Issue
NPRs - Solution information for IT professionals.
Environment
I/NET site with a network
Cause
Is there information for the site IT Professional concerning NPRs
Resolution
The I/NET control network, on which the NPR is a component, makes exclusive use of UDP/IP packets. All retry, the control network applications layer handles timeout, and other packet transfer reliability. The maximum packet data component size is 140 bytes. The maximum UDP/IP packet size, including MAC and IP headers, is 186 bytes.
Most control network transactions occur in the following four sets of packets: Transmission packet, Acknowledge packet, Response packet, and Response-Acknowledge packet. This is true for all transaction types including manual operator control actions initiated from I/NET, controller software downloads, and trend data uploads. Three control network packet transaction types occur periodically and are formed as a set of two packets. These transactions are for node to node (on the control network) supervision, global data point distribution, and message (alarms, transactions) distribution. This two-packet set is constructed of a Transmission packet and a Response packet. Node-to-node supervision occurs every 15 seconds.
Global data point and message distribution occur at random intervals depending on the operator settings for those events on the control network. Acknowledge and Response-Acknowledge packets are 64 bytes in length. Transmission and Response packets will vary in length from 64 bytes to 186 bytes. The data content of the UDP packets is proprietary to TAC control networks. Critical configuration packet transactions between TAC control network machines use private key encryption to protect the data content. All other packet data contents are not encrypted.
The highest Ethernet network utilization will occur during an I/NET host PC to NPR software restore action. This is the only sustained network activity where transmission packet sizes are filled to the maximum of 186 bytes. It is also the only control network activity that will generate a continuous transmission data stream. Network utilization during activity will be between 2 and 3 percent. To validate this statement, the Triticom Landecoder32 Ethernet monitor was used to observe network activity during the software restore process.
Broadcast UDP/IP packets are NOT utilized by the control network applications. The only Ethernet broadcasts that will be used are standard ARP broadcasts for normal MAC to IP address resolution.
The NPR requires a static IP address assignment.
The control network makes use of logical port number 50069 as the transmission packet destination.
The NPR exposes an SNMP agent that will provide SNMP managers access to the standard MIB2 network variable set.
The NPR exposes a limited Telnet service that provides connecting clients access to control network specific debug information such as the application layer routing table a well as the IP stack routing table and ARP cache.
The NPR operates at 10 Mbs and communicates at half duplex.
