1. A method, in data processing system, for differentiating between different traffic types comprising: generating a first mapping data structure that, for each single-root virtual hierarchy in the data processing system, associates each traffic class in a plurality of traffic classes with a corresponding virtual channel in a plurality of virtual channels; generating a second mapping data structure that maps each virtual channel in the plurality of virtual channels to a corresponding virtual link in a plurality of virtual links of the data processing system; and routing traffic of a particular priority group from a single-root virtual hierarchy to a particular virtual link in the plurality of the virtual links based on the first mapping data structure and second mapping data structure, wherein each combination of virtual hierarchy and virtual channel is mapped to a different virtual link in the plurality of virtual links.