Some thoughts on emulating jitter for user experience trials

It is usually hard to control the network conditions affecting public online game servers when studying the impact of latency, loss and jitter on user experience. This leads to a natural desire for running user-experience trials under controlled network conditions, and hence a requirement for accurate (or at least predictable) emulation of IP level latency, loss and jitter on a localized network testbed. In this short paper we reflect on some experiences with running user-experience trials, and specifically evaluate the utility and limitations of using FreeBSD's kernel-resident dummynet module to introduce controlled jitter. We expect these insights will stimulate further user-experience trials built around low-cost, unix-based networking tools.