Different Data Paths

Abstract

QoS procedures consist of data and control path mechanisms as described in Chapter 2. The next chapter treats different control paths while in this chapter, we focus on the problem of different data path mechanisms in heterogeneous QoS systems. As in the preceding chapter on different QoS declarations, this is clearly an instance of technical heterogeneity. Different QoS architectures usually differ very much in the details of their respective data path mechanisms. For the peer model a close interoperation of the data path mechanisms is necessary and thus these differences are one of its major impediments. However, if we restrict our considerations to the overlay model of interaction between QoS systems, many of the discrepancies on the data paths can be abstracted from since the overlaid QoS architecture does not need to deal with how the underlying QoS architecture ensures the contracted QoS guarantees on the data path but only that these guarantees are ensured. Hence, the problem of different data paths becomes the problem of converting the QoS context of the overlaid QoS system into the QoS context of the underlying QoS system. By QoS context, we mean the criteria which qualify data packets for differential treatment on the data path. QoS context is established by some form of “label” that is either attached to or contained in the data.