Towards a Bufferless Optical Internet

Abstract

This paper investigates the relationship between buffer size and long-term average TCP performance in dense wavelength division multiplexing (DWDM) networks. By investigating TCP NewReno, we demonstrate that buffer requirements are related to the number of wavelength channels at a bottleneck. With sufficient wavelengths, high throughput can be obtained with a buffer of one packet per channel; furthermore, there may be situations where an entirely bufferless optical packet switching (OPS) will become feasible. For this study, we develop new evaluation tools. First, we propose a method based on a two-part analytical model, with a new ¿open loop¿ component which approximates packet discarding in a bottleneck DWDM switch, and a ¿closed loop¿ fixed-point which reflects the impact of TCP. This analytical method provides accurate and scalable approximations of throughput and packet loss rate that can be used as part of a tool for DWDM network and switch design. Second, we propose an extrapolation technique to allow simulation of TCP over long ultra-high bit rate links, avoiding the intractable processing and memory requirements of direct simulation. This extrapolation technique enables us to validate the analytical model for arbitrarily high bit rate scenarios.