5 MME – HSS (S6a) and SGSN – HSS (S6d)

29.2723GPPEvolved Packet System (EPS)Mobility Management Entity (MME) and Serving GPRS Support Node (SGSN) related interfaces based on Diameter protocolRelease 17TS

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

5.1 Introduction

The S6a interface enables the transfer of subscriber related data between the MME and the HSS as described in the 3GPP TS 23.401 [2].

The S6d interface enables the transfer of subscriber related data between the SGSN and the HSS as described in 3GPP TS 23.060 [12].

5.2 Mobility Services

5.2.1 Location Management Procedures

5.2.1.1 Update Location

5.2.1.1.1 General

The Update Location Procedure shall be used between the MME and the HSS and between the SGSN and the HSS to update location information in the HSS. The procedure shall be invoked by the MME or SGSN and is used:

– to inform the HSS about the identity of the MME or SGSN currently serving the user, and optionally in addition;

– to update MME or SGSN with user subscription data; subscription data that are applicable to MMEs but not to SGSNs should not be sent to the SGSN unless the SGSN is known to be a combined MME/SGSN; similarly subscription data that are applicable to SGSNs but not to MMEs should not be sent to the MME unless the MME is known to be a combined MME/SGSN.

– to provide the HSS with other user data, such as Terminal Information or UE SRVCC Capability.

This procedure is mapped to the commands Update-Location-Request/Answer (ULR/ULA) in the Diameter application specified in clause 7.

Table 5.2.1.1.1/1 specifies the involved information elements for the request.

Table 5.2.1.1.1/2 specifies the involved information elements for the answer.

Table 5.2.1.1.1/1: Update Location Request

Information element name	Mapping to Diameter AVP	Cat.	Description
IMSI	User-Name (See IETF RFC 6733 [61])	M	This information element shall contain the user IMSI, formatted according to 3GPP TS 23.003 [3], clause 2.2.
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Terminal Information (See 7.3.3)	Terminal-Information	O	This information element shall contain information about the user’s mobile equipment. Within this Information Element, only the IMEI and the Software-Version AVPs shall be used on the S6a/S6d interface.
ULR Flags (See 7.3.7)	ULR-Flags	M	This Information Element contains a bit mask. See 7.3.7 for the meaning of the bits.
Visited PLMN Id (See 7.3.9)	Visited-PLMN-Id	M	This IE shall contain the MCC and the MNC, see 3GPP TS 23.003 [3]. It may be used to apply roaming based features.
Equivalent PLMN List (See 7.3.151)	Equivalent-PLMN-List	O	This Information Element shall contain the equivalent PLMN list of which the MME/SGSN requests the corresponding CSG Subscription data.
RAT Type (See 7.3.13)	RAT-Type	M	This Information Element contains the radio access type the UE is using. See clause 7.3.13 for details.
SGSN number (See 7.3.102)	SGSN-Number	C	This Information Element contains the ISDN number of the SGSN, see 3GPP TS 23.003 [3]. It shall be present when the message is sent on the S6d interface and the SGSN supports LCS (using MAP based Lg interface) or SMS functionalities or the Gs interface. It may be present when the message is sent on the S6a interface and the requesting node is a combined MME/SGSN.
Homogeneous Support of IMS Voice Over PS Sessions	Homogeneous-Support-of-IMS-Voice-Over-PS-Sessions	O	This Information Element, if present, indicates whether or not "IMS Voice over PS Sessions" is supported homogeneously in all TAs or RAs in the serving node (MME or SGSN or combined MME/SGSN). The value "SUPPORTED" indicates that there is support for "IMS Voice over PS Sessions" in all TAs or RAs. The value "NOT_SUPPORTED" indicates that theres is not support for "IMS Voice over PS Sessions" in any of the TAs or RAs.
V-GMLC address	GMLC-Address	C	This Information Element shall contain, if available, the IPv4 or IPv6 address of the V-GMLC associated with the serving node.
Active APN	Active-APN	O	This Information Element, if present, contains the list of active APNs stored by the MME or SGSN, including the identity of the PDN GW assigned to each APN. For the case of explicitly subscribed APNs, the following information shall be present: – Context-Identifier: context id of subscribed APN in use – Service-Selection: name of subscribed APN in use – MIP6-Agent-Info: including PDN GW identity in use for subscribed APN – Visited-Network-Identifier: identifies the PLMN where the PDN GW was allocated For the case of the Wildcard APN, the following information shall be present: – Context-Identifier: context id of the Wildcard APN – Specific-APN-Info: list of APN-in use and related PDN GW identity when the subscribed APN is the wildcard APN It may be present when MME or SGSN needs to restore PDN GW data in HSS due to a Reset procedure.
UE SRVCC Capability	UE-SRVCC-Capability	C	This information element shall indicate if the UE supports or does not support the SRVCC capability and shall be present if the MME or the SGSN supports SRVCC and this information is available to the MME or the SGSN.
MME Number for MT SMS	MME-Number-for-MT-SMS	C	This Information Element contains the ISDN number of the MME to route SMS to the UE through the MME, see 3GPP TS 23.003 [3]. It shall be present when the MME supports SMS in MME and wishes to provide SMS in MME.
SMS Register Request	SMS-Register-Request	C	This information element is used to inform the HSS if the MME or the SGSN needs to be registered for SMS, prefers not to be registered for SMS or has no preference. It shall be present when the MME supports SMS in MME and requests to be registered for SMS. It shall be present when the SGSN supports "SMS in SGSN" as defined in clause 5.3.18 in 23.060 [12], and requests to be registered for SMS.
SGs MME identity	SGs-MME-Identity	O	This information element is used to inform the HSS of the MME identity that the MME will use over the SGs interface. This information element shall be present, if the MME supports this information element and if the MME identity used over SGs is different from the MME Diameter identity used over S6a.
Coupled node’s Diameter identity	Coupled-Node-Diameter-ID	O	This information element contains the Diameter identity of the coupled node (i.e. MME’s Diameter identity for the SGSN and SGSN’s Diameter identity for the MME) when the message is sent by the combined MME/SGSN. This information element may be present when the message is sent on the S6a/S6d interface and the requesting node is a combined MME/SGSN.
Adjacent PLMNs	Adjacent-PLMNs	O	This information element, if present, shall contain the list of PLMNs where an UE served by the MME/SGSN is likely to make a handover from the PLMN where the MME/SGSN is located. This list is statically configured by the operator in the MME/SGSN, according to the geographical disposition of the different PLMNs in that area, the roaming agreements, etc…
Supported Services (3GPP TS 29.336 [54])	Supported-Services	O	If present, this Information Element shall contain AVPs indicating details of the services supported by the MME/SGSN.

Table 5.2.1.1.1/2: Update Location Answer

Information element name	Mapping to Diameter AVP	Cat.	Description
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Result (See 7.4)	Result-Code / Experimental-Result	M	This IE shall contain the result of the operation. The Result-Code AVP shall be used to indicate success / errors as defined in the Diameter base protocol (see IETF RFC 6733 [61]). The Experimental-Result AVP shall be used for S6a/S6d errors. This is a grouped AVP which shall contain the 3GPP Vendor ID in the Vendor-Id AVP, and the error code in the Experimental-Result-Code AVP. The following errors are applicable: – User Unknown – Unknown EPS Subscription – RAT Not Allowed – Roaming Not Allowed
Error-Diagnostic	Error-Diagnostic	O	If the Experimental Result indicates "Unknown EPS Subscription", Error Diagnostic may be present to indicate whether or not GPRS subscription data are subscribed (i.e. whether or not Network Access Mode stored in the HSS indicates that only circuit service is allowed). If the Experimental Result indicates "Roaming Not Allowed", and the Update Location is rejected due to ODB, Error Diagnostic may be present to indicate the specific type of ODB.
ULA-Flags (See 7.3.8)	ULA-Flags	C	This Information Element contains a bit mask. See 7.3.8 for the meaning of the bits. It shall be present only when the Result-Code AVP is DIAMETER_SUCCESS.
Subscription Data (See 7.3.2)	Subscription-Data	C	This Information Element shall contain the complete subscription profile of the user. It shall be present if success is reported, unless an explicit "skip subscriber data" indication was present in the request.
Reset-IDs (See 7.3.184)	Reset-ID	O	The Reset-ID uniquely identifies a fallible resource in the HSS on which the user (IMSI) depends. In the event of a restart of the fallible resource a Reset message containing the Reset-ID will exactly identify the impacted subscribers.

5.2.1.1.2 Detailed behaviour of the MME and the SGSN

The MME shall make use of this procedure to update the MME identity stored in the HSS (e.g. at initial attach, inter MME tracking area update or radio contact after HSS reset).

The SGSN shall make use of this procedure to update the SGSN identity stored in the HSS (e.g. at initial attach, inter SGSN routing area update or radio contact after HSS reset).

The MME shall make use of this procedure to request SMS data and to become registered for SMS.

The SGSN shall make use of this procedure to request to become registered for SMS.

A combined MME/SGSN which uses different Diameter Identities for the MME and SGSN parts shall not send a second ULR when in a first ULA the ULA-Flag "Separation Indication" was not set.

For UEs receiving emergency services, in which the UE was not successfully authenticated, the MME or SGSN shall not make use of the Update Location procedure.

If the Update Location request is to be sent due to an inter node (SGSN to MME) update and the previous SGSN is a Gn/Gp SGSN, the MME shall set the "Single-Registration-Indication" flag in the ULR-Flags information element in the request.

If the Update Location request is to be sent due to an initial attach, the MME or SGSN shall set the "Initial-Attach-Indicator" flag in the ULR-Flags information element in the request.

If the Update Location request is sent due to a Tracking Area Update following intra-PLMN inter-MME or AMF to MME handover, then the MME may set the Intra-PLMN-inter-MME handover flag in the ULR-Flags information element in the request.

If the Update Location request is sent due to a Tracking Area Update following inter-PLMN inter-MME or AMF to MME handover, then the MME may set the Inter-PLMN-inter-MME handover flag in the ULR-Flags information element in the request.

In order to avoid handovers failing (including the cases of emergency and non-emergency EPS fallback voice handovers), the Intra-PLMN-inter-MME handover flag and Inter-PLMN-inter-MME handover flags are required if the HPLMN deploys Steering of Roaming functionality that interferes with the Diameter signalling procedures e.g. as described in the section 6.1 of GSMA PRD IR.73 [71]. Otherwise, these flags are left to be configured based on operator policy.

NOTE 0: It is useful if the HPLMN discloses how they do Steering of Roaming to the VPLMN. The VPLMN can be configured to comply if they support this feature in the MME.

When receiving and supporting Reset-ID AVPs in the response, the MME or SGSN shall delete all the stored Reset-IDs, if there are any, and then store all the received Reset-IDs.

A combined MME/SGSN shall set the "Skip Subscriber Data" flag in the ULR-Flags if subscriber data are already available due to a previous location update.

A combined MME/SGSN that has advertised its support for the combined MME/SGSN capability, by either including the SGSN Number within ULR sent over S6a or including the Coupled-Node-Diameter-ID within ULR sent over S6a/S6d or by using same Diameter identity over S6a and S6d interfaces, shall be prepared to receive a single subscription data update message (IDR or DSR) from the HSS when the subscription data is modified.

If the MME or SGSN knows about the homogeneity of the support of IMS Voice over PS Sessions in all TAs or RAs associated to that serving node (i.e., it is supported in all the TA/RAs or it is not supported in any of the TA/RAs) and for the serving subscriber taking into account roaming relationship for IMS Voice over PS Sessions, it shall include this indication to the HSS in the "Homogeneous Support of IMS Voice over PS Sessions" IE.

The MME or SGSN may include dynamic APN and PGW ID data in the list of Active-APN AVPs, in order to restore this information in the HSS after a Reset procedure.

The MME/SGSN may include an equivalent PLMN list to request the CSG Subscription data of the equivalent PLMNs.

A standalone MME shall not indicate its support for any SGSN specific features, and it shall not request explicitly the download of GPRS data (via the GPRS-Subscription-Data-Indicator flag; see clause 7.3.7). A standalone MME that does not support the "SMS in MME" feature shall not provide its MME Number for MT SMS, "SMS only" indication or SMS Registration Request and therefore not indicate its support for any SMS related features (such as ODB or barring services).

For an SGSN, if a DIAMETER_ERROR_CAMEL_SUBSCRIPTION_PRESENT is received, the SGSN shall initiate the update location procedure with MAP over Gr interface and use Gr for the subsequent mobility procedures.

For a standalone MME or SGSN, if EPS or GPRS subscription data is received, the standalone MME or SGSN shall replace all of the EPS or GPRS subscription data of the user in the MME or SGSN. Any optional EPS or GPRS data not received, but stored in the standalone MME or SGSN, shall be deleted.

For a combined MME/SGSN, if EPS subscription data of the user is received, it shall replace all of the EPS subscription data of the user. Any optional EPS data not received by the combined MME/SGSN, but stored in the MME/SGSN, shall be deleted.

For a combined MME/SGSN, if GPRS subscription data of the user is received, it shall replace all of the GPRS subscription data of the user. Any optional GPRS data not received by the combined MME/ SGSN, but stored in the MME/SGSN, shall be deleted.

When receiving an Update Location response from the HSS, the MME or SGSN shall check the result code. If it indicates success the MME or SGSN shall store the received subscription profile (if any), and it shall store the HSS identity as received in the Origin-Host AVP.

If an Additional MSISDN (A-MSISDN) is available in the subscription data and downloaded in the A-MSISDN AVP to the MME/SGSN in an Update Location and if the MME or SGSN supports the additional MSISDN feature, the MME or SGSN shall use the Additional MSISDN as C-MSISDN.

For UEs receiving emergency services (i.e. emergency attached UEs or normal attached UEs with a UE Requested PDN Connection for emergency services), and if the MME or SGSN supports emergency services for users in limited service state, the MME or SGSN shall proceed even if the Update Location procedure fails (e.g. authenticated users with roaming restrictions or RAT-Type restrictions in HSS).

When receiving GPRS-Subscription-Data AVP in the response, the SGSN or combined MME/SGSN shall delete all the stored PDP-Contexts, if there are any, and then store all the received PDP-Contexts.

When receiving the APN-Configuration-Profile AVP in a ULA, the MME or SGSN shall delete all the stored APN-Configurations, if there are any, and then store all the received APN-Configurations.

For each of the received APN-Configurations in the APN-Configuration-Profile, if both the MIP6-Agent-Info and the PDN-GW-Allocation-Type AVPs are absent in the APN-Configuration AVP and the MME or SGSN does not have any associated PGW information, the MME or SGSN shall perform the PGW selection (static or dynamic) according to the local configuration. If MIP6-Agent-Info is present, and PDN-GW-Allocation-Type is not present, this means that the PDN GW address included in MIP6-Agent-Info has been statically allocated. If the MIP6-Agent-Info contains an FQDN of the PDN GW, the MME shall retrieve the PGW PLMN ID from the MIP-Home-Agent-Host AVP within the MIP6-Agent-Info AVP.

When receiving an Update Location response from the HSS in the TAU or RAU procedure, for each of the received APN-Configurations in the APN-Configuration-Profile, if both the MIP6-Agent-Info and the PDN-GW-Allocation-Type AVPs are absent in the APN-Configuration AVP and the MME or SGSN has associated PGW information and the UE-level access restriction "HO-To-Non-3GPP-Access Not Allowed" is not set, the MME or SGSN should send a Notify Request if HO to the WLAN is supported in the network, including the APN and PDN GW identity to the HSS in order to restore this information in the HSS e.g. after a Reset procedure.

If the MME/SGSN supports interworking with Gn/Gp-SGSNs, it shall ensure that the Context -Identifier sent over GTPv1 for each of the received APN-Configurations is within the range of 1 and 255.

NOTE 1: If the MME/SGSN receives from HSS a Context-Identifier value higher than 255, how this value is mapped to a value between 1 and 255 is implementation specific.

If the subscriber is not roaming and the SIPTO-Permission information for an APN is present, the MME or SGSN shall allow SIPTO above RAN for that APN only if the SIPTO-Permission information indicates so.

If the subscriber is not roaming and the SIPTO-Permission information for an APN is not present, the MME or SGSN may allow SIPTO above RAN for that APN.

If the subscriber is roaming and the SIPTO-Permission information for an APN is present, the MME or SGSN shall allow SIPTO above RAN for that APN only if the SIPTO-Permission information indicates so and the VPLMN Dynamic Address is allowed and the MME or SGSN selects a PDN GW in the VPLMN.

If the subscriber is roaming and the SIPTO-Permission information for an APN is not present, the MME or SGSN shall not allow SIPTO above RAN for that APN.

NOTE 2: Based on local configuration, the MME or SGSN can determine not to allow SIPTO above RAN for an APN, regardless if the SIPTO-Permission information is present.

If the subscriber is not roaming and the SIPTO-Local-Network-Permission information for an APN is present, the MME or SGSN shall allow SIPTO at the local network for that APN only if the SIPTO-Local-Network-Permission information indicates so.

If the subscriber is not roaming and the SIPTO-Local-Network-Permission information for an APN is not present, the MME or SGSN may allow SIPTO at the local network for that APN.

If the subscriber is roaming and the SIPTO-Local-Network-Permission information for an APN is present, the MME or SGSN shall allow SIPTO at the local network for that APN only if the SIPTO-Local-Network-Permission information indicates so and the VPLMN Dynamic Address is allowed and the MME or SGSN selects a L-GW in the VPLMN.

If the subscriber is roaming and the SIPTO-Local-Network-Permission information for an APN is not present, the MME or SGSN shall not allow SIPTO at the local network for that APN.

NOTE 3: Based on local configuration, the MME or SGSN can determine not to allow SIPTO at the local network for an APN, regardless if the SIPTO-Local-Network-Permission information is present.

If MPS-Priority AVP is present and the UE is subscribed to the eMLPP or 1x RTT priority service in the CS domain as indicated by the MPS-CS-Priority bit of the AVP, the MME shall allow the UE to initiate the RRC connection with higher priority than other normal UEs during CS Fallback procedure. If the MPS-Priority AVP is present and the UE is subscribed to MPS in the EPS domain as indicated by the MPS-EPS-Priority bit of the AVP, the MME shall allow the UE to initiate the RRC connection with higher priority than other normal UEs.

If the subscriber is not roaming, the MME or SGSN may allow or prohibit the UE to use LIPA as indicated by LIPA-Permission for a specific APN.

If the subscriber is roaming and the VPLMN-LIPA-Allowed AVP indicates that the UE is not allowed to use LIPA in the VPLMN where the UE is attached, the MME or SGSN shall not provide LIPA for the UE and shall not consider the LIPA-Permission AVP. If the VPLMN-LIPA-Allowed AVP indicates that the UE is allowed to use LIPA in the VPLMN, the MME or SGSN may allow or prohibit the UE to use LIPA as indicated by LIPA-Permission for a specific APN. The VPLMN-Dynamic-Address-Allowed AVP shall not be considered if it is received when the MME or SGSN establishes a PDN connection with LIPA.

If the LIPA-Permission information for an APN indicates LIPA only, the MME or SGSN shall only allow LIPA for that APN via the authorized CSGs according to the CSG Subscription Data. If the LIPA-Permission information for an APN indicates LIPA prohibited, the MME or SGSN shall not allow LIPA for that APN. If the LIPA-Permission information for an APN indicates LIPA conditional, the MME or SGSN shall allow non LIPA, and LIPA for that APN via the authorized CSGs according to the CSG Subscription Data. If the LIPA-Permission AVP is not present for a specific APN, the APN shall not be allowed to use LIPA.

The LIPA-Permission information for the Wildcard APN shall apply to any APN that is not explicitly present in the subscription data.

The SIPTO-Permission information for the Wildcard APN shall apply to any APN that is not explicitly present in the subscription data.

The SIPTO-Local-Network-Permission information for the Wildcard APN shall apply to any APN that is not explicitly present in the subscription data.

If the subscription data received for a certain APN indicates that the APN was authorized as a consequence of having the Wildcard APN in the user subscription in HSS, then the MME shall not store this APN data beyond the lifetime of the UE session and the MME shall delete them upon disconnection of the UE.

If the MME supports the Relay Node functionality (see 3GPP TS 36.300 [40]) and the subscription data indicates that the subscriber is not a relay, the MME shall reject the attach request from a device attempting to attach to EPS as a Relay Node. If a device requests to be attached to EPS as an UE, the MME shall proceed with the attach procedure regardless of the content of the Relay Node Indicator.

If trace data are received in the subscriber data, the MME or SGSN shall start a Trace Session. For details, see 3GPP TS 32.422 [23].

If the Ext-PDP-Type AVP is present in the PDP-Context AVP, the SGSN or combined MME/SGSN shall ignore the value of the PDP-Type AVP.

If the subscriber is not roaming and the Subscribed-Periodic-RAU-TAU-Timer information is present, the MME or SGSN shall allocate the subscribed value to the UE as periodic RAU or TAU timer. If the subscriber is roaming and the Subscribed-Periodic-RAU-TAU-Timer information is present, the MME or SGSN may use the subscribed periodic RAU/TAU timer value as an indication to decide for allocating a locally configured periodic RAU/TAU timer value to the UE.

For a combined MME/SGSN, the node may include the Coupled-Node-Diameter-ID AVP to allow the HSS to determine if the UE is served by the MME and SGSN parts of the same combined MME/SGSN. When the message is sent over S6a interface and if this AVP is included, the MME shall include the Diameter identity of the coupled SGSN which is used by the SGSN over S6d interface. When the message is sent over S6d interface and if this AVP is included, the SGSN shall include the Diameter identity of the coupled MME which is used by the MME over S6a interface.

NOTE 4: The Coupled-Node-Diameter-ID AVP allows the HSS to determine if the UE is served by the MME and SGSN parts of the same combined MME/SGSN, when the SGSN number is not available and when Diameter identity of S6a and S6d interfaces of the combined MME/SGSN are not the same.

If the MME supports the "SMS in MME" feature and the UE has requested a combined EPS/IMSI attach or Combined TA/LA Update (see 3GPP TS 23.272 [44]) and the MME is not currently registered for SMS, the MME requests to be registered for SMS by indicating its MME Number for MT SMS in the request, including the SMS-Register-Request AVP and the SMS-Only-Indication flag set in the ULR-Flags AVP if UE indicates "SMS only".

If the MME supports the "SMS in MME" feature, when receving an EPS attach or a TAU from a UE accessing NB-IoT which requests SMS by indicating "SMS transfer without Combined Attach" (see 3GPP TS 23.401 [2]), and if the MME is not currently registered for SMS, the MME requests to be registered for SMS by indicating its MME Number for MT SMS in the request, including the SMS-Register-Request AVP.

If the HSS provides the MME with SMS data in the ULA and the ULA-Flags is received with "MME Registered for SMS" flag set, the MME shall store this data for providing SMS in MME service and consider itself registered for SMS.

If the SGSN supports the "SMS in SGSN" feature as specified in 3GPP TS 23.060 [12], clause 5.3.18, and wishes to provide SMS via SGSN it shall set the "SMS in SGSN" flag in the Feature-List AVP, and include SMS-Register-Request AVP. If the SGSN supports the Diameter based Gdd interface for SMS in SGSN, it shall set the "Gdd-in-SGSN" flag in the Feature-List AVP. If the UE has indicated "SMS-Only" this shall be indicated to the HSS setting the SMS-Only–Indication flag in the ULR-Flags AVP.

NOTE 5: the setting of the "SMS in SGSN" feature bit reflects the "SMS in SGSN Offered" as described in stage 2 above.

If the SMS-In-SGSN-Allowed-Indication flag is set in the received Subscription-Data-Flags AVP, the SGSN shall store the subscription data for providing SMS in SGSN service.

If the subscriber is not roaming and the Restoration-Priority information for a certain APN is present, the MME or SGSN shall consider the subscribed value as the relative priority of the user’s PDN connection among PDN connections to the same APN when restoring PDN connections affected by an SGW or PGW failure/restart (see 3GPP TS 23.007 [43]). If the subscriber is roaming and the Restoration-Priority information for a certain APN is present, the MME or SGSN may use the subscribed value as an indication of the relative priority of the user’s PDN connection among PDN connections to the same APN based on service level agreements. The MME/SGSN may use a locally configured value as default restoration priority if the Restoration-Priority AVP for a certain APN is not present, or if it is not permitted by service level agreements for an in-bound roamer.

If the subscription data received for a certain APN includes WLAN-offloadability AVP, then the MME or SGSN shall determine the offloadability of the UE’s PDN Connection(s) to that APN based on subscription data and locally configured policy (e.g. for roaming users or when the subscription data does not include any offloadability indication).

NOTE 6: As indicated in clause 7.3.31, if the UE-level access restriction "HO-To-Non-3GPP-Access Not Allowed" is set, the offload of PDN Connections to WLAN is not allowed for any APN.

If the subscription data received for the user includes the DL-Buffering-Suggested-Packet-Count AVP, then the MME or SGSN should take into account the subscription data, in addition to local policies, to determine whether to invoke extended buffering of downlink packets at the SGW for High Latency Communication. Otherwise, the MME or SGSN shall make this determination based on local policies only.

When receiving IMSI-Group-Id AVP(s) within the Subscription-Data AVP, the MME or SGSN shall replace stored IMSI-Group Ids (if any) with the received information rather than add the received information to the stored information.

When receiving one or more Monitoring-Event-Configuration AVP(s) in the ULA, the MME or SGSN shall start the detection of the Monitoring events indicated in those AVP(s), if not already started, and shall stop the detection and delete the previous monitoring events (if any) which are not indicated in those AVP(s). If there is a failure when starting the detection (e.g. maximum resources exceeded), the MME or SGSN shall not store the failed configuration(s) and shall send a notification of those events whose configuration have failed, as described in clause 5.2.5.1.2 (NOR/NOA commands). If the Subscription-Data AVP is received in the ULA but it does not contain any Monitoring-Event-Configuration AVP(s), the MME or SGSN shall stop the detection and delete all stored monitoring event configurations (if any).

If the MME/SGSN supports Monitoring, the MME/SGSN shall include the Supported-Services AVP with Supported-Monitoring-Events included in the ULR command.

If the MME and the UE support Attach without PDN connection (i.e. EMM-REGISTERED without PDN connection) and the PDN-Connection-Restricted flag is set in the received Subscription-Data-Flags AVP, the MME shall not establish any non-emergency PDN connectionand shall tear down any existing non-emergency PDN connection for this user.

If the subscription data received for the user includes the Preferred-Data-Mode AVP, for an IP APN configuration or for a non-IP APN configuration with SGi based delivery, then the MME should (if the subscriber is not roaming) or may (if the subscriber is roaming) take into account the subscription data, in addition to local policies and the UE’s Preferred Network Behaviour, to determine whether to transmit the traffic associated with this APN over the User Plane and/or over the Control Plane.Otherwise, the MME shall make this determination based on local policies and the UE’s Preferred Network Behaviour only.

If the MME receives from the HSS an Update Location response containing the Emergency-Info AVP in the Subscription-Data, the MME shall use the PDN-GW identity included in Emergency-Info as the PDN-GW used to establish emergency PDN connections with the emergency APN, for non-roaming authenticated UEs requesting the handover of an emergency PDN connection if the MME is configured to use a dynamic PDN-GW for emergency services for such user.

When receiving V2X-Subscription-Data in the ULA, the MME shall determine whether the UE is authorized to use V2X communication over PC5 according to V2X subscription data and UE provided network capability. If the UE is authorized to use V2X communication over PC5, the MME shall store the "V2X service authorized" indication together with the UE AMBR used for PC5 interface (i.e. UE-PC5-AMBR), and provide such information to the eNodeB when needed.

If the MME/SGSN receives from the HSS an Update Location response without the bit set for "NR as Secondary RAT" in the Feature-List AVP, the MME/SGSN, based on local policy, may restrict access for NR as secondary RAT when all relevant entities except HSS supports it.

If the MME receives from the HSS an Update Location response containing in the subscription data the Core-Network-Restrictions AVP with the bit "5GC not allowed" set, the MME shall restrict mobility towards 5GC.

5.2.1.1.3 Detailed behaviour of the HSS

When receiving an Update Location request the HSS shall check whether subscription data exists for the IMSI.

If the HSS determines that there is not any type of subscription for the IMSI (including EPS, GPRS and CS subscription data), a Result Code of DIAMETER_ERROR_USER_UNKNOWN shall be returned.

If the Update Location Request is received over the S6a interface, and the subscriber has not any APN configuration, the HSS shall return a Result Code of DIAMETER_ERROR_UNKNOWN_EPS_SUBSCRIPTION.

If the Update Location Request is received over S6a, from an MME that does not support the "Non-IP PDN Type APNs" feature, and the user’s subscripton profile contains only APN configurations of type "Non-IP", the HSS shall return a Result Code of DIAMETER_ERROR_UNKNOWN_EPS_SUBSCRIPTION.

If the Update Location Request is received over the S6d interface, and the subscriber has neither an APN configuration profile nor GPRS subscription data, the HSS shall return a Result Code of DIAMETER_ERROR_UNKNOWN_EPS_SUBSCRIPTION.

When sending DIAMETER_ERROR_UNKNOWN_EPS_SUBSCRIPTION, an Error Diagnostic information may be added to indicate whether or not GPRS subscription data are subscribed (i.e. whether or not Network Access Mode stored in the HSS indicates that only CS service is allowed).

The HSS shall check whether the RAT type the UE is using is allowed for the subscriber in the serving PLMN. If it is not, a Result Code of DIAMETER_ERROR_RAT_NOT_ALLOWED shall be returned.

The HSS shall check whether access to EPC is allowed, based on the active Core Network Restrictions of the subscriber. If access to EPC is restricted, a Result Code of DIAMETER_ERROR_UNKNOWN_EPS_SUBSCRIPTION shall be returned.

The HSS shall check whether roaming is not allowed in the VPLMN due to ODB. If so a Result Code of DIAMETER_ERROR_ROAMING_NOT_ALLOWED shall be returned. When this error is sent due to the MME or SGSN not supporting a certain ODB category, an Error Diagnostic information element may be added to indicate the type of ODB; if this error is sent due to the ODB indicating "Barring of Roaming", Error Diagnostic shall not be included.

If the Update Location Request is received over the S6d interface and the HSS supports the "SGSN CAMEL Capability" feature, and the SGSN indicates support of SGSN CAMEL capability, the HSS shall check if the subscriber has SGSN CAMEL Subscription data. If the subscriber has SGSN CAMEL Subscription data, the HSS shall return a Result Code of DIAMETER_ERROR_CAMEL_SUBSCRIPTION_PRESENT.

If the Update Location Request is received over the S6a interface, the HSS shall send a Cancel Location Request with a Cancellation-Type of MME_UPDATE_PROCEDURE (CLR; see clause 7.2.7) to the previous MME (if any) and replace the stored MME-Identity with the received value (the MME-Identity is received within the Origin-Host AVP). The HSS shall reset the "UE purged in MME" flag and delete any stored last known MME location information of the (no longer) purged UE. If the "Single-Registration-Indication" flag was set in the received request, the HSS shall send a Cancel Location Request with a Cancellation-Type of SGSN_UPDATE_PROCEDURE to the SGSN (MAP Cancel Location), and delete the stored SGSN address and SGSN number. If the "Initial-Attach-Indicator" flag was set in the received request, and the "Single-Registration-Indication" flag was not set, the HSS shall send a Cancel Location Request with a Cancellation-Type of INITIAL_ATTACH_PROCEDURE (CLR; see clause 7.2.7, or MAP Cancel Location) to the SGSN if there is an SGSN registration.

If the Update Location Request is received over the S6d interface, the HSS shall send a Cancel Location Request with a Cancellation-Type of SGSN_UPDATE_PROCEDURE (CLR; see clause 7.2.7, or MAP Cancel Location) to the previous SGSN (if any) and replace the stored SGSN-Identity with the received value (the SGSN-Identity is received within the Origin-Host AVP). The HSS shall reset the "UE purged in SGSN" flag and delete any stored last known SGSN location information of the (no longer) purged UE. If the "Initial-Attach-Indicator" flag was set in the received request, the HSS shall send a Cancel Location Request with a Cancellation-Type of INITIAL_ATTACH_PROCEDURE (CLR; see clause 7.2.7) to the MME if there is an MME registration.

When the HSS receives the Update Location Request, if a 15^th digit of the IMEI AVP is received, the HSS may discard the digit.

If the Update Location Request includes either the ULR-flag Inter-PLMN-inter-MME or the ULR-flag intra-PLMN-inter-MME, then the HSS may ignore this information.

NOTE 1: These flags are intended for use by Steering of Roaming functions that are not standardised by 3GPP and which operate by interfering with the Diameter procedures.

If the Update Location Request includes the list of active APNs, the HSS shall delete all the stored dynamic PDN GW information, if there are any, and then replace them by the PDN GW information received in the list of Active-APN AVPs.

If the Update Location Request includes an equivalent PLMN list, the HSS shall return the CSG list (if any) for each equivalent PLMN to the MME with the subscription data, and Visited-PLMN-Id AVP shall be present in the CSG-Subscription-Data AVP to indicate the corresponding PLMN. If there is no equivalent PLMN list received, the HSS may not include Visited-PLMN-Id AVP in the CSG-Subscription-Data AVP, and the CSG-Subscription-Data AVP shall contain the CSG subscription data of the registered PLMN of the MME or the SGSN.

If the Update Location Request is received over the S6a interface for a user for which the URRP-MME parameter is set in the HSS, the HSS shall clear the URRP-MME parameter and send an indication to the corresponding Service Related Entities.

If the Update Location Request is received over the S6d interface for a user for which the URRP-SGSN parameter is set in the HSS, the HSS shall clear the URRP-SGSN parameter and send an indication to the corresponding Service Related Entities.

If no result code has been sent to the MME or SGSN so far, the HSS shall include the subscription data in the ULA command according to the ULR-Flags and the supported/unsupported features of the MME or SGSN, unless an explicit "skip subscriber data" indication has been received in the request, and shall return a Result Code of DIAMETER_SUCCESS.

When the APN-Configuration-Profile AVP is present in the Subscription-Data AVP sent within a ULA, the AVP shall contain at least the default APN Configuration and a Context-Identifier AVP that identifies the per subscriber’s default APN configuration. The default APN Configuration shall not contain the Wildcard APN (see 3GPP TS 23.003 [3], clause 9.2); the default APN shall always contain an explicit APN.

The GPRS Subscription data (if available in the HSS) shall only be present in the ULA command if it was indicated by the serving node in the ULR-Flags AVP (see clause 7.3.7), or when the subscription data is returned by a Pre-Rel-8 HSS (via an IWF) or when the Update Location Request is received over the S6d interface and there is no APN configuration profile stored for the subscriber.

The HSS shall use the indication received in the GPRS-Subscription-Data-Indicator for future use in the subscriber data update procedures.

The HSS shall store the new terminal information and/or the new UE SRVCC capability, if they are present in the request. If the UE SRVCC capability is not present, the HSS shall store that it has no knowledge of the UE SRVCC capability.

If the MME/SGSN indicates support of the Additional-MSISDN feature and an additional MSISDN (A-MSISDN) is available in the subscription data, the HSS shall send the provisioned additional MSISDN together with the MSISDN.

If the MME/SGSN does not support the Additional-MSISDN feature, the HSS shall populate the MSISDN AVP either with the subscribed MSISDN or the subscribed additional MSISDN based on operator policy and availability.

NOTE 2: When the MME/SGSN does not support the Additional-MSISDN feature, the MME/SGSN will use the MSISDN from the MSISDN AVP as C-MSISDN.

LCS-Info, Teleservice-List and Call-Barring-Info data shall be included according to the list of supported features indicated by the serving node (see clause 7.3.10).

If the HSS supports the "SMS in MME" feature and receives the indication that the MME supports the "SMS in MME" feature and requests to be registered for SMS by including the MME Number for MT SMS, SMS-Register-Request AVP and/or setting the SMS-Only-Indication flag in the ULR-Flags AVP if indicated from the UE, the HSS shall determine if SMS can be provided via the MME as described in 3GPP TS 23.272 [44]. If SMS in MME is accepted the HSS shall register the MME for SMS, store the "MME number for MT SMS" as the corresponding MSC number to be used for MT SMS and return an indication of MME registered for SMS in ULA-Flags AVP.

If the MME is successfully registered for SMS the HSS shall download the available SMS related subscription data that may comprise SMS teleservice, MSISDN, ODB and barring services for SMS according to supported features. Also, if the user is considered as not reachable (i.e., MNRF flag is set in HSS for that user), and the UE is considered to have free available memory (i.e., MCEF flag is not set in HSS for that user), the HSS shall send a MAP-Alert-Service-Centre message or S6c-Alert-Service-Centre-Request to the SMS-IWMSC (see 3GPP TS 29.338 [48]).

If the HSS supports the "SMS in SGSN" feature as described in 3GPP TS 23.060 [12], clause 5.3.18 and receives the indication from the SGSN that it supports "SMS in SGSN" feature, and SMS-Register-Request AVP and/or the SMS-Only-Indication flag in the ULR-Flags AVP if indicated from the UE, and the PS subscriber data allow for SMS services (e.g. the subscription information indicates "PS and SMS-Only"), the HSS shall determine if SMS can be provided via the SGSN as described in 3GPP TS 23.060 [12]. If "SMS in SGSN" is accepted the HSS shall indicate in the ULA that "SMS in SGSN" is allowed to the SGSN and shall handle MT SMS as described in 3GPP TS 23.060 [12], clause 5.3.18. If the HSS supports the "Gdd-in-SGSN" feature and receives the indication from the SGSN that it supports the "Gdd-in-SGSN" feature, the HSS shall store the information that the SGSN supports the Gdd interface. Also, if the user is considered as not reachable (i.e., MNRG flag is set in HSS for that user), and the UE is considered to have free available memory (i.e., MCEF flag is not set in HSS for that user), the HSS shall send a MAP-Alert-Service-Centre message or S6c-Alert-Service-Centre-Request to the SMS-IWMSC (see 3GPP TS 29.338 [48]).

The HSS may use the indication received in the Node-Type-Indicator for future use in the subscriber data update procedures.

Subscriber-Status AVP shall be present in the Subscription-Data AVP when sent within a ULA. If the value "OPERATOR_DETERMINED_BARRING" is sent, the Operator-Determined-Barring AVP or HPLMN-ODB AVP shall also be present in the Subscription-Data AVP, or vice versa.

Access-Restriction-Data AVP shall be present within the Subscription-Data AVP sent within a ULA if at least one of the defined restrictions applies.

The AMBR AVP shall be present in the Subscription-Data AVP when the APN-Configuration-Profile AVP is sent within a ULA (as part of the Subscription-Data AVP) and may be present in the Subscription-Data AVP when the GPRS-Subscription-Data AVP is present.

The EPS-Subscribed-QoS-Profile AVP and the AMBR AVP shall be present in the APN-Configuration AVP when the APN-Configuration AVP is sent in the APN-Configuration-Profile AVP and when the APN-Configuration-Profile AVP is sent within a ULA (as part of the Subscription-Data AVP).

For those APNs that have been authorized as a consequence of having the Wildcard APN in the user subscription, the HSS shall include the specific APN name and associated PDN-GW identity inside the APN context of the Wildcard APN. This indicates to the MME that the particular APN shall not be cached in the MME and it shall be deleted when the UE session is terminated.

If a Result Code of DIAMETER_SUCCESS is returned, the HSS shall set the Separation Indication in the response.

If the HSS receives an indication in the ULR command about the homogeneous support of IMS Voice over PS Sessions in all TA/RAs associated to a serving node, it may use this information in the future in order to skip the T-ADS data retrieval, as described in clause 5.2.2.1 (IDR/IDA commands).

Subscribed-VSRVCC AVP shall be present within the Subscription-Data AVP sent within a ULA only if the user is subscribed to the SRVCC and vSRVCC.

If the UE is allowed to use Proximity-based Services in the visited PLMN, the HSS shall include ProSe-Subscription-Data AVP within the Subscription-Data AVP sent within a ULA.

If the HSS receives the SGs MME identity and if the HSS supports this information element, the HSS shall store it for use with VLR restoration.

If the HSS receives Update Location Request over both the S6a and S6d interfaces then based on the following conditions the HSS concludes if the UE is served by the MME and SGSN parts of the same combined MME/SGSN:

– if both the messages contain the same SGSN number; or

– if the Diameter identity received over S6a matches with the Diameter identity received over S6d; or

– if the Coupled-Node-Diameter-ID AVP received over S6a interface matches with the Diameter identity received within Origin-Host AVP over S6d interface OR if the Coupled-Node-Diameter-ID AVP received over S6d interface matches with the Diameter identity received within Origin-Host AVP over S6a interface.

If the HSS supports the handling of access restrictions for adjacent PLMNs, and it receives a list of adjacent PLMNs from the MME/SGSN, the HSS may send the associated Access Restriction Data, according to local operator policies, in the Adjacent-Access-Restriction-Data AVP, so the MME/SGSN can use this information to allow, or prevent, inter-RAT inter-PLMN handovers towards any of the PLMNs indicated by the HSS. The HSS shall not include in the list of Adjacent-Access-Restriction-Data the PLMN-ID, and its access restrictions, of the current PLMN where the MME/SGSN is located, since this information is already conveyed in the Access-Restriction-Data AVP inside the Subscription-Data AVP.

If the HSS supports Monitoring events and receives a Supported-Services AVP it shall only trigger those services which are supported by the MME/SGSN.

If the HSS has previously received over SWx (see 3GPP TS 29.273 [59]) the identity of the PDN-GW to be used for the establishment of emergency PDN connections, it shall include it as part of the Subscription-Data AVP (in the Emergeny-Info AVP), in the Update Location response to the MME.

If the UE is allowed to use V2X service in the visited PLMN and the MME supports V2X service, the HSS shall include V2X-Subscription-Data AVP into Subscription-Data AVP within the ULA command.

If the MME/SGSN supports the "External-Identifier" feature, the HSS shall include the External-Identifier associated with Monitoring Event Configuration in the External-Identifier AVP if populated in the subscription. When multiple External Identifiers are defined for a same subscription, the HSS shall send a default External Identifier in the External-Identifier AVP of the Subscription-Data AVP, and shall include a specific External Identifier (if different from the default External Identifier) associated to each Monitoring Event Configuration in the External-Identifier AVP of each Monitoring-Event-Configuration AVP occurrence inside the Subscription-Data AVP.

The Aerial-UE-Subscription-Information AVP shall be present within the Subscription-Data AVP sent within a ULA only if the user has Aerial UE subscription information.

5.2.1.2 Cancel Location

5.2.1.2.1 General

The Cancel Location Procedure shall be used between the HSS and the MME and between the HSS and the SGSN to delete a subscriber record from the MME or SGSN. The procedure shall be invoked by the HSS and is used:

– to inform the MME or SGSN about a subscription withdrawal, or a change in the subscriber profile that does not allow PS services anymore (e.g., the Network Access Mode does not allow PS services), or a change in the subscriber profile that does not allow access to EPC anymore, or

– to inform the MME or SGSN about an ongoing update procedure i.e. MME or SGSN change or

– to inform the MME or SGSN about an initial attach procedure.

This procedure is mapped to the commands Cancel-Location-Request/Answer (CLR/CLA) in the Diameter application specified in clause 7.

Table 5.2.1.2.1/1 specifies the involved information elements for the request.

Table 5.2.1.2.1/2 specifies the involved information elements for the answer.

Table 5.2.1.2.1/1: Cancel Location Request

Information element name	Mapping to Diameter AVP	Cat.	Description
IMSI	User-Name (See IETF RFC 6733 [61])	M	This information element shall contain the user IMSI, formatted according to 3GPP TS 23.003 [3], clause 2.2.
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Cancellation Type (See 7.3.24)	Cancellation-Type	M	Defined values that can be used are: – MME-Update Procedure, – SGSN-Update Procedure, – Subscription Withdrawal, – Update Procedure_IWF, – Initial Attach Procedure.
CLR Flags (See 7.3.152)	CLR-Flags	O	This Information Element contains a bit mask. See 7.3.152 for the meaning of the bits and the condition for each bit to be set or not.

Table 5.2.1.2.1/2: Cancel Location Answer

Information element name

Mapping to Diameter AVP

Cat.

Description

Supported Features

(See 3GPP TS 29.229 [9])

Supported-Features

If present, this information element shall contain the list of features supported by the origin host.

Result

(See 7.4)

Result-Code / Experimental-Result

The result of the operation.

The Result-Code AVP shall be used to indicate success / errors as defined in the Diameter base protocol (see IETF RFC 6733 [61]).

5.2.1.2.2 Detailed behaviour of the MME and the SGSN

When receiving a Cancel Location request the MME or SGSN shall check whether the IMSI is known.

If it is not known, a result code of DIAMETER_SUCCESS is returned.

If it is known, the MME or SGSN shall check the Cancellation Type and act accordingly.

If the Cancellation Type is "Subscription Withdrawal", the MME or SGSN shall delete the subscription data and detach the UE; in addition, if the Reattach-Required flag is set, the MME or SGSN shall indicate to the UE to initiate an immediate re-attach procedure, as described in 3GPP TS 23.401 [2] and 3GPP TS 23.060 [12]. A result code of DIAMETER_SUCCESS shall be returned.

If a cancellation type of "Initial Attach Procedure" is received, the MME or SGSN shall not delete the subscription data. For details see 3GPP TS 23.401 [2] and 3GPP TS 23.060 [12]. If the MME receives this cancelation type, and it is registered for SMS, it shall consider itself as unregistered for SMS. Also in this case a result code of DIAMETER_SUCCESS shall be returned.

When a UE is served by a single combined MME/SGSN for both E-UTRAN and non-E-UTRAN access, the combined MME/SGSN shall check the Cancellation-Type. If it indicates Subscription Withdrawal or Update Procedure_IWF, the CLR is processed both in the MME part and in the SGSN part of the combined node. If it indicates Initial Attach Procedure, and if the CLR-Flags AVP is received and supported by the combined MME/SGSN, the CLR is processed only in the affected part of the combined node as indicated by the "S6a/S6d-Indicator" flag in the CLR-Flags AVP. Otherwise, the CLR is processed only in the affected part of the combined node and subscription data are kept for the not affected part.

5.2.1.2.3 Detailed behaviour of the HSS

The HSS shall make use of this procedure when the subscription is withdrawn by the HSS operator, and when the HSS detects that the UE has moved to a new MME or SGSN area, and when EPC access is not allowed due to Core Network Restrictions.

The HSS+UDM shall also make use of this procedure when the HSS+UDM detects that the UE has moved to a new AMF area, if the AMF indicates to the HSS+UDM to cancel MME and/or SGSN. The HSS+UDM shall include a cancellation type as specified in clause 5.4.2.2 of 3GPP TS 29.563 [70].

The HSS shall include a cancellation type of "Subscription Withdrawal" if the subscription is withdrawn by the operator, or if the subscriber profile does not allow PS services anymore, or if the Core Network Restrictions do not allow access to EPC anymore; the HSS may set the Reattach-Required flag in order to request the MME or the SGSN to trigger an immediate reattachment of the UE.

The HSS shall include a cancellation type of "MME Update Procedure" if the UE moved to a new MME area.

The HSS shall include a cancellation type of "SGSN Update Procedure" if the UE moved to a new SGSN area.

The HSS shall include a cancellation type of "Initial Attach Procedure" if the cancel location is initiated due to an Initial Attach from the UE.

The HSS shall include the CLR-Flags with the "S6a/S6d-Indicator" flag indicating the affected part of the combined node if the cancel location is to be sent to a combined MME/SGSN during initial attach procedure.

5.2.1.3 Purge UE

5.2.1.3.1 General

The Purge UE Procedure shall be used between the MME and the HSS and between the SGSN and the HSS to indicate that the subscriber’s profile has been deleted from the MME or SGSN either by an MMI interaction or automatically, e.g. because the UE has been inactive for several days.

This procedure is mapped to the commands Purge-UE-Request/Answer (PUR/PUA) in the Diameter application specified in clause 7.

Table 5.2.1.3.1/1 specifies the involved information elements for the request.

Table 5.2.1.3.1/2 specifies the involved information elements for the answer.

Table 5.2.1.3.1/1: Purge UE Request

Information element name	Mapping to Diameter AVP	Cat.	Description
IMSI	User-Name (See IETF RFC 6733 [61])	M	This information element shall contain user IMSI, formatted according to 3GPP TS 23.003 [3], clause 2.2.
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
PUR-Flags (See 7.3.149)	PUR-Flags	O	If present, this Information Element shall contain a bitmask. See clause 7.3.149 for the meaning of the bits.
EPS-Location-Information (See 7.3.111)	EPS-Location-Information	C	This Information Element shall contain the last known EPS-Location Information of the purged UE. Shall be present if available.

Table 5.2.1.3.1/2: Purge UE Answer

Information element name	Mapping to Diameter AVP	Cat.	Description
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Result (See 7.4)	Result-Code / Experimental-Result	M	This IE shall contain the result of the operation. The Result-Code AVP shall be used to indication success / errors as defined in the Diameter base protocol (see IETF RFC 6733 [61]). The Experimental-Result AVP shall be used for S6a/S6d errors. This is a grouped AVP which shall contain the 3GPP Vendor ID in the Vendor-Id AVP, and the error code in the Experimental-Result-Code AVP. The following errors are applicable: – User Unknown
PUA-Flags (See 7.3.48)	PUA-Flags	C	This Information Element shall contain a bit mask. See clause 7.3.48 for the meaning of the bits. It shall be present only when the Result-Code AVP is DIAMETER_SUCCESS.

5.2.1.3.2 Detailed behaviour of the MME and the SGSN

The MME shall make use of this procedure to set the "UE Purged in the MME" flag in the HSS when the subscription profile is deleted from the MME database due to MMI interaction or after long UE inactivity.

The SGSN shall make use of this procedure to set the "UE Purged in SGSN" flag in the HSS when the subscription profile is deleted from the SGSN database due to MMI interaction or after long UE inactivity.

The combined MME/SGSN when using a single Origin-Host identity shall make use of this procedure to set the "UE Purged in MME" and "UE Purged in SGSN" flags in the HSS when the subscription profile is deleted from the common MME/SGSN database due to MMI interaction or after long UE inactivity on all registered accesses. If the HSS has indicated support for the Partial Purge feature (see clause 7.3.10), the combined MME/SGSN may also indicate to the HSS a Purge of the UE in only one of the serving nodes in the combined node (either in the MME or in the SGSN).

The combined MME/SGSN when using different Origin-Host identities for MME and SGSN shall send two Purge UE Requests as if it was not combined.

When receiving a Purge UE response from the HSS the MME shall check the Result Code. If it indicates success, the MME shall check the PUA flag "freeze M-TMSI", and if set freeze the M-TMSI i.e. block it for immediate re-use.

When receiving a Purge UE response from the HSS the SGSN shall check the Result Code. If it indicates success, the SGSN shall check the PUA flag "freeze P-TMSI", and if set freeze the P-TMSI i.e. block it for immediate re-use.

When receiving a Purge UE response from the HSS the combined MME/SGSN shall check the Result Code. If it indicates success, the combined MME/SGSN shall check the PUA flag "freeze M-TMSI" and "freeze P-TMSI", and if set freeze the M-TMSI and/or the P-TMSI i.e. block it for immediate re-use.

5.2.1.3.3 Detailed behaviour of HSS

When receiving a Purge UE request the HSS shall check whether the IMSI is known.

If it is not known, a result code of DIAMETER_ERROR_USER_UNKNOWN shall be returned.

If it is known, the HSS shall set the result code to DIAMETER_SUCCESS and compare the received identity in the Origin-Host with the stored MME-Identity and with the stored SGSN-Identity.

If the received identity matches the stored MME-identity and the stored SGSN-Identity (no matter whether the node type indicator bit in ULR-Flags was set or clear), then:

– if the HSS supports the Partial Purge feature (see clause 7.3.10), and the combined MME/SGSN indicated that the UE was purged in only one of the serving nodes, the HSS shall set the PUA flags according to the serving node where the purge was done (i.e., either "freeze M-TMSI" if the purge was done in the MME, or "freeze P-TMSI" if the purge was done in the SGSN); similarly, the HSS shall either set the "UE purged in MME" flag and store the received last known MME Location information of the purged UE, or set the "UE purged in SGSN" flag and store the received last known SGSN-Location Information of the purged UE, accordingly;

– if the HSS does not support the Partial Purge feature, or the combined MME/SGSN did not indicate that the UE was purged in only one of the serving nodes, the HSS shall set the PUA flags "freeze M-TMSI" and "freeze P-TMSI" in the answer message and set the flag "UE purged in MME" and "UE purged in SGSN" and store the received last known EPS Location Information of the purged UE;

If the received identity matches the stored MME-identity but not the stored SGSN-identity, the HSS shall set the PUA flag "freeze M-TMSI" and clear the PUA flag "freeze P-TMSI" in the answer message, set the flag "UE purged in MME" and store the received last known MME location information of the purged UE;

If the received identity matches the stored SGSN-identity but not the stored MME-identity, the HSS shall set the PUA flag "freeze P-TMSI" and clear the PUA flag "freeze M-TMSI" in the answer message and set the flag "UE purged in SGSN" and store the received last known SGSN location information of the purged UE;

If the received identity does not match the stored MME-identity and does not match the stored SGSN-identity, the HSS shall clear the PUA flags "freeze M-TMSI" and "freeze P-TMSI in the answer message.

5.2.2 Subscriber Data Handling Procedures

5.2.2.1 Insert Subscriber Data

5.2.2.1.1 General

The Insert Subscriber Data Procedure shall be used between the HSS and the MME and between the HSS and the SGSN for updating and/or requesting certain user data in the MME or SGSN in the following situations:

– due to administrative changes of the user data in the HSS and the user is now located in an MME or SGSN, i.e. if the user was given a subscription and the subscription has changed; subscription data that are applicable to MMEs but not to SGSNs should not be sent to the SGSN unless the SGSN is known to be a combined MME/SGSN; similarly subscription data that are applicable to SGSNs but not to MMEs should not be sent to the MME unless the MME is known to be a combined MME/SGSN.

– the operator has applied, changed or removed Operator Determined Barring for this user;

– activate subscriber tracing in the MME or the SGSN;

– to indicate to the MME or SGSN that the HSS has requested to be notified when the UE has become reachable;

– to request from the MME or SGSN the necessary data to support the T-ADS functionality;

– to retrieve location information and/or state information from the MME or the SGSN;

– to retrieve from the MME or the SGSN the Local Time Zone of the location in the visited network where the UE is attached;

– to update the STN-SR (e.g., as a result of an Sh interaction with an SCC-AS).

– to update the MME/SGSN with the identity of a dynamically allocated PDN GW as a result of the first PDN connection establishment associated with an APN over non 3GPP access or 5GS..

– to update the MME with the identity of a PDN GW for Emergency Services as a result of the PDN connection establishment for Emergency Services over non 3GPP access.

– to indicate to the MME that the HSS has deregistered the MME for SMS.

– to indicate to the MME/SGSN that the HSS-based P-CSCF restoration procedure, as described in 3GPP TS 23.380 [51] clause 5.4, shall be executed.

– to request the MME or the SGSN to configure and report the detection of Monitoring events, or delete stored Monitoring events configuration.

– to update the MME with the O&M configured desired Active Time for power saving mode (PSM), or with the value received from the SCEF if Active Time is provided as part of the Suggested-Network-Configuration AVP.

– to update the MME with the O&M configured desired Core Network Restrictions to restrict/allow mobility to 5GC.

If the HSS knows that the UE has attached to the MME and SGSN parts of the same combined MME/SGSN via both the E-UTRAN and UTRAN/GERAN (refer to clause 5.2.1.1.2, 5.2.1.1.3 for further details), the HSS should invoke this procedure for a single time to update and/or request certain user data in the combined MME/SGSN, i.e. the HSS should not invoke this procedure for each of the MME and the SGSN registered respectively.

If the Node-Type-Indicator information has been previously received as cleared in the ULR-Flags and if the MME has not been registered for SMS during update location procedure for the MME, the HSS may skip any change of the SMS related subscription data and consequently does not have to make use of the Insert Subscriber Data procedure to update the SMS subscription data in the MME.

This procedure is mapped to the commands Insert Subscriber Data-Request/Answer (IDR/IDA) in the Diameter application specified in clause 7.

Table 5.2.2.1.1/1 specifies the involved information elements for the request.

Table 5.2.2.1.1/2 specifies the involved information elements for the answer.

Table 5.2.2.1.1/1: Insert Subscriber Data Request

Information element name	Mapping to Diameter AVP	Cat.	Description
IMSI	User-Name (See IETF RFC 6733 [61])	M	This information element shall contain the user IMSI, formatted according to 3GPP TS 23.003 [3], clause 2.2.
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Subscription Data (See 7.3.2)	Subscription-Data	M	This Information Element shall contain the part of the subscription profile that either is to be added to the subscription profile stored in the MME or SGSN or is replacing a part of the subscription profile stored in the MME or SGSN.
IDR Flags (See 7.3.103)	IDR-Flags	C	This Information Element shall contain a bit mask. See 7.3.103 for the meaning of the bits.
Reset-IDs (See 7.3.184)	Reset-ID	O	The Reset-ID uniquely identifies a fallible resource in the HSS on which the user (IMSI) depends. In the event of a restart of the fallible resource a Reset message containing the Reset-ID will exactly identify the impacted subscribers.

Table 5.2.2.1.1/2: Insert Subscriber Data Answer

Information element name	Mapping to Diameter AVP	Cat.	Description
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host. A combined MME/SGSN that makes use of separate origin host values in Update Location Request messages sent on S6a and Update Location Request messages sent on S6d can detect whether the IDR from HSS was sent to the MME or to the SGSN. IDA sent from such combined MME/SGSN corresponds to the MME’s or the SGSN’s supported features respectively. A combined MME/SGSN that makes use of a common origin host value in Update Location Request messages sent on S6a and Update Location Request messages sent on S6d cannot detect whether the IDR from HSS was sent to the MME or to the SGSN. IDA sent from such combined MME/SGSN uses the union of the MME’s and the SGSN’s supported features.
Result (See 7.4)	Result-Code / Experimental-Result	M	This IE shall contain the result of the operation. Result-Code AVP shall be used to indicate success / errors defined in the Diameter base protocol (see IETF RFC 6733 [61]). The Experimental-Result AVP shall be used for S6a/S6d errors. This is a grouped AVP which shall contain the 3GPP Vendor ID in the Vendor-Id AVP, and the error code in the Experimental-Result-Code AVP. The following errors are applicable in this case: – User Unknown
IMS Voice over PS Sessions Supported (See 7.3.106)	IMS-Voice-Over-PS-Sessions-Supported	C	If available to the serving node, this information element shall indicate whether or not "IMS Voice over PS Sessions" is supported by the UE’s most recently used TA or RA in the serving node (MME or SGSN or combined MME/SGSN). If the UE is in detached state, this information element shall not be included in the response.
Last UE Activity Time (See 7.3.108)	Last-UE-Activity-Time	C	If available to the serving node, this information element shall contain the time of the last radio contact with the UE. If the UE is in detached state, this information element shall not be included in the response.
RAT Type (See 7.3.13)	RAT-Type	C	If available to the serving node, this information element shall indicate the RAT Type of the access where the UE was present at the time of the last radio contact. If the UE is in detached state, this information element shall not be included in the response.
IDA-Flags (See 7.3.47)	IDA-Flags	C	This Information Element shall contain a bit mask. See 7.3.47 for the meaning of the bits.
EPS-User-State (See 7.3.110)	EPS-User-State	C	This Information Element shall contain the EPS-User State. It shall be present if EPS user state was requested within IDR.
EPS-Location-Information (See 7.3.111)	EPS-Location-Information	C	This Information Element shall contain the EPS-Location Information. It shall be present if EPS location information was requested within IDR.
Local Time Zone (See 7.3.156)	Local-Time-Zone	C	This Information Element shall contain information on the Local Time Zone of the location in the visited network where the UE is attached. It shall be present if the Local Time Zone was requested within IDR.
Monitoring Event Report	Monitoring-Event-Report	C	This Information Element shall contain the report of Monitoring event. It shall be present if Monitoring event configuration is included within IDR and any of the requested Monitoring events are available to be reported. (see NOTE 1)
Monitoring Event Config Status	Monitoring-Event-Config-Status	C	This Information Element shall be present if Monitoring event configuration is included in IDR. It shall contain all the configuration status for each Monitoring event that was requested.
Supported Services (3GPP TS 29.336 [54])	Supported-Services	O	If present, this Information Element shall contain AVPs indicating details of the services supported by the MME/SGSN.
NOTE 1: In IWK-SCEF scenarios, an event is available to be reported by the visited MME only if the event is considered as authorized by the visited MME after checking with the IWK-SCEF. Otherwise, the immediate report shall be not be sent in this command (S6a/IDA), and it shall be sent over T6a using RIR command (see 3GPP TS 29.128 [63].

5.2.2.1.2 Detailed behaviour of the MME and the SGSN

When receiving an Insert Subscriber Data request the MME or SGSN shall check whether the IMSI is known.

If it is not known, a result code of DIAMETER_ERROR_USER_UNKNOWN shall be returned.

If it is known, the MME or SGSN shall replace the specific part of the stored subscription data with the received data, or shall add the received data to the stored data.

When receiving the APN-Configuration-Profile AVP within the Subscription-Data AVP, the MME or SGSN shall check the All-APN-Configurations-Included-Indicator value. If it indicates "All_APN_CONFIGURATIONS_INCLUDED", the MME or SGSN shall delete all stored APN-Configurations and then store all received APN-Configurations. Otherwise, the MME or SGSN shall check the Context-Identifier value of each received APN-Configuration. If the Context-Identifier of a received APN-Configuration matches a Context-Identifier of a stored APN-Configuration, the MME or SGSN shall replace the stored APN-Configuration with the received APN-Configuration. If the Context-Identifier of a received APN-Configuration does not match a Context-Identifier of a stored APN-Configuration, the MME or SGSN shall add the received APN-Configuration to the stored APN-Configurations. If the addition or update of the subscription data succeeds in the MME or SGSN, the Result-Code shall be set to DIAMETER_SUCCESS. The MME or SGSN shall then acknowledge the Insert Subscriber Data message by returning an Insert Subscriber Data Answer.

For each of the received APN-Configurations in the APN-Configuration-Profile, if both the MIP6-Agent-Info and the PDN-GW-Allocation-Type AVPs are absent in the APN-Configuration AVP, the MME or SGSN shall perform the PGW selection (static or dynamic) according to the local configuration. If MIP6-Agent-Info is present, and PDN-GW-Allocation-Type is not present, this means that the PDN GW address included in MIP6-Agent-Info has been statically allocated.

If the MME/SGSN supports interworking with Gn/Gp-SGSNs, it shall ensure that the context identifier sent over GTPv1 for each of the received APN-Configurations is within the range of 1 and 255.

NOTE 1: If the MME/SGSN receives from HSS a Contex-Identifier value higher than 255, how this value is mapped to a value between 1 and 255 is implementation specific.

If the MME is requested to notify the HSS when the UE becomes reachable, the MME shall set the URRP-MME parameter to indicate the need to inform the HSS about UE reachability, e.g. when the next NAS activity from the UE is detected. If the SGSN is requested to notify the HSS when the UE becomes reachable, the SGSN shall set the URRP-SGSN parameter to indicate the need to inform the HSS about UE reachability, e.g. when the next NAS activity from the UE is detected.

When receiving GPRS-Subscription-Data AVP within the Subscription-Data AVP, the SGSN or combined MME/SGSN shall check the Complete-Data-List-Included-Indicator value. If it indicates "All_PDP_CONTEXTS_INCLUDED", the SGSN or combined MME/SGSN shall delete all stored PDP-Contexts and then store all received PDP-Contexts. Otherwise, the SGSN or combined MME/SGSN shall check the Context-Identifier value of each received PDP-Context. If the Context-Identifier of a received PDP-Context matches a Context-Identifier of a stored PDP-Context, the SGSN or combined MME/SGSN shall replace the stored PDP-Context with the received PDP-Context. If the Context-Identifier of a received PDP-Context does not match a Context-Identifier of a stored PDP-Context, the SGSN or combined MME/SGSN shall add the received PDP-Context to the stored PDP-Contexts.

If the MME or SGSN receives an empty Subscription-Data AVP, it shall take no action with regard to the stored subscription data.

When receiving HPLMN-ODB AVP within the Subscription-Data AVP, the MME or SGSN shall replace stored HPLMN-ODB data (if any) with the received information rather than add the received information to the stored information. Unsupported Barring categories need not be stored.

When receiving Operator-Determined-Barring AVP within the Subscription-Data AVP, the MME or SGSN shall replace stored ODB subscription information (if any) with the received information rather than add the received information to the stored information. Unsupported Barring categories need not be stored.

When receiving Access-Restriction-Data or Adjacent-Access-Restriction-Data AVPs within the Subscription-Data AVP, the MME or SGSN shall replace the corresponding stored information (if any) with the new received information, rather than adding received information to stored information. The handling of access restrictions per-PLMN is defined in 3GPP TS 23.221 [53], clause 6.3.5a and in 3GPP TS 23.401 [2] clause 4.3.28.

When receiving APN-OI-Replacement AVP within the Subscription-Data AVP, the MME or SGSN shall replace the stored information (if any) with the received information.

When receiving Regional-Subscription-Zone-Code AVP within the Subscription-Data AVP, the MME or SGSN shall replace stored Zone Codes (if any) with the received information rather than add the received information to the stored information. MMEs and SGSNs that do not support regional subscription need not store zone codes. If due to regional subscription restrictions or access restrictions the entire SGSN area is restricted, SGSN shall report it to the HSS by returning the "SGSN Area Restricted" indication within the IDA flags.

When receiving CSG-Subscription-Data AVPs within the Subscription-Data AVP the MME or SGSN shall replace all stored information from previously received CSG-Subscription-Data AVPs (if any) with the received information rather than add the received information to the stored information.

When receiving Teleservice-List AVP, Call-Barring-Info, or LCS-Info AVP, the MME or SGSN shall replace stored information (if any) with the received information rather than add the received information to the stored information.

When receiving ProSe-Subscription-Data AVP, the MME or combined MME/SGSN shall replace stored information (if any) with the received information rather than add the received information to the stored information.

When receiving and supporting Reset-ID AVPs within the request, the MME or SGSN shall replace stored information (if any) with received information rather than add received information to stored information.

When receiving the IDR-Flags with the "T-ADS Data Request" bit set, and the UE is in attached state, the MME or SGSN or combined MME/SGSN shall return in the IDA message the time stamp of the UE’s most recent radio contact and the associated RAT Type, and an indication of whether or not IMS Voice over PS is supported in the current (and most recently used) TA or RA. If the UE is in detached state, the MME or SGSN or combined MME/SGSN shall answer successfully to the T-ADS request from HSS, but it shall not include any of the T-ADS IEs in the response (IMS Voice over PS Sessions Supported, RAT Type and Last UE Activity Time).

When receiving the IDR-Flags with the "EPS User State Request" bit and/or "EPS Location Information Request" bits set the MME or SGSN shall return the corresponding user information to the HSS. If the serving node is a combined MME/SGSN, and the UE is attached via both E-UTRAN and UTRAN/GERAN on the same node, the combined MME/SGSN shall provide the corresponding user information relevant for both MME and SGSN. If the Current Location Request bit was also set and the UE is in idle mode and is expected to be reachable even when it uses a power saving feature (e.g. extended idle mode DRX or PSM as defined in 3GPP TS 23.685 [55]), then the MME or SGSN or combined MME/SGSN shall page the UE in order to return the most up-to-date corresponding user information. If the Current Location Request bit was also set and either paging is unsuccessful or the UE is not expected to be reachable, then the last known location of the UE shall be returned to the HSS. If the Current Location Request bit was also set and the UE (attached via E-UTRAN) is in connected mode, then the MME or combined MME/SGSN shall use S1AP Location Reporting Control procedure towards the eNB prior to reporting the E-UTRAN Cell Global Identification in order to return the UE’s most up-to-date cell information. When the location is returned to the HSS, the MME or the combined MME/SGSN shall provide the age of location information if stored in the MME or the combined MME/SGSN or received from eNB.

When receiving the IDR-Flags with only the "Current Location Request" bit set (i.e. the "EPS Location Information Request" bit is not set), the MME or SGSN or combined MME/SGSN shall set the Result-Code to DIAMETER_UNABLE_TO_COMPLY.

If the "Local Time Zone Request" bit was set the MME or SGSN if supported shall provide the Local Time Zone corresponding to the location (e.g. TAI or RAI) of the UE to the HSS.

If the MME or SGSN cannot fulfil the received request, e.g. due to a database error or any of the required actions cannot be performed, it shall set the Result-Code to DIAMETER_UNABLE_TO_COMPLY. If subscription data are received, the MME or SGSN shall mark the subscription record "Subscriber to be restored in HSS".

If trace data are received in the subscriber data, the MME or SGSN shall start a Trace Session. For details, see 3GPP TS 32.422 [23].

If the Ext-PDP-Type AVP is present in the PDP-Context AVP, the SGSN or combined MME/SGSN shall ignore the value of the PDP-Type AVP.

When receiving the IDR-Flags with the bit "Remove SMS Registration" set, the MME shall consider itself unregistered for SMS.

NOTE 2: As indicated in clause 7.3.31, if the UE-level access restriction "HO-To-Non-3GPP-Access Not Allowed" is set, the offload of PDN Connections to WLAN is not allowed for any APN.

When receiving the IDR-Flags with the "P-CSCF Restoration Request" bit set, the MME or SGSN or combined MME/SGSN shall execute the procedures for HSS-based P-CSCF Restoration, as described in 3GPP TS 23.380 [51] clause 5.4.

In the present clause, if the feature "Extended Reference IDs" (see clause 7.3.10) is supported by the HSS and the MME/SGSN, the term "SCEF Reference ID" shall refer to the content of the 64-bit long "SCEF-Reference-ID-Ext" AVP, and the term "SCEF Reference ID for Deletion" shall refer to the content of the 64-bit long "SCEF-Reference-ID-for-Deletion-Ext" AVP.

When receiving a Monitoring-Event-Configuration in the IDR:

– if the SCEF Reference ID for Deletion is present in the IDR, the MME or SGSN shall stop the detection of the Monitoring event related to the SCEF Reference ID for Deletion and SCEF-ID pair, and shall delete the corresponding Monitoring event configuration data;

– if the SCEF Reference ID is present in the IDR but not stored in the MME or SGSN, the MME or SGSN shall store the received Monitoring event configuration data related to the SCEF Reference ID and SCEF-ID pair, and shall start the detection for the specified Monitoring event(s).

– if the SCEF Reference ID is present in the IDR and stored in the MME or SGSN, the MME or SGSN shall replace the stored Monitoring event configuration data related to the SCEF Reference ID and SCEF-ID pair with the received information.

NOTE 3: In roaming scenarios the MME/SGSN can reply immediately to the HSS without waiting for the outcome of the interaction with the IWK-SCEF.

For the monitoring event configurations for which the configuration status have changed since the last status informed to the HSS, the MME/SGSN shall notify the HSS about the outcome of the interaction with the IWK-SCEF as specified in clause 5.2.5.1.2.

If the HSS indicates the support of Monitoring event feature to the MME/SGSN and the MME/SGSN supports Monitoring, the MME/SGSN shall include the Supported-Services AVP with Supported-Monitoring-Event included in the IDA command.

When receiving the Maximum-Response-Time in Monitoring-Event-Configuration in IDR, the MME shall use the Maximum-Response-Time as the Active Time for the usage of PSM in UE. If not, when the MME receives the Active-Time in subscription data, the MME shall use the Active-Time as the Active Time for the usage of PSM in UE.

When receiving AESE-Communication-Pattern AVP(s) within the Subscription-Data AVP with an SCEF Reference ID for which the MME has already stored data, it shall delete the stored data (CP set(s)) and store the received ones.

When receiving AESE-Communication-Pattern AVP(s) within the Subscription-Data AVP with one or more SCEF Reference ID for deletion the MME shall delete the data related to the indicated SCEF Reference ID.

If the MME and the UE support an Attach without PDN connection (i.e. EMM-REGISTERED without PDN connection) and the PDN-Connection-Restricted flag is set in the received Subscription-Data-Flags AVP, the MME shall not establish any non-emergency PDN connection and shall tear down any existing non-emergency PDN connection for this user.

If the subscription data received for the user includes the Preferred-Data-Mode AVP, for an IP APN configuration or for a non-IP APN configuration with SGi based delivery, then the MME should (if the subscriber is not roaming) or may (if the subscriber is roaming) take into account the subscription data, in addition to local policies and the UE’s Preferred Network Behaviour, to determine whether to transmit the traffic associated with this APN over the User Plane and/or over the Control Plane. Otherwise, the MME shall make this determination based on local policies and the UE’s Preferred Network Behaviour only.

If the MME subscription data received for the user includes the Emergency-Info AVP, the MME shall use the PDN-GW identity contained in such AVP as the PDN-GW used to establish emergency PDN connections with the emergency APN, for non-roaming authenticated UEs requesting the handover of an emergency PDN connection if the MME is configured to use a dynamic PDN-GW for emergency services for such user.

When receiving V2X-Subscription-Data in the IDR, the MME shall determine whether the UE is authorized to use V2X communication over PC5 according to V2X subscription data and UE provided network capability. If the UE is authorized to use V2X communication over PC5, the MME shall store the "V2X service authorized" indication together with the UE AMBR used for PC5 interface (i.e. UE-PC5-AMBR), and provide such information to the eNodeB when needed.

If the MME/SGSN receives from the HSS an Insert Subscriber Data request without the bit set for "NR as Secondary RAT" in the Feature-List AVP, the MME/SGSN, based on local policy, may restrict access for NR as secondary RAT when all relevant entities except HSS supports it.

If the MME receives from the HSS Insert Subscriber Data request containing in the subscription data the Core-Network-Restrictions AVP with the bit "5GC not allowed" set, the MME shall restrict mobility towards 5GC.

When receiving Paging-Time-Window AVPs within the Subscription-Data AVP, the MME or SGSN shall replace stored information (if any) with the received information rather than add the received information to the stored information.

5.2.2.1.3 Detailed behaviour of HSS

The HSS shall make use of this procedure to replace a specific part of the user data stored in the MME or SGSN with the data sent, or to add a specific part of user data to the data stored in the MME or SGSN. The HSS shall also make use of this procedure to indicate to the MME that it is no longer registered for SMS.

NOTE: When a Cancel Location message is required for other reasons, the use of IDR to indicate that the MME is no longer registered for SMS is not needed (see clause 5.2.1.2).

Subscriber-Status AVP shall be present in the Subscription-Data AVP, sent within IDR, if the current value in the MME or SGSN needs to be changed. To remove all Operator Determined Barring Categories the Subscriber-Status shall be set to "SERVICE_GRANTED". If Subscriber-Status AVP is present and set to OPERATOR_DETERMINED_BARRING, the Operator-Determined-Barring AVP or HPLMN-ODB AVP shall also be present in the Subscription-Data AVP.

Access-Restriction-Data AVP shall be present within the Subscription-Data AVP send within an IDR if the information stored in the MME or SGSN needs to be modified.

APN-OI-Replacement AVP shall be present in the Subscription-Data AVP sent within an IDR, if the UE level APN-OI-Replacement has been added or modified in the HSS.

The APN-Configuration-Profile AVP shall be present in the Subscription-Data AVP sent within an IDR if the Context-Identifier associated with the default APN configuration is changed or at least one APN-Configuration is added or modified by the HSS. If the default APN is changed in the HSS, the APN-Configuration-Profile AVP shall contain the Context-Identifier associated with the default APN and the APN-Configuration AVP for the default APN. The default APN Configuration shall not contain the Wildcard APN (see 3GPP TS 23.003 [3], clause 9.2); the default APN shall always contain an explicit APN.

If the GPRS-Subscription-Data-Indicator information has been previously received as set in the ULR-Flags during update location procedure for the SGSN or combined MME/SGSN, the HSS shall make use of this procedure to replace the GPRS Subscription Data stored in the SGSN or combined MME/SGSN with the data sent or to add a PDP-Context to the data stored in the SGSN or combined MME/SGSN.

ProSe-Subscription-Data AVP shall be present in the Subscription-Data AVP sent within an IDR, if the ProSe Subscription data has been added or modified in the HSS.

If the HSS receives a message (e.g. via MAP ATM or Sh Sh-Subs-Notif) from a Service Related Entity (e.g. IP-SM-GW) indicating that the UE is unreachable,

– the HSS shall associate the subscription to UE reachability of the service-related entity to the URRP-MME and the URRP-SGSN parameters (if not already done)

– and if the URRP-MME and/or the URRP-SGSN parameters were not already set (i.e. at least one service-related entity already listed as subscribed), the HSS shall

– set the URRP-MME and/or URRP-SGSN parameters and

– send an IDR command to the registered MME and/or to the registered SGSN including the "UE Reachability Request flag" in the IDR Request Flags in order to request the MME and/or SGSN to notify the HSS when the UE becomes reachable again, unless the HSS knows from the previous ULR command that the registered MME and/or the registerd SGSN do not support UE reachability notifications.

If the IDR is sent for the only purpose to request the MME and/or SGSN about the UE reachability status notification, the Subscription-Data AVP shall be included empty.

If the HSS has received a message from a service related entity requesting EPS User State and/or EPS Location Information without the Serving Node Indication IE, the HSS shall set the "EPS User State Request" bit and/or "EPS Location Information Request" bit respectively in the IDR-Flags. The HSS may optionally also set the "Current Location Request" bit along with the "EPS Location Information Request" bit in the IDR-Flags, if the most up-to-date set of information is needed, unless the HSS knows from the previous ULR command that the registered MME and/or the registered SGSN do not support State/Location Information retrieval. If the IDR is sent only for the purpose of requesting the MME or the SGSN User State or Location Information, the Subscription-Data AVP included shall be empty.

If the HSS cannot request EPS Location Information from the MME/SGSN e.g. because the UE is purged from the MME/SGSN, the HSS may make use of stored EPS Location information received in a previous IDA or PUR message.

If the HSS has received a message from an AS requesting the current access network’s support status of "IMS Voice over PS Sessions", and there is no indication about homogeneous support of IMS Voice over PS Sessions in all the serving nodes currently registered in HSS for the UE, the HSS shall set the "T-ADS Data Request flag" in the IDR Request Flags, unless the HSS knows from the previous ULR command that the registered MME and/or the registered SGSN do not support T-ADS data retrieval. If the IDR is sent for the only purpose to retrieve the "IMS Voice over PS Sessions Supported" indication from the MME or SGSN, the Subscription-Data AVP included shall be empty.

If the HSS has received a message from an AS requesting the Local Time Zone, the HSS shall set the " Local Time Zone Request" bit in the IDR-Flags, unless the HSS knows from the previous ULR command that the registered MME and/or the registered SGSN do not support Local Time Zone retrieval. If the IDR is sent only for the purpose of requesting the Local Time Zone, the Subscription-Data AVP included shall be empty.

If the HSS received an indication in a former ULR command from the MME or SGSN about homogeneous support of IMS Voice over PS Sessions in all TA/RAs associated to that serving node, it may use this information to skip the retrieval of T-ADS data. This can only be done if all the registered serving nodes in HSS for the UE indicated in ULR the same type of homogeneous support (i.e. both serving nodes indicated "SUPPORTED", or both serving nodes indicated "NOT_SUPPORTED"); otherwise, the retrieval of T-ADS data shall be done, to receive the time of the last radio contact with the UE.

All APN and PGW-ID pairs stored in the HSS not associated with an explicit APN subscription, (i.e. the access to that APN has been authorized as a consequence of having the Wildcard APN in the user subscription), shall be included by the HSS inside the APN context of the Wildcard APN, as multiple instances of the Specific-APN-Info AVP.

When receiving an Insert Subscriber Data answer with "SGSN Area Restricted" the HSS shall set the SGSN area restricted flag as "SGSN area restricted".

Subscribed-VSRVCC AVP may be present within the Subscription-Data AVP sent within an ISR only if the user is subscribed to the SRVCC and vSRVCC.

If the HSS determines that the MME shall be unregistered for SMS it shall set the "Remove SMS Registration" bit in the IDR-Flags. If the IDR is sent for the only purpose to indicate that the MME is no longer registered for SMS, the Subscription-Data AVP shall be included empty.

If the HSS needs to request to the MME/SGSN the execution of the HSS-based P-CSCF restoration procedure, as described in 3GPP TS 23.380 [51] clause 5.4, the HSS shall set the "P-CSCF Restoration Request" bit in the IDR-Flags, if supported by the MME/SGSN. If the IDR is sent only for the purpose of requesting the execution of the HSS-based P-CSCF restoration procedures, the Subscription-Data AVP included shall be empty.

If the HSS receives a SCEF request to configure Monitoring events for the UE to be handled by the MME/SGSN or receives a SCEF request for deleting Monitoring events for the UE in the MME/SGSN, the HSS shall include Monitoring-Event-Configuration AVP(s) in the Subscription-Data AVP sent within the IDR. If the HSS has registered both an MME and an SGSN as serving nodes for a given user, and both nodes are not part of a same combined MME/SGSN node, the HSS shall send the Monitoring-Event-Configuration AVP(s) to each one of the serving nodes that supports the Monitoring event service. If the HSS receives the IDA with Monitoring-Event-Report AVP(s), the HSS shall forward the Monitoring-Event-Report AVP(s) to the SCEF associated to those Monitoring events.

If the HSS does not receive a SCEF request to configure Monitoring events for the UE to be handled by the MME/SGSN and does not receive an Active Time with the Suggested-Network-Configuration AVP , the HSS may send an O&M configured desired Active Time value within the Active-Time AVP.

If the HSS receives a Supported-Services AVP it shall only trigger those services which are supported by the MME/SGSN.

If the HSS has previously received over SWx (see 3GPP TS 29.273 [59]) the identity of the PDN-GW to be used for the establishment of emergency PDN connections, it shall send it to the registered MME (if any) in the IDR command as part of the Subscription-Data AVP (in the Emergeny-Info AVP).

If V2X subscription data has been added or modified in the HSS, the HSS shall include the V2X-Subscription-Data AVP in the Subscription-Data AVP sent within an IDR.

If the External-Identifier associated with Monitoring Event Configuration for the UE has been added or modified in the HSS and the MME/SGSN supports the "External-Identifier" feature, the HSS shall include the External-Identifier AVP in the Subscription-Data AVP. When multiple External Identifiers are defined for a same subscription, the HSS shall send a default External Identifier in the External-Identifier AVP of the Subscription-Data AVP, and shall include a specific External Identifier (if different from the default External Identifier) associated to each Monitoring Event Configuration in the External-Identifier AVP of each Monitoring-Event-Configuration AVP occurrence inside the Subscription-Data AVP.

The Aerial-UE-Subscription-Information AVP may be present within the Subscription-Data AVP sent within an IDR only if the user has Aerial UE subscription information.

If Core Network Restrictions in subscription data (5GC allowed/not allowed) has been added or modified in the HSS, the HSS shall include the Core-Network-Restrictions AVP in the Subscription-Data AVP sent within an IDR.

5.2.2.2 Delete Subscriber Data

5.2.2.2.1 General

This procedure shall be used between the MME and the HSS and between the SGSN and the HSS, to remove some data of the HSS user profile stored in the MME or SGSN. The procedure shall be invoked by the HSS and it corresponds to the functional level operation Delete Subscriber Data (see 3GPP TS 23.401 [2]).

It shall be used to remove:

– a subset (wich may or may not be the complete set of APN configurations) of the APN Configuration Profile for the subscriber from the SGSN or combined MME/SGSN;

– a proper subset (i.e. a subset that is not equal to the complete set of APN configurations and does not contain the default APN configuration) of the APN Configuration Profile for the subscriber from the MME;

– the regional subscription;

– the subscribed charging characteristics;

– Session Transfer Number for SRVCC;

– trace data;

– ProSe subscription data;

– Reset-IDs;

– MSISDN;

– UE Usage Type;

– V2X subscription data.

– External Identifier(s).

If the HSS knows that the UE has attached to the MME and SGSN parts of the same combined MME/SGSN via both E-UTRAN and UTRAN/GERAN(refer to clause 5.2.1.1.2, 5.2.1.1.3 for further details), the HSS should invoke this procedure for a single time to remove some or all data of the HSS user profile stored in the combined MME/SGSN, i.e. not invoke this procedure for each of the MME and the SGSN registered respectively.

If the Node-Type-Indicator information has been previously received as cleared in the ULR-Flags and if the MME has not been registered for SMS during update location procedure for the MME, the HSS may skip any removal of the SMS related subscription data and consequently does not have to make use of the Delete Subscriber Data procedure to update the SMS subscription data in the MME.

This procedure is mapped to the commands Delete-Subscriber-Data-Request/Answer (DSR/DSA) in the Diameter application specified in clause 7.

Table 5.2.2.2.1/1 specifies the involved information elements for the request.

Table 5.2.2.2.1/2 specifies the involved information elements for the answer.

Table 5.2.2.2.1/1: Delete Subscriber Data Request

Information element name	Mapping to Diameter AVP	Cat.	Description
IMSI	User-Name (See IETF RFC 6733 [61])	M	This information element shall contain the user IMSI, formatted according to 3GPP TS 23.003 [3], clause 2.2.
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
DSR Flags (See 7.3.25)	DSR-Flags	M	This Information Element shall contain a bit mask. See 7.3.25 for the meaning of the bits.
Trace Reference (See 7.3.64)	Trace- Reference	C	This parameter shall contain the same value as used for the activation of the Trace Session. This element shall be present only if the "Trace Data Withdrawal" bit is set in the DSR-Flags.
Context Identifier (See 7.3.27)	Context-Identifier	C	This parameter shall identify the PDN subscription context or GPRS-PDP context that shall be deleted. This element shall be present only if the "PDN subscription contexts Withdrawal" bit or the "PDP context withdrawal" bit is set in the DSR-Flags. In the "PDN subscription contexts Withdrawal" case, the Context-Identifier shall not be associated with the default APN configuration. For the compatibility with the MAP protocol as defined in the 3GPP TS 29.002 [24], this parameter shall not have a value of zero.
TS Code List (See 7.3.100)	TS-Code	C	This parameter shall contain the teleservice codes that are to be deleted from the subscription. This element shall be present only if the "SMS Withdrawal" bit is set in the DSR-Flags and the SMS related teleservice codes are to be deleted.
SS Code List (See 7.3.87)	SS-Code	C	This parameter shall contain the supplementary service codes that are to be deleted from the subscription. This element shall be present only if the "SMS Withdrawal" bit is set or the "LCS Withdrawal" bit is set in the DSR-Flags.
SCEF-Id (See 3GPP TS 29.336 [54])	SCEF-ID	C	This parameter shall contain the identity of the SCEF to which monitoring events that are to be deleted are associated. This element shall be present if the "Delete monitoring events" bit is set in the DSR-Flags.
eDRX Related RAT List	eDRX-Related-RAT	C	This parameter shall contain the RAT types for which the eDRX Cycle Lengths is to be deleted from the subscription. This element shall be present only if the "eDRX-Cycle-Length-Withdrawal" bit is set in the DSR-Flags and the corresponding eDRX Cycle Lengths are to be deleted. If the "eDRX-Cycle-Length-Withdrawal" bit is set in DSR-Flags, but the eDRX-Related-RAT AVP is absent in this command, the MME/SGSN shall delete the stored eDRX cycle lengths for all RATs.
External Identifiers	External-Identifiers	O	If present, this parameter shall contain the External Identifier(s) to be deleted from the subscriber data; the MME/SGSN shall also delete those monitoring events that include an External-Identifier AVP in their event configuration matching any of the External-Identifiers in this IE. This IE shall be absent if the "External-Identifier-Withdrawal" bit is not set in the DSR-Flags. If this IE is absent, and "External-Identifier-Withdrawal" bit is set in DSR-Flags, the MME/SGSN shall delete the default External-Identifier in the Subscription-Data AVP and it shall also delete all monitoring events that include an External-Identifier AVP in their event configuration.

Table 5.2.2.2.1/2: Delete Subscriber Data Answer

Information element name	Mapping to Diameter AVP	Cat.	Description
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Result (See 7.4)	Result-Code / Experimental-Result	M	This IE shall contain the result of the operation. The Result-Code AVP shall be used to indicate success / errors as defined in the Diameter base protocol (see IETF RFC 6733 [61]). The Experimental-Result AVP shall be used for S6a/S6d errors. This is a grouped AVP which shall contain the 3GPP Vendor ID in the Vendor-Id AVP, and the error code in the Experimental-Result-Code AVP. The following errors are applicable in this case: – User Unknown
DSA Flags (See 7.3.26)	DSA-Flags	C	This Information Element shall contain a bit mask. See 7.3.26 for the meaning of the bits.

5.2.2.2.2 Detailed behaviour of the MME and the SGSN

When receiving a Delete Subscriber Data request, the MME or SGSN shall check whether the IMSI is known.

If it is not known, a result code of DIAMETER_ERROR_USER_UNKNOWN shall be returned.

If it is known, but the Context-Identifier is associated with the default APN configuration, the MME shall not delete the PDN subscription context, and return an error with a Result-Code set to DIAMETER_UNABLE_TO_COMPLY. Otherwise, the MME or SGSN shall delete the corresponding data according to the indication as sent in the request, and acknowledge the Delete Subscriber Data message by returning a Delete Subscriber Data Answer.

If an MME receives a Delete Subscriber Data Request with the "Complete APN Configuration Profile Withdrawal" bit set in the DSR-Flags AVP, it shall return an error with a Result-Code set to DIAMETER_UNABLE_TO_COMPLY.

If the deletion of the subscription data succeeds in the MME or SGSN, the Result-Code shall be set to DIAMETER_SUCCESS.

If the Regional Subscription is deleted from the subscription data, the SGSN shall check for its routing areas whether they are allowed or not. If the entire SGSN area is restricted, SGSN shall report it to the HSS by returning the "SGSN Area Restricted" indication within the DSA flags.

If the EPS Subscription Data is deleted from the subscription data, the MME or SGSN shall check whether all EPS Subscription Data for the subscriber is deleted or if only a subset of the stored EPS Subscription Data for the subscriber is deleted, the MME or SGSN may then deactivate the associated affected active EPS bearers.

If the Subscribed Charging Characteristics are deleted from the subscription data, the Gn/Gp-SGSN shall maintain the existing Subscribed Charging Characteristics throughout the lifetime of the existing MM and PDP contexts, see 3GPP TS 32.251 [33].

If the Subscribed Charging Characteristics are deleted from the subscription data, the MME or S4-SGSN shall maintain the existing Subscribed Charging Characteristics throughout the lifetime of the existing IP CAN bearer, see 3GPP TS 32.251 [33].

If the MSISDN is deleted from the subscription data, the MME or SGSN shall maintain the existing MSISDN throughout the lifetime of the existing PDN connections that were established prior to the deletion of the MSISDN (i.e., other network nodes, such as PDN-GW, are not informed of such deletion for the existing PDN connections). The MME/SGSN shall also delete those monitoring events related to the deleted MSISDN.

If the MME or SGSN cannot fulfil the received request for other reasons, e.g. due to a database error, it shall set the Result-Code to DIAMETER_UNABLE_TO_COMPLY. In this case, the MME or SGSN shall mark the subscription record "Subscriber to be restored in HSS".

If trace data are deleted from the subscription data, the MME or SGSN shall deactivate the Trace Session identified by the trace reference. For details, see 3GPP TS 32.422 [23].

If External Identifiers are requested to be deleted from the subscription data, the MME/SGSN shall check whether any of the identifiers to be deleted match the default External-Identifier provided by HSS in the Subscrition-Data AVP (unless all External Identifiers are requested to be deleted from the subscription); in such case, the MME/SGSN shall reject the request and return an error with a Result-Code set to DIAMETER_UNABLE_TO_COMPLY (if default External Identifier is wanted to be deleted, no External Identifier must be provided in the request). The MME/SGSN shall also delete those monitoring events related to the deleted External Identifiers, or all monitoring events associated to any External Identifier if default External Identifier is deleted.

5.2.2.2.3 Detailed behaviour of the HSS

The HSS shall make use of this procedure to remove deleted subscription data from the MME or SGSN.

The HSS shall make use of this procedure to remove deleted GPRS Subscription Data from the SGSN or combined MME/SGSN if the GPRS-Subscription-Data-Indicator information has been previously received as set in the ULR-Flags during update location procedure for the MME.

The HSS shall not set the "Complete APN Configuration Profile Withdrawal" bit in the DSR-Flags AVP when sending a Delete Subscriber Data Request to an MME, since the default APN shall always be present in an MME.

When receiving a Delete Subscriber Data Answer with "SGSN Area Restricted" the HSS shall set the SGSN area restricted flag as "SGSN area restricted".

5.2.3 Authentication Procedures

5.2.3.1 Authentication Information Retrieval

5.2.3.1.1 General

The Authentication Information Retrieval Procedure shall be used by the MME and by the SGSN to request Authentication Information from the HSS.

This procedure is mapped to the commands Authentication-Information-Request/Answer (AIR/AIA) in the Diameter application specified in clause 7.

Table 5.2.3.1.1/1 specifies the involved information elements for the request.

Table 5.2.3.1.1/2 specifies the involved information elements for the answer.

Table 5.2.3.1.1/1: Authentication Information Request

Information element name	Mapping to Diameter AVP	Cat.	Description
IMSI	User-Name (See IETF RFC 6733 [61])	M	This information element shall contain the user IMSI, formatted according to 3GPP TS 23.003 [3], clause 2.2.
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Requested E-UTRAN Authentication Info (See 7.3.11)	Requested-EUTRAN-Authentication-Info	C	This information element shall contain the information related to authentication requests for E-UTRAN.
Requested UTRAN/GERAN Authentication Info (See 7.3.12)	Requested-UTRAN-GERAN Authentication-Info	C	This information element shall contain the information related to authentication requests for UTRAN or GERAN.
Visited PLMN ID (See 7.3.9)	Visited-PLMN-ID	M	This IE shall contain the MCC and the MNC of the visited PLMN, see 3GPP TS 23.003 [3].
AIR Flags (See 7.3.201)	AIR-Flags	O	This IE, if present, contains a bit mask. See clause 7.3.201 for the meaning of the different bits.

Table 5.2.3.1.1/2: Authentication Information Answer

Information element name	Mapping to Diameter AVP	Cat.	Description
Result (See 7.4)	Result-Code / Experimental-Result	M	This IE shall contain the result of the operation. This IE shall contain the Result-Code AVP shall be used to indicate success / errors as defined in the Diameter base protocol (see IETF RFC 6733 [61]). The Experimental-Result AVP shall be used for S6a/S6d errors. This is a grouped AVP which shall contain the 3GPP Vendor ID in the Vendor-Id AVP, and the error code in the Experimental-Result-Code AVP. The following errors are applicable in this case: – User Unknown – Unknown EPS Subscription – Authentication Data Unavailable
Error-Diagnostic	Error-Diagnostic	O	If the Experimental Result indicated "Unknown EPS Subscription", Error Diagnostic may be present to indicate whether or not GPRS subscription data are subscribed (i.e. whether or not Network Access Mode stored in the HSS indicates that only CS service is allowed).
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Authentication Info (See 7.3.17)	Authentication-Info	C	This IE shall contain the Authentication Vectors.
UE Usage Type (See 7.3.202)	UE-Usage-Type	C	This IE shall be present if the HSS supports the Dedicated Core Networks feature, and the "Send UE Usage Type" flag was set in the AIR-Flags AVP in the AIR command, and this information is available in the user subscription. If present, this IE shall contain the UE Usage Type of the subscriber (see clause 7.3.202).

5.2.3.1.2 Detailed behaviour of the MME and the SGSN

The MME or SGSN shall make use of this procedure in order to retrieve the Authentication Vectors from the HSS.

If the MME or SGSN supports Emergency services for users in limited service state, and the user’s IMSI is not available from the UE, or the user’s IMSI is marked as unauthenticated, the MME or SGSN shall not make use of the Authentication Information Retrieval procedure.

If the request is triggered by a synchronization failure during E-UTRAN authentication, the MME or combined MME/SGSN shall include the Re-Synchronization Information in the Requested-EUTRAN-Authentication-Info AVP in the request.

If the request is triggered by a synchronization failure during UTRAN or GERAN authentication, the SGSN or combined MME/SGSN shall include the Re-Synchronization Information in the Requested-UTRAN-GERAN-Authentication-Info AVP in the request.

Re-Synchronization Information shall not be present in both the Requested-EUTRAN-Authentication-Info AVP and the Requested-UTRAN-GERAN-Authentication-Info AVP.

A stand alone MME shall include the Requested-EUTRAN-Authentication-Info AVP and shall not include the Requested-UTRAN-GERAN-Authentication-Info AVP in the request. The Immediate-Response-Preferred AVP should be present if a EUTRAN-Vector is needed for immediate use.

A stand alone SGSN shall not include the Requested-EUTRAN-Authentication-Info AVP and shall include the Requested-UTRAN-GERAN-Authentication-Info AVP in the request. The Immediate-Response-Preferred AVP should be present if a UTRAN/GERAN-Vector is needed for immediate use.

A combined MME/SGSN may include both the Requested-EUTRAN-Authentication-Info AVP and the Requested-UTRAN-GERAN-Authentication-Info AVP in the request. If both the Requested-EUTRAN-Authentication-Info AVP and the Requested-UTRAN-GERAN-Authentication-Info AVP are present in the request, the Immediate-Response-Preferred AVP shall be present if the requested authentication vectors are needed for immediate use. The content of the Immediate-Response-Preferred AVP shall correspond to the access type which the UE is currently to be authenticated. The Immediate-Response-Preferred AVP shall not be present in both the Requested-EUTRAN-Authentication-Info AVP and the Requested-UTRAN-GERAN-Authentication-Info AVP. The presence of an Immediate-Response-Preferred AVP shall indicate that a vector is needed for immediate use.

When EUTRAN-AVs and UTRAN-AVs or GERAN-AVs are requested, presence of Immediate-Response-Preferred AVP within the Requested-EUTRAN-Authentication-Info AVP shall indicate that EUTRAN-AVs are requested for immediate use in the MME/SGSN; presence of Immediate-Response-Preferred AVP within the Requested-UTRAN-GERAN-Authentication-Info AVP shall indicate that UTRAN-AVs or GERAN-AVs are requested for immediate use in the MME/SGSN. It may be used by the HSS to determine the number of vectors to be obtained from the AuC and the number of vectors downloaded to the MME or SGSN.

If the MME or SGSN supports the Dedicated Core Networks functionality, and the MME or SGSN needs to retrieve the UE Usage Type from the HSS, it shall set the "Send UE Usage Type" flag in the AIR-Flags AVP in the AIR command.

When receiving an Authentication Information response from the HSS, the MME or SGSN shall check the Result Code. If it indicates success and Authentication Information is present in the result, the MME or SGSN shall use the received vectors. For details see 3GPP TS 33.401 [5].

If the MME or SGSN supports Emergency services for users in limited service state, the MME or SGSN shall proceed even if the Authentication Information Retrieval procedure has failed. In this case, the MME or SGSN shall mark the user’s IMSI as unauthenticated.

Vectors with lower Item Number should be used before Vectors with higher Item Number are used in the MME or SGSN. For Vectors received within different requests those received by the earlier request should be used before those received by the later request.

5.2.3.1.3 Detailed behaviour of the HSS

When receiving an Authentication Information request the HSS shall check whether subscription data exists for the IMSI.

If the HSS determines that there is not any type of subscription for the IMSI (including EPS, GPRS and CS subscription data), a result code of DIAMETER_ERROR_USER_UNKNOWN shall be returned.

If the Authentication Information Request contains a Requested-EUTRAN-Authentication-Info AVP but no Requested-UTRAN-GERAN-Authentication-Info AVP, and the subscriber has not any APN configuration, the HSS shall return a Result Code of DIAMETER_ERROR_UNKNOWN_EPS_SUBSCRIPTION.

If the Authentication Information Request contains a Requested-UTRAN-GERAN-Authentication-Info AVP but no Requested-EUTRAN-Authentication-Info AVP, and the subscriber has neither an APN configuration profile nor GPRS subscription data, the HSS shall return a Result Code of DIAMETER_ERROR_UNKNOWN_EPS_SUBSCRIPTION.

If the Authentication Information Request contains both Requested-EUTRAN-Authentication-Info AVP and Requested-UTRAN-GERAN-Authentication-Info AVP, and the Requested-EUTRAN-Authentication-Info AVP does not contain an Immediate-Response-Preferred AVP, and the subscriber has not any APN configuration, the HSS shall not return E-UTRAN vectors.

If the Authentication Information Request contains both Requested-EUTRAN-Authentication-Info AVP and Requested-UTRAN-GERAN-Authentication-Info AVP, and the Requested-EUTRAN-Authentication-Info AVP contains an Immediate-Response-Preferred AVP, and the subscriber does not have any APN configuration, the HSS shall return a Result Code of DIAMETER_ERROR_UNKNOWN_EPS_SUBSCRIPTION.

If EUTRAN-Authentication-Info is requested, the HSS shall check if serving nodes within the realm identified by the received Origin-Realm AVP are allowed to request authentication information for use in the serving network identified by the received Visited-PLMN-Id AVP.

The HSS shall then request the AuC to generate the corresponding requested Authentication Vectors (AVs). Subject to load considerations and/or other implementation specific considerations which may be based on the presence of an Immediate-Response-Preferred AVP, less AVs than the requested number of AVs may be generated.

If EUTRAN-Authentication-Info is requested, when receiving AVs from the AuC, the HSS shall generate the KASME before sending the response to the MME or combined MME-SGSN.

If the AuC is unable to calculate any corresponding AVs due to unallowed attachment for the UE, e.g. the UE is attaching via E-UTRAN with a SIM card equipped, the HSS shall return an error DIAMETER_AUTHORIZATION_REJECTED, the HSS shall not return any AV to the requesting node in the response. Otherwise, if no corresponding pre-computed AV is available, and the AuC is unable to calculate any corresponding AVs due to unknown failures, such as the internal database error, the result code shall be set to DIAMETER_AUTHENTICATION_DATA_UNAVAILABLE. The MME or the SGSN may request authentication vectors again.

For details see 3GPP TS 33.401 [5]. KASME generation is not performed before sending the response to the SGSN.

If the Requested-EUTRAN-Authentication-Info AVP is present in the request, the HSS shall download E-UTRAN authentication vectors to the MME. If the Requested-UTRAN-GERAN-Authentication-Info AVP is present in the request, the HSS shall download UTRAN or GERAN authentication vectors to the SGSN.

If the Immediate Response Preferred parameter has been received, the HSS may use it together with the number of requested vectors and the number of vectors stored in the HSS that are pre-computed to determine the number of vectors to be obtained from the AuC. The HSS may return less number of vectors than requested to the MME or SGSN. If both the Requested-EUTRAN-Authentication-Info AVP and the Requested-UTRAN-GERAN-Authentication-Info AVP are in the request, and one of them includes the Immediate Response Preferred parameter, the HSS may omit the vectors request that are not for immediate use. If both the Requested-EUTRAN-Authentication-Info AVP and the Requested-UTRAN-GERAN-Authentication-Info AVP are in the request, and both of them includes the Immediate Response Preferred parameter, the HSS may return E-UTRAN authentication vectors and UTRAN or GERAN authentication vectors. KASME is always computed for each E-UTRAN vector due to the PLMN-binding before sending the response to the MME independent of the presence of the Immediate Response Preferred parameter.

If the Re-Synchronization-Info AVP has been received, the HSS shall check the AUTS parameter before sending new authentication vectors to the MME or the SGSN. For details see 3GPP TS 33.102 [18]. If both the Requested-EUTRAN-Authentication-Info AVP and the Requested-UTRAN-GERAN-Authentication-Info AVP are in the request, and both of them include the Re-Synchronization-Info AVP, the HSS shall not check the AUTS parameter and return the result code of DIAMETER_UNABLE_TO_COMPLY. Any authentication vectors shall not be sent by the HSS to the requesting node in the response.

If more than one EPS or UTRAN or GERAN Vector is to be included within one Authentication-Info AVP, the Item-Number AVP shall be present within each Vector.

If the HSS supports the Dedicated Core Networks functionality, and the MME or SGSN has set the "Send UE Usage Type" flag in the AIR-Flags AVP in the AIR command:

– if the UE Usage Type value is available in the subscription data of the user:

– if the Immediate Response Preferred parameter is not present in the Requested-EUTRAN-Authentication-Info nor in the Requested-UTRAN-GERAN-Authentication-Info, the HSS may return no authentication vectors in the response; the HSS shall then return the result code DIAMETER_SUCCESS and may return the generated AVs (if any) to the MME or SGSN;

– the HSS shall include the UE-Usage-Type AVP in the AIA response command if the result code is DIAMETER_SUCCESS or DIAMETER_AUTHENTICATION_DATA_UNAVAILABLE.

– if the UE Usage Type value is not available in the subscription data of the user, the HSS shall answer as if the MME/SGSN had not requested the UE Usage Type parameter.

5.2.4 Fault Recovery Procedures

5.2.4.1 Reset

5.2.4.1.1 General

The Reset Procedure shall be used by the HSS, after a restart, to indicate to the MME and to the SGSN that a failure has occurred.

The Reset Procedure may also be used by the HSS as part of operation and maintenance actions e.g. to allow planned HSS outage without service interruption, or to update subscription data shared by multiple subscribers.

This procedure is mapped to the commands Reset-Request/Answer (RSR/RSA) in the Diameter application specified in clause 7.

Table 5.2.4.1.1/1 specifies the involved information elements for the request.

Table 5.2.4.1.1/2 specifies the involved information elements for the answer.

Table 5.2.4.1.1/1: Reset Request

Information element name	Mapping to Diameter AVP	Cat.	Description
User Id List (See 7.3.50)	User-Id	O	This IE shall contain a list of User-Ids where a User-Id comprises the leading digits of an IMSI (i.e. MCC, MNC, leading digits of MSIN) and it shall identify the set of subscribers whose IMSIs begin with the User-Id. The HSS may include this information element if the occurred failure is limited to subscribers identified by one or more User-Ids.
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Reset-IDs (See 7.3.184)	Reset-ID	O	If present, this information element identifies the set of impacted subscribers.
Subscription Data (See 7.3.2)	Subscription-Data	O	If the Reset Procedure is used to add/ modify subscription data shared by multiple subscribers, this Information Element shall contain the part of the subscription profile that either is to be added to the subscription profile stored in the MME or SGSN or combined MME/SGSN or is replacing a part of the subscription profiles of the impacted subscribers stored in the MME or SGSN. Shall be absent if Subscription-Data-Deletion AVP is present. Shall be absent if Reset-ID AVP is absent
Subscription Data Deletion (See 7.3.208)	Subscription-Data-Deletion	O	If the Reset Procedure is used to delete subscription data shared by multiple subscribers, this Information Element shall contain identifications of the part of the subscription profile that is to be deleted from the subscription profiles of the impacted subscribers stored in the MME or SGSN or combined MME/SGSN. Shall be absent if Subscription-Data AVP is present. Shall be absent if Reset-ID AVP is absent

Table 5.2.4.1.1/2: Reset Answer

Information element name

Mapping to Diameter AVP

Cat.

Description

Supported Features

(See 3GPP TS 29.229 [9])

Supported-Features

If present, this information element shall contain the list of features supported by the origin host.

Result

(See 7.4)

Result-Code / Experimental-Result

This IE shall contain the result of the operation.

The Result-Code AVP shall be used to indicate success / errors as defined in the Diameter base protocol (see IETF RFC 6733 [61]).

The Experimental-Result AVP shall be used for S6a/S6d errors. This is a grouped AVP which shall contain the 3GPP Vendor ID in the Vendor-Id AVP, and the error code in the Experimental-Result-Code AVP.

There are no Experimental-Result codes applicable for this command.

5.2.4.1.2 Detailed behaviour of the MME and the SGSN

When receiving a Reset message neither containing Subscription-Data nor Subscription-Data-Deletion the MME or SGSN or combined MME/SGSN shall mark all impacted subscriber records "Location Information Confirmed in HSS " as "Not Confirmed".

When receiving a Reset message containing Subscription-Data or Subscription-Data-Deletion the MME or SGSN or combined MME/SGSN shall update all impacted subscriber records accordingly, i.e. each impacted subscriber record is updated as if an individual IDR or DSR for that subscriber was received; for details see clauses 5.2.2.1.2 and 5.2.2.2.2. The MME or SGSN or combined MME/SGSN shall not mark successfully updated subscriber records "Location Information Confirmed in HSS " as "Not Confirmed". If an impacted subscriber record cannot be updated for any reason (e.g. the updated data is considered not shareable by the MME or SGSN or combined MME/SGSN, or the update requires an individual acknowledgement to be sent to the HSS), the MME or SGSN or combined MME/SGSN shall mark that record "Location Information Confirmed in HSS " as "Not Confirmed".

NOTE: Which subscription data are considered by the MME or SGSN or combined MME/SGSN not shareable by multiple subscribers is implementation specific.

If the update of shared subscription data requires only local updates in the MME or SGSN or combined MME/SGSN (i.e., the update of the profile does not imply to initiate any signalling interaction towards other network nodes), the updates should be performed immediately (e.g. deleting an Operator Determined Barring).

If the update of shared subscription data implies initiating a signalling interaction towards other nodes (e.g. towards the PGW/PCRF for the change of an APN configuration parameter, such as APN-AMBR), depending on the UE’s state the following shall apply:

– If the UE is in CONNECTED state, the updates shall be performed immediately including signalling towards other nodes.

– If the UE is in IDLE state, the signalling towards other nodes should be deferred to the next authenticated radio contact with that UE.

NOTE: The rational for the recommendation to defer signalling towards other nodes until the next authenticated radio contact is to consider impacts to the network only when the updates are required, and to spread the signalling towards other nodes over some time, based on user’s activity.

In both cases, to avoid high processing/signalling load resulting from shared subscription data update, processing/signalling actions resulting from data updates in the MME or SGSN or combined MME/SGSN may take a maximum operator configuration-depending time.

If the Reset-IDs IE is supported and received, the MME or SGSN or combined MME/SGSN shall make use of the Reset-IDs (together with the HSS’s realm) in order to determine which subscriber records are impacted (i.e. check whether at least one received Reset-ID is associated with the subscriber); otherwise the MME or SGSN or combined MME/SGSN shall make use of the HSS Identity received in the Origin-Host AVP (by comparing it with the value stored after successful ULA) and may make use of the received User-Id-List (if any) in order to determine which subscriber records are impacted.

At the next authenticated radio contact with the UE concerned, if the subscriber record "Location Information Confirmed in HSS" is marked as "Not Confirmed", the restoration procedure shall be triggered.

See also 3GPP TS 29.118 [46] clause 5.9.2.

5.2.4.1.3 Detailed behaviour of the HSS

The HSS shall make use of this procedure in order to indicate to all relevant MMEs, SGSN, and combined MME/SGSNs that the HSS has restarted and may have lost the current MME-Identity and SGSN-Identity of some of its subscribers who may be currently roaming in the MME area and/or SGSN area, and that the HSS, therefore, cannot send a Cancel Location messages or Insert Subscriber Data messages when needed.

The HSS may make use of this procedure in order to indicate to all relevant MMEs, SGSN, and combined MME/SGSNs that the HSS has updated subscription data shared by some of its subscribers who may be currently roaming in the MME area and/or SGSN area.

If the Reset-ID feature is not supported by the MME/SGSN and HSS, the HSS optionally may include a list of Ids identifying a subset of subscribers served by the HSS, if the occurred failure is limited to those subscribers.

If the Reset-ID feature is supported by the MME or SGSN, the HSS optionally may include one (or several) Reset-ID AVPs identifying e.g. failed hardware components if the occured failure is limited to those subscribers associated with e.g. the identified failed hardware components.

The HSS should invoke this procedure towards a combined MME/SGSN only for a single time even if some of the impacted subscribers are attached to the combined MME/SGSN via UTRAN/GERAN and some of the impacted subscribers are attached to the combined MME/SGSN via E-UTRAN.

5.2.5 Notification Procedures

5.2.5.1 Notification

5.2.5.1.1 General

The Notification Procedure shall be used between the MME and the HSS and between the SGSN and the HSS when an inter MME or SGSN location update does not occur but the HSS needs to be notified about

– an update of terminal information;

– an update of the UE SRVCC capability (only if the MME/SGSN supports SRVCC).

The Notification Procedure shall also be used between the MME and the HSS and between the SGSN and the HSS if the HSS needs to be notified about:

– an assignment/change of a dynamically allocated PDN GW for an APN, if such a notification is needed taking into account the access restrictions and the type of PDN;

NOTE: If the PDN is of type "non-IP", the APN is not accessible via non-3GPP access and therefore the PDN-GW ID does not need to be conveyed across accesses.

– an assignment/change of a dynamically allocated PDN GW for the establishment of emergency PDN connections, if such notification is needed for a non roaming authenticated user, based on operator policy (e.g. on whether the operator uses static PDN GW or not for emergency services) taking into account the access restrictions and feature support;

– the failed monitoring event configurations at the MME or SGSN (if received in ULA) or the status of the monitoring event configurations at the IWK-SCEF;

– the deletion of a monitoring event configuration in SCEF for a UE (i.e. due to an SCEF restart, see 3GPP TS 23.007 [43]).

The Notification Procedure shall be used between the MME and the HSS when an inter MME location update does not occur but the HSS needs to be notified about

– the need to send a Cancel Location to the current SGSN.

The Notification Procedure shall be used between the MME and the HSS when the "SMS in MME" feature is applied and between the SGSN and the HSS when an earlier short message delivery failed and the HSS needs to be notified about:

– the UE is reachable or the UE has memory capacity available to receive one or more short messages.

The Notification Procedure shall be used between the MME and the HSS and between the SGSN and the HSS when the HSS has requested to be notified about:

– the UE is reachable.

The Notification Procedure shall be used between the MME and the HSS and between the SGSN and the HSS to notify the HSS about:

– an update of the Homogeneous Support of IMS Voice Over PS Sessions.

The Notification Procedure shall be used between the MME and the HSS to notify the HSS about:

– removal of MME registration for SMS.

This procedure is mapped to the commands Notify-Request/Answer (NOR/NOA) in the Diameter application specified in clause 7.

Table 5.2.5.1.1/1 specifies the involved information elements for the request.

Table 5.2.5.1.1/2 specifies the involved information elements for the answer.

Table 5.2.5.1.1/1: Notify Request

Information element name	Mapping to Diameter AVP	Cat.	Description
IMSI	User-Name (See IETF RFC 6733 [61])	M	This information element shall contain the user IMSI, formatted according to 3GPP TS 23.003 [3], clause 2.2.
Supported Features (See 3GPP TS 29.229 [9])	Supported-Features	O	If present, this information element shall contain the list of features supported by the origin host.
Terminal Information (See 7.3.3)	Terminal-Information	C	This information element shall contain information about the user’s mobile equipment. When notifying the HSS about any change of Terminal Information, the MME or SGSN shall include the new Terminal Information in the request. Within this Information Element, only the IMEI and the Software-Version AVPs shall be used on the S6a/S6d interface.
PDN GW Identity (See 7.3.45)	MIP6-Agent-Info	C	This IE shall contain the identity of the selected and dynamically allocated PDN GW for an APN. It shall be present if a new PDN-GW has been selected and the subscriber is allowed handover to non 3GPP access or 5GS interworking without N26 interface enabled. When notifying the HSS about a newly selected PDN GW, the MME or SGSN shall include the PDN-GW-Identity in the request. For establishment of emergency PDN connections, this IE shall contain the identity of the PDN-GW used to establish those PDN connections.
PGW PLMN ID	Visited-Network-Identifier	C	This IE identifies the PLMN in which the PDN GW is located. It shall be present when the PDN GW Identity is present and does not contain an FQDN.
Context Identifier (See 7.3.27)	Context-Identifier	O	This parameter shall identify the APN Configuration with which the selected PDN GW shall be correlated. It may be present if it is available and the PDN-GW is present and is particular for one specific APN and not common to all the APNs. For the compatibility with the MAP protocol as defined in the 3GPP TS 29.002 [24], this parameter shall not have a value of zero.
APN (See TS 23.008 [30])	Service-Selection (See IETF RFC 5778 [20])	C	This IE shall contain the APN for the selected and dynamically allocated PDN GW. For establishment of non-emergency PDN connections, it shall be present if the selected PDN-GW is present and is particular for one specific APN and not common to all the APNs. For establishment of emergency PDN connections (i.e., the Emergency-Services AVP is present, with the Emergency-Indication flag set), this AVP shall be left absent.
Alert Reason (See 7.3.83)	Alert-Reason	C	This parameter shall indicate if the mobile subscriber is present or the MS has memory available. It shall be present when notifying the HSS about the presence of the UE or the UE has memory capacity available to receive one or more short messages.
UE SRVCC Capability	UE-SRVCC-Capability	C	This information element shall indicate if the UE supports or does not support the SRVCC capability. If the MME/SGSN supports SRVCC and the UE SRVCC Capability has changed, the MME or SGSN shall include the new UE SRVCC Capability in the request.
NOR Flags (See 7.3.49)	NOR-Flags	C	This Information Element shall contain a bit mask. See 7.3.49 for the meaning of the bits. Absence of this information element shall be interpreted as all bits set to 0. When notifying the HSS about the need to send cancel location to the current SGSN, the MME shall set the "Single-Registration-Indication" flag in the NOR-Flags. When notifying the HSS about the "restricted" status of the current SGSN area, the SGSN shall set the "SGSN area restricted" flag in the NOR-Flags. When notifying the HSS about the reachability of the UE or the UE has memory capacity available to receive one or more short messages, the MME, if the "SMS in MME" feature is applied, or SGSN shall set the "Ready for SM" flag correspondingly in the NOR-Flags. When notifying the HSS that the UE is reachable, the MME or SGSN shall set the "UE Reachable" flag correspondingly in the NOR-Flags. When notifying the HSS about update of the Homogeneous Support of IMS Voice Over PS Sessions, the MME or the SGSN shall set the "Homogeneous Support of IMS Voice Over PS Sessions" flag and S6a/S6d-Indicator flag for a combined MME/SGSN correspondingly in the NOR-Flags. When notifying the HSS about removal of MME registration for SMS, the MME shall set the "Removal of MME Registration for SMS" flag correspondingly in the NOR-Flags.
Homogeneous Support of IMS Voice Over PS Sessions (See 7.3.107)	Homogeneous-Support-of-IMS-Voice-Over-PS-Sessions	C	This Information Element shall be present if Homogeneous Support of IMS Voice Over PS Sessions is modified to one of the values "SUPPORTED" or "NOT_SUPPORTED". The value "SUPPORTED" indicates that there is support for "IMS Voice over PS Sessions" in all TAs or RAs. The value "NOT_SUPPORTED" indicates that there is not support for "IMS Voice over PS Sessions" in any of the TAs or RAs.
Maximum UE Availability Time	Maximum-UE-Availability-Time	O	This information element may be included when notifying the HSS that the UE is reachable. When present, it shall indicate the timestamp (in UTC) until which a UE using a power saving mechanism (such as extended idle mode DRX) is expected to be reachable for SM Delivery. This information may be used by the SMS Center to prioritize the retransmission of Short Message to UEs using a power saving mechanism.
Monitoring Event Config Status	Monitoring-Event-Config-Status	C	This information element shall be present if the MME/SGSN sends the Notify Request after receiving the Configuration-Information-Answer from the IWK-SCEF. This information element shall only contain the monitoring event configuration status of those events whose configuration status has changed since the last status informed to the HSS. This information element shall also be present if any of the monitoring events configurations received in ULA failed and shall only contain the monitoring event configuration status of those events whose detection could not be started at the MME/SGSN. This information element shall also be present if the MME or SGSN determines that a Monitoring Event Configuration for a UE is to be deleted in the HSS (i.e. SCEF responds to a Monitoring Event Report with DIAMETER_ERROR_SCEF_REFERENCE_ID_UNKNOWN).
Emergency Services (See 3GPP TS 29.273 [59])	Emergency-Services	C	The MME shall include this information element, and set the Emergency-Indication flag, to notify the HSS that a new PDN-GW has been selected for the establishment of an emergency PDN connection, whose identify is conveyed in the "PDN GW Identity" IE.

Table 5.2.5.1.1/2: Notify Answer

Information element name

Mapping to Diameter AVP

Cat.

Description

Result

(See 7.4)

Result-Code / Experimental-Result

This IE shall contain the result of the operation.

The Result-Code AVP shall be used to indicate success / errors as defined in the Diameter base protocol (see IETF RFC 6733 [61]).

The following errors are applicable in this case:

– User Unknown

Supported Features

(See 3GPP TS 29.229 [9])

Supported-Features

If present, this information element shall contain the list of features supported by the origin host.

5.2.5.1.2 Detailed behaviour of the MME and the SGSN

If the MME or SGSN supports Emergency services, the MME or SGSN shall not make use of the Notification procedure for emergency attached unauthenticated UEs; for authenticated UEs, the MME shall make use of the Notification procedure to inform the HSS about the PDN-GW selected to establish emergency PDN connections, if the MME is configured to use a dynamic PGW for emergency services for such UEs.

The MME or SGSN shall not make use of the Notification procedure to inform the HSS about the identity of the dynamically selected PDN-GW, if the access restrictions indicate that the user is not allowed to get service via non-3GPP access, or the PDN type of the APN is of type "non-IP".

The MME or SGSN shall include conditional AVPs in NOR according to the description given in table 5.2.5.1.1/1.

If the MME sends a Notify Request to inform the HSS that the UE has become reachable again, the MME shall clear the corresponding URRP-MME for the UE.

If the SGSN sends a Notify Request to inform the HSS that the UE has become reachable again, the SGSN shall clear the corresponding URRP-SGSN for the UE.

If the MME sends a Notify Request to inform the HSS about the presence of the UE to receive one or more short messages, the MME shall clear the corresponding MNRF for the UE.

If the SGSN sends a Notify Request to inform the HSS about the presence of the UE to receive one or more short messages, the SGSN shall clear the corresponding MNRG for the UE.

If the MME or SGSN determines that it needs to update the Homogeneous Support of IMS Voice Over PS Sessions in the HSS, the MME or SGSN shall send a Notify Request with the "Homogeneous Support of IMS Voice Over PS Sessions" bit set in the NOR-Flags AVP; if there is homogeneous support, or homogeneous non-support, of IMS Voice Over PS Sessions, the MME or SGSN shall report it by including the updated Homogeneous-Support-of-IMS-Voice-Over-PS-Sessions AVP; if the support is not homogeneous, the MME or SGSN shall report it by leaving such AVP absent in the Notify Request to the HSS. MME or SGSN shall ensure the status of Homogeneous Support of IMS Voice Sessions in HSS does not contradict with the value of "IMS voice over PS session indicator" provided to UE over NAS as specified in 3GPP TS 24.008 [31] and 3GPP TS 24.301 [64];
if "IMS voice over PS session indicator" sent to UE has changed from "not supported" to "supported" when status Homogenous Support of IMS Voice in HSS is "not supported", MME or SGSN shall immediately send Notify Request indicating as either homogenous support or not homogeneous;
if "IMS voice over PS session indicator" sent to UE has changed from "supported" to "not supported" when status Homogenous Support of IMS Voice in HSS is "supported", MME or SGSN shall immediately send Notify Request indicating as either homogenous non-support or not homogeneous.

If the MME needs to indicate to the HSS that it is no longer registered for SMS in the HSS, the MME shall send a Notify Request with "Removal of MME Registration for SMS" flag set in the NOR-Flags AVP.

When receiving a Notify response from the HSS, if the result code indicates DIAMETER_ERROR_UNKNOWN_SERVING_NODE, the MME or SGSN shall consider the Notification procedure as failed, and it shall mark the subscriber record as "Subscriber to be restored in HSS".

When receiving a Notify response from the HSS, if the result code indicates DIAMETER_ERROR_USER_UNKNOWN, the MME or SGSN shall detach the subscriber and remove the subscriber from its database.

If the MME/SGSN has received the monitoring event configurations in an ULA command and one, several or all event detections fail to be started (e.g due to maximum resources exceeded), the MME/SGSN shall send the Notify Request command with the Monitoring-Event-Config-Status AVP for the failed monitoring event configurations.

If the MME or SGSN receives a failure response, e.g. DIAMETER_UNABLE_TO_COMPLY, corresponding to a Notify Request to notify the HSS about the selected PDN-GW, the MME or SGSN shall not trigger a detach for the subscriber based only on this failure.

NOTE 1: A failure to indicate the selected PDN-GW to the HSS does not impact connectivity provided via 3GPP access.

When the MME/SGSN has received the Configuration-Information-Answer from the IWK-SCEF during the monitoring event configuration procedure, the MME/SGSN shall send the Notify Request command with the Monitoring-Event-Config-Status AVP as received from the IWK-SCEF in the Configuration-Information-Answer, for the monitoring event configurations whose status have changed (due to authorization performed by the IWK-SCEF) since last informed to the HSS.

NOTE 2: If the Monitoring-Event-Configuration was received at the MME/SGSN in the ULA command, then the HSS is not yet informed of any status of the monitoring event configuration. In this case, the entire Monitoring-Event-Config-Status as received from IWK-SCEF has to be transferred to the HSS through a Notify Request Command.

If the MME or SGSN determines that a Monitoring Event Configuration for a UE is to be deleted in the HSS (i.e. SCEF responds to a Monitoring Event Report with DIAMETER_ERROR_SCEF_REFERENCE_ID_UNKNOWN), the MME or SGSN shall send a Notify Request with the Monitoring-Event-Config-Status AVP. The Monitoring-Event-Config-Status AVP shall include the error as received from SCEF.

5.2.5.1.3 Detailed behaviour of the HSS

When receiving a Notify request the HSS shall check whether the IMSI is known.

If it is not known, a result code of DIAMETER_ERROR_USER_UNKNOWN shall be returned.

If the IMSI is known, and the source MME or SGSN originating the Notify message is not currently registered in HSS for that UE, a result code of DIAMETER_ ERROR_ UNKNOWN_SERVING_NODE shall be returned.

If the IMSI is known, and the source MME or SGSN is currently registered in HSS, the HSS shall set the result code to DIAMETER_SUCCESS, unless otherwise stated, and

– store the new terminal information if present in the request;

– store the new UE SRVCC capability if present in the request;

– store the new PDN GW and PLMN ID for an APN if present in the request and the APN is present in the subscription and if PDN GW is dynamically allocated; otherwise the HSS shall not store the new PDN GW data and shall set the result code to DIAMETER_ UNABLE_TO_COMPLY;

– store the new PDN GW and PLMN ID, and the APN itself, if both are present in the request, and the APN is not present in the subscription but a wild card APN is present in the subscription;

– if the Emergency Services IE is present, with the Emergency-Indication flag set, store the new PDN GW, as the PDN GW used to establish emergency PDN connections; the HSS shall store this information not bound to any specific APN;

– mark the location area as "restricted" if so indicated in the request;

– send Cancel Location to the current SGSN if so indicated in the request;

– if the UE has become reachable again, and NOR is received on S6a from an MME or on S6d from an SGSN, the HSS shall respectively clear the URRP-MME or the URPP-SGSN parameter for the UE and send an indication t of UE reachability from MME or SGSN o the Service Related Entities if there is any;

– when NOR is received on S6d from an SGSN (with the Alert Reason present), the HSS shall reset the MNRG flag and send a MAP-Alert-Service-Centre message or S6c-Alert-Service-Centre-Request (see 3GPP TS 29.338 [48], i.e. the behaviour in the HSS should be the same as when a MAP-Ready for SM is received from an SGSN;

– when NOR is received on S6a from an MME (with the Alert Reason present), the HSS shall reset the MNRF flag and send a MAP-Alert-Service-Centre message or S6c-Alert-Service-Centre-Request (see 3GPP TS 29.338 [48], i.e. the behaviour in the HSS should be the same as when a MAP-Ready for SM is received from a VLR/MSC;

– when NOR is received on S6a from an MME or on S6d from an SGSN to update the Homogeneous Support of IMS Voice Over PS Sessions, the HSS shall store the updated Homogeneous Support of IMS Voice Over PS Sessions and may use this information in the future in order to skip the T-ADS data retrieval, as described in clause 5.2.2.1 (IDR/IDA commands). If the "Homogeneous Support of IMS Voice Over PS Sessions" bit is set in the NOR-Flags AVP received but without Homogeneous-Support-of-IMS-Voice-Over-PS-Sessions AVP present in the NOR message, the HSS shall take the Homogeneous Support of IMS Voice Over PS Sessions as unknown to the serving node. If the "Homogeneous Support of IMS Voice Over PS Sessions" bit is not set in the NOR-Flags AVP, the HSS shall ignore (if present) the Homogeneous-Support-of-IMS-Voice-Over-PS-Sessions AVP;

– when NOR is received on S6a from an MME for removal of MME registration for SMS, the HSS shall remove the MME registration for SMS and the "MME number for SMS" as the corresponding MSC number to be used for MT SMS.

– when NOR is received on S6a from an MME or on S6d from an SGSN with the Monitoring-Event-Config-Status AVP, the HSS shall either trigger a Monitoring event cancelation procedure for the monitoring events that were not successfully authorized at the MME/SGSN by the IWK-SCEF or a Monitoring event suspension procedure for the monitoring events that were not successfully configured at the MME/SGSN, as specified in clause 7.2.2.2 of 3GPP TS 29.336 [54]. The HSS shall trigger a Monitoring event cancelation or suspension procedure based on the result code as indicated by MME/SGSN (e.g. DIAMETER_ERROR_UNAUTHORIZED_REQUESTING_ENTITY (5510) returned by IWK-SCEF triggers a Monitoring event cancelation procedure in HSS).

– when NOR is received on S6a from an MME or on S6d from an SGSN with an indication of the deletion of a monitoring event configuration in SCEF (DIAMETER_ERROR_SCEF_REFERENCE_ID_UNKNOWN in the Monitoring-Event-Config-Status AVP), the HSS shall locally delete the corresponding Monitoring Event Configuration and shall not trigger a Monitoring event cancelation procedure.

and then send the response to the MME or SGSN.