12.2. Delegating Router Behavior

12.2. Delegating Router Behavior

When a delegating router receives a Request message from a requesting router that contains an IA_PD option, and the delegating router is authorized to delegate prefix(es) to the requesting router, the delegating router selects the prefix(es) to be delegated to the requesting router. The mechanism through which the delegating router selects prefix(es) for delegation is not specified in this document. Section 11.2 gives examples of ways in which a delegating router might select the prefix(es) to be delegated to a requesting router.

A delegating router examines the prefix(es) identified in IA_PD Prefix options (in an IA_PD option) in Renew and Rebind messages and responds according to the current status of the prefix(es). The delegating router returns IA_PD Prefix options (within an IA_PD option) with updated lifetimes for each valid prefix in the message from the requesting router. If the delegating router finds that any of the prefixes are not in the requesting router's binding entry, the delegating router returns the prefix to the requesting router with lifetimes of 0.

The delegating router behaves as follows when it cannot find a binding for the requesting router's IA_PD:

Renew message: If the delegating router cannot find a binding for the requesting router's IA_PD the delegating router returns the IA_PD containing no prefixes with a Status Code option set to NoBinding in the Reply message.

Rebind message: If the delegating router cannot find a binding for the requesting router's IA_PD and the delegating router determines that the prefixes in the IA_PD are not appropriate for the link to which the requesting router's interface is attached according to the delegating routers explicit configuration, the delegating router MAY send a Reply message to the requesting router containing the IA_PD with the lifetimes of the prefixes in the IA_PD set to zero. This Reply constitutes an explicit notification to the requesting router that the prefixes in the IA_PD are no longer valid. If the delegating router is unable to determine if the prefix is not appropriate for the link, the Rebind message is discarded.

A delegating router may mark any prefix(es) in IA_PD Prefix options in a Release message from a requesting router as "available", dependent on the mechanism used to acquire the prefix, e.g., in the case of a dynamic pool.

The delegating router MUST include an IA_PD Prefix option or options (in an IA_PD option) in Reply messages sent to a requesting router.