ct that having a properly tuned network bearer is a prerequisite for having a healthy application performance. This view also supports the sequential approach of first having the bearer optimised, and then the application performance is tuned from an end-to-end perspective, in which the packet core network also plays a major role. This approach can be considered as the vertical approach, because differentiation of the activities is done vertically with respect to the protocol layer model. System Optimisation and Subsystem Based Optimisation There is yet another view to packet core network optimisation that can be justified in view of the actual complexity of the current mobile networks, where new services and applications are meant to be added next to the packet core network through the Gi interface: Subsystem based optimisation, which relies on the fact that the network subsystems (in our case, BSS or RAN and packet switched) are complex enough to be considered separately if all the potential is to be unravelled. In this context, the focus would be on packet core optimisation per se, when there Packet Core Network Optimisation is a clear need to improve performance aspects, configuration aspects or even capacity aspects of the packet core network. There is an understated link to bearer optimisation in this approach. Packet core optimisation as part of the concept of system optimisation, which simply assumes that the subsystem based optimisation is simply not enough to achieve the expected performance. Tuning subsystem parameters will not provide the full potential if those parameters are not aligned with the possible counterparts on the other subsystem. Under this approach, there is also an understated link towards bearer or application optimisation, having the flavour of an end-to-end approach, which has been very much under the spotlight lately. This last approach can be considered as a horizontal approach, due to the fact that it is based on the inclusion or exclusion of network subsystems that are considered