Monday, February 28, 2022

Topology aware fabric analytics

Real-time telemetry from a 5 stage Clos fabric describes how to emulate and monitor the topology shown above using Containerlab and sFlow-RT. This article extends the example to demonstrate how topology awareness enhances analytics.
docker run --rm -it --privileged --network host --pid="host" \
  -v /var/run/docker.sock:/var/run/docker.sock -v /run/netns:/run/netns \
  -v ~/clab:/home/clab -w /home/clab \ bash
Start Containerlab.
curl -O
Download the Containerlab topology file.
sed -i "s/prometheus/topology/g" clos5.yml
Change the sFlow-RT image from sflow/prometheus to sflow/topology in the Containerlab topology. The sflow/topology image packages sFlow-RT with useful applications that combine topology awareness with analytics.
containerlab deploy -t clos5.yml
Deploy the topology.
curl -O
Download the sFlow-RT topology file.
curl -X PUT -H "Content-Type: application/json" -d @clos5.json \
Post the topology to sFlow-RT.
Connect to the sFlow-RT Topology application, http://localhost:8008/app/topology/html/. The dashboard confirms that all the links and nodes in the topology are streaming telemetry. There is currently no traffic on the network, so none of the nodes in the topology are sending flow data.
docker exec -it clab-clos5-h1 iperf3 -c
Generate traffic. You should see the Nodes No Flows number drop as switches in the traffic path stream flow data. In a production network traffic flows through all the switches and so all switches will be streaming flow telemetry.
Click on the Locate tab and enter the address Click submit to find the location of the address. Topology awareness allows sFlow-RT to examine streaming flow data from all the links in the network and determine switch ports and MAC addresses associated with the point of ingress into the fabric.
Connect to the sFlow-RT Fabric Metrics application, http://localhost:8008/app/fabric-metrics/html/. The Traffic charts identifies each iperf3 test as a large (elephant) flow - see SDN and large flows for a discussion of the importance of large flow visibility. The Busy Links chart reports the number of links in the topology with a utilization exceeding a threshold (in this case 80% utilization).
The Ports tab contains charts showing switch ports with the highest ingress/egress utilization, packet discards, and packet errors.
Connect to the sFlow-RT Trace Flow application,  http://localhost:8008/app/trace-flow/html/.
Enter a traffic filter and click Submit.
docker exec -it clab-clos5-h1 iperf3 -c
Run an iperf3 test and the path the traffic takes across the network topology will be immediately displayed.
Connect to the sFlow-RT Flow Browser application, http://localhost:8008/app/browse-flows/html/index.html?keys=ipsource&value=bps. Run a sequence of iperf3 tests and the traffic will be immediately shown. Defining Flows describes flow attributes that can be added to the query to examine inner / outer tunneled traffic, VxLAN, MPLS, GRE, etc.

Trace Flow demonstrated that flow telemetry is streamed by each switch port along the path from source to destination host to deliver end-to-end visibility. Simply summing the data would overestimate the size of the flow. Adding topology information allows sFlow-RT to intelligently combine data, eliminating duplicate measurements, to provide accurate measurements of traffic crossing the fabric.

containerlab destroy -t clos5.yml
When you are finished, run the above command to stop the containers and free the resources associated with the emulation.

Moving the monitoring solution from Containerlab to production is straightforward since sFlow is widely implemented in datacenter equipment from vendors including: A10, Arista, Aruba, Cisco, Edge-Core, Extreme, Huawei, Juniper, NEC, Netgear, Nokia, NVIDIA, Quanta, and ZTE. In addition, the open source Host sFlow agent makes it easy to extend visibility beyond the physical network into the compute infrastructure.

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