Friday, June 14, 2019

Mininet flow analytics with custom scripts

Mininet flow analytics describes how to use the sflow.py helper script that ships with the sFlow-RT analytics engine to enable sFlow telemetry, e.g.
sudo mn --custom sflow-rt/extras/sflow.py --link tc,bw=10 \
--topo tree,depth=2,fanout=2
Mininet, ONOS, and segment routing provides an example using a Custom Topology, e.g.
sudo env ONOS=10.0.0.73 mn --custom sr.py,sflow-rt/extras/sflow.py \
--link tc,bw=10 --topo=sr '--controller=remote,ip=$ONOS,port=6653'
This article describes how to incorporate sFlow monitoring in a fully custom Mininet script. Consider the following simpletest.py script based on Working with Mininet:
#!/usr/bin/python                                                                            
                                                                                             
from mininet.topo import Topo
from mininet.net import Mininet
from mininet.util import dumpNodeConnections
from mininet.log import setLogLevel

class SingleSwitchTopo(Topo):
    "Single switch connected to n hosts."
    def build(self, n=2):
        switch = self.addSwitch('s1')
        # Python's range(N) generates 0..N-1
        for h in range(n):
            host = self.addHost('h%s' % (h + 1))
            self.addLink(host, switch)

def simpleTest():
    "Create and test a simple network"
    topo = SingleSwitchTopo(n=4)
    net = Mininet(topo)
    net.start()
    print "Dumping host connections"
    dumpNodeConnections(net.hosts)
    print "Testing bandwidth between h1 and h4"
    h1, h4 = net.get( 'h1', 'h4' )
    net.iperf( (h1, h4) )
    net.stop()

if __name__ == '__main__':
    # Tell mininet to print useful information
    setLogLevel('info')
    simpleTest()
Add the highlighted lines to incorporate sFlow telemetry:
#!/usr/bin/python                                                                            
                                                                                             
from mininet.topo import Topo
from mininet.net import Mininet
from mininet.util import dumpNodeConnections
from mininet.log import setLogLevel
from mininet.util import customClass
from mininet.link import TCLink

# Compile and run sFlow helper script
# - configures sFlow on OVS
# - posts topology to sFlow-RT
execfile('sflow-rt/extras/sflow.py') 

# Rate limit links to 10Mbps
link = customClass({'tc':TCLink}, 'tc,bw=10')

class SingleSwitchTopo(Topo):
    "Single switch connected to n hosts."
    def build(self, n=2):
        switch = self.addSwitch('s1')
        # Python's range(N) generates 0..N-1
        for h in range(n):
            host = self.addHost('h%s' % (h + 1))
            self.addLink(host, switch)

def simpleTest():
    "Create and test a simple network"
    topo = SingleSwitchTopo(n=4)
    net = Mininet(topo,link=link)
    net.start()
    print "Dumping host connections"
    dumpNodeConnections(net.hosts)
    print "Testing bandwidth between h1 and h4"
    h1, h4 = net.get( 'h1', 'h4' )
    net.iperf( (h1, h4) )
    net.stop()

if __name__ == '__main__':
    # Tell mininet to print useful information
    setLogLevel('info')
    simpleTest()
When running the script the highlighted output confirms that sFlow has been enabled and the topology has been posted to sFlow-RT:
pp@mininet:~$ sudo ./simpletest.py
*** Creating network
*** Adding controller
*** Adding hosts:
h1 h2 h3 h4 
*** Adding switches:
s1 
*** Adding links:
(10.00Mbit) (10.00Mbit) (h1, s1) (10.00Mbit) (10.00Mbit) (h2, s1) (10.00Mbit) (10.00Mbit) (h3, s1) (10.00Mbit) (10.00Mbit) (h4, s1) 
*** Configuring hosts
h1 h2 h3 h4 
*** Starting controller
c0 
*** Starting 1 switches
s1 ...(10.00Mbit) (10.00Mbit) (10.00Mbit) (10.00Mbit) 
*** Enabling sFlow:
s1
*** Sending topology
Dumping host connections
h1 h1-eth0:s1-eth1
h2 h2-eth0:s1-eth2
h3 h3-eth0:s1-eth3
h4 h4-eth0:s1-eth4
Testing bandwidth between h1 and h4
*** Iperf: testing TCP bandwidth between h1 and h4 
*** Results: ['6.32 Mbits/sec', '6.55 Mbits/sec']
*** Stopping 1 controllers
c0 
*** Stopping 4 links
....
*** Stopping 1 switches
s1 
*** Stopping 4 hosts
h1 h2 h3 h4 
*** Done
Mininet dashboard and Mininet weathermap describe the sFlow-RT Mininet Dashboard application shown at the top of this article. The tool provides a real-time visualization of traffic flowing over the Mininet network. Writing Applications describes how to develop custom analytics applications for sFlow-RT.

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