# Towards Adaptive Multipath Managing:
## 4 Performance Evaluation
### Simulation Results
The OOO DSN can be attained by the offset between the DSNs of two consecutively received MPTCP data chunks (the difference between the DSN of the current MPTCP chunk and that of the latest received MPTCP chunk). Figure 9 shows a comparison of out-of-order chunks among the baseline MPTCP, MPTCP + (PU)\({}^{2}\)M\({}^{2}\), and MPTCP-LM\({}^{3}\). As the figure shows, the baseline MPTCP scheme generated more out-of-order chunks and required increased unnecessary packet reordering than both MPTCP + (PU)\({}^{2}\)M\({}^{2}\) and MPTCP-LM\({}^{3}\). This was because the baseline MPTCP's scheduler assigned data traffic over all the paths, without considering that a poorly performing path or a failure prone path would cause extremely great numbers of out-of-order chunks for reordering. In contrast, both MPTCP + (PU)\({}^{2}\)M\({}^{2}\) and MPTCP-LM\({}^{3}\) could detect a broken/poorly performing path and select a group of stable paths for data transmission. In this way, they could possibly allocate data traffic over the stable and high performing paths and thus reduce the out-of-order data reception. However, it was noted that MPTCP + (PU)\({}^{2}\)M\({}^{2}\) often generated more out-of-order data chunks than MPTCP-LM\({}^{3}\). This was because in MPTCP + (PU)\({}^{2}\)M\({}^{2}\), the paths selected for multipath transmission  
Figure 8: The comparison of data sending and receiving times. would be frequently changed and sensitive to paths' delay variations, while in MPTCP-LM\({}^{3}\), the path group, which was jointly determined by the paths' delay and _cvand_ characteristics, was relatively stable and changed little. When comparing the three schemes, we can see that the peak out-of-order data reception at the receiver was up to \(1.40\times 10^{6}\) when using the baseline MPTCP, while it was approximately \(1.39\times 10^{5}\) when using both MPTCP + (PU)\({}^{2}\)M\({}^{2}\) and MPTCP-LM\({}^{3}\). (3) End-to-end delay: Figure 10 shows a comparison of end-to-end delay performance when using the baseline MPTCP, MPTCP + (PU)\({}^{2}\)M\({}^{2}\), and MPTCP-LM\({}^{3}\) schemes, respectively. As we analyzed earlier, both MPTCP-LM\({}^{3}\) and MPTCP + (PU)\({}^{2}\)M\({}^{2}\) could prevent an underperforming path (or a broken path) from multipathing, and they could thereby prevent unnecessary retransmission in the underperforming or broken paths. This made MPTCP-LM\({}^{3}\) and MPTCP + (PU)\({}^{2}\)M\({}^{2}\) reduce the unnecessary retransmission delay. Moreover, both MPTCP-LM\({}^{3}\) and MPTCP + (PU)\({}^{2}\)M\({}^{2}\) could possibly ensure that the MPTCP segments arrive at the receiver in the right order. This helped the two schemes reduce the packet reordering delay. As a result, MPTCP-LM\({}^{3}\) and MPTCP + (PU)\({}^{2}\)M\({}^{2}\) obtained a lower level of delay than the baseline MPTCP. However, MPTCP + (PU)\({}^{2}\)M\({}^{2}\) performed worse than MPTCP-LM\({}^{3}\) because more out-of-order data reception in MPTCP + (PU)\({}^{2}\)M\({}^{2}\) required increased reordering than MPTCP-LM\({}^{3}\). Moreover, in MPTCP + (PU)\({}^{2}\)M\({}^{2}\), the paths used in multipath transmission often changed, and as a result, the data traffic could be offloaded from one path to another frequently, which incurred additional processing time overhead. When comparing the three methods in terms of the cumulative average delay (with a total of 100 s of simulation time), the MPTCP-LM\({}^{3}\) scheme's cumulative average delay was approximately 4.35% lower than that of the baseline MPTCP and 1.03% lower than that of MPTCP + (PU)\({}^{2}\)M\({}^{2}\). (4) Jitter comparison: Jitter can be defined as the amount of packet delay variation in the end-to-end data traffic transmission time. Jitter is a well suited metric to evaluate and analyze the temporal performance of a multipath transmission protocol. A higher level of jitter is more likely to occur on a poorly performing transport technology and vice versa. Figure 11 shows a comparison of the jitter performance when the three schemes were used.