Chengyi Gao

Traffic grooming and regenerator placement in impairment-aware optical WDM networks

In this paper, we address the problem of traffic grooming and regenerator placement in a WDM optical network in which lightpaths are hop-constrained by physical impairments. The efficient placement of regenerators and electronic grooming equipment at ROADM nodes for a given network topology is required such that all traffic demands can be supported with minimum cost. We present a detailed ROADM node architecture together with an associated cost model, and we propose an auxiliary-graph-based heuristic for jointly placing regenerators and electronic grooming equipment in the network. The numerical results show that combining the grooming problem with the placement of regenerators reduces the network cost significantly compared to the cases in which traffic grooming and regenerator placement are handled separately.

Survivable impairment-aware traffic grooming and regenerator placement with connection-level protection

In this paper, we address the problem of survivable traffic grooming and regenerator placement in optical wavelength division multiplexing (WDM) networks with impairment constraints. The working connections are protected end to end by provisioning bandwidth along a sequence of lightpaths through either a dedicated or a shared connection-level protection scheme. We propose an auxiliary-graph-based approach to address the placement of regenerators and grooming equipment for both working and backup connections in the network in order to minimize the total equipment cost. Simulation results show that the proposed algorithms outperform lightpath-level protection algorithms, in which each lightpath is protected separately. We also show the performance of connection-level protection under both dedicated and shared protection schemes in terms of the network cost, along with the effect of different cost models on equipment placement and performance for networks with different line rates. The restoration time of dedicated and shared connection-level protection is also investigated.

SRLG-Aware Topology Aggregation for Survivable Multi-Domain Optical Networks

In multi-domain optical networks, due to confidentiality and management considerations, it may be infeasible to exchange complete domain state information among domains. Topology aggregation (TA) is a widely adopted technique for aggregating a domains detailed topology into simpler aggregated topology with limited information. In order to generate an abstracted topology that is more survivable against failures, the TA approach may also consider the presence of shared risk link groups (SRLGs), each of which defines a set of links that may fail simultaneously. We propose SRLG-aware topology aggregation approaches that can help to find a pair of inter-domain paths with a minimum set of common SRLGs. We find that constructing an aggregated topology while taking into account the SRLG distribution can help in developing a more survivable aggregated multi-domain network. Moreover, exchanging SRLG information prior to constructing the TA further increases the survivability of the aggregated topology. The performance of various TA schemes, such as single node, star, and full mesh, is also investigated.

Cost efficient traffic grooming and regenerator placement in impairment-aware optical WDM networks

Abstract In this paper, we address the problem of traffic grooming and regenerator placement in a WDM optical network in which lightpaths are hop-constrained by physical impairments. The efficient placement of regenerators and electronic grooming equipment at ROADM nodes for a given network topology is required such that all traffic demands can be supported with minimum cost. We present a detailed ROADM node architecture together with an associated cost model. We model the problem by Integer Linear Programming (ILPs) and propose an auxiliary-graph-based heuristic for jointly placing regenerators and electronic grooming equipment in the network. To evaluate the performance of the proposed heuristic, we also derive a lower bound on the network cost. The numerical results show that combining the grooming problem with the placement of regenerators reduces the network cost significantly compared to the cases in which traffic grooming and regenerator placement are handled separately. The performance of the proposed polynomial-time heuristic is very close to the lower bound and approaches the bound as the network load increases.

Virtual optical network embedding considering mixed transparent and translucent virtual links

An intelligent virtual optical network embedding approach is proposed, which minimizes the network resource usage of each request. Both transparent and translucent virtual optical link embedding is considered as specifically required by virtual optical links.

Domain-Disjoint Routing Based on Topology Aggregation for Survivable Multi-Domain Optical Networks

In a multi-domain network, domains may be defined based on geography or administrative boundaries. For domains that are constructed based on geographic locations, multiple links within the same domain may fail simultaneously due to geographically localized failure events. For domains that are defined administratively, a domain administrator may not be able to provide link-disjointness for two paths traversing the domain. Thus, in some cases, it may be necessary to find two domain-disjoint paths to improve survivability. In this paper, we propose an algorithm to find domain-disjoint working and backup paths for multi-domain routing requests. We prove that our approach is optimal in finding domain disjoint paths with minimum total cost.

Survivable inter-domain routing based on topology aggregation with intra-domain disjointness information in multi-domain optical networks

In a network in which multiple domains are defined due to geographical and/or administrative reasons, only a limited amount of domain information is exchanged by domain service providers. Topology aggregation is a method used to facilitate this limited information exchange. The amount of information provided for each domain may vary based on the technical and management decisions taken by the service provider. For instance, some domains may choose to provide only a single shortest path between two border nodes, while another may be able to provide a pair of disjoint paths with minimum total cost. In such cases, end-to-end protected path routing needs to facilitate and use different amounts of domain information provided by domain service providers in order to find the best solution. In this work, we propose several approaches that help find a pair of disjoint end-to-end paths that may traverse multiple domains from source to destination and result in minimum total cost. These approaches include methods for inter-domain information exchange that carry costs of disjoint paths within a domain. The performance of minimizing the total cost of a pair of end-to-end paths is investigated. Finally, the blocking probabilities of these various approaches due to the existence of trap topologies in the network are also discussed.

Domain-disjoint routing based on topology aggregation for survivable multidomain optical networks

In a multidomain network, topology aggregation (TA) may be adopted to provide limited information regarding intradomain connectivity without revealing detailed topology information. If the TA information does not include details on the mapping of aggregated links in the TA over the physical topology, then physical disjointness cannot be guaranteed in the case in which two interdomain paths traverse the same domain through different aggregated links. Thus, in order to provide survivability over multiple domains, it may be necessary to find two domain-disjoint paths in the multidomain network. In this paper, we propose an algorithm for finding domain-disjoint working and backup paths for a multidomain connection request. The algorithm modifies the original multidomain network topology by adding cyclic structures that enable the direct application of Bhandaris algorithm to find a pair of diverse paths with minimum total cost over the modified topology. We give detailed analysis of various scenarios that may occur during the routing procedure, and the corresponding performance of our approach in these scenarios. We show that our approach can achieve good performance in finding domain-disjoint paths with minimum total cost.

Survivable Impairment-Aware Traffic Grooming and Regenerator Placement with Dedicated Connection Level Protection

In this paper, we address the problem of survivable traffic grooming and regenerator placement in optical WDM networks with impairment constraints. The working connections are protected end to end by provisioning bandwidth along a sequence of lightpaths through a dedicated connection-level protection scheme. An auxiliary-graph-based approach is proposed to address the placement of regenerators and grooming equipment for both working and dedicated backup connections in the network with the goal of minimizing the total equipment cost. Simulation results show that the proposed algorithm outperforms a lightpath-level protection algorithm, in which each lightpath is protected separately. We also show the effect of different cost models on equipment placement and evaluate the performance for networks with different line rates.

SRLG-aware topology aggregation for survivable multi-domain optical networks

In multi-domain optical networks, due to confidentiality and management considerations, it may be infeasible to broadcast complete domain state information among domains. Nevertheless, sufficient information on each domain is required in order to keep network activities operating successfully. Topology Aggregation (TA) may be adopted to abstract a domains detailed topology into an aggregated topology which only shows limited information about the network. With the introduction of Shared Risk Link Groups (SRLGs), each of which includes a set of links affected by the same failure, the TA approach needs to consider the presence of SRLGs to generate a more survivable aggregated topology. In this paper, we propose SRLG-aware topology aggregation approaches that can help in finding a pair of inter-domain paths with a minimum set of common SRLGs.