ARIN-PPML Message

[ppml] Policy Proposal 2005-9: 4-Byte AS Number

On December 15, 2005, the ARIN Advisory Council concluded its review of
proposed policy 4-Byte AS Number Policy Proposal and agreed to forward 
it as a formal proposal for discussion by the community. This proposal 
is designated Policy Proposal 2005-9: 4-Byte AS Number. The policy 
proposal text is below and can be found at:

http://www.arin.net/policy/proposals/2005_9.html

All persons in the community are encouraged to discuss Policy Proposal
2005-9 in the weeks leading to the ARIN Public Policy Meeting in
Montreal scheduled for April 10-11, 2006. Both the discussion on the
Public Policy Mailing List and at the public policy meeting will be used
to determine the community consensus regarding this policy proposal.

The ARIN Internet Resource Policy Evaluation Process can be found at:
http://www.arin.net/policy/irpep.html

ARIN's Policy Proposal Archive can be found at:
http://www.arin.net/policy/proposals/proposal_archive.html

Regards,

Member Services
American Registry for Internet Numbers (ARIN)


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Policy Proposal Name: 4-Byte AS Number

Author: Geoff Huston

Policy Term: Temporary (1 January 2007 - 1 January 2010)

Policy Statement:

          This policy proposal nominates 3 dates for changes to the
          current AS Number allocation policy for the registry:

          On 1 January 2007 the registry will process applications that
          specifically request 4-byte only AS Numbers and allocate such
          AS Numbers as requested by the applicant. In the absence of
          any specific request for a 4-byte only AS Number, a 2-byte
          only AS Number will be allocated by the registry.

          On 1 January 2009 the registry will process applications that
          specifically request 2-byte only AS Numbers and allocate such
          AS Numbers as requested by the applicant. In the absence of
          any specific request for a 2-byte only AS Number, a 4-byte
          only AS Number will be allocated by the registry.

          On 1 January 2010 the registry will cease to make any
          distinction between 2-byte only AS Numbers and 4-byte only AS
          Numbers, and will operate AS number allocations from an
          undifferentiated 4-byte AS Number allocation pool.

          Nomenclature

          It is proposed to identify 4-byte AS Numbers using a syntax of
          <high order 16 bit value in decimal>:<low order 16 bit value
          in decimal>. Accordingly, a 4-byte AS number of value 65546
          (decimal) would be identified as "1:10".

          Terminology

          "2-byte only AS Numbers" refers to AS numbers in the range 0 -
          65535

          "4-byte only AS Numbers" refers to AS Numbers in the range 1:0
          - 65535:65535 (decimal range 65,536 - 4,294,967,295)

          "4-byte AS Numbers" refers to AS Numbers in the range 0:0 -
          65535:65535 (decimal range 0 - 4,294,967,295)

Rationale:

          Recent studies of AS number consumption rates indicate that
          the existing 2-byte pool of unallocated AS Numbers will be
          exhausted sometime in the period between 2010 and 2016, absent
          of any concerted efforts of recovery of already-allocated AS
          Numbers [1] [2]. Standardization work in the IETF has produced
          a document that is currently being submitted as a Proposed
          Standard that will expand the AS Number space to a 4-byte
          field [3].

          It is noted that some advance period may be required by
          network operators to undertake the appropriate procedures
          relating to support of 4-byte AS numbers, and while no flag
          day is required in the transition to the longer AS Number
          field, it is recognised that a prudent course of action is to
          allow for allocation of these extended AS numbers well in
          advance of an anticipated 2-byte AS Number exhaustion date.

          This policy proposal details a set of actions and associated
          dates for RIR AS Number allocation policies to assist in an
          orderly transition to use of the 4-byte AS Number space.

          The essential attributes of this policy proposal are to
          facilitate the ease of transitional arrangements by equipment
          vendors, network managers and network operations staff, to
          provide the industry with some predictability in terms of
          dates and associated actions with respect to registry
          operational procedures for AS Number allocations.

          References

          [1]  Daily AS Number Report,
               http://www.potaroo.net/tools/asns
          [2]  ASNs MIA: A Comparision of RIR Statistics and RIS
               Reality, http://www.nanog.org/mtg-0510/wilhelm.html
          [3]  BGP Support for Four-octet AS Number Space,
               draft-ietf-idr-as4bytes-12.txt

Timetable for implementation:

	Procedures to support this proposal need to be implemented
	by 1 January 2007