(Solved Homework): You are a network engineer responsible for creating the following network and testing it in your lab before your…

In datagram forwarding this is achieved by providing each switch with a forwarding table of (destination,next_hop) pairs. When a packet arrives, the switch looks up the destination address (presumed globally unique) in its forwarding table and finds the next_hop information: the immediate-neighbor address to which – or interface by which – the packet should be forwarded in order to bring it one step closer to its final destination. The next_hop value in a forwarding table is a single entry; each switch is responsible for only one step in the packet’s path. However, if all is well, the network of switches will be able to deliver the packet, one hop at a time, to its ultimate destination.

rom mininet.topo import Topo
from mininet.net import Mininet
from mininet.node import CPULimitedHost
from mininet.link import TCLink
from mininet.util import irange,dumpNodeConnections
from mininet.log import setLogLevel

class LinearTopo(Topo):
   "Linear topology of k switches, with one host per switch."

   def __init__(self, k=2, **opts):
       """Init.
           k: number of switches (and hosts)
           hconf: host configuration options
           lconf: link configuration options"""

       super(LinearTopo, self).__init__(**opts)

       self.k = k

       lastSwitch = None
       for i in irange(1, k):
           host = self.addHost('h%s' % i, cpu=.5/k)
           switch = self.addSwitch('s%s' % i)
           # 10 Mbps, 5ms delay, 1% loss, 1000 packet queue
           self.addLink( host, switch, bw=10, delay='5ms', loss=1, max_queue_size=1000, use_htb=True)
           if lastSwitch:
               self.addLink(switch, lastSwitch, bw=10, delay='5ms', loss=1, max_queue_size=1000, use_htb=True)
           lastSwitch = switch

def perfTest():
   "Create network and run simple performance test"
   topo = LinearTopo(k=4)
   net = Mininet(topo=topo, 
                 host=CPULimitedHost, link=TCLink)
   net.start()
   print "Dumping host connections"
   dumpNodeConnections(net.hosts)
   print "Testing network connectivity"
   net.pingAll()
   print "Testing bandwidth between h1 and h4"
   h1, h4 = net.get('h1', 'h4')
   net.iperf((h1, h4))
   net.stop()

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