Адаптивная стратегия распределения буфера в узлах телекоммуникационных сетей

Предложены приближенные формулы для вычисления вероятностей потерь разнотипных пакетов в сетях АТМ со стратегией ограниченного частичного распределения буфера. Описан новый подход к решению проблемы расчета характеристик качества данной стратегии, основанный на принципах теории фазового укрупнения состояний соответствующей цепи Маркова. Приведены результаты численных экспериментов, выполненных с использованием полученных аналитических зависимостей.Запропоновано наближені формули для обчислення ймовірностей втрат різнотипових пакетів у мережах АТМ із стратегією обмеженого часткового розподілу буфера. Описано новий підхід до вирішення проблеми розрахунку характеристик якості даної стратегії, заснований на принципах теорії фазового укрупнення станів відповідного ланцюга Маркова. Наведено результати чисельних експериментів із використанням отриманих аналітичних залежностей.Approximate formulae are obtained to calculate the cell loss probability for packets of different types in ATM networks with limited partial buffer sharing strategy. A new approach to solution of the problem of calculating characteristics of this strategy quality, based upon principles of state phase-aggregation theory, is offered. The results of numerical experiments performed by using the developed formulae are given

An Efficient Queueing Policy for Input-Buffered Packet Switches

An efficient self-adaptive packet queueing policy, called Queueing with Output Address Grouping (QOAG), is proposed for optimizing the performance of an input buffered packet switch. Each input port of the N×N switch under consideration has Q queues and each queue has B packet buffers, where 1<Q<N. Using QOAG, a packet arriving at an input port is assigned to the queue which has some backlog packets with the same output address as that of the new packet. If the output address of the new packet is different from all current buffered packets in all queues, it is assigned to the shortest queue. The performance of QOAG is compared with the Odd-Even queueing policy of Kolias and Kleinrock (see Proceedings of IEEE ICC '96, p.1674-79, 1996) by simulations. The Zipf distribution version II is used to model the non-uniform packet output distributions. We found that for a 16×16 switch with B=20 buffers at each queue and input load p=0.7, the mean packet delays are 58.1 and 91.2 time slots and the mean throughputs are 0.474 and 0.355 for using QOAG and Odd-Even queueing respectively. This represents a 57% cut in mean packet delay and 25% increase in throughput when QOAG is used.published_or_final_versio

The CMS Event Builder

The data acquisition system of the CMS experiment at the Large Hadron Collider will employ an event builder which will combine data from about 500 data sources into full events at an aggregate throughput of 100 GByte/s. Several architectures and switch technologies have been evaluated for the DAQ Technical Design Report by measurements with test benches and by simulation. This paper describes studies of an EVB test-bench based on 64 PCs acting as data sources and data consumers and employing both Gigabit Ethernet and Myrinet technologies as the interconnect. In the case of Ethernet, protocols based on Layer-2 frames and on TCP/IP are evaluated. Results from ongoing studies, including measurements on throughput and scaling are presented. The architecture of the baseline CMS event builder will be outlined. The event builder is organised into two stages with intelligent buffers in between. The first stage contains 64 switches performing a first level of data concentration by building super-fragments from fragments of 8 data sources. The second stage combines the 64 super-fragments into full events. This architecture allows installation of the second stage of the event builder in steps, with the overall throughput scaling linearly with the number of switches in the second stage. Possible implementations of the components of the event builder are discussed and the expected performance of the full event builder is outlined.Comment: Conference CHEP0

Simulation study of two-level forward error correction for lost packet recovery in B-ISDN/ATM

The major source of errors in B-ISDN/ATM systems is expected to be buffer overflow during congested conditions, resulting in lost packets. A single lost or errored ATM cell will cause retransmission of the entire packet data unit (PDU) that it belongs to. The performance of the end-to-end system can be made much less sensitive to cell loss by means of forward error correction. In this paper, we present the results of a simulation study for an ATM network where forward error correction is performed at both the cell level and the PDU level. The results indicate that (i) cell losses are highly correlated in time, and analytical models ignoring this fact will not yield accurate results, (ii) the correlation of cell losses is similar to burst errors in digital communication, and similar code interleaving techniques should be used, (iii) coding cells and PDUs separately provides this interleaving effect, and this joint code outperforms coding only at the cell level or only at the PDU level in almost all cases simulated

Extending the VEF traces framework to model data center network workloads

Producción CientíficaData centers are a fundamental infrastructure in the Big-Data era, where applications and services demand a high amount of data and minimum response times. The interconnection network is an essential subsystem in the data center, as it must guarantee high communication bandwidth and low latency to the communication operations of applications, otherwise becoming the system bottleneck. Simulation is widely used to model the network functionality and to evaluate its performance under specific workloads. Apart from the network modeling, it is essential to characterize the end-nodes communication pattern, which will help identify bottlenecks and flaws in the network architecture. In previous works, we proposed the VEF traces framework: a set of tools to capture communication traffic of MPI-based applications and generate traffic traces used to feed network simulator tools. In this paper, we extend the VEF traces framework with new communication workloads such as deep-learning training applications and online data-intensive workloads.Ministerio de Ciencia e Innovación y Agencia Estatal de Investigación (MCIN/AEI/10.13039/501100011033) R &D Project Grant (PID2019-109001RA-I00)Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL