Why Does Flow Director Cause Packet Reordering?

TL;DR

This paper analyzes why Intel Ethernet Flow Director, despite its benefits, can cause packet reordering in multiprocessing environments, leading to performance issues, and verifies the analysis through experiments.

Contribution

It provides a simplified model explaining the causes of packet reordering due to Flow Director and experimentally verifies these causes.

Findings

Flow Director can cause packet reordering in multiprocessing environments.

Packet reordering negatively impacts TCP performance.

Experiments confirm the analysis of reordering causes.

Abstract

Intel Ethernet Flow Director is an advanced network interface card (NIC) technology. It provides the benefits of parallel receive processing in multiprocessing environments and can automatically steer incoming network data to the same core on which its application process resides. However, our analysis and experiments show that Flow Director cannot guarantee in-order packet delivery in multiprocessing environments. Packet reordering causes various negative impacts. E.g., TCP performs poorly with severe packet reordering. In this paper, we use a simplified model to analyze why Flow Director can cause packet reordering. Our experiments verify our analysis.