PTCP: A Priority-Driven Congestion Control Algorithm to Tame TCP Incast in Data Centers

Abstract

Data centers have become a prevalent infrastructure to host a large number of services, such as social networking and Web search, which generally have rigorous delay requirements. Even a slight increase in delay can seriously affect the performance of applications. Therefore, there have been several efforts focusing on minimizing the flow completion time (FCT) to meet the delay requirements, such as ICTCP, which adjusts the receive window according to the available bandwidth and DCTCP that uses ECN to provide the feedback to end hosts in mixing workloads. However, both approaches are only for a specific scene and cannot effectively solve the problem that packets losses lead to timeouts due to TCP incast. Moreover, they all use the fair-share mechanism, which causes the increasing of the FCT for small flows, when background flows pour into the network. For example, background flows cause the increasing(≈ 5ms) of the FCT for the ICTCP in an incast experiment. To solve these problems, we propose a priority-driven congestion control algorithm, PTCP, which can effectively avoid the incast problem and improve the FCT in mixing workloads. The PTCP leverages the priority to adjust the receive window and control the interval time of ACK. To evaluate the PTCP, we conduct extensive experiments in NS-2. The simulation results show that the PTCP outperforms greatly previous schemes both in the incast scenario and mixing workloads.

Keywords

• Congestion
• TCP incast
• ACK control
• data centers
• priority