Figure 10: The multi-hop network topology for multi-path simulations. Each of
the intermediate nodes N1 through N6 has a number of TCP data sources
attached.
We simulate sending two CBR voice streams from source to destination over two independent paths, with TCP data traffic contending for network resources at the same time. The topology used in ns simulator is shown in Fig. 10. Each CBR stream is transmitted in 30 ms UDP packets at the rate of 48 kbps. The first stream flows over nodes from N1 through N3 to the destination; while stream 2 goes through N4 to N6 to the destination. Intermediate nodes N1 through N6 present access points on the routes, which are abstract of sources of data traffic. Each of these node has a number of data sources attached, with a large amount of incoming TCP traffic heading for different destinations.
We use log-normal model proposed in [2] for the file sizes of TCP traffic. The load of data traffic is controlled by the intermission between successive TCP transmissions, which varies in our simulation.
In the simulations all links have 10Mbps bandwidth and introduce 20 ms propagation delay (which will be varied in later simulations), and the buffer size of the switches is 100 kbyte per port. Each simulation runs for 300 seconds, and QoS parameters are monitored from end to end.