[arin-ppml] ARIN-2012-3: ASN Transfers - Last Call

William Herrin bill at herrin.us
Wed May 9 20:30:42 EDT 2012

On 5/9/12, John Curran <jcurran at arin.net> wrote:
>>  ARIN-2012-3: ASN Transfers
> I was asked recently about the number of issued and not presently
> advertised ASN's in the ARIN region, and thought it best to reply
> publicly so everyone has the same information.
> ARIN does not directly monitor ASN usage, but the esteemed
> Geoff Huston does at <http://www.potaroo.net/tools/asn32/>
> >From that report as of this morning -
>    There are 24406 16-bit ASN's assigned to the ARIN region, with
>    1099 presently in the regional free pool, 8259 unadvertised in
>    BGP, and 15048 advertised in BGP.


For folks looking for a reason for AS number transfers, here's a thought:

Implementing BGP communities is a nuisance with a 32-bit AS number.
The convention is: 16 bits AS number, 16 bits tag. Virtually every
shipping router is configured to display them in this manner. AS
numbers larger than 65535 require a service provider who wants to
offer communities to implement it in an unconventional manner. This
can be expected to cause collisions and other confusion in this
tagging mechanism for downstreams with more than one BGP link. Where
an organization wishes to implement communities, a 16-bit AS number is
*highly* desirable on a technical basis.

Geoff's numbers suggest that there are upwards of 8,000 16-bit as
numbers recoverable in the ARIN region, some third of the total. Given
some incentive for the current holders to release them of course. When
we run out of fresh 16-bit AS numbers, the availability of those 8,000
would simplify operations for new ISPs and new ISP efforts which use a
distinct AS number.

Tom, is that a good enough reason to allow an AS number transfer? As a
technical necessity to follow the conventions for BGP communities?

Bill Herrin

William D. Herrin ................ herrin at dirtside.com  bill at herrin.us
3005 Crane Dr. ...................... Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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