README.md

gNMI Telemetry Proof of Concept - Recipe

The purpose of this prototype is collect data of gNMI sources from the Semantic Data Aggregator (SDA). For this proof of concept with gNMI data sources, the prototype has two main resources: docker instances of Arista cEOS routers as network devices and YANG-based data sources that support the gNMI management protocol and a CLI client that provides a full support of gNMI RPCs called gNMIc to request the configuration and operational status from these telemetry-based network devices.

Here are the most important steps to be able to run the gNMI-based data collection prototype and extract telemetry information of Arista cEOS routers using the gNMIc client from the SDA:

1. Before starting docker-compose it is necessary to import the Arista cEOS router docker image. Specifically, the scenario uses one of the latest available Arista cEOS versions cEOS-lab-4.25.4M. Download it first from the Arista software section (it is the 64-bit version).

2. The command to import the image is:

docker import cEOS64-lab-4.25.4M.tar.xz ceos-image:4.25.4M

3. Then you can start the docker-compose, which raises two instances of Arista cEOS routers (ceos1 and ceos2 docker services). These docker services are responsible for configuring environment variables, configuring TCP access ports for gNMI, and creating two P2P networks between both routers. The command to start the docker-compose is:

docker-compose -f docker-compose-arista.yml up

4. Once the docker-compose is up, it is necessary to perform a very basic configuration of the ceos1 and ceos2 routers to enable the gNMI protocol. Example for ceos1:

• To access the CLI of ceos1:

docker exec -it ceos1 Cli
localhost>enable

• gRPC/gNMI configuration:

localhost#configure terminal
localhost(config)#hostname ceos1
ceos1(config)#username admin secret xxxx
ceos1(config)#management api gnmi
ceos1(config-mgmt-api-gnmi)#transport grpc default
ceos1(config-gnmi-transport-default)#end
ceos1#write memory

5. In order to play with the gNMIc client, a series of steps and RPCs execution examples are shown:

• The nifi docker container has gNMIc installed.
• To learn about the gNMI capabilities of ceos1 (which gNMI version the device runs, what models it is loaded with and which encoding it understands).

root@nifi:/opt/nifi/nifi-current# gnmic -a ceos1:6030 -u admin -p xxxx --insecure capabilities
Capabilities Response:
gNMI version: 0.7.0
supported models:
  - openconfig-bgp-policy, OpenConfig working group, 5.0.1
  - openconfig-packet-match-types, OpenConfig working group, 1.0.1
  - arista-intf-deviations, Arista Networks, Inc.,
  ...
  - openconfig-isis, OpenConfig working group, 0.6.0
supported encodings:
  - JSON
  - JSON_IETF
  - ASCII

• Arista community publishes its YANG models in a GitHub repository. To analyze and understand the structure of YANG models, the Python tool pyang is very useful (they have not published the updated models for version 4.24.5M, and 4.24.2F is the latest available). As an example, we can parse the openconfig-interfaces.yang module using the pyang command:

pyang -f tree -p yang yang/EOS-4.24.2F/openconfig/public/release/models/interfaces/openconfig-interfaces.yang

• To request information (Get RPC) about a specific leaf node of an available YANG tree module (example for the openconfig-interfaces.yang module and the in-octets node):

root@nifi:/opt/nifi/nifi-current# gnmic -a ceos1:6030 -u admin -p xxxx --insecure get --path "/interfaces/interface[name=Ethernet1]/state/counters/in-octets"
Get Response:
[
  {
    "time": "1970-01-01T00:00:00Z",
    "updates": [
      {
        "Path": "interfaces/interface[name=Ethernet1]/state/counters/in-octets",
        "values": {
          "interfaces/interface/state/counters/in-octets": 37484
        }
      }
    ]
  }
]

• To subscribe to information (Subscribe RPC) about a specific leaf node of an available YANG tree module ((1) on-change or (2) sample subscription modes):

(1) root@nifi:/opt/nifi/nifi-current# gnmic -a ceos1:6030 -u admin -p xxxx --insecure subscribe --path "/interfaces/interface[name=Ethernet1]/state/counters/in-octets" --stream-mode on_change --qos 0

(2) root@nifi:/opt/nifi/nifi-current# gnmic -a ceos1:6030 -u admin -p xxxx --insecure subscribe --path "/interfaces/interface[name=Ethernet1]/state/counters/in-octets" --stream-mode sample --sample-interval 5s --qos 0

• /gnmi/gnmic-cfgs/cfg-subscriptions.json is the configuration file used to automate the gNMI subscriptions and store the information monitored in the Kafka data data substrate of the aggregator. Weaver is the building block in charge of parameterizing the file values regarding the type and subscription interval, the YANG path of the data to be monitored, the address and port of the endpoint and the Kafka topic. To be able to do a subscription test with gNMIc using this configuration file, you can run the following example commands ((1) sample or (2) on-change subscription modes):

(1) root@nifi:/opt/nifi/nifi-current# gnmic --config /gnmic-cfgs/cfg-subscriptions.json subscribe --name sample

(2) root@nifi:/opt/nifi/nifi-current# gnmic --config /gnmic-cfgs/cfg-subscriptions.json subscribe --name on-change

In the message bus of the kafka docker container, a new topic will appear where new entries will be written according to the type of subscription chosen.

• NGSI-LD API Orchestrator Postman collection has a set of requests that can be used to model a NGSI-LD datapipeline with TelemetrySource entities and extract the telemetry information of the Arista cEOS devices from the Semantic Data Aggregator using gNMIc.