The Mobile IPv6 (MIPv6) protocol [RFC3775] is a proposed standard by the IETF to provide transparent host mobility within IPv6. The protocol enables a Mobile Node to move from one network to another without the need to change its IPv6 address. A Mobile Node is always addressable by its home address, which is the IPv6 address that is assigned to the node within its home network. When a Mobile Node is away from its home network, packets can still be routed to it using the node’s home address. In this way, the movement of a node between networks is completely invisible to transport and other higher layer protocols.
Mobile Nodes participating in the MIPv6 protocol each have a persistent home address, which can be used to address the Mobile Node irrespective of its current point of attachment to the IPv6 network. The IPv6 network which matches the home address’ prefix is known as the home network. Mobile Nodes also adopt a Home Agent - an IPv6 capable router directly connected to the home network. This process may either be static, or dynamic, via the MIPv6 Home Agent discovery mechanism. The Home Agent is responsible for the interception and forwarding of IPv6 packets to the Mobile Node which are incorrectly routed to the home network while the Mobile Node is away from home.
When a Mobile Node is attached to its home network it operates as any other network node, so no special routing is required. When a Mobile Node moves to a foreign network, it uses IPv6 autoconfiguration to discover the new network and to allocate a care-of address within the address space of that network. However, to ensure that IPv6 packets destined for the Mobile Node’s home address reach the proper location as efficiently as possible, the routing information pertaining to the Mobile Node’s home address must be updated in both the Home Agent and any relevant Correspondent Nodes. MIPv6 provides this functionality by the introduction of a bindings cache on the Mobile and Correspondent Nodes and binding update messages which are transmitted in a new IPv6 extension header called the mobility header.
Although MIPv6 implementations have been around since 1998 most have fallen out of date as the MIPv6 protocol has progressed over the years. However, there are a handful of available implementations that are fairly up to date with either MIPv6 draft version 24 or RFC 3775 (which is based on draft version 24). Yet these implementations can still differ slightly in their supported features and are not likely to be completely 100% interoperable in most cases.