Cyclic Matrix Coding to Mitigate ACK Blocking of MPTCP in Data Center Networks

Multi-path Transmission Control Protocol (MPTCP) has shown great potential in improving network bandwidth and robustness by utilizing multiple subflows in data center networks (DCNs). However, the delay and loss heterogeneities of multiple paths potentially cause packet reordering, resulting in the ACK blocking and increased latency. Recent coding-based solutions use forward error correction (FEC) to mitigate path heterogeneity with redundant encoded packets. However, current FEC-based solutions work at the subflow level, that is, each subflow independently generates redundant encoded packets. This intra-subflow coding, however, does not leverage the path diversity, easily suffering from long tail latency. In this article, we propose a new MPTCP based on cyclic matrix coding, called as CM-MPTCP, which encodes packets inter subflow to leverage the path diversity. Specifically, to let good paths help bad ones, the good paths deliver more redundant packets encoded based on cyclic matrix, which gives more coding opportunities to packets on bad paths, thus achieving high packet decoding ratio at the receiver side. The results of large-scale NS2 simulations show that CM-MPTCP effectively mitigates the ACK blocking and reduces the average flow completion time (AFCT) by about $45\% \sim 70\%$ under a wide variety of network conditions compared with the state-of-the-art coding-based MPTCPs.