M-architecture: a structural model of traffic managementand control in broadband ISDNs

A model of multiservice network architecture (M-architecture) is presented. An attempt is made to describe the traffic management and control schemes in a systematic way. The basic concepts are developed, and examples are given that indicate how the proposed framework can be used to solve multiplexing, routing, and flow control problems in the ISDN. The emphasis is on the traffic control schemes. The M-architecture can be regarded as either a reference architecture for future multiservice networks or an abstract model of traffic management and control in currently used networks     

Voice QoS in third-generation mobile systems

We analyze voice quality and system performance in third-generation mobile communication systems. We argue that in these networks that are expected to integrate voice, data, and multimedia services, the transport network can no longer be considered as a lossless transparent traffic channel. Rather, proper dimensioning is needed even for plain voice services. Furthermore, the efficient utilization of the network resources shared by voice and data traffic requires sophisticated traffic management in the statistical multiplexing environment. The contribution of the paper is twofold: first, voice quality in the cellular transport network is analyzed and network dimensioning criteria are derived. Second, building on advances reported in the literature and taking into consideration current standardization activities, a joint performance model is established for the air interface (AI) and the transmission network (TN) allowing for the analysis of end-to-end service performance within a uniform framework. To demonstrate the applicability of this model, we point to some performance problems in the multiservice environment and suggest and evaluate traffic management actions to overcome these     

Multi-hour, multi-traffic class network design for virtualpath-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     

Cross-Layer Design for QoS in Wireless Mesh Networks

Cross-layer design for quality of service (QoS) in wireless mesh networks (WMNs) has attracted much research interest recently. Such networks are expected to support various types of applications with different and multiple QoS and grade-of-service (GoS) requirements. In order to achieve this, several key technologies spanning all layers, from physical up to network layer, have to be exploited and novel algorithms for harmonic and efficient layer interaction must be designed. Unfortunately most of the existing works on cross-layer design focus on the interaction of up to two layers while the GoS concept in WMNs has been overlooked. In this paper, we propose a unified framework that exploits the physical channel properties and multi-user diversity gain of WMNs and by performing intelligent route selection and connection admission control provides both QoS and GoS to a variety of underlying applications. Extensive simulation results show that our proposed framework can successfully satisfy multiple QoS requirements while it achieves higher network throughput and lower outage as compared to other scheduling, routing and admission control schemes.     

Adaptive alternate routing in WDM networks and its performance tradeoffs in the presence of wavelength converters

Routing in wavelength-routed all-optical WDM networks has received much attention in the past decade, for which fixed and dynamic routing methods have been proposed. Taking into account the observation that wavelength-routed all-optical WDM networks are similar to circuit-switched voice networks, except with regard to wavelength conversion, we propose an adaptive alternate routing (AAR) scheme for wavelength-routed all-optical WDM networks. A major benefit of AAR is that it can operate and adapt without requiring an exchange of network status, i.e., it is an information-less adaptive routing scheme. The scope of this work is to understand this scheme in its own right since no other dynamic routing schemes are known to have the information-less property. In this paper, we conduct a systematic study of AAR with regard to factors such as the number of converters, load conditions, traffic patterns, network topologies, and the number of alternate paths considered. We observe that the routing scheme with multiple alternate routes provides more gain at a lower load instead of requiring any nodes to be equipped with wavelength converters. On the other hand, the availability of wavelength converters at some nodes, along with adaptive routing, is beneficial at a moderate to high load without requiring all nodes to be equipped with wavelength converters. We also observed that a small number of alternate routes considered in a network without wavelength converters gives a much better performance than a network with full wavelength converters and fewer alternate routes. Throughout this study, we observed that the proposed adaptive alternate routing scheme adapts well to the network traffic condition.     

On call admission control in DS/CDMA cellular networks

Analytical models are proposed for various direct sequence code-division multiple-access (DS/CDMA) call admission control schemes. Many mathematical call admission models for DS/CDMA cellular networks have been proposed. However, they have shortcomings. First, by ignoring the stochastic traffic load variation or call blocking effect, they failed to sufficiently characterize the second moment of other-cell interference. This leads to inaccurate analysis of a real network. Second, the optimal control parameters were often obtained through an exhaustive search which was very time consuming. Finally, the estimation of system capacity in previous models was obtained by using a simple one-slope path-loss propagation model. However, it is well known that a two-slope path loss propagation model is needed in a line-of-sight (LOS) microcell propagation environment. We propose an analytical model for call admission to overcome these drawbacks. In addition, we combine a modified linear programming technique with the built analytical model to find better call admission control schemes for a DS/CDMA cellular network     

A scalable QoS routing model for diffserv over MPLS networks

In this paper, we present a new Quality of Service (QoS) routing model for Differentiated Services (Diffserv) over Multiprotocol Label Switching (MPLS) networks. We use a pre-established multi-path model in which several MPLS label switching paths (LSPs) are established between each ingress-egress router pair in advance. Ingress routers perform per-request admission control and bulk-type resource reservation based on the resource availability on the associated LSPs. We use a utilization-based dynamic load balancing scheme to increase resource utilization across LSPs. The proposed model increases signaling and state scalability in the network core. It also provides hard QoS guarantees and minimizes admission control time. The experimental results verify the achievements of our model under various network topologies and traffic conditions.     

Equivalent capacity and its application to bandwidth allocation inhigh-speed networks

The authors propose a computationally simple approximate expression for the equivalent capacity or bandwidth requirement of both individual and multiplexed connections, based on their statistical characteristics and the desired grade-of-service (GOS). The purpose of such an expression is to provide a unified metric to represent the effective bandwidth used by connections and the corresponding effective load of network links. These link metrics can then be used for efficient bandwidth management, routing, and call control procedures aimed at optimizing network usage. While the methodology proposed can provide an exact approach to the computation of the equivalent capacity, the associated complexity makes it infeasible for real-time network traffic control applications. Hence, an approximation is required. The validity of the approximation developed is verified by comparison to both exact computations and simulation results     

Reinforcement learning based routing in wireless mesh networks

This paper addresses the problem of efficient routing in backbone wireless mesh networks (WMNs) where each mesh router is equipped with multiple radio interfaces and a subset of nodes serve as gateways to the Internet. Most routing schemes have been designed to reduce routing costs by optimizing one metric, e.g., hop count and interference ratio. However, when considering these metrics together, the complexity of the routing problem increases drastically. Thus, an efficient and adaptive routing scheme that takes into account several metrics simultaneously and considers traffic congestion around the gateways is needed. In this paper, we propose an adaptive scheme for routing traffic in WMNs, called Reinforcement Learning-based Distributed Routing (RLBDR), that (1) considers the critical areas around the gateways where mesh routers are much more likely to become congested and (2) adaptively learns an optimal routing policy taking into account multiple metrics, such as loss ratio, interference ratio, load at the gateways and end-to end delay. Simulation results show that RLBDR can significantly improve the overall network performance compared to schemes using either Metric of Interference and Channel switching, Best Path to Best Gateway, Expected Transmission count, nearest gateway (i.e., shortest path to gateway) or load at gateways as a metric for path selection.     

Cross-Layer optimal connection admission control for variable bit rate multimedia traffic in packet wireless CDMA networks

Next generation wireless code division multiple access (CDMA) networks are required to support packet multimedia traffic. This paper addresses the connection admission control problem for multiservice packet traffic modeled as Markov modulated Poisson process (MMPP) with the quality of service (QoS) requirements on both physical layer signal-to-interference ratio (SIR) and network layer blocking probability. Optimal linear-programming-based algorithms are presented that take into account of SIR outage probability constraints. By exploiting the MMPP traffic models and introducing a small SIR outage probability, the proposed algorithms can dramatically improve the network utilization. In addition, we propose two reduced complexity algorithms that require less computation and can have satisfactory approximation to the optimal solutions. Numerical examples illustrating the performance of the proposed schemes are presented.     

Statistical multiplexing and mix-dependent alternative routing inmultiservice VP networks

We consider problems in traffic integration and routing for virtual path (VP)-based multiservice networks. The objective is to exploit statistical multiplexing among various traffic types in order to improve system utilization. Difficulties arise due to statistical multiplexing since a connection's bandwidth requirement depends on the characteristics of the interfering traffic. We first consider whether segregating heterogeneous traffic with different quality of service (QoS) requirements on separate VPs is desirable. Next we consider routing heterogeneous permanent connections given a predefined traffic type mix onto multiple VPs between a source destination pair. We show that it is not necessarily advantageous to have each VP carry every traffic type. In fact, perhaps surprisingly, an optimum solution to this problem suggests that only a small number of traffic types, or even homogeneous traffic, need be present on each VP. Based on this observation, we propose a simple alternative routing algorithm with routing sequences depending on the traffic mix     

Advanced traffic control methods for network management

The objectives of network management control are outlined, and two categories of control are defined: network traffic controls and network configuration controls. Network traffic controls are further classified into traffic volume controls and routing controls, and advanced techniques for achieving each of them are examined. Two classes of methods for specifying the amount of traffic to be controlled are described. In proportional control, a certain proportion of the traffic offered by each exchange is admitted; in threshold control, there is a maximum rate at which the traffic offered by each exchange is admitted. The TCS-V2 traffic-control system, an advanced automatic code-blocking system that uses area and subscriber congestion control, is considered, and the simulated performance of proportional control and threshold control is compared for this system. For routing control, an advanced state-dependent dynamic routing scheme is examined, and the results of a comparative evaluation of dynamic routing schemes are presented     

MPLS网络中保证服务质量的多径路由选择策略

本文提出了一种在多协议标签交换(MPLS, Multiple Protocol Label Switching) 网络中保证服务质量 (QoS,Quality-of-Service) 的多径路由选择策略,其核心思想是引入多路径分散业务量机制,在保证用户服务质量要求的同时达到增加网络呼叫接受率和平衡网络负载的目的.文中着重讨论了用户端对端服务质量要求的多路分解和分配问题,在此基础上提出了多径路由的分支路径选择策略,并研究了策略中的关键参数K对该策略性能的影响.数值结果显示出多路径分散业务量在网络负载均衡方面的重要意义,并且表明用户的要求相对网络资源越高使用多径传输的优势越明显.     

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.     

Domain load balancing routing for multi-gateway wireless mesh networks

As Wireless Mesh Networks (WMNs) are typically used for Internet access, most traffic is routed through the gateways which connect WMN to the wired network. As a result, the gateways tend to get congested and balancing of the traffic load of gateways is critical. In this paper, we consider applications that require continuous provision of a certain bandwidth to a server located at the wired network. If a path that satisfies the bandwidth request cannot be found, the request will be rejected, so that load imbalance will result underutilization of the network capacity. We present a novel load balancing routing algorithm for maximizing the network utilization (i.e., accommodating service requests as many as possible) for multi-gateway WMNs. In the proposed scheme, a WMN is divided into domains. Each domain is served by one gateway, so that all traffic of a domain is served by the corresponding gateway. Our scheme determines routing to balance the traffic load among domains, and then performs load balancing routing within each domain. Simulation results show that in square grid topologies, our intra-domain routing achieves near optimal performance with about 70% less overhead than the existing schemes. Our inter-domain load balancing scheme outperforms the existing heuristics by up to 25% while achieving about 80% performance of the optimal solution.     

Dimensioning optical networks under traffic growth models

In this paper, we consider the problem of dimensioning a large optical wavelength-division multiplexing (WDM) network assuming the traffic is growing over time. Traffic between pairs of nodes is carried through lightpaths which are high-bandwidth end-to-end circuits, occupying a wavelength on each link of the path between two nodes. We are interested in dimensioning the WDM links so that the first lightpath request rejection will occur, with high probability, after a specified period of time T. Here we introduce the concept of capacity exhaustion probability - the probability that at least one lightpath request will be rejected in the time period (0,T) due to lack of bandwidth/capacity on some link. We propose a network dimensioning method based on a traffic growth model which eventually results in a nonlinear optimization problem with cost minimization as the objective and route capacity exhaustion probabilities as the constraints. Computation of exact capacity exhaustion probabilities requires large computing resources and is thus feasible only for small networks. We consider a reduced load approximation for estimating capacity exhaustion probabilities of a wavelength routed network with arbitrary topology and traffic patterns. We show that the estimates are quite accurate and converge to the correct values under a limiting regime in the desired range of low-capacity exhaustion probabilities.     

A fast packet switch for the integrated services backbone network

With the projected growth in demand for bandwidth and telecommunication services will come the requirement for a multiservice backbone network of far greater efficiency, capacity, and flexibility than ISDN (integrated-services digital network) is able to satisfy. This class of network has been termed the broadband ISDN, and the design of the switching nodes of such a network is the subject of much research. The author investigates one possible solution. The design and performance, for multiservice traffic, is presented for a fast packet switch based on a nonbuffered, multistage interconnection network. It is shown that for an implementation in current CMOS technology, operating at 50 MHz, switches with a total traffic capacity of up to 150 Gb/s can be constructed. Furthermore, if the reserved service traffic load is limited on each input port to a maximum of 80% of switch port saturation, then a maximum delay across the switch of on the order of 100 μs can be guaranteed, for 99% of the reserved service traffic, regardless of the unreserved service traffic load     

Virtual path control for ATM networks with call level quality ofservice guarantees

The configuration of virtual path (VP) connection services is expected to play an important role in the operation of large-scale asynchronous transfer mode (ATM) networks. A major research challenge is to understand the fundamental tradeoff between the network call throughput and the processing load on the signaling system and to provide an algorithm for VP capacity allocation that achieves an optimal network operating point while guaranteeing quality of service (QoS) at the call level and satisfies a priori bounds on the processing load of the call processors. We present a taxonomy of previous approaches to the problem and identify their strengths and weaknesses. Based on these observations, we provide an algorithm for the VP capacity allocation problem that satisfies nodal constraints on the call processing load and blocking constraints for each source-destination (SD) pair. The algorithm maximizes the network revenue under the above set of constraints and is parameterized by the number of traffic classes in the network, the method of presentation of networking resources, the admission control policy used in every link and VP, and the network routing scheme. Finally, we apply the algorithm to three sample networks and study several of its performance characteristics. In one case, we applied the calculated VP distribution to the Xunet ATM testbed and verified experimentally the predicted performance     

Adaptive cross‐layer bandwidth allocation in a rain‐faded satellite environment

Two control schemes, based on cross‐layer adaptation and a hierarchical parametric optimization of the bandwidth allocation, are described and investigated in a satellite network environment, in the presence of both real‐time and best‐effort traffic flows. A number of earth stations (traffic stations) operate in different weather conditions, with different levels of fade, which affect the transmitted signals. The call admission control policy for real‐time connections is administered locally at the traffic stations. A master station is charged to manage the time division multiple access bandwidth allocation policy, by defining bandwidth partitions to the traffic stations. Upon detecting significant fade changes, the signalling from the traffic stations triggers new bandwidth redistributions. The control schemes are compared, and the effect of fade countermeasures, applied at the physical layer, on the bandwidth occupation is explicitly accounted for. For each policy, figures of merit such as loss, blocking and dropping probabilities are computed for a specific real environment, based on the Italsat satellite national coverage payload characteristics. Copyright © 2005 John Wiley & Sons, Ltd.