The Internet2 project is a partnership of over 130 U.S. universities, 40 corporations, and 30 other organizations. Since its inception, one of the primary technical objectives of Internet2 has been to engineer scalable, interoperable, and administrable interdomain QoS to support an evolving set of new advanced networked applications. Applications like distance learning, remote instrument access and control, advanced scientific visualization, and networked collaboratories will allow universities to fulfill their research and education missions into the future, but only if the network QoS these applications require can be ensured. To meet this challenge, the Internet2 QBone initiative has brought together a dedicated group of U.S. University and federal agency networks, international research networks, engineers, researchers, and applications developers to build a testbed for interdomain IP differentiated services. This article presents the engineering motivations behind DiffServ and its adoption by Internet2, provides an overview of the QBone architecture, and describes its anticipated deployment, including plans for a trial inter-domain bandwidth brokering architecture. Security aspects are considered togethered together with an inter-bandwidth broker reservation signaling protocol.