Multicast routing and allocation of wavelengths in a WDM network with splitters and converters (original) (raw)
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Multicast Routing and Wavelength Assignment in WDM Mesh Networks with Sparse Splitting
HAL (Le Centre pour la Communication Scientifique Directe), 2009
In this paper routing and wavelength assignment for supporting multicast traffic is investigated in WDM mesh networks under sparse splitting constrain. This problem is generally solved in two phases respectively with the purpose of minimizing the number of wavelengths required. Alternative routing is first proposed to route each session by pre-computing a set of candidate light-forests. Then wavelength assignment is formulated as a coloring problem by constructing a conflict graph. Potential heuristic algorithms are proposed.
Time-efficient optimal wavelength assignment in optical WDM networks with conversion capability
IEEE Communications Letters, 2006
In wavelength-routed optical networks (WRONs), a wavelength assignment algorithm which can optimally utilize wavelength converters is strongly desired. In this letter, for the first time, we propose a novel graph constructed with groups of available wavelengths, called lambda-runs, to obtain the leastconversion lightpaths easily by applying the shortest-path routing Dijkstra's algorithm. Simulations show that our algorithm is much more scalable than an existing optimal algorithm, and significantly improves the blocking performance, compared to modified first-fit algorithm.
On the routing and wavelength assignment in multifiber WDM networks
IEEE Journal on Selected Areas in Communications, 2004
This paper addresses the problem of routing and wavelength assignment (RWA) in multifiber WDM networks assuming neither a special topology nor wavelength converters. Given a traffic matrix, the number of fibers per link, and the number of wavelengths a fiber can support, we seek to realize the maximum number of connections. We formulate the problem as an integer linear program (ILP), and show that the selected lightpaths by this formulation can indeed be realized by properly configuring the optical switches. An upper bound on the carried traffic can be computed by solving the linear programming (LP) relaxation of the ILP formulation. However, we prove that the bound can be computed exactly by solving a significantly simplified LP, which considers only one wavelength. Consequently, our bound can easily scale to an arbitrarily large number of wavelengths. Although our formulation is path-flow based, we will demonstrate that, even if all, possibly exponentially many, paths are considered, the upper bound can always be computed in polynomial time. Our bound can thus be used as a benchmark against which exact and heuristic techniques are compared. Furthermore, we demonstrate that a simple greedy algorithm provides solutions to the original ILP formulation that are guaranteed to be within (1 − 1 e ) of its optimal solution. As the greedy algorithm considers only one wavelength at a time, it can scale to a large number of wavelengths. Computational results confirm the high efficiency of our proposed algorithm.
IEICE Transactions on Communications, 2010
We propose a scheme of MultiCast Routing and Wavelength Assignment (MC-RWA) to establish light-tree for dynamic multicast session for the Wavelength Division Multiplex (WDM) network by choosing the wavelength that leads to a reduction in blocking probabilities by using a parameter Δ. Δ is defined as the overall reduction of connectivity of the nodes in the network caused by a wavelength assignment process when using a particular wavelength, and we assign wavelength resources to the multicast session by choosing the Δ which leads to smallest reduction in connectivity. Through computer simulation, we show that the proposed scheme has lower blocking probabilities when compared with minimum cost scheme under the condition that wavelength conversion is not allowed.
A Wavelength Assignment Scheme for WDM Networks with Limited Range Wavelength Converters
2006 IEEE International Conference on Communications, 2006
In this paper, we propose a new wavelength assignment scheme that improves the blocking probability of WDM networks that use limited-range wavelength converters. Limitedrange wavelength converters are attractive for wavelength-routed networks given current technology since they offer good utilization of the wavelength resource and improved blocking probability. However, their conversion ranges are limited, the maximum difference between the input and output wavelengths is restricted. Thus, we must take into account the existence of these limitedrange wavelength converters. In our proposed scheme, each connection request is assigned a different wavelength according to its hop number. We tend to use different wavelengths for connection requests with different hop numbers. As a result, we can reduce the blocking probability by two decades compared to simply assigning the shortest available wavelengths. In addition, it allows the number of wavelength converters used in each node to be reduced with almost no degradation in blocking probability. Simulation results show that the proposed scheme can reduce the wavelength converters by about 20%.
Minimum wavelength assignment for multicast traffic in all-optical WDM tree networks
2008 5th International Conference on Broadband Communications, Networks and Systems, 2008
We study the problem of assigning wavelengths to a given set of multicast traffic requests with the objective of minimizing the number of wavelengths used per fiber. We assume that the underlying optical network is a tree and that all-optical networking paradigm is employed. First, we prove that the problem is NP hard even when the underlying network is a simple star or path. Since assigning wavelengths to a given set of unicast traffic requests on star and path networks is easy, this shows that the the multicast wavelength assignment problem is fundamentally harder than the unicast scenario. Next we present GREEDY and SUBTREE-BASED: two simple deterministic algorithms for assigning wavelengths to a given set of multicast traffic requests when the underlying network is a tree with maximum node degree 3 and 4 respectively. Of the two wavelength assignment schemes, GREEDY is a 5 2 -approximation algorithm, and SUBTREE-BASED is an approximation algorithm with approximation ratio 10 3 , 3 and 2 for the cases when the underlying network is a tree with degree 4, 3 and 2, respectively.
Multicasts on WDM all-optical multistage interconnection networks
Proceedings. Eighth International Conference on Parallel and Distributed Systems. ICPADS 2001, 2001
Wavelength-division multiplexing (W D M) optical networks provide huge bandwidth by allowing multiple data streams transmitted simultaneously along the same optical fiber, with each stream assigned a distinct wavelength. A key issue o n W D M optical networks is to minimize the number of wavelengths f o r realizing a routing request. Let W be the number of wavelengths supported by a W D M optical network. For a routing request R which needs 1 wavelengths, i f I 5 W then R can be realized in one round of routing. However, when 1 > W , multiple rounds of routing f o r R are required. I n this case, it is important t o minimize the number of routing rounds. Multicast is to transmit a data stream f r o m one input t o multiple outputs (one-to-many), a fundamental communication pattern in many applications. I n this paper, we study the problem of minimizing the number of wavelengths and the number of routing rounds f o r realizing a set R = { (u , v) } of multicasts, where each output v receives a data stream f r o m exactly one input U , o n the n-dimensional W D M all-optical multistage interconnection networks (MINs). For the network with wavelength converters, we show that any set of multicasts can be realized by 2 r (n-1) f (k + ') 1 wavelengths in k rounds of routing. For one round of routing, the upper bound 2r(n-1)f21 is tight to the lower bound. W e also give algorithms f o r multicasts o n the network without wavelength converters. Computer simulation results show that any set of multicasts can be realized in at most two rounds of routing o n the network with practical size.
Analysis of sparse-partial wavelength conversion in wavelength-routed WDM networks
IEEE INFOCOM 2004, 2004
Wavelength conversion has been shown as one of the key techniques to improve blocking performance in a wavelength-routed all-optical network. Given that wavelength converters nowadays remain very expensive, how to make effective use of a limited number of wavelength converters becomes an important issue. In this paper, we propose Sparse-Partial Wavelength Conversion (SPWC) network architecture with the inherent flexibility that can facilitate network carriers to migrate the optical backbone to support wavelength conversion. We demonstrate that this network architecture can significantly save the number of wavelength converters, yet achieving excellent blocking performance. Theoretical and simulation results indicate that, the performance of a wavelength-routed WDM network with only 1-5% of wavelength conversion capability is very close to that with Full-Complete Wavelength Conversion capability.
Light-hierarchy: the optimal structure for multicast routing in WDM mesh networks
Based on the false assumption that multicast incapable (MI) nodes could not be traversed twice on the same wavelength, the light-tree structure was always thought to be optimal for multicast routing in sparse splitting Wavelength Division Multiplexing (WDM) networks. In fact, for establishing a multicast session, an MI node could be crosswise visited more than once to switch a light signal towards several destinations with only one wavelength through different input and output pairs. This is called Cross Pair Switching (CP S). Thus, a new multicast routing structure light-hierarchy is proposed for alloptical multicast routing, which permits the cycles introduced by the CP S capability of MI nodes. We proved that the optimal structure for minimizing the cost of multicast routing is a set of light-hierarchies rather than the light-trees in sparse splitting WDM networks. Integer linear programming (ILP) formulations are developed to search the optimal light-hierarchies. Numerical results verified that the light-hierarchy structure could save more cost than the light-tree structure.
WDM Optical Networks: A Complete Design
Journal of Communication and Information Systems, 2005
Different integer linear programming (ILP) have been proposed for design of optical networks. The traditional approaches divide design into two separate problems: virtual topology design (VTD), in which best connections among nodes are derived from traffic demand; and routing-and-wavelength assignment (RWA), in which physical paths are accommodated in the physical topology to support the requested connections. We propose an iterative linear programming approach to solve both problems jointly under multiple objectives such as congestion avoidance, fiber load and wavelength pool minimization. The solution of the VTD problem generates a request for a set of paths to be supplied by the physical topology. Physical paths are then allocated in order to minimize some objective functions that are akin to a linear programming formulation. If no feasible solution is found, VTD program supplies a next best solution until all paths are routed. Some objective functions (e.g. maximum fiber load) may be oblivious to the persistence of cycles in the final solution, which may even be dismembered from the source-to-destination link sequence. These anomalies may be eliminated by re-optimizing the solution using the total number of hops as a new objective function, subject to the minimal value of maximum fiber load that was determined in the previous optimization step. The final design phase is the assignment of wavelengths to paths or sections thereof, making best use of available wavelength conversion resources. Our formulation allows for any kind (partial or full, sparse or ubiquitous) of wavelength conversion and limited number of converters, thus providing a tool for the allocation of conversion resources in the network. Index Termsoptical networks; lightpath routing; virtual and physical topology; wavelength conversion.