2002 - cesnet

20.3 KPC Control ComputerThis computer is an older PC (Pentium 150 MHz) with the Linux operating system.For communicating with the outer world, the computer uses two networkadapters (its public IP address and the peer-to-peer connection with the NTPcomputer) and two serial ports (the FK microcomputer and the GPS receiver).KPC system processes:• kpc2 is the basic control multi-thread process, which collects and evaluatesinformation about the current time and NTP server status.• The kpclie process takes the data from the kpc2 process and presents themto a user in a well-organized form. Several kpclie processes can be runningsimultaneously, allowing for the system to be monitored from multiple locationsat the same time.• The kpctrl process implements the algorithm that decides on enabling ordisabling the provision of time services based on data provided by thekpc2 process. The kpctrl process hands its decisions over to the ntp_denyprocess using UDP datagrams.20.3.1 kpc2 ProcessThis process is the core of the KPC system. It collects the following data:• local KPC time• time labels from the FK microcomputer• measured deviation of the internal NTP server time (from FK)• time provided by all time services of the NTP server (i.e., the NTP, TIME,and DAYTIME protocol)• time from the external independent time server• time from the GPS receiverConcerning the aforementioned data, their availability and value is treated separately.The kpc2 process evaluates and sorts the data obtained and providesthem to other processes every second. It is necessary to emphasize that theGPS receiver is used only for the verification, not as a source of the referencesignal for the NTP server. Thus, the time server is not dependent on GPS.20.4 FK Microprocessor SystemThe FK system is a single-board microcomputer. Its input is represented by secondpulses from the time standard, accurate 10 MHz signal, and second pulses202 High-speed National Research Network and its New Applications 2002