vides routing-related and Quality of Service (QoS)-related information between the BSC and the SGSN. The network ser- vice that the Gb uses is frame relay. Base Transceiver Station (BTS) 2G radio network element that directly communicates with the mobile station over the air interface. Bellhead A hardcore telecommunications engineer who despises anything except circuit switched networking or more recently anything but managed vertical solutions. Control plane Takes care of the signaling in the network used for controlling the network and the mobile station. The control plane transports the messages that are needed to attach a subscriber to the network, authenticate and authorize the user, open and close connections, and for signal handovers. Core network The Internet service provider's network between the radio access network and the transit network. In the case of 4G, the core is referred as the Evolved Packet Core (EPC) and includes MME, SGW, PDN-GW, and HSS. In the case of 2G and 3G, the core is referred as the packet core and includes SGSN, GGSN, and HLR. Domain Name Service (DNS) Global name to address, and address to name translation service. The DNS allows human-readable names to be used for protocols and user Glossary interfaces, while allowing the Internet still to function with numbers with better com- putational characteristics. DNS is a global distributed database covering the whole Internet. Domain Name System Security Extensions (DNSSEC) Extensions that allow signing of the DNS resource records and validation by the DNS resolvers. Protects against spoofing and tampering of the records on the path from authoritative name server to the resolver. Duplicate Address Detection (DAD) The process by which an IPv6 node ensures that an IPv6 address that it is configuring for a network interface is not already in use on the link to which the node is attached. eNodeB LTE base station that directly communicates with the mobile station over the air interface. The eNodeB, however, also includes some of the functio