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Designing the Switch/Router
Published in James Aweya, Designing Switch/Routers, 2023
The kernel is responsible for running a number of daemons that perform important tasks in the router. A daemon is a program that runs continuously as a background process with the sole purpose of handling periodic service requests that the system receives. Typically, in high-performance routing systems, each daemon operates in its own protected memory space. This protected memory space and the communication among the processes is also controlled by the kernel. This separation is done to provide isolation between the various processes running in the system, which leads to system resiliency in the event of a process failure. Such router resiliency features are important, particularly, in core routing devices, because the failure of a single process will not cause the entire device to cease functioning. Some common daemons (processes) in a routing device are discussed below.
Experimental Setup for Harmonic Impedance Measurement in a Real HV Power Grid
Published in Electric Power Components and Systems, 2019
Dariusz Borkowski, Andrzej Wetula, Jakub Kowalski, Szymon Barczentewicz, Jerzy Nabielec, Marek Rogóż, Ireneusz Szczygieł
The storage application is a multithreaded application running as a Unix service (daemon). Its architecture is shown in Figure 6. The main thread manages communication and storage threads as well as implements main state machine controlling a behavior of the application. States are changed by POSIX signals sent from a user control shell script. Following states are possible at the moment: ACQ (acquisition in progress), IDLE (acquisition is stopped, all incoming frames are dropped), RESET (used in the case of lost data transmission). User control is realized by a remote SSH connection. Such an approach allows for using both standard UNIX tools and a standard UNIX approach to control the behavior of the data storage application.