in AppExpert, NetScaler, Traffic Management

Core-Logic Whitepaper


Core-Logic does not specifically target the implementation of a single application on a Citrix NetScaler. However, it is considered as an integrated strategy to get consistency between different applications implemented on a NetScaler platform.

The focal point of the Core-Logic is to centralize all application steering across multiple HTTP/HTTPS Content Switching Virtual Servers by using a single String Map, which we call the Control Plane.

Much of this was inspired by (thank you Neha).

In short, the Core-Logic is a collection of Advanced Policy Expressions and non-addressable Load Balancing Virtual Servers. The policy expressions are static and therefore version able within a configuration’s lifecycle, so new features should/can be implemented in a controlled manner.


Currently, the Core-Logic takes care of the following things on a HTTP and/or HTTPS Content Switch:

  • Select the correct (non-addressable) Load Balancing Virtual Server, based on:
    • FQDN
    • FQDN + 1st path of the URL
    • FQDN domain (wildcard)
  • Redirect the request:
    • From HTTP to HTTPS or vice versa
    • 301/302 Redirect based on:
      • FQDN
      • FQDN + 1st path of the URL
      • FQDN domain (wildcard)
  • Drop or Reset the request, based on:
    • FQDN
    • FQDN + 1st path of the URL
    • FQDN domain (wildcard)

In most cases, reducing the number of content switching policies bound to a Content Switching Virtual Server also reduces the “time-to-decision” on how to process a request.

With the Core-Logic implemented, adding a new application should only require the creation of a non-addressable load balancing virtual server for the application and adding a corresponding entry to the Control Plane.

The advantages are clear:

  • Changes have a lower impact on the current configuration.
  • Changes are easier to automate.
  • Changes take less time to be implemented.
  • Lower time-to-decision
  • Improved performance


The main goal of the whitepaper is to get you involved into improving the framework. Some challenges we try to address:

  • The code should be version able / reusable in multiple situations
  • The code should be independent of the application that needs publishing
  • The code should be identical through a DTAP implementation
  • It should simplify multi tenant implementations / automating in-housing
  • It should be fast in large implementations

Get the files

You can download the whitepaper here.

To get the files containing the code: mail us, we will provide the files for free plus a more in depth whitepaper on the actual code.

Have fun!


What do you think?


  1. Hi Team,
    This is nice whitepaper. However being a newbie in net scalar we are facing issues with writing the codes. Specially we are migrating from F5 to Net scalar and F5 has the policies written in codes which are using TCL and TACL code which are called irule in F5 language.

    Now how to convert from the F5 to netscalar policies any help on that please?

    • Hi avishek,
      I am not aware of any tool that converts irule into NetScaler Code. The corelogic is intended as a framework that should help to setup a structured loadbalancing environment. It can help you get on your way. For the last part it is evaluating the F5 implementation and translating it to a NetScaler strategy application by application.