that has already established an active PDN connection through a system.

There are three possible scenarios:

– The existing system is a home link and the added one is a foreign link;

– The existing system is a foreign link and the added one is a home link; or

– The existing system is a foreign link and the added one is a foreign link.

The following can be performed during the attach to an additional system procedure:

– system specific procedure in order to connect and to configure an IP address for the added system. It consists of the UE performing the GPRS attach procedure and establishing a PDP context as described in 3GPP TS 24.008 [4] or the UE performing the I-WLAN automatic network selection procedure as described in 3GPP TS 24.234 [5];

– discovery of the Home Agent address, if the HA IP address was not obtained upon the attachment to the first system or when performing the system specific procedure;

– security associati on establishment between the UE and the HA, if there was no security association established upon the attachment to the first system;

– home link detection; and

– exchange of the Binding Update and the Binding Acknowledge messages between the UE and the HA including the BID mobility option(s) and the FID mobility option(s).

5.5.2 UE procedures

5.5.2.1 General

When attaching to an additional system, the UE is already attached to either a home link or a foreign link and discovers a new system. The UE requests the discovery of the HA IP address, as described in subclause 5.1.2.2 in case the UE does not already have it. The UE then initiates the home link detection as specified in subclause 5.1.2.4 to determine if the new system is a foreign link or a home link. If it is a home link, the UE performs the procedure described in subclause 5.5.2.2. If it is a foreign link, the UE performs the procedure described in subclause 5.5.2.3.

5.5.2.2 Attach to an additional system acting as a home link

The procedures for attach to an additional system acting as a home link are the same as the UE procedures for attach to an additional access acting as a home link described in 3GPP TS 24.303 [3].

5.5.2.3 Attach to an additional system acting as a foreign link

When the UE detects that the additional system acts as a foreign link, if the initial system where the UE is already attached acts as a home link, the UE procedures are the same as the UE procedures for attach to an additional access acting as a foreign link specified in 3GPP TS 24.303 [3].

If the initial system where the UE is already attached acts as a foreign link, the UE procedures are the same as the procedures described in subclause 5.1.2.5 with the following exceptions:

a) the O (Overwrite) flag shall be set to "0";

b) the UE may insert a flow summary mobility option (as described in IETF RFC 6089 [21]).

– If the UE wants to keep some routing rules previously registered unmodified, i.e. no flow handover, the UE lists the values of the FIDs identifying the routing rules that the UE wants to keep unmodified in the flow summary mobility option; and

– If the UE wants to remove one or more previously registered routing rules, the UE does not include in the flow summary mobility option the FIDs identifying the routing rules that the UE wants to remove; and

c) the UE may modify one or more routing rules with the HA. For each routing rule that the UE wants to modify, the UE shall include a FID mobility option as specified in IETF RFC 6089 [21].

– the UE shall set the FID field to the value identifying the routing filter the UE wants to handover;

– the UE shall set the FID-PRI field to assign the priority to the BID as indicated in IETF RFC 6089 [21]; and

– the UE shall include a Binding Reference suboption as indicated in IETF RFC 6089 [21]. The value assigned to the BID identifies the routing address that the UE wants to use to exchange the packets matching the routing filters.

When the UE receives the Binding Acknowledgment from the HA, the UE shall process the Binding Acknowledgment as specified in subclause 5.1.2.5.

5.5.3 HA procedures

5.5.3.1 General

The following subclauses describe the HA procedures for the case when a UE is attaching to an additional system.

5.5.3.2 Attach to an additional system acting as a home link

The HA procedures for attach to an additional system acting as a home link are the same as the HA procedures for attach to an additional access acting as a home link described in 3GPP TS 24.303 [3].

5.5.3.3 Attach to an additional system acting as a foreign link

The HA procedures for attach to an additional system acting as a foreign link depends whether the first system where the UE is connected, acts as a home link or foreign link:

– if the initial system where the UE is already attached acts as a home link, the HA procedures are the same as the HA procedures for attach to an additional access acting as a foreign link specified in 3GPP TS 24.303 [3]; and

– if the initial system where the UE is already attached acts as a foreign link, the HA process the received Binding Update message as specified in IETF RFC 5648 [20], IETF RFC 6089 [21] and IETF RFC 6088 [22].

5.6 Inter-system flow mobility

5.6.1 General

The operations defined within this subclause apply to IFOM capable UE configured for IFOM and to HA supporting IFOM.

The inter-system flow mobility is performed when the UE has already established a PDN connection through multiple systems. The UE has previously registered one or more routing rules with the HA in order to route the packets exhcanged through the access systems.

This procedure enables the UE to update one or more routing rules with the HA, e.g. by changing the system through which some routing filters were previously routed. This procedure consists on exchanging a Binding Update and a Binding Acknowledge messages with a BID and a FID options between the UE and the HA including the updated routing rules.

5.6.2 UE procedures

The UE procedures for the inter-system flow mobility are the same as the UE procedures for inter-access flow mobility defined in 3GPP TS 24.303 [3].

5.6.3 HA procedures

The HA procedures for the inter-system flow mobility are the same as the HA procedures for inter-access flow mobility defined in 3GPP TS 24.303 [3].

5.7 UE-initiated removal of a system from a PDN connection

5.7.1 General

The operations defined within this subclause apply to IFOM capable UE configured for IFOM and to HA supporting IFOM.

The UE-initiated removal of a system from a PDN connection procedure is performed by a UE which has a PDN connection through multiple systems and which wants to stop using one system for this PDN connection. This procedure consists on exchanging a Binding Update and a Binding Acknowledge messages between the UE and the HA.

Three scenarios are possible:

– The removed system is a home link and the maintained one is a foreign link;

– The removed system is a foreign link and the maintained one is a foreign link, or

– The removed sytem is a foreign link and the maintained one is a home link.

5.7.2 UE procedures

5.7.2.1 General

The removal of a system from a PDN connection is performed by a UE attached to multiple systems. The UE sends a Binding Update message in order to update the HA binding cache removing the entry corresponding to the removed system.

If the removed system is a home link, the UE follows the procedure as specified in subclause 5.7.2.2. If the removed system is a foreign link, the UE follows the procedure as specified in subclause 5.7.2.3.

5.7.2.2 Removal of a system acting as a home link

The procedures for removal of a system acting as a home link are the same as the UE procedures for UE-initiated removal of a home link access from a PDN connection described in 3GPP TS 24.303 [3].

5.7.2.3 Removal of a system acting as a foreign link

If the UE removes a system acting as a foreign link from a specific PDN connection and maintains the connection to the PDN through the foreign link, the UE shall perform one of the following operations:

(a) the UE sends a Binding Update message with the Lifetime field set to 0 as specified in IETF RFC 5555 [10] and IETF RFC 6275 [12] and with a BID mobility option. The UE populates the BID mobility option as follows (see IETF RFC 5648 [20]):

– the BID field is set to the BID corresponding to the system the UE wants to remove;

– the H flag is set to 0; and

– the Care-of Address field is in the BID mobility options omitted;

or:

(b) the UE sends a Binding Update message as indicated in subclause 5.1.2.5 with the following additions:

– the Binding Update message shall be exchanged through the maintained system;

– the BID field is set to the value identifying the maintained system; and

– the Care-of Address field in the BID mobility options is omitted.

NOTE: The choice of the operation to follow is up to UE implementation.

If the UE removes a system acting as a foreign link from a specific PDN connection and maintains the connection to the PDN through the home link, the UE shall send a Binding Update message with the lifetime field set to 0 as specified in subclause 5.3.2.2. If the UE decides to close the security association set up with the HA, the UE shall send the INFORMATIONAL request message including a DELETE payload as specified in subclause 5.3.2.2.

5.7.3 HA procedures

5.7.3.1 General

The following subclauses describe the HA procedures for the case when the UE initiates the removal of a system from a PDN connection.

5.7.3.2 Removal of a system acting as a home link

In case of removal of asystem acting as a home link from a PDN connection executed by the UE, the HA shall perform the following operations:

– If the lifetime field of the received Binding Update is set to 0, the HA processes the received Binding Update message as described in IETF RFC 5555 [10] and IETF RFC 6275 [12] and IETF RFC 5648 [20]; and

– If the lifetime field of the received Binding Update is not set to 0, the HA shall only keep the entry corresponding to the remaining binding in its binding cache. In addition, the HA shall process the Binding Update message and populate the Binding Acknowledge message as specified in the 3GPP TS 24.303 [3].

5.7.3.3 Removal of a system acting as a foreign link

In case of removal of a system acting as a foreign link from a PDN connection executed by the UE, the HA shall perform the following operations:

– if the lifetime field of the received Binding Update is set to 0, the HA shall delete any existing entry for the home address in the binding cache and shall send a Binding Acknowledge message to the UE as specified in the IETF RFC 5555 [10] and IETF RFC 5648 [20]. In addition, if the received Binding Update message contains a BID mobility option, the HA shall validate and process the Binding Update message as described in IETF RFC 5648 [20]; and

– if the lifetime field of the received Binding Update is not set to 0, the HA performs the same procedures described in subclause 5.1.3.3.2.

5.8 Network-initiated removal of a system from a PDN connection

5.8.1 General

The operations defined within this subclause apply to IFOM capable UE configured for IFOM and to HA supporting IFOM.

The following subclauses describe the procedures performed by the UE and the HA in order to remove one system from a PDN connection initiated by the HA.

Three scenarios are possible:

– the removed system is a foreign link and the maintained system is a home link;

– the removed system is a foreign link and the maintained system is a foreign link; or

– the removed system is a home link and the maintained system is a foreign link.

5.8.2 UE procedures

When receiving the BRI message without a BID mobility option from the HA, the UE shall process it and send a BRA message to the HA as described in subclause 5.3.2.1.

When receiving the BRI message with a BID mobility option from the HA, the UE shall process it and send a BRA message to the HA as described in the 3GPP TS 24.303 [3]. The UE shall remove the entry corresponding to the BID mobility option included in the BRI from its binding update list.

5.8.3 HA procedures

In order to remove a foreign link access and maintain the home link access from a PDN connection triggered by the network, or to remove the home link and maintain the foreign link from a PDN connection triggered by the network, the HA shall send a Binding Revocation indication message to the UE as described in 3GPP TS 24.303 [3].

In addition, in order to remove a foreign link and maintain another foreign link from a PDN connection, the HA shall include a BID mobility option of the removed foreign link access in the BRI message sent to the UE as described in IETF RFC 5648 [20].

Annex A (normative):
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