12. Annual Review

Given the dynamic nature of IPv4 multicast and its associated infrastructure, and the previously undocumented IPv4 multicast address assignment guidelines, the IANA should conduct an annual review of currently assigned addresses.

12.1. Address Reclamation

During the review described above, addresses that were mis-assigned should, where possible, be reclaimed or reassigned.

The IANA should also review assignments in the AD-HOC, "DIS Transient Groups", and ST Multicast Groups [RFC1819] blocks and reclaim those addresses that are not in use on the global Internet (i.e., those applications that can use SSM, GLOP, or Administratively Scoped addressing, or are not globally routed).

12.2. Positive Renewal

It is occasionally appropriate to make temporary assignments that can be renewed as necessary. In cases where this happens the registrant needs to positively request an extension to the temporary assignment or the addresses assigned. When the IANA has not received a request to renew the registration of a temporary assignment within 30 days of the expiry of the assignment, it MUST be removed from the multicast registry.

Addresses returned to the IANA when a temporary assignment ends MUST NOT be assigned to anyone other than the last registrant for at least one calendar year.