UDM Integration

Feature Summary and Revision History

Summary Data

Table 1. Summary Data

Applicable Product(s) or Functional Area

SMF

Applicable Product(s) or Functional Area

SMI

Feature Default Setting

Enabled – Always-on

Related Changes in this Release

Not Applicable

Related Documentation

Not Applicable

Revision History

Table 2. Revision History

Revision Details

Release

Added the N10 fail open support.

2023.04.0

First introduced.

2020.02.2

Feature Description

The Unified Data Management (UDM) is responsible for primarily storing the subscriber data, which SMF accesses for managing the user sessions on the network. The SMF explicitly subscribes to receive the notifications about the events that occur in the subscriber data such session terminate.

The N10 interface is between Unified Data Management (UDM) and SMF (Session Management Function). The UDM provides the following services to SMF via the Nudm interface:

  • Nudm_SubscriberDataManagement Service

  • Nudm_UEContextManagement Service

How it Works

This section describes how this feature works.

When the SMF skips UDM subscription, then it stops sending the following messages:

  • Fetch-Subscription during session establishment

  • Subscribe-for-Notification during session establishment

  • Unsubscribe-to-Notification during session release and when the UDCM receives the UECM messages

The SMF allows any dynamic changes to the UDM subscription skip configuration. That is, new value is applicable for the new session being established. The existing sessions continue to use the old values.

Configuring UDM

This section provides all the configurations related to UDM:

Configuring Options for Controlling SDM Messages

This section describes how to configure controlling Subscription Data Management (SDM) messages over the N10 interface.

Configuring RAT Type

To configure the RAT type with the local authorization under the DNN profile, use the following sample configuration:

config 
   profile dnn dnn_profile 
      authorization local rat-type [ nr | eutra | wlan ] 
      end

NOTES:

  • authorization local : This command skips the SDM messages for EPS sessions only. Upon configuring this command under the selected DNN profile, the SMF skips the UDM interaction for fetch subscription. The SMF uses the values received in the Create Session Request message. The SMF skips the UDM interaction to receive ‘Subscribe-for-Notifications’ from the UDM.

  • rat-type [ nr | eutra | wlan ] : This keyword skips the following SDM messages based on the specified RAT type.

    • udm subscription-fetch

    • subscribe-to-notifications

    • unsubscribe-to-notifications

    Upon configuring the RAT type with authorization local command in the selected DNN profile, then for sessions on that RAT-type, the SMF skips the UDM interaction for the following messages:

    • udm subscription-fetch during session establishment

    • subscribe-for-notifications during session establishment

    • unsubscribe-for-notifications during session release

  • no authorization local rat-type [ nr | eutra | wlan ] : Disables the local authorization under the DNN profile.

Configuration Verification

To verify the configuration, use the show running-config profile dnn dnn_profile_name command.

The output of this show command displays all the configurations including the RAT type information that is configured within the specified DNN profile. 

[smf] smf# show running-config profile dnn intershat
profile dnn intershat
network-element-profiles chf chf1
network-element-profiles amf amf1
network-element-profiles pcf pcf1
network-element-profiles udm udm1
charging-profile chgprf1
virtual-mac b6:6d:47:47:47:47
ssc-mode 2 allowed [ 3 ]
session type IPV6 allowed [ IPV6 ]
authorization local rat-type nr 
upf apn intershat
dcnr true
exit

Configuring Session Type

The SMF uses both subscription type data from UDM response and the session type configuration in DNN profile to allow or reject the call. The SMF selects the session type based on the initial look up of UE-requested PDN type in the UDM subscription data. Then, the SMF provisions session type for the session based on the selected session type and the session type configured in the DNN profile.

To configure the PDU session type in DNN profile, use the following sample configuration.

config 
   profile dnn dnnprofile 
      session type { IPV4 | IPV4V6 | IPV6 } allowed [ IPV4 | IPV4V6 | IPV6 ] 
      end

NOTES:

  • session type { IPV4 | IPV4V6 | IPV6 } allowed [ IPV4 | IPV4V6 | IPV6 ] : Specify the IP type for the PDU session. The allowed keyword allows you to specify two IP types other than the default session type.

  • The SMF uses this session type configuration to process the call. For example, if the UE requested type is IPv4 and the UDM subscription type is IPv4v6, the SMF selects IPv4 in the first pass and subsequently checks against the session type configuration. If the configured session type is IPv6, then the SMF rejects the call with a cause "#51 - PDU session type IPv6 only= IPV4 allowed".

  • If the IPAM configuration includes the IP address pool that is different from the finally selected PDU session type, the SMF rejects the call with a cause "#31 - request rejected, unspecified". For example, this cause value will be generated under the following conditions:

    • UeReq-PdnType = V4

    • UdmSubscription-PdnType = V4V6

    • SessionType-Config = V4V6

    • IP-Pool = V6

Configuration Verification

To verify the configuration, use the show running-config profile dnn dnn_profile_name command.

The output of this show command displays all the configurations including the session type information that is configured within the specified DNN profile. 

[smf] smf# show running-config profile dnn intershat
profile dnn intershat
network-element-profiles chf chf1
network-element-profiles amf amf1
network-element-profiles pcf pcf1
network-element-profiles udm udm1
charging-profile chgprf1
virtual-mac b6:6d:47:47:47:47
ssc-mode 2 allowed [ 3 ]
session type IPV6 allowed [ IPV6 ]
upf apn intershat
dcnr true
exit

Configuration to Disable Optional IEs

To disable optional IEs such as epdgInd and registrationTime attributes in the N10 Registration Request, use the following sample configuration: 


config 
   profile message-handling nf-type nf_ype 
      mh-profile mh_profile_name 
      service name type { nudm-ee | nudm-pp | nudm-sdm | nudm-ueau | nudm-uecm }  
      message type { UdmRegistrationReq | UdmSdmGetUESMSubscriptionData | UdmSdmSubscribeToNotification | UdmSdmUnsubscribeToNotification | UdmSubscriptionReq | UdmUecmRegisterSMF skip optional-ies [ epdgInd | registrationTime ] | UdmUecmUnregisterSMF } 
     exit 
  exit 
exit

NOTES:

  • mh-profile mh_profile_name : Specify the name of the message handling profile.

  • skip optional-ies [ epdgInd | registrationTime ] : Skips ePDG indication and registration time in the Registration Request.


    Note
    The skip optional-ies [ epdgInd | registrationTime ] command is available only with the UdmUecmRegisterSMF message.

Configuration-based Control of Subscription Notification with Immediate Report

Table 3. Feature History
Feature Name

Release Information

Description

Configuration-based Control of Subscription Notification with Immediate Report Indication on N10 Interface

 2024.03.0

With the "immediateReport" attribute enabled on UDM, the SMF ignores the UDM subscription fetch message and continues with the Subscription Notification Request, in which Subscription Management Data is received in the Subscription Notification Response.

With this controlled UDM notification subscription with the immediate report indication, the interactions between SMF and UDM over the N10 interface are minimized during the 4G, 5G, and Wi-Fi attach procedures and hence prevents message overload and failures.

This feature introduces the new CLI command subscription notify-immediate in the DNN profile.

Default Setting: Disabled – Configuration Required

Feature Description

When the "immediateReport" attribute is enabled on UDM in the Nudm_SDM_Subscribe service operation request, the SMF ignores the UDM subscription fetch message and continues with the subscription notification. The UDM sends the subscription data in the response to the SMF. The "immediateReport" attribute indicates whether an immediate report is required or not. By default, this attribute is disabled.

By enabling this feature, the interactions between SMF and UDM over the N10 interface are minimized during the 4G, 5G, and Wi-Fi attach procedures. The minimized interactions prevent message overload and failures. You can configure this feature through the subscription notify-immediate CLI command.


Note

The "immediateReport" attribute for UDM subscription is supported only for 3GPP TS 29.503 version 16.9.0, Release 16.

How it Works

When the subscription notification with immediate report feature is enabled, SMF performs the following tasks:

  • When the subscription notify-immediate CLI is configured, it’s assumed that all the UDMs support the immediate report feature.

  • SMF skips the N10 subscription fetch and continues with the N10 subscription notification. SMF includes the "immediateReport" attribute in the Subscribe to Notify request.

  • SMF triggers the subscription fetch procedure if the SMF doesn't receive the subscription data in the Subscribe to Notify response.

  • SMF triggers subscription notification with the "immediateReport" attribute to UDM through Service Communication Proxy (SCP). If the response includes the subscription data, the SMF doesn't perform the subscription fetch again. Else, the SMF triggers subscription fetch.


    Note

    If the subscription notification fails, SMF performs an action based on the failure handling configuration.

  • SMF enables the subscription local rat-type CLI functionality only when both subscription local rat-type and subscription notify-immediate CLI commands are configured for the same RAT type.

  • SMF ignores the authorization local CLI functionality when the subscription [ local | notify-immediate ] CLI is configured.

Configuring Subscription Notification with Immediate Report

To control the UDM Subscription Notification with Immediate Report messages, use the following sample configuration:

config 
   profile dnn dnn_profile 
      subscription [ local | notify-immediate ] rat-type [ nr | eutra | wlan ] 
      end

NOTES:

  • subscription notify-immediate : SMF skips the subscription fetch procedure and continues with Subscribe to Notify procedure with the ImmediateReport.

Verifying Subscription Notification with Immediate Report

This section describes how to verify the subscription notification when the "immediateReport" attribute is enabled.

Use the show running-config profile dnn command to verify subscription notification when the "immediateReport" attribute is enabled for various RAT types.

The following is an example output of the show running-config profile dnn command for the configured subscription local rat-type and subscription notify-immediate rat-type values. 

show running-config profile dnn dnnprof-ims.prod
 profile dnn dnnprof-ims.prod
   subscription local rat-type [ wlan ]
   subscription notify-immediate rat-type [ nr wlan ]
exit

OAM Support

This section describes operations, administration, and maintenance information for the subscription notification with immediate report feature.

Metrics

As part of this feature, the following label is added:

  • UDM_LABEL_IMMEDIATE_RPT: This label is added to the RecordUdmMsgProcessingStats udm_msg_processing_status metrics to determine the number of PDU sessions that have the "immediateReport" attribute enabled.

The following is an example of metrics when the immediate report feature is disabled.

udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="accepted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="",udm_msg="UdmRegistration"} 1
 
udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="accepted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="",udm_msg="UdmSmSubscription"} 1
 
udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="accepted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="10.105.35.112:8001",
udm_msg="UdmSubscribeToNotify"} 1
 
udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="attempted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="",udm_msg="UdmRegistration"} 1
 
udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="attempted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="",udm_msg="UdmSmSubscription"} 1
 
udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="attempted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="10.105.35.112:8001",
udm_msg="UdmDeregistration"} 1
 
udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="attempted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="10.105.35.112:8001",
udm_msg="UdmSubscribeToNotify"} 1

The following is an example of metrics when the immediate report feature is enabled.

udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="accepted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="",udm_msg="UdmRegistration"} 1

udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="true",instance_id="0",msg_status="accepted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="",udm_msg="UdmSmSubscription"} 1

udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="true",instance_id="0",msg_status="accepted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="10.105.35.112:8001",
udm_msg="UdmSubscribeToNotify"} 1

udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="attempted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="",udm_msg="UdmRegistration"} 1

udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="true",instance_id="0",msg_status="attempted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="",udm_msg="UdmSmSubscription"} 1

udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="false",instance_id="0",msg_status="attempted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="10.105.35.112:8001",
udm_msg="UdmDeregistration"} 1

udm_msg_processing_status{app_name="smf",cluster="Local",data_center="DC",
gr_instance_id="1",immediate_report="true",instance_id="0",msg_status="attempted",
rat_type="nr",service_name="smf-service",snssai="",udm_end_point="10.105.35.112:8001",
udm_msg="UdmSubscribeToNotify"} 1

N10 Fail Open on Converged Core

Table 4. Feature History
Feature Name

Release Information

Description

Minimizing SMF and UDM interactions on N10 interface through fail open support

 2023.04

With the fail open feature, the SMF supports the ignore and continue failure handling actions as well for the call during the N10 message failures. These failures include the UDM registration, Subscriber Fetch, and Subscribe to Notify for all RAT types.

Feature Description

This feature provides the following support:

  • Fail open—The SMF supports the ignore and continue failure handling actions as well for the call during the N10 message failures. These failures include the UDM registration, Subscriber Fetch, and Subscribe to Notify for all RAT types, which are LTE, NR and Wi-Fi.

    If the registration isn’t performed or failed during the session creation, then based on the configured failure handling action, the SMF performs the N10 registration during handover. The failure handling action can either be ignore or continue. If you haven’t configured the failure action to terminate the session, and the failure happens during handover, then SMF ignores the failure and continues with the handover procedure.

  • Interaction with SCP Model-D—If you have configured the SCP failure handling as continue or ignore, then the preceding failure handling is applicable. If you have configured the SCP failure handling as a fallback and a failure happens after the fallback, then the action that you configured under UDM failure handling is applicable.

Configuration-based Control of Subscription Messages

Feature Description

The Unified Data Management (UDM) is responsible for primarily storing the subscriber data, which SMF accesses for managing the user sessions on the network. The SMF explicitly subscribes to receive the notifications about the events that occur in the subscriber data such session terminate. When the SMF wants to stop receiving the notifications, it initiates the Unsubscribe-to-Notification messages to UDM. Upon receiving these messages, the UDM cancels the subscription by removing the notification subscription for the subscribed session.


Note

The SMF does not receive notification when the UDM-triggered subscription change is observed. However, for UDM-triggered session terminations, the SMF receives notifications from UDM.

How it Works

This section provides a overview of how the SMF and UDM communicate over the Unsubscribe-to-Notifications message:

  1. The NF, such as SMF, sends an Unsubscribe-to-Notifications request to the resource identified by the URI to the UDM. The SMF transacts the request to the UDM over the N10 interface. The Unsubscribe-to-Notifications request allows the SMF unsubscribe from notifications for a specific subscriber session. The SMF receives the URI details during the subscription creation process.

    The Unsubscribe-to-Notifications request contains the ‘SUPI’ and ‘subscriptionId’ in the URI.

  2. The UDM processes the request, and based on the response; it sends a response code to the SMF. For example, if the unsubscription is successful, then UDM sends 204 code. If the request is not processed, then the appropriate HTTP status code indicating the error is returned in the response body along with the additional error information.

  3. The SMF handles the timeout and failure that occurs when sending the Unsubscribe-to-Notifications messages to the UDM. In case the Unsubscribe-to-Notifications request fails, the SMF continues to purge the corresponding sessions.

    The Unsubscribe-to-Notification message is required for sessions that are hosted on the EUTRA network. Being on this network may not be a requirement for sessions that are released on the NR and WLAN network. For these access types, the SMF sends the UDM registration and deregistration messages that include subscription to notifications through implicit-unsubscribe during the deregistration.

Standards Compliance

The Support for the Unsubscribe-To-Notifications Messages feature complies with the following standards:

  • 3GPP TS 29.503 - 5G System; Unified Data Management Services

Call Flows

This section describes the call flow for the Unsubscribe-To-Notifications message support.

Unsubscribe-to-Notifications Call Flow

This section describes the call flow on how the SMF sends a request to the UDM to unsubscribe from notifications of data changes.

Figure 1. Unsubscribe-to-Notifications Communication with UDM
Table 5. Unsubscribe-to-Notifications Communication Call Flow Description

Step

Description

1

The NF service consumer, such as SMF, sends a request to the UDM to unsubscribe from notifications. By unsubscribing, the UDM no longer sends notifications to SMF when the data modifications occur in the respective subscriber session.

The NF service consumer sends a DELETE request to the resource identified by the URI. The NF service consumer receives the URI when the subscription gets created.

2a

If the deletion of request is successful, the UDM responds with "204 No Content".

2b

If the subscription is invalid, which can be due to an unknown subscriptionId value, then the HTTP status code "404 Not Found" is returned along with the additional error information in the response body (as part of the "ProblemDetails" element).

If the request is not processed, then the appropriate HTTP status code indicating the error is returned in the DELETE response body along with the additional error information.

OAM Support for the Unsubscribe-To-Notifications Messages

This section describes operations, administration, and maintenance information for this feature.

Statistics Support

The SMF maintains the following labels on the smf-rest-ep pod for monitoring the number of unsubscribe-to-notifications messages that are initiated towards UDM:

  • nfType – “udm”

  • messageDirection – “outbound”

  • apiName – “sdm_unsubscription_req”

  • nfUri – “nf_uri”

  • respStatus – “response_status”

  • rspCause – “response_cause”

Configuration-based Control of UDM Registration Messages

Table 6. Feature History
Feature Name

Release Information

Description

Configuration-based Control of UDM Registration Messages

 2024.01.2

SMF allows the user to ignore the UDM registration messages during the PDU setup and Wi-Fi attach procedures.

With this controlled UDM registrations, the interactions between SMF and UDM over the N10 interface are minimized to handle the message overload and attach failures on the N10 interface.

This feature introduces the new CLI command skip-n10-registration rat-type [ NR | WIFI | ALL ] in the DNN profile.

Default Setting: Disabled – Configuration Required

Feature Description

When the UE attach failures are caused by message overload on N10 interface, SMF ignores the UE registration messages from reaching the UDM. This feature optimizes the N10 interactions in the 5G and Wi-Fi network. You can configure this feature through the skip-n10-registration rat-type [ NR | WIFI | ALL ] CLI command.

How it Works

When you configure the skip-n10-registration rat-type [ NR | WIFI | ALL ] CLI command, SMF ignores the UDM registration during session creation in the 5G and Wi-Fi network. The handover between 5G and Wi-Fi fails because ePDG doesn't find the target SMF that was handling the session. If the UE registration fails during 5G or Wi-Fi attach and if the UDM failure handling template (FHT) is configured as continue or ignore, then SMF reattempts the registration during Wi-Fi-to 5G and 5G to Wi-Fi handovers.

Configuring Control for UDM Registration Messages

To control the UDM registration messages, use the following sample configuration:

config 
   profile dnn dnn_profile 
      skip-n10-registration rat-type [ NR | WIFI | ALL ] 
      exit

NOTES:

  • skip-n10-registration rat-type [ NR | WIFI | ALL ] : Specify the RAT type for which you want to ignore the UDM registration.