A set of co-ordinated measures to reach one goal
Quality of Service is not an additional feature which can easily be attached to a network structure as an add-on. Moreover, it is the result of a multitude of activities co-ordinated with one another, which have to be supported by the fundamental architecture of the network.
In order to meet requirements with respect to QoS, the interoperation of the different network platforms must be the primary consideration. In principle, Quality of Service of one network layer is limited by the QoS of the lower layers, i.e. the QoS of the optical platform (layer 2) decides also about the QoS of the IP platform (layer 3). However, it is always helpful to consider if a platform supports mechanisms which enhance the tolerance of (possibly unavoidable) deficiencies of lower layer platforms.
The measures taken for the enhancement of QoS are related to the seven design principles applied to the architecture of the research and education network. These design principles fundamentally contribute to its QoS: redundancy, homogenous link-layer connectivity, control over the network, rightsizing, fault tolerance, process organization and monitoring.