Measuring the difference of packet latencies in data center

More and more applications are being moved to data center. However, little research for the characteristic of the difference of packet latencies in data center was carried out. Packet latency is a key issue of latency-sensitive applications. In this paper, we explore the nature of packet latency in a 3-level tree topology data center and make a detailed study of the difference of packet latencies by using NS2 to analyze the packetlevel traces with different data transmission protocols. We find that though the workload and over-subscription in data center have a significant effect on the difference of packet latencies for most of the data transmission protocols, pFabric has a better performance than other protocols and the difference of packet latencies is much smaller than others. We also use ELR (equal-length routing) to equalize the pathway length for all packets and find that the difference of pathway length has little impaequal-length routingct to the difference of packet latencies on regular TCP protocols, but has a significant effect on pFabric. We also verify that pFabric with ELR has a higher performance than other data transmission protocols for the difference of packet latencies and can meet the requirements of most real-time applications.