CSCI 4211: Introduction to Computer Networks - Zhi-Li Zhang - Programming Project 3
Virtual networks provide a good framework for testing and experimenting with
networking environments in a safe and configurable way. Additionally, SDNs (Software Defined
Networks) provide an added level of ease of network management for both real and simulated
environments through centralized configuration and monitoring. Note: this is a group assignment
of 1-3 people.
Your Assignment:
● You will create virtual networks with Mininet, evaluate them, and then build SDN
controller logic for them
● Setup the Testing Environment
○ Download the VM containing Mininet
■ (download the i386.zip one, and if it doesn’t work later try the amd64.zip)
○ Install a Virtual Machine Manager (VMM)
■ You can use any virtualization system of your choice, but we recommend
installing Virtualbox (and the follow instructions use it). It is free and runs
on Windows, Linux, and macOS.
○ Start your VMM (Oracle Virtualbox here), and in the “File” menu, select “import
Appliance”.
○ Click “Choose” (a folder icon may also be “Choose”), browse to the location
containing Mininet-VM (the .ovf file you downloaded), and click “Open”, and click
“Continue”.
○ Click “Import” and then select the imported virtual machine
○ Select “Host Network Manager” from the “File” menu
○ Click “Create”, you should see a new network named like “vboxnet0” or similar
○ Click “Enable DHCP” in the “vboxnet0” entry
○ Now go back to main menu, click on the Mininet-VM, click on “Settings”
■ Select “Network” and then set “Attached to” to “Host-only Adapter”
then click “OK”
○ Select the Mininet-VM and click the “Start”
○ Login (or SSH) with
■ mininet-vm login: mininet
■ Password: mininet
○ Additionally, if your VM won’t boot to login, check your BIOS/UEFI settings to
ensure virtualization is enabled. To do this you will need to look up how to access
your bios for your machine. For example, a lenovo laptop can access its bios by
CSCI 4211: Introduction to Computer Networks - Zhi-Li Zhang - Programming Project 3
restarting and hitting enter as soon as the initial boot screen appears and from
there the bios configuration can be accessed.
● Consider Topology A:
○ Is it possible to estimate the throughput and latency between the switches for the
links L1, L2, L3, and L4? If yes, provide the estimated throughput and latency for
each of the links and explain the process used to estimate them in detail. If no,
justify your response with an explanation. Write your answers in a file named
(topology-a-report.txt)
■ Note: To run topology A’s mininet script use the command “sudo python
topology-a.py”
■ Note: The hosts (h1 - h9) are assigned IP addresses 10.0.0.1 through
10.0.0.9 (h1 is 10.0.0.1, h9 is 10.0.0.9).
■ Note: You may use Iperf and Ping to answer these questions
● Create Topology B with Mininet’s Python API (using the skeleton code topology-b.py)
○ Note: Each level (i.e., core, aggregation, edge and host) is composed of a single
layer of switches or hosts. (1:Core to Aggregation ,2:Aggregation to
Edge ,3:Edge to Hosts)
CSCI 4211: Introduction to Computer Networks - Zhi-Li Zhang - Programming Project 3
○ Note: All links between hosts and edge switches will have the same predefined
performance parameter. Here there are 3 types of links, the links between core
and aggregation switches, the links between aggregation and edge switches,
links between edge switches and host. You will see these specific parameters in
the skeleton code (topology-b.py)
● Evaluate Topology B similarly to Topology A (measurements of throughput and latency
for links between switches (example: e1 to a1, a1 to c1)
○ Write your answers in a file named (topology-b-report.txt)
● Create an optimized Ethernet-based self learning algorithm
○ Consider the Topology C:
■ Switch s1 maintains a flow table which contains match-action rules that
are added/removed/updated by the controller. At the beginning, there are
no rules installed in the flow table. When packets are sent by hosts to one
another, the controller extracts information from these packets and builds
certain internal data structures (such as a hashmap, etc.) to represent the
topology. The controller will use these internal data structures to decide
what rules should be installed in the switch’s flow table.
■ As an example, consider host h1 wants to send a packet to h2. When
switch s1 receives this packet from h1, it checks if there is any
corresponding match-action rule (or flow entry) for this packet in its flow
table. If there is no entry, the switch will encapsulate the packet and send
it inside as an OFPacketIn message to the controller c0. On the other
hand, if there is a flow entry, switch s1 will execute the action associated
with the rule. However, as discussed earlier, the flow table is initially
empty. Therefore, the switch will forward the packet to the controller.
When the controller receives the OFPacketIn message from switch s1, a
packet-in event is triggered. Two tasks are performed due to a packet-in
event: 1) using the information from packet headers/event, the controller
may update its internal state (e.g. it learns something new about the
topology), 2) using the internal state, it makes a decision on what
action(s) s1 should take to send this packet to h2. If the controller knows
what interface s1 should forward the packet to, it will inform s1 and also
CSCI 4211: Introduction to Computer Networks - Zhi-Li Zhang - Programming Project 3
install a flow entry which could be used for future packet transmissions of
similar kind. If the controller does not know what interface s1 should
forward to, then it will instruct the switch to flood the packet to all the
interfaces except the one. This flooding instruction is a one-time action
without installing any rules in the switch.
○ Try to come up with an Ethernet-based self learning algorithm at the controller
that does not unnecessarily flood packets while learning the topology.
■ Hint: Try to test your algorithm under multiple scenarios such that the
controller is able to learn the whole topology quickly without unnecessarily
flooding packets. For example, one such scenario could be h1 sends a
packet to h2, then h2 sends a packet to h1, then h3 sends a packet to
h1. Another direction to think about is if your algorithm should be source-
based, destination-based, or a combination of multiple packet header
fields.
■ Write this in your submission following the “What to Submit” guidelines
○ Implement your algorithm (using the skeleton code ethernet-learning.py or
EthernetLearning.java you decide which)
○ Test your algorithm using POX (Python) or Floodlight (Java):
■ Against Topology A
● Comment out the line “net = Mininet(topo=topo, link=TCLink,
autoSetMacs=True,autoStaticArp=True)” and uncomment the
line “#net = Mininet(controller=RemoteController, topo=topo,
link=TCLink, autoSetMacs=True,autoStaticArp=True)”. This will
allow the topology to connect to your controller.
● Ping and Iperf (you should see latencies and throughputs similar
to what is defined for each link)
● Make sure that each host can reach each other
■ Against Topology B
● Comment out the line “net = Mininet(topo=topo, link=TCLink,
autoSetMacs=True,autoStaticArp=True)” and uncomment the
line “#net = Mininet(controller=RemoteController, topo=topo,
link=TCLink, autoSetMacs=True,autoStaticArp=True)”. This will
allow the topology to connect to your controller.
● Ping and Iperf (you should see latencies and throughputs similar
to what is defined for each link)
● Make sure that each host can reach each other
■ Note: When you start your topology (using the python) it will connect to
this controller, so run your controller first, then run the target topology
■ Note: To run your controller with POX:
● Put ethernet-learning.py file in the directory pox/pox/samples. You
will then run the controller and your module using the following
commands:
○ you@yourmachine$ cd pox
○ you@yourmachine$ ./pox.py samples.ethernet-learning
CSCI 4211: Introduction to Computer Networks - Zhi-Li Zhang - Programming Project 3
■ Note: To run your controller with Floodlight:
● This is a more involved process:
○ You may have to follow pre-req instructions for modifying
the VM
● Put EthernetLearning.java file in
src/main/java/net/floodlightcontroller/ethernetlearning/ .
● We need to tell Floodlight to load the module on startup. First we
have to tell the loader that the module exists. This is done by
adding the fully qualified module name on it’s own line in
src/main/resources/META-INF/services/net.floodlightcontroller.cor
e.module.IFloodlightModule. We open that file and append this
line to the file:
net.floodlightcontroller.ethernetlearning.EthernetLearning Then we
tell the module to be loaded. We modify the Floodlight module
configuration file to append the EthernetLearning module. The
default one is src/main/resources/floodlightdefault.properties. The
key is floodlight.modules and the value is a comma separated list
of fully qualified module names.floodlight.modules = default list of modules in place>,
net.floodlightcontroller.ethernetlearning.EthernetLearning
● Proceed with re-building the controller using:
○ you@yourmachine$ cd floodlight/target
○ you@yourmachine$ ant
● Finally, run the controller by using the floodlight.jar file produced
by ant from within the floodlight directory:
○ you@yourmachine$ java -jar target/floodlight.jar
● Floodlight will start running and print log and debug output to your
console
■ Note: Your code will be executed to show it can properly map out the
topology, eg: all hosts reachable to each other via appropriate paths
What To Submit:
● A zip file (.tar.xz or .zip formats), named as --project3.zip
(or .tar.xz) (example: Boberson-Alice-project3.tar.xz for single submission, Boberson-
Alice-Bobserson-John-project3.tar.xz for multiple teammembers), to the class canvas
site containing:
○ The evaluation report for Topology A (as topology-a-report.txt)
○ Your Topology B code (as topology-b.py)
○ The evaluation report for Topology B (as topology-b-report.txt)
○ A readme file (as README.md using Markdown syntax) with sections:
■ A header
● ,Zhang CSCI4211,(day/month/year)>
CSCI 4211: Introduction to Computer Networks - Zhi-Li Zhang - Programming Project 3
● Ex: Marky Markdowns,Zhang CSCI4211,31/12/1969
■ An “Ethernet-Algorithm” section that describes at a high level your
Ethernet-based self learning algorithm
● Including detailed explanations of your data structures and their
purposes
■ A “Pseudocode” section describing your algorithm following Pseudocode
guidelines
■ (optional) A(n) comments/assumption section
○ Your Ethernet-based self-learning algorithm code (ethernet-learning.py or
EthernetLearning.java)

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