Revenue optimization of telecommunication networks

The optimal routing and dimensioning of circuit-switched networks operating with call revenues is examined, and F.P. Kelly's (1988) model is extended in two directions. First, the formulation is transformed in such a way that the optimality equations are significantly easier to derive, and another interpretation of Kelly's induced costs is given. Alternative routing is introduced, the corresponding values for the induced costs and the net path revenue are given, and it is shown that the optimal routing is given by an equal-revenue rule. It is also shown that the dimensioning aspect is easily decomposed into individual link dimensioning problems if the fixed-point multipliers are known. Some results for networks operating with state protection are presented to show that the method also works quite well for networks with heterogeneous traffic     

Adaptive Optimization-based Routing in Wireless Mesh Networks

Routing is a critical component in wireless mesh networks. The inherent shared-medium nature of the wireless mesh networks, however, poses fundamental challenges to the design of effective routing policies that are optimal with respect to the resource utilization. Node churns and traffic fluctuations exacerbate such a problem. In this paper, we propose a novel adaptive routing algorithm for multiple subscribers in wireless mesh networks. We view a mesh network with multiple nodes as an entity that optimizes some global utility function constrained by the underlying MAC layer interference. By solving the optimization problem, the network is driven to an efficient operating point with a certain routing policies for each node. We then use this operating point information to adaptively find better paths, which is able to gear the network towards optimal routing. Further, we take the fluctuations of the network into consideration and thus render our algorithm more robust for a variety of network situations. Simulations demonstrate the efficiency and efficacy of our algorithm.     

A near-optimal routing and dimensioning algorithm for dynamic WDM rings

In this paper a novel algorithm which jointly solves the problems of routing and dimensioning in dynamic WDM rings is proposed. The algorithm is simple, very fast (processing time <1 s) and applicable to rings of any size. After applying the algorithm to rings of 6–20 nodes, it was found that it outperformed the best proposal to date. In the cases where the optimal solution could be obtained by solving an ILP (Integer Linear Programming) model, the algorithm proposed here obtained exactly the same results. These facts make the proposed method the best solution to date for the routing and dimensioning of dynamic WDM rings, the most popular topology in metropolitan networks.     

Distributed dynamic routing schemes

Schemes that do not explicitly use much information about the state of networks are briefly surveyed, with the focus on dynamic alternative routing (DAR), a simple but highly effective routing method currently planned for the British Telecom Network. State-dependent routing and how some of the methodology also has bearing on the control issue are discussed. The problem of dimensioning a network that uses dynamic routing (i.e. how much capacity is needed and where it should be put to provide an acceptable performance) is addressed. A practical example, which refers to routing in an international access network, is discussed. Some conclusions are drawn on the benefits and drawbacks of distributed routing     

DDD Network Optimization in Field Engineering--From Theory to Application

This paper deals with some important practical applications of teletraffic theory to field engineering problems. It is shown that the following tasks concerning line switching telephone networks can be mastered by means of a few handy tables: loss calculation and dimensioning of trunk groups for full or limited access; very accurate loss approximation of link systems with an arbitrary number of stages, operating as group selection or traffic concentrating arrays with point-to-group selection mode (regarding this, and also optimal link structures, wiring, etc., see [7] in this issue); dimensioning groups with limited or full access for offered peaked overflow traffic; cost minimizing partition of the traffic in local or toll networks with alternate routing to the various trunk groups; and computerized dimensioning is of course also possible.     

Multicommodity flow models, failure propagation, and reliable lossnetwork design

Multicommodity flow (MF) models are well known and have been widely used in the design of packet-switched networks. They have also been used as approximations in the design of circuit-switched networks with reliability constraints. We investigate the usefulness of multicommodity models both as routing models and as an integral part of design models conceived under the failure propagation strategy. First, we compare the performance measures calculated by the models with results produced by a real-time technique. Next, we study the performance of networks dimensioned with flow models and with known adaptive models under failures of transmission facilities when a real-time routing technique is used. Results obtained using realistic data show that the MF models compare favorably with exact dimensioning algorithms when failures are considered     

A general framework for developing adaptive fault-tolerant routingalgorithms

It is shown that Cartesian product (CP) graph-based network methods provide a useful framework for the design of reliable parallel computer systems. Given component networks with prespecified connectivity, more complex networks with known connectivity and terminal reliability can be developed. CP networks provide systematic techniques for developing reliable fault-tolerant routing schemes, even for very complex topological structures. The authors establish the theoretical foundations that relate the connectivity of a CP network, the connectivity of the component networks, and the number of faulty components: present an adaptive generic algorithm that can perform successful point-to-point routing in the presence of faults: synthesize, using the theoretical results, this adaptive fault-tolerant algorithm from algorithms written for the component networks: prove the correctness of the algorithm: and show that the algorithm ensures following an optimal path, in the presence of many faults, with high probability     

Three-level traffic shaper and its application to source clockfrequency recovery for VBR video services in ATM networks

Studies the traffic shaping issues for VBR video services in ATM networks with stress put on the source clock frequency recovery aspect. The authors propose a “three-level traffic shaper” (TLTS) which is able to limit the minimum as well as the maximum cell rate of input VBR traffic. For a VBR video source modeled after a two-state Markov modulated Poisson process, they determine, as performance measures, the cell loss probability, the underflow probability, and the maximum delay that a cell can experience in the proposed TLTS. Then they apply the TLTS for source clock frequency recovery in VBR video services. In extending the existing CBR-based synchronous residual time stamp (SRTS) method for VBR video services, it is necessary to restrict the minimum, as well as the maximum, number of cells generated in a fixed period of time to ensure the transmission of timing information, and the proposed TLTS is tailored to meet this necessity by adopting an optimal dimensioning procedure based on the genetic algorithm (GA). Finally the authors provide some numerical examples to demonstrate the optimal dimensioning procedure of TLTS and the related performances of statistical multiplexing and source clock frequency recovery     

Blocking evaluation for networks with residual capacity adaptiverouting

An algorithm is proposed for obtaining conservative estimates for the end-to-end blocking probability of networks operating with residual capacity adaptive routing. Two important requirements are that it should be fast enough for use within an iterative network design procedure and have an accuracy sufficient for that purpose. The algorithm is based on the assumption that the stationary behavior of residual capacity adaptive routing can be adequately modeled by a nonadaptive routing with suitably chosen parameters. An algorithm is proposed for the stationary version that is stable and fast but overestimates the blocking. A number of modifications of the model to improve its accuracy are examined. It is concluded that the model can be used for network design if a conservative solution is acceptable     

Capacity dimensioning and routing for hybrid satellite and terrestrial systems

Satellite network architecture plays an important role in the success of a satellite business. For future commercial broadband data satellite networks integrated with the terrestrial network, satellite network topology, link capacity, and routing have major impacts on the cost of the network and the amount of revenue the network can generate. To find the most cost-effective satellite network topology, we propose a unified mathematical framework using a two-stage stochastic programming formulation. The solution to the stochastic programming formulation gives optimal link capacities and an optimal routing strategy for different network topologies, taking into account uncertainties in long-term aggregate traffic statistic estimation. Using a simple satellite network example, we show the feasible topology regions for three different satellite topologies and show that, for some parameter values, the hybrid topology is more cost effective than nonhybrid topologies. In the limit of high traffic rejection cost, stochastic dimensioning reduces to static dimensioning. We study worst case static dimensioning for a general geosynchronous earth orbit satellite network and show the feasible topology regions, as well as effective cost comparisons for different topologies. We conclude with a discussion on network cost and architectural flexibility relating to satellite network design.     

Adaptive load-balancing in WDM mesh networks with performance guarantees

In nowadays, wavelength-division multiplexing (WDM) networks, on the one hand, increasingly more users expect the network to provide high-priority QoS services demanding no congestion and low latency. On the other hand, it is significantly more difficult for network operators to forecast future traffic demands, as the packet traffic running over WDM networks fluctuates over time for a variety of reasons. Confronted with a rough understanding of traffic patterns as well as the increasing number of time-sensitive applications, most networks today are grossly over-provisioned. Thus, designing cost-effective WDM networks in an uncertain traffic environment, which includes network planning and robust routing, is both an important and a challenging task. In this paper, we explore adaptive load-balancing to investigate the problems of network planning and robust routing for WDM mesh networks under varying traffic matrices. We first propose an efficient heuristic algorithm called Maximizing Network Capability (MNC) to provision congestion-free and cost-effective WDM networks based on load-balancing to deal with traffic uncertainty. Then, a novel traffic grooming algorithm called Adding Direct Traffic (ADT) is proposed to implement robust routing with partial traffic information. Finally, we demonstrate by simulation that MNC consumes less resources than previous methods and performs quite close to the optimal solution, while ADT achieves the desirable performance in delay, jitter (delay variation), and throughput compared with existing robust routing and traffic grooming algorithms.     

Joint routing and dimensioning of optical burst switching networks

Existing methods for handling routing and dimensioning in dynamic WDM networks solve the two problems separately. The main drawback of this approach is that a global minimum cost solution cannot be guaranteed. Given that wavelengths are costly resources, determining the minimum network cost is of fundamental importance. We propose an approach which jointly solves the routing and dimensioning problems in optical burst switching (OBS) networks, guaranteeing a target blocking per connection. The method finds the set of routes and the number of wavelengths per network link that minimise the total network cost. To accomplish this, an integer linear programming problem is solved. The proposed method was applied to ring networks, where the optimal solution achieves a reduction in the network cost of 10–40% (for traffic loads <0.4, compared to solving both problems separately). In the case of mesh topologies, to reduce the computational complexity of the method, we applied a variation of it which achieves a local minimum. Even so, a reduction of 5–20% (for traffic loads <0.4) in the network cost was obtained. This ability to lower network cost could make the proposed method the best choice to date for dynamic network operators.     

在ATM网络中采用业务流自适应分布优化控制的拥塞概率分析

本文提出了一种降低ＡＴＭ网络拥塞率的业务流量分布自适应优化控制方法,建立了一种碰撞函数型的新的距离测度,并建立了多种业务环境下拥塞概率的分析模型,得出了多端口拥塞的计算公式,研究结果表明,业务流量分布的自适应优化控制技术能很好的改善ＡＴＭ网络内的业务流量分布,大大降低了信道拥塞率。     

Multi-Layer Differentiated Integrated Survivability for Optical Internet

In this paper, we study the problem of multi-layer integrated survivability (MLIS) for efficiently provisioning reliable traffic connections of arbitrary bandwidth granularities in the integrated optical Internet. We decompose the MLIS problem into three sub-problems: survivable strategies design (SSD), spare capacity dimensioning (SCD), and dynamic survivable routing (DSR). First, a review of network survivability in multi-layer IP/WDM networks is provided. Then, multi-layer survivability strategies are proposed and it is observed how these strategies could be applied to the integrated optical Internet architecture. We also present an enhanced integrated shared pool (ISP) method for solving the static MLIS problem (i.e., the SCD sub-problem) and the priority-based integer programming formulations are also given. Moreover, we design a novel scheme called the differentiated integrated survivability algorithm (DISA) to solve the dynamic MLIS problem (i.e., the DSR sub-problem), which employs flexible survivable routing strategies according to the priority of the traffic resilience request. Performance simulation results of DISA show that our adaptive survival schemes perform much better in terms of traffic blocking ratio, spare resource requirement, and average traffic recovery ratio compared with other solutions in the optical Internet.     

Effects of a Priority Discipline in Routing for Packet-Switched Networks

This paper addresses itself to some comparisons of adaptive routing algorithms in store-and-forward Communication nets. The intent here is to demonstrate how some relatively simple add-ons to already existing adaptive algorithms can decrease the average message delay and increase message throughput in the network. The overview of many existing routing algorithms is intended to point out that, although an algorithm may be adaptive, it is not necessarily good in terms of the performance measures addressed in this paper. The basic objective of this study is to assess the effects of endogenous priority assignment to messages that have reached some specified aging threshold while in the network and to note the effects of Such priority assignment on network performance. The performance measures are average message delay, throughput, and number of messages undelivered. The routing techniques are demonstrated via simulation on an 8node highly connected network and a 19-node Advanced Research Projects Agency (ARPA) network. The routing algorithms are applied with and without network element destruction on the selected networks.     

Fair integration of routing and flow control in communicationnetworks

Relationships among delay, throughput, and fairness, three conflicting performance criteria in modern flow-controlled communication networks, are investigated, and an optimal tradeoff among them is defined. Several fair bandwidth sharing schemes are introduced and compared with each other for a variety of network configurations. The results obtained are then utilized to define an optimal operating point (OOP) which maximizes the generalized network power. Given a fixed routing, it is shown that the OOP can be found via any unconstrained optimization algorithm. If rerouting is allowed, it is also shown that the OOP can be found by solving a variant of the multicommodity convex cost network flow problem. An algorithm for this problem is developed and tested for a number of networks. A delay-directive flow control scheme is suggested to realize the OOP in real operating networks, and additional implementation issues are discussed     

A mobility-based framework for adaptive clustering in wireless adhoc networks

This paper presents a novel framework for dynamically organizing mobile nodes in wireless ad hoc networks into clusters in which the probability of path availability can be bounded. The purpose of the (α, t) cluster is to help minimize the far-reaching effects of topological changes while balancing the need to support more optimal routing. A mobility model for ad hoc networks is developed and is used to derive expressions for the probability of path availability as a function of time. It is shown how this model provides the basis for dynamically grouping nodes into clusters using an efficient distributed clustering algorithm. Since the criteria for cluster organization depends directly upon path availability, the structure of the cluster topology is adaptive with respect to node mobility. Consequently, this framework supports an adaptive hybrid routing architecture that can be more responsive and effective when mobility rates are low and more efficient when mobility rates are high     

Dynamically controlled routing in networks with non-DCR-compliantswitches

The authors investigate the deployment of a state-dependent call routing scheme in a network where only a fraction of the switches can fully support it. The state-dependent routing scheme considered is dynamically controlled routing (DCR). Not all switches are assumed to be capable of supporting the feature that DCR requires. For switches that cannot support DCR, several alternative routing schemes are considered. These are: FHR, fixed routing (FR), and adaptive controlled routing (ACR). These schemes were selected on the basis of their modest switch requirements, which can be expected to be satisfied with no or minimal new development by the vast majority of existing switch products. The objective in the article is to define feasible interworking arrangements between DCR and these schemes and assess the performance that can be expected of a network operating under these arrangements. The authors begin by discussing DCR, and describe how it can be enhanced to interwork with non-DCR switches. They describe the routing schemes considered for the non-DCR switches, and how they can interwork with DCR. After that they analyze the performance that a network can expect to achieve when it supports DCR in its DCR switches in conjunction with one of the other routing schemes in its non-DCR switches     

Topological design,routing and capacity dimensioning for ISL networks in broadband LEO satellite systems

This paper considers the network design of intersatellite link (ISL) networks in broadband LEO satellite systems, where the major challenge is the topology dynamics. First, a general method to design convenient ISL topologies for connection‐oriented operation is presented, and a reference topology for numerical studies is derived. A permanent virtual topology is then defined on top of the orbiting physical one, thus forming a framework for discrete‐time dynamic traffic routing. On this basis, heuristic and optimization approaches for the combined routing and dimensioning task, operating on discrete time steps, are presented and their performance is numerically compared. It is shown that minimizing the worst‐case link capacity is an appropriate target function, which can be formulated as linear optimization problem with linear constraints. Using linear programming (LP) techniques, the dimensioning results are clearly better than with simple heuristic approaches. Copyright © 2001 John Wiley & Sons, Ltd.     

Generalization of the ECCS method to the multihour case

The classical ECCS method for dimensioning hierarchical telephone networks is extended to the multihour case. The problem is reformulated as a nonlinear optimization method, and the Kuhn-Tucker equations are derived. It is shown why the ECCS method cannot solve this multihour case. The ECCS method is presented as a solution technique for the Lagrangian relaxation of the multihour problem in which subgradient techniques are used for the solution of the dual. A numerical algorithm implementing these ideas is described that can handle networks with arbitrary hierarchies and allows time-of-day routing changes. Preliminary numerical results of the method are presented, showing that the multihour algorithm can reduce a network's cost when compared to currently used methods