42486395
On a class of Banyan networks and tandem Banyan switching fabrics
The operating characteristics of a class of tandem banyan switching fabrics (TBSFs) built using bi-delta networks are examined. Functional equivalence between bi-delta networks induces an equivalence between TBSFs as well. A weaker form of equivalence guaranteeing identical performance under the conditions of symmetric traffic is studied, and sufficient conditions for weak equivalent between functionally distinct TBSFs is established. These results hold for a variety of conflict resolution policies (CRPs). Simulations indicate that a TBSF constructed by cascading omega networks (or in fact any other TBSF in its weak equivalence class) performs better than the two TBSFs studied by F.A. Tobagi et al. (1991) and converges rapidly to a theoretical lower bound on the loss rate in the region of interest.<<ETX>>
20173388
Spectral Decomposition Approach for Transient Analysis of Multi-Server Discrete-Time Queues
Abstract Discrete time queueing systems are extensively used in modeling the ATM environment at the cell level. This paper examines the transient behavior of a discrete time FCFS multiple server queue. For the arrival process we assume a general discrete time Markovian batch arrival process, where the batch size distribution of the arrivals in successive slots is governed by a finite state discrete time Markov chain. We show that once the spectral decomposition of the “probability generating matrix” of the arrival process is obtained, the complete solution in the transform domain may be given. Using the complex analysis technique and Cauchy's integral formula, we present an efficient numerical method for the numerical calculation of a few performance measures of interest, namely transient probability of queue being empty, and the mean of the queue length distribution. We also generalize our numerical method in the situations where the superposition of a number of independent arrival sources are fed to the queue. It is shown that the numerical complexity of obtaining the transient solution in this case can be substantially reduced by using the approach based on the Kronecker product. The finite buffer case is also analyzed.
24760638
Performance study of Markov modulated fluid flow models with priority traffic
The steady-state performance of generic high-speed queuing system with priority traffic is studied, using the Markov modulated fluid models. the focus is on systems with traffic partitioned into two priorities according to a splitting factor alpha , so that low priority traffic can be discarded when congestion occurs. The results are used to further study issues of congestion control with priority traffic. In particular, the expected values, waiting times, variances of the buffer contents, and tail distributions are evaluated. It is found that the waiting time is more sensitive to changes of alpha than the buffer contents. This shows that for time-constrained traffic, the priority assignment is important for properly balancing the tradeoff between packet loss and delays. This model can be considered as a direct extension of the fluid-flow model to include priorities.<<ETX>>
5054397
The transient solution of time-dependent M/M/1 queues
The transient behavior of time-dependent M/M/1 queues is studied. The boundary probability function pi /sub 0/(t), which is the probability that the queue is empty at time t, is shown with analyticity arguments to satisfy a Volterra-type integral equation. The boundary integral equation is derived, and a numerical algorithm is used to solve the integral equation and to find the expected queue size from pi /sub 0/(t). The approach can be applied to many other types of time-dependent queues. Examples are given. >
15454854
TCP Quick-Adjust by Utilizing Explicit Link Characteristic Information
This paper investigates the utilization of explicit bottleneck link characteristic information in order to enhance TCP behaviors. We propose the TCP Quick-Adjust algorithm as an extension of TCP Quick-Start, to allow end nodes to quickly adjust their sending rate for ongoing connections according to the reported bottleneck link bandwidth. Our scheme is considered to be especially suitable to use in a mobile operator's controlled network domain, where it is possible to provide a subscribed mobile node with reasonably accurate access link and path information. The link characteristic information is piggybacked in IP mobility signaling in this paper. Using simulations, we show that TCP Quick-Adjust provides good performance in terms of link capacity utilization in the scenarios where vertical handovers can happen between two links with very different characteristics.
19257985
Proactive care-of address test for route optimization in FMIPv6
This paper proposes a practical scheme to run the care-of address test (part of the Return Routability test for Mobile IPv6 route optimization) in a proactive way in the context of the Fast Handovers for Mobile IPv6 (FMIPv6) protocol, so that the latency (normally one round-trip time between a mobile node and its correspondent node) caused by the care-of address test after movements can be removed or reduced. Proactive care-of address test can make the Return Rroutability protocol more suitable for delay sensitive applications especially when it is applied in conjunction with other Return Routability optimization schemes.
16418111
Levels of Independence in Aspect-Oriented Modeling
We are investigating the application of aspect-oriented principles as an aid toward improving the capabilities of domain-specific modeling. The approach, in general, provides transformations by weaving modeling aspects into a base model. The modeling aspects provide variation points within the model and can be used to drive the synthesis of the model into different artifacts. In this brief position paper, we describe how our current and future work improves the capabilities offered in a model-based tool. We highlight several levels of independence that make the approach applicable to numerous modeling situations.
18945895
Advances in Fuzzy Method for Natural Computing
Both natural computing and fuzzy method exhibit human-like mental processing. Natural computing is the field of research that works with computational techniques inspired in part by natural systems. Fuzzy method is an alternative to traditional notions of set membership and logic, and it occurs in many applications of engineering, science and medicine. This paper presents a survey of recent advances in fuzzy method for natural computing, such as fuzzy artificial neural networks, fuzzy genetic algorithms, fuzzy ant colony optimization, fuzzy artificial immune systems, etc. We utilize uncertainty handling capacity of fuzzy method for modeling ambiguity, and the learning ability of natural computing for efficiently traversing large search spaces.
16442444
A Context-Aware Policy Model to Support Autonomic Networking
Autonomic networking requires that the services and resources offered by the network at any specific time adapt to evolving changes in user needs, business goals and environmental conditions. This paper describes a rich and extensible context-aware policy model as part of the FOCALE autonomic network architecture. This context-aware policy model is built explicitly to support context-awareness that in turn enables the control loops in FOCALE to be adaptive.
18935532
Equivalent Inertia Moment in Linear Stability Calculation of Stepped Beam
In the process of simplifying the stability calculation for light main boom of crawler crane, the structure can be considered as non-symmetrical one with variable cross-section beam. The equivalence of the simply supported beam with asymmetrical cross-section has not been solved. This paper attains the equivalent inertia moment of the stepped beam with the small deformation by using the differential and energy methods. In addition, comparing with the software ANSYS, the results of differential method is better than energy method. Then the results of differential errors are amended and reduced. Then, the paper presents the equivalent inertia moment coefficients curves, which greatly simplifies the calculation process of critical load and provides the reference for boom design.
12801074
Studies on a Class of AWG-Based Node Architectures for Optical Burst-Switched Networks
We investigate a class of novel node architectures based on the static arrayed-waveguide gratings (AWGs) and tunable waveband converters (TWBCs) for optical burst-switched (OBS) networks. As compared to the other AWG-based architectures using tunable wavelength converters (TWCs) for switching, our design needs much fewer wavelength-converting devices, TWBCs, instead of a large number of TWCs (operating only on one wavelength at a time). Notwithstanding the inherent simplicity, AWG-based architectures, due to the static routing properties of AWGs, exhibit some internal blocking as compared to the strictly nonblocking OBS nodes employing SOA/TWC-based architectures. We address this issue in our design methodology to arrive at different candidate node architectures using multiple layers of AWGs. Our simulation results indicate that the proposed class of node architectures using TWBCs and multiple layers of AWG can offer acceptable blocking performance with a simple and cost-effective optical hardware for OBS networks.