Optical Burst Switching (OBS) aims to provide higher utilization and greater flexibility at a lower cost and reduced complexity than current optical circuit switched networks. We introduce a new routing protocol for Optical Burst Switching, Shortest Path Prioritized Random Deflection Routing (SP-PRDR), that aims to lower burst loss probabilities while only using limited state information from traditional Internet Protocol technologies. We show, through analysis and simulation, that loss in OBS networks is significantly reduced by SP-PRDR for loads that previously gave moderate or low losses in the unmodified case. In the simulation examples studied, by using SP-PRDR we are able to increase the input load by approximately 15-20% while maintaining a constant burst loss probability of 10 −3. Additionally, unlike other schemes, we show that the worst case burst loss probability of SP-PRDR is provably upper-bounded by the burst loss probability of standard OBS.
We evaluate and compare the performance of timer-based and threshold-based assembly algorithms in Optical Burst Switching networks. Results including burst blocking probability, mean packet delay and link utilization at the ingress node are presented from both simulations and two theoretical models. The results are obtained for the full range of input traffic load so they can provide guidelines for design and dimensioning links to meet desired Quality of Service levels.
It is well known that optimal server placement is NP-hard. We present an approximate model for the case when both clients and servers are dense, and propose a simple server allocation and placement algorithm based on high-rate vector quantization theory. The key idea is to regard the location of a request as a random variable with probability density that is proportional to the demand at that location, and the problem of server placement as source coding, i.e., to optimally map a source value (request location) to a codeword (server location) to minimize distortion (network cost). This view has led to a joint server allocation and placement algorithm that has a time-complexity that is linear in the number of clients. Simulations are presented to illustrate its performance.
Abstract:The sending rate of commonly used TCP protocols is tightly coupled to packet loss within the network: a high rate of packet loss will cause a sender to slow down, thereby reducing the network load and decreasing subsequent packet loss rates. In this paper, we combine a widely verified source rate TCP model with an Optical Burst Switching (OBS) loss model, to find fixed-point input loads and loss rates for an OBS link carrying TCP traffic. In doing so, we show that if OBS networks are to be efficiently used to carry TCP traffic, many wavelengths with full wavelength conversion are required.
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