QoS Multi-Spanning Tree for Optical Burst Switching

Abstract

Optical Burst Switching (OBS) has been proposed as a future high-speed switching technology for Internet Protocol (IP) networks that may be able to efficiently utilize extremely high capacity links without the need for optical-electronic (O/E) conversions at intermediate nodes. Among its benefits of supporting statistical multiplexing at a rational granularity, OBS still gives poor performance in terms of burst drop probability. In an Optical Burst Switched network, the existence of highly congested links could lead to unacceptable performance for the entire network, causing Quality of Service (QoS) degradation to flows inserted into the network. In this paper we propose a Multi-Spanning Tree architecture that improves QoS management by increasing the efficiency in the wavelength assignment process. The new protocol uses wavelength spanning trees on demand depending on the QoS constraints demanded by inserted traffics. Moreover, the protocol avoids burst overlapping on each edge of the spanning trees, while at the same time, permitting the reutilization of lambda assignments between nodes contained in the same branch. Therefore, the protocol allows traffic aggregation from many nodes into a single branch, improving efficiency and link utilization. We take a traffic engineering approach to branch selection with the objective of balancing the traffic across the network links to reduce congestion and to improve overall performance. In this paper, the architecture, the design of the protocol and some simulation results are presented.