# Comparative Analysis of Producer Mobility Management Approaches in Named Data Networking
## 4 Simulation Set-Up and Evaluation Metrics
### Evaluation Metrics  
To evaluate the performance of the different MM schemes, several evaluation metrics which measured their effectiveness from different perspectives were used. We explain the evaluation metrics next. * Average Data Packet Retrieval Delay  
The data packet retrieval delay is the time delay between the consumer issuing the interest packet and the arrival of the requested data packet to the consumer. This delay is measured for each associated interest-data pair and then averaged over the total number of received data packets. Shorter delays indicate faster handoff management of the MM scheme because the route to the mobile producer was re-established successfully in shorter time. The data retrieval delay obviously affects the QoS perceived by the consumer application and should be minimized as much as possible. * Average Hop Count  
The ratio between the optimum potential path through the network and the actual path taken by traffic is known as the path stretch. The optimal path is the shortest possible path between two nodes in the network (the producer and the consumer in our case). The hop count represents the path length and is measured by the average number of (router) hops a data packet traverses from the producer to the consumer. After producer mobility, an effective MM scheme would assure reachability to the mobile producer by a path that has a low stretch. We used the average hop count as one of the metrics to assess the performance of an MM scheme, as it is an important metric and has a direct impact on other evaluation metrics, such as the delay. Specifically, a certain delay in data delivery may result from the increase in the path length caused by the underlying MM scheme. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Category** & **Parameters** & **Value** \\ \hline \multirow{4}{*}{Mobility} & Mobility model & Random waypoint \\  & Number of producer & 5 \\  & Number of consumers & 5 \\ \hline \multirow{4}{*}{NDN} & Streaming rate & 1 Mbps \\  & Packet size & 1024 bytes \\  & Request rate & 128 request/s \\  & Application & Streaming audio or video \\ \hline \multirow{4}{*}{Network} & 4 \(\times\) 4 fat tree & 80 \(\times\) 80 m cell size \\  & Link delay & 5 ms \\  & Bandwidth & 10 Mbps \\ \hline \multirow{2}{*}{Set-up} & Simulation duration & 3000 s \\  & Warm-up duration & 100 s \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Simulation parameters. Figure 6: Layout of base stations. * Data Loss Rate  
The streaming producers generated data packets with a constant rate, such as 128 packets per second. A data packet that was generated but did not arrive at its requesting consumer was considered a lost data packet. The data loss rate is then the number of data packets that have not arrived at their requesting consumers over the total number of data packets sent by the producers. Packet loss is the number of unfulfilled interest packets, which in the simulation was equivalent to the number of interest packet retransmissions. A packet may be lost due to either producer mobility, network congestion, or wireless collisions. Due to producer mobility, some interest packets may not find the mobile producer, because the FIB tables may lead interest packets to the old location of the producer. A producer MM scheme should react to producer mobility promptly and update the network to make the mobile producer reachable. Fast reachability of a mobile producer guarantees replying with the requested data packet and thus reducing packet loss. * Signaling Overhead  
This is the additional signaling packets per handoff required by the MM scheme to complete its operations. Although the signaling overhead does not really describe the effectiveness and efficiency of an MM scheme, it should be rather minimized to better utilize the network resources. What is more, the signaling overhead may sometimes have an inverse relationship with other evaluation metrics.