Congestion Control Algorithm

Congestion Control provides performance isolation when multiple applications running on the same cluster. Additionally, it prevents congestion spreading when there is a slow receiver, reduce latency in the cluster, improves fairness, prevents parking-lot effects and packet's drop in lossy networks.

ZTR_RTTCC is NVIDIA’s default Congestion Control algorithm.

The diagram below shows an example of head of the line blocking scenario.

The following are the Datacenter Congestion Control challenges:

• Several µ-sec of latency with hundreds of Gbps of bandwidth

  • Congestion buildup is fast, so the congestion loop should be short

• A wide variety of traffic types, topologies and applications

  • Hard to develop an algorithm that suits all

  • Congestion Control algorithms are constantly being introduced with new congestion indications

• Hardware implementation is not robust enough

• Software implementation reacts too slow