A Provisioning Services (PVS) server must perform the functions of 'Login' and 'Streaming' in all implementations. The 'Login' function is crucial because the server must authenticate and manage access for clients connecting to it. 'Streaming' is also essential since PVS servers stream the virtual disk images to the clients. Functions like DHCP and TFTP are commonly part of the implementation, but they aren't strictly necessary to be performed by the PVS server itself in all scenarios. PXE, while useful for network booting, is not a function that must be performed by the server in all cases.