The inclusion of multiple metrics in a routing computation is called policy-based routing. Previous work on solutions to this problem have focused on virtual-circuit-based solutions, and have resulted in computationally expensive algorithms. This paper presents a number of advances in the provision of policy-based routing services in networks and internetworks. An integrated policy-based routing architecture is formulated where the general problem is decomposed into a traffic engineering problem of computing routes in the context of administrative traffic constraints, and a quality-of-service (QoS) problem of computing routes in the context of performance-related path constraints. A family of routing algorithms are presented for computing routes in the context of these constraints which achieve new levels of computational efficiency. Lastly, a forwarding architecture is presented that efficiently supports hop-by-hop forwarding in the context of multiple paths to each destination, which is required for policy-based routing.