DTJ Number 3 September 1987 - Digital Technical Journals

New ProductsData is collected from the netwoPk by the networkmanagement interface (NMI) , which pollsthe systems in the network periodically for data.As defined in the DNA architectural specification,which is the formal basis for the DECoctsoftware, each system in the network stores managementinformation and accommodates remoteaccess to it. u The protocol for accessing thisdata is called NICE, which NMI uses to request ·status, characteristic, and counter information.The components for which these types of informationcan be collected include the system, thelines, the circuits, and any other remote node inthe network.Counters have a limited range . When theyreach their maximum values, they latch, and anysubsequent events will not be counted. Therefore, if NMI detects any counters that havealready or may soon latch, it can zero theirvalues.The kernel can poll multiple systems simultaneously.The list of systems to poll and the frequencyof polling for each kind of informationfor each component (twe lve kinds in all, fourcomponents times three types) are all controlledby the network manager. This control data isstored in the on-line database.The data collected by NMI is passed to KIM,which determines if the data is news. If so, KIMwrites the news to LOB and notifies any user whohas requested to be notified when that particularnews arrives. Among the other facts that could bediscovered from the data collected is that newsystems, lines, or circuits have been added to thenetwork. When discovercd,l they arc added to theon-line database.· If allowed to, the database would grow withoutbounds with continuohs polling. The databaseadministration (DBA) software prevents thisproblem by periodically pUrging old data fromIthe database .'One unique attribute of the data collectedfrom the DECnet network is its extensibility.Each new implementatiop or upgrade of theDECnet software can define new fields in theIrecords returned from the polling operation.That is accomplished by a data format (calledNICE data blocks) , which is self describing andextensible. The kernel preserves this structureand also enhances it so thaf all data passed fromone major fu nction to another is carried in thisform.The log file writer (LFW) produces the historyfiles that are read to produce reports. At fixedperiods, LFW writes to a set of files the data collectedsince the last histort fi le was written.The NMCC protocol serVer (NPS) is responsiblefor the kernel's end of the protocol link bywhich the UI program communicates with KIM.In effect, NPS, the NMC protocol, and theNMCC protocol client (called NPC in the userIinterface) allow remote access to the data maintainedby KIM. Multiple protocol links can besupported by the kernel , thus allowing multipleusers to access the data.The need for the asynchronous operation of allIthese fu nctions posed a major design problem forthe NMCC development team. Without our goingITASK TASK TASK TASKTASK TASK ... TASK.. ,., ", ---''", 1", _,"', /.I ... .. .. ... ... / ---,... - .. _• ' ... _ _ -"