Mobile IP was originally defined for IP version 4, before IPv6 existed. The base protocol is defined in RFC 2002. Many enhancements have been proposed to Mobile IPv4 to counter some of the identified problems, which include:
Triangular routing as shown in Figure 1. All packets sent to the mobile node are routed through its home agent, causing increased load on the home network and higher latency. This problem could be solved with route optimization extension, but the required update may not be practical.
Deployment problem: Mobile IPv4 typically requires each potential foreign network to have foreign agent(s). If foreign agents were not used, every mobile node would need a globally routable IPv4 address from the foreign network.
Ingress filtering: In an ISP (Internet Service Provider), any border router may discard packets that contain a source IP address that is not topologically correct. In Mobile IPv4, the Mobile nodes that are away from home, i.e., in a foreign ISP, use their home address as the source IP address, resulting in the likelihood of dropping of packets by ingress filtering.
Authentication and Authorization: Mechanisms specific to Mobile IPv4 are used for authentication of Mobile IPv4 registrations. Mobile IPv4 has only a small percentage (a few million nodes) of the overall IPv4 deployment. A shortage of globally routable IPv4 addresses and use of private IPv4 addresses with Network Address Translators hampers its deployment in many cases.
Triangular routing as shown in Figure 1. All packets sent to the mobile node are routed through its home agent, causing increased load on the home network and higher latency. This problem could be solved with route optimization extension, but the required update may not be practical.
Deployment problem: Mobile IPv4 typically requires each potential foreign network to have foreign agent(s). If foreign agents were not used, every mobile node would need a globally routable IPv4 address from the foreign network.
Ingress filtering: In an ISP (Internet Service Provider), any border router may discard packets that contain a source IP address that is not topologically correct. In Mobile IPv4, the Mobile nodes that are away from home, i.e., in a foreign ISP, use their home address as the source IP address, resulting in the likelihood of dropping of packets by ingress filtering.
Authentication and Authorization: Mechanisms specific to Mobile IPv4 are used for authentication of Mobile IPv4 registrations. Mobile IPv4 has only a small percentage (a few million nodes) of the overall IPv4 deployment. A shortage of globally routable IPv4 addresses and use of private IPv4 addresses with Network Address Translators hampers its deployment in many cases.
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