The vertical interplay among Edge-Fog-Cloud computing introduces a new requirement to accommodate services, network functions and chains of them in a heterogeneous environment. However, such operation involves challenging tasks including management of resource availability, compliance with Service Level Agreements (SLAs), dynamic re-configuration of services and networks across different computing domains. This paper proposes Dynamic Network Function (DNF) that involves 1) a tractable VNF placement algorithm, and 2) a bottleneck detection and removal algorithm for the heterogeneous computing and network environments representing the Edge-Fog-Cloud interplay. The proof of concept (PoC) implementation of DNF has been done using Docker-based NFV and SDN setups as well as a simulation setup for studying the DNF scalability. The evaluation results showed that DNF could achieve high acceptance ratio of SLA requests with reasonably short duration. The PoC implementation also exhibited the proper functions to 1) orchestrate the NFV and SDN, and 2) detect and mitigate the bottlenecks. © 2018 Association for Computing Machinery.