Methods and systems, including computer program products, implementing techniques for receiving, at a first device of a switched fabric network, requests from one or more applications, each request being destined for a second device of the network, the first device being connected to the second device by a virtual channel; generating, for each request, a descriptor comprising a traffic class designation; and adding the descriptor to an ordered list of descriptors, the descriptor having a location in the ordered list that is based on the traffic class designation of the descriptor.