cause large increases in the cost of networking devices. An open source software implementation is provided by ODTONE. Crossing different administrative connectivity domains will require agreements among different network operators. Currently, such agreements are still not in place. In smart phones today, a user can manually select to use WiFi or cellular LTE, but the connections are not automatically maintained should a disconnection of one network occurs. Hence, seamless handovers across different wire/wireless networks are still not available today. Examples A user should be able to unplug from an 802.3 network and get handed off to an 802.11 network. A cellular phone user in the midst of a call should be able to enter an 802.11 network hotspot and be seamlessly handed off from a GSM network to the 802.11 network and back again when leaving the hotspot. Other similar technologies Unlicensed Mobile Access (UMA) technology is basically a mobile-centric version of 802.21. UMA is said to provide roaming and handover between GSM, UMTS, Bluetooth and 802.11 networks. Since June 19, 2005, UMA is a part of the ETSI 3GPP standardization process under the GAN (Generic Access Network) Group. The Evolved Packet Core (EPC) architecture for Next Generation Mobile Networks (3GPP Rel.8 and newer) provides the Access Network Discovery and Selection Function element (ANDSF) (see 3GPP TS 23.402 and 3GPP TS 24.312). Its S14 interface provides the communication path between the Core Network and the User Endpoint device on which to exchange discovery information and inter-system mobility policies, enabling as such a network suggested reselection of access networks. See also Mobility management Mobile IP Handover Radio resource management Roaming Vertical handoff Handoffs in Wireless ATM / Mobile ATM Asynchronous Transfer Mode#Wireless ATM or mobile ATM References External links IEEE Standards Associations IEEE 802.21 web site Is Cellular Handoff Nigh? article Internet Protocol Journal Introduction to IEEE 802.21 Open source implementation ODTONE IEEE 802