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.
© 2009 IEEE
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