Software that speeds up transmission in a wide area network. Various techniques are used including compression and the application of quality of service (QoS) parameters to packets. If an application is chatty and requires constant acknowledgments, a specialized WAN accelerator may transfer data behind the scenes. For example, Windows file sharing (Common Internet File System (CIFS) protocol) is slow over a WAN. A CIFS WAN accelerator can prefetch data at the server side and transfer it to the client side so that most of the CIFS interaction takes place locally in the client.