Background
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]. Standardisation 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.
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)
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