ePolicy – FortiBalancer

Chapter 17 ePolicy

17.1 Overview

ePolicy is a script-based function for extending the capabilities of the FortiBalancer appliance. Using the scripts written in Tools Command Language (TCL), you can customize new features in addition to the existing functions on the FortiBalancer appliance. For example, the FortiBalancer appliance can be customized to support more application protocols, precisely control IP application traffic in both incoming and outgoing directions, or control the access of the specified client to real services.

17.2 ePolicy Elements

The elements of ePolicy are as follows:

  • Event
  • Command
  • Command invocation rule

17.2.1 Event

ePolicy uses an event-driven and message-response mechanism. The FortiBalancer appliance defines an event for every action occurring in each Client-FortiBalancer-Server connection. When such an event occurs, the FortiBalancer appliance will process traffic according to preconfigured ePolicy commands.

17.2.2 Command

ePolicy uses commands to instruct the FortiBalancer appliance to process traffic after an event occurs, such as rewriting packet contents, selecting real servers, selecting groups, or querying whether a group has valid real servers.

17.2.3 Command Invocation Rule

Command invocation rules indicate the relationship between events and commands. Based on the command invocation rules, you can flexibly combine the events and commands to intercept, detect, convert, or redirect the IP application traffic in both incoming and outgoing directions. For detailed information of events, commands, and command invocation rules, contact Fortinet Customer Support for related documents.

17.3 ePolicy Scripts

By functions, the scripts of ePolicy can be classified into the following:

  • Setting script: specifies the traffic type of a virtual service. The following table lists the setting scripts that are currently supported:

Table 17–1 Content of Setting Scripts

Traffic Type Content of the Setting Script
HTTP message::type http
Diameter message::type binary

binary_message::length_start_offset 1 binary_message::length_end_offset 3

Generic TCP message::type binary
  • Runtime script: specifies the action of the FortiBalancer appliance for an event. The content of a runtime script should be written according to the actual requirement based on events, commands, and command invocation rules. For the examples of the runtime scripts, contact Customer Support for related documents.

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