Henning Westerholt is one of the core developers of the Kamailio (OpenSER) Open Source project. He is responsible at 1&1 Internet AG for the operation of their Kamailio (OpenSER) backend, including the maintenance and deploying of extensions of the Voice over IP, Radius and ACS system of 1&1. Henning is in charge with one of the biggest VoIP deployments out there, using Kamailio (OpenSER) as core routing system: over 3 000 000 users, over 7 000 000 phone numbers and 1 500 000 000 routed minutes per month.

Henning is a long term Linux user and contributer to many Open Source projects, participating to world wide events, presenting about Kamailio (OpenSER) and open source. He holds a master degree in applied computer science from the University of Siegen.