Motorola V186 User Manual - Page 110
MDLC over IP Site Paging, Dynamic DHCP
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Communications • Static IP address mode • Dynamic (DHCP) With static IP address mode, the user is required to set the link ID, IP address, subnet mask and default gateway. If DNS or NTP servers are required, these must be defined as well. DNS servers are only required if this port is to be accessed via a host name rather than a numeric IP address. In this case the operator assigns a host domain name to the FEP or RTU. The IP conversion table must include the domain name well. If an NTP server is to be used to obtain the time, the numeric IP address or domain name of the NTP server must be defined. In DHCP address mode, the user is only required to set the link ID for this port. If DNS servers are required there is no need to set them, since they are learned from the network. If NTP servers are required, the user must set them since they are not learned from the network. As an option, user can set a full host domain name for an Ethernet port that is configured as a dynamic DHCP client. Each port should be set with a different name. This option allows the network DNS servers to be updated when the DHCP server changes its IP address, keeping its name up to date. This is called FQDN and is not always supported by the DHCP server (in this case a warning is logged.) MDLC over IP Site Paging A paging mechanism is available in each site (peer) to make MDLC over IP more reliable. (This feature is the same as in Toolbox V9.54 and MOSCAD V9.25.) Paging a site before transmitting MDLC data to it over IP, guarantees that the site is reachable. This is necessary because MDLC over IP does not have a confirmed type of link in which the peer acknowledges received packets (as opposed to other types of MDLC ports). It relies on the radio to have a link layer that will guarantee a 'best effort' delivery, and thus avoids overloading the channel with excessive traffic. A site is paged by sending it a poll request and awaiting a poll reply. During this time, the RTU can continue to transmit to other sites (and receive transmission from other sites). If the site responds with a poll reply, or any other MDLC data, it is considered as reachable and all pending transmissions are sent to it immediately. Further transmissions will be sent to it as well without paging until the site is declared as failed. If an 'ICMP Destination Unreachable' message is received or if the site does not respond to paging for a configurable poll interval, it will be polled again for a maximum number of polls. If there is still no response, the site is considered to be failed, and the network layer is notified so any pending transmissions can be redirected to an alternative route. If subsequent transmissions are to be sent to the site through an MDLC over IP port, paging will be performed again before actual transmission takes place. The Site Paging mechanism can be enabled or disabled. 106