This post discuss the “Configure slow-link mode” policy on Vista with Offline Files. How is slow link determined by Windows Vista? Offline Files measures the speed of a link based on the packet latency between the client and the target server. This is reported by the network driver and TCP stack and is then used to compute the throughput to the server for comparison with the configured throughput and/or latency policy configuration. You might think that the NLA service (Network Location Awareness) service would be used in this, but that is not the case.