A route computation algorithm, a load-balancing scheme inside a router for making a hop-by-hop routing network (such as the Internet) nonblocking are described in this patent. The output of the route computation algorithm includes a set of link weights that determine the paths of the hop-by-hop routing network. The route computation algorithm and the load-balancing scheme also determine the ingress and egress traffic constraints at each edge router such that as long as the traffic entering and leaving the network does not exceed the constraints, none of the internal links will ever have traversing traffic more than its link capacity. The network is thus non-blocking internally. This greatly simplifies flow admission control and allows hard QoS to be supported inside the network.