Welcome to the SDN-IP tutorial!
This tutorial is designed to be an introduction to how SDN-IP runs in practice. We'll go through starting up a simple emulated network, and we'll see how SDN-IP controls this network to move data from place to place.
If you haven't done so already, it's highly recommended that you go through the ONOS Tutorial first. This will give you some familiarity with the basic functionality of ONOS. In addition, you should read through the SDN-IP Architecture <LINK> document to get an overview of how SDN-IP works.
Hopefully you've already done the ONOS tutorial, so you already have the ONOS tutorial VM available. If not, check out the Setup your environment <LINK> section of the ONOS tutorial to get the VM ready.
Start up the network
We've prepared a simple emulated Mininet topology, which contains 6 OpenFlow switches. Connected around the edges of the SDN network are 4 emulated routers. The routers run Quagga, which is an open-source routing suite. In our case we run the BGP part of Quagga on them, to simulate external BGP routers belonging to other administrative domains. The goal of SDN-IP is to be able to talk BGP with these routers in order to exchange traffic between the different external ASes.
This figure shows the topology as observed by ONOS. We can see 6 blue OpenFlow switches, and 5 hosts around the edge.
The host labelled "bgp" is our Internal BGP Speaker. It sits inside our SDN network, and its job is to peer with all the External BGP Routers, learn BGP routes from them, and relay those routes to the SDN-IP application running on ONOS.
The other four hosts, labelled r1 through r4, are the External BGP Routers. They are the border routers that reside in other networks that want to exchange traffic with us.
Behind each router is a host, and these are labelled h1 through h4 in Mininet. ONOS can't see these hosts, because the reside in other network that are not controlled by ONOS.
We can look at the configuration of the hosts in the Mininet terminal.
Each host is in a different IP subnet. When SDN-IP is up and running, these hosts will be able to communicate with one another despite being in different networks. This is because the SDN network is able to route traffic based on BGP routes.
Double-click the "SDN-IP Mininet" icon on the desktop to start up the network.
Also, double-click the "ONOS" icon on the desktop to start up the ONOS console. If you run the "devices" command, you should see the network has started up and connected to ONOS.
Installing the SDN-IP application
If you try and ping between any two hosts right now, you'll notice nothing is working.
Even though ONOS is running and connected to switches, there are no applications loaded so there is nothing to tell ONOS how to control the network. We can also use the summary command to verify there are no flows or intents in the network.
First we need to install some helper applications that SDN-IP relies on. These features let ONOS read in various configuration files and respond to ARP requests on behalf of hosts.
Now lets install the SDN-IP application so we can get some traffic flowing between our networks.
A lot happens as soon as we install the SDN-IP application. The first thing it does is install point-to-point intents to allow the external BGP peers to communicate with our internal BGP speaker. This allows the external BGP routers to relay the routes they are capable of forwarding through to SDN-IP.
We can see the routes that SDN-IP has learnt with the "routes" command.
Don't worry if you don't see all of the routes straight away - sometimes it takes a minute or so for the BGP sessions to establish and advertise the routes to ONOS.
Now that ONOS has learnt some routes, it has programmed those routes into the switches using the intent API. If we look at the intent summary, we can see the different intents that SDN-IP is using.
We see a total of 28 intents. The 24 PointToPointIntents are simple end-to-end flows which allow the external BGP routers to communicate with our internal BGP speaker. The 4 MultiPointToSinglePoint intents are the forwarding rules for the routes that we've learnt through BGP. Each route is translated into one MultiPointToSinglePoint intent which matches the traffic for that route at the ingress ports of the network, and forwards it along to the router who advertised the route to us. This is how we use routing information learnt from BGP to enable traffic to transit our network on these routes.
Now that the intents are installed, we can ping through the network. Go back to the Mininet console and try ping between a pair of hosts.
The ping succeeds!