## 5 Results
### Analysis of Queue Threshold and Link Utilization  
Link utilization is the ratio of current link traffic to the maximum traffic that the interface can handle. While high link utilization depicts the link is busy, low link utilization shows that the link is underutilized. When link utilization exceeds the threshold under normal condition, it causes a considerable delay because of the increase in queue size. A queue of average length less than a certain threshold never causes packets to drop. This threshold depends on traffic characteristics, such as burstiness and arrival rate.  
We used packet loss percentage to determine queue threshold and link utilization in order to set these values for link rate adaption. We first estimated the data rate at which the queue starts to overflow and results in 1% packet loss and observed the impact of data rate on average queue length and link utilization. We implemented fat-tree topology of DCN and considered data transmission within pod 1 where host 1 sends data to host 2. We performed queue analysis for this topology and  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Number of Pods**} & **Power** & **Power** & **Power saving in** & **Power Consumption** & **Power saving in** \\  & **Consumption** & **Consumption** & **ElasticTree vs.** & **in ADAPTIVE** & **Adaptive TrimTree** \\  & **Fat-Tree (W)** & **ElasticTree (W)** & **Fat-Tree (\%)** & **Time (W)** & **vs. ElasticTree (\%)** \\ \hline
4 & 213.4 & 126.71 & 40.8 & 119.7 & 5 \\
8 & 1.174 k & 0.481 k & 59 & 445.07 & 7.5 \\
16 & 7.25 k & 2.2 k & 69 & 2.04 k & 7.3 \\
24 & 22.08 k & 6.2 k & 72 & 5.45 k & 12 \\
48 & 157.45 k & 38.06 k & 75 & 32.8 k & 13.8 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Power saving in Adaptive TrimTree.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Transport layer protocol & UDP \\ Window size & 32 kbytes \\ File size & 10 kbytes \\ Transmission time (each Iperf cycle) & 4 s \\ Buffer size & 8 kbytes \\ Transmission rate & 1000 Mbps \\ Time (periodic bandwidth report) & 1 s \\ \hline \hline \end{tabular}
\end{table}
Table 5: Iperf simulation parameters.  
observed the relationship between packet loss ratio and queue operation. We observed that for 0% packet loss, buffer utilization (buffer occupancy) is 0.56. Repeating these calculations, we generated a plot of packet loss percentage versus buffer utilization shown in Figure 5. When data rate is around 550 Mbps, the queue threshold increases to 0.8 and packet loss percentage becomes approximately equal to 1%.  
We also observed the network and link characteristics for inter-pod traffic. We observed that when link utilization is 55%, packet loss is 1%. From queue analysis and link utilization analysis we deduce that when packet loss percentage is above 1%, link utilization threshold and queue length reaches threshold and we must turn on extra switches or increase links capacity. Figure 6 shows the packet loss percentage vs. time which shows a continuous increase in packet loss percentage.  
The simulation parameters for Mininet simulations are given in Table 6.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Max number of switches & 20 \\ Number of servers & 16 \\ Core-aggregate & Transmission rate: 1000 Mbps delay: 1 ms queue length: 250 packets \\ Aggregate-edge & Transmission rate: 100 Mbps delay: 10 ms queue length: 125 packets \\ Edge-servers & Transmission rate: 10 Mbps delay: 15 ms queue length: 25 packets \\ \hline \hline \end{tabular}
\end{table}
Table 6: Mininet simulation parameters.  
Figure 5: Packet loss percentage vs. Utilization.  
Figure 6: Packet loss percentage vs. Time.