A system, method or computer readable medium to provide efficient congestion notification is described herein. In various embodiments, a packet is received at an intermediate node of one or more data center networks. A current queue length at the intermediate node is determined. A threshold value for the current queue length is tuned by dynamically computing an upper bound and a lower bound based at least in part on the network. The packet is marked to indicate possible congestion in the one or more data center networks when the current queue length exceeds the threshold value. In some embodiments, the packet is marked when it is being de-queued. In a further embodiment, Flexible Initial Packet Size (FIPS) may be utilized to improve the efficiency of the tuning.