Virtual Path Concept Research Articles

The use of multiple objective genetic algorithm in self-healing network

Abstract This paper presents a genetic algorithm based method to solve the capacity and routing assignment problem arising from the design of self-healing networks using the virtual path (VP) concept. Past research has revealed that the pre-planned backup protection method and the path restoration scheme can provide a good compromise between the reserved amount of spare capacity and the failure restoration time. Our aim is to minimize the sum of working and backup capacity usage while a set of customer traffic demands can still be satisfied and the traffic is 100% restorable under a single point of failure. A searching technique, genetic algorithm (GA), is proposed to perform this optimization. There are several advantages of using a genetic algorithm which includes lower computational cost in reaching a reasonably good virtual path routing scheme and less complex mathematical formulation. Another technique, exhaustive-like search, is also utilized in order to compare their results. Moreover, we implement two restoration schemes for multicast connections, link restoration and path restoration, for comparison purposes. Most of the past research mainly focused on the unicast traffic, but our method works for both unicast traffic and multicast traffic.

Aggregated bandwidth allocation: investigation of performance of classical constrained and genetic algorithm based optimisation techniques

We consider a high speed integrated services network, and investigate compare and contrast the performance of two algorithms for solving the Aggregated Bandwidth Allocation (BA) problem. The algorithms we focus our attention are: (1) a classical constrained optimisation (CCO) algorithm and (2) a constrained optimisation Genetic Algorithm (GA). We adopt the Virtual Path concept for Asynchronous Transfer Mode networks as an example, but expect the findings to be equally applicable for other aggregated BA problems, such as in networks using Multiprotocol Label Switching. We define a fair multiobjective criterion for maximisation of network throughput, based on a probability (density) function for bandwidth demand. We convert to single optimisation problem and study network topologies involving varying number of nodes. We compare throughput, fairness and time complexity of GA-BAVP and CCO-BAVP. The results on maximising the throughput obtained with GA-BAVP and CCO-BAVP are in close agreement, however, when considering fairness GA-BAVP outperforms CCO-BAVP especially for more complex topologies. Convergence of the two algorithms appears similar, with GA-BAVP outperforming CCO-BAVP in initial stages, and vice versa for longer time scales. However, as problem complexity increases the solution time for the GA does not increase as fast as the CCO algorithm. A hybrid scheme is also introduced, combining the benefits of both algorithms. It exhibited better overall convergence rate but the same solution as CCO-BAVP. More work is needed to investigate the usefulness of GAs in larger network topologies, as well as to multiobjective BA problems.

A virtual path routing algorithm for ATM networks based on the equivalent bandwidth concept

The coexistence of a wide range of services with different quality of service (QoS) requirements in today's networks makes the efficient use of resources a major issue. It is desirable to improve network efficiency by adaptively assigning resources to services that have different bandwidth demands. Implementing Broadband Integrated Services Digital Networks (B-ISDN) therefore requires a network control scheme that can handle bursty traffic with unexpected fluctuations. The Asynchronous Transfer Mode (ATM) technology provides this flexibility by virtualizing network resources through the use of the virtual path (VP) concept. In this study, a method for designing a VP-based ATM network is proposed. The developed heuristic design algorithm applies VP routing and separation techniques to minimize the maximum link utilization under processing delay constraints. Each link is assigned a weight that reflects its current utilization. Using these weights, the VPs on highly utilized links are rerouted to less congested physical paths. The algorithm makes use of the equivalent bandwidth concept, which provides an efficient method to estimate capacity requirements of connection requests such that QoS requirements are met. The quality of the solutions achieved by the proposed method is compared to several competitors under varying network topologies and traffic conditions. The observations on the algorithm performance show that the developed method is able to facilitate an efficient use of network resources through the introduction of VPs.

Some approaches to solving a multihour broadband network capacity design problem with single-path routing

In this paper, we consider solution approaches to a multihour combined capacity design and routing problem which arises in the design of dynamically reconfigurable broadband communication networks that uses the virtual path concept. We present a comparative evaluation of four approaches, namely: a genetic algorithm, a Lagrangian relaxation based subgradient optimization method, a generalized proximal point algorithm with subgradient optimization, and, finally, a hybrid approach where the subgradient based method is combined with a genetic algorithm. Our computational experience on a set of test problems of varying network sizes services) shows that the hybrid approach often is the desirable choice in obtaining the minimum cost network while the genetic algorithm based approach has the most difficulty in solving large scale problems.

An improved scheme for self-healing in ATM networks

Broadband networks based on ATM technology can carry a large volume of data and can support diverse services like audio, video, and data uniformly. The reliability and availability levels provided by such networks should be very high. Self-healing is an elegant concept in this direction to provide highly reliable networks. A self-healing network can detect failures such as link/node failures and reroute the failed connections automatically using distributed control mechanisms. In this paper, we consider link and node failures including the VP terminating nodes unlike Kawamura and Tokizawa (Self-healing in ATM networks based on virtual path concept, IEEE Journal on Selected Areas in Communications 12 (1) (1994) 120–127). We present here an improved scheme for self-healing in ATM networks based on the concept of backup VPs. The problems we address are: (i) self-healing scheme; and (ii) backup VP routing. Two issues are addressed in the self-healing scheme: (i) backup VP activation protocol; and (ii) dynamic backup VP routing. We propose a new backup VP activation protocol which uses a VC packing strategy which allows the fast and prioritized restoration of critical VCs that were carried by failed VPs. We also propose a distributed dynamic backup VP routing algorithm which reduces the resource contention that may occur when multiple source–destination pairs contend for the routes simultaneously. The objective of the backup VP routing problem is to find a backup VP for each of the working VPs so that the cost of providing the backup is minimized. We propose a heuristic based solution for the backup VP routing problem using the concept of minimum cost shortest paths. We conducted simulation experiments to evaluate the performance of the proposed schemes. The results show that the proposed schemes are effective. Comparison of the results with those of the earlier schemes (R. Kawamura, I. Tokizawa, Self-healing in ATM networks based on virtual path concept, IEEE Journal on Selected Areas in Communications 12 (1) (1994) 120–127; C.J. Hou, Design of a fast restoration mechanism for virtual path-based ATM networks, Proceedings of IEEE INFOCOM’97, Kobe, Japan, April 1997) shows that the proposed schemes perform better.

Bandwidth-demand prediction in virtual path in ATM networks using genetic algorithms

The concept of Virtual Paths (VP) is a powerful technique to improve the transmission efficiency in ATM networks. Transmission efficiency can be improved by dynamically changing the bandwidths of the VPs, based on the demand. Intelligent controllers, which predict bandwidth-demand patterns to enable better VP management, have the potential to revolutionize ATM network performance. We present a scheme based on the Evolutionary Genetic Approach to predict the bandwidth-demand patterns in VPs. The efficiency of this approach, quantified in terms of the Degree of Learning (DoL), is evaluated through simulation and the results are presented.

Restoration strategies and spare capacity requirements in self-healing ATM networks

This paper studies the capacity and flow assignment problem arising in the design of self-healing asynchronous transfer mode (ATM) networks using the virtual path concept. The problem is formulated here as a linear programming problem which is solved using standard methods. The objective is to minimize the spare capacity cost for the given restoration requirement. The spare cost depends on the restoration strategies used in the network. We compare several restoration strategies quantitatively in terms of spare cost, notably: global versus failure-oriented reconfiguration, path versus link restoration, and state-dependent versus state-independent restoration. The advantages and disadvantages of various restoration strategies are also highlighted. Such comparisons provide useful guidance for real network design. Further, a new heuristic algorithm based on the minimum cost route concept is developed for the design of large self-healing ATM networks using path restoration. Numerical results illustrate that the heuristic algorithm is efficient and gives near-optimal solutions for the spare capacity allocation and flow assignment for tested examples.

A design of self-healing ATM networks based on backup virtual paths

Broadband network will support a variety of services such as voice, video, data and image with different traffic characteristics and different qualities of service in integrated environment. Asynchronous transfer mode (ATM) network techniques have been actively studied with the goal of realizing B-ISDN. ATM network will provide the infrastructure for B-ISDN and offer the benefit of enhanced flexibility when the virtual path (VP) concept is adopted. One of the most important issues in B-ISDN is the increased level of network survivability. The backup VP scheme prepares a preassigned backup VP before a failure occurs. A backup VP can be assigned between any pair of nodes on a VP route. The backup route is link disjoint from the original path to avoid the simultaneous failure of both the original and the backup VP. In this paper, a self-healing VP network design is considered to find the configuration of the backup VP such that the cost of required spare capacity is minimized.We propose a design of self-healing ATM virtual path (VP) networks based on backup VP. The backup VP is a preassigned virtual path to restore the traffic after a network failure. It is known that the self-healing scheme based on the backup VP is simple, fast and easy to implement. Given a set of bandwidth requirements and original routes for target demands, the design is to find the backup route of each traffic demand such that the cost of total spare bandwidth, which is required for each physical link to restore the services, is minimized. The problem is formulated as an integer linear program. Based on the property that a common backup VP of any two distinct traffic demands saves the required bandwidth, an initial and two improvement heuristics are proposed. Computational experiments show that the proposed procedure provides solutions the gap of which are less than 11% compared to optimal solutions.

Bandwidth allocation of virtual paths using neural-network-based genetic algorithms

The concept of virtual paths has become the key technology in ATM networks. A control scheme based on genetic algorithms and neural networks is proposed and applied to the bandwidth allocation of virtual paths in ATM networks. The proposed control scheme is capable of selecting adaptively optimal step sizes of virtual paths according to the traffic characteristics and network environment. As the optimisation problem is constrained, traditional genetic algorithms are no longer applicable to this problem. The authors propose the masked genetic algorithms with seeds (MGAS) to solve the optimisation problem. Simulation results demonstrate the superiority of the MGAS algorithm. To achieve better performance, the relationships among the QOS measures, the evaluation of seed scores, and the selection of relearning data records are discussed. Finally, a simplified control scheme is proposed to reduce not only the complexity of the neural networks but also the processing time.

Optimal Communication Algorithms for Heterogeneous Computing over ATM Networks

We present efficient algorithms for designing optimal collective communication primitives for cluster-based heterogeneous computing across Asynchronous Transfer Mode (ATM) networks. The virtual path (VP) concept is known to be a powerful transport mechanism for ATM networks. In many parallel processing applications, the potential communication pattern is known in advance. We then seek to find an optimal set of virtual paths to realize the communication pattern, such that the communication overhead of the parallel processing application is minimized, and at the same time, the extent to which the other data traffic in the network is affected by the data traffic generated by the parallel processing application is also minimized.We consider the following four collective communication problems that occur frequently in parallel computation:one-to-all broadcast,all-to-all broadcast,one-to-all scatter, andall-to-all scatter. We formulate these problems as combinatorial optimization problems of finding a system of virtual path routes in networks, with the objectives of minimizing the path length, the link congestion, and the node copy load. We consider two cases of data sources, namely homogeneous and heterogeneous. For the case ofhomogeneous sources, we presentpolynomial-timealgorithms for the problems of one-to-all broadcast, all-to-all broadcast, and one-to-all scatter, by converting these problems to the maximum-flow problems. For the case ofheterogeneous sources, we show that the problems of all-to-all broadcast, one-to-all scatter, and all-to-all scatter are allNP-complete. Finally, we present novelrandomizedalgorithms for these problems, and show that with high probability these algorithms yield good solutions in the sense that the objective functions yield values close to the optimums. The randomized algorithms can also be used to design near-optimummulticastcommunication primitives. These randomized algorithms make use of linear programming and are easy to implement, which makes them a potential candidate for practical implementations, even for very large networks.

Models for network design, servicing and monitoring of ATM networks based on the virtual path concept

Virtual Path (VP) concept has gained attention in terms of effective deployment of ATM networks for wide-area environment. In this paper, we present models and algorithms for network design and management of ATM networks based on virtual path concept from a network planning perspective. Our approach is based on statistical multiplexing of traffic within a traffic class by using a virtual path for the class and deterministic multiplexing of different virtual paths, and on providing dynamic bandwidth and reconfigurability through virtual path concept depending on traffic load during the course of the day. For some realistic example networks, we observe that considering network dynamism through variation of traffic during the course of a day by doing dynamic bandwidth and virtual path reconfiguration can save between 10 to 14% in network design costs compared to a static network based on maximum busy hour traffic.

Deterministic algorithm for VP assignment in ATM networks

Virtual Path (VP) assignment is an important resource management activity in ATM networks. By using the VP concept, the logical layout of the network can be administered to minimize the total network cost to the provider. We formulate the VP assignment problem as a constrained optimization problem; the objective function to be minimized reflects processing/control costs at nodes and transmission costs between nodes. The blocking probability quality of service (QoS) requirements and overall throughput of the network are taken into consideration in the solution process as constraints. Since the solution space is complex, we develop a deterministic, iterative heuristic algorithm to reach a ‘near-optimal’ VP configuration for a given physical network and traffic demand. The Multi-Rate Loss Network model is used in the calculation of connection-level blocking probabilities. Results for static connection-routing are presented, for various forms of the objective function and constraints.

Resource management with virtual paths in ATM networks

A virtual path connection (VPC) is a labelled path which can be used to transport a bundle of virtual channel connections (VCCs) and to manage the resources used by these connections. The virtual network is organized as a collection of VPCs which form a VPC, or logical, overlay network. If the VPCs are permanent or semi-permanent and have reserved capacity, establishing new VCCs requires simple connection admission decisions at the VPC terminators of existing VPCs. This would enable faster connection establishment since transit nodes are not involved in the connection setup. The virtual path concept also allows the possibility of segregating traffic types according to quality of service requirements. However, the extent to which VPC provisioning is able to improve network efficiency is dependent on the resource management decisions that determine the VPC topology and capacity allocations. The article surveys resource management using virtual paths in an ATM network. Of interest are techniques which modify the VPC topology and capacity assignments in order to adapt to changing traffic conditions and possible network failures. The resource management activities employed to facilitate such adaptation can be categorized by the timescale on which they operate. On the shortest timescale are strategies for dynamically making minor changes to the VPC topology or capacity assignments. On a somewhat longer timescale are strategies for making more widespread modifications to the VPC overlay network. This would be appropriate for traffic changes based on time of day and for recovering from network failures. Finally, on an even longer timescale, strategies may be employed to design a general VPC overlay network, to be used at startup or after major network upgrades. Solutions to VPC resource management for each of these timescales are discussed.

Multi-hour, multi-traffic class network design for virtual path-based dynamically reconfigurable wide-area ATM networks

The virtual path (VP) concept has been gaining attention in terms of effective deployment of asynchronous transfer mode (ATM) networks in recent years. In a recent paper, we outlined a framework and models for network design and management of dynamically reconfigurable ATM networks based on the virtual path concept from a network planning and management perspective. Our approach has been based on statistical multiplexing of traffic within a traffic class by using a virtual path for the class and deterministic multiplexing of different virtual paths, and on providing dynamic bandwidth and reconfigurability through virtual path concept depending on traffic load during the course of the day. In this paper, we discuss in detail, a multi-hour, multi-traffic class network (capacity) design model for providing specified quality-of-service in such dynamically reconfigurable networks. This is done based on the observation that statistical multiplexing of virtual circuits for a traffic class in a virtual path, and the deterministic multiplexing of different virtual paths leads to decoupling of the network dimensioning problem into the bandwidth estimation problem and the combined virtual path routing and capacity design problem. We discuss how bandwidth estimation can be done, then how the design problem can be solved by a decomposition algorithm by looking at the dual problem and using subgradient optimization. We provide computational results for realistic network traffic data to show the effectiveness of our approach. We show for the test problems considered, our approach does between 6% to 20% better than a local shortest-path heuristic. We also show that considering network dynamism through variation of traffic during the course of a day by doing dynamic bandwidth and virtual path reconfiguration can save between 10% and 14% in network design costs compared to a static network based on maximum busy hour traffic.

Self-healing virtual path architecture in ATM networks

ATM network techniques have been actively researched and developed with the goal of realizing B-ISDN. ATM networks can transport signals of various services efficiently and economically, and offer the benefit of enhanced flexibility if the virtual path (VP) concept is adopted. Therefore, the ATM network will provide the infrastructure for B-ISDN. One of the most important themes in B-ISDN is the increased level of network reliability required to to match the high volume of data transmission that will be incurred by the information society and the mission critical nature of such data. The authors summarize self-healing network (SHN) schemes they have developed, and discuss problems that must be solved to realize SHN. >

Two-level dynamic step sizes of virtual paths on bandwidth allocation in ATM networks

The virtual path concept has been proposed as the key technique in improving the transmission efficiency in ATM networks. Changing the bandwidth of a virtual path, by a step at a time, has been shown to successfully enhance the transmission efficiency compared to the fixed bandwidth scheme. Therefore how to appropriately select a step size which causes a trade-off between the transmission efficiency and the normalised processing load, becomes an important issue. The authors propose a flexible and effective bandwidth control algorithm, which is capable of dynamically selecting a proper step size according to traffic types, network conditions, and the bandwidth-demand factor of each traffic type. Performance measures of the network, using this dynamic bandwidth-allocation scheme are analysed. Two examples are provided for illustration. The first shows that the proposed algorithm is capable of improving the transmission efficiency, even compared to the scheme with optimal fixed step size. The other shows that the normalised processing loads of both traffic types are significantly reduced without degradation in transmission efficiency.

Adaptive virtual path capacity control in multimedia ATM networks

AbstractThe Virtual Path concept has several beneficial features to construct an economical and efficient Asynchronous Transfer Mode (ATM) network. The Virtual Path capacity control technique can increase network flexibility and improve transmission efficiency through statistical sharing of facilities.This paper presents an adaptive virtual path capacity control method which maximizes transmission efficiency under the condition of limited processing load. Evaluation shows that the proposed method successfully improves network transmission efficiency with a slight increase in processing load compared to the fixed virtual path capacity scheme.

Self-healing ATM networks based on virtual path concept

This paper proposes self-healing network techniques suitable for ATM networks in order to realize a high-reliablity B-ISDN. First, the characteristics of the virtual paths (VP) and their influence on failure restoration are discussed. A high-speed restoration technique which exploits the benefits of the VP is then proposed and described. The technique simplifies the message transmission processes and reduces the number of generated messages by using preassigned backup virtual paths. Next, the scheme used to design the backup VP routes and spare resource distribution for each link is proposed in order to create a network that applies the proposed restoration scheme. Next, self-reconstruction techniques of backup virtual paths are proposed for the realization of a reversionless restoration cycle. Finally, the feasibility of the distributed control operation is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Optimizing the system of virtual paths

The virtual path (VP) concept is known to be a powerful transport mechanism for ATM networks. This paper deals with the optimization of the virtual paths system from a bandwidth utilization perspective. While previous research on VP management has basically assumed that bandwidth in ATM networks is unlimited, emerging technologies and applications are changing this premise. In many networks, such as wireless, bandwidth is always at a premium. In wired networks, with increasing user access speeds, less than a dozen of broadband connections can saturate even a Gigabit link. We present an efficient algorithm that finds a system of VP routes for a given set of VP terminators and VP capacity demands. This solution is motivated by the need to minimize the load, or reduce congestion, generated by the VP's on individual links. A nontrivial performance guarantee is proven for the quality of the proposed solution and numerical results show that the proposed solution carries the potential for a near optimal allocation of VPs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Dynamic bandwidth control of the virtual path in an asynchronous transfer mode network

The virtual path concept has several valuable features to construct an economical and efficient asynchronous transfer mode (ATM) network. One of them is bandwidth control which affords transmission efficiency improvement through statistical sharing of capacity. An effective bandwidth control algorithm and its calculated performance are described. Network performance with the algorithm is evaluated, and the bandwidth control is shown to successfully improve network transmission efficiency with only a slight increase in processing load compared to the fixed bandwidth scheme. A method is also proposed to equalize call loss probability for each virtual path. The effectiveness of the method is demonstrated by analysis. >