Many “rich-connected” topologies with multiple parallel paths between servers have been proposed for data center networks recently to provide high bisection bandwidth, but it remains challenging to fully utilize the high network capacity by appropriate multi-path routing algorithms. As flow-level path splitting may lead to traffic imbalance between paths due to flow size difference, packet-level path splitting attracts more attention lately, which spreads packets from flows into multiple available paths and significantly improves link utilizations. However, it may cause packet reordering, confusing the TCP congestion control algorithm and lowering the throughput of flows. In this paper, we design a novel packet-level multi-path routing scheme called SOPA, which leverages OpenFlow to perform packet-level path splitting in a round-robin fashion, and hence significantly mitigates the packet reordering problem and improves the network throughput. Moreover, SOPA leverages the topological feature of data center networks to encode a very small number of switches along the path into the packet header, resulting in very light overhead. Compared with random packet spraying (RPS), Hedera and equal-cost multi-path routing (ECMP), our simulations demonstrate that SOPA achieves 29.87%, 50.41% and 77.74% higher network throughput respectively under permutation workload, and reduces average data transfer completion time by 53.65%, 343.31% and 348.25% respectively under production workload.