Mobile IP

Mobile IP (MIP) can be used to enable seamless switching between different kinds of WAN links (e.g. WWAN/WLAN). The mobile node hereby remains reachable via the same IP address (home address) at any time, independently of the WAN link being used. Effectively, any WAN link switch causes very small outages during switchover while keeping all IP connections alive.

Moreover, NetModule routers also support NAT-Traversal for mobile nodes running behind a firewall (performing NAT), which makes mobile nodes even there accessible from a central office via their home address, and thus, bypassing any complicated VPN setups.

The home agent accomplishes this by establishing a tunnel (similar to a VPN tunnel) between itself and the mobile node. WAN link switching works by telling the home agent that the WAN IP address (called the care-of address in MIP terms) of the mobile node has changed. The home agent will then encapsulate packets destined to a mobile node’s home address into a tunnel packet containing the current care-of address of the mobile node as its destination address.

To prevent problems with firewalls and private IP addressing, the MIP implementation always employs reverse tunneling, which means that all traffic sent by a mobile node is relayed via the tunnel to the home agent instead of directly being conveyed to the final destination. This fact also empowers MIP to be used as a lightweight VPN replacement (without payload secrecy).

The MIP implementation supports RFCs 3344, 5177, 3024 and 3519. For applications requiring vast numbers of mobile nodes, interoperability with the Cisco 2900 Series home agent implementation has been verified. However, since NetModule routers implement a mobile node as well as a home agent, a MIP network with up to 10 mobile nodes can be implemented without requiring expensive third party routers.