10.6.1 Prefix solicitation

As the lifetime of the mobile node's home address becomes expired, the mobile node sends a Mobile Prefix Solicitation message to its home agent to update or to get fresh prefix information. The Mobile Prefix Solicitation message is very similar to the Router Solicitation message in Neighbor Discovery protocol. ^[6] Only difference between them is that Mobile Prefix Solicitation message is originated by the mobile node in a foreign link and delivered to its home agent while Router Solicitation message is routed directly to the router. The important points on building the Mobile Prefix Solicitation message is as follows:

• The Home Address option should be contained to carry the mobile node's home address in the message.

• IPsec should be used.

• The Identifier field in the ICMP Header should be set to a random value.

To prevent mobile node from using invalid home addresses, the Lifetime field value should be set smaller than the remaining lifetime of its home registration.

10.6.2 Prefix advertisement

For mobile nodes which are away from home, routers working as mobile node's home agents should advertise prefix information to the mobile node using Mobile Prefix Advertisement message. The mobile node may solicit the advertisement message, instead of waiting for periodical advertisement messages. Mobile Prefix Advertisement and Solicitation messages are explained in Section 7.

Unsolicited Mobile Prefix Advertisement messages from the home agent are generated as follows:

• The Source Address field of IPv6 Header is set to the home agent's IP...