Reasonable choice of protocol parameters is crucial for the successful deployment of overlay networks fulfilling given service quality requirements in next generation networks. Unfortunately, changing network conditions, as well as changing application and user requirements may invalidate an initial parameter choice during the lifetime of an overlay. To this end, runtime adaptation of protocol parameters seems to be a promising solution-however, it is not clear if protocol parameters can be adjusted dynamically at runtime in a distributed setting. In this paper, we show-using the NICE application layer multicast protocol as an example-that runtime adaptation of protocol parameters is indeed feasible. We propose an algorithm for adapting the NICE clustersize parameter k dynamically at runtime and discuss the impact on service quality. Our simulations show that runtime adaptation of NICE protocol parameters is promising for service improvement and that data latencies can be optimized by up to 25% without increasing the overhead significantly for most of the nodes.