A novel contention resolution scheme for optical burst switching (OBS) networks is proposed. Traffic payload is classified into two types at the edge nodes, and they are transferred through the core nodes using two different routing algorithms—least-hop first routing and shortest-path first routing, respectively, leading to balanced traffic loads among fiber links. By using this contention resolution scheme, active avoidance of burst contention is achieved. Performance evaluation and simulation results indicate that the new scheme outperforms the commonly used shortest-path first routing and is robust under both Poisson and self-similar traffic. Furthermore, the new scheme can provide quality-of-service (QOS) differentiation when used with wavelength conversion, and the implementation of this scheme is easy, which makes OBS technology more applicable in network engineering.
Considering the state of the art of wavelength conversion technology, it is likely to dictate a more limited and sparse deployment of wavelength converters in the optical burst switching (OBS) networks. Without wavelength conversion capabilities at optical switches, the start wavelength selection method becomes an important issue to avoid burst contention. We present a new start wavelength selection method, the minimum relative group combined interference level (Min-RGCIL) algorithm, which is a modified version of a proposed method called first-fit-TE (traffic engineering). The performance study indicates that the new method achieves better performance than the original one and is robust under Poisson and self-similar traffic.
Many recent studies have convincingly demonstrated that network traffic exhibits a noticeable self-similar nature, and most studies of optical burst switching (OBS) networks are under a fundamental assumption that full wavelength conversion is available throughout the network. In practice, however, economic and technical considerations are likely to dictate a more limited and sparse deployment of wavelength converters in the optical network. Therefore, we present a novel scheme for OBS Networks, called logical cascaded private subnet with start wavelength assignment policy. We define the concept of canoe relative to cluster in self-similar traffic, and introduce a new device named payload segregator at the edge node as a gateway to the OBS core node. According to the changes in the edge node framework, we put forward the concept of cluster private subnet and canoe private subnet in OBS core node correspondingly. Due to the absence of wavelength conversion capabilities, we assign start wavelengths to both private subnets before network start operation. A new start wavelength assignment policy is proposed for the absence of wavelength conversion capabilities in the core node of OBS Networks. The analytical results clearly show that logical cascaded private subnet scheme can yield better performance in terms of block probability than traditional OBS Networks, and logical cascaded private subnet with start wavelength assignment policy has the potential to improve the block probability by more than one order of magnitude compared with traditional OBS Networks, helping reduce the performance gap with respect to full wavelength conversion.