Open Source software OpenStack's very name emphasizes the motivation behind its genesis: OpenStack aims to be an open basis for the cloud that offers users the freedom and independence to run their applications as they need. Put a different way, users can look for the cloud provider whom they think best suits a given situation. The Open Telekom Cloud underscores its open approach with the OpenStack Powered Compute (DefCore) 2017.01 certification.

An open platform lets companies design and develop their own options in-house. However, this can have a negative impact on interoperability, something we frequently see in the world of business. The OpenStack Foundation's response has been to establish a yardstick in the form of its guidelines for using the OpenStack Powered brand (DefCore). Only companies that have passed all of the necessary tests are listed on the official OpenStack Marketplace This gives users a single standard they can apply to their development work and which enables them to freely port their applications within this ecosystem without having to make major changes. It is one way of making good the promise of independence.

The Open Telekom Cloud received its first DefCore certification in 2016. Following new releases from OpenStack (Mitaka, Newton and Ocata) and the foundation's new or updated services, tests also need to be modified to ensure their conformity with OpenStack.

The OpenStack community has produced an extensive test suite (tempest) for this purpose. The "InterOp Guidelines" for certification are a subset of this suit. Obtaining DefCore 2017.01 certification required a company to pass over 200 different tests. In 2016, there were only 85. These tests are performed on an ongoing bases in the Open Telekom Cloud (every night). The tools automatically access the Open Telekom Cloud via  API calls and create different OpenStack resources, e.g. virtual machines, storage volumes etc. The tools then check if these comply with the standards and send feedback to the operator.