the multicast address. Neighbor Discovery The functionality that IPv6 nodes on the same link use to discover each other's presence, when applicable to determine each other's link-layer addresses, to find routers, and to maintain reachability information about the paths to active neighbors. Network Address Translation (NAT) Process whereby one network address is changed to another. The most common use of NAT has been to translate private IPv4 addresses into public IPv4 addresses. The translation is also referred as NAPT, if transport proto- col port translation is taking place. However, due to port translation being very common in IPv4, the term NAT usually also indicates port translation. With the emergence of IPv6 translation discussions and protocol translation, the term NAT44 is sometimes used to highlight that it is IPv4 address translation that is taking place, and similarly term NAT66 to indicate IPv6 address translation. Network layer Layer three in the OSI model. Responsible for transporting data over series of link layers, including routing, error detection, possibly fragmentation and reassembly, and providing logical addresses to the network (such as IP addresses). IPv4 and IPv6 are examples of network layer protocols. NodeB 3G radio network element that directly communicates with the UE over the air interface. Offloading Process for directing the host's traffic to go through some other network than the one over which the traffic would have otherwise been sent. Packet Data Convergence Protocol (PDCP) Responsible for transferring the IP packets over the 3G and LTE radio interface, and also providing header compression. The segmentation and reassembly of the user packets, and mapping the PDP Contexts to the radio bearers is provided by the underlying RLC. In 3G, the functionality, which was in SNDCP in 2G, has been distributed into PDCP and to the RLC protocol layers. In 4G the PDCP is further extended to provide user traffic ciphering and integrity protection, and to deliver packets in sequence and witho