To achieve such simplicity, thin clients sometimes lag behind desktop PCs in terms of extensibility. For example, if a local software utility or set of device drivers are needed in order to support a locally attached peripheral device (e.g. printer, scanner, biometric security device), the thin client operating system may lack the resources needed to fully integrate the required dependencies (although dependencies can sometimes be added if they can be identified). Modern thin clients address this limitation via port mapping or USB redirection software. However, these methods cannot address all scenarios. Therefore, it is good practice to perform validation tests of locally attached peripherals in advance to ensure compatibility. Further, in large distributed desktop environments, printers are often networked, negating the need for device drivers on every desktop.