Heterogeneous network infrastructures have always been part of the public Internet as well as production systems in enterprise and industrial environments. The coexistence of multiple communication technologies and systems from multiple vendors still represents management cost and reliability challenges mainly due to the lack of interoperability at the network management plane. In this paper, we outline the main challenges that organizations face in managing large scale multi-technology and multi-vendor heterogeneous network infrastructures. We then propose the ENM (Extended Network Management) framework, a scalable and extensible service oriented architecture for deploying ontology-driven network management services adapted for large scale heterogeneous infrastructures. The ENM framework defines the different entities involved in deploying ontology-driven network management services and specifies a scalable and flexible communication protocol, based on Diameter (RFC3588), between these entities. To demonstrate the feasibility of the proposed framework, a proof of concept was implemented and deployed on a small scale test-bed.