5G marks the beginning of a revolution in the mobile network ecosystem, transitioning to a network of services to satisfy the demands of new telecom players, the vertical industries. This revolution implies a redesign of the overall mobile network architecture to provide it with the automation and programmability capabilities to handle the envisioned heterogeneity, flexibility, and dynamicity. Software Defined Networking (SDN), Network Function Virtualization (NFV), and Network slicing are key enabling concepts to provide such capabilities. They are complementary, but they are still in its infancy and the synergies between them must be exploited to realise the mentioned vision. This thesis contributes to its development and integration in next generation mobile networks by designing an end-to-end (E2E) network service orchestration architecture. This proposed architecture, which is aligned with some guidelines and specifications provided by main standardization bodies, goes beyond current management and orchestration (MANO) platforms to fulfill network service lifetime requirements in heterogeneous multi-technology network infrastructures shared by concurrent instances of diverse network services. Other relevant contribution of this work is the multi-administrative domain capabilities of the proposed architecture, going beyond high-level considerations done in existing literature that prevent its effective realisation. The resulting architecture, workflows, and interfaces are validated and assessed through practical implementations in experimental infrastructures with network service definitions close to real vertical use cases (e.g., automotive and eHealth), which help bridging the gap between network providers and vertical industries stakeholders.