2023/4/29 15:43 NDM Lab 2: NS2 Simulation

M1 – Sorbonne Université Network Design and Modeling

Lab II: Implementation of a simulation model and its application

In this second Lab, you will study a simple network with multi-routes. You will use the manual routing in order to simulate a model of the studied network.

IMPORTANT. At the end of this part of the lab (03:45pm), you must send a first version of your lab report. This first version will include the tcl script of the simulation and some texts that explain the solution you implemented in the script to simulate the required topology and network parameters, plus the result of one simulation run. (No final report for this part of the lab. It will be required later in conjunction with lab II followup report.)

A network with multi-routes and losses

The network to study is composed by 4 nodes, and 4 links. Packets of 1000 bytes are generated by a Poisson source at node 0. The sending rate is b in kbits. The destination of these packets is node 3 (see the figure below). 1⁄4 of the traffic is routed through node 2. Links 1-2 and 2-3 may drop packets with the probability p (Uniform losses). All queues are FIFO. In addition, we assume that the application at node 3 cannot support more than 64 packets per second. We would like to study the maximum performance of the network as a function of b and p.

  1)

Complete the TCL script lab2.tcl in order to create a simulation model of the above network for ns2 so that you generate both trace and nam files. We assume that DropTail queues are of “infinite” size and that the propagation delay over all links is negligible.

Note 1: ns2 do not support probabilistic routing. However, you can implement a solution using manual routing (See slides 19, 20, 13 and 11) and using the fact that the aggregation of two Poisson processes is also a Poisson process with a rate parameter equals to the sum of the two rate parameters of the aggregated Poisson processes.

Note 2 : The network used in the simulation model does not correspond necessarily to the real network to study. You can add nodes and/or links in order to simulate the 64 packets/s constraint of the application.

Once your tcl code is ready, run one simulation and check globally the correctness of the simulation by looking at the trace file and the nam animation. In order to find the required TCL code to create the nam trace file, see the previous lab tcl code.

To be continued

   These two above notes indicate that what you simulate can be different from the real system you want to evaluate as long as the simulation results provide the performance that you would measure in the real system.

General rule: Do not try to simulate everything from the system you want to evaluate. Implement in the simulator only the minimum required to be able to compute the target performance metrics.

 https://www-npa.lip6.fr/~malouch/M1/SDMp2/lab2.htm

1/1