using its permanent home address as the source address for the IP packets. This is known as triangular routing or "route optimization" (RO) mode. If needed, the foreign agent could employ reverse tunneling by tunneling the mobile node's packets to the home agent, which in turn forwards them to the communicating node. This is needed in networks whose gateway routers check that the source IP address of the mobile host belongs to their subnet or discard the packet otherwise. In Mobile IPv6 (MIPv6), "reverse tunneling" is the default behaviour, with RO being an optional behaviour. Development Enhancements to the Mobile IP technique, such as Mobile IPv6 and Hierarchical Mobile IPv6 (HMIPv6) defined in RFC 5380, are being developed to improve mobile communications in certain circumstances by making the processes more secure and more efficient. Fast Handovers for Mobile IPv6 is described in IETF RFC 5568. Researchers create support for mobile networking without requiring any pre-deployed infrastructure as it currently is required by MIP. One such example is Interactive Protocol for Mobile Networking (IPMN) which promises supporting mobility on a regular IP network just from the network edges by intelligent signalling between IP at end-points and application layer module with improved quality of service. Researchers are also working to create support for mobile networking between entire subnets with support from Mobile IPv6. One such example is Network Mobility (NEMO) Network Mobility Basic Support Protocol by the IETF Network Mobility Working Group which supports mobility for entire Mobile Networks that move and to attach to different points in the Internet. The protocol is an extension of Mobile IPv6 and allows session continuity for every node in the Mobile Network as the network moves. Changes in IPv6 for Mobile IPv6 A set of mobility options to include in mobility messages A new Home Address option for the Destination Options header A new Type 2 Routing header New Internet Control Message Protocol for IPv6 (ICMPv6) messages to discover the set of home agents and to obtain the prefix of the home link Changes to router discovery messages and options and additional Neighbor Discovery options Foreign Agents are no longer needed Definition of terms Home network The home network of a mobile device is the network within which the device receives its identifying IP address (home address). Home address The home address of a mobile device is the IP address assigned to the device within