Space-time characteristics of ALOHA protocols in high speed birdirectional bus networks

Caption title.Includes bibliographical references (p. 27-28).Supported by the Defense Advanced Research Projects Agency. N00014-84-K-0357 Supported by the National Science Foundation. NSF-ECS-8310698 Supported by the Army Research Office. ARO-DAAL03-92-G-0115by Whay Chiou Lee and Pierre A. Humblet

Robustness of Ethernet-Based Real-Time Networked Control System with Multi-Level Client/Server Architecture

The importance of real-time communication at the device level in a factory automation setup is a widely researched area. This research is an effort to experimentally verify if Ethernet can be used as a real-time communication standard in a factory automation setup, by observing the effects of packet delays, packet loss, and network congestion on the performance of a networked control system (NCS). The NCS experimental setup used in this research involves real-time feedback control of multiple plants like DC motors and a magnetic-levitation system connected to one or more controllers. A multi-client-multi-server architecture on a local area network (LAN) was developed using user datagram protocol (UDP) as the communication protocol. Key observations are as follows. (1) The multi-client-single-server system showed the highest packet delays compared to single-client-single-server architecture. (2) In the singleclient- single-server system, as the Ethernet link utilization increased beyond 82 percent, the average packet delays and steady-state error of the DC motor speed-control system increased by 2231 percent and 304 percent, respectively. (3) Even under high link utilization, adding an additional server to the NCS reduced average packet delays considerably. (4) With large packet sizes, higher packet rates were automatically throttled by Ethernet’s flow control mechanism affecting the real-time communication negatively. (5) In the multiclient- multi-server architecture, average packet delays at higher packet rates, and at higher packet lengths were found to be 40 percent lesser than the those of the single-clientsingle- server system and 87.5 percent lesser than those of the multi-client-single-server system

Aplicação de desempenho para validar a gerencia pro-ativa de redes

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnologicoA gerência pró-ativa de redes visa resolver os problemas em uma rede antes que eles aconteçam. Para isso, é utilizado um perfil do comportamento normal da rede, conhecido como baseline. Para desenvolver a gerência pró-ativa, um modelo (ou arquitetura) com características básicas, tal como a baseline, o monitor remoto e a plataforma de gerência, foi proposto. Além disso, foi desenvolvida uma aplicação de gerência de desempenho baseada neste modelo, que caracteriza um protótipo experimental que demonstra o comportamento pró-ativo