Motorola V186 User Manual - Page 108
Configuring NTP Servers, User Protocol over IP, Dynamic IP Address, MDLC over IP Port Routing
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Communications Configuring NTP Servers An Ethernet or RS232 PPP port can be configured for NTP protocol (NTP is UDP port number 123.) In this case, the RTU will retrieve its time from a set of NTP servers specified by the user. The clock offset between the RTU and these servers depends on network delays, and may be up to 100 milliseconds in some wireless media. The clock offset on LAN in the same Ethernet network is approximately 1 millisecond. Note: It is possible to define an NTP server with a full host name (e.g. www.mysite.com). To do so, the user must set DNS servers for this port, either statically, or from a DHCP server or PPP modem. User Protocol over IP Both Ethernet and PPP ports provide an interface for a user application written in the 'C' Toolkit using MOSCAD_socket() functions, also known as "User protocol over IP". An MDLC over IP port can serve a user application at the same time as it serves MDLC which is built in the socket API. MDLC takes one logical UDP port number (2002 by default); other applications can use other TCP or UDP port numbers. For more information on the 'C' Toolkit socket functions, see the ACE3600 RTU 'C' Toolkit User Guide. Dynamic IP Address Many wireless networks do not allocate a fixed IP address to a PPP modem (such as the GPRS network). For the FEP to communicate with the RTU it must know its address or host name. Since these networks do not provide a name for each modem, there is no option of setting them in the FEP beforehand. In this case, the FEP should not be assigned an IP conversion table with that link ID (port). The RTUs should be associated with a table which has the FEP's IP address. If the network operator assigns a host name to the FEP instead of a numeric address, this can be set in the IP conversion table. When the RTU detects that its modem is connected, it will notify this address, the FEP, of its new IP address, thus updating its table in runtime. Since this process does not guarantee that the FEP will be updated, it is highly recommended that user application periodically send a message to the FEP. For example, if the user application expects an interrogation every two minutes from the FEP, and it has not received that, it will send a message to the FEP. This will update the RTU address in the FEP. MDLC over IP Port Routing In the example mentioned in Dynamic IP Address above, for RTU-to-RTU (modem to modem) communication, set 'Enable routing of MDLC over IP port' parameter in the FEP. Then assign to the RTUs an IP conversion table which list the RTUs' site IDs as having the FEP IP address. 104