An example of a system may include a processing resource and a computing device comprising instructions executable by the processing resource to determine an interval based on an amount of time to upgrade a network; determine a series of time windows based on the interval; analyze data traffic in the network over the series of time windows; identify a subset of the series of time windows that are sequential and non-overlapping; and select a particular time window from the subset of the series of time windows to perform an upgrade of the network based on the analyzed data traffic.