MP-1xx SIP
MP-1xx SIP User’s Manual 112 Document #: LTRT-65404
5.9.1.2 Multiple Routers Support
Multiple routers support is designed to assist the media gateway when it operates in a multiple
routers network. The gateway learns the network topology by responding to ICMP redirections
and caches them as routing rules (with expiration time).
When a set of routers operating within the same subnet serve as gateways to that network and
intercommunicate using a dynamic routing protocol (such as OSPF, etc.), the routers can
determine the shortest path to a certain destination and signal the remote host the existence of
the better route. Using multiple router support the media gateway can utilize these router
messages to change its next hop and establish the best path.
Note: Multiple Routers support is an integral feature that doesn’t require configuration.
5.9.1.3 Simple Network Time Protocol Support
Simple Network Time Protocol (SNTP) client functionality generates requests and reacts to the
resulting responses using the NTP version 3 protocol definitions (according to RFC 1305).
Through these requests and responses, the NTP client is able to synchronize the system time to
a time source within the network, thereby eliminating any potential issues should the local system
clock 'drift' during operation. By synchronizing time to a network time source, traffic handling,
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 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.
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