Framework and YANG Data Model for the NMA A2U Interface

Framework and YANG Data Model for the NMA A2U Interface China Academy of Information and Communication Technology

China zhaoxing@caict.ac.cn

China Mobile

Beijing China wangminxue@chinamobile.com

Cisco

dceccare@cisco.com

China Academy of Information and Communication Technology

China xuyunbin@caict.ac.cn

Operations and Management Network Management Operations NMA A2U YANG Network Management Agent This document describes a framework and a YANG data model for the Agent-to-User (A2U) interface of a Network Management Agent (NMA). The A2U interface is a user-facing interface through which a non-agent upper-layer system or user, such as an operator's OSS/BSS, orchestrator, management portal, human-facing application, automation system, etc., interacts with an NMA. The A2U interface supports NMA capability discovery, unified intent submission, task lifecycle management, execution plan exposure, human-in-the-loop confirmation, task progress notification, and consistent error reporting. The YANG data model defined in this document includes operational state data, RPC operations, and YANG notifications for the A2U interface. The model is intended to be used with YANG-based management protocols. This document does not define a separate transport protocol, a new HTTP resource API, or a separate notification delivery mechanism.

Introduction Telecommunication networks are becoming increasingly complex in scale, technology composition, service diversity, and operational requirements. Traditional manual operation and fixed API-based management are often insufficient to support highly automated and adaptive network operations. As defined in , a Network Management Agent (NMA) is an autonomous network management entity with intent management, network context awareness, analysis, decision-making, and execution capabilities. It can interpret user goals, plan management actions, invoke tools and interfaces, monitor execution, and report results. To allow non-agent upper-layer systems and users to consume NMA capabilities in a uniform way, this document defines the Agent-to-User (A2U) interface. The A2U interface supports:

NMA capability discovery;
natural-language or structured intent submission;
task lifecycle monitoring;
execution plan exposure;
human-in-the-loop confirmation;
task progress notification;
consistent error reporting.

A2U is intended for client/server-style interaction between a non-agent upper-layer system or user and an NMA. It is not intended for communication between an upper-layer NMA and a lower-layer NMA. NMA-to-NMA or Agent-to-Agent communication is outside the scope of A2U and is expected to use A2A or other Agent-to-Agent interfaces. The A2U YANG data model defines operational state data, RPC operations, and notifications for NMA-facing interaction. It does not define configuration datastore nodes for network resources and does not replace existing service, topology, alarm, incident, or performance management models. The model is intended to be used with YANG-based management protocols. This document does not define a separate transport protocol, a new HTTP resource API, or a separate notification delivery mechanism. Subscription and delivery of A2U notifications are expected to reuse existing YANG notification subscription mechanisms.

Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals. The following terms are defined in this document:

A2U Interface: The Agent-to-User interface through which a non-agent upper-layer system or user consumes NMA capabilities.
Network Management Agent (NMA): A network management entity defined in with autonomous task processing capabilities, which can interpret user goals, plan management actions, invoke tools and interfaces, monitor execution, and report results.
A2U Client: A non-agent upper-layer system or user-facing application that uses the A2U interface. Examples include an operator's OSS/BSS systems, orchestrators, management portals, automation systems, and human-facing applications. An upper-layer NMA is not an A2U Client in this document.
Intent: A goal description submitted to the NMA. It can be expressed using natural language or structured data.
Task: A management operation unit instantiated by the NMA for an accepted intent.
Plan: A sequence of steps generated by the NMA to execute a task.
Confirmation: A pending decision object generated when a task requires explicit approval, rejection, modification, or escalation.
A2U Notification: A YANG notification generated by the NMA to report A2U task progress or state changes.
A2A Interface: An Agent-to-Agent interface used for interaction between agents or NMAs. A2A is outside the scope of this document.

Scope This document defines the A2U interface positioning, reference framework, information model, and a YANG data model for A2U operational state data, RPC operations, and notifications. It also provides non-normative JSON examples illustrating A2U payloads and reuse of existing IETF domain models. This document does not define a new transport protocol, a new HTTP resource API, a new notification delivery mechanism, Agent-to-Agent communication, domain-specific service models, LLM implementation details, or internal NMA implementation mechanisms.

A2U Interface Positioning A2U is used when a non-agent upper-layer system or user invokes NMA capabilities. It is a client/server-style interface between an A2U client and an NMA acting as the A2U server. A2U is not used for communication between an upper-layer NMA and a lower-layer NMA. Such communication is outside the scope of this document and is expected to use A2A or other Agent-to-Agent interfaces. This document focuses only on the logical A2U interaction between a non-agent A2U client and an NMA acting as the A2U server.

A2U Reference Framework The figure below illustrates the logical A2U relationship between a non-agent upper-layer system or user and an NMA. It is intended to show the A2U client/server interaction model only. The deployment relationship between the NMA, controllers, and network resources is outside the scope of this figure.

Framework of A2U interface The A2U function provides capability discovery, intent submission, task state access, confirmation access and resolution, notification subscription, and result reporting. The A2U data model defined in this document focuses on the information exchanged between the A2U client and the A2U server.

A2U Design Principles

YANG-Based Management Protocol Reuse The A2U model is defined as a YANG module containing operational state data, RPC operations, and notifications. It is intended to be carried by existing YANG-based management protocols rather than by a dedicated new protocol. Protocol-specific details such as transport, URI layout, message framing, subscription establishment, and notification delivery are outside the scope of this document.

Unified Intent Entry Natural-language and structured input share the same intent submission entry and the same task lifecycle. The mode field distinguishes the input type.

Unified Task Lifecycle After an intent is accepted, the NMA creates or associates a task. The task lifecycle includes:

Lifecycle of a task PENDING -> ANALYZING -> PLANNING -> AWAITING_CONFIRMATION -> EXECUTING -> COMPLETED / FAILED / ABORTED Clarification may be requested when input is incomplete or ambiguous.

Human-in-the-Loop Confirmation When a task violates a policy, affects critical resources, or requires human review, the NMA creates a confirmation object and suspends execution until the confirmation is resolved.

YANG Notification Reuse A2U task progress and state changes are reported using YANG notifications. This document defines the notification content in the A2U YANG module. Subscription, filtering, and delivery of A2U notifications are expected to use existing mechanisms such as Subscription to YANG Notifications . Where an implementation supports subscription to operational datastore updates, YANG-Push can also be used to observe changes to A2U operational state data such as task and confirmation state.

A2U Information Model The A2U information model contains five core components.

Agent Capabilities The agent-capabilities object describes the NMA and its exposed skills, including supported input schemas, confirmation requirements, and global policies.

Intent The intent object represents a user or system goal. Natural-language input includes the original user text. Structured input includes the operation type, target resource, constraints, and priority. The intent-type identifies the high-level operation category. It is not intended to encode all domain-specific subtypes. Domain-specific details, such as service assurance objectives, fault symptoms, recovery constraints, or optimization policies, are carried in the constraints field. The constraints field of a structured intent is modeled as anydata, allowing it to carry domain-specific information objects defined by other IETF YANG modules. For example, in fault handling and service assurance scenarios, the constraints MAY include incident information as defined in , such as incident-id, incident-no, priority, category, sources, probable-causes, probable-events, and events, to provide the NMA with structured incident context for analysis and remediation.

Task The task object represents the lifecycle of an accepted intent. It exposes task state, execution plan information, and task results.

Confirmation The confirmation object represents a pending or resolved decision point. It provides the context, allowed actions, status, and resolution information needed for human-in-the-loop or system-in-the-loop decision making.

Notification A2U notifications report task progress and state changes. The notification payload is modeled as a YANG choice so that different notification types can carry different payload structures.

YANG Data Model

Model Design The model defined in this document (ietf-nma-a2u) contains operational state data, RPC operations, and a YANG notification for the A2U interface. The operational state data expose NMA capabilities, submitted intents, tasks, and pending or resolved confirmations. RPC operations are used for intent submission, confirmation resolution, and task abort. The notification reports task progress and state changes. Domain-specific information can be carried using anydata fields with an associated schema identifier. For example, incident-related information can be aligned with without redefining the incident model in this document.

YANG Tree The following tree provides a non-normative overview of the defined YANG model.

YANG Module module ietf-nma-a2u { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-nma-a2u"; prefix nmaa2u; import ietf-yang-types { prefix yang; reference "RFC 6991: Common YANG Data Types"; } import ietf-inet-types { prefix inet; reference "RFC 6991: Common YANG Data Types"; } organization "IETF NMOP Working Group"; contact "WG Web: <https://datatracker.ietf.org/wg/nmop/> WG List: <mailto:nmop@ietf.org> Editor: Xing Zhao <mailto:zhaoxing@caict.ac.cn>"; description "This module defines operational state data, RPC operations, and notifications for the Agent-to-User (A2U) interface of a Network Management Agent (NMA). The module is used between a non-agent A2U client and an NMA."; revision 2026-06-30 { description "Initial revision."; reference "RFC XXXX: Framework and YANG Data Model for the NMA A2U Interface."; } typedef intent-mode { type enumeration { enum natural-language { description "Intent expressed using natural language."; } enum structured { description "Intent expressed using structured data."; } } description "Intent input mode."; } typedef intent-type { type enumeration { enum CREATE { description "Create a service, resource, policy, or other managed object."; } enum DELETE { description "Delete a service, resource, policy, or other managed object."; } enum MODIFY { description "Modify an existing service, resource, policy, or other managed object."; } enum QUERY { description "Query status, state, inventory, performance, or other management information."; } enum REPORT { description "Generate a report based on network, service, or operational data."; } enum DIAGNOSE { description "Analyze symptoms, alarms, performance data, or events to identify possible root causes."; } enum REMEDIATE { description "Perform corrective or recovery actions for a detected fault, degradation, or abnormal condition."; } enum OPTIMIZE { description "Optimize service or network behavior according to performance, efficiency, cost, energy, capacity, or policy objectives."; } enum ASSURE { description "Assure a service, slice, resource, or policy objective by monitoring its state and taking or recommending actions when needed."; } } description "High-level structured intent operation category. Domain-specific subtypes and constraints are carried in the constraints payload."; } typedef task-state { type enumeration { enum PENDING { description "Task has been created and is awaiting processing."; } enum ANALYZING { description "The NMA is analyzing the intent."; } enum AWAITING_CLARIFICATION { description "Additional information is required."; } enum PLANNING { description "The NMA is generating an execution plan."; } enum AWAITING_CONFIRMATION { description "The task is suspended until confirmation is resolved."; } enum EXECUTING { description "The NMA is executing the task."; } enum COMPLETED { description "The task has completed successfully."; } enum FAILED { description "The task has failed."; } enum ABORTED { description "The task has been aborted."; } } description "Task lifecycle state."; } typedef confirmation-type { type enumeration { enum EXECUTION { description "Confirmation before executing an action."; } enum PARAMETER_CHANGE { description "Confirmation of parameter changes."; } enum DESTRUCTIVE_OPERATION { description "Confirmation of a destructive or service-affecting operation."; } enum POLICY_VIOLATION { description "Confirmation of an action that violates or exceeds a policy."; } } description "Confirmation type."; } typedef a2u-notification-type { type enumeration { enum plan-generated { description "An execution plan has been generated."; } enum confirmation-required { description "Confirmation is required."; } enum step-completed { description "A plan step has completed."; } enum step-failed { description "A plan step has failed."; } enum task-completed { description "The task has completed."; } enum task-failed { description "The task has failed."; } } description "Type of A2U task notification."; } typedef step-state { type enumeration { enum pending { description "Step is pending."; } enum running { description "Step is running."; } enum completed { description "Step has completed."; } enum failed { description "Step has failed."; } enum skipped { description "Step has been skipped."; } } description "Plan step state."; } typedef confirmation-action { type enumeration { enum approve { description "Approve the proposed action."; } enum reject { description "Reject the proposed action."; } enum modify-and-approve { description "Modify parameters and approve the action."; } enum escalate-to-human { description "Escalate the decision to a human operator."; } } description "Confirmation resolution action."; } typedef confirmation-status { type enumeration { enum pending { description "Confirmation is waiting for resolution."; } enum approved { description "Confirmation has been approved."; } enum rejected { description "Confirmation has been rejected."; } enum modified { description "Confirmation has been modified and approved."; } enum expired { description "Confirmation has expired."; } enum escalated { description "Confirmation has been escalated."; } } description "Confirmation status."; } typedef error-type { type enumeration { enum invalid-request { description "The request is invalid."; } enum unauthorized { description "Authentication is required or has failed."; } enum forbidden { description "The requester is not authorized."; } enum not-found { description "The requested object was not found."; } enum conflict { description "The request conflicts with the current state."; } enum unprocessable-content { description "The request cannot be processed semantically."; } enum internal-error { description "An internal error occurred."; } } description "A2U error type."; } grouping submitter-info { description "Information about the user or non-agent upper-layer system that submitted the request."; leaf type { type enumeration { enum user { description "Human user."; } enum system { description "Non-agent upper-layer system."; } } description "Submitter type. The system value represents a non-agent upper-layer system."; } leaf id { type string; description "Submitter identifier."; } } grouping message-metadata { description "Common metadata used for request correlation and tenancy context."; leaf request-id { type string; description "Identifier of the request."; } leaf correlation-id { type string; description "Identifier used to correlate related A2U interactions."; } leaf tenant-id { type string; description "Identifier of the tenant, customer, organization, project, administrative domain, or other management context associated with the request."; } } grouping error-info { description "Common error information returned by the A2U interface."; leaf error-type { type error-type; description "Error type."; } leaf error-code { type string; description "Machine-readable error code."; } leaf error-message { type string; description "Human-readable error message."; } leaf retryable { type boolean; default "false"; description "Whether retry may succeed."; } leaf target { type string; description "Target object or field related to the error."; } anydata details { description "Additional error details."; } } grouping agent-capabilities-object { description "Capability discovery information exposed by the NMA."; leaf agent-id { type string; mandatory true; description "NMA identifier."; } leaf version { type string; mandatory true; description "NMA version."; } list skills { key "skill-id"; description "Skills exposed by the NMA."; leaf skill-id { type string; description "Skill identifier."; } leaf name { type string; mandatory true; description "Human-readable skill name."; } leaf description { type string; description "Skill description."; } leaf input-schema { type union { type inet:uri; type string; } description "Input schema URI or inline schema description."; } leaf confirmation-required { type boolean; default "false"; description "Whether this skill normally requires confirmation before execution."; } leaf-list tags { type string; description "Optional tags used to classify or discover this skill."; } } container policies { description "Global policies advertised by the NMA."; leaf human-in-the-loop { type boolean; default "true"; description "Whether human-in-the-loop is enabled by default."; } leaf max-timeout-seconds { type uint32; units "seconds"; description "Maximum timeout in seconds."; } } } grouping intent-object { description "Intent submitted to the NMA."; leaf intent-id { type string; description "Intent identifier."; } leaf mode { type intent-mode; mandatory true; description "Intent input mode."; } container submitter { description "Submitter information."; uses submitter-info; } leaf timestamp { type yang:date-and-time; description "Submission timestamp."; } leaf state { type task-state; description "Current processing state associated with this intent."; } leaf task-id { type string; description "Associated task identifier."; } choice mode-choice { description "Mode-specific intent content."; case natural-language { container natural-language { description "Natural-language input."; leaf text { type string; mandatory true; description "Natural-language text submitted by the user or system."; } } } case structured { container structured { description "Structured input."; leaf type { type intent-type; mandatory true; description "High-level operation category."; } leaf target-resource { type string; description "Target service, resource, slice, domain, or object."; } leaf constraints-schema { type inet:uri; description "Schema used to interpret constraints."; } anydata constraints { mandatory true; description "Domain-specific constraints. This field MAY carry information objects defined by other IETF YANG modules. For example, in fault handling scenarios, incident information as defined in the ietf-incident module MAY be included."; } leaf priority { type uint8 { range "1..10"; } default "5"; description "Intent priority."; } } } } leaf estimated-completion { type uint32; units "seconds"; description "Estimated completion time."; } } grouping plan-step { description "A step in a task execution plan."; leaf step-id { type string; description "Step identifier."; } leaf action { type string; mandatory true; description "Action to be performed."; } leaf target { type string; description "Target of the action."; } anydata input-params { description "Step input parameters."; } leaf status { type step-state; mandatory true; description "Step status."; } leaf observation { type string; description "Observation or result generated by this step."; } leaf started-at { type yang:date-and-time; description "Step start time."; } leaf completed-at { type yang:date-and-time; description "Step completion time."; } } grouping task-object { description "Task lifecycle information."; leaf task-id { type string; description "Task identifier."; } leaf parent-intent-id { type string; mandatory true; description "Identifier of the parent intent."; } leaf state { type task-state; mandatory true; description "Current task state."; } leaf created-at { type yang:date-and-time; mandatory true; description "Task creation time."; } leaf updated-at { type yang:date-and-time; mandatory true; description "Last task update time."; } list plan { key "step-id"; description "Execution plan."; uses plan-step; } container result { description "Task result or intermediate output."; leaf summary { type string; description "Result summary."; } leaf-list affected-resources { type string; description "Resources affected by the task."; } anydata output-data { description "Structured output data."; } } } grouping confirmation-object { description "Confirmation information used for human-in-the-loop or system-in-the-loop decision making."; leaf confirmation-id { type string; description "Confirmation identifier."; } leaf task-id { type string; mandatory true; description "Associated task identifier."; } leaf type { type confirmation-type; mandatory true; description "Confirmation type."; } leaf priority { type uint8 { range "1..10"; } default "5"; description "Confirmation priority."; } leaf timeout-seconds { type uint32; default "300"; units "seconds"; description "Timeout for resolving the confirmation."; } leaf context-schema { type inet:uri; description "Schema used to interpret context."; } anydata context { mandatory true; description "Context needed to resolve the confirmation."; } leaf-list allowed-actions { type confirmation-action; min-elements 1; description "Actions allowed for this confirmation."; } leaf status { type confirmation-status; default "pending"; description "Confirmation status."; } container resolution { description "Final resolution of the confirmation."; leaf action { type confirmation-action; description "Selected resolution action."; } leaf modified-params-schema { type inet:uri; description "Schema used to interpret modified-params."; } anydata modified-params { description "Modified parameters."; } leaf resolved-by { type string; description "Resolver identifier."; } leaf resolved-at { type yang:date-and-time; description "Resolution time."; } } } container a2u { config false; description "Operational state data for the A2U interface."; container agent-capabilities { description "NMA capabilities exposed through A2U."; uses agent-capabilities-object; } list intent { key "intent-id"; description "Intents submitted through A2U and retained as operational state for tracking."; uses intent-object; } list task { key "task-id"; description "Tasks created or associated with accepted intents."; uses task-object; } list confirmation { key "confirmation-id"; description "Confirmation objects generated by the NMA."; uses confirmation-object; } } rpc submit-intent { description "Submit an intent to the NMA."; input { uses message-metadata; container intent { description "Submitted intent."; uses intent-object; } } output { uses message-metadata; leaf accepted { type boolean; mandatory true; description "Whether the intent was accepted."; } leaf intent-id { type string; description "Accepted intent identifier."; } leaf task-id { type string; description "Created or associated task identifier."; } leaf state { type task-state; description "Current task state."; } container task { description "Task information when available."; uses task-object; } container error { description "Error information."; uses error-info; } } } rpc resolve-confirmation { description "Resolve a pending confirmation."; input { uses message-metadata; leaf confirmation-id { type string; mandatory true; description "Confirmation identifier."; } leaf action { type confirmation-action; mandatory true; description "Selected resolution action."; } leaf modified-params-schema { type inet:uri; description "Schema used to interpret modified-params."; } anydata modified-params { description "Modified parameters."; } leaf resolved-by { type string; description "Resolver identifier."; } } output { leaf confirmation-id { type string; description "Confirmation identifier."; } leaf task-id { type string; description "Associated task identifier."; } leaf status { type confirmation-status; description "Updated confirmation status."; } leaf task-state { type task-state; description "Updated task state."; } container error { description "Error information."; uses error-info; } } } rpc abort-task { description "Abort an A2U task."; input { uses message-metadata; leaf task-id { type string; mandatory true; description "Task identifier."; } leaf reason { type string; description "Reason for aborting the task."; } } output { leaf task-id { type string; description "Task identifier."; } leaf state { type task-state; description "Updated task state."; } container error { description "Error information."; uses error-info; } } } notification a2u-task-notification { description "Notification generated when an A2U task changes state or produces progress information."; leaf task-id { type string; mandatory true; description "Associated task identifier."; } leaf intent-id { type string; description "Associated intent identifier."; } leaf notification-type { type a2u-notification-type; mandatory true; description "A2U notification type."; } leaf time { type yang:date-and-time; description "Time when the notification was generated."; } container payload { description "Notification-type-specific payload."; choice notification-payload { description "Payload selected according to notification type."; case plan-generated { container plan-generated { leaf step-count { type uint32; mandatory true; description "Number of generated plan steps."; } leaf estimated-duration { type uint32; units "seconds"; description "Estimated execution duration."; } } } case confirmation-required { container confirmation-required { description "Payload carried when a task requires confirmation. The payload provides a summary of the confirmation so that the client can present the decision request without necessarily retrieving the full confirmation object."; leaf confirmation-id { type string; mandatory true; description "Identifier of the confirmation object created by the NMA. The full confirmation object can be read from A2U operational state data using this identifier."; } leaf confirmation-type { type confirmation-type; description "Type of confirmation required."; } leaf priority { type uint8 { range "1..10"; } description "Priority of the confirmation."; } leaf timeout-seconds { type uint32; units "seconds"; description "Timeout for resolving the confirmation."; } leaf context-schema { type inet:uri; description "Schema used to interpret the confirmation context."; } leaf summary { type string; description "Human-readable summary of the confirmation request."; } leaf-list allowed-actions { type confirmation-action; description "Actions allowed for this confirmation."; } } } case step-completed { container step-completed { leaf step-id { type string; mandatory true; description "Completed step identifier."; } leaf observation { type string; description "Step observation."; } } } case step-failed { container step-failed { leaf step-id { type string; mandatory true; description "Failed step identifier."; } leaf exception-type { type string; mandatory true; description "Exception type."; } leaf affected-scope { type string; description "Affected scope."; } leaf-list remedial-suggestions { type string; description "Suggested remedial actions."; } } } case task-completed { container task-completed { leaf summary { type string; mandatory true; description "Task completion summary."; } leaf-list affected-resources { type string; description "Affected resources."; } } } case task-failed { container task-failed { leaf reason { type string; mandatory true; description "Task failure reason."; } leaf failed-step-id { type string; description "Failed step identifier."; } } } } } } }

Security Considerations The A2U YANG module can expose sensitive operational information, including intents, tasks, plans, affected resources, confirmation context, notifications, and results. The YANG module specified in this document is designed to be accessed via YANG-based management protocols, such as NETCONF and RESTCONF . Implementations are expected to provide secure transport, mutual authentication, authorization, confidentiality protection, integrity protection, replay protection, audit logging, and policy enforcement. RPC operations such as submit-intent, resolve-confirmation, and abort-task can affect network operations indirectly through the NMA. Access to these RPC operations needs to be restricted to authorized clients. Natural-language inputs and AI-assisted interpretation may introduce risks such as ambiguous instructions, malicious input, prompt injection, or incorrect interpretation. Implementations should validate interpreted results before execution and should use confirmation or policy checks for risky operations. Confirmation resolution operations can affect network behavior and therefore require authorization and audit logging. A2U notifications may contain sensitive operational information. Implementations should ensure that notification subscribers are authorized to receive the corresponding notifications. Future versions of this document are expected to expand this section.

IANA Considerations This version of the document does not request any IANA actions. Future versions may request registration of the YANG module namespace and module name if the YANG module becomes normative. Expected future namespace: urn:ietf:params:xml:ns:yang:ietf-nma-a2u Expected future module name: ietf-nma-a2u

References Normative References Key words for use in RFCs to Indicate Requirement Levels Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words Common YANG Data Types The YANG 1.1 Data Modeling Language Informative References Subscription to YANG Notifications AI based Network Management Agent (NMA): Concepts and Architecture Network Configuration Protocol (NETCONF) RESTCONF Protocol Subscription to YANG Notifications for Datastore Updates A YANG Data Model for Network Incident Management Work in Progress

Example A2U Interaction Using YANG-Based Management Protocols This appendix provides a non-normative example of an A2U interaction flow in a network incident diagnosis scenario. RESTCONF-style resource paths are used only to illustrate how A2U operational state data, RPC operations, and YANG notifications can be accessed by an A2U client. A typical A2U interaction can proceed as follows:

The A2U client first discovers the NMA capabilities.
The A2U client invokes the submit-intent RPC with either natural-language input or structured input.
The NMA creates or updates intent and task operational state.
The A2U client observes task state by subscribing to A2U task notifications.
When confirmation is required, the NMA creates a confirmation object and sends a confirmation-required notification.
The A2U client invokes the resolve-confirmation RPC to approve, reject, modify, or escalate the proposed action.
The NMA continues execution and sends task progress or completion notifications.

Example A2U Interaction Flow Using a YANG-Based Management Protocol | | | | 2. Return NMA capabilities | |<-------------------------------------------------------------| | | | 3. POST /restconf/operations/ietf-nma-a2u:submit-intent | | Input: incident diagnosis intent with | | ietf-incident aligned constraints | |------------------------------------------------------------->| | | | 4. Return accepted result: intent-id, task-id, state | |<-------------------------------------------------------------| | | | 5. Establish subscription for a2u-task-notification | |------------------------------------------------------------->| | | | 6. Subscription established | |<-------------------------------------------------------------| | | | 7. Notification: plan-generated | |<-------------------------------------------------------------| | | | 8. Notification: confirmation-required | | Carries confirmation-id and compact summary | |<-------------------------------------------------------------| | | | 9. Optional: GET /restconf/data/ietf-nma-a2u:a2u/ | | confirmation=confirmation-id | |------------------------------------------------------------->| | | |10. Return confirmation object: context, actions, status | |<-------------------------------------------------------------| | | |11.POST /restconf/operations/ietf-nma-a2u:resolve-confirmation| | Input: confirmation-id, action, resolved-by, | | optional modified-params | |------------------------------------------------------------->| | | |12. Return confirmation result and updated task-state | |<-------------------------------------------------------------| | | |13. Notification: step-completed | |<-------------------------------------------------------------| | | |14. Notification: task-completed | |<-------------------------------------------------------------| | | |15.Optional: GET /restconf/data/ietf-nma-a2u:a2u/task=task-id | |------------------------------------------------------------->| | | |16. Return final task state and result | |<-------------------------------------------------------------| | | +-------+------+ +-------+----+ | A2U Client | | A2U Server | | (User) | | (NMA) | +--------------+ +------------+ ]]>

JSON Examples This appendix provides non-normative JSON examples for an OTN network incident diagnosis and resolution scenario. The examples demonstrate how the A2U interface can carry incident-related information aligned with the ietf-incident module defined in . In this example, the A2U model does not redefine the incident model. Instead, the A2U envelope carries the user-facing interaction semantics, such as intent submission, task lifecycle, confirmation, and notification, while the constraints and confirmation context reuse incident fields such as incident-no, service-instance, domain, priority, status, sources, probable-causes, probable-events, and events. In this example, a vendor's OSS detects degradation of an OTN service and invokes the NMA through A2U by submitting an incident diagnosis intent. The structured intent carries incident information aligned with . After accepting the intent, the NMA perceives the incident, analyzes the probable root cause, generates an incident resolution plan, and creates a confirmation object before executing a service-affecting recovery action. Task progress and state changes are reported using A2U YANG notifications. Examples of A2U interface message contents are provided below in sequence from intent initiation, task planning, confirmation, execution to feedback.

Agent Capabilities { "agent-id": "nma-transport-1", "version": "0.1.0", "skills": [ { "skill-id": "otn-incident-handling", "name": "OTN incident handling", "description": "Analyze OTN alarms, performance degradation, and service impact, and propose or execute recovery actions.", "input-schema": "urn:ietf:params:xml:ns:yang:ietf-incident", "confirmation-required": true, "tags": [ "transport", "otn", "incident", "remediation" ] } ], "policies": { "human-in-the-loop": true, "max-timeout-seconds": 1800 } }

Intent Submission RPC The following examples show the input and output of the submit-intent RPC. The RPC can carry either a natural-language intent or a structured intent. Both input modes use the same submit-intent RPC and follow the same task lifecycle after the intent is accepted. Input example using a natural-language intent: { "request-id": "req-1001", "correlation-id": "corr-20260630-001", "tenant-id": "tenant-1", "intent": { "intent-id": "intent-1001", "mode": "natural-language", "submitter": { "type": "system", "id": "oss-a" }, "timestamp": "2026-06-30T10:00:00Z", "natural-language": { "text": "Analyze the service degradation of OTN service svc-1001, identify the root cause, assess affected resources, and recommend recovery actions." } } } Input example using a structured intent: { "request-id": "req-1002", "correlation-id": "corr-20260630-002", "tenant-id": "tenant-1", "intent": { "intent-id": "intent-1002", "mode": "structured", "submitter": { "type": "system", "id": "orchestrator-a" }, "timestamp": "2026-06-30T10:05:00Z", "structured": { "type": "DIAGNOSE", "target-resource": "incident-56433218", "constraints-schema": "urn:ietf:params:xml:ns:yang:ietf-incident", "constraints": { "incident-no": 56433218, "name": "otn-service-degradation", "type": "problem", "incident-id": "line-fault-svc-1001", "service-instance": [ "svc-1001" ], "domain": "otn", "priority": "critical", "status": "raised", "ack-status": "unacknowledged", "category": "network", "detail": "OTN service svc-1001 is degraded. OTU_LOF and ODU_AIS alarm events were observed on the working path.", "resolve-advice": "Diagnose the probable root cause and provide recovery suggestions. Prefer actions that minimize impact on running services.", "occur-time": "2026-06-30T09:59:30Z", "raise-time": "2026-06-30T10:00:00Z", "last-updated": "2026-06-30T10:05:00Z" }, "priority": 9 } } } Output example after the intent is accepted: { "request-id": "req-1002", "correlation-id": "corr-20260630-002", "tenant-id": "tenant-1", "accepted": true, "intent-id": "intent-1002", "task-id": "task-2001", "state": "PENDING" }

Task Object { "task-id": "task-2001", "parent-intent-id": "intent-1002", "state": "AWAITING_CONFIRMATION", "created-at": "2026-06-30T10:00:00Z", "updated-at": "2026-06-30T10:03:30Z", "plan": [ { "step-id": "step-1", "action": "perceive-network-incident", "target": "incident-56433218", "status": "completed", "observation": "The NMA perceived the OTN service degradation incident and loaded the incident context." }, { "step-id": "step-2", "action": "analyze-network-incident", "target": "incident-56433218", "status": "completed", "observation": "The NMA analyzed the incident and identified probable cause information based on alarms and topology correlation." }, { "step-id": "step-3", "action": "generate-incident-resolution-plan", "target": "incident-56433218", "status": "completed", "observation": "The NMA generated a resolution plan according to the incident resolve-advice and probable cause information." }, { "step-id": "step-4", "action": "request-confirmation-before-incident-resolution", "target": "incident-56433218", "status": "pending", "observation": "Waiting for confirmation before executing a service-affecting incident resolution action." } ], "result": { "summary": "The incident has been analyzed. Probable cause information has been identified, and an incident resolution action is awaiting confirmation.", "affected-resources": [ "incident-56433218", "svc-1001", "node-a", "node-b", "port-7", "port-3" ], "output-data": { "incident-no": 56433218, "status": "updated", "ack-status": "acknowledged", "next-action": "confirmation-required" } } }

Task Notifications The following examples show A2U task notifications generated during the incident diagnosis and resolution flow. Plan-generated notification: { "task-id": "task-2001", "intent-id": "intent-1002", "notification-type": "plan-generated", "time": "2026-06-30T10:03:00Z", "payload": { "plan-generated": { "step-count": 4, "estimated-duration": 300 } } } Confirmation-required notification: { "task-id": "task-2001", "intent-id": "intent-1002", "notification-type": "confirmation-required", "time": "2026-06-30T10:03:30Z", "payload": { "confirmation-required": { "confirmation-id": "conf-5001", "confirmation-type": "EXECUTION", "priority": 9, "timeout-seconds": 600, "context-schema": "urn:ietf:params:xml:ns:yang:ietf-incident", "summary": "Switch service svc-1001 to the protection path to bypass the affected working path resources.", "allowed-actions": [ "approve", "reject", "escalate-to-human" ] } } } Step-completed notification: { "task-id": "task-2001", "intent-id": "intent-1002", "notification-type": "step-completed", "time": "2026-06-30T10:04:10Z", "payload": { "step-completed": { "step-id": "step-5", "observation": "The incident resolution action was executed. The affected service has been switched to the protection path." } } } Task-completed notification: { "task-id": "task-2001", "intent-id": "intent-1002", "notification-type": "task-completed", "time": "2026-06-30T10:05:00Z", "payload": { "task-completed": { "summary": "Incident 56433218 has been resolved and the related OTN service svc-1001 has been restored. The incident status is updated to cleared.", "affected-resources": [ "incident-56433218", "svc-1001", "node-a", "node-b", "port-7", "port-3" ] } } }

Confirmation Object The following example shows the full confirmation object exposed as A2U operational state data. { "confirmation-id": "conf-5001", "task-id": "task-2001", "type": "EXECUTION", "priority": 9, "timeout-seconds": 600, "context-schema": "urn:ietf:params:xml:ns:yang:ietf-incident", "context": { "incident-no": 56433218, "name": "otn-service-degradation", "type": "problem", "incident-id": "line-fault-svc-1001", "service-instance": [ "svc-1001" ], "domain": "otn", "priority": "critical", "status": "updated", "ack-status": "acknowledged", "category": "network", "detail": "The incident has been analyzed. The probable cause is associated with the working path resources between node-a and node-b.", "resolve-advice": "Switch service svc-1001 to the protection path to bypass the affected working path resources." }, "allowed-actions": [ "approve", "reject", "escalate-to-human" ], "status": "pending" }

Confirmation Resolution RPC The following example shows the input and output of the resolve-confirmation RPC. Input: { "request-id": "req-1003", "correlation-id": "corr-20260630-002", "tenant-id": "tenant-1", "confirmation-id": "conf-5001", "action": "approve", "resolved-by": "operator-a" } Output: { "confirmation-id": "conf-5001", "task-id": "task-2001", "status": "approved", "task-state": "EXECUTING" }

Error Response { "error-type": "unprocessable-content", "error-code": "A2U-INCIDENT-RESOLVE-001", "error-message": "The requested incident resolution action cannot be completed because the protection resource is unavailable.", "retryable": false, "target": "resolve-confirmation.action", "details": { "incident-resolve-error-info": { "incident-no": 56433218, "reason": "resource-unavailable", "description": "The protection path required to bypass the affected working path is unavailable." } } }