The use of the binding cache and IPv6 encapsulation provides a mechanism to enable optimal routing to Mobile hosts. This mechanism, however, relies on the bindings contained within that cache being accurate and up to date. Indeed, to protect against total machine failure (which is common in a mobile environment due to battery life constraints, etc.) and long periods of network disconnection by Mobile Nodes, binding cache entries for a Mobile Node must persist even after a period of total disconnection or loss of state by Mobile or Correspondent Nodes.

Mobile IPv6 maintains binding cache coherence through the use of binding update, binding acknowledgement and binding request messages. The remainder of this section describes these messages in detail, and how they interoperate to provide accurate and timely binding cache coherence.

Binding update, acknowledgement and request messages are all carried inside IPv6 destination options, each with their own destination option type. Utilising IPv6 destination options gives several advantages over less integrated methods of control messaging. Firstly, messages can be placed inline with the header of existing IPv6 packets, thereby reducing the packet transmission overhead of the message. Secondly, as no transport layer protocol is involved in the transmission of the message, fewer issues exist concerning the blocking of control messages by firewalls.