Buffer scaling for optical packet switching networks with shared RAM

According to a historical rule of thumb, which is widely used in routers, the buffer size of each output link of a router should be set to the product of the bandwidth and the average round-trip time. However, it is very difficult to satisfy this buffer requirement for ultra-high-speed dense wavelength division multiplexing (DWDM) networks with the current technology. Recently, many researchers have challenged the rule of thumb and have proposed various buffer sizing strategies requiring less buffer. Most of them were proposed for electronic routers with input and output buffering. However, shared buffering is a strong candidate for future DWDM optical packet switching (OPS) networks because of its high efficiency. As all links use the same buffer space, the wavelength count and nodal degree have a big impact on the size requirements of shared buffering. In this paper, we present a new buffer scaling rule showing the relationship between the number of wavelengths, nodal degree, and the required shared buffer size. By an extensive simulation study, we show that the buffer requirement increases with O((NW0.85)-W-0.85) for both standard TCP and paced TCP, while XCP-paced TCP's buffer requirement increases with O((NW0.85)-W-1) for a wide range of N and W, where N is the nodal degree and W is the number of wavelengths. (C) 2010 Elsevier B.V. All rights reserved.