ge receipt of the Binding Update message. 168 Wi-Fi Integration to the 4G Mobile Network - 7) Binding Error. This message is transmitted by the correspondent node or by the home agent if the Binding Update message is incorrect. Checksum: this field, coded on two bytes, contains the checksum calculated on the pseudo-header and the mobility extension. Message Data: this variable size field contains the data corresponding to the type of mobility extension. The mobility extension can also include the following options: - Pad1: this option is used to insert a padding byte; - PadN: this option is used to insert several bytes of padding; - Binding Refresh Advice: this option is associated with the mobility extension Binding Acknowledgment passed by the home agent. It specifies the value of the timer used by the mobile node to update its registration; - Alternate Care-of Address: this option is associated with the mobility extension Binding Update. It specifies the CoA if it cannot be deduced from the source address of the IPv6 header; - Nonce Indices: this option is associated with the mobility extension Binding Update passed to the correspondent node. It contains random numbers (nonce) needed for calculating cryptographic information (Home Keygen Token, Care-of Keygen Token); - Binding Authorization Data: this option is associated with the mobility extensions Binding Update and Binding Acknowledgment. It contains cryptographic information from which the destination can verify that the message originates from a node with which the Return Routability procedure has occurred. 9.1.1.2. Destination extension The Home Address option of the Destination extension indicates the HoA of the mobile node. The Destination extension is used for the direct transfer of data from the mobile node to the correspondent node. S2c Tunnel Establishment The mobile node cannot use the HoA as the source address because the router of the foreign network can delete the packet if the source does not belong to the local network. The mobile node is th