Oblivious Routing Algorithm under Hose Model for WDM Mesh Network

The problem of routing bandwidth guaranteed paths in wavelength-routed, WDM optical mesh networks is explored. A WDM mesh network offers great flexibility in dynamically reconfiguring the optical core to match the IP layer demands. In this paper, we argue that IP subnets can limit the reconfigurability potential of the WDM mesh network. We show that finding the shortest IP-hop path, normally admitting a straightforward polynomial solution on the WDM mesh, is NP-hard in the presence of subnets. We propose a new algorithm called MobiTwist that finds the optimal shortest path when accounting for subnets. We also observe that subnets impose a routing penalty by forcing longer paths for bandwidth demands. Consequently, they create a trade-off between lower network efficiency if subnets are honored (due to longer paths) or, an upfront overhead of dynamically changing subnets to derive shorter paths. We propose the MobiFlex algorithm that attempts to achieve a balance by finding the shortest path given an upper limit on the number of subnet violations acceptable. The inherent hardness of the routing problem due to subnets precludes a solution with low worst-case complexity. However, we present performance results that show that both the algorithms proposed are extremely efficient in routing demands, and in practice, do so in polynomial time.

Multicommodity flow models are commonly used to formulate the logical topology design (LTD) problem and the lightpath routing (LR) problem as mixed integer linear programming (MILP) problems. In general, MILP formulations are intractable even for relatively small networks due to the combinatorial complexity of the problem. In this paper we propose improvements to these models and a method to solve the LTD and the LR problems in a combined manner. The interest is two fold: firstly, by tackling the two problems with separate models, problem instances of realistic size (up to 14 nodes in this paper) can be dealt with. Furthermore, different combinations of optimization models and objective functions can be investigated in a modular manner. Secondly, the mechanisms proposed to combine the problems allow to keep track of the global design problem when solving each individual step.

We study oblivious routing in which the packet paths are constructed independently of each other. We give a simple oblivious routing algorithm for geometric networks in which the nodes are embedded in the Euclidean plane. In our algorithm, a packet path is constructed by first choosing a random intermediate node in the space between the source and destination, and then the packet is sent to its destination through the intermediate node. We analyze the performance of the algorithm in terms of the stretch and congestion of the resulting paths. We show that the stretch is constant, and the congestion is near optimal when the network paths can be chosen to be close to the geodesic lines that connect the end points of the paths. We give applications of our general result to the mesh topology and uniformly distributed disc graphs. Previous oblivious routing algorithms with near optimal congestion use many intermediate nodes and do not control the stretch.

Feature Issue on High Availability in Optical NetworksA resource provisioning method for optical backbone networks running IP or multiprotocol label switching (MPLS) is presented. Trunk and hose models are well-known bandwidth provisioning models, but both have significant disadvantages if applied to large-scale networks. The management complexity of the trunk model highly increases with the size of the network, and the bandwidth efficiency of the hose model is often excessively low. We propose an intermediate solution between the hose and trunk models. By dividing the network into clusters and using a cluster-based traffic description, an appropriate equilibrium can be found between management complexity and overprovisioning.

This paper compares the performances of optimal routing as yielded by the pipe, hose, and intermediate models. The pipe model, which is specified by the exact traffic matrix, provides the best routing performance, but the traffic matrix is difficult to measure and predict accurately. On the other hand, the hose model is specified by just the total outgoing/incoming traffic from/to each node, but it has a problem in that its routing performance is degraded compared to the pipe model, due to insufficient traffic information. The intermediate model, where the upper and lower bounds of traffic demands for source-destination pairs are added as constraints, is a construction that lies between the pipe and hose models. The intermediate model, which lightens the difficulty of the pipe model, but narrows the range of traffic conditions specified by the hose model, offers better routing performance than the hose model. An optimal-routing formulation extended from the pipe model to the intermediate model can not be solved as a regular linear programming (LP) problem. Our solution, the introduction of a duality theorem, turns our problem into an LP formulation that can be easily solved. Numerical results show that the network congestion ratio for the pipe model is much lower than that of hose model. The differences in network congestion ratios between the pipe and hose models lie in the range from 27% to 45% for the various network topologies examined. The intermediate model offers better routing performance than the hose model. The intermediate model reduces the network congestion ratio by 34% compared to the hose model in an experimental network, when the upper-bound and lower-bound margins are set to 25% and 20%, respectively.

This paper proposes an efficient and scalable dynamic traffic grooming algorithm suitable for large WDM mesh networks by limiting the zone where lightpaths for new connection requests are searched. Besides, in order to maintain the multi-hop grooming flexibility, the searching zone can be dynamically enlarged according to the availability of groomable existing or new lightpaths and the physical connectivity between network nodes. We develop a mathematical model to estimate the possibility that a node connects the source and destination when included to enlarge the searching zone, and to ensure that the selected lightpath is resource-efficient. Simulation results demonstrate that the proposed algorithm can significantly reduce the computations and improve the blocking performance.

Wireless Mesh Networks offer a high-performance and low-cost solution to last-mile broadband Internet access. Routing and Scheduling play a critical role in determining the performance of a wireless mesh network. Efficiency of Routing and Scheduling algorithms is highly dependent on the availability of accurate traffic information. In this paper, we predict network traffic based on past data using ARIMA model, and provide that input to the routing and scheduling algorithm. Joint routing and scheduling results in significant performance improvement over the routing only algorithms. So, we provide predicted network traffic information to a Joint routing and scheduling algorithm known as Traffic Oblivious Routing and Scheduling. Traffic Oblivious Routing and Scheduling algorithm optimizes the worst case performance under traffic uncertainty but when accurate traffic information is available to the algorithm, its performance is enhanced. In the Traffic Oblivious Routing and Scheduling algorithm, computing the routing and the scheduling values is a one time overhead. In this paper, we present a system where we predict network traffic information using past data, then use the predicted information to formulate the input for the Traffic Oblivious routing and scheduling algorithm and finally we evaluate the performance of the algorithm using simulations.

A novel robust routing algorithm for multi-granularity connection requests in wavelength division multiplexing mesh networks

In wavelength routed optical networks, each optical link is capable of carrying traffic using several wavelengths and each wavelength as well as lightpath support traffic in the Gbps range. On the other hand, the traffic requested by individual connection is still in the Mbps range. Therefore, to utilize the network resources (bandwidth, transceivers, etc.) effectively, several low-speed traffic streams have to be efficiently groomed or multiplexed into a high-speed lightpath. In this work, we have investigated the traffic grooming problem with the objective of maximizing the network throughput for wavelength routed mesh networks. We have proposed an algorithm to handle general multi-hop static traffic grooming based on genetic algorithm. The efficacy of our approach has been established through extensive simulation on different sets of traffic demands under different network topologies and compared with an efficient heuristics proposed in the literature.

Two new algorithms for worm-hole routing in the hypercube are presented. The first hypercube algorithm is adaptive, but non-minimal in the sense that some derouting is permitted. Then another deadlock-free adaptive worm-hole based routing algorithm for the hypercube interconnection is presented which is minimal. Finally some well-known worm-hole algorithms for the hypercube were evaluated together with the new ones on a hypercube of 2/sup 10/ nodes. One oblivious algorithm, the Dimension-Order, or E-Cube routing algorithm (W. Dally, C. Seitz, 1987) was tried. In addition, three partially adaptive algorithms were considered: the Hanging algorithm (Y. Birk, P. Gibbons, D. Soroker, J. Sanz, 1989 and S. Konstantinidou, 1990), the Zenith algorithm (S. Konstantinidou, 1990), and the Hanging-Order algorithm (G.-M. Chia, S. Chalasani, C.S. Raghavendra, 1991). Finally, a fully adaptive minimal algorithm presented independently by L. Gravano, G. Pifarre, S.A. Felperin and J. Sanz (1991) and J. Duato was tried. This algorithm allows each message to choose adaptively among all the shortest paths from its source to its destination. Only four virtual channels per physical link are needed to achieve this. This technique is referred to as Fully. The results obtained show that the two new algorithms are good candidates as a choice for worm-hole routing in the hypercube network.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Data networking now plays a major role in everyday life and new applications continue to appear at a blinding pace. Yet we still do not have a sound foundation for designing, evaluating and managing these networks. This book covers topics at the intersection of algorithms and networking. It builds a complete picture of the current state of research on Next Generation Networks and the challenges for the years ahead. Particular focus is given to evolving research initiatives and the architecture they propose and implications for networking. Topics: Network design and provisioning, hardware issues, layer-3 algorithms and MPLS, BGP and Inter AS routing, packet processing for routing, security and network management, load balancing, oblivious routing and stochastic algorithms, network coding for multicast, overlay routing for P2P networking and content delivery. This timely volume will be of interest to a broad readership from graduate students to researchers looking to survey recent research its open questions.

We study the provisioning of virtual private network (VPN) service over WDM optical networks. For this purpose, we investigate the blocking performance of the hose model versus the pipe model for the provisioning. Two techniques are presented: an analytical queuing model and a discrete event simulation. The queuing model is developed from the multirate reduced-load approximation technique. The simulation is done with the OPNET simulator. Several experimental situations were used. The blocking probabilities calculated from the two approaches show a close match, indicating that the multirate reduced-load approximation technique is capable of predicting the blocking performance for the pipe model and the hose model in WDM networks. A comparison of the blocking behavior of the two models shows that the hose model has superior blocking performance as compared with pipe model. By and large, the blocking probability of the hose model is better than that of the pipe model by a few orders of magnitude, particularly at low load regions. The flexibility of the hose model allowing for the sharing of resources on a link among all connections accounts for its superior performance.

Past approaches to routing in mesh networks either (i) do not account for the MAC-layer interactions between the links in a tractable manner, or (ii) are agnostic to load-balancing across gateways. Our answer to these problems is MaLB (MAC-aware and Load Balanced routing algorithm), a greedy, tractable, and distributed mesh routing algorithm. Since the underlying objective function has high combinatorial complexity, MaLB uses a greedy approach. MaLB finds an optimum routing forest (union of trees rooted at the gateways) by taking into account MAC-layer interaction between links, as well as optimum multi-hop association of mesh nodes to gateways. MaLB builds on top of ETP (Expected Through-Put), a recently proposed MAC-aware routing metric. We also propose a low complexity variant of MaLB called LB (Load Balanced routing algorithm) which performs load balancing in a MAC-agnostic manner. MaLB performs especially well in networks with skewed topologies that result from unplanned mesh network deployment, as well as in the presence of gateway failures. Simulations with an enhanced version of ns-2 show that MaLB results in up to 60% higher throughput than a shortest path algorithm with ETX (Expected Transmission Count). Furthermore, MaLB results in up to 30% improvement over the LB algorithm, as well as a shortest path algorithm with ETT (Expected Transmission Time).

We consider optical layer monitoring schemes for fast link failure localization in WDM mesh networks. A new concept monitoring trail (m-trail) is proposed. It differs from the existing monitoring cycle (m-cycle) concept by removing the cycle constraint. As a result, m-trail provides a more flexible all-optical monitoring structure which includes simple, non-simple m-cycles and open trails as special cases. Aiming at minimizing the total monitoring cost, an integer linear program (ILP) is formulated for m-trail design. Numerical results show that the m-trail based scheme significantly outperforms its m-cycle based counterpart.

In wavelength routed optical networks, the number of wavelength channels is limited due to several constraints and each wavelength as well as each lightpath support traffic in the Gbps range. On the other hand, the traffic requested by an individual connection is still in the Mbps range. Therefore, to utilize the network resources (such as bandwidth and transceivers) effectively, several low-speed traffic streams have to be efficiently groomed or multiplexed into one or more high-speed lightpaths. The grooming problem of a static demand is considered as an optimization problem. In this work, we have investigated the traffic grooming problem with the objective of maximizing the network throughput for wavelength-routed mesh networks and map this problem to the clique partitioning problem. We have proposed an algorithm to handle general multi-hop static traffic grooming based on the clique partitioning concept. The efficiency of our approach has been established through extensive simulation on different sets of traffic demands with different bandwidth granularities for different network topologies and compared the approach with existing algorithms.