Performance evaluation of large capacity broadcast-and-select optical crossconnects

In this work, two bufferless high capacity broadcast-and-select optical switching node architectures are presented and their performance is evaluated. The architectures are modular permitting the expansion from basic to complex structures by adding new blocks/components in a gradual way, enhancing at the same time the corresponding network functionality. The blocking performance is assessed and scheduling algorithms are proposed to solve contention for a single node. Finally, physical layer modeling is carried out in order to investigate node scalability and node cascadeability. Overall, the proposed solutions are offering modularity, transparency to switching technology, graceful evolution and high performance at an affordable cost.     

Performance Analysis of ATM Replicated Banyan Networks with External Input–Output Queueing

This paper develops an improved analysis of ATM switching architectures adopting a replicated banyan interconnection network provided with dedicated input and output queues, one per switch inlet and outlet. Two different plane selection policies are studied, random choice and alternate sharing, and two different operation modes are considered for the interaction between input and output queues, backpressure and output queue loss. These different internal operations are ranked in terms of traffic performance and the problem of optimal allocation of a given buffer budget between input and output queues is addressed. The analysis, which assumes that the network is loaded by uniform traffic, always provides conservative results whereas known models are less accurate and give optimistic traffic results. Packet delay and loss probability performance is evaluated for the ATM switch and its accuracy is assessed using computer simulation also in comparison with results given by previous models.     

Performance analysis of ATM banyan networks with shared queueing.II. Correlated/unbalanced offered traffic

For pt.I see ibid., vol.2, no.4, p.398-410 (1994). The paper develops the analysis of multistage banyan interconnection networks in which the switching elements are provided with a buffer shared among all the inlets and outlets of the element. Two different internal protocols are considered for the transfer of packets from stage to stage based on the presence or absence of interstage backpressure to signal the occurrence of buffer saturation conditions. The analytical model is based on the representation of the switching element state by means of only two variables. Two kinds of offered traffic patterns are considered, a bursty balanced pattern and an unbalanced uncorrelated pattern. In this latter case, the load above the average is supposed to be addressed either to a single network outlet, or to a given group of network outlets     

Performance analysis of the ATM shuffleout switch under arbitrarynonuniform traffic patterns

Shuffleout is a blocking multistage asynchronous transfer mode (ATM) switch using shortest path routing with deflection, in which output queues are connected to all the stages. This paper describes a model for the performance evaluation of the shuffleout switch under arbitrary nonuniform traffic patterns. The analytical model that has been developed computes the load distribution on each interstage link by properly taking into account the switch inlet on which the packet has been received and the switch outlet the packet is addressing. Such a model allows the computation not only of the average load per stage but also its distribution over the different links belonging to the interstage pattern for each switch input/output pair. Different classes of nonuniform traffic patterns have been identified and for each of them the traffic performance of the switch is evaluated by thus emphasizing the evaluation of the network unfairness     

AS-level source routing for multi-provider connection-oriented services

In this paper, we study the inter-domain Autonomous System (AS)-level routing problem within an alliance of ASs. We first describe the framework of our work, based on the introduction of a service plane for automatic multi-domain service provisioning. We adopt an abstract representation of domain relationships by means of directional metrics which are applied to a triplet (ingress point, transit AS, egress point) where the ingress and egress points can be ASs or routers. Then, we focus on the point-to-point and multipoint AS-level routing problems that arise in such an architecture. We propose an original approach that reaches near optimal solutions with tractable computation times. A further contribution of this paper is that a heavy step in the proposed heuristic can be precomputed, independently of the service demands. Moreover, we describe how in this context AS-level path diversity can be considered, and present the related extension of our heuristic. By extensive tests on AS graphs derived from the Internet, we show that our heuristic is often equal or a few percent close to the optimal, and that, in the case of precomputation, its time consumption can be much lower than with other well-known algorithms.     

WDM Network Design by ILP Models Based on Flow Aggregation

Planning and optimization of WDM networks has raised much interest among the research community in the last years. Integer linear programming (ILP) is the most used exact method to perform this task and many studies have been published concerning this issue. Unfortunately, many works have shown that, even for small networks, the ILP formulations can easily overwhelm the capabilities of today state-of-the-art computing facilities. So in this paper we focus our attention on ILP model computational efficiency in order to provide a more effective tool in view of direct planning or other benchmarking applications. Our formulation exploits flow aggregation and consists in a new ILP formulation that allows us to reach optimal solutions with less computational effort compared to other ILP approaches. This formulation applies to multifiber mesh networks with or without wavelength conversion. After presenting the formulation we discuss the results obtained in the optimization of case-study networks.     

Bounds and Performance Networks of Reuse Partitioning in Cellular

In this paper we study a scheme that allows asmooth increase of the capacity of a cellular system forcircuit switching by applying cell partitioning andusing dynamic channel allocation techniques. A bound is computed for this reuse partitioningscheme that gives the maximum theoretical gainaccomplished in the system bandwidth. The performance ofthe proposed scheme in terms of blocking probability is evaluated both when the position of themobiles remains unchanged and when mobility is takeninto account. The numerical results show that thecapacity of the proposed scheme is sensibly higher than that of a fixed allocation scheme.     

Multistage shuffle networks with shortest path and deflectionrouting for high performance ATM switching: the open-loopshuffleout

A new class of switching architectures for broadband packet networks, called shuffleout, is described and analyzed in the paper. Shuffleout is basically an output-queued architecture with a multistage interconnection network built out of unbuffered b×2b switching elements. Its structure is such that the number of cells that can be concurrently switched from the inlets to each output queue equals the number of stages in the interconnection network. The switching element operates the cell self-routing adopting a shortest path algorithm which, in case of conflict for interstage links, is coupled with deflection routing. The paper presents the basic shuffleout architecture, called open-loop shuffleout, in which the cells that cross the whole interconnection network without entering the addressed output queues are lost. The key target of the proposed architecture is coupling the implementation feasibility of a self-routing switch with the desirable traffic performance typical of output queueing