Understanding Backends and Packages
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Understanding Backends and Packages

NFR captures network packets and passes them to the NFR engine for evaluation. The engine decides where to direct the packets based upon the selection criteria previously established in the filter. The data is then sent to the appropriate "backend".

Backends

A backend is not one specific object, but rather consists of several components:

  • A filter, written in N code, that is loaded by NFRD and that will run the recorder. The filter examines incoming packets and decides if any of the data should be recorded. If so, it sends that data to the "recorder". The data is sent as a record with a fixed set of fields which is similar to a row of a database table.
  • The "recorder" writes the records into files. Special processing may occur depending on the type of backend you are using. The data is then stored in the files.
  • The user interface can display the recorded data by making "queries" to the backend. A query describes a subset of the data to be displayed. The display output will depend upon the type of backend that is being queried.

NFR provides are two types of backends: List and Histogram. A List backend collects details about individual events; a Histogram backend collects statistical data.

Some backends can send alerts on various conditions.

Packages

A package is a collection of backends. Each backend has N code of its own, but there is also a piece of N code that is shared by all the backends in a package.

There are two good reasons to group backends into packages:

  • The backends may all be recording data you consider to be related. It could be convenient to group them.
  • If several backends process the same data, you can combine them into a package for efficiency. For example, you could call the same program to run once in a package rather than running multiple copies for each backend.

NFR includes several packages that allow you to monitor mail, network, and Web traffic.


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