A novel diffusion process with jumps to study an electronic-optical edge router

The article presents a diffusion approximation model applied to investigate the process of filling a large optical packet by smaller and coming irregularly electronic packets. The use of diffusion approximation enables us to include the general distributions of interarrival times, also the self-similarity of the input process, as well as to investigate transient states. We propose a novel diffusion process with jumps representing the end of the filling the buffer due to arrival of too large packet and we give the transient solution to this process. The model allows us to study the distribution of interdeparture times and the distribution of the space occupied in the optical packet

Implementation of modified AQM mechanisms in IP routers

The article is an attempt to answer the question if it makes sense to modify the way of choosing packets to reject inAQM mechanisms. Simulation and analytical research of RED and DSRED mechanisms shows that their efficiency grows when packet is received from the front of the queue. It is especially conspicuous when taking into account the self-similarity of traffic. However implementation of the above mentioned mechanisms in real router does not corroborate such a clear advantage over Drop-From-Front strategy. In this article the results of analytical, simulation and real router research based on the Linux operating system have been presented

Screening Tool for Desiccant Dehumidification Applications

A state-of-the-art software tool that calculates the benefits of desiccant-based air-treatment equipment is described. The software, a Desiccant Systems Application Screening Tool, is written in the WindowsTM environment to promote user-friendliness. Its graphical interface emphasizes the simplicity of using default values or, if desired, provides the user with the option of customizing the input. The program runs annual loads/energy calculations with the electric equipment selected by the user (from a library of typical systems) and compares performance of a conventional system to an alternative electric system supplemented with a commercially available desiccant dehumidifier providing the required air-conditioning performance. The screening tool uses DOE 2.1E as the computational engine, which runs in the background and is transparent to the user. In addition, the latest TMY2 meteorological data recently released from the Department of Energy National Renewable Energy Laboratory are used by the program. Output of the program provides the user with a clear comparison between the performance of a desiccant/electric system and conventional system installed in an identical application. Specifically, the comfort issues are emphasized by comparing the number of occupied hours when the relative humidity in the building exceeds 60% RH (or above specific RH set point, if controlled). The economics are compared based on the annual/monthly energy consumption and operating cost. A case study is presented

A diffusion approximation model of an electronic-optical node

Designing of smart edge routers and shaping the self-similar traffic in optical switched networks arise recently a lot of interest. Here, we propose an analytical approach which we consider useful in modelling and dimensioning of buffers in the edge routers between electronic and optical networks. We study a single buffer where packets of various sizes, classified by the class of service and the destination, are stored to build an optical packet of a fixed size. We already studied this problem with the use of simulation model, remarking that self-similar traffic at the entrance of such a buffer remains self-similar when leaving it. Now we are building analytical model based on diffusion approximation. and our previous contributions to this approach, i.e. a method to solve transient diffusion models. The model is used to analyse the process of buffer filling and a a numerical example proves that this approach may give reasonable results in relatively short (compared to simulation, especially simulation of transient states) time

Diffusion approximation as a modelling tool in congestion control and performance evaluation

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Stability and Dynamics of TCP-NCD (DCR) Protocol in Presence of UDP Flows

International audienceThe fluid-flow approximation models investigate with much success the dynamics and stability of TCP/RED connections. Their main assumption is that the fluctuations of variables characterizing the behaviour of the connections are relatively small, that enables the linearization of model and the use of traditional control analysis tools to obtain such measures as Bode gain, phase margins, tracking error or delay margin. In this article, preserving linear fluid-flow model, we propose its extension to the case when a network is composed of wired and wireless part. We consider a variant of TCP algorithm (TCP-DCR or its new version TCP-NCR) and fluid-flow differential equations representing the size of congestion window, mean queue at the bottleneck router and loss probability at a RED queue are supplemented with terms representing constant loss probability due to transmission in wireless part and probability that a fraction of these errors is recovered by a link level mechanism. The decrease of congestion window due to TCP mechanism is delayed to allow the link protocol to deal with the errors. The model considers the presence of uncontrollable UDP flows

Transport Time Distribution for Optimal Deflection Routing on an Odd Torus

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