3. Model the network topology below using python and capture ECHO packets transmitted from N7 to N4 and Analyze using Wireshark N2 N3 N4 (NO N1 1 10.1.1.0/24 N5 10.1.2.0/24 ECHO 10.1.3.0/24 N6 N7 4. Create a simple dumbbell topology , two client Nodel and Node2 on the left side of the dumbbell and server nodes Node3 and Node4 on the right side of the dumbbell . Let Node5 and Node6 form the bridge of the dumbbell . Use point -to-point links a. Install a TCP socket instance on Nodel that will connect to Node3 b. Install a UDP socket instance on Node2 that will connect to Node4 . c. Start the TCP application at time Is . d. Start the UDP application at time 20s at rate Ratel such that it clogs half the dumbbell bridge's link capacity e . Increase the UDP application's rate at time 30s to rate Rate2 such that it clogs the whole of the dumbbell bridge's capacity f. Use the ns-3 tracing mechanism to record changes in congestion window size of the ICP instance over time . Use gnuplot /matplotlib to visualise plots of cwnd vs time g. Mark points of fast recovery and slow start in the graphs h . Perform the above experiment for TCP variants Tahoe , Reno and New Reno , all of which are available with ns-3