In this paper, we address the problem of providing differentiated levels of protection in MAN/WAN Ethernet environments. The IEEE 802.3ad bundling mechanism of Link-Aggregation is used to mitigate disruption of traffic due to link failure. We focus on the network design problem of accommodating Ethernet Virtual Connections (EVCs) traffic with given protection requirement with minimum budget utilizing novel Traffic Engineering (TE)based schemes. The initial investment cost of linkaggregate upgrade can be recovered by providing differentiated survivability services to customers.

This paper addresses multicast routing in 40 Gb/s traffic in heterogeneous optical networks. The multicast routing of multi-rate traffic (MRMT) problem is informally defined as the process of finding the best routing which maximizes the total bandwidth utilization in the network, for a given set of sessions, and a given WDM and TDM equipment budget. In our model, a multicast connection is realized by constructing a multicast tree. The whole process is divided into two steps. Numerical results demonstrate our approach utilizes network resources more efficiently, as compared to the approach based on shortest path algorithm.

In this paper, we address the design and management issues in routing a mixture of OC-192 and OC-768 streams in wavelength-routed optical networks. We assume that fiber links in the network are heterogeneous with respect to their transmission capability (i.e., links are designed to handle a given maximum bit-rate imposed by regenerator spacing). We investigate the issues of routing connection demands of various bit-rate requirements in such heterogeneous networks. In this environment, we introduce the routing of multirate traffic (RMT) problem. The RMT problem is informally defined as the process of finding the best routing which maximizes the total bandwidth carried in the network, for a set of sessions, within a given TDM equipment budget. We propose a two-phase optimization scheme (two-phase RMT). This scheme first obtains a basis solution used in routing 40-Gb/s traffic only on OC-768 capable links without the use of TDM equipment. In the second phase, an iterative routing, rerouting, and resource allocation step is used to optimize the total bandwidth carried in the network, while allowing 40-Gb/s traffic to be routed on OC-768 incapable links by the proper installation of TDM multiplexors and demultiplexers at some strategic locations in the network. Numerical results reveal the following: 1) the two-phase RMT optimization algorithm provides substantial savings in terms of both the total TDM equipment installed and number of wavelengths used; 2) noticeable enhancements of the bandwidth utilization and the TDM budget are observed when the route-optimization takes into account the transmission quality of the links; and 3) the use of intermediate TDM multiplexing/demultiplexing functions provides substantial savings, in terms of the total number of channels, over the source-splitting scheme.

In this paper, we introduce the routing of multi-rate traffic (RMT) problem that arises in current backbone networks required to carry the new 40 Gb/s traffic streams. The RMT problem is informally defined as the process of finding the best routing which maximizes the total bandwidth carried in the network, for a set of sessions, within a given TDM equipment budget. We propose a two-phase iterative optimization scheme (two-phase RMT). This scheme first obtains a basis solution used in routing 40 Gb/s traffic only on OC-768 capable links without the use of TDM equipment. In the second phase, an iterative routing, re-routing and resource allocation step is used to optimize the total bandwidth carried in the network while allowing 40 Gb/s traffic to be routed on OC-768 incapable links by the proper installation of TDM multiplexors and demultiplexers at some strategic locations in the network. Numerical results demonstrate the performance of the proposed approach on a mesh-type heterogeneous topology.

This paper addresses the placement of multicast nodes in wavelength-routed all-optical networks. This problem is motivated by the expected high cost of optical multicast cross-connects due to fabrication complexity and power considerations. An analytical model for the approximate blocking probability in multicast networks is developed. The blocking performance is used to guide an iterative algorithm, Multicast-ADD, for the placement of multicast nodes. We provide validation of the model and the techniques used. In addition, a simulation study is provided to evaluate the performance of the heuristic. Insights obtained from the simulation results reveal that: (1) only a subset of the nodes (found to be 50%) need to be multicast-capable for acceptable blocking performance; (2) the blocking performance of Multicast-ADD outperforms that of random placement; and (3) employing alternate routing trees is not helpful in the optimization procedure.

We consider networks consisting of optical cross-connects interconnected via fiber optic links and controlled by IP routes. Optical connections are provisioned dynamically and on demand as the need for them arises due to changes in the traffic. We discuss the impact of linear effects such as polarization mode dispersion (PMD) on the design of the control plane. Constrained-routing algorithms as well as signaling protocols are developed which allow for proper label (lambda) and regeneration requests distribution. Both the architecture and the electronic equipment cost are validated, through simulation, using a new WDM-aware version of NS-2 simulator. Simulation results reveal that: (1) the feasibility of the lightpath is greatly affected by the PMD factor, especially for bit-rates exceeding 5Gbit/s; and (2) significant improvement (in terms of cost) can be achieved through intelligent route selection schemes which take into consideration physical characteristics of fiber links. These cost savings are more apparent in networks with non-homogeneous fiber quality.

In this paper, we investigate the multicast routing problem in sparse splitting networks (MR-SSN). The MR-SSN problem is to find a route from the source node of a session to all destinations of the session such that the total number of fibers used in establishing the session is minimized while the multicast capable nodes are evenly distributed throughout the network. We present a heuristic based on Tabu search that requires only one transmitter for the source node and one wavelength for a multicast session in this paper. We test our heuristic on a wide range of network topologies and random sessions and conclude that the difference between our solution and ILP optimal solution in terms of the number of fibers used for establishing a multicast session is within 10% nearly all the time and within 5% in about half of the time.

We investigate the allocation of multicast nodes and formalize it as splitter placement in wavelength-routed networks (SP-WRN) problem. The SP-WRN problem entails the placement of multicast nodes so that the overall network blocking probability is minimized. To gain a deeper insight into the computational complexity of the SP-WRN problem, we define a graph-theoretic version of the splitter placement problem (SPG), and show that even SPG is NP-complete. We develop three heuristics for the SP-WRN problem with different degrees of trade-off between computation time an quality of solution. The first heuristic uses CPLEX, the second heuristic is based on a greedy approach, and the third heuristic employs simulated annealing. Numerical examples demonstrate that: (i) no more than 50% of the cross-connects need to be multi-case capable, and (ii) the iterative simulated annealing heuristic provides fast near-optimal solutions.

This paper addresses the optimal placement of multicast nodes in all-optical networks. An approximate analytical model for the blocking probability in multicast networks is developed. The blocking model is used to guide two heuristics for the placement problem. The two heuristics are: (1) the famous warehouse allocation heuristic (ADD) and (2) simulated annealing.

This paper introduces the optical quality of service (QoS) optimization model for wavelength-routed networks. In the first part of this study we concentrate on power as the main quantitative measure of optical QoS. A mathematical formulation of the problem is presented and heuristic approaches are proposed.

In this paper, we introduce the power-efficient design space for multicast wavelength-routed networks. The power-efficient design space is based on the impact of power on the overall design of wavelength-routed networks. Two cross-connect architectures on this design concept are investigated. One is an existing architecture called splitter-and-delivery (SaD). The other is a new architecture called multicast-only splitter-and-delivery (MOSaD). The MOSaD architecture uses power splitters for multicast connections only, allowing unicast connections to pass without enduring unnecessary power losses. Our cross-connect design provides a strictly nonblocking service for unicast connections while eliminating unnecessary power loss of the SaD cross-connect. Experimental results demonstrate that the MOSaD architecture provides substantial savings in cost and reduction in signal power loss with minimal effects on the blocking performance of the network.

In this paper, we investigate the problem of routing connections in ail-optical networks while allowing for degradation of routed signals by different optical components. To overcome the complexity of the problem, we divide it into two parts. First, we solve the pure RWA problem using fixed routes for every connection. Second, power assignment is accomplished by either using the smallest-gain first (SGF) heuristic or using a genetic algorithm. Numerical examples on a wide variety of networks show that: (a) the number of connections established without considering the signal attenuation was most of the time greater than that achievable considering attenuation; and (b) the genetic solution quality was much better than that of SGF, especially when the conflict graph of the connections generated by the linear solver is denser.