5.Product Features
This section covers operational features that add versatility to the modem. Understanding these features helps you better plan the configuration that will best meet the needs of your installation.
Features covered include:
•Friends Only security
•Dial Directory (“Quick Dial”)
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•Sleep modes
•Remote diagnostics and monitoring
•Booster Support
The details of the features of the DART 300 are each covered with:
•A brief description of the feature
•A detailed discussion of it with respect to configuration and impact on other features
•Sample(s) of AT command sequences to implement the feature
5.1.Friends Only
For applications that allow the modem to answer incoming call requests (server mode), a security feature is available to restrict the modem to only answering “friendly” callers. Friends Only is available when either the UDP or TCP PAD (Packet Assembly / Disassembly) service is enabled, but is not used with the SLIP / PPP protocols.
If Friends Only is active, the modem will only respond to packets or connection requests from a source address in the Friends List. Connection requests from other sources are declined.
CAUTION
The Friends Only feature cannot be used if the calling client is behind a security firewall or other mechanism that might create “masquerade” IP addresses.
Details
When the Friends Only feature is active, the modem will check the source IP address of incoming packets. If the address is not on the Friends List: UDP packets are quietly discarded; TCP session requests are declined (ignored).
This feature requires that the calling system use a known, fixed IP address. If the network connection used by the monitoring station obtains an IP address through DHCP or some other dynamic IP allocation, then the feature will not be practical. Note that IP masquerading can also have an impact on the use of this feature.
The modem maintains a list of up to ten friends. If the table is not empty, the feature is enabled and the comparison of packet source addresses against the list stored in the modem will be made. If the table is empty (all entries are 000.000.000.000) then the modem will accept calls from any source.
There is also a space in each entry for a port number. The port number is only used for dialing features described below.
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