Classical routing and admission control strategies achieve provably good performance by relying on an assumption that the virtual circuits arrival pattern can be described by some a priori known probabilistic model. Recently a new online routing framework, based on the notion of competitive analysis, was proposed. This framework is geared towards design of strategies that have provably good performance even in the case where there are no statistical assumptions on the arrival pattern and parameters of the virtual circuits. The online strategies motivated by this framework are quite different from the min-hop and reservation-based strategies. This paper surveys the online routing framework, the proposed routing and admission control strategies, and discusses some of the implementation issues. Research supported by NSF CCR-9304971, ARO DAAH04-95-1-0121, and by Terman Fellowship. E-Mail: plotkin@cs.stanford.edu, URL: http://theory.stanford.edu/people/plotkin/plotkin.html. 1 Introducti...

Emerging high speed networks will carry traffic for services such as video-on-demand and video teleconferencing -- that require resource reservation along the path on which the traffic is sent. High bandwidth-delay product of these networks prevents circuit rerouting, i.e. once a circuit is routed on a certain path, the bandwidth taken by this circuit remains unavailable for the duration (holding time) of this circuit. As a result, such networks will need effective routing and admission control strategies. Recently developed online routing and admission control strategies have logarithmic competitive ratios with respect to the admission ratio (the fraction of admitted circuits). Such guarantees on performance are rather weak in the most interesting case where the rejection ratio of the optimum algorithm is very small or even 0. Unfortunately, these guarantees can not be improved in the context of the considered models, making it impossible to use these models to identify algorithms th...

High-speed packet networks will begin to support services that need Quality-of-Service (QoS) guarantees. Guaranteeing QoS typically translates to reserving resources for the duration of a call. We propose a statedependent routing scheme that builds on any base stateindependent routing scheme, by routing flows which are blocked on their primary paths (as selected by the state-independent scheme) onto alternate paths in a manner that is guaranteed---under certain Poisson assumptions---to improve on the performance of the base state-independent scheme. Our scheme only requires each node to have state information of those links that are incident on it. Such a scheme is of value when either the base state-independent scheme is already in place and a complete overhaul of the routing algorithm is undesirable, or when the state (reserved flows) of a link changes fast enough that the timely update of state information is infeasible to all possible call-originators. The performance improvements ...

In this paper we consider a family of product-form loss models, including loss networks (or circuit-switched communication networks) and a class of resource-sharing models. There can be multiple classes of requests for multiple resources. Requests arrive according to independent Poisson processes. The requests can be for multiple units in each resource (the multi-rate case, e.g., several circuits on a trunk). There can be upper-limit and guaranteed-minimum sharing policies as well as the standard complete-sharing policy. If all the requirements of a request cannot be met upon arrival, then the request is blocked and lost. We develop an algorithm for computing the (exact) steady-state blocking probability of each class and other steady state descriptions in these loss models. The algorithm is based on numerically inverting generating functions of the normalization constants. In a previous paper we introduced this approach to product-form models and developed a full algorithm for a class of closed queueing networks. The inversion algorithm promises to be even more useful for loss models than for closed queueing networks because fewer alternative algorithms are available for loss models. Indeed, for many loss models with sharing policies other than traditional complete sharing, our algorithm is the first

Field of the Invention The invention relates to efficiently providing multiple grades of service, including protection against overloads, for multiple customers sharing limited resources, wherein "efficiently providing " includes (i) determining when a prospective new customer can be admitted with a desired grade of service, (ii) determining how to adjust capacity in face of changing customer demand and (iii) determining how to respond to resource failure. Background of the Invention 1. Resource-Sharing Problems The setting involves one or more resources, each containing multiple resource units which provide service to multiple customers. Each customer is a source of a stream of requests. Each customer request requires a number of units from each resource, which may be zero, one or greater than one, and may be different for different customers, but which is the same for different requests of the same customer. If all requirements can be met upon arrival of a new request, then the new request is admitted, and all required resource units are held throughout the request holding time. Otherwise, the request is not admitted, and is said to be blocked.

In this paper we describe Quorum, a non-invasive approach to scalable quality-of-service provisioning that uses traffic shaping, admission control, and response monitoring at the border of an Internet site to ensure throughput and response time guarantees. We experimentally compare an implementation of Quorum both to hardware over-provisioning and to leading software approaches using real world workloads. Our results show that Quorum can enforce the same QoS guarantees as either of the compared approaches, while achieving better resource utilization than over-provisioning and without the application rewriting overhead required by intrusive software approaches. We also demonstrate that our implementation can successfully handle extreme situations such as sudden traffic surges, application misbehavior and node failures. Furthermore, we demonstrate the flexibility of Quorum by providing QoS guarantees for a complex and heterogeneous Internet service that cannot be implemented by other current software approaches. 1

We consider the issue of routing requests for virtual circuits in a Virtual Path (VP) based ATM network. We suppose that the VPs are partitioned in a manner such that all the VCs making use of any given VP have the same traffic characteristics and quality of service demands. A virtual circuit request can be accepted in the network only if the specified loss and delay bounds can be guaranteed for the cells belonging to it. After making suitable simplifying assumptions about the operation of the network, simple admission rules for virtual circuit requests are proposed. Routing policies are then proposed that try to minimize the fraction of virtual circuit requests denied. Simulations are carried out to evaluate the proposed routing policies. 1 Introduction Networks employing Asynchronous Traffic Mode (ATM) are required to support real time services in a packet switched environment. Real time traffic differs from traditional data traffic in several ways, the most important being that it ...

Many researchers have explored enhancements of the Internet's best-effort service model that allow real-time and other inelastic applications to obtain preferential Quality of Service. However, these applications are limited to utilizing the opportunistic, shortest-path routes provided by the current routing infrastructure. To better support real-time applications, this paper introduces extensions to interdomain multicast routing to scalably compute and install alternate paths and non-opportunistic, or pinned, routes. We present a simple multicast setup protocol for installing alternate paths and discuss how it prevents loops. Furthermore, we include the results of a simulation study to demonstrate the viability of using localized route construction to find adequate alternate paths. 1 Introduction The Internet has been extremely successful supporting elastic applications with best-effort service [Cla88]. However, best effort service can result in large and widely varying end-to-end pa...

High transmission speeds, increased burstiness of traffic, and statistical multiplexing of traffic render traditional approaches to network management and control ineffective. This thesis develops insight into the operation and performance of high-speed networks by developing tractable models and approximations. The insight gained is utilized to propose ways of enhancing the efficiency of network resources and facilitating ease of network management and control. Dynamic routing algorithms for routing Virtual Circuits (VCs) in Asynchronous Transfer Mode (ATM) must take into account their heterogeneous bandwidth characteristics and quality of service requirements. We classify ATM networks according to the network characteristics which have the greatest bearing on the performance of dynamic routing algorithms and discuss appropriate routing algorithms for each cla...

We study dynamically rearrangable end-to-end transport networks by means of SDH/SONET and/or ATM virtual paths. The concept and its advantages are brie y reviewed and we propose a new algorithm for designing such networks. Our algorithm provides integer solutions, handles non-linear equivalent bandwidths, nds its own paths, and allows for an arbitrary design optimisation criterion. It is found to perform equal to or better than an earlier, comparable though more restricted, algorithm. We also put forward a strategy for managing virtual paths in real time. It consists of a repeated cycle of on-line measurement of o ered tra cs followed by the design and implementation of a new virtual path network. Methods and parameters for tra c measurements and network updating frequency are studied and optimised. Applying the strategy to rearrangeable networks subject to variable tra cs in a simulator, we discover considerable gains and a robustness in our parameter settings.