3. Use the command line of Mininet to generate the following topology: a) 3 switches, each switch is connected to a host, and the 3 switches are connected into a line.

4. On the basis of 2b), add a new host on the Mininet interactive interface and connect it to the switch, and then test the connectivity of the new topology.

5. Edit the Python script saved in step 1 of the basic requirements, add the following network performance constraints, and generate the topology:
a) The maximum cpu of h1 does not exceed 50%;
b) The link bandwidth between h1 and s1 is 10, the delay is 5ms, the maximum queue size is 1000, and the loss rate is 50.

#!/usr/bin/env python

from mininet.net import Mininet
from mininet.node import Controller, RemoteController, OVSController
from mininet.node import CPULimitedHost, Host, Node
from mininet.node import OVSKernelSwitch, UserSwitch
from mininet.node import IVSSwitch
from mininet.cli import CLI
from mininet.log import setLogLevel, info
from mininet.link import TCLink, Intf
from subprocess import call

def myNetwork():

    net = Mininet( topo=None,
                   build=False,
                   ipBase='10.0.0.0/8')

    info( '*** Adding controller\n' )
    c0=net.addController(name='c0',
                      controller=Controller,
                      protocol='tcp',
                      port=6633)

    info( '*** Add switches\n')
    s2 = net.addSwitch('s2', cls=OVSKernelSwitch)
    s1 = net.addSwitch('s1', cls=OVSKernelSwitch)

    info( '*** Add hosts\n')
    h4 = net.addHost('h4', cls=Host, ip='10.0.0.4', defaultRoute=None)
    h3 = net.addHost('h3', cls=Host, ip='10.0.0.3', defaultRoute=None)
    h1 = net.addHost('h1', cls=Host, ip='10.0.0.1', defaultRoute=None,cpu=0.5)
    h2 = net.addHost('h2', cls=Host, ip='10.0.0.2', defaultRoute=None)

    info( '*** Add links\n')
    net.addLink(h1, s1,bw=10,delay='5ms',max_queue_size=1000,loss=50,use_htb=True)
    net.addLink(h2, s1)
    net.addLink(s1, s2)
    net.addLink(s2, h3)
    net.addLink(s2, h4)

    info( '*** Starting network\n')
    net.build()
    info( '*** Starting controllers\n')
    for controller in net.controllers:
        controller.start()

    info( '*** Starting switches\n')
    net.get('s2').start([])
    net.get('s1').start([c0])

    info( '*** Post configure switches and hosts\n')

    CLI(net)
    net.stop()

if __name__ == '__main__':
    setLogLevel( 'info' )
    myNetwork()

(2) Advanced requirements

Write a Python script to generate the following data center network topology, which requires:

• Write a .py topology file and name it "student number_fattree.py";

• The above file must be loaded through the custom parameter of Mininet, and the .py file generated by miniedit.py cannot be used directly;

• The device name must be consistent with the following figure;

• It is implemented using Python's loop function, and devices and links must not be added directly in the code.
  

4. Personal summary:

• In this experiment, I feel that I still have a lot of inexperience in the operation of mininet. I often type wrong commands, and my understanding of the experiment is not thorough enough. I need to strengthen my study.