Computer Network 7｜Implement MiniNet

The following instructions is based on MacOS with Apple silicon chip (M1/M2). The used VM software is VMware and Virtual Code Studio is required.

1. VM Setup

Register on VMware
Download: VMware Fusion Player 13 – Personal Use (VMware Fusion 13.0.1 (for Intel-based and Apple silicon Macs) https://customerconnect.vmware.com/en/evalcenter?p=fusion-player-personal-13
Select personal use for a free license
Download from one of the following links for the latest VM image
- Dropbox Link
- Onedrive Link
Run image with the VMware installed

2. Basic Test

Login to VM with the following information:
- username: mininet
- password: mininet
Then open a QTerminal (terminal emulator) window for testing

$ sudo su -      # for root permission
[sudo] password for mininet: mininet

Finally, test mininet installed

% mn
*** Creating network
...
exit

3. IDE Setup

Open VSCode with Remote-SSH extension
Go to VM terminal and check for the ip address. Check the IP address (inet) under ens160. For me, it is 192.168.80.129.

$ ifconfig
ens160:
    ...
    inet ...
    ...

Connect to the host -> add a new host, then enter the following command

ssh mininet@192.168.80.129

Use the default config and connect. Enter the password mininet when required.
Wait to be connected. Then we can use VSCode to edit.

4. Mininet Introduction

Github Source: https://github.com/mininet/mininet
Offical webpage: https://mininet.org/
Beginner Guide: http://mininet.org/walkthrough/#interact-with-hosts-and-switches

Here are some common commands,

help – shows all commands
nodes – displays all nodes including the controller c0
net – displays all nodes and links in an extended format
links – brief display of links
dump – displays full network information
$mn –c cleans the Mininet environment after topology runs.

5. Useful Sources

Network topology visualizer for complextopo.py and datacenter.py (will discuss later): http://demo.spear.narmox.com/app/?apiurl=demo#!/mininet

6. Project Setup

Make Assignment directory

$ mkdir /home/mininet/Assignments

Then use VSCode to go into this folder and copy the starter code from unzipping SimulatingNetworks.zip downloaded from Canvas
Go to the folder

$ cd /home/mininet/Assignments/SimulatingNetworks

Time to start!

Note: you can also setup git/github for your working directory before you start.

7. Part 2 - Modifications

If you can successfully execute the program topology.sh, feel free to skip the following discussions.

Because I downloaded the VM image through the first link and it is not perfect, we have to make some change when we are running Part 2.

Inside the SimulatingNetworks folder, change the permission by,

$ chmod -R 755 ./topology.sh

Also install bwn-ng by,

$ apt-get install bwm-ng

Then bypass the cgroups issue by adding the following line in /etc/fstab,

cgroup /sys/fs/cgroup cgroup defaults,blkio,net_cls,freezer,devices,cpuacct,cpu,cpuset,memory,clone_children 0 0

Also, add the following line in /etc/default/grub,

GRUB_CMDLINE_LINUX_DEFAULT="quiet cgroup_enable=memory,namespace systemd.unified_cgroup_hierarchy=0" 

Then update grub with,

$ update-grub

And reboot the VM,

$ reboot

Once back, rerun ./topology.sh then we are able to execute. However, after a couple seconds, we will receive a matplotlib error.

Then we add the following line at the top of the util/helper.py file

#! sh/bin/env python

And we should also install matplotlib by,

$ pip3 install matplotlib

After this, if we run ./topology.sh again, it will pass without any further errors.

8. Part 2

After running ./topology.sh, we generate the following two figures in the output folder,

cwnd: shows a TCP cubic pattern
bandwidth: shows a rate of about 10 Mbps

The topology here we used is defined in mntopo.py with 2 hosts, 2 links, and 1 switch.

Task 1: Modify the mntopo.py so that it represent the following topology. Rerun ./topology.sh to get the result. Remember to clean the mininet files by mn -c.

After execution, we have a similar because our topology map doesn’t have much difference.

Next, let’s test the latency of the current topo. First let’s run python ./ping.py for the initial bench mark as,

$ python ./ping.py
PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
64 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=19.4 ms
64 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=9.55 ms
64 bytes from 10.0.0.1: icmp_seq=3 ttl=64 time=8.70 ms
64 bytes from 10.0.0.1: icmp_seq=4 ttl=64 time=8.85 ms
64 bytes from 10.0.0.1: icmp_seq=5 ttl=64 time=8.82 ms

--- 10.0.0.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4006ms
rtt min/avg/max/mdev = 8.697/11.063/19.389/4.173 ms

Task 2: Modify linkConfig.delay in mntopo.py to 10ms, then rerun python ./ping.py to compare the result.

The possible result is,

$ python ./ping.py
PING 10.0.0.1 (10.0.0.1) 56(84) bytes of data.
64 bytes from 10.0.0.1: icmp_seq=1 ttl=64 time=166 ms
64 bytes from 10.0.0.1: icmp_seq=2 ttl=64 time=85.5 ms
64 bytes from 10.0.0.1: icmp_seq=3 ttl=64 time=81.7 ms
64 bytes from 10.0.0.1: icmp_seq=4 ttl=64 time=81.8 ms
64 bytes from 10.0.0.1: icmp_seq=5 ttl=64 time=81.5 ms

--- 10.0.0.1 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4007ms
rtt min/avg/max/mdev = 81.537/99.397/166.426/33.546 ms

Here we say see pings just a bit over 80 ms compared with 10 ms initially.

Task 3: Adjust bandwidth linkConfig.bw to 50 Mbps per second. Rerun ./topology.sh to get the result. Remember to clean the mininet files by mn -c.

The result should be,

Task 4: Create a new topology representing a more complicated network topology in complextopo.py.

The parameters should be set as follows,

Ethernet: Bandwidth 25 Mbps, Delay 2 ms, and loss rate 0%
WiFi: Bandwidth 10 Mbps, Delay 6 ms, and loss rate 3%
3G: Bandwidth 3 Mbps, Delay 10 ms, and loss rate 8%

Also, do not specify ports (use the default ones) in this task.

9. Part 3

Now that we have implemented complextopo.py so it’s the right time to test it out. We run cli.py to start the simulation.

$ python ./cli.py

After Mininet loads the complex topology, you should see the Mininet command prompt: mininet>.

Then we can test the following command,

mininet> h1 ping h2 -c 10

This means to let h1 to ping h2 for 10 times. If everything works well, we can expect something like,

PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
bytes from 10.0.0.2: icmp_seq=1 ttl=64 time=1087 ms
bytes from 10.0.0.2: icmp_seq=2 ttl=64 time=57.8 ms
bytes from 10.0.0.2: icmp_seq=3 ttl=64 time=27.7 ms
bytes from 10.0.0.2: icmp_seq=4 ttl=64 time=26.9 ms
bytes from 10.0.0.2: icmp_seq=5 ttl=64 time=25.1 ms
bytes from 10.0.0.2: icmp_seq=6 ttl=64 time=25.8 ms
bytes from 10.0.0.2: icmp_seq=7 ttl=64 time=26.2 ms
bytes from 10.0.0.2: icmp_seq=8 ttl=64 time=25.2 ms
bytes from 10.0.0.2: icmp_seq=9 ttl=64 time=25.1 ms
bytes from 10.0.0.2: icmp_seq=10 ttl=64 time=25.4 ms

--- 10.0.0.2 ping statistics ---
packets transmitted, 10 received, 0% packet loss, time 9039ms
rtt min/avg/max/mdev = 25.064/135.192/1086.846/317.361 ms, pipe 2

Task 1: Test ping from h1 to h2 and h3 for 100 times each. Compare the difference of the results.

h1 to h2: delay 20 ms with 4% packet loss
h1 to h3: delay 30 ms with 10% packet loss

This follows the topology we have built.

Tasl 2: Use mininet> pingall to ping between each pair of hosts.

If success, we should expect something like,

mininet> pingall
...
h1 -> h2 h3
h2 -> h1 h3
h3 -> h1 h2
*** Results: 0% dropped (6/6 received)

Note that there can be X in the result meaning the one link is not pingable. If this happens, please rerun pingall to confirm.

10. Part 4

In this part, we are going to implement a fan-in style data center. It has three layers of switch,

tls: top-level switch
mls: mid-level switches
rs: rack switches, these connct to the hosts

The network should have the following two arguments,

fi: fin-in rate, wich is the ratio of,
- the # of mls / the # of tls
- the # of rs / the # of mls
n: number of hosts connected to each rack switch

For example,

The code should be implemented based on datacenter.py using loops. And the naming conventions should follow,

tls: tls1
mls: mls1, mls2, to mlsfi
rs: s1x1, s1x2… to sfixfi
hosts: h1x1x1, h1x1x2, to hfixfixn

For testing, we can run,

$ python datacenter.py --fi 2 --n 5

Then run pingall when we are in the Mininet prompt. We can expect this result if everything works well.

11. Submission

To submit, use the following command to zip the file.

$ zip -r <gtid>_sn.zip . -x '.*' -x '__MACOSX' 