End-to-end network latency has become an important issue for big data processing on large-scale and heterogeneous data centers. To realize them, a low-latency inter-switch network is required. In recent years, a novel network based on a random regular graph such as Jellyfish has been proposed as a solution to these problems. To realize this network on Infiniband, we explore layered shortest path routing that guarantees deadlock freedom. Infiniband can avoid deadlocks by using Virtual Lane (VL), which is a QoS guarantee mechanism. However, the output VL is indirectly determined by using Service Level (SL) held by each packet. In this research, to minimize the number of consumed SLs, we propose an algorithm based on a graph coloring problem to assign SLs to all source-destination pairs. The proposed method can reduce the number of consumed SLs by up to 38%compared to the conventional SL mapping method.