This paper provides two contributions to the study of quality of service (QoS)-enabled middleware that supports the network QoS requirements of distributed real-time and embedded (DRE) systems. First, we describe the design and implementation of NetQoPE, which is a model-driven component middleware framework that shields applications from the details of network QoS mechanisms by (1) specifying per-flow network QoS requirements, (2) performing resource allocation and validation decisions (such as admission control), and (3) enforcing per-flow network QoS at runtime. Second, we evaluate the effort required and flexibility of using NetQoPE to provide network QoS assurance to end-to-end application flows. Our results demonstrate that NetQoPE can provide network-level differentiated performance to each application flow without modifying its programming model or source code, thereby providing greater flexibility in leveraging network-layer mechanisms.