A mobile node needs to know when it has moved to start using the MobileIP functions. At the MobileIP level, a node moves when its IP address changes.1 To find when it has moved, a node compares its saved home address with a new acquired address. When the addresses are equal, it is at home, otherwise it is visiting another network. A mobile node visiting a network acquires an IPv6 address by autoconfiguration or DHCPv6.
Correspondent nodes (CN) know the mobile node by its home address. By default, the correspondent node sends datagrams to the home address, as shown in Figure 11.11.
The home agent, which proxies the mobile node while it is away, intercepts the packets addressed to the mobile node home address, encapsulates them in an IPv6 packet with the mobile node care-of-address as the destination address and sends them the mobile node at the visiting site. The home agent proxies the mobile node home address by sending a neighbor advertisement message (see Section 6.2) on behalf of the mobile node, advertising the mobile node home address. All neighbor solicitations sent to the home address by any node on the link are answered by the home agent.
After acquiring its new IP address and discovering it is visiting, the mobile node registers its ...