We explore Domain federation using SDN as a means of provisioning in real-time, end-to-end QoS. This can be achieved by having a holistic SDN control plane that takes care of dynamically provisioning application QoS needs per domain, and a federation of the domain controllers so as to enable secure and manageable grounds for deploying an RSVP-like service-request protocol between domains. Such a federation should be straightforward to create and be able to preserve the privacy of each domain. In this paper, we design, implement and evaluate an End-to-end MPLS-as-a-Service (EMPLaaS) framework. EMPLaaS is an evolution of MPLS in which SDN is used to provide a dynamic control plane so as to have an application-centric QoS framework. The end result is a scalable and privacy-aware multi-domain control plane for dynamically setting up resource reserved label-switched tunnels. The framework proposes payloading the MPLS service requests onto the widely deployed BGP so as to ensure inter-operability. It also derives responsive end-to-end network behavior by enabling application-delegated traffic engineering. Through an implementation, the proposed framework has been evaluated in terms of ability to setup QoS-aware paths dynamically and adaptively.