Multilayered network interaction among various networks such as IP/MPLS packet networks and optical fiber networks are now achieved using generalized multiprotocol label switching (GMPLS) technology. One unique feature of GMPLS networks is that GMPLS packet-layer label switching paths (LSPs), such as IP/MPLS LSPs, sometimes tunnel through GMPLS lower layer LSPs such as optical fiber/lambda LSPs. One problem that occurs in this situation is protecting an important primary packet LSP by using a protection LSP that is physically separated from the primary LSP. The packet router has difficulty recognizing lower layer LSPs that are totally disjointed from the primary LSP. This is because, in a GMPLS's packet layer, a source router only differentiates one lower layer LSP from another, and does not check the disjointedness of segments through which the lower layer path passes. Sometimes, different lower LSPs pass through the same optical fiber, and a malfunction of one optical fiber sometimes causes many lower layer LSPs to malfunction at the same time. To solve this problem, a shared risk link group (SRLG) is introduced. Network links that belong to the same SRLG share a common physical resource. We apply this SRLG to the proposed hierarchically distributed path computation elements (HDPCEs) and achieve effective disjointed SRLG protection for important primary GMPLS packet paths.

This work proposes a distributed fault protection mechanism called the Dynamic-Shared Segment Protection (DSSP) algorithm for WDM (Wavelength Division Multiplexing) mesh networks. The objects are to assure high probability of path protection and efficient use of network resources. The proposed approach exploits the segment protection mode, which accommodates the characteristics of both path-based and link-based protections, for providing finer service granularities, to satisfy the versatile requirements of critical applications in the foreseeable future. To show that DSSP can improve performance efficiency, simulations are conducted using four networks (NSFNET, USANET, Mesh 66, Mesh 99) for a comparative study of the proposed DSSP versus ordinary shared protection schemes and SLSP (Short Leap Shared Protection). Simulation results reveal that the proposed DSSP method results in much lower blocking probability and has higher network utilization. Consequently, it is very useful for applications to a real-time WDM network, which changes status dynamically.

This paper proposes a disjoint path selection scheme for Generalized Multi-Protocol Label Switching (GMPLS) networks with Shared Risk Link Group (SRLG) constraints. It is called the weighted-SRLG (WSRLG) scheme. It treats the total number of SRLG members related to a link as part of the link cost when the k-shortest path algorithm is executed. In WSRLG, a link that has many SRLG members is rarely selected as the shortest path. Simulation results show that WSRLG finds more disjoint paths than the conventional k-shortest path algorithm. In addition, since WSRLG searches for the weight of the SRLG factor by using a modified binary search algorithm while satisfying the required number of disjoint paths between source and destination nodes, it can find cost-effective disjoint paths.