Extension of virtual path concept for QOS guarantee

Quality control methods for an asynchronous transfer model (ATM) network to which the virtual path (VP) concept is applied are discussed. The factors which affect the quality of service (QOS) of virtual circuits (VCs) given a layered multiplexing structure are clarified, and the evaluation methods of each VC's QOS using these factors are presented. The necessity for each VP to perform traffic shaping in order to control each VC's QOS based on the above evaluation is discussed. A two-level bandwidth allocation control method which assures each VC's QOS is also presented. Two approaches for realizing a range of QOS requirements of VCs through VPs are investigated and compared from the viewpoint of transmission-path utilization efficiency. >

The virtual path (VP) concept in ATM networks simplifies network structure, traffic control and resource management. For VP formulation, a VP can carry traffic of the same type (the separate scheme) or of different types (the unified scheme). For VP adjustment, a certain amount of bandwidth can be dynamically assigned (reserved) to VPs, where the amount (the bandwidth incremental/decremental size) is a predetermined system parameter. In this paper, we study least loaded path-based dynamic routing schemes with various residual bandwidth definitions under different bandwidth allocation (VP formulation and adjustment) schemes. In particular, we evaluate the call blocking probability and VP set-up processing load with varying (bandwidth) incremental sizes. Also, we investigate numerically how the use of VP trades the blocking probability with the processing load. It is found that the unified scheme could outperform the separate scheme in certain incremental sizes. Moreover, we propose two ways to reduce the processing load without increasing the blocking probability. Using these methods, the separate scheme always outperforms the unified scheme.

Deterministic algorithm for VP assignment in ATM networks

The advantages of applying the virtual path (VP) concept to asynchronous transfer mode (ATM) networks are summarized. The implementation techniques of VPs with ATM cross-connect systems and some VP applications are presented. It is demonstrated that network capability can be effectively increased by applying VP techniques. >

The future Internet will support a large variety of services whose QoS requirements may vary widely. In order to provide scalable quality of service traffic aggregation may be necessary. We examine several approaches to providing scalable QoS services which includes soft QoS with relative performance guarantees, and hard performance guarantees signaled by RSVP over an aggregated cell switched core. In these approaches QoS is based on aggregate traffic. The question then arises as to what level of QoS is perceived by individual flows within the aggregate. This has an important implication on QoS guarantees which the network can make to individual users. To provide answers to the above question we analyse per-flow and aggregate QoS in an ATM virtual path (VP) which is used as an example of a cut-through handling IP flows. Using cell loss as a measure of QoS, our analysis allows us to investigate the impact of the parameters of individual flows on per-flow QoS. We then compare per-flow QoS against the QoS experienced by the aggregate flow in the VP. Based on numerical tests we find that cell loss experienced by individual flows may be very different from cell loss experienced by the aggregate flow. Thus if aggregate cell loss is used as a QoS constraint in dimensioning of VP this may lead to unfair treatment of flows and hence to potential user dissatisfaction.

Implementation strategies of a contract-based MRI examination reservation process for stroke patients

In the paper we describe a framework for resource management and traffic control which is based on the virtual network concept. In this context the virtual networks are used as a toot for customization of networks management functions and for virtual separation of network resources. We identify three main categories of virtual network applications (service, user and management oriented virtual networks). We discuss generic and application oriented problems, which have to be solved to take full advantage of the proposed framework. We also study the relation between the virtual network concept and the virtual path concept in the context of bandwidth management. The study indicates that using virtual paths for bandwidth management involves some inherent contradictions.

A ring architecture that uses the asynchronous transfer mode (ATM) virtual path (VP) concept to reduce the SONET ring cost in terms of bandwidth management is discussed. The add-drop multiplexer (ADM) proposed for VP ring architectures can evolve from existing SONET ADMs by replacing the STS-3 termination cards by the ATM STS-3c line cards. Existing standard self-healing schemes and protocol SONET rings can be applied to proposed ATM/SONET VP rings. A case study based on a BCC (Bellcore client company) ring network and the sensitivity analysis suggests that the proposed ATM VP ring architecture may be a cost-effective option for implementing the distributed ring grooming system at the DS 1 level. The proposed VP self-healing rings are not only used to carry existing DS 1 and DS 3 service, but can also be used to more cost-effectively consolidate switches for public-switched services and for SMDS, frame relay, and FDDI in metropolitan areas.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

In the ATM network, various kinds of traffic will be supported. This includes traffic which requires high quality of service. For example, coded HDTV requires no cell loss because of high compression and no possibility of retransmission. CBR (constant bit rate) services require no delay jitter. Thus, it will be required to support some class of services with no cell loss and no delay jitter. This paper proposes a new transmission method Q-STM, with which no cell loss and no delay jitter can be supported in the ATM network. The Q-STM introduces two new concepts into the ATM networks; frame structure and time slot reservation. A frame structure itself is similar to the framed ATM. However, in the Q-STM, a frame is divided into some subframes and each subframe is a unit of time switching in intermediate switching nodes. This leads to smaller end-to-end delay than that of the framed ATM. Time slots in a frame are reserved for each Q-STM call in a call setup phase and this leads to no delay jitter and no cell loss. Ordinary ATM service class is also supported and this kind of cell uses an empty slot which is not reserved or is not used because of fluctuation of Q-STM call transmission rate.

We consider the problem of reducing the control cost associated with handling connections (or flows) in multimedia networks such as ATM or an Internet supporting RSVP. This cost lies in processing and storage; it is directly related to connection setup latency and to the maximum number of connections that a switching node can handle. We advocate a systematic grouping of connections inside the transit network in order to reduce connection awareness at intermediate switching points. In the ATM case, this means using dynamic virtual path connections as trunks between ATM access nodes. We analyze the requirements and issues posed by such an architecture. As a first step towards a complete solution, we have developed a signaling prototype that shows how virtual path trunks can be setup or released without additional round trip delays.

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

An improved scheme for self-healing in ATM networks

An enhanced multiple-input multiple-output (MIMO) filtered-x least mean square (FXLMS) algorithm using improved virtual secondary path is proposed as the basis for an active noise control (ANC) system for treating vehicle powertrain noise. This new algorithm is developed to overcome the limitation caused by the frequency-dependent property of the standard FXLMS algorithm and to reduce the variation of convergence speed inherent in multiple-channel cases, in order to improve the overall performance of the control system. In this study, the convergence property of the proposed algorithm is analyzed in the frequency domain in order to yield a better understanding of the physical meaning of the virtual secondary path. In practice, because of the arrangement and sensitivities of the actuators (speakers), transducers (microphones), and physical environment, the magnitude response of the main secondary paths can be very different from each other. This difference will cause difficulty in the overall convergence of the algorithm, which will result in minimal attenuation at some of the channels. The proposed channel equalized (CE) virtual secondary path algorithm is designed to tackle this difficulty by equalizing the mean magnitude level of the main secondary paths and by adjusting other secondary paths correspondingly to keep the coupling effects among the control channels unchanged. The performance of the proposed algorithm is validated by analyzing a two-input two-output active powertrain noise control system.

Connection oriented packet networks such as IP/MPLS can better meet QoS guarantees in terms of delay jitter, bandwidth etc. These connection oriented networks are more vulnerable to failures that could be classified into link/path and degraded failures. Virtual path hopping (VPH) concept discussed here eliminates terminations of data communications in data plane due to degraded failures detected by control plane timers. Dynamic virtual path allocation (DVPA) algorithm proposed here can achieve very fast recovery for premium traffic (PT) from link/path failures while keeping efficiency of network high. This recovery time consists of two main parts; time taken to detect failures and time taken to activate backup path. DVPA algorithm virtually makes time taken to activate backup path `zero' for PT as it uses active backup path. DVPA algorithm maintains a VP-pool between ingress and egress and two or more VPs will be active at any given time, depending on traffic. Also DVPA algorithm makes sure that active backup path is always occupied by best effort traffic (BET) when there are no failures, increasing efficiency of network. According to simulation results, implementing DVPA algorithm in conjunction with VPH concept can achieve a very high availability for PT in future IP/MPLS

In this paper, we focus on improving EDGE technology with the aim that the benefits of mobile communication reach rural environments and isolated areas. We present a method of channel allocation that provides both voice and data services, improving data traffic transmission without putting aside the QoS of voice traffic. Firstly, a general analytical model is presented. Secondly, allocating sequentially the time slots, we study the best way of using few reserved time slots just for voice calls, in order to get greater probabilities of higher throughput. Finally, the results obtained are analysed and using them, the network operator can schedule the channel allocation of th