1. A method of providing point to point data communications among compute nodes in a global combining network of a parallel computer, each compute node connected to each adjacent compute node in the global combining network through a network link, the method comprising: determining, from among a plurality of class route identifiers for each of the compute nodes along a communications path from an origin compute node to a target compute node in the network, a single class route identifier that is available for each of the compute nodes along the communications path, the class route identifier specifying the route between multiple nodes; configuring network hardware of each compute node along the communications path with routing instructions in dependence upon the available class route identifier and a network topology for the network, the routing instructions for each compute node associating the available class route identifier with the network links between that compute node and each compute node adjacent to that compute node along the communications path; transmitting, by the origin compute node along the communications path, a network packet to the target compute node, including encoding the available class route identifier in the network packet; and routing, by the network hardware of each compute node along the communications path, the network packet to the target compute node in dependence upon the routing instructions for the network hardware of each compute node and the available class route identifier encoded in the network packet.