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Draft Policies and Proposals

Policy 2005-9: 4-Byte AS Number
Policy Proposal Evaluation Status: Author
Adopted - NRPM Section 5.1 Geoff Huston
Discussion Tracking
Mailing List:
Formal introduction on PPML on 19 December 2005
Last call from 14 April through 28 April 2006
Public Policy Mailing List
ARIN Public Policy Meeting: ARIN XVII
ARIN Advisory Council: 15 December 2005
26 January 2005
16 February 2006
23 March 2006
11 April 2006
4 May 2006
25 May 2006
15 June 2006
ARIN Board of Trustees: 9 May 2006
27 July 2006
Revisions Implementation
Click here to view previous versions 1 January 2007

Proposal

Policy Proposal 2005-9: 4-Byte AS Number

Policy statement:

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

- Commencing 1 January 2007 the registry will process applications that specifically request 32-bit only AS Numbers and allocate such AS numbers as requested by the applicant. In the absence of any specific request for a 32-bit only AS Number, a 16-bit only AS Number will be allocated by the registry.

- Commencing 1 January 2009 the registry will process applications that specifically request 16-bit only AS Numbers and allocate such AS Numbers as requested by the applicant. In the absence of any specific request for a 16-bit only AS Number, a 32-bit only AS Number will be allocated by the registry.

- Commencing 1 January 2010 the registry will cease to make any distinction between 16-bit only AS Numbers and 32-bit only AS Numbers, and will operate AS number allocations from an undifferentiated 32-bit AS Number allocation pool.

Terminology

"16-bit only AS Numbers" refers to AS numbers in the range 0 - 65535

"32-bit only AS Numbers" refers to AS Numbers in the range 65,536 - 4,294,967,295

"32-bit AS Numbers" refers to AS Numbers in the range 0 - 4,294,967,295

Rationale:

Recent studies of AS number consumption rates indicate that the existing 16-bit 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 32-bit field [3].

It is noted that some advance period may be required by network operators to undertake the appropriate procedures relating to support of 32-bit 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 16-bit 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 32-bit 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

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