The Domain Time II Ultra Thin Client is a special-use broadcast-listener time client that runs as a background service
on Windows systems. It is designed to be an extremely low overhead, high-accuracy service that synchronizes directly with
any NTP broadcast server or Domain Time II Server configured to provide Broadcast Time using
a special type of Heartbeat time broadcast.
The Ultra Thin Client has no user-definable configuration options. However, variance reporting and time zone
features can be set by an administrator using the Domain Time II Manager program,
and certain options can be pre-configured during installation using the DOMTIME.INI file (see the
Domain Time II Manager, Advanced Tab instructions for details).
To get a free 30-day evaluation copy of the fully-functioning program, download it from the
Greyware Evaluation Center.
If you have already registered the software, download the registered version directly from your
Greyware Account page.
Reliability and Security Considerations
Important: Broadcast Time should only be used when there is a specific requirement for it. Broadcast Time does not scale well beyond a single subnet,
and doesn't offer any redundancy in the event the broadcasting server becomes unavailable. It is also inherently more susceptible to disruption by the inadvertent
or malicious introduction of conflicting broadcast servers onto the network. See the When to use
Heartbeats and NTP Broadcasts page to determine whether Broadcast Time is an appropriate solution for your network.
When first installed, the Ultra Thin Client is set to accept any type of time broadcast (NTP Broadcasts or Domain Time Heartbeats) from any source. This basic
configuration is acceptable only if installed on a tightly-controlled network where there is no possibility of there ever being more than one broadcasting time
Since such control is difficult to guarantee on most networks, we highly recommended that you restrict the client to accept broadcast packets only from designated systems.
This can be done in the following ways:
- Before installation, edit the DOMTIME.INI template file used by Manager to remotely install the client.
- After installation, use Domain Time II Manager to connect to the Ultra Thin Client and change the Client Options.
- After installation, edit the appropriate registry entries for Ultra Thin Client.
If you choose to use Manager to secure the client, connect to the machine running the Ultra Thin Client by double-clicking on it in Manager's
Browse list. On the Connected to screen, click the Options icon.
This will bring up the Client Options screen (for a complete description of the Connected To... Client Options screen, see the
Domain Time II Manager documentation).
Click the Server Addresses button on this screen to bring up the configuration window, and enter the IP Address of the servers you want the
client to respond to. You can also set which type of broadcast protocol to accept on this screen.
Next, on the same Client Options screen, click the DT2 Commands button to bring up the Domain Time II Command Restrictions dialog.
You can use these settings to restrict what kind of Domain Time II control and sync messages your server listens for on the network.
The default protocol restriction settings assure both maximum functionality and a high degree of security; in most cases you will have no need to adjust them from the defaults.
Domain Time II components communicate with each other primarily through directed communication, and are therefore highly resistant to spoofing and malign
The Domain Time II protocol command restriction capability is intended for use by system administrators in environments where an extra level of
security is required, such as running a Server on the open Internet. Using the restrictions list, you can determine exactly what Domain Time II protocol
command messages the service is allowed to listen for. Think of the command restriction list as an application-level "firewall" allowing in only the
desired Domain Time II commands and blocking any others. Keep in mind that the restriction list only affects incoming DTII protocol commands - outgoing
commands are not affected.
Disabling protocol commands can have unintended consequences on the operation of your entire time distribution network, including the prevention
of cascade triggers and sync notifications, which may result in inaccurate clocks. Problems resulting from disabled protocol messages can be quite
hard to troubleshoot later, particulary by the next system administrator after you. Make adjustments only if you understand and require them, and be
sure you document the changes so you can maintain the consistency and smooth operation of your time network.
Synchronizing with a Broadcasting Server
The default settings for the Ultra Thin Client allow it to synchronize with any NTP Broadcast server, including *nix machines
and Domain Time II Server sending NTP Broadcasts. When an NTP broadcast is seen, the Ultra Thin Client synchronizes its time.
The Ultra Thin Client can also sync to a Domain Time II Server (version 3.1 or later) that is providing time broadcasts
using the Heartbeat (With Time Data) option. The Ultra Thin cannot use the older Advisory Only style Heartbeat. See
the Broadcast Time page for instructions on setting the
correct Heartbeat type.
When a Heartbeat (With Time Data) packet is received, the Ultra Thin Client will immediately set the system clock to match the time data in the packet.
Ultra Thin Clients ignore all other time synchronization and cascade messages.
If the Ultra Thin Client is receiving both NTP and Heartbeat broadcasts, it will use the broadcast type that is arriving more frequently (on the assumption
that this will result in higher accuracy). If you do not want this behavior, set the client to ignore the unwanted type of broadcast using Manager to connect to the
Client Options or by changing the relevant registry settings.
System Tray Applet
The Ultra Thin Client can display the DTTray System Tray Applet in the Start Bar system tray.*
The System Tray Applet provides visual and audible (if desired) confirmation that the system is correctly synchronized. It also allows a user to view the
Activity Monitor, see the Drift Graphs, client time statistics, etc.
Hint: Right-click the system tray icon to see the context menu.
The System Tray can also bring up an an extremely useful Broadcasts Statistics display showing the status of time broadcasts in real time.