In this paper we demonstrate the feasibility of an extended and flexible SDN control plane that allows to overcome the limitations of the Openflow protocol by achieving distributed and intelligent network services in SDN networks. This extended control plane is designed according to the following reference guidelines; 1) the concept of generic and programmable network nodes usually known as "white boxes". They integrate a generic engine to execute the service and a library of elementary components as basic building blocks of any services; 2) a fine grained decomposition logic of network services into elementary components, which allows the services to be designed and customized on the fly using these building blocks available on each network node in libraries; 3) a mechanism for re-configuring or redefinition on the fly of the network services on generic nodes without service interruption; 4) some smart elementary agents called SDN controllers elements to provide and distribute the intelligence necessary to interact with the data plane at different levels of locality. This SDN control plane is illustrated in a proof of concept with the implementation of a distributed monitoring service use case. The monitoring service can act and evolve in a differentiated manner in the network depending on traffic requirements and monitoring usage.