Thursday, November 19, 2020


Multipass is a command line tool for running Ubuntu virtual machines on Mac or Windows. Multipass uses the native virtualization capabilities of the host operating system to simplify the creation of virtual machines.

Docker testbed and Docker DDoS testbed describe how to use containers to experiment with network visibility and control. However, not all software is amenable to running in containers, and so the ability to quickly create and configure virtual machines is a useful complement. This article demonstrates how to use Multipass to quickly build a virtual machine to run Mininet network emulation software.
multipass launch --name=mininet bionic
multipass exec mininet -- sudo apt update
multipass exec mininet -- sudo apt -y install mininet python-ryu
multipass exec mininet -- sudo apt -y install default-jre python-requests hping3
multipass exec mininet -- wget
multipass exec mininet -- tar -xzf sflow-rt.tar.gz
multipass exec mininet -- ./sflow-rt/ sflow-rt mininet-dashboard

Run the above commands in a terminal to create the virtual machine. Multipass commands can easily be scripted to automate the creation and configuration of virtual machines.

multipass list
List the virtual machines.
Name                    State             IPv4             Image
test                    Running      Ubuntu 18.04 LTS

Find the IP address of the mininet virtual machine we just created (

multipass exec mininet -- ./sflow-rt/

Start sFlow-RT.

Use a web browser to connect to the VM and access the Mininet Dashboard application running on sFlow-RT, in this case
multipass exec mininet -- sudo mn --custom sflow-rt/extras/ \
--link tc,bw=10 --topo tree,depth=2,fanout=2 --test iperf
In a separate terminal, run a test using Mininet.
The Mininet Dashboard shows the test traffic, the links in the emulated network carrying the traffic, and the diameter of the emulated network.
The Topology tab shows a Mininet weathermap, displaying a dynamic view of topology in which link widths update in real-time to reflect traffic flowing over the virtual network.

An external SDN controller can be used to control packet forwarding in the network.
multipass exec mininet -- ryu-manager,
Start the Ryu SDN controller in a terminal window.
multipass exec mininet -- sudo mn --custom sflow-rt/extras/ \
--link tc,bw=10 --topo tree,depth=2,fanout=2 \
--controller=remote,ip= --test iperf
Run the same test as before, but this time connecting to the SDN controller. For a more interesting example, Ryu measurement based control describes how to detect and block denial of service attacks using the controller.

There are additional multipass commands available to manage the virtual machine.
multipass shell mininet
Connect to the virtual machine and access a command shell.
multipass stop mininet
Stop the virtual machine.
multipass start mininet
Start the virtual machine.
multipass delete mininet
multipass purge
Delete the virtual machine.

There are a number of Mininet articles on this blog describing projects that can be run using the virtual machine that demonstrate performance aware software defined networking concepts.

Friday, November 13, 2020

sFlow Monitoring for AI

A Proposal towards sFlow Monitoring Dashboards for AI-controlled NRENs is a recent talk by Mariam Kiran (Esnet) presented at the recent GÉANT Telemetry and Big Data Workshop.
In the talk, Miram describes the set open source tools (Netdata, Prometheus, Zabbix, Ntopng, and PerfSONAR) that they attempted to synthesize a complete picture of the network.
A number of tools were combined since each tool provides a different subset of the measurements needed to drive the AI controller. 
Integrating the data from the different sources was a challenge, but they were able to pull the data together into a single Grafana dashboard. Unfortunately, there was a lot of noise in legacy measurement schemes, making the data set unsuitable for training the AI controller.
The team decided to go toward sFlow, replacing the legacy monitoring tools with sFlow enabled devices, in order to generate the very clean data needed for machine learning.

For background, the talk, Real-time network telemetry for automation, describes why sFlow is uniquely suited to automation, providing the comprehensive, real-time, system-wide, visibility needed to make networked systems observable.

Thursday, November 12, 2020

Real-time network telemetry for automation

The video discusses telemetry and requirements for network automation, providing an overview of sFlow measurement architecture and a discussion of recently added packet drop monitoring functionality, and ending with a live demonstration of GPU compute cluster analytics. The slides from the video are available here.

The video is part of recent talk Using Advanced Telemetry to Correlate GPU and Network Performance Issues [A21870] presented at the NVIDIA GTC conference

Wednesday, November 11, 2020


Introducing DENT OS, switchdev NOS for the rest of us talk, presented at the recent Open Source Summit, describes the Linux Foundation DENT project. The slides from the presentation are available.

Linux switchdev is an in-kernel driver model for switch devices which offload the forwarding (data) plane from the kernel. Integrating switch ASIC drivers in the Linux kernel makes switch ports appear as additional Linux network interfaces that can be configured and managed using standard Linux tools. 

DENT is an Ubuntu based Linux distribution that packages the drivers for switch hardware (fans, temperature sensors, ASIC, etc) along with the open source FRRouting routing protocol suite which includes protocol daemons for BGP, IS-IS, LDP, OSPF, PIM, and RIP. The FRRouting software uses the Linux netlink API to program Linux kernel packet forwarding, which on a hardware switch platform is offloaded by the switchdev driver to the ASIC for line rate forwarding.

A major benefit of DENT's approach to making Linux into the network operating system is that the same tools used to configure, manage and monitor Linux servers can also be used to manage network switches. In addition, a DENT virtual machine behaves in exactly the same way as DENT running on a physical switch, allowing configurations to be validated in virtual environments before being pushed into the production network.

The open source Host sFlow agent streams standard sFlow telemetry from Linux hosts. On a switchdev based network switch, hardware counters are gathered using standard Linux API's for monitoring network interfaces. The Host sFlow agent also supports Linux psample and drop_monitor APIs that provide visibility into packet flows and dropped packets. On hardware switches, the switchdev driver offloads these measurements to the switch ASIC which provides line rate visibility into packet forwarding. 
Installing Host sFlow agents on DENT OS based switches activates the standard sFlow hardware instrumentation in switch ASICs to stream network telemetry to an sFlow collector, for example sFlow-RT, for the real-time network-wide view of performance needed to drive automation.