Effective deflection control method in optical packet switching networks with shared buffers

Deflection routing is considered as a method to avoid packet collisions in an optical packet switching system. Deflection routing is a method of avoiding collision by link substitution, in which the colliding packet is sent to an idle link. Thus, the load on the congested part of the network is distributed and the bandwidth can be utilized effectively. When excessively frequent deflections are performed, however, the load on the whole network is increased, which produces an adverse effect. Another problem is that sequence errors can occur in the same flow due to differences of transmission delay, since packets are sent to different routes. From these points of view, this paper proposes a deflection control method which can remedy the above problems, and applies the proposed method to an optical packet switching system. In the proposed control method, class separation is performed with respect to sequence error, and deflection is permitted to packets of nonpriority class. This improves performance by large-scale grouping. In order to alleviate the increase in load on the whole network, a control algorithm which can deal with changes of the link utilization and the number of traversed hops is devised. The effectiveness of the approach is shown by computer simulation. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 90(9): 67– 77, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20312