so include VLAN design optimisation and routing protocol optimisation. Up to recent times the backbones of mobile operators have not been suffering from exces- sive traffic loads that may trigger this type of process. However, the new IP traffic levels generated by the new telecommunications architectures, such as release 4 based soft-switch solutions, will produce a significant increase in the IP traffic levels served by the operator's backbones. Although this type of traffic is not impacting directly on the packet core network elements, the fact of sharing fixed network resources places more stress than earlier on the complete mobile network solution. Procedure-Dependent Aspects This type of optimisation can be described as the search for improvement in the performance of a given type of procedure. Normally, this activity arises as a result of an observed low performance of the procedure under study, noted through some of the OSS counters and KPIs, e.g. a low GPRS attach success rate. If the OSS KPIs do not give any indication, e.g. the GPRS attach average delay, this low performance of the procedure is normally detected through subscriber complaints and it is further characterised through controlled end-to-end performance tests with interface tracing. This is a technique normally associated with troubleshooting practices, and can be very useful for this type of case. Once the source of the problem - it can also be simply an optimisation opportunity - is identified, it can generally be associated with a given network node, network subsystem or network interface. Following the previous example of the GPRS attach procedure, if the OSS data have been recording an exceptionally low GPRS attach success rate and while carrying out an interface tracing exercise an abnormally long delay is detected in the Gb interface between the request and response messages of the procedures, the optimisation activity can focus on tuning the timers that control the BSSGP associated processes in the SGSN. In a different scenario, if t