Communication networks: Survivable routing algorithm with mixed shared protection in fault-tolerant GMPLS multi-layered optical networks

In this paper, we studied survivability in general multi-protocol label switching (GMPLS) multi-layered optical networks and proposed a novel mixed shared protection algorithm (MSPA) based on the integrated layered graph (ILG) to tolerate single-fibre link failure. The ILG is composed of one virtual topology layer (VTL), corresponding to IP/MPLS layer; multiple wavelength-plane layers (WPLs), corresponding to the wavelength-division multiplexing (WDM) optical layer; and some virtual links that connect the VTL to each WPL in order to solve the problem on routing, wavelength assignment and low-speed traffic grooming. For every connection request, the MSPA first computes a single-hop or multi-hop label switching path (LSP) pair, involving a working LSP and a physical link-disjoint backup LSP in the VTL. If the LSP pair is not found in the VTL, the MSPA computes the new LSP pair in the WPL. Conversely, if the new LSP pair is not detected in the WPL, the MSPA computes the hybrid multi-hop LSP pair in the ILG. In the MSPA, if the two working LSPs are in physical link-disjoint, their corresponding backup LSPs can share the backup bandwidth. In addition, theworking LSPs and the backup LSPs can also share the same mixed ofwavelength, in which the different bandwidths can be assigned to different working and backup LSPs. Simulation results show that, compared to previous algorithm, the MSPA can obtain a better bandwidth utilisation ratio (BUR) with a lower blocking probability.