This IDC Forecast Update recasts IDC's long-term forecast (through 2009) in light of 1H05 data and discusses the major dynamics impacting the forecast. Changes to IDC's initial forecast, U.S. Router 2005?2009 Forecast by Vertical Market (IDC #33807, October 2005), include both refined industry segmentation and alterations to the projected forecast trends. An explanation of those changes and the rationale that motivated them is subsequently offered.