TSP Lab	Gy4 - The NTP Client	Gy4

The NTP Client module
`("Gy4")`

Features

Periodically synchronizes the local clock to a high precision Network Time Protocol (NTP) server's clock
Re-tries the sychronization when the previous one was unsuccessful
Logs it operation
Synchronization can be done manually
Icon is moved from taskbar to system tray if minimized

Basic operation

Sends six queries to the predefined NTP server, e.g. routers/gateways of the ethernet network usually provide this kind of service
If at least one of the six queries was successful the local clock is adjusted by that shift value which has the smalles round-trip-time (RTT)
When the interrogation of the NTP server was unsuccesful the module retries the synchronization after a predifened value (Gy4.ini/[Advanced]/dwQueryDelaySecWhenFailed)

User interface

Parts of the user interface

Status
- 60 queries sent to 192.168.0.1 (0 failed); 60 answers received (100% ready).: Indicates how many queries were sent to and how many answers were received from the given NTP server
- Last shifted +15ms at 2008.11.12 10:53:19.199 (local time).: Shows the last timecorrection value and when the local clock was adjusted
- Next query will start in 379 seconds; i.e., at 2008.11.12 11:07:57 (local time).: Displays the remaining seconds to the next query
- Reset: Zeroes values of the first line
Restart queries: Press this button to start the interrogation manually
Apply required shifts: If checked the time will be adjusted otherwise only the queries will be done and the local timer will not be shifted
Exit: Quit from the module
Elements of the result screen:
- Tx time here (UTC): timestamp of the NTP query (in UTC format)
- Rx time here: timestamp of the answer
- RTT [ms (us)]: round trip time (see Note for details!)
- Ref time at server: time value in the answer of the NTP server
- Shift required [ms]: the difference of the timestamps of query and answer revised by the half of the RTT (RefTime-TxTime-RTT/2)

Note: RTT coloumn has two values because Windows operating system usually provides two different timers to measure the time. One of them is the LoRes or System timer and less precise but it is always available. The other one (HiRes or MM timer) is more precise and theoretically not available in all versions of Windows operating system. The latter one's value is shown in parenthesis. The Gy4 NTP Client uses the LoRes value to decide the RTT because local timer has this resolution.

Configuration (INI) file settings

Section	Entry	Example	Meaning
[Settings]
	bApplyRequiredShifts	True	(Refer to the `Apply required shifts` checkbox!)
[Advanced]
	iLocalTimeOffsetSec	0	Local time can be shifted by this value
	dwQueryDelaySecWhenOK	900	Period of the synchronization
	dwQueryDelaySecWhenFailed	120	The next query will start in this time
	dwRTTMaxMS	200	Defines the maximal round-trip-time. If the a RTT is greater than this value the answer of the NTP server will not be considered
	dwShiftAbsoluteMaxSec	3700	The modul can not adjust the local clock when the difference is greater than this value
	sLogFilesPath	d:\LogFiles	Path for the log file
	sNTPServer	192.168.0.1	Defines the NTP server address
	sPCAPDevice	rpcap://\Device\NPF_{12345678-ABCD-1234-5678-123456789ABC}	PCAP interface for high-resolution round-trip time measurement

Version history

v1.03

(n) Alternate high-resolution round-trip time measurement via pcap interface.
(n) INI/[Advanced]/sPCAPDevice

v1.02

(c) HiRes round-trip time is given in microseconds [us], used to be given in [ms].

v1.01

(f) Reported unsuccessful query if exactly +/-0 ms were to be set.

v1.00

(c) Icon is moved from taskbar to system tray if minimized on start-up.

v0.92

(f) Day-of-month was incorrectly calculated in some cases.
(f) Only the very first character of TimeZone's StandardName and DaylightName was logged.