In this paper we describe an efficient algorithm for the constrained shortest path problem which is defined as follows. Given a directed graph with two weights on each link e, a cost le and a delay te, find the cheapest path from a source to all destinations such that the delay of each path is no more than a given threshold. The constrained shortest path problem arises in Quality-of-Service-sensitive routing in data networks and is of particular importance in real-time services. The problem formulation and the algorithmic framework presented are quite general; they apply to IP, ATM, and optical networks.Unlike previous algorithms, our algorithm generates paths from one source to all destinations. Our algorithm is strongly polynomial, and is asymptotically faster than earlier algorithms. We corroborate our analysis by a preliminary simulation study.
The paper proposes a structure for quality-of-service (QoS)-centered service level agreements (SLA), and a framework for their real-time management in multiservice packet networks. The SLA is structured to be fair to both parties, the service provider and their customer. The SLA considered here are for QoS assured delivery of aggregate bandwidth from ingress to egress nodes; however, the control and signaling is for the more granular flows or calls. A SLA monitoring scheme is presented in which revenue is generated by the admission of flows into the network, and penalty incurred when flows are lost in periods when the service provider is not SLA compliant. In the SLA management scheme proposed here, the results of a prior off-line design are used, in conjunction with measurements taken locally at ingress nodes, to classify the loading status of routes. The routing and resource management are based on virtual partitioning and its supporting mechanism of bandwidth protection. The effectiveness of SLA management is measured by the robustness in performance in the presence of substantial diversity in actual traffic conditions. A simulation testbed called D'ARTAGNAN has been built from which we report numerical results for a case study. The results show that the SLA management scheme is robust, fair and efficient over a broad range of traffic conditions.
ATM network design and optimization at the call-level may be formulated in the framework of multirate, circuit-switched, loss networks with effective bandwidth encapsulating cell-level behaviol: Each service supported on the ATM network is characterized by a rate or bandwidth requirement. Future networks will be characterized by links with very large capacities in circuits and by many rates. Various asymptotic results are given to reduce the attendant complexity of numerical calculations. A central element is a uniform asymptotic approximation (UAA) for link analyses, Moreover, a unijied hybrid approach is given which allows asymptotic and nonasymptotic (exact) methods of calculations to be used cooperatively. Network loss probabilities are obtained by solving jixed point equations. A canonical problem of route and logical network design is considered. An optimization procedure is proposed, which is guided by gradients obtained by solving a system of equations for implied costs. Finally, we report numerical results obtained by the software package TALISMAN, which incorporates the theoretical results. The network considered has 8 nodes, 20 links, 6 services and as many as 160 routes,
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