In this paper, we propose a set of dimensioning rules, which deliver high quality session-based services over an NGN network based IP/MPLS transport infrastructure. In particular, we develop a detailed dimensioning methodology for achieving a target QoS requirement, expressed in terms of per-service traffic flow throughput and delay. The proposed methodology outlines an optimal equipment allocation strategy for a requested capacity. The benefits of operating a network under the paradigm of generous dimensioning, for converged multiservice traffic flows, include target QoS guarantee, scalability, and resilience of the transport network, while maintaining high resource management. We present and discuss experimental results which illustrate a practical implementation of the proposed dimensioning strategy and its benefits.