  The Northbound (NB) APIs that SDN controllers provide differ in terms of
architecture, syntax, naming convention, data resources, and usage. Using NB
APIs to write SDN applications makes each application dependent on the API of a
specific controller. To bring NB APIs from different vendors under one umbrella
and make programming of SDN applications independent of specific controllers,
we propose a unified software defined development framework that we call
Umbrella. This paper presents the key components of the software and reports
some preliminary results.
