Efficient Buffer Allocation Scheme for Bursty Traffic in ATM Networks using Fast Reservation Protocol

One of the major problems in the realization of ATM is traffic management, in particular, the resource allocation for an efficient network. Many approaches to the bandwidth management problems [2] and buffer management problems have been proposed. Boyer [IO] suggested a Fast Bandwidth Reservation protocol, while Turner [2] applied the same technique to the buffer allocation for the bursty traffic. In this thesis, we extend Turner\u27s scheme in order to make it more efficient with respect to buffer allocation. We define a new parameter Reduction Factor\u27\u27, which has the potential of saving a significant amount of buffer space in a commonly shared pool of buffers. It is observed that the amount of savings depends upon the cell loss probability (CLP) bound on the network, Source Activity Probability (SAP) and number of connections supported by the network (N) at particular instant. The performance of the scheme is evaluated under various QoS requirements. It is seen that this scheme leads to approximately 38% of savings in the buffer space under certain circumstances. For supporting multimedia services, we also employ the scheme of partitioning the total buffer space. The results show that it leads to 10 % less savings as compared to single buffer scheme under certain conditions. As usage policing is very critical in this scheme, we outline a suitable mechanism and hardware implementation for Usage Parameter Control. The algorithm for acceptance of virtual circuit in the network is also described

Fast packet switching algorithms for dynamic resource control over ATM networks

Real-time continuous media traffic, such as digital video and audio, is expected to comprise a large percentage of the network load on future high speed packet switch networks such as ATM. A major feature which distinguishes high speed networks from traditional slower speed networks is the large amount of data the network must process very quickly. For efficient network usage, traffic control mechanisms are essential. Currently, most mechanisms for traffic control (such as flow control) have centered on the support of Available Bit Rate (ABR), i.e., non real-time, traffic. With regard to ATM, for ABR traffic, two major types of schemes which have been proposed are rate- control and credit-control schemes. Neither of these schemes are directly applicable to Real-time Variable Bit Rate (VBR) traffic such as continuous media traffic. Traffic control for continuous media traffic is an inherently difficult problem due to the time- sensitive nature of the traffic and its unpredictable burstiness. In this study, we present a scheme which controls traffic by dynamically allocating/de- allocating resources among competing VCs based upon their real-time requirements. This scheme incorporates a form of rate- control, real-time burst-level scheduling and link-link flow control. We show analytically potential performance improvements of our rate- control scheme and present a scheme for buffer dimensioning. We also present simulation results of our schemes and discuss the tradeoffs inherent in maintaining high network utilization and statistically guaranteeing many users` Quality of Service

Traffic Management and Congestion Control in the ATM Network Model.

Asynchronous Transfer Mode (ATM) networking technology has been chosen by the International Telegraph and Telephony Consultative Committee (CCITT) for use on future local as well as wide area networks to handle traffic types of a wide range. It is a cell based network architecture that resembles circuit switched networks, providing Quality of Service (QoS) guarantees not normally found on data networks. Although the specifications for the architecture have been continuously evolving, traffic congestion management techniques for ATM networks have not been very well defined yet. This thesis studies the traffic management problem in detail, provides some theoretical understanding and presents a collection of techniques to handle the problem under various operating conditions. A detailed simulation of various ATM traffic types is carried out and the collected data is analyzed to gain an insight into congestion formation patterns. Problems that may arise during migration planning from legacy LANs to ATM technology are also considered. We present an algorithm to identify certain portions of the network that should be upgraded to ATM first. The concept of adaptive burn-in is introduced to help ease the computational costs involved in virtual circuit setup and tear down operations

Explicit congestion control algorithms for available bit rate services in asynchronous transfer mode networks

Congestion control of available bit rate (ABR) services in asynchronous transfer mode (ATM) networks has been the recent focus of the ATM Forum. The focus of this dissertation is to study the impact of queueing disciplines on ABR service congestion control, and to develop an explicit rate control algorithm. Two queueing disciplines, namely, First-In-First-Out (FIFO) and per-VC (virtual connection) queueing, are examined. Performance in terms of fairness, throughput, cell loss rate, buffer size and network utilization are benchmarked via extensive simulations. Implementation complexity analysis and trade-offs associated with each queueing implementation are addressed. Contrary to the common belief, our investigation demonstrates that per-VC queueing, which is costlier and more complex, does not necessarily provide any significant improvement over simple FIFO queueing. A new ATM switch algorithm is proposed to complement the ABR congestion control standard. The algorithm is designed to work with the rate-based congestion control framework recently recommended by the ATM Forum for ABR services. The algorithm\u27s primary merits are fast convergence, high throughput, high link utilization, and small buffer requirements. Mathematical analysis is done to show that the algorithm converges to the max-min fair allocation rates in finite time, and the convergence time is proportional to the distinct number of fair allocations and the round-trip delays in the network. At the steady state, the algorithm operates without causing any oscillations in rates. The algorithm does not require any parameter tuning, and proves to be very robust in a large ATM network. The impact of ATM switching and ATM layer congestion control on the performance of TCP/IP traffic is studied and the results are presented. The study shows that ATM layer congestion control improves the performance of TCP/IP traffic over ATM, and implementing the proposed switch algorithm drastically reduces the required switch buffer requirements. In order to validate claims, many benchmark ATM networks are simulated, and the performance of the switch is evaluated in terms of fairness, link utilization, response time, and buffer size requirements. In terms of performance and complexity, the algorithm proposed here offers many advantages over other proposed algorithms in the literature

Análisis y evaluación de los sistemas de protección contra la congestión en la red digital de sevicios integrados de banda ancha

Postprint (published version

Dynamic bandwidth allocation in ATM networks

Includes bibliographical references.This thesis investigates bandwidth allocation methodologies to transport new emerging bursty traffic types in ATM networks. However, existing ATM traffic management solutions are not readily able to handle the inevitable problem of congestion as result of the bursty traffic from the new emerging services. This research basically addresses bandwidth allocation issues for bursty traffic by proposing and exploring the concept of dynamic bandwidth allocation and comparing it to the traditional static bandwidth allocation schemes

Rendimiento de TCP y Cálculo de Rutas en Redes de Conmutación Óptica de Ráfagas

La tecnología de conmutación óptica de ráfagas (Optical Burst Switching, OBS) es una alternativa prometedora para la próxima generación de redes ópticas. Esta tesis estudia el comportamiento de flujos de datos que empleen el protocolo de transporte TCP (Transmission Control Protocol) sobre una red basada en la mencionada tecnología OBS. Así, la tesis estudia el impacto del asentimiento retardado en OBS, propone un modelo teórico que captura el funcionamiento de TCP sobre OBS con múltiples flujos y estudia el efecto de la sincronización de flujos TCP en una red OBS. Además, la tesis propone una técnica de encaminamiento adaptativa y multicamino para OBS, y diseña e implementa un elemento de cálculo de rutas basado en PCE (Path Computation Element) para redes de conmutación de ráfagas OBS con encaminamiento por longitud de onda, conocidas como WR-OBS (Wavelength-Routed OBS).Departamento de Teoría de la Señal y Comunicaciones e Ingeniería Telemátic