CSE561 Problem Set #1

[ summary | background | tutorials | assignment | turn-in | grading | solution ]

Summary

Software-Defined Networking (SDN) refactors the network control plane to enable programmatic control of packet forwarding and increase network flexibility. Instead of having a switch-resident control plane define a forwarding (or routing) information base (e.g., using RIP, OSPF, etc.), the forwarding information base used by each switch's data plane is established by applications running atop a logically centralized SDN controller. These applications operate on a (abstract) view of the network topology to define the forwarding behavior of each (virtual) network switch. The controller translates these directives into forwarding rules which are installed in a flow table at each physical switch. The data plane in each switch matches packets against the rules in the flow table (based on fields in the Ethernet, IP, and transport headers) and the actions (forward, flood, drop, etc.) defined in the matching rule are applied to the packets.

These SDN projects will expose you to how to write SDN applications to achieved some desired control over the forwarding behavior of a network. You will be introduced to OpenFlow (the current industry-wide standard for SDN), common SDN controllers (POX and Floodlight), tools for testing and debugging applications, and the typical software and hardware components included in an actual SDN deployment. Using this knowledge, you will be able to develop several SDN applications that implement basic control over network forwarding and leverage the key capabilities exposed by SDN controllers.

Background material

The two key technologies that we will use in the projects are: (a) OpenFlow: a standardized API that exposes routing/switching functions to a controller, and (b) centralized network controller written using Floodlight or POX that allows you to install appropriate rules in the switches using the OpenFlow API. We will discuss some of this material in class, but there is a wealth of information available on the Web that you can read up on in order to get the context for this work. Here are some such links:

• Youtube talk by Nick McKeown on how SDN will shape networking.
• OpenFlow white paper.
• Read sections 1-4 of OpenFlow spec.
• NOX paper.

You will be using the Mininet VM based system developed by the OpenFlow group to do your assignments. For the controller, we recommend either Floodlight or POX. Here are some tutorials to install Mininet and start using it with Floodlight/POX.

• Parts 1-4 of OpenFlow tutorial provides instructions on how to install Mininet. There is also a video describing how to perform the mininet install. Mininet is also described in the following paper.
• The "Set up network access" instructions are to be modified as follows. Before you open the downloaded VM from VirtualBox, open VirtualBox's "Preferences..." from the menu, navigate to the "Network" tab, and click on the "Add host-only network" button on the right. This will most likely create a "vboxnet0" interface. After you have downloaded the VM, you need to setup the host-only network interface before you open the VM. For this, you click on the "Settings" for the VM, navigate to the "Network" tab, click on Adapter 2, "enable" it and attach it to the "Host-only adapter" that you had created earlier. Then you can follow the instructions listed under "Set up network access".
• Run the following command in your VM to fix the following bug.

  sudo sed -e '450s/IP/MAC/' -i /usr/local/lib/python2.7/dist-packages/mininet-2.0.0-py2.7.egg/mininet/node.py

• Part 5 has information on different types of controllers, including POX and Floodlight.
• Floodlight users: read the How to write a module document.
• POX users: read the following documentation.

As part of the assignment, you will build a learning switch. You might find it useful to look at the Hub code for Floodlight. We also provide you a floodlight skeleton and a pox skeleton on top of which to implement your Learning Switch applications.

Application Design

Write Learning Switch Application

if (source mac address is new)
    record the source mac and input port mapping
if (destination mac address is known)
    install a flow table rule
    forward the packet to the destination
else
    FLOOD the packet

Test Learning Switch Application

sudo mn --topo single,10 --mac --arp --switch ovsk --controller remote,ip=<host_ip> 

mininet> h1 ping -c 10 h10

mininet> h10 iperf -s &
mininet> h1 iperf -c h10

dpctl dump-flows tcp:127.0.0.1:6634 

Useful notes

• We will cover the learning switch material and some of the SDN background material in class on Oct 15th.
• You can assume that ARP is turned off. For extra credit, discuss and implement ARP handling at the centralized controller.
• Watch this space for additional clarifications.
• If you are using the floodlight to implement your Learning Switch application, you should use this property file, replacing the original one at src/main/resources/floodlightdefault.properties. Otherwise, the default property file includes too many modules that overlap with the module you need to implement.

Please turn in a tarball or a zip file at https://catalyst.uw.edu/collectit/dropbox/summary/arvindk/29361.
The archive should have following files:

• your source code with comments;
• a readme file including your name, email address, and the platform you use;
• discussion of what you learnt from the experience.

We will be basing your grade on several elements:

• Whether your code works! It should be correct, compile without warnings, and not leak memory, processes, descriptors, etc.
• How well structured your code is: you should have clean module interfaces, a nice decomposition, good comments, and so on.

Learning Switch: FloodLight, Pox