Recent studies provide evidence that Quality of Service (QoS) routing can provide increased network utilization compared to routing that is not sensitive to QoS requirements of traffic. However, there are still strong concerns about the increased cost of &OS routing, both in terms of more complex and frequent computations and increased routing protocol overhead. The main goals of this paper are to study these two cost components, and propose solutions that achieve good routing performance with reduced processing cost. First, we identify the parameters that determine the protocol traffic overhead, namely (a) policy for triggering updates, (b) sensitivity of this policy, and (c) clamp down timers that limit the rate of updates.Using simulation, we study the relative significance of these factors and investigate the relationship between routing performance and the amount of update traffic. In addition, we explore a range of design options to reduce the processing cost of QoS routing algorithms, and study their effect on routing performance.Based on the conclusions of these studies, we develop extensions to the basic QoS routing, that can achieve good routing performance with limited update generation rates. The paper also addresses the impact on the results of a number of secondary factors such as topology, high level admission control, and characteristics of network traffic.

Absrrucr-We discuss an implementation of QoS routing extensions to the OSPF routing protocol and evaluate its performance over a wide range of operating conditions. Our evaluations are aimed at assessing the cost and feasibility of QoS routing in IP networks. The results provide insight into the respective weights of the two major components of QoS routing costs, processing cost and protocol overhead and establish strong empirical evidence that the cost of QoS routing is well within the limits of modern technology and can be justified by the performance improvements.

Constraint-based routing gradually becomes an essential enabling mechanism for a variety of emerging network services such a s virtual private networkin and QoS su port A number of recent works have recognized its significance a n i investigate 8 m a n y aspects of the operation of constraint-based routing and in particular its variant concerned with determining paths for requests with specific QoS require ments, known as QoS routing. In this work we build on previous results on the cost of QoS routing and investigate the performance/cost trade-offs involved in the operation of a representative QoS routing architecture, elaborate on the constituents of this cost, and identify the main methods for containing the cost that QoS routing incurs on routers. Our results show that the cost of QoS routing is not excessive a n d that there indeed exist o erationol configurations, which can cost when compared to conventional best-effort routing.achieve reasonable performance gains wit R only a minimal increase in processing outing in IP nchvorks has so far been hascd on a besteffort service model, in thc sense that established routing protocols build routing tables with the only objective of minimizing the administrative cost of cach path. Emergcncc of multiple service offcrings in IP networks, some of which rcquirc service level assuranccs such as reliability, bounds on bandwidth availability, and dclay and packet loss have sparked interest in developing routing protocols for IP networks that are capable of accommodating such constraints (i.e., constraint-based routing). A constraint-based routing protocol can generate paths that satisfy certain spccified constraints, such a s routing policy constraints or quality of service (QoS) constraints. Routing with QoS constraints is also known as 00s routing, and is a longstanding research topic that has recently receivcd rcnewed attention [l-51 (scc [6] for an overview). In particular, some of the recent focus has bccn directed at assessing the impact of deploying QoS routing protocols in IP networks, as well as developing techniques that achicve the best cost-pcrforrnance trade-off for the constraints of most relevance in 1P nctworks (e.g., available bandwidth). Initial efforts have bccn primarily directed at thc intra-domain version of thc problcm, and this is what wc focus on in this article.The main benefits of QoS routing are thrccfold: it enables creation of virtual-circuit-likc scrvices over IP networks, improvcs user satisfaction by incrcasing chanccs of finding a path that meets thc QoS constraints, and improvcs network utilization by finding altcrnatc paths around congestion spots. Howcvcr, these benefits come at thc cost of dcveloping new routing protocols or enhancing existing ones, and of incurring potcntially higher communication, proccssing, and storagc overheads. As a result, an important concern is whcthcr or not QoS routing's benefits arc worth its cost. Answering such a question requires both expcrimentation and quantitative analysis, to better assess thc cos...

One of the key issues in deployment of QoS is determining the set of applications or users, which are allowed to have a preferential access to network resources. The administrative criteria for regulating access to resources constitute the QoS policies. A policy could determine which of the reservation requests in the network be honored during the processing of a signaling protocol such as RSVP, or it could determine the class of applications or users which are to be placed in a specific DiffServ class of service. In this paper, we look at the issues that arise in the definition, deployment and management of policies related to QoS in an IP network. The paper provides an overview of the requirements for QoS policies, the alternate policy architectures that can be deployed in a network, the different protocols that can be used to exchange policy information, and the exchange of policy information among different administrative domains. We provide a coverage of the current issues being examined in IETF and other standard bodies, as well as issues explored in policy related research ongoing at different universities and research labs.

No abstract

No abstract

ÐThis paper considers the support of hard real-time connections in ATM networks. In an ATM network, a set of hard realtime connections can be admitted only if the worst case end-to-end delays of cells belonging to individual connections are less than their deadlines. There are several approaches to managing the network resources in order to meet the delay requirements of connections. This paper focuses on the use of traffic regulation to achieve this objective. Leaky buckets provide simple and userprogrammable means of traffic regulation. An efficient optimal algorithm for selecting the burst parameters of leaky buckets to meet connections' deadlines is designed and analyzed. The algorithm is optimal in the sense that it always selects a set of burst parameters whose mean value is minimal and by which the delay requirements of hard real-time connections can be met. The exponential size of the search space makes this problem a challenging one. The algorithm is efficient through systematically pruning the search space. There is an observed dramatic improvement in the system performance in terms of the connection admission probability when traffic is regulated using this algorithm. Index TermsÐATM network, hard real-time communication, network delay analysis, traffic regulation.

No abstract