Approaches for contention resolution among packets in the optical domain have been traditionally devised for distributed operation locally within individual nodes, exploiting both the time and wavelength dimensions. In this work, we focus on packet contention prevention in an optical packet-switched network, tackling the problem from the perspective of a network-wide end-to-end label-switched path (LSP) admission control and LSP-to-wavelength assignment. We present two contention-preventing wavelength assignment schemes, called minimum interference (MI) schemes, that can be implemented within a network control plane based on a generalized multiprotocol label switching (GMPLS) protocol suite. MI schemes envision that LSP-to-wavelength assignment is accomplished by a novel ranking policy utilized for the tie breaking of the GMPLS label set (i.e., the available wavelength set). Specifically, the novel GMPLS object named the suggested vector (SV) is populated during forward propagation of the path message, collecting, for each wavelength, the amount of bandwidth not interfering with already-established LSPs. During the backward propagation of the Resv message, the actual LSP-to-wavelength allocation is performed based on the preference level stored in the SV object. Numerical results show that MI schemes are effective in decreasing end-to-end packet loss and wavelength conversion probabilities, compared with the no-preference scheme that does not exploit such optimization.
© 2008 Optical Society of AmericaPDF Article