Network slicing is seen as a key enabler for meeting the diverse network service requirements, which stem from the transition to 5G. Furthermore, network slicing provides inherent support for multi-tenancy, enabling network providers to slice their infrastructure and resell it to a large number of tenants. Most existing work on slicing has been focused on certain mechanisms (e.g., slice embedding) and architecture specifications. As such, the performance and scalability with network slice instantiation has not been studied in depth. These aspects are even more critical in the case of slice deployments across multiple Points-of-Presence (PoP), since the various slice components should be stitched together for the end-to-end slice instantiation. In this paper, we present the design and prototype implementation of a network slicing architecture, based on which we perform a feasibility study of network slicing using multiple experimental infrastructures. Our prototype implementation supports all the required functionality for slice instantiation, such as resource discovery, slice embedding, resource provisioning, link setup, and inter-PoP slice segment stitching. Our experimental results corroborate the feasibility of multi-PoP network slicing. We further gain useful insights on slice instantiation performance and scalability.