In this article we assess the economic gain obtained by introducing multi-granularity switching optical cross-connects (MG-OXCs) in an optical transport network. An MG-OXC is an equipment able to switch wavelengths, to aggregate (disaggregate) wavelengths into (from) groups of wavelengths called wavebands and to switch wavebands. We evaluate the economic gain by comparing the cost of instantiating (i.e., provisioning) a set of Scheduled Lightpath Demands (SLDs) in a network of wavelength-switching optical cross-connects (WXCs) against the cost of instantiating them in a network of MG-OXCs. We formulate the problems of instantiating SLDs in both a network of WXCs and a network of MG-OXCs as two combinatorial optimization problems and compute approximate solutions to these problems using Tabu Search (TS) based algorithms. Finally, we define a method to determine the conditions (traffic distribution, cost of switching matrices and ports, etc.) under which a network of MG-OXCs is more economical than a network of WXCs

Virtual concatenation (VCAT) is an SDH/SONET network functionality recently standardized by the ITU-T. VCAT provides the flexibility required to efficiently allocate network resources to Ethernet, fiber channel, ESCON and other important data traffic signals. The aim of this paper is to quantify the savings in network resources provided by VCAT, with respect to contiguous concatenation (CCAT), in SDH/SONET mesh transport networks bearing protected scheduled connection demands (SCDs). We define mathematical models to quantify the add/drop and transmission resources required to instantiate a set of protected SCDs in either a VCAT-capable or a CCAT-capable network. Quantification of transmission resources requires a routing and slot assignment (RSA) problem to be solved. We formulate the RSA problem in VCATand CCAT-capable networks as two different combinatorial optimization problems: RSAv and RSAc, respectively. Protection of the SCDs is considered in the formulations using a shared backup path protection (SBPP) technique. We propose a simulated annealing (SA) based meta-heuristic algorithm to compute approximate solutions to these problems (i.e., solutions whose cost is close to the cost of the optimal ones). The gain in transmission resources and the cost structure of add/drop resources making VCAT-capable networks more economical are analyzed for different realistic traffic types (ESCON, GbE, fibre channel, voice).

We present algorithms that compute the routing and wavelength assignment (RWA) for scheduled lightpath demands in a wavelength-switching mesh network without wavelength conversion functionality. Scheduled lightpath demands are connection demands for which the setup and teardown times are known in advance. We formulate separately the routing problem and the wavelength assignment problem as spatio-temporal combinatorial optimization problems. For the former, we propose a branch and bound algorithm for exact resolution and an alternative tabu search algorithm for approximate resolution. A generalized graph coloring approach is used to solve the wavelength assignment problem. We compared the proposed algorithms to an RWA algorithm that sequentially computes the route and wavelength assignment for the scheduled lightpath demands.

We investigate the problem of routing a set of lightpath demands for which the start and end dates may be planned. We call this type of requests foreseeable lightpath demands or FLDs. In a transport network, FLDs correspond, for example, to clients' requests for pre-provisioned bandwidth capacity such as fixed-bandwidth pipes for bulk data transfers during the night, extra VPN bandwidth used during peak office working time, etc. Since in some cases the FLDs are not all simultaneous in time, it is possible to reuse physical resources to realize time-disjoint demands. We propose a routing algorithm that takes into account this property to minimize the number of required WDM channels in the physical links of the network. The gain (in term of saved resources) provided by the algorithm, when compared to a shortest path routing strategy, depends both on the spatial and temporal structure of the set of traffic demands and on the structure of the physical network. The routing problem is formulated as a combinatorial optimization problem. A tabu search meta-heuristic algorithm is developed to solve this problem.

Presents new search algorithms to detect the occurrences of any pattern from a given pattern set in a text, allowing in the occurrences a limited number of spurious text characters among those of the pattern. This is a common requirement in intrusion detection applications. Our algorithms exploit the ability to represent the search state of one or more patterns in the bits of a single machine word and to update all the search states in a single operation. We show analytically and experimentally that the algorithms are able of rapidly searching large sets of patterns, allowing a large number of spurious characters, yielding about a 75-fold improvement over the classical algorithm.