# SVDC: Synchronous Update with the Division and Combination of SRv6 Policy
## 5 Performance Evaluation
### Result and Analysis  
#### 5.2.1 Number of Times for Policy Distribution  
The number of times for policy distribution is the number of times the controller distributes the numerous policies derived from a single computation to the corresponding target nodes. Table 3 and Figure 5 depicts the number of times for policy distribution of ordered update, two-phase update, and SUDC. From Figure 5 and Table 3, it can be seen that the number of times for policy distribution of ordered update and two-phase update is equal to the number of policy entries contained in the test set. This is due to the fact that policies are distributed to the target nodes one by one in these two schemes. SUDC needs to distribute all the SID blocks obtained by the policy-dividing algorithm, so the number of times for policy distribution of SUDC is the number of policy distribution SID blocks. The distribution policy times in SUDC are 46.71% less than those in ordered update and two-phase update. Furthermore, as the test set size increases, the reduction in the number of times for policy distribution of SUDC becomes increasingly pronounced. Coexisting Time of New and Legacy Policies  
In the network, some packets execute the new SRv6 TE policy while others execute the legacy SRv6 TE policy simultaneously. The time during which this state persists is referred to as the new policy and legacy policy coexisting time. For ordered updates, each SRv6 policy is distributed to the destination router along the path with the smallest transmission delay. The coexisting time of new and legacy policies for ordered updates is the time lag between the moment when the first policy is received and the moment when the last policy is received. For a two-phase update, each SRv6 policy whose target node is an internal switch is distributed sequentially along the path with the smallest transmission delay, and then each SRv6 policy whose target node is an ingress switch is distributed sequentially along the path with the smallest transmission delay. Before updating ingress switches, all packets are processed according to legacy policies. Starting from updating ingress switches, new policies process packets with new version tags, and packets with old version tags are processed by legacy rules. Therefore, the coexisting time of new and legacy policies for two-phase updates is the time lag between the moment when the first policy, whose target node is an ingress switch, is received and the moment when the last policy, whose target node is an ingress switch, is received. Figure 5: Number of times for policy distribution. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Number of** & & & & \\
**Policies** & **SUDC** & **Ordered Update** &
\begin{tabular}{c} **Two-Phase** \\ **Update** \\ \end{tabular} & **Reduction Ratio** \\ \hline
5000 & 3075 & 5000 & 5000 & 38.50\% \\
10,000 & 5757 & 10,000 & 10,000 & 42.43\% \\
25,000 & 13,438 & 25,000 & 25,000 & 46.25\% \\
50,000 & 25,934 & 50,000 & 50,000 & 48.13\% \\
100,000 & 50,965 & 100,000 & 100,000 & 49.04\% \\
250,000 & 125,968 & 250,000 & 250,000 & 49.61\% \\
500,000 & 250,963 & 500,000 & 500,000 & 49.81\% \\
1,000,000 & 500,963 & 1,000,000 & 1,000,000 & 49.90\% \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Number of times for policy distribution. For SUDC, each policy distribution SID block is multicast to the set of target routers along the transmission delay minimizing spanning tree. In addition, this metric of SUDC is the time lag between the moment when the first multicast SID block first arrives at one router in its set of target routers and the moment when the last multicast SID block finally arrives at one router in its set of target routers. Table 4 and Figure 6 show the coexisting time of new and legacy policies for an ordered update, two-phase update, and SUDC. The average coexisting time in SUDC is 99.38% and 96.80% less than that in ordered updates and two-phase updates, respectively.