Content for  TS 24.303  Word version:  18.0.0

Following a change of access, the UE configures an IP address on the target access system. The details of IP address configuration can be access specific. The handling of the received Binding Acknowledgement is the same as specified in subclause 5.1.2.4.

If the access network supports IPv6, as soon as the UE has received via a Router Advertisement at least an IPv6 prefix which is not present in its Prefix List, the UE shall perform the Home Link detection as specified in subclause 5.1.2.3. If the UE detects that it is moving from home link to foreign link, and if there is no security association existing with the HA, the UE shall perform the Security association establishment and Home Address assignment procedure with the HA as specified in subclause 5.1.2.2. Then the UE shall perform the initial binding registration and IPv4 Home Address assignment as specified in subclause 5.1.2.4. In order to maintain IP address preservation for the IPv4 address used in the home link, the UE shall include the IPv4 address used on the home link in an IPv4 Home Address option in the same Binding Update message. The IFOM capable UE configured for IFOM shall extend the Binding Update message as described in subclause 5.1.2.4. If the UE does not have an IPv4 Home Address but wants to configure one, the UE shall include the IPv4 Home Address option with the 0.0.0.0 address as specified in subclause 5.1.2.4. If the access network supports only IPv4, as soon as the UE has configured an IPv4 Care-of Address, the UE shall send a Binding Update tunnelled in UDP as specified in RFC 5555. The UE shall set the F flag to "0". The UE shall set the R flag to "1". Independent of an IPv6 or IPv4 access network the UE shall set the Key Management Capability (K) bit in the Binding Update message. If the UE receives, as response to an outstanding binding registration, a binding acknowledgment having a status code equal to 135 ("Sequence number out of window") and a sequence number different from the one used in the outstanding binding registration, the UE shall accept the binding acknowledgment and process it as specified in RFC 6275.

If the access network supports IPv6, as soon as the UE has received via a Router Advertisement at least an IPv6 prefix which is not present in its Prefix List, the UE shall perform the Home Link detection as specified in subclause 5.1.2.3. If the UE detects it is not attached to the home link, the UE shall send a Binding Update to the HA including the newly configured IP address as the Care-of Address in the Source IP address of the packet and optionally in the Alternate Care-of Address Option RFC 6275. The UE build the Binding Update message as specified in RFC 6275. If the UE has been assigned also an IPv4 Home Address and wants to update also the binding for it, the UE shall include the IPv4 Home Address option including the assigned IPv4 Home Address in the same Binding Update message. If the UE has been assigned also an IPv4 Home Address and wants to release it, the UE shall not include any IPv4 Home Address option in the same Binding Update. If the UE does not have an IPv4 Home Address but wants to configure one, the UE shall include the IPv4 Home Address option with the 0.0.0.0 address as specified in subclause 5.1.2.4. If the access network supports only IPv4, as soon as the UE has configured an IPv4 Care-of Address which is different from the previous Care-of Address, the UE shall send a Binding Update tunnelled in UDP as specified in RFC 5555. The UE shall set the F flag to "0". The UE shall set the R flag to "1". Independent of an IPv6 or IPv4 access network the UE shall set the Key Management Capability (K) bit in the Binding Update message. If the UE is an IFOM capable UE configured for IFOM, the UE extends the Binding Update with the following options:

1. the UE shall set the O (Overwrite) flag to "0";
2. the UE shall include a BID identifier mobility option in the Binding Update as specified in RFC 5648;
   • the UE shall set the BID field to the value registered with the Home Agent;
   • the UE shall set the BID-PRI field to assign the priority to the BID as indicated in RFC 6089;
   • if the newly configured IP address used as Care-of Address is an IPv6 address, the UE shall not insert any Alternate Care-of Address option in the Binding Update message;
   • if the newly configured IP address used as Care-of Address is an IPv4 address, the UE shall not insert any IPv4 Care-of Address option in the Binding Update message; and
   • the UE shall insert the newly configured IP address used as Care-of Address in the Care-of Address field of the BID identifier mobility option insertd in the Binding Update message;
3. the UE may create one or more routing rules. For each routing rule that the UE wants to register with the HA, the UE shall include a FID mobility option containing one traffic selector as specified in RFC 6089. Traffic selectors are defined in RFC 6088:
   • the UE shall set the FID field to an arbitrary value;
   • the UE shall set the FID-PRI field to assign the priority to the routing filter as indicated in RFC 6089;
   • the UE shall include a Binding Reference suboption as indicated in RFC 6089. The value assigned to the BID identifies the routing address that the UE wants to use to exchange the packets matching the routing filters; and
   • traffic selector suboption shall be set as specified in RFC 6089 and RFC 6088. The parameters described in the traffic selector suboption represent the routing filter that corresponds to the routing rule that the UE wants to register with the HA;
4. The UE may insert a flow summary mobility option (as described in RFC 6089).
   • 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
5. 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 RFC 6089.
   • 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 RFC 6089; and
   • the UE shall include a Binding Reference suboption as indicated in RFC 6089. The value assigned to the BID identifies the routing address that the UE wants to use to exchange the packets matching the routing filters.

The UE shall process the binding acknowledge message as described in subclause 5.1.2.4.

If the access network supports IPv6, as soon as the UE has received via a Router Advertisement message at least an IPv6 prefix which is not present in its Prefix List, the UE shall perform the Home Link detection as specified in subclause 5.1.2.3 to detect if the UE is attaching to the home link. If the UE detects it is attached to the home link and there is a valid DSMIPv6 Binding Update list entry at the UE, the UE shall send a Binding Update with the Lifetime field set to "0" in order to remove the binding at the HA, as specified in RFC 6275. If an IPv4 home address was assigned to the UE, as an optimization the UE may not include the IPv4 home address option as the binding for the IPv4 home address will be removed by the HA. Independent of an IPv6 or IPv4 access network the UE shall set the Key Management Capability (K) bit in the de-registration Binding Update message. The UE may preserve the IKEv2 session in order to avoid re-establishing the session when the next handover occurs. If there is not a safe assumption that the UE will remain in the home link (e.g. switching off the non-3GPP radio interface in case of a dual radio terminal), the UE should preserve the IKEv2 session. If the UE receives a Binding Revocation Indication message from the HA while there is an outstanding unacknowledged Binding Update with Lifetime field set to "0" message, the UE need not send a Binding Revocation Acknowledgement as specified in subclause 5.4.2.1.

In case of UE handover from home link to foreign link, the HA shall support the initial registrstion procedure as specified in subclause 5.1.3. The error codes used in the Binding Acknowledgement are the same as specified in subclause 5.1.3.2.

When the HA receives a Binding Update from the UE, the HA shall validate it as described in RFC 6275 and in RFC 5555. If the validation is successful, the HA shall update the binding cache entry related to the Home Address included in the Binding Update. If the Binding Update is an IPv6 packet, with the Alternate Care-of Address option present, the HA shall verify the correctness of the Alternate Care-of Address option. If the Care-of Address specified in the Alternate Care-of Address option and in the Source Address field of the IPv6 header of the Binding Update packet are different, the HA shall reject the request by returning a Binding Acknowledgement with status code 128. If the option is valid, the HA shall update the binding cache entry with the Care-of Address in the Source Address of the IPv6 header. If the Binding Update outer header is an IPv4 header and the IPv4 Care-of Address in the IPv4 Care-of Address option is the same as the IPv4 address in the Source Address in the outer IPv4 header, the HA shall update the binding cache entry with the Care-of Address in the IPv4 Care-of Address option and shall send a Binding Acknowledgment encapsulated in IPv4 as specified in RFC 5555. If in the received Binding Update the IPv4 Care-of Address in the IPv4 Care-of Address option is not the same as the IPv4 address in the Source Address in the outer IPv4 header then a NAT was in the path. This information shall be included in the Binding Acknowledgement within a NAT Detection option with the F bit set. The Binding Acknowledgment shall be encapsulated in UDP and the binding cache updated as specified in RFC 5555. If the Binding Update contains an IPv4 Home Address option with an IPv4 Home Address previously assigned, the HA shall update also the binding cache entry related to the IPv4 Home Address to the UE. If the Binding Update contains no IPv4 Home Address option, the HA shall remove the binding cache entry related to the IPv4 Home Address of the UE if present. If the Binding Update contains an IPv4 Home Address option with the 0.0.0.0 IPv4 address, the HA shall assign an IPv4 Home Address to the UE, including an IPv4 Address Acknowledgement option in the Binding Acknowledgement message. The error codes used in the Binding Acknowledgement are the same as specified in subclause 5.1.3.2. If the Binding Update contains a BID mobility option and (optionally) a Flow summary mobility option, the HA shall process the received Binding Update message and send a Binding Acknowledgement message as described in subclause 5.1.3.2. If the Key Management Mobility Capability (K) bit is set in the Binding Update and the HA supports the feature, the HA updates its IKEv2 security associations to include the UE's Care-of Address as the peer address and the Binding Acknowledgement is returned with the K bit set. The HA shall set the R bit to "1" in the Binding Acknowledgement.

When a UE hands over from a foreign link to its home link, a network based mobility protocol (PMIPv6 or GTP) in the home link creates a binding cache entry for the UE. The DSMIPv6 binding cache entry that was created by the UE on the foreign link shall not be overwritten. The downlink UE packets shall be processed by the HA based on the DSMIPv6 binding cache entry before the DSMIPv6 binding cache entry is removed. The DSMIPv6 binding cache entry shall be removed when a Binding Update with lifetime field set to "0" is received by the HA from the UE. The HA shall process the message as per RFC 5555 and RFC 6275, removing the associated binding cache entry and sending the Binding Acknowledge message with the Status field set to "0" (Binding Update accepted). If an IPv4 home address was assigned to the UE, the HA shall also remove the binding for the IPv4 home address tied to the IPv6 home address included in the Binding Update. If the HA decides to remove the DSMIPv6 binding cache entry of the UE, prior to receiving a binding update with lifetime set to "0" from the UE , the HA shall send a Binding Revocation Indication message as specified in subclause 5.4.3.1.

Upon receiving a Binding Revocation Indication (BRI) message according to RFC 5846 from the HA, the UE first shall perform the required validity checks on the BRI according to RFC 5846. The UE shall send a Binding Revocation Acknowledgement (BRA) as specified in RFC 5846. In this message the UE shall set the status field to 'Success' to reflect that it has received the BRI message. The BRA message may be tunnelled in UDP or IPv4 as specified in subclause 5.1.2.4 for Binding Update messages. The UE then shall remove the entry identified in the BRI as deregistered from its binding update list and shall use the procedures defined in RFC 5996 to remove the IPsec security associations associated with the DSMIPv6 registration as described in subclause 5.4.2.2.

To detach from a specific PDN to which it is connected through a DSMIPv6 session, the UE shall send a Binding Update with the Lifetime field set to 0 as specified in RFC 6275. The UE shall use the procedures defined in the IKEv2 protocol in RFC 5996 to remove the IPsec security associations associated with the DSMIPv6 registration. The UE shall close the security associations associated with the DSMIPv6 registration and instruct the HA to do the same by sending the INFORMATIONAL request message including a DELETE payload. The Protocol ID in the DELETE payload shall be set to "1" (IKE) to indicate that all IPsec ESP security associations that were negotiated within the IKEv2 exchange shall be deleted.

As soon as it receives a trigger for network-initiated detach procedure (see TS 29.273) the HA shall send a Binding Revocation Indication (BRI) message according to RFC 5846 to the UE. The message shall contain the Home Address, corresponding to the PDN connection which shall be removed. The HA shall set the P (Proxy Binding) bit to 0 (Not Proxy MIPv6 binding), G bit (Global) to 0 (only the PDN Connection specified by the HoA is removed) and V bit (IPv4 HoA Binding Only) to 0 (Not to terminate the IPv4 Home Address binding only). The revocation trigger value shall be set to 1 (Unspecified). The HA shall include the UE home address in the Type 2 routing header as per RFC 5846 and shall not include any mobility option. The HA shall not include a BID option in the BRI message. The BRI message may be tunnelled in UDP or IPv4 as specified in subclause 5.1.3.2 for Binding Acknowledgement messages. The HA shall follow procedures according to RFC 5846 to await the receipt of a Binding Revocation Acknowledgment (BRA) message from the UE. These procedures are based on the timer MINDelayBRIs defined in RFC 5846. The HA shall not remove the entry from its binding cache before receiving the BRA. If the HA receives a Binding Update with Lifetime set to 0 after initiating the network-initiated detach procedure, the HA should treat the BU as acknowledgement to the BRI for the purposes of completing the revocation procedures that are defined in RFC 5846; in this case, the HA shall remove the respective entry in its binding cache, deleting the timer MINDelayBRIs and respond with a Binding Acknowledgement according to RFC 5555 and RFC 6275.

When the HA receives a Binding Update with the Lifetime field set to 0, it shall delete any existing entry for the Home Address included in the Binding Update. Then the HA shall send a Binding Acknowledgement as specified in RFC 5555 and RFC 6275. On receipt of the INFORMATIONAL request message including a DELETE payload indicating that the UE is deleting the IPsec security associations associated with the DSMIPv6 registration, the HA shall close the IKE security association, and all IPsec ESP security associations that were negotiated within it towards the UE.