ONOS, Open Network Operating System, is a newly released open-source SDN controller that is focused on service provider use-cases. The platform is written in Java and uses OSGi for functionality management. Similar to OpenDaylight, the individual features are loaded using the OSGi runtime called Karaf. In the SDN Hub tutorial VM we provide, you will find a pre-compiled version of ONOS 1.1.0. Alternatively, we make available an ONOS Docker container repository.

1. Architecture

The platform is modular and built with 1) application intents, and 2) network topology graph as the top level abstractions that applications uses to program the underlying hardware. These intents gets translated to OpenFlow rules that are programmed on the switches using the southbound plugin. Below is a high-level architecture of ONOS. In the top application layer, we show the list of sample applications that are included in the current releases.


2. Running ONOS

  • Setting the environment variables for ONOS and Karaf execution
$ cd onos
$ source ./tools/dev/bash_profile 
$ echo $KARAF_ROOT
  • Optionally, you can compile the controller using the commands:
$ mvn clean install -nsu -DskipIT -DskipTests
  • Running the controller involves loading the required modules. If everything went well, you will see the ONOS banner printed on the screen. At this point, the controller listens on port 8181 for UI, and ports [6633, 6635 and 6635] for OpenFlow
$ karaf clean
Welcome to Open Network Operating System (ONOS)!
     ____  _  ______  ____   
    / __ \/ |/ / __ \/ __/    
   / /_/ /    / /_/ /\ \       
Hit '' for a list of available commands
and '[cmd] --help' for help on a specific command.
Hit '' or type 'system:shutdown' or 'logout' to shutdown ONOS.
  • In our VM installation, we have pre-loaded certain features by including it in ~/onos/apache-karaf-3.0.2/etc/org.apache.karaf.features.cfg file in the featuresBoot key. This runs the single-instance (trivial) ONOS core, simple L2 forwarding, and Web GUI modules.
  • You can verify if all those were loaded by executing this command on the Karaf console.
onos> feature:list -i
Name                 | Version          | Installed | Repository              | Description                                       
standard             | 3.0.2            | x         | standard-3.0.2          | Karaf standard feature                            
config               | 3.0.2            | x         | standard-3.0.2          | Provide OSGi ConfigAdmin support                  
region               | 3.0.2            | x         | standard-3.0.2          | Provide Region Support                            
package              | 3.0.2            | x         | standard-3.0.2          | Package commands and mbeans                       
http                 | 3.0.2            | x         | standard-3.0.2          | Implementation of the OSGI HTTP Service           
war                  | 3.0.2            | x         | standard-3.0.2          | Turn Karaf as a full WebContainer                 
kar                  | 3.0.2            | x         | standard-3.0.2          | Provide KAR (KARaf archive) support               
ssh                  | 3.0.2            | x         | standard-3.0.2          | Provide a SSHd server on Karaf                    
management           | 3.0.2            | x         | standard-3.0.2          | Provide a JMX MBeanServer and a set of MBeans in K
scr                  | 3.0.2            | x         | standard-3.0.2          | Declarative Service support                       
onos-thirdparty-base | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS 3rd party dependencies                       
onos-thirdparty-web  | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS 3rd party dependencies                       
onos-api             | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS services and model API                       
onos-core-trivial    | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS core components                              
onos-gui             | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS GUI console components                       
onos-cli             | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS admin command console components             
onos-openflow        | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS OpenFlow API, Controller & Providers         
onos-app-fwd         | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS sample forwarding application                
onos-app-mobility    | 1.1.0-SNAPSHOT   | x         | onos-1.1.0-SNAPSHOT     | ONOS sample mobility application                  
pax-jetty            | 8.1.15.v20140411 | x         | org.ops4j.pax.web-3.1.2 | Provide Jetty engine support                      
pax-http             | 3.1.2            | x         | org.ops4j.pax.web-3.1.2 | Implementation of the OSGI HTTP Service           
pax-http-whiteboard  | 3.1.2            | x         | org.ops4j.pax.web-3.1.2 | Provide HTTP Whiteboard pattern support           
pax-war              | 3.1.2            | x         | org.ops4j.pax.web-3.1.2 | Provide support of a full WebContainer            

  • Our VM includes the following features pre-installed and set to run when the ONOS karaf container is started:
    • onos-api: Required service interface from defining the API for cross-module interaction
    • onos-core-trivial: Single-instance version of the core layer
    • onos-openflow: OpenFlow plugin/driver that uses Loxigen for wire-protocol handling
    • onos-cli: Implements Karaf CLI commands listed in Section 3.1 below.
    • onos-app-fwd: Reactive-fwding L2 learning switch, and proxy ARP functionality to prevent ARP flooding
    • onos-app-mobility: Host mobility handler that cleans up flowmods when a host moves
    • onos-gui: Javascript-based UI that uses websockets and visualizes the topology
  • All other dependencies or bundles that are not part of the git repository is loaded by maven, at compile time, from http://repo.maven.apache.org/maven2/org/onosproject.
  • You can stop any of these features by issuing the command “feature:uninstall”.
  • Since we have the OpenFlow feature and L2 forwarding feature started already, we can connect one or more switches to the controller, and manage the forwarding. In the tutorial VM, you can start mininet to emulate a network of switches and hosts using this command:
$ sudo mn  --topo linear,2 --mac --switch ovsk,protocols=OpenFlow13 --controller remote --arp
mininet> h1 ping h2
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=26.4 ms
64 bytes from icmp_seq=2 ttl=64 time=1.69 ms
  • Inspect the hosts already learned by the controller using the hosts command on the Karaf console.
onos> hosts
id=00:00:00:00:00:01/-1, mac=00:00:00:00:00:01, location=of:0000000000000001/1, vlan=-1, ip(s)=[]
id=00:00:00:00:00:02/-1, mac=00:00:00:00:00:02, location=of:0000000000000002/1, vlan=-1, ip(s)=[]
  • The ONOS controller is performing LLDP to learn the links in the topology and computes the path between two hosts. So, it is possible to statically program connectivity without using the onos-app-fwd feature.
  • Stop the onos-app-fwd feature and perform a ping between the hosts. The ping will fail.
  • Then, add static host intents for bi-directional communication between two hosts. This translates to two unidirectional path rules.
onos> feature:uninstall onos-app-fwd
onos> add-host-intent 00:00:00:00:00:01/-1 00:00:00:00:00:02/-1 
onos> add-host-intent 00:00:00:00:00:02/-1 00:00:00:00:00:01/-1 
  • After adding the intent, you will again be able to ping between hosts h1 and h2. (Caveat: If the hosts need ARP resolution, that will not work because there is no rule to flood the ARP).
  • Lastly, on the tutorial VM, you can open the Firefox browser and visit http://localhost:8181/onos/ui/index.html to see the Javascript-based UI of ONOS. Once the UI page opens, you can press ? (question mark) to get a list of UI features.

3. Features and Applications

3.1. ONOS Karaf CLI commands

There are several commands available on the Karaf console to do stateĀ checks and debugging. Here is a list of features available as of this 1.1.0 release:

Command Information
onos:add-flows Installs a flow rules
onos:add-host-intent Installs host-to-host connectivity intent
onos:add-multi-to-single-intent Installs point-to-point connectivity intent
onos:add-optical-intent Installs optical connectivity intent
onos:add-point-intent Installs point-to-point connectivity intent
onos:add-single-to-multi-intent Installs connectivity intent between multiple egress
onos:address-bindings Lists all configured address port bindings.
onos:apps Lists application ID information
onos:balance-masters Forces device mastership rebalancing
onos:cluster-devices Lists devices of the specified topology cluster in t
onos:cluster-links Lists links of the specified topology cluster in the
onos:clusters Lists all clusters in the current topology
onos:device-remove Removes an infrastructure device
onos:device-role Sets role of the controller node for the given infra
onos:devices Lists all infrastructure devices
onos:flows Lists all currently-known flows.
onos:get-stats Fetches stats for a connection point
onos:host-remove Removes an end-station host
onos:hosts Lists all currently-known hosts.
onos:intents Lists the inventory of intents and their states
onos:leaders Finds the leader for particular topic.
onos:links Lists all infrastructure links
onos:masters Lists device mastership information
onos:metrics Prints metrics in the system
onos:nodes Lists all controller cluster nodes
onos:paths Lists all shortest-paths paths between the specified
onos:ports Lists all ports or all ports of a device
onos:push-random-intents Installs random intents to test throughput
onos:push-test-intents Installs random intents to test throughput
onos:remove-intent Removes the specified intent
onos:resource-allocations Lists allocations by link
onos:resource-available Lists available resources by link
onos:roles Lists mastership roles of nodes for each device.
onos:summary Provides summary of ONOS model
onos:tablet-leader Prints the current leader of a tablet.
onos:tablet-member Lists all member nodes
onos:topology Lists summary of the current topology
onos:wipe-out Wipes-out the entire network information base, i.e. devices, links, hosts, intents.

3.2. Writing an Application on ONOS

There is a template application called apps/foo to jumpstart your app development with ONOS. There are services provided by the platform for many of the typical functions using exported services:

  • IntentService: programming intents and listening to other intents
  • FlowRuleService: OpenFlow rules and listening to other rules being programmed
  • PacketService: performing packet_out operations
  • DeviceService: extract switch inventory and track its changes
  • TopologyService: extract topology graph and track its changes

3.3 Clustering

ONOS 1.1.0 supports running multiple controllers in a clustered mode where they share state among each other. Furthermore, when the underlying OpenFlow switches are connected to more than 1 controller, they determine which controller should be the master and which should be the standby/slave. This is very useful for fault tolerance and high availability purposes.

To enable this feature, you need to perform the following two steps before starting Karaf:

  1. Update that the subnet listed in the file apache-karaf-3.0.2/etc/hazelcast.xml to same subnet corresponds to.
  2. Update the featuresBoot parameter in apache-karaf-3.0.2/etc/org.apache.karaf.features.cfg to list the onos-core feature instead of the onos-core-trivial feature.

After this, you are ready to spin up multiple instances of the controller. Since each controller listens on the same TCP ports (e.g., 6633 for OpenFlow and 5701 for the Hazelcast), you will need to spawn each controller within a separate Docker container or a VM. To learn more about ONOS clustering, read this blog post dedicated to the clustering feature.