Promoting the use of end-to-end congestion control in the Internet

TLDR

Increasing deployment of non‑congestion‑controlled best‑effort traffic can cause extreme unfairness to TCP traffic and even lead to congestion collapse. The authors aim to promote end‑to‑end congestion control in future protocols by arguing that routers must identify and restrict the bandwidth of selected high‑bandwidth best‑effort flows during congestion. They discuss several general approaches for identifying such flows, including classifying them as unresponsive, non‑TCP‑friendly, or disproportionate‑bandwidth when congestion occurs.

Abstract

This paper considers the potentially negative impacts of an increasing deployment of non-congestion-controlled best-effort traffic on the Internet. These negative impacts range from extreme unfairness against competing TCP traffic to the potential for congestion collapse. To promote the inclusion of end-to-end congestion control in the design of future protocols using best-effort traffic, we argue that router mechanisms are needed to identify and restrict the bandwidth of selected high-bandwidth best-effort flows in times of congestion. The paper discusses several general approaches for identifying those flows suitable for bandwidth regulation. These approaches are to identify a high-bandwidth flow in times of congestion as unresponsive, "not TCP-friendly", or simply using disproportionate bandwidth. A flow that is not "TCP-friendly" is one whose long-term arrival rate exceeds that of any conformant TCP in the same circumstances. An unresponsive flow is one failing to reduce its offered load at a router in response to an increased packet drop rate, and a disproportionate-bandwidth flow is one that uses considerably more bandwidth than other flows in a time of congestion.