A major challenge in the design of multimedia networks is to meet the quality of service (QoS) requirements of all admitted users. Regulation and scheduling are key factors for fulfilling such requirements. We propose a rate-based regulation-scheduling scheme in which the regulation function is modulated by both the tagged stream's characteristics and the state information fed-back from the scheduler. The rate-jitter and bandwidth share of each tagged connection are controlled appropriately by considering the system time and the queue length of the scheduler. Simulation results have shown that the proposed scheme works better than other rate-based disciplines.

This is the first paper to report the influence of fuzzy thresolding-based buffer management scheme on the end-to-end delay performance of cell switching networks including asynchronous transfer mode (ATM) networks. In this approach, the fraction of the selectively blocked cells, corresponding to the difference of cell loss due to buffer overflow, between the traditional fixed and fuzzy schemes, are re-routed to their final destinations. A 50-switch, representative, cell-switching network under fuzzy thresholding is first modeled, second, simulated on a testbed consisting of a network of 25+ Pentium workstations under Linux, configured as a loosely-coupled parallel processor, and third, its performance is studied under realistic input traffic conditions. A total of 10,000 user calls, generating between 1.0 and 1.5 million ATM cells, is stochastically distributed among the nodes. Performance analysis reveals that for different input traffic distributions ranging from light to moderate to heavy traffic, the re-routing approach successfully routes these blocked cells, although it causes the average end-to-end cell delay in the network to increase, compared to the fixed scheme, by a factor ranging from 1.65 for relatively light traffic to 6.7 for heavy traffic.

In this paper, new integrated schemes of scheduling real-time traffic and cell loss control in high speed ATM networks are proposed for multiple priorities based on variable queue length thresholds for scheduling and the Partial Buffer Sharing policy for cell loss control. In our schemes, the queues for buffering arriving cells can be constructed in two ways: one individual queue for each user connection, or one physical queue for all user connections. The proposed schemes are considered to provide guaranteed QoS for each connection and cell sequence integrity for virtual channel/path characteristics. Moreover, these new schemes are quite flexible and can realize different scheduling algorithms. This paper also provides the Stochastic Petri Net models of these integrated schemes and an approximate analysis technique, which significantly reduces the complexity of the model solution and can be applied to real ATM switch models. From the numerical results, we can see that our schemes outperform those well-known schemes such as the head-of-line (HOL) priority control and the queue length threshold (QLT) policy.

The major concern at a branch point in asynchronous transfer mode (ATM) networks for point-to-multipoint available bit rate (ABR) services is how to consolidate backward resource management (BRM) cells from each branch for a multicast connection. In this paper, we propose an efficient feedback consolidation algorithm based on an adaptive dynamic threshold (ADT) to eliminate consolidation noise and to reduce consolidation delay. The main idea of the ADT algorithm is that each branch point estimates the ABR traffic condition of the network through virtual queue estimation. Simulation results show that the proposed ADT algorithm can achieve a faster response in congestion status and a higher link utilization compared with the previous works.

This paper presents a real-time integrated traffic management (RITM) scheme that can effectively manage variable bit rate (VBR) and available bit rate (ABR) traffics having unpredictable characteristics in asynchronous transfer mode (ATM) networks. An unique feature of this scheme is that it has a special ATM cell control block, which makes it possible to monitor VBR and bursty traffics in real-time so that the delay incurred to measure cell arrival rate is minimized. In addition to its traffic monitor capability, the proposed scheme intends to dynamically reassign the leftover network resources to VBR/ABR connections without any deterioration in quality of service (QoS) of the existing connections. Particularly, we investigate into some functions of traffic management schemes that should be integrated to operate correctly in the emerging ATM networks. Also, we emphasize the merits of the RITM that has been developed to be a simple and efficient traffic management scheme to support the increasing data/Internet services and to get over difficulties in hardware complexities. The capability of managing the incoming ATM traffics in real-time helps determine an optimal acceptable number of user connections for a given network condition. We can use this value as a threshold to prevent the network from being congested and to find out a cost-effective buffer design method. This property makes the scheme extremely attractive as it supports most delay-sensitive and loss-sensitive applications at the same time without changing the existing ATM switching system architecture. The RITM scheme has been verified to reliably monitor incoming traffics and to efficiently manage network resources by computer simulations.

In this study, we propose a simple multipoint-to-point ABR mechanism that can be implemented easily in existing ATM networks. The proposed scheme can provide fair bandwidth allocation among the sources in multipoint-to-point connection.

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.

This letter proposes a congestion control scheme for the ABR service of ATM networks which have non-responding connections. The control scheme is robust with respect to both the round trip delay and the loss of control information caused by non-responding connections. Thus, it is shown that the proposed control scheme guarantees the QoS of the network.

In this paper, we propose optimization approaches for the parameter determination of the PNNI complex node model. Two optimal objectives are discussed: Least Square Approximation and Maximum Deviation Minimization. For each objective, we propose two practical criteria for setting up bypasses: Maximum Difference Removal and Largest Deviation Removal. Generalized inverse of matrix and linear programming techniques are used to find the solutions. The numerical results show that the least square approximation with the largest deviation removal criteria has the best performance as the number of bypasses increases.

In Asynchronous Transfer Mode (ATM) networks, congestion can be caused by unpredictable statistical fluctuations of traffic flows and fault conditions within the network. If congestion happens, then the network performance for the already established connection will decrease. ATM networks use the preventive congestion control mechanisms such as Usage Parameter Control (UPC) and Connection Admission Control (CAC) to avoid congested conditions. Knowing that many sources in ATM networks have variable traffic stream with different QoS characteristics, traffic management functions become necessary to control the traffic flows within the network. By using the signaling procedures at the call setup phase, the network and source reach an agreement for some traffic characteristic parameters. If the source violates the traffic parameters, then the probability of congestion increases. So the network must control the source traffic streams and detect well the violating cells. Therefore, fast detection of any violating source is one of the most important characteristics of a good traffic policer. In this paper we propose a fuzzy traffic policer with high ability in detection of violating sources. Our proposed fuzzy controller has two inputs, estimated passed mean cell rate and the current state of the counter. If the output of fuzzy controller is 1, then the input cell is detected as violating cell, otherwise it is a non-violating cell. Simulation results obtained from two traffic sources, show that the proposed traffic policer has better selectivity than the conventional leaky bucket. It is observed that our proposed traffic policer has better ability for mean cell rate control, peak cell rate control and burst duration control. Furthermore, it is observed that the proposed traffic policer outperforms the conventional leaky bucket specially when the dynamic behavior is considered.

Major problems of traffic control in ATM networks include how to decide whether a network accepts a new call or not in real time and how to select the best set of Dual Leaky Bucket (DLB) parameter values. To solve these problems, it is necessary to determine the amount of network bandwidth required by the call. In this paper, we present an analysis based on bounding technique to derive an upper bound on bandwidth requirement when the call is characterized by a set of DLB parameters. Consequently, a new definition of the upper bound on bandwidth requirement and simple formulae used for computing the upper bound have been obtained. To clarify the advantages of the derived upper bound, we demonstrate its two applications, one to select the best set of DLB parameter values from candidates for minimizing the amount of bandwidth to be allocated to the call and the other to establish a Connection Admission Control (CAC) scheme. The upper bound-based CAC scheme is fast enough to process in real time due to its simplicity and provides a significant improvement of network utilization compared to the peak rate-based CAC scheme.

In ATM Network, the VBR (Variable Bit Rate) service category is used to accommodate TCP/IP traffic. In an international ATM network with large propagation delay, higher TCP throughput can be obtained by use of window scale option. In order to accommodate TCP traffic with window scale option effectively, it is required to select appropriate values of VBR parameters, i. e. SCR (Sustainable Cell Rate) and MBS (Maximum Burst Size), and to evaluate the impact of UPC (Usage Parameter Control) function on TCP throughput. We have studied those technical issues for the conventional TCP, but the results cannot be applied to TCP traffic with the window scale option due to the TCP terminal performance and the large window size. In this paper, we proposed VBR parameter determination method for TCP with the window scale option and evaluated the values in each condition. These results show that the determined MBS is much smaller than the burst length of TCP segments especially using low performance TCP terminals. Furthermore, we also discuss some experimental results of TCP throughput degradation due to UPC function. It shows that the throughput of TCP with large window size is degraded when the SCR and MBS values used in ATM switch are smaller than the determined values.

This paper studies how the self-similarity of traffic changes through shaper (buffered leaky bucket) and switch in ATM networks by numerical experiments. Further the applicability of CAC algorithm to shaped self-similar traffic is also investigated. Numerical experiments show self-similarity of total output traffic from shapers and switch is kept while connection-wise self-similarity is broken.

The Asynchronous Transfer Mode (ATM) technique has been accepted as a basis for the future B-ISDN networks. In ATM networks, all information is packetized and transferred in small packets of fixed length, called cells. The packetized information transfer, without flow control between the user and the network and the use of statistical multiplexing, results in a need of a policing mechanism to control the traffic parameters of each virtual connection in order to guarantee the required quality of service (QoS). Policing of the peak cell rate is generally not complex and can be achieved by using a cell spacer or other policing mechanisms (PMs). Monitoring of the mean cell rate is more difficult, but is intended to improve the link utilization when it has to handle bursty traffic sources. Conventional PMs, such as the Leaky Bucket Mechanism (LBM) and Window Mechanisms (WMs), are not well suited to the bursty nature of the sources supported by ATM networks, therefore intelligent PMs are needed. In this paper, we propose a Fuzzy Policing Mechanism (FPM) for multimedia applications over ATM networks. We consider the case of still picture source control. The performance evaluation via simulation shows that the FPM efficiently controls the mean cell rate of the still picture source. The proposed FPM shows a good response behavior against parameter variations and the selectivity characteristics approach very close to the ideal characteristic required for a PM. The FPM has a better characteristic compared with the LBM.

We analyze the behavior of a finite FIFO buffer in an advanced packet-switched network. It is modeled by a multi-class single-server delay-loss system Σχi MAP i/ PH /1/m. As stochastic process of the system it yields a finite Markov chain with QBD structure and two boundary sets. Our main result is a new representation of its steady-state vector in terms of a linear combination of exactly two matrix-geometric components. Furthermore, we present an efficient algorithm to solve the corresponding matrix-quadratic equations. As second key result we state a new efficient recursive procedure to calculate the congestion characteristics of this delay-loss system.

The classical max-min policy has been suggested by the ATM Forum to support the available bit rate (ABR) service class. However, there are several drawbacks in adopting the max-min rate allocation policy. In particular, the max-min policy is not able to support the minimum cell rate (MCR) requirement and the peak cell rate (PCR) constraint for each ABR connection. Furthermore, the max-min policy does not offer flexible options for network providers wishing to establish a usage-based pricing criterion. In this paper, we present a generic weight-based rate allocation policy, which generalizes the classical max-min policy by supporting the MCR/PCR for each connection. Our rate allocation policy offers a flexible usage-based pricing strategy to network providers. A centralized algorithm is presented to compute network-wide bandwidth allocation to achieve this policy. Furthermore, a simple switch algorithm using ABR flow control protocol is developed with the aim of achieving our rate allocation policy in a distributed networking environment. The effectiveness of our distributed algorithm in a local area environment is substantiated by simulation results based on the benchmark network configurations suggested by the ATM Forum.

In this paper an ATM call level model, where service classes with QoS guarantees (CBR/VBR) as well as elastic (best effort) services (ABR/UBR) coexist, is proposed and a number of simulations have been carried out on three different network topologies. Elastic traffic gives on the network level rise to new challenging problems since for a given elastic connection the bottleneck link determines the available bandwidth and thereby put constraints on bandwidth at other links. Thereby bandwidth allocation at call arrivals but also bandwidth reallocation at call departure becomes, together with routing, an important issue for investigation. Two series of simulations have been carried out where three different routing schemes have been evaluated together with two bandwidth allocation algorithms. The results indicate that the choice of routing algorithm is load dependent and in a large range the shortest path algorithm properly adopted to the mixed CBR/ABR environment performs very well.

The proposed GCRA (Generic Cell Rate Algorithm) traffic shaper consists of a regulator and a scheduler. It can shape multiple incoming VBR (Variable Bit Rate) cell streams simultaneously to be strictly conforming according to the GCRA algorithm when the cells depart for the ATM output link. The impact of cell emission conflicts is considered and resolved by using an EDD (Earliest-Due-Date) scheduler and a feedback signal from the scheduler to the regulator. The call admission control condition and the cell delay bound are derived. Simulation results demonstrate that the output cell streams of the proposed GCRA traffic shaper do not contain any non-conforming cells and the scheduler queue size is significantly reduced. Meanwhile, the delay performance is almost not affected by the use of the feedback mechanism.

In this paper, a design concept that offers ATM-VP connections with different protection levels is presented. The users have the choice to select the protection level they wish, the network transport service they need, and the worst cell loss they can tolerate at call set up time, and pay accordingly. Besides, an advanced adaptive traffic control scheme that simplifies call and cell processing is also presented. Many important functions such as call admission, VC-bandwidth reservation, cell-level congestion control, etc. are efficiently performed at the boundary of the backbone network. In this way is given a suitable answer to the important question: "How can future telecommunication networks based on ATM provide services with customized availability ?" A platform that outlines the potential interaction between restoration methods and congestion avoidance schemes is also obtained.

For traffic control in high speed ATM Networks Usage Parameter Control (UPC) plays an important role. The existing UPC schemes have some limitations. It is difficult to implement policy which involves monitoring vioations while guaranteeing QoS for the compliant connections-particularly with respect to bursty traffic sources. This is due to the difficulty in measuring the Sustained Cell Rate (SCR) and Maximum Burst Size (MBS) parameters simultaneously. To ensure prompt action against policy-violations, speedy detection is an important requirement. But the existing UPC schemes do not have a satisfactory response time. In this paper, we propose a new scheme called Markovian State-Dependent UPC schemes (MSDU) to police SCR and MBS parameter violation simultaneously with a satisfactory response time. The MSDU scheme is performed by using two virtual queues: 1) a Markovian State Dependent Service queue and 2) a Fixed Service queue. The discrete time analysis of the MSDU is carried out for a bursty source which is a Markov-Modulated Bernoulli Process (MMBP). The improved effectiveness of the proposed MSDU is clarified by a numerical comparison with UPC based on standard Leaky Bucket scheme.