Design & evaluation of all-optical buffer-constrained routers at the Internet backbone

The focus of this dissertation is on the modeling and performance evaluation of buffer-constrained all-optical routers. Of particular interest is the IRIS (Integrated Router Interconnected Spectrally) router, an all-optical implementation of the load-balanced Birkhoff-von Neumann switch architecture. The primary limitation of the router stems from the dearth of buffering in its all-optical data path, where per output buffering is limited to just a fraction of a single 1,500 byte TCP/IP packet. We consider the application of such a router at the Internet backbone.;First, we present the results of extensive network simulations conducted using realistic flow-level traffic models. We show that under bursty Internet traffic, buffer-constrained routers exhibit poor performance, even under light load conditions. To overcome this problem, a rate-control framework for shaping bursty Internet traffic into a deterministic traffic stream is considered and evaluated. Our work shows that fine-grained traffic shaping of aggregate traffic at the edge of the all-optical cloud obviates the need for any significant buffering within the cloud.;Second, the complexity of generating realistic backbone traffic using flow-level traffic models in network simulations limited our analysis to small router and network configurations. As an alternative, we consider several synthetic traffic generation models capable of modeling Gaussian and non-Gaussian traffic processes. Within the context of buffer-constrained routers, our work reveals that these models substantially underestimate the extent of the losses seen under bursty traffic. In order to understand why existing models are ineffective, we take a closer look at the fine timescale behavior of network traffic traces. It is shown that arrivals across smaller sub-intervals are highly erratic and prone to intermittent output load conditions that are sharply higher than the long-term mean. The dearth of buffering makes cell losses sensitive to such short-term behavior. A method that builds upon the multi-fractal wavelet model (MWM) is proposed and shown to be highly accurate. Additionally, the model has also proven useful in generating shaped traffic streams, thereby allowing us to analyze the performance under both bursty and shaped traffic conditions.;Lastly, application of the model has led to several important observations in the context of buffer-constrained routers: (i) One cannot rely on statistical multiplexing alone as a means to enable buffer-constrained routers. Benefits of statistical multiplexing are not evident at fine timescale granularities, where traffic appears largely non-Gaussian and highly erratic. (ii) The rate-control framework can be an enabler for large-scale all-optical buffer-constrained routers. It is shown that such routers can operate at peak loads, while suffering negligible degradation in performance.