Data centers are considered as the indispensable infrastructure for cloud services nowadays. However, large-scale data centers use the traditional TCP protocol may experience performance issues, such as TCP incast. TCP incast is caused by the deficiency of TCP works for many-to-one traffic patterns on high-bandwidth, low-latency networks. In this paper, we propose a new TCP variant named Threshold Controlled TCP (TC-TCP) for data center networks. TC-TCP combines explicit congestion notification (ECN) with a novel control scheme at the sources. Sources estimate the fraction of marked packets, and use that as a signal for the extent of congestion. This allows TC-TCP to operate without packet losses and achieving high throughput. The ns-2 simulation results reveal that TC-TCP obtains better performance as compared to DCTCP and New Reno in data center networks.