Mobile IP with VPN

The second variant to Mobile IP is Mobile IP with VPN. Mobile IP with VPN
affords greater mobility for the subscriber over Simple IP with VPN because
it can maintain a session when it moves from one PDSN area to another.
Like Mobile IP, the IP address assigned to the subscriber is static; however,
the private network that the mobile is connected to provides the IP address,
which needs to be drawn from a predefined IP scheme that is coordinated.
The PDSN provides a COA when operating in a non-home PDSN for routing
purposes. However, the IP packets in both directions flow between the
HA and the FA using IP-in-IP encapsulation, and no treatment, with the
exception of throughput speed allowed, is performed by the wireless network.
Figure 7-17 depicts the general packet flow for Mobile IP with VPN.