1. At a computer system including one or more processors and system memory, a method for routing a namespace lookup request to a namespace manager responsible for a namespace branch corresponding to the namespace lookup request, the method comprising: an act of a particular namespace manager receiving a namespace lookup request requesting access to a resource at a provider within a namespace tree, the namespace tree defining an arrangement of available resources via a plurality of namespace branches, each namespace branch being associated with at least one corresponding namespace manager, the namespace lookup request including a namespace identifier that identifies the requested resource within one of the plurality of namespace branches, the namespace identifier comprising a scheme portion that identifies a scheme type of the namespace identifier and a path portion identifying a path to the requested resource within the namespace tree, and the particular namespace manager being included in a neighborhood of namespace managers that have formed federating relationships with one another to exchange namespace information, each namespace manager in the neighborhood being assigned a unique numeric identifier that is within a predefined numeric range of the particular namespace manager; an act of the particular namespace manager generating an at least one-way equivalent numeric identification value for the resource based on the namespace identifier of the namespace lookup request, including generating the at least one-way equivalent numeric identification value based on a combination of at least the scheme portion of the namespace identifier and at least one part of the path portion of the namespace identifier; and an act of the particular namespace manager sending the namespace lookup request to a destination namespace manager, which is included in the neighborhood of namespace managers that are within the predefined numeric range, and which has a unique identifier numerically closest to the at least one-way equivalent numeric identification value generated for the resource.