 to bad network quality in end user perception. The regular end user does not know or care about the admission control algorithm's calculations and decisions. For the end user the success of the service request is the only meaningful consideration. As far as the admission control algorithm is concerned, the service quality should be good if a service request is accepted, SO the expectancy is that, if accepted, the end user will not have any quality issues that could be improved. This, however, might not always be true if the vendor has chosen an admission control algorithm that tries to optimise the capacity usage of the network by taking some risk in quality. If there is such an algorithm in use, then performance engineering can optimise the calculation of the algorithm only if some input values are made accessible to engineering by the vendor. If the required input parameters are not made available then there is very little an operator or performance engineer can do. They can ask the vendor to make such changes to the software and provide a software change delivery version including those changes or they can change the vendor, which is quite a huge decision, but otherwise there is nothing they can do. On the other hand, if there are admission control algorithms with input parameters that can be made to take adjustments then tweaking them can perform the optimisation. The possible parameters are defining in one way or another the acceptable levels of delays and acceptable levels of losing information packets (i.e. in transmission this means AAL units or ATM cells). The nature of the algorithm and what it is designed for suggests that tweaking them can easily mean that the input parameters go to an unauthorised zone. This becomes taking those parameters to absolute values. It should, however, be remembered that some sacrifices have to be made, probably in the accuracy of the algorithm, in order to keep it fast and trouble-free but on the safe side. Therefore, practically tweaking input parameters to an unauthoris