TABLE OF CONTENTS When a mobile node communicates with other nodes, all packets are forwarded by a home agent if the mobile node is away from home. This causes a communication delay, especially if the mobile node and its peer node are located on networks that are topologically close and the home agent is far away. The worst case is when both nodes are on the same network.
The Mobile IPv6 specification provides a solution for this problem. If the peer node supports the Mobile IPv6 correspondent node function, the path between a mobile node and the peer node can be optimized. To optimize the path, a mobile node sends a Binding Update message to the correspondent node. The message must not have the H and L flags set because the message is not requesting home registration. The A flag may be set; however, it is not mandatory. If the A flag is set, a correspondent node replies with a Binding Acknowledgment message in response to the Binding Update message. Note that even if the A flag is not set, a correspondent node must reply to the mobile node with a Binding Acknowledgment message when an error occurs during the message processing except in the authentication error case.
A Binding Update message must be protected by the return routability procedure, discussed in the next section. The message must contain a Binding Authorization Data option. The option contains a hash value of the Binding Update message, which is computed with the...
