The scalability of many datacenter applications is largely dependent on the networking infrastructure. Several studies addressed the network traffic characteristics from the perspective of network equipment, i.e., collecting and analyzing traffic data from routers, switches, or other network aggregation points. However, little is known about how traffic is directly generated by the servers. In this paper, we conduct an empirical study to characterize datacenter traffic from a server-centric perspective. We analyze data from more than 30,000 servers, located across more than 50 production datacenters, over a two-year time span. Our evaluation encompasses traffic statistics as well as network resources, based on short-term snapshots and long-term evolution of the collected metrics. In particular, we characterize the temporal and spatial characteristics of incoming and outgoing traffic volumes across servers, in packets as well as bytes per second. Our analysis provides a baseline for datacenter network modeling and workload model calibration. © 2013 IEEE.