# Search of the Shortest Path in a Communication Network with Fuzzy Cost Functions
## 6 Experimentation and Results  
### Description of the Experiment  
In this work, the simulator OMNET ++ [31] is used for the experimentation. The code used for the experiment and the configuration files can be downloaded from [32]. A flow-oriented simulation is performed to reduce the execution time of each simulation  
Figure 4: WS applied to a 9-node network with explicit Mean Residual Bandwidth in every link. (the alternative packet-oriented simulation would require an execution time in the order of thousand times greater). In our study, a 57-node and a 12-node networks were used. The first one is based on the topology of the backbone network of the Nippon Telegraph and Telephone (NTT). This topology has been extensively used in the related literature such as in [33]. The particular characteristics of our implementation can be found in the examples of the use of the OMNeT ++ simulator [31] (Figure 5). The second one is based on the topology of the National Science Foundation's Network (NFSNET) (Figure 6) [34]. This network is obsolete today, but it has been used extensively in the study of routing protocols. Our data loss model simulates an optical burst switching network (OBS) without storage. If a burst does not have enough bandwidth on a link, the information is discarded (that is, the information is lost) until there are enough resources. When there are not enough resources at any time during the burst lifetime, the complete burst is discarded. The model and source code required to carry out these simulations are found in [32]. To facilitate the reproduction of the experiments, we have carried out ten simulations with different seeds for each of the different strategies, where every node generates traffic with the same probability. We have adjusted the traffic in both networks to work in a close saturation mode, because we want to study the performance of the different strategies under these conditions. With low saturation, all the strategies can deliver the traffic successfully, and in high saturation conditions, the percentage of losses impacts on the network performance. Tables 1 and 2 indicate the features of the traffic used for the first and second network topologies, respectively. Figure 5: First topology used in our experiments, based on the backbone network of the Nippon Telegraph and Telephone (NTT). Figure 6: Second topology used in our experiments, based on the backbone network of NFSNET network. Each parameter characterizing the traffic is described next:  
_Call rate_: Mean number of connections requests. _Call duration_: Interval of time at which the connection is active once it is established. _Type of traffic_: Data are transmitted for a specific time (burst with constant bandwidth) and they are not transmitted for another time interval. _Used Bandwidth over an ON period_: Resources required for a connection over an ON period. Since we are considering an ON period of 5 s and an OFF period of 1 s, the _Mean Used Bandwidth_ for a connection is 25 Mb/s, that is, approximately, the Used Bandwidth of an Advanced Video Coding High Definition (AVCHD) connection. We use this value in order to work in conditions of saturation. _ON period_: Transmission period. It is modeled by a random distribution. In our case we use an exponential distribution with a mean of 5 s. \begin{table}
\begin{tabular}{l l} \hline \hline
**Description of the Parameters** & **Value** \\ \hline Call rate & Poisson Distribution with mean value \\  & 0.5 Calls/s \\ \hline Call duration & Exponential Distribution with mean value \(\mu=120\) s \\ \hline Type of traffic & ON/OFF \\ \hline Used Bandwidth over an ON period & 30 Mbit/s \\ \hline ON period & Exponential Distribution with mean value \(\mu=5\) s \\ \hline OFF period & Exponential Distribution with mean value \(\mu=1\) s \\ \hline Connection type & Symmetrical and bidirectional \\ \hline Simulation time & 10,000 s \\ \hline Interval of time to update routing tables & 300 s \\ \hline Number of replications with different seeds & 10 \\ \hline \hline \end{tabular}
\end{table}