or a protocol framework. BCPs describe the currently best found ways to implement or deploy something. Additionally, an RFC can be classified as experimental or informa- tional. Experimental RFCs are meant only for experimenting, and informational RFCs range from specifications to jokes. Roaming A mobile station is roaming when it is attached to a 3GPP radio access that is not part of the home network. Attachment to non-3GPP accesses, such as WLAN, is not referred to as roaming. Router discovery A process for hosts to automatically find routers present on the link. The router discovery is essential for global communications, as without manually con- figured or automatically discovered routers, hosts can only send packets to other hosts on the same link. Hosts discover routers by sending Router Solicitations and by listening for Router Advertisements. Routing Technologies that cover rules and decisions made by individual routers to decide where to forward IPv6 packets. It also refers to the protocols that are used by routers to share information about paths to different destinations (to different IPv6 networks). Glossary S1-MME interface Control-plane interface connecting the eNodeB and the MME. The interface uses SCTP as the transport protocol. S1-U interface User-plane interface connecting the eNodeB and SGW. The interface is based on GTP. S4 Serving Gateway Support Node (S4-SGSN) A 3GPP Release-8 (and onwards) com- pliant SGSN that connects 2G/3G radio access networks to the EPC via new Release-8 GTP-based S3/S4 interfaces, and to an HSS using a Diameter-based S6d interface. S5/S8 interface The interfaces connecting the SGW and the PGW. S5 is used within the home network, and S8 is the roaming interface when the UE is roaming. This is similar to the Gn- and Gp-interfaces in GPRS. The S5- and S8-interfaces consist of user and control planes. S6a interface Interface connecting the MME and HSS. The interface is based on Diameter. S6d interface Interface connecting 3GPP Release-8 S4-SGSN and an HSS. The interface i