As the speed and the dynamic range of computer networks evolve, the issue of efficient traffic management becomes increasingly important. This work describes an approach to traffic management using explicit rate information provided to the source by the network. We present an asynchronous distributed algorithm for optimal rate calculation across the network, where optimality is understood in the maxmin sense. The algorithm quickly converges to the optimal rates and is shown to be well-behaved in transience.

Congestion Control with Explicit Rate Indication

Modern networks provide a QoS (quality of service) model to go beyond best-effort services, but current QoS models are oriented towards low-level network parameters (e.g., bandwidth, latency, jitter). Application developers, on the other hand, are interested in quality models that are meaningful to the end-user and, therefore, struggle to bridge the gap between network and application QoS models. Examples of application quality models are response time, predictability or a budget (for transmission costs). Applications that can deal with changes in the network environment are called network-aware. A network-aware application attempts to adjust its resource demands in response to network performance variations. This paper presents a framework-based approach to the construction of network-aware programs. At the core of the framework is a feedback loop that controls the adjustment of the application to network properties. The framework provides the skeleton to address two fundamental challenges for the construction of network-aware applications: how to find out about dynamic changes in network service quality; and how to map application-centric quality measures (e.g., predictability) to network-centric quality measures (e.g., QoS models that focus on bandwidth or latency). Our preliminary experience with a prototype network-aware image retrieval system demonstrates the feasibility of our approach. The prototype illustrates that there is more to network-awareness than just taking network resources and protocols into account and raises questions that need to be addressed (from a software engineering point of view) to make a general approach to network-aware applications useful.

A framework based approach to the development of network aware applications

This paper gives an overview of the methods and models used for the performance evaluation of asynchronous transfer mode (ATM)-based broad-band integrated services digital networks (B-ISDNs). Because these methods rely heavily upon stochastic processes theory, the relevant concepts from this field are succinctly recalled. The first main topic is traffic modeling. Because of the large impact upon the performance of B-ISDN systems, the concept of traffic burstiness is discussed and various definitions are given and compared. The most common stochastic traffic models are then discussed: on-off, Markov modulated sources, and Markovian process. The field of self-similar traffic is also reviewed. Another approach to source characterization is reviewed as well: bounded traffic models, which instead of a precise statistical description give a set of bounds on the cell generation process. The second main topic is the use of advanced queueing models for the performance evaluation of the ATM statistical multiplexer, the basic B-ISDN modeling concept underlying the design of switching elements, output buffers, rate adapters, etc. The three main solution methods for the statistical multiplexer are reviewed: matrix methods, generating function approach, and fluid flow approximation. This paper concludes with an overview of current topics in B-ISDN teletraffic research: connection admission control, buffer dimensioning, multiquality of service, cell discard schemes, rate-based flow control, per-virtual-connection queueing, and weighted fair queueing.

Teletraffic engineering in a broad-band era

Connection-dependent threshold model: a generalization of the Erlang multiple rate loss model

The invention concerns an efficient strategy for sharing link bandwidth in a mixed rigid-elastic traffic environment, as well as a strategy for sharing bandwidth among elastic traffic flows. The idea according to the invention is to sharing the link bandwidth among rigid and elastic traffic by dividing the link bandwidth into a first common part CCOM for elastic as well as rigid traffic and a second part CELA dedicated for elastic traffic. Subsequently, one or more admission control parameters for the elastic traffic are determined in order to restrict the number of elastic traffic flows simultaneously present on the link. In particular, by formulating a call-level model for elastic traffic and determining a maximum number NELA of admissible elastic traffic flows based on call-level constraints for the elastic traffic related to throughput and/or blocking, the so-called throughput-to-blocking trade-off for elastic traffic can be fully considered.

Link capacity sharing for throughput-blocking optimality

The authors describe the purpose of the available bit rate (ABR) service in the context of other ATM services and review the agreements on the traffic control mechanism. They describe the recent progress towards standardization of the new service. The general nature of the ABR service is described in comparison with constant bit rate (CBR) and variable bit rate (VBR) services.

The available bit rate service for data in ATM networks

This article describes a framework for monitoring and controlling ATM networks based on the use of management cells. By management cells we refer to a broad class of special cells that circulate around the network to perform a variety of useful functions for monitoring and optimizing the operation of the network. The proposed framework includes current ATM-layer OAM (operations and maintenance) methods as well as new mechanisms for more sophisticated long-term network management. This article explores various existing and new uses of management cells for performance monitoring, traffic control, fault management, and network administration.

/pdf/monitoring-and-control-of-atm-networks-using-special-cells-2focc0oc8m.pdf

Monitoring and control of ATM networks using special cells

The authors study a method for the analysis of fluid buffer models with Markov input rate and constant output rate. In telecommunications applications, the constant output rate typically represents a fixed-rate transmission channel. Given the initial system state, the conditional (time-dependent) survivor function and moments of the buffer content are characterized as the solution of an integral equation. The method depends on the solution of a first passage time problem for the cumulative input process (an integrated Markov process) which is described by a Fredholm integral equation of the second kind. Under appropriate conditions, the integral equation has a Neumann series solution that can be found by successive approximations. Numerical results are presented for a specific example of a buffer shared by a number of input sources varying as independent Ornstein–Uhlenbeck diffusion processes, which may be used, for instance, as a model for statistically multiplexed variable bit-rate video.

Time-dependent behavior of fluid buffer models with Markov input and constant output rates

http://ieeexplore.ieee.org/iel1/35/10618/00492973.pdf

vailable Bit Rate Servi ata in ATM Netwo

This article describes a framework for monitoring and controlling ATM networks based on the use of management cells. By management cells we refer to a broad class of special cells that circulate around the network to perform a variety of useful functions for monitoring and optimizing the operation of the network. The proposed framework includes current 'ATM-layer OAM (operations and maintenance) methods as well as new mechanisms for more sophisticated long-term network management. This article explores various existing and new uses of management cells for performance monitoring, traffic control, fault management, and network administration.

Vijay K. Samalam

Papers

The available bit rate service for data in ATM networks

Monitoring and control of ATM networks using special cells

Time-dependent behavior of fluid buffer models with Markov input and constant output rates

vailable Bit Rate Servi ata in ATM Netwo

Moniforing and Control of