Different Control Paths

Abstract

After the treatment of different data paths in the last chapter, we now turn to the other component of QoS architectures — the control path. Different control paths in heterogeneous QoS systems are again an instance of technical heterogeneity that has to be mediated by edge devices. In this chapter, we concentrate on short-term mechanisms of the control path, i.e., the signalling protocols of different QoS architectures. These tend to be very peculiar for each QoS architecture, in fact, they often exhibit even more discrepancies than QoS declarations. As a result of this, it is very difficult to find generic solutions to the concatenation of control paths, as we call it. The challenge of concatenation is more on ensuring that all the details of a given pair of signalling protocols are taken into account when they shall intemperate at an edge device. However, what we strive for in this chapter is to establish a conceptual model of layered signalling systems and the general issues involved in them. These are then illustrated by the concrete example of an overlaid QoS system based on RSVP/IntServ onto a system based on ATM. For this instance of a layered signalling configuration, we then also deal with all the details of concatenation.