## 5 Performance Evaluation
### Performance Evaluation  
#### 5.2.1 Pipeline Influence on Forwarding Performance  
Figure 6 shows the influence of continuous interest messages sent by edge nodes through pipelines on the network download performance. In order to prevent DDoS attacks, all concurrent interest messages are aggregated as one piece of interest in the PIT of the intermediate router within the retransmission suppression time range set by the exponential backoff algorithm in MIN-IIoT, because they carry the same content name. Only one request message will be forwarded, and the others will be discarded.  
The NDN-BestRoute scheme does not support concurrent requests from different users. It only requests original data packets along the path with the lowest forwarding cost, without distinguishing interest requests from different downstream nodes. Therefore, we would not choose NDN-BestRoute as a reference for comparison. With the increase in concurrency, the transmission delay of NDN-Multicast decreases quickly (from 290 ms to 174 ms), and then increases slowly (from 174 ms to 219 ms). With the gradual increase in concurrency, the number of previous request packets in the network will gradually increase, thus accelerating the content requests. However, when the concurrency exceeds 10, concurrent requests from the same requester and parallel ones from different requesters will be challenging to coordinate on the bottleneck link (router 3 to router 2), and congestion will occur. Generally speaking, slow interest requests can cause the network to become  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Value Range** & **Default Value** \\ \hline Connection bandwidth & 2–10 Mbps & 10 Mbps \\ Transmission delay & 1 ms & 1 ms \\ Number of content segments & 100 & 100 \\ Number of encoded blocks per & 100 & 100 \\ segment size & 5 KB & 5 KB \\ Finite field & \(F_{\mu\mu}\) & \(F_{\mu\mu}\) \\ Zipf & 0.6–1.6 & 0.8 \\ Cache size (proportion of total content) & 0.05–0.25 & 0.1 \\ Pipeline number (pcs/s) & 1–25 & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Emulation parameters.  
Figure 6: Influence of continuous interest requests on content download time.  
idle, while frequent interest requests can lead to congestion. It is necessary to wait for the network to respond and deal with the interest sent before.  
In contrast, the access latency of the NetCodCCN and IDEANE schemes using network coding will not be significantly affected by the number of concurrent requests. Both of them request encoded blocks, which can eliminate the possibility of asking for the same content block on the bottleneck link. When the amount of concurrency is small, these two methods will take time to process the received encoded blocks, so the initial transmission delay is worse than that of NDN-Multicast. At the same time, they show a slight upward trend after a significant decline. The average transmission delay of IDEANE is 16.5% less than that of NetCodCCN. IDEANE only performs linear independent verification of the encoded vectors at the intermediate node, without secondary encoding and decoding. At the same time, NetCodCCN does not deal with the linear correlation of the encoded blocks and requires secondary coding at the intermediate nodes. Therefore, there will be linearly dependent encoded blocks, and it is necessary to reapply for linearly independent ones. Therefore, IDEANE can reduce the delay in network requests and achieve better results than NetCodCCN. In the next experiment, we choose the concurrent interest message with the best NDN-Multicast performance, and the number of pipeline requests is 10 per second.