2002 - cesnet

InternetNTPEthernetKPCPPSLabelPPSLabelFKPPS+10 MHzEtalonGPSFigure 20.1: Functional components of the servermunication with the KPC control computer. For communicating with the FKmicrocomputer, a serial port is utilized.We applied so called nanokernel patch to the Linux operating system kernel (2.4family). The patch contains the support for the PPS signal processing and modifiesthe kernel so that it works with time in nanosecond resolution. Moreover,the kernel has been extended with our own driver for the special PCI card.Furthermore, there are two processes running on the computer:• pps_gen is designed to generate a second signal derived from the internalNTP server time. This signal is compared with the time standard in FKand the deviation measured determines the internal time error of the NTPserver. The measurement is done with the accuracy of 100 ns.• ntp_deny is the process that enables or disables the output of all time informationfrom the NTP server (i.e., the NTP, TIME, and DAYTIME service)to the public network depending on the requirements of the kpctrl processfrom KPC.High-speed National Research Network and its New Applications 2002201