Nortel Networks Mediant TP-1610 SIP - Manual (Page 64)

Mediant 2000 SIP
Mediant 2000 SIP User’s Manual 64 Document #: LTRT-72504
maintenance, and debugging actions become simplified for the network administrator.
The NTP client follows a simple process in managing system time; the NTP client requests an
NTP update, receives an NTP response, and updates the local system clock based on a
configured NTP server within the network.
The client requests a time update from a specified NTP server at a specified update interval. In
most situations this update interval should be every 24 hours based on when the system was
restarted. The NTP server identity (as an IP address) and the update interval are configurable
parameters that can be specified either in the ini file (NTPServerIP, NTPUpdateInterval
respectively) or via an SNMP MIB object.
When the client receives a response to its request from the identified NTP server it must be
interpreted based on time zone, or location, offset that the system is to a standard point of
reference called the Universal Time Coordinate (UTC). The time offset that the NTP client should
use is a configurable parameter that can be specified either in the ini file (NTPServerUTCOffset)
or via an SNMP MIB object.
If required, the clock update is performed by the client as the final step of the update process.
The update is done in such a way as to be transparent to the end users. For instance, the
response of the server may indicate that the clock is running too fast on the client. The client
slowly robs bits from the clock counter in order to to update the clock to the correct time. If the
clock is running too slow, then in an effort to catch the clock up, bits are added to the counter,
causing the clock to update quicker and catch up to the correct time. The advantage of this
method is that it does not introduce any disparity in the system time, that is noticeable to an end
user, or that could corrupt call timeouts and timestamps.