Core-Logic Whitepaper

Core-Logic

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 https://www.citrix.com/blogs/2011/07/29/how-string-maps-help-simplify-and-reduce-configuration/ (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.

Expressions

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 + 1^st path of the URL
  • FQDN domain (wildcard)
• Redirect the request:
  • From HTTP to HTTPS or vice versa
  • 301/302 Redirect based on:
    • FQDN
    • FQDN + 1^st path of the URL
    • FQDN domain (wildcard)
• Drop or Reset the request, based on:
  • FQDN
  • FQDN + 1^st 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

Goal

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!