Data Collection and Reporting Modules


As noted in Chapter 2, the basis of network management is information about the configuration of the network. Much of the important information has to do with the way the network is currently operating, and cannot be gathered during the startup node discovery process. Most of this dynamic information has to do with the volume of traffic and rate and type of errors detected. The Network Management Application, during the entire time it is operational, will actively collect information about traffic and errors, maintain simple summary statistics, and do more involved statistical computations. The information so gathered will be reported on demand or periodically at specific intervals. The data collection and reporting function actually entails as many as three activities: collect data, do computations, generate reports for presentation to some peripheral device. Raw data collection will always take place in active mode. Collection of data as inputs to a computation function may take place in active or surrogate mode. Presentation of reports may be in active or surrogate mode.
4.1 Simple Data Collection

This function will be very similar to that of SNMP Managers and Agents, as currently defined. The same types of statistics will be collected and retained for reporting. To the greatest extent possible the Network Management Application will avoid replicating the functionality provided by SNMP software and will take advantage of it, as previously specified. When necessary, the application will replicate the function of SNMP.

For most purposes, the precise information being collected will be specified via configuration file during the startup process. The privileged user will be able to manually revise the nature of simple information collection at any time. If and when it is deemed appropriate, the development team will add to the kind of simple information to be gathered. This will entail extending the SNMP MIB data structures.
4.2 STATS Subsystem

Beyond the relatively 'raw' data collection capability specified for SNMP, the Network Management Application will regularly perform statistical computations. The specific computations to be performed by any process component will vary, depending on the functional charter of that component. In some cases a process component will perform all relevant (requested) computations using data collected in its sphere of control. In other cases a process component may perform some computations, but forward some collected or computed information to another component for additional computations to be performed.

4.2.1 Simple Statistics

It shall be possible to request simple statistical summaries for nodes, linkes, and/or ports of a node. Simple statistics include periodic utilization, throughput, and error rate computations. Counts or values per unit time and averages per set of unit times shall be computed. Time units may be in seconds, minutes, hours, or days. The measurement period may be some number of any higher granularity time unit, including some number of days, weeks, or months. Peak time unit during the measurementperiod will also be identified and the associated quantity reported. When Simple statistics collection is initiated a start time and optional stop time will be specified. When one measurement period has passed a report is generated, counters are reset to 0 and the process begins again, until the stop time has passed. If a stop time is not specified, computations continue until the process is explicitly terminated by the privileged user. The focus of these statistics shall be on MAC level packets, at a min

4.2.2 Link Cost Computation

Two process components may cooperate in establishing link cost computations, if requested to do so. This involves the two processes synchronizing their time clocks, and periodically measuring delay for transmissions between the two. The rate of measure can be varied, and the length of time over which measurements will be taken to determine a representative delay value, can be specified in a manner similar to the periodicity and length of measurement period specifications for simple statistics, as specified in Section 4.2.1. The 'cost' of a link may be specified to be a function of delay and / or transmission rate and / or error rate. Some preset cost formulae will be provided for selection. Alternatively, the application may execute a user-provided computation algorithm. The cost computation may be different for each process-to-process pair. This computation is provided primarily as a service to Route Control Agents. In future implementations a protocol, or modifications to some existing protocol, will be specified to permit Route Control Agents to interact directly with the Network Management Application to request and receive link cost computation updates. When this protocol is implemented authorization to honor such requests will still be under control of the privileged user. Manual authorization might be required in some circumstances, or the user may be able to pre-authorize this service. In early implementations the request for link cost evaluation will be made by the privileged user, and the results will be reported to the user. The user may then use the information to update tables used by the relevant Route Control Agents using currently available methods.

4.2.3 Trend Analysis

The simple statistics computation capability describe in Section 4.2.1 represents a substantial improvement over the simpler data collection capabilities of SNMP Managers and Agents. However, for effective network planning and management, it is critical to be able to do long term trend analysis so that the need for costly or complex network upgrades can be predicted well in advance of the time users will begin to suffer without such upgrades.

The fundamental inputs to trend analysis are simply the data values computed for nodes, links, and ports, as described in Section 4.2.1. One important difference is that, as described, the privileged user may activate and deactivate, or change the nature of, simple statistics computations at will. To properly provide input for trend analysis the data computed via the methods specified in Section 4.2.1 must be collected in a consistent manner over the period of time analyzed. Thus, if trend analysis is specified for a given statistic for a specific port or node, the appropriate computation functions should be automatically set up, and the privileged user's ability to cancel or deactivate those computations should be limited. At the very least, should the user attempt to deactivate or modify the base computations, a warning message should remind the user that doing so may compromise the validity of the previously requested trend analysis. After displaying the warning message the user should be given the option to cancel the deactivate or modify request.

It shall be possible to do trend analysis on utilization or throughput of a link, error rate at a port, or availability of a node or port. At a minimum, a trend analysis will result in a periodic report of the nature of the statistic whose trend is being monitored. The periodicity of the report may be specified by the privileged user. In addition, it shall be possible for the user to specify thresholds that will cause alarms. Such alarms might fire, for instance, if utilization reaches a certain level or the rate of utilization increase changes dramatically. A marked increase in error rate or decrease in availability might also cause alarm. 4.3 Reports
For any data collection, statistical computation, or trend analysis requested, a report will be generated at a specified rate or at specific times. The user may direct that such reports be made to a specific location. Usually such reports will only be made to physically secure locations, but it shall be possible to override this restriction. In general, a report will be delivered to a location other than where the relevant data is being collected or computed. (As, in general, computations may be done at a location other than where the relevant data is collected.) When a report is generated but not presented to a local peripheral device, the process component producing the report is said to be reporting the results in surrogate mode. It will format the report appropriately and forward it toward the active reporting device.
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CSC405, Spring '96 Distributed Network Manager (DNM) Data Collection and Reporting