If you bought an original Surface tablet when it was first released in October 2012, you might have noticed that it did not have an Ethernet port. The tablet also didn't support any USB-based Ethernet adapters. There have been rumors that Microsoft was working on adding Ethernet drivers to Windows RT for the 8.1 release, but Microsoft never officially commented on those plans.
Now it appears that the Windows RT 8.1 update has finally added Ethernet driver support. In a page on the Surface support site, it states, "To use the Surface Ethernet Adapter with Surface RT you'll need to update to Windows RT 8.1 and check Windows Update." While this would appear to be a confirmation that Ethernet support has finally come to Windows RT; Neowin has emailed Microsoft for official confirmation.