Introducing QoS Awareness in Tcl Programming: QTcl

A number of distributed applications require communication services with Quality of Service (QoS) guarantees. Among the actions undertaken by the Internet Engineering Task Force (IETF) with regard to the end-to-end QoS provisioning issue in the Internet, the definition of the Integrated Services (IntServ) framework plays a major role. According to this model, applications need to interact with network routers by means of a signalling protocol, RSVP. Even though special-purpose APIs have been defined to let applications negotiate QoS parameters across RSVP-capable networks, the integration of QoS negotiation mechanisms in the applications still remains an open issue. In modern programming, the Tcl scripting language plays a significant role, as it enables fast system prototyping by gluing basic components to build complex applications. In this paper we present QTcl, an extension of Tcl-DP which provides programmers with a new set of primitives, fully compliant with the SCRAPI programming interface for RSVP. We also present how QTcl has been used in an advanced VoD application to setup reservations in an IntServ network.