# A Single-Rate Multicast Congestion Control (SRMCC) Mechanism in Information-Centric Networking
## 4 Rate Adaptation
### Rate Selection Strategy
Note that since we considered a hybrid network of IP and ICN and the entire network consisted of ICN routers and IP routers, TCP was the traffic in the network that could not be ignored. To compare performance with other mechanisms and evaluate the friendliness of these mechanisms to TCP, we introduced TCP as the primary competitive traffic. Additionally, Table 1 shows the experiment parameters and their values for our simulation. ### Basic Performance of SRMCC

#### 5.2.1 Experiments on the Setting of Value \(\gamma\)

We performed a series of experiments to explore the effect of parameter \(\gamma\) on SRMCC performance in the first three scenarios. Figure 5a represents the ratio of the multicast throughput to TCP throughput under different rate selection factors \(\gamma\), and Figure 5b represents the packet loss rate of multicast traffic under different rate selection factors \(\gamma\). As shown in Figure 5, as the value of \(\gamma\) increases, both the throughput ratio of multicast traffic using SRMCC to TCP traffic and the packet loss rate are on the rise. Figure 5 shows that SRMCC can achieve good performance in a relatively wide range of \(\gamma\). In particular, when \(\gamma=0.15\), the throughput ratio is closest to 1 and the packet loss rate is equal to or close to 0, which can simultaneously achieve optimal performances when it comes to TCP friendliness and packet loss rate. Therefore, we set \(\gamma\) to 0.15 in our experiments. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline The maximum queue length (\(Q_{max}\)) & 50 packets \\ The threshold 1 of queue occupancy ratio (\(O_{th1}\)) & 0.25 \\ The threshold 2 of queue occupancy ratio (\(O_{th2}\)) & 0.50 \\ Weighting factor \(\alpha\) & 0.9 \\ Packet size & 1000 bytes \\ Rate selection factor (\(\gamma\)) & 0.15 \\ Rate adaptation cycle & 4.0 \(\times\)_RTT_ \\ Simulation time & 200 s \\ The rate of CBR application & 600 kb/s \\ Initial rate of multicast & 50 kb/s \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Experiment parameters. Figure 4: The simulation topology. #### 5.2.2 The Basic Performance of SRMCC

The proposed rate adaption method is based on fair shared rate estimation, for which we performed many experiments to evaluate the performance of SRMCC, in terms of throughput, packet loss rate, and bandwidth utilization, in the case of multiple multicast groups co-existing. In Figure 6a, we take four multicast flows as an example to show the variation in throughput of each multicast flow over time in the presence of multiple multicast groups. We can see that after a short period of adjustment, the throughput of the four multicast flows becomes very even and does not fluctuate very much. That reflects the aggregation of the proposed rate adaptation method and the effectiveness of the fair shared rate estimation method. Figure 6b shows variations in the average packet loss rate of SRMCC under different numbers of multicast groups. As the number of multicast groups increases, the packet loss rate remains at a relatively low level, which can meet the reliability requirements of most applications. Figure 6c shows the total bandwidth utilization of SRMCC under different numbers of multicast groups. The total bandwidth utilization hardly decreases as the number of multicast groups increases, which reflects the good scalability of SRMCC. In summary, SRMCC is able to achieve good protocol fairness, scalability, and a low packet loss rate, and can be well applied to scenarios where multiple multicast groups exist. Figure 5: Experiments on the setting of value \(\gamma\). **(a)** The throughput ratio of multicast traffic to TCP traffic under different rate selection factors \(\gamma\): **(b)** The packet loss rate of multicast traffic under different rate selection factors \(\gamma\). Figure 6: The basic performance of SRMCC.