Most wireless devices (also referred to herein as “user equipments”, or “UEs”) support multiple access technologies. For example, smartphones typically support cellular, e.g., 3rd Generation Partnership Project (3GPP), 3rd Generation (3G), and 4th Generation (4G), etc. as well as other technologies such as Wi-Fi (IEEE 802.11), Bluetooth, etc. Other device types, such as Internet of Things (IoT) devices, may support cellular (e.g., NB-IoT) and/or other technologies such as Wi-Fi, Bluetooth, etc. Consequently, the device may be operative to select which wireless access technology (or technologies) to attach to from the multiple wireless technologies and/or wireless network providers available at a specific location and time.
3GPP LTE provides an optional standard for access network discovery and selection function (ANDSF) which is expected to be included in the policy control function (PCF) in the standards for 5G. The network features of this standard include a defined control plane functional element called an ANDSF server which is accessible over the Gi interface. The defined reference point in the 3GPP standard is S14. A defined ANDSF client function is used by a device to access the ANDSF server. This client function may be either provided natively as an integrated component of the device's operating system (OS) and/or as a software client which is on the device by a service provider, employer's IT department, or by the user. Enforcement of ANDSF-based policies may take into account external data associated with the device's operating environment, such as, for example: location, network identifiers (e.g., SSID, etc.), connectivity conditions, time of day, applications, etc.