Perspectives on Router Buffer Sizing: Recent Results and Open Problems

Arun Vishwanath, Vijay Sivaraman, and Marina Thottan
Appears in: 
CCR April 2009

The past few years have witnessed a lot of debate on how large Internet router buffers should be. The widely believed rule-of-thumb used by router manufacturers today mandates a buffer size equal to the delay-bandwidth product. This rule was first challenged by researchers in 2004 who argued that if there are a large number of long-lived TCP connections flowing through a router, then the buffer size needed is equal to the delay- bandwidth product divided by the square root of the number of long-lived TCP flows. The publication of this result has since reinvigorated interest in the buffer sizing problem with numerous other papers exploring this topic in further detail - ranging from papers questioning the applicability of this result to proposing alternate schemes to developing new congestion control algorithms, etc.

This paper provides a synopsis of the recently proposed buffer sizing strategies and broadly classifies them according to their desired objective: link utilisation, and per-flow per- formance. We discuss the pros and cons of these different approaches. These prior works study buffer sizing purely in the context of TCP. Subsequently, we present arguments that take into account both real-time and TCP traffic. We also report on the performance studies of various high-speed TCP variants and experimental results for networks with limited buffers. We conclude this paper by outlining some interesting avenues for further research.