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Overview
SNTP stands for Simple Network Time Protocol.
Computers can use SNTP to get accurate time.
MasterSyncPC, a small program running on Microsoft Windows on a PC,
uses SNTP to make that PC's clock accurate by synchronizing it to a reference.
That reference is called an SNTP server, or time server,
which sends time data over a network.
That network can be the Internet or the Ethernet LAN that your PC is on.
An SNTP server is a software program running on a microprocessor--like
the one in a PC or in a special purpose network device
like the ones that Masterclock makes.
This server can respond to requests for the time or send out the time periodically
without being asked, or both. "The time" is a packet of data holding timestamps
referenced to UTC time, which is the time at Greenwich, England.
MasterSyncPC corrects your PC's clock by using those timestamps.
Making a request for time is called polling the server.
When the server sends time packets without being asked it is said to be broadcasting.
If you put a time server on your own Ethernet LAN then MasterSyncPC can poll it
or listen for its broadcasts, but an Internet time server will only be polled
because the broadcasting of SNTP time is not done on the Internet.
Time servers on the Internet are of 2 levels or strata.
Those in Level 1 are extremely accurate, and have the task of serving time to those in Level 2
that in turn respond to requests from the public.
Only Level 2 servers are appropriate for use by MasterSyncPC,
as those in Level 1 should not be queried by end users, and are likely to be too busy.
Even a level 2 server may be very busy.
This is noted on the website of U.S. servers
http://tf.nist.gov/tf-cgi/servers.cgi
Note that website recommends some servers for new users.
NIST servers are available to anyone on the Internet from anywhere on earth,
but there are many servers that restrict their responses to requests from within a "service area".
Here's a website that makes that clear, for servers all over the world:
http://support.ntp.org/bin/view/Servers/StratumTwoTimeServers
If you find several servers in those lists that you want to use,
MasterSyncPC lets you record them in a Custom Servers list.
One cannot count on any server to be functioning at any time.
They may be unavailable due to maintenance, power outages, lack of funding, etc.
For all such uncertainties MasterSyncPC has provision for 2 servers,
a primary and a secondary, and a test facility for each.
The primary will be used as long as it responds with valid time,
and the secondary will be used if the primary fails.
If both servers fail then the program notifies the user so that he can choose new servers.
This scheme ensures that the PC is kept in sync when the primary is down for maintenance
and alerts the user of communication failure,
which is the probable reason for the failure of both servers.
Often an institution like a college or government agency will have more than one time server
available, but you should choose a secondary server that is at a different location than the
primary so that maintenance and power outages don't affect both at the same time.
The NIST website given above lists scheduled maintenance for its entries.
The Internet time servers we have been speaking of respond to queries; they do not broadcast.
A time server installed on an Ethernet LAN can do both. MasterSyncPC can sync either by sending
a query or listening for a broadcast. In the first case it's in Poll mode, and in the second
it's in Listen mode. There's a menu item on the main window of MasterSyncPC where the user
chooses the mode. When the user selects Listen a window appears in which to state
the time to wait for a broadcast. If none is received within that time then the program
alerts the user. No more configuration is needed, but before using Listen mode the user
should make sure that a broadcasting SNTP server exists on his network,
that it is broadcasting, and that it broadcasts often enough to provide the accuracy needed.
MasterSyncPC cannot detect those things.
Note also that in Listen mode there is no secondary server as backup,
and there is no restriction upon which server´s broadcast is used.
The program then listens for, and uses, any SNTP broadcast.
But if the user chooses Poll mode then he gets to choose a specific sever,
set a specific backup server, and immediately test both to see if they're active
and respond quickly enough. Also, the user gets to query as often as he wishes (within reason).
There is one remaining problem with Listen mode:
it conflicts with the service called Windows Time, also known as W32time.
You cannot switch to Listen mode until you stop that service,
as a message box will tell you should you try.
To do so, right-click on My Computer and choose Manage.
In the pane that appears expand 'Services and Applications' on the left
and then click on 'Services'. All of your PC's services will appear on the right.
Find 'Windows Time', right-click on it and choose Stop.
At this time you could disable the service to make sure it doesn't re-start.
Alternatively, you could open a command window (Start -> Run)
enter "net stop w32time" and hit OK.
It may be that you have software installed on your PC that relies on Windows Time.
It is beyond the scope of this document to instruct you on how to find out
what those dependent programs are.
You will simply have to use Poll mode so that Windows Time can keep running.
MasterSyncPC has the requirement that the program and a file that it needs must be in the same folder.
These are the files MasterSyncPC.exe and MasterSyncPC.ini.
No installer is necessary; you can simply drag those files into place wherever you wish,
although the standard for our software is C:\Program Files\Masterclock
The .exe file holds the program code--an MFC application that will run on
Windows 2000
Windows XP
Windows Vista (both 32 and 64 bit)
Windows 7
The final need is Ethernet or Internet access to an SNTP server.
Public SNTP servers exist on the Internet, so you don't have to provide your own.
In fact, the .ini file is just a text file of the URLs of the best-known Internet SNTP servers.
The program reads this file to show those servers to you in a list
so you can choose a pair as your primary and secondary servers, in Poll mode.
A server can be referred to by URL (as in nist1-sj.witime.net) or IP address (as in 64.125.78.85).
That .ini file can also list servers that the user enters,
like those on your local area network that only users of that network would know about.
For instance, a Windows Small Business Server or Enterprise Server can host an SNTP server.
Also, you could buy a Masterclock generator that serves time, such as the MCR1000, MCR5000
or one of our NTP100 series, and install it on your network.
Then you would open MasterSyncPC, click on Servers, put the IP address or URL
of the server into the field labeled "Enter a new Custom Server",
and click the button "Add to Custom Servers".
Your entry can immediately be designated primary or secondary server, and can be tested
to make sure you can communicate with it and that it has been properly set up.
Here's a little advice on network organization.
Anyone with lots of PCs to synchronize should have their own SNTP server
with its PCs polling it or listening to it.
If that that in-house server synchronizes to a Stratum 2 server on the Internet
then this scheme takes load off of the Stratum 2 server, and decreases Internet traffic.
A smart tactic is to have the in-house server as Primary, and an Internet server as Secondary,
in Poll mode, because the failure of both is extremely unlikely.
Or you could buy an NTP100, MCR1000 or MCR5000 from Masterclock and put it on your network.
These genererators can reference very accurate, stable sources,
like GPS satellites or high-stability oscillators.
After installing MasterSyncPC double-click on it to start it running.
A small window should appear, filled mostly with the time and date of your PC's clock.
If you don't see that pane then check the tray area of the Windows taskbar
and look for a blue clock symbol. This is how MasterSyncPC appears when it's minimized.
(It may first appear minimized if your installation is actually a re-installation.)
First the easy stuff: Open the View menu and choose "Foreground Color..." and "Background Color..."
to set the display the way you like it. They will be saved in case you exit the program.
A new installation should be configured so that polling is done of an NIST server on the Internet.
The first synchronization will happen immediately after the program's launch,
and you will be informed of this in the message bar at the window's bottom left
with the time of sync and the amount of correction.
Please click on the Servers menu item and see if the "Sync Interval" and "Max Correction" are what you wish.
The program will count the interval down to zero and then poll the server in use.
It then corrects the PC's clock using the time from the server,
but not if the correction that it computes is over the max;
this is a safeguard to prevent an erroneous time being set due to a malfunctioning server.
(Note that the least interval is 15 seconds; even if you enter a lower it will not be recorded,
because polling a server too often could be interpreted as a denial of service attack.)
You can now consider your work complete if you're happy with the standard servers.
Close the Server Configuration pane and minimize the program. You should see its icon appear in the tray.
If you want to switch servers then fill in their URL or IP address by hand or select from the lists.
The one provided is called Standard Servers--a list of well-known Internet SNTP servers.
Note there is another list, called Custom Servers, which is for the user to fill with his own entries.
These can be Internet or local area network servers, listed by URL or IP address.
Highlight a server in either list, then make it Primary or Secondary by use of
the buttons between the lists. The highlighted entry will be copied into place.
Be sure of your selections by use of the "Test Primary" and "Test Secondary" buttons.
These do immediately polls and display results gotten from the timestamps in the SNTP packet.
When MasterSyncPC polls it sends the time of the request in the packet.
The server copies this stamp to the response packet, along with the time at which it received the request.
The third timestamp is the time at which the response was dispatched,
and the last is that of its reception by the program.
The first two timestamps are used to figure the "Request Travel Time",
the last two to figure "Response Travel Time", and the middle two the "Server Processing Time".
Note that the travel times will not be accurate unless your PC is already synchronized,
as one timestamp involved in each is gotten from your PC's clock.
Of course, there is provision for a secondary server so that it can be used if the primary fails.
The program will do this automatically, but it will also tell you that the server in use failed.
The need for this arises from practical considerations: servers can fail, go down for maintenance,
be taken off line due to lack of funding, be swamped by too many requests, etc.
The secondary will remain in use until it too fails, and the primary will be tried.
If it too is unresponsive then you will be notified.
Closing the Server Configuration pane by hitting OK causes a switch to the primary.
You will notice a button labeled "Swap" in between the Primary and Secondary entries.
It does exactly that, so if the pane is then closed via OK the settings for
Primary and Secondary server are swapped.
Closing with the Cancel button prevents any change in recorded settings.
It may be that you don't want to poll a time server. This would be true of an organization
with a LAN on which it has installed its own SNTP server.
As mentioned above, that could be a Windows server with an enabled SNTP service
or a special-purpose network device like the ones that we sell: an NTP100, MCR1000 or MCR5000.
In such circumstances it makes sense to put MasterSyncPC into Listen mode instead of Poll.
The program will simply wait for a broadcast SNTP packet from the server,
and synchronize the PC whenever one arrives. A big advantage of this is a decrease in network traffic.
To flip over to Listen mode open the Mode menu and choose "Listen for a Broadcast",
which presents a little dialog in which to state how long you are willing to wait.
Should MasterSyncPC not hear a broadcast in that time it will tell you so.
On this dialog you can also reset the timeout and state the maximum correction you want to allow.
Hitting the OK button saves your changes but canceling discards them and leaves the mode unchanged.
OK also deletes and recreates the communications socket and disables the Servers menu
because that menu only applies to Poll mode.
MasterSyncPC can write data describing the synchronization events to a log file,
and do simple analysis of that data. The log file is created for you, alongside the executable.
Open the Options menu and click on "Logging and Statistics..." to set it up.
There you can turn logging on or off, see the size of the log, clear it,
rotate the current log to a backup, set how many backups to keep,
and configure automatic rotation based on a size or time limit.
On the same panel you see the statistic that the program figures by reading the current log.
The data is plain text in comma-delimited format.
You can open the log file with any text editor to see this.
This format was chosen so you could import the file into a spreadsheet.
Statistics are shown only for the current log, called MasterSyncPC.log.
The backup logs are named MasterSyncPC.log.1, MasterSyncPC.log.2, etc. up to the limit you've set.
You don't need to be careful with the log files. The program can write to the current log
even if you have it open. If you move or delete the log it will be recreated automatically.
Under the Options menu are 3 settings to control how MasterSyncPC starts and appears.
"Minimize to Tray" will keep the program running and put a little icon in the Taskbar Tray
when the minimize button (near the upper right) is hit.
"Run at Startup" means the program will re-start whenever the PC does.
"Start Minimized" means that the program's main window will not appear upon program start;
only the tray icon will appear.
Be aware that if you choose File -> Exit or hit the close button at upper right
you will be ending the program, and it cannot then synchronize your PC.
(This version of MasterSyncPC is not a service.)
You will be notified of the option to minimize to the tray, which keeps the program on the job.
Under the Help menu is an Instructions choice that displays the briefest possible setup steps.
Also there is "MasterSyncPC Help Page" which is a web page on www.masterclock.com.
That page is what you are reading. It has the most thorough and up-to-date information.
Of course, you can get an answer from a real person.
Please use this link to see all of those options.
