e Neighbor Discovery Proxy does not show as an IPv6 router for other nodes. The only instance where the Neighbor Discovery Proxy appears as a node, a router, to others is the case where the Neighbor Discovery Proxy has to emit ICMPv6 Packet Too Big message to inform a sender about an MTU problem on the next link. In the case of proxying Router Advertisement messages, the Neighbor Discovery Proxy has to set a 'P' bit on in the flags field of Router Advertisement. 'P' bit indicates to the receiver that the Router Advertisement is proxied, and cannot be proxied any further. This feature is needed to avoid the formation of network loops. Consequently, if a node that would like to act as a Neighbor Discovery Proxy receives a Router Advertisement with 'P'-bit on, it cannot engage in proxying functions. The great benefit of the Neighbor Discovery Proxy technology is that it significantly decreases the need to implement IPv6 Network Address Translations (NATs), which oth- erwise might be needed to connect different link types, and also in scenarios where there are not enough IPv6 addresses locally available (e.g. if DHCPv6 Prefix Delegation (PD), described in Section 3.5.2, is not available for use). 3.5 Address Configuration and Selection Approaches IPv6 comes with two major automatic address configuration protocols. The one developed first, and that has more widespread support, is 'IPv6 Stateless Address autoconfigura- tion' [73]. The fundamental idea of the SLAAC is to enable hosts to configure addresses without a centrally administrated address allocation scheme, per-host states in the network, and address management network entities. The second tool, stateful address autoconfigu- ration, is 'Dynamic Host Configuration Protocol for IPv6 (DHCPv6)' [54]. The approach of DHCPv6 is familiar to people accustomed to Dynamic Host Configuration Proto- col version 4 (DHCPv4), but there are differences as well - such as DHCPv6 relying on ICMPv6 Router Advertisements to deliver default router information. Originally the IPv6 wa