Product Documentation

Pattern Sets and Data Sets

Aug 31, 2016

Policy expressions for string matching operations on a large set of string patterns tend to become long and complex. Resources consumed by the evaluation of such complex expressions are significant in terms of processing cycles, memory, and configuration size. You can create simpler, less resource-intensive expressions by using pattern matching.

Depending on the type of patterns that you want to match, you can use one of the following features to implement pattern matching:
  • A pattern set is an array of indexed patterns used for string matching during default syntax policy evaluation. Example of a pattern set: imagetypes {svg, bmp, png, gif, tiff, jpg}.
  • A data set is a specialized form of pattern set. It is an array of patterns of types number (integer), IPv4 address, or IPv6 address.

In many cases, you can use either pattern sets or data sets. However, in cases where you want specific matches for numerical data or IPv4 and IPv6 addresses, you must use data sets.

Note: Pattern sets and data sets can be used only in default syntax policies.

To use pattern sets or data sets, first create the pattern set or data set and bind patterns to it. Then, when you configure a policy for comparing a string in a packet, use an appropriate operator and pass the name of the pattern set or data set as an argument.