he target is to detect any kind of abnormal situation having a negative impact on the network performance. The inheritance from radio access is very strong in this aspect, although from the packet core point of view it is difficult to achieve its level of efficiency, mostly due to the fact that the packet core network nodes are essentially more stable and predictable in their dynamic behaviour. There is another variant of monitoring, not necessarily related to OSS monitoring, that enables new possibilities for core network, i.e. real-time monitoring. It is possible to define real-time monitoring at two different levels, network node based real-time monitoring and network interface based real-time Core Network Planning and Optimisation monitoring. This process is essentially complex and might be intrusive for the network infrastructure, which is not a desirable feature. Existing systems are based on network probes, which are difficult to manage, or on network nodes, which are essentially easier to handle. In addition to those, it is interesting from a packet core point of view to note the approach taken by some IP based monitoring tools, which are capable of presenting a monitoring view of different application level performance aspects in real time. Although the real time feature is not essential for the optimisation approach, its instantaneous capabilities provide an additional degree of efficiency in the process. Troubleshooting Troubleshooting is actually a technique that is being utilised in different processes and events throughout the network lifecycle. A great deal of intuition is required for an engineer to be successful during a troubleshooting exercise, although with the flavour of optimisation, the troubleshooting techniques can be marginally better when systematically approached. The tools utilised mostly in this area are tracing tools. The basic tools are usually protocol analysers, especially used in Gb and Iu-PS interfaces, and of course IP protocol analysers in the Gn backbone and Gi interfaces, w