f view. With current levels of utilisation of the network nodes in terms of traffic, the most likely scenario is that the mobility management and session management procedures offer the most limiting load to the system, hitting the capacity roof of the network nodes before the traffic volumes reach such levels that priorisation of traffic according to their nature can take place. This fact will have a major impact on the optimisation process. 4.16.3 QoS Process Specifications for 3G define four traffic classes ( conversational, streaming, interactive and background) and also specify in more detail other QoS attributes such as the maximum bit rate, guaranteed bit rate, maximum transfer delay, maximum delay variation and bit error rate. The specifications have actually been gathered in a table where the QoS requirements are defined in detail. This QoS detailed parameter table is the starting point of the QoS network implementation design and is closely related to the concept of service creation. Moreover, during the creation of a new mobile application, the QoS aspects are the major concern from the network point of view, since there is a need for an end-to-end approach for proper QoS deployment that cannot be limited to a given network subsystem. During the network planning phase, the QoS is one of the aspects to be considered, but from a rather general approach, ensuring its deployment and functionality from a network design perspective. Only when new mobile applications are to be introduced does the QoS concept trigger attention, especially with those applications that generate more demanding traffic flows, such as video streaming. The sensible process consists of verifying the capability of the packet core network nodes to deal with the traffic created with the introduction of a new application, which may end in a new dimensioning exercise. Once the verification and eventual re-dimensioning takes place, the packet core network is ready for the end-to- Quality of Service end QoS implementation for the given new 