The support of a single signalling protocol for all components on the data path of a QoS-based transmission cannot necessarily be assumed In this paper, we investigate the issues surrounding hierarchically layered network QoS signalling configurations, as e.g. can be found in RSVP over ATM signalling. After introducing and discussing these issues we conclude that many of the decisions involved require understanding the performance characteristics of such layered signalling configurations. We therefore describe the implementation of an RSVP/ATM edge device, which we then use to conduct measurements in a configuration that involves in effect three layered signalling protocols: RSVP and ATM's UNI and PNNI. Using these measurements we review the issues in layering signalling protocols and reinforce design decisions being taken for the edge device mediating between the different mechanisms of the two network QoS architectures.
