AudioCodes Mediapack mp-11x, Руководство пользователя

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Version 5.2 371 August 2007
SIP User's Manual 8. Networking Capabilities
The first packet arriving on a newly opened channel sets the source IP address and UDP
port from which further packets are received. Thus, the source IP address and UDP port
identify the currently accepted stream. If a new packet arrives whose source IP address or
UDP port are different to the currently accepted RTP stream, one of the following occurs:
„ The gateway reverts to the new RTP stream when the new packet has a source IP
address and UDP port that are the same as the remote IP address and UDP port that
were stated during the opening of the channel.
„ The packet is dropped when the new packet has any other source IP address and
UDP port.
8.6 Multiple Routers Support
Multiple routers support is designed to assist the gateway when it operates in a multiple
routers network. The gateway learns the network topology by responding to Internet
Control Message Protocol (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, 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 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.
8.7 Simple Network Time Protocol Support
The 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 synchronizes 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 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 is every 24 hours based on when the
system was restarted. The NTP server identity (as an IP address) and the update interval
are user-defined that can be specified using the Embedded Web Server (refer to
'Configuring the Application Settings' on page
168 ), the
ini
file (NTPServerIP and
NTPUpdateInterval respectively), or an SNMP MIB object (refer to the
SIP Series
Reference Manual
).