1. Background
The O-RAN architecture includes a Real-Time (RT) Radio Intelligent Controller (RIC) that is connected via A1 interface to Non-Real Time RIC function that resides in the Service Management and Orchestration (SMO) layer. The purpose of A1 interface is to enable Non-RT RIC function to provide policy-based guidance, AI/ML model management, and enrichment information to the near-RT RIC for RAN optimization.
2. High-Level Architecture and Use Cases
The overall Use Case Flow (DMAAP <--> SDNR/A1 REST Adapter <--> A1 Mediator) is as follows:
- Any ONAP or micro-service that wants to perform any policy management related activity will publish a DMAAP message, with appropriate request
- DMAAP listener will consume the DMAAP message and invoke RPC against A1 Adapter
- A1 Adapter, based on the received DMAAP message/RPC, will invoke corresponding REST API's against A1 Mediator in Near-RT RIC
The picture below depicts overall use case flow
3. High-Level Design and Implementation Approach
For Frankfurt, only A1 Policy Management is supported.
The solution leverages existing CCSDK/SDNR code base and SDNC Dmaap Listener, and below depicts implementation approach:
4. North-bound RPC YANG Model
YANG model for north-bound RPC's for A1 Adapter can be found at: https://gerrit.onap.org/r/gitweb?p=ccsdk/features.git;a=blob;f=sdnr/northbound/a1Adapter/model/src/main/yang/A1-ADAPTER-API.yang;h=fb740cc2731ba8ab76977450b9bc31578bff9f16;hb=refs/heads/master
The below picture depicts the overall YANG tree.
5. DMAAP Message Format
Following are DMAAP message formats for topics A1-P and A1-P-RSP.
DMAAP Message Request (sent from ONAP or MS components):
Topic: A1-P { "body": { "input": { "CommonHeader": { "TimeStamp": "2018-11-30T09:13:37.368Z", "APIver": "1.0", "RequestID": "9d2d790e-a5f0-11e8-98d0-529269fb1459", "SubRequestID": "1", "RequestTrack": {}, "Flags": {} }, "Action": "getNearRT-RICs", "Payload": {"input": {"dummy": "dummy"}} }, "version": "1.0", "rpc-name": "getNearRT-RICs", "correlation-id": "9d2d790e-a5f0-11e8-98d0-529269fb1459-1", "type": "request" } } |
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DMAAP Message Response (sent from A1 Mediator with status response)
Topic: A1-P-RSP
{ "body": { "output": { "CommonHeader": { "TimeStamp": "2018-09-10T07:10:05.614Z", "APIver": "1.0", "RequestID": "9d2d790e-a5f0-11e8-98d0-529269fb1459", "SubRequestID": "1", "RequestTrack": [], "Flags": [] }, "Status": { "Code": 200, "Value": "SUCCESS" }, "Payload": "" } }, "version": "1.0", "rpc-name": "getNearRT-RICs", "correlation-id": "9d2d790e-a5f0-11e8-98d0-529269fb1459-1", "type": "response" } |
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DMAAP message payload is aligned with YANG RPC Input parameters and is exactly the same as, when YANG model RPC input is rendered as a JSON object. See the above example, where DMAAP message is related to RPC "getNearRT-RICs".
IMPORTANT: Please note that “input” key needs to be included in the payload. Escape characters ARE NOT to be INCLUDED.
6. A1 Mediator References
The A1 Mediator Open API's can be referenced at: https://gerrit.o-ran-sc.org/r/gitweb?p=ric-plt/a1.git;a=history;f=a1/openapi.yaml;h=2aa7a943eea23dff79a40917273c1bf43b1ae7d9;hb=445221bb8e531d77aad987b936b30d385521134f
A1 Adapter in Frankfurt is implemented against A1 Mediator OpenAPI version 1.0.0, and will be updated to support the latest A1 Mediator OpenAPI version 2.1.0. It is observed that there are no substantial material differences between API's for versions 1.0.0 and 2.1.0.
7. Deployment Considerations
9. A1 Mediator Testing
The following depicts DMAAP to RPC to A1 Mediator REST API flow, and test cases are also mapped against this flow.
Mapping of flow to Test Cases described here:
Following is the current testing environment in the WIndriver Lab:
A1 Mediator deployed currently conforms to OpenAPI Version 1.0.0; and the OpenAPI latest version is 2.1.0. It is observed that there are no substantial material differences between API's for versions 1.0.0 and 2.1.0.