can be received from layer 2 indications, such as change from a cellular network to a WLAN network. However, due to developments in network based mobility approaches, Introduction to IPv6 it is not always that straightforward to rely on layer 2 events. Furthermore, sometimes the layer 2 can change without impacting layer 3. IETF has defined a layer 3 based tool for faster detection of changes on a network point of attachment. The solution is called Detecting Network Attachment (DNA) [119]. The DNA procedures are triggered from layer 2 indications about possible change events taking place, such as layer 2 connection being (re)established. The first step that DNA takes is to assume that all network link specific information may have become obsolete and may need to be verified. The verification happens by performing IPv6 Neighbor Discovery procedures, such as sending unicast Neighbor Solicitations for previously learned routers in parallel to multicast Router Solicitation message to quickly learn about new routers. A DHCPv6-using node would need to verify that the information learned via DHCPv6 is valid by reaching the DHCPv6 servers. If the responses to solicitations indicate that the attachment point to a network has not changed, or has changed but without implications to the networking layer, the node can continue using the information it previously had. However, if the point of attachment has changed, fully or partially, the node must flush the information that is no longer valid, such as IPv6 addresses that the node has autoconfigured from routers that are no longer reachable. It is worth noting that host movement may not warrant flushing of all information, but only pieces of information received from routers and DHCPv6 servers that are no longer reachable. The benefit for applications of (fast) detection of network attachment change is that applications will quickly be informed about disconnected transport layer sessions, and hence can immediately attempt reconnection. Obviously, the DNA can be used to speed 