9. IANA Considerations

This document expands the pool for AS numbers from 0-65535 to 0-4294967295. The AS numbers are managed by the IANA "Autonomous System Numbers" registry. Other than expanding the AS number pool, this document does not propose any modifications to the existing policies and procedures pertaining to the allocation of AS numbers.

This document uses a BGP capability code to indicate that a BGP speaker supports four-octet AS numbers. Capability Code 65 has been assigned by IANA per [RFC5492].

In addition, this document introduces two BGP optional transitive attributes, and their type codes have been assigned by IANA. The first one is the AS4_PATH attribute, value 17, which preserves the AS path information with four-octet AS numbers across old BGP speakers. The second one is the AS4_AGGREGATOR attribute, value 18, which is similar in use to the current AGGREGATOR attribute, but it carries a four-octet AS number.

Finally, IANA has replaced a reference to RFC 4893 with a reference to this document for a reserved two-octet AS number -- AS_TRANS (23456). Also, IANA has replaced a reference to RFC 4893 with a reference to this document for the "32-bit Autonomous System Numbers" registry.