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Namf Service-Based Interface

5G Testing - Namf Nodes and Interfaces

The Access and Mobility Function (AMF) acts as the gatekeeper for the 5G Core (5GC) network, determining whether a particular UE may register with a network. With the Namf services it provides, the AMF also acts as the conduit through which 5GC Network Functions (NFs) communicate with a connected UE and obtain information about a UE’s capability, reachability, or location.

The dsTest Namf application supports the services briefly described below.

Namf_Communication

The Communication service focuses on information exchange with core NFs during a UE’s session, including during AMF mobility and 5G-4G mobility.

N1/N2 Messages

5G core NFs may communicate directly with the access network or the UE via the AMF’s N1/N2 interface. This service also enables NFs to subscribe to notifications for specific types of N1 messages received from a UE or N2 messages received from an access network.

  • Session Management Functions (SMFs) use this service during PDU session establishment, modification, and release to manage PDU session and QoS information in both the access network and the UE. SMFs also use this service to convey similar information during session continuity, service continuity, UP path management, and network-triggered service request procedures.
  • Short Message Service Functions (SMSFs) use this service to transmit the body of MT messages to the target UE and to forward SMS ack responses for MO messages to the originating UE.
  • Location Management Functions (LMFs) use this service to obtain location information for a UE directly from the UE or from the NG RAN. LMFs may subscribe for LPP messages from the UE or for NRPPa messages from the access network.
  • Policy Control Functions (PCFs) use this service to update access selection and PDU session selection policy information in the UE. PCFs may also subscribe for UPDP messages from the UE.

AMF Mobility

This service is also used by AMFs to communicate with each other during mobility events in order to transfer the UE’s context — including its security context — from the source AMF to the target AMF.

  • If mobility is realized during the registration process, the target AMF obtains the UE’s context by initiating the UEContextTransfer operation towards the source AMF. The target AMF, in turn, notifies the source AMF of the success or failure of said registration through the RegistrationStatusUpdate operation. Upon a successful registration the source AMF releases the UE context. It may also initiate the release of the AM Policy Association with the PCF in addition to releasing any PDU sessions that could not be maintained, as indicated by the content of the request message.
  • When the NG-RAN initiates an N2-based handover and the source AMF determines that it can no longer serve the UE, the source AMF selects a target AMF and initiates a CreateUEContext operation towards the target AMF to convey the existing context. If the handover is cancelled the source AMF notifies the target AMF through the ReleaseUEContext operation.

4G Interworking

Finally, during 5GS to Evolved Packet System (EPS) mobility an SMF may use this service to request that the serving AMF allocate EPS bearer IDs for some or all of a UE’s PDU sessions by invoking the EBIAssignment operation.

Namf_EventExposure

Event Exposure enables other NFs — NEFs, SMFs, and UDMs — to subscribe or unsubscribe for event notifications. They may subscribe for events regarding a specific UE, a group of UEs, or any UE. An AMF exposes the following events.

  • LOCATION_REPORT — delivers the last known location of a UE and notifies if its location changes
  • PRESENCE_IN_AOI_REPORT — delivers the current present state of a UE in an Area of Interest (AOI) and notifies if it enters or leaves an AOI
  • TIMEZONE_REPORT — delivers the UE’s current time zone and notifies if its time zone changes
  • ACCESS_TYPE_REPORT — delivers the UE’s current access type(s) and notifies if any access type changes
  • REGISTRATION_STATE_REPORT — delivers a UE’s current registration state and notifies if that state changes
  • CONNECTIVITY_STATE_REPORT — delivers a UE’s current connectivity state and notifies if that state changes
  • REACHABILITY_REPORT — delivers a UE’s current reachability and notifies if it changes
  • SUBSCRIBED_DATA_REPORT — delivers a UE’s subscribed data, as received from the Nudm_SDM service, and notifies if that data is updated
  • COMMUNICATION_FAILURE_REPORT — notifies of communications failures with a UE
  • UES_IN_AREA_REPORT — delivers the number of UEs in the specified area
  • SUBSCRIPTION_ID_CHANGE — notifies subscribers that the ID of an event subscription has changed (e.g., the serving AMF has changed)
  • SUBSCRIPTION_ID_ADDITION — notifies subscribers that a new group-level subscription ID is available (e.g., a new AMF is serving a UE that belongs to a group subscription)

Namf_MT

The MT service provides interested NFs information regarding a UE’s ability to receive the specified signalling.

  • The EnableUEReachability operation is invoked by an SMSF to determine whether the UE can receive an MT SMS. This operation will trigger the AMF to page the UE if the UE is in the CM-IDLE state.
  • The ProvideDomainSelectionInfo operation is invoked by a UDM to obtain information for terminating domain selection of IMS voice. Included in this information is UE support for IMS voice, the time stamp of the last radio contact with the UE, and its current access type and RAT type.

Namf_Location

An AMF’s Location service allows NFs to obtain information about a UE’s current location.

  • GMLCs use the ProvidePositioningInfo operation to obtain a UE’s current location on behalf of an external client. It receives updates through the EventNotify operation, in the case of emergency services sessions, if the UE’s location changes.
  • UDMs use the ProvideLocationInfo operation to request the Network Provided Location Information (NPLI) of a UE.

Implementation

Use our AMF emulator in your test network to provide Namf services to service consumers while also verifying their compliance with service specifications.

AMF Testing with dsTest

Test your Namf service producer by surrounding it with our node emulators:

  • Simulate millions of subscribers attempting to register over the N1/N2 interface with our gNodeB emulators.
  • Provide Nausf authentication services with our AUSF emulator.
  • Provide Nudm subscription data and UE context management services with our UDM emulator.
  • Install or delete authentication, access, and mobility policies in the AMF with our PCF emulator and its Npcf application.
  • Simulate PDU session establishment by initiating network-triggered service requests and conveying SM context information using the N1N2MessageTransfer operation with our SMF emulator.

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As with all dsTest products, the node configurations and test scenarios are easily defined and configured with XML files that are validated against a published XML Schema to avoid invalid definitions. With our dsClient Desktop application you can create, run, and archive tests; capture, graph and archive operational measurements; capture real-time data flows and subscriber events; and manage your dsTest platforms and testing scenarios with a standalone application that runs on your PC.

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Advanced Testing Features

SmartEvents — Alter application behavior or coordinate multiple interface applications with SmartEvents — our programmable, subscriber-level state machine. All dsTest applications are event-driven, enabling you to easily alter subscribers’ activities. Use our visual composer to draw your state machine and to trace a single subscriber’s path through the state machine while the test is running. Define event handlers that affect a subscriber’s behavior in an application, or that trigger an event in another application. You can also configure event handlers to modify subscriber information during run-time, introduce timers, or randomize subscriber behavior based on configurable probabilities to name just a few of the many options in one of dsTest’s most powerful features.

SmartMessageElement — Insert, delete, or replace elements in Diameter, RADIUS, MAP, LDAP, GTP, REST, or SOAP messages with our SmartMessageElement feature. Define proprietary signaling or corrupt elements to facilitate negative testing. You can specify when your elements are used with SmartEvents.

Traffic Profile — Draw the shape of your test actions across time with Traffic Profile. You can define the rate for any action as a static rate or reference a Traffic Profile configuration, which also means that multiple Traffic Profiles can be running concurrently. Use Traffic Profile in conjunction with the randomizing features in SmartEvents to design a test that more truly simulates real-world network activity.

REST Dictionary — Add conformance testing to your performance or functional test with our REST Dictionary. You can validate message types and JSON structures by simply including our base dictionary. You can also build custom dictionaries to explicitly define required parameter and property values and selectively include the dictionary to be used for a particular test.

Operational Measurements

dsTest provides rich sets of measurements for Namf services:

  • Transaction and transport layer attempts, successes, and failures
  • Transaction duration, transactions-per-second, and round-trip delay
  • Message and byte counters
  • Errors encountered and error indications received in messages

See our Online Help for Namf Communications Service measurements and socket measurements.

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Reference Standards