In all the cases listed above the plausibility checks on the timing information fail, so the hybrid radio clock stops passing
any timing information on to the NTP server. The NTP server's stratum changes to a worse value to let the clients know
that the server's reference time source fails. The hybrid radio clock continues supplying time to the NTP server after all
error conditions have been removed and the error has been acknowledged by an operator.
If one or more additional LANTIME NTP servers are available on the network then clients which have been configured to
use all of them will automatically discard the LANTIME with the bad stratum and synchronize to another NTP server
which is operating correctly at a better stratum. If no redundant LANTIME is available, however, the clients will continue
to synchronize to the LANTIME with worse stratum. This way it is guaranteed that all the client devices on the network
operate using the same system time.
All changes of the reception status of one of the radio clocks, and also failure of the hybrid clock's plausibility check are
logged by the local Linux system and optionally reported across the network. If the hybrid receiver passes the status "not
synchronized" to the NTP server, or it has disabled time information output at all, then the alarm signal output of the
LANTIME/SHS/BGT is activated.
The GNU/Linux operating system of the LANTIMEs SBC (Single Board Computer) has been optimized to ensure a high
level of network security and reliability. A large display shows the state of the internal SHS receiver and the NTP
subsystem.
The configuration of the system can be done by using a standard web browser to access the extensive but
straightforward html interface. Alternatively a text based and menu driven setup utility can be started from the shell
prompt after logging into the unit via Telnet or SSH.
The security-related features of LANTIME time servers satisfy highest demands. The time synchronization data can be
reliably signed and secured by symmetric keys (MD5) and the NTP autokey procedures. This protects the clients
against manipulated time and man-in-the-middle attacks and allows them to verify that the NTP packets they received
were send by the LANTIME. Additionally the whole LANTIME configuration can be done by using encrypted channels
(e.g. SSH, HTTPS or SNMPv3). Every unused/unneeded protocol can be disabled in order to reduce possible points of
attack.
In order to support network management systems the LANTIME time servers offer an extensive SNMP interface, which
can be accessed by SNMP V1, V2.c and V3. It allows the monitoring of all relevant system parameters (including
operating system parameters, network interface statistics, detailed GPS and NTP status information as well as the
complete system configuration) and can be used to alter the LANTIME configuration via SNMP set commands, too.
LANTIME time servers are designed to be deployed in IPv6 networks, the NTP time synchronization as well as the
configuration interfaces (Web-based, SSH and SNMP) comes with IPv6 support. You can assign several IPv6
addresses and the system supports automatic configuration by IPv6 autoconf.
Because of its modular system architecture it is possible to equip a LANTIME time server with up to three additional
ethernet ports and a number of different reference time sources. Optionally several additional frequency-, serial string-
and pulse outputs are available and by combining two (even different) time sources and redundant power supplies,
high-availability systems are no problem. Besides that a collection of oscillators, from the reliable temperature controlled
base model (TCXO), the three excellent oven controlled variants (OCXO-LQ, -MQ and -HQ) to the high-end rubidium
based top model, offers a wide selection of holdover characteristics (e.g. when the GPS signal is disturbed or jammed).
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