 horizontally. 4.14.2 Packet Core Optimisation - Main Aspects After being presented with different options and approaches, now is the moment to start defining the main issues in packet core optimisation. Network Equipment-Dependent Aspects The different network gear vendors provide different solutions for the packet core network nodes and their interfaces. Therefore, there is great optimisation potential in extracting the most out of the nominal capacity of the network nodes. This requires a thorough knowledge of the equipment. It is not enough just to know the nominal or static capacities of the network nodes, as stated in the technical sheets of the vendors, used mostly during the sales process. It is essential to understand the actual behaviour of the network nodes in the life network, with the existing traffic profiles. This understanding should be built on a knowledge of the network performance and dynamic traffic profile, which is characterised through a series of measurements, mostly obtained through the operations support system (or network management system), which will provide the basis on which to calculate a given set of KPIs (key performance indicators). These effectively characterise the current situation of the network, and eventually will help to identify optimisation possibilities. The concept of the KPI will be dealt with in more detail in the following sections. Thoroughly understanding the actual dynamic situation of the network will provide the tools to evaluate different scenarios for improvement of the network. A possible scenario will now be presented to illustrate this concept better. In a mobile network of a middle sized country in Western Europe, a given SGSN can be observed under heavy traffic volumes offered by a few corporate users located under three RNCs serving the business centre in a major capital. At the same time, another co-sited SGSN is connected to five RNCs serving the suburban area of the same capital, where most of the traffic is offered by commuters mainly using messagi