Micro SID DEMO with P4 and ONOS

This demo is based on the P4 tutorial by Open Networking Foundation. As such, it is possible to find more information about the above listed software modules in their repository. There you can also find useful material like the slides explaining the tutorial and a prepared Ubuntu virtual machine with all the software installed. It is strongly recommended to download the prepared VM and run the DEMO inside it, as it contains the several dependencies needed to run the software.

In the following, we will present only the steps needed to run the SRv6 micro SID demo, starting from the downloaded VM.

Repository structure

This repository is structured as follows:

p4src/ P4 implementation
app/ ONOS app Java implementation
mininet/ Mininet script to emulate a topology of stratum_bmv2 devices
config/ configuration files
video/ contains a record of a DEMO for the two use cases

DEMO overview

The demo runs on a mininet topology made up of fourteen P4 enabled switches (based on bmv2 P4 software implementation) and two hosts that represent Site A and Site B. For this demo we rely on static routing for simplicity.

The Onos controller is used to configure the P4 software switches with the various table entries, e.g. SRv6 Micro SID routes, L2 forwarding entries, etc.

DEMO commands

To ease the execution of the commands needed to setup the required software, we make use of the Makefile prepared by the ONF for their P4 tutorial.

Make command	Description
`make start`	Runs ONOS and Mininet containers
`make onos-cli`	Access the ONOS command line interface (CLI)
`make app-build`	Builds the tutorial app and pipeconf
`make app-reload`	Load the app in ONOS
`make mn-cli`	Access the Mininet CLI
`make netcfg`	Pushes netcfg.json file (network config) to ONOS
`make stop`	Resets the tutorial environment

Detailed DEMO description

1. Start ONOS

In a terminal window, start the ONOS main process by running and connect to the logs:

$> make start
$> make onos-log

2. Build and load the application

An application is provided to ONOS as an executable in .oar format. To build the source code contained in app/ issue the following command:

$> make app-build

This will create the srv6-uSID-1.0-SNAPSHOT.oar application binary in the app/target/ folder.

Moreover, it will compile the p4 code contained in p4src creating two output files:

bmv2.json is the JSON description of the dataplane programmed in P4;
p4info.txt contains the information about the southbound interface used by the controller to program the switches.

These two files are symlinked inside the app/src/main/resources/ folder and used to build the application.

After the creation of the binary, we have to load it inside ONOS:

$> make app-reload

The app should now be registered in ONOS.

3. Push the network configuration to ONOS

ONOS gets its global network view thanks to a JSON configuration file in which it is possible to encode several information about the switch configuraton. This file is parsed at runtime by the application and it is needed to configure, e.g. the MAC addresses, SID and uSID addresses assigned to each P4 switch.

Let's push it to ONOS by prompting the following command:

$> make netcfg

Now ONOS knows how to connect to the switches set up in mininet.

4. Insert the SRv6 micro SID routing directives

In a new window open the ONOS CLI with the following command:

$> make onos-cli

For the purpose of this DEMO, we statically configured the IPv6 routes of each router inside the config/routing_tables.txt file consisting of a list of route-insert commands. Also the uA Instructions are contained in the config/ua-config.txt in the form of a list of uA-insert commands. Configure them inside the switches by sourcing this file inside the CLI:

onos-cli> source /config/routing_tables.txt
onos-cli> source /config/ua_config.txt

Then, we can insert the uSID routing directive to the the two end routers, one for the path H1 ---> H2 and one for the reverse path H2 ---> H1:

onos-cli> srv6-insert device:r1 fcbb:bb00:8:7:2:fd00:: 2001:1:2::1
onos-cli> srv6-insert device:r2 fcbb:bb00:7:8:1:fd00:: 2001:1:1::1

Essentially, these commands specify to the end routers (R1 and R2) to insert an SRv6 header with a list of SIDs. The first represents the list of uSID that the packet must traverse while the last is the IPv6 address of the host the packet is destined to.

In the config/srv6-insert.txt file, there are the commands for both Use Case 1 and Use Case 2.

6. Test

Test the communication between the two hosts with ping inside mininet.

$> make mn-cli
mininet> h2 ping h1
mininet> h1 ping h2

The first pings will not work since the switch will not know how to reach the host at L2 layer. After learning on both paths it will work.

It is also possible to have a graphical representation of the running topology thanks to the ONOS web UI. Type in a browser localhost:8181/onos/ui and enter as user onos with password rocks. It will display the graphical representation of the topology.

Now, let's make some faster pings:

mininet> h1 ping h2 -i 0.1

Then, return to the UI and press

h to show the hosts
l to display the nodes labels
a a few times until it displays link utilization in packets per second

dkalog / europ4_2020