16 vs 32 bit ASNs [Re: BBC does IPv6 ;) (Was: large multi-site enterprises and PI]

Chris Burton ChrisB at VMC.com
Mon Nov 29 23:25:34 UTC 2004


	
	These are the same arguments that are presented each time
something new comes along to replace something old.  When IPv4 first
came along nobody thought all of the 4 billion plus address could ever
be used; but we were wrong.  16-bit ASNs have served their place and
will continue to serve for the time being.  Those who fail to plan, plan
to fail.

	It is highly doubtful that the policies in place will become
more relaxed with the introduction of 32-bit ASNs, the more likely
scenario is that they will stay the same or get far stricter as with
assignments of IPv4 or IPv6 addresses.  As you had mentioned though, in
the near term this definitely would not be scalable, but who knows what
is going to happen 10, 15, or more years from now.

	I think your numbers may be a little off 2^32 = 4,294,967,296;
current world population give or take a few million is hovering around
6,300,000,000 according to the US Gov.  If everyone and the mother would
like an ASN (Which is highly unlikely) you would need just a few more to
make that work.

Chris

-----Original Message-----
From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On Behalf Of
Pekka Savola
Sent: Monday, November 29, 2004 11:41 AM
To: Owen DeLong
Cc: Jeroen Massar; Cliff Albert; nanog at merit.edu
Subject: Re: 16 vs 32 bit ASNs [Re: BBC does IPv6 ;) (Was: large
multi-site enterprises and PI]


On Mon, 29 Nov 2004, Owen DeLong wrote:
>> Also, with 32bit ASN's, also expect upto 2^32 routes in your routing
>> table when each and every ASN would at least send 1 route and of
course
>> there will be ASN's sending multiple routes.
>
> Only if EVERY ASN were allocated and active.  You and I both know this
> doesn't begin to approach reality.  Slightly more than half of current
> ASNs are actually in the routing table.  The ASN issuance rate is not
likely
> to go up simply because we go to 32 bit ASNs.  Probably we are really
talking
> about a need for 20 bit ASNs or so, generally, but, 32 bits is a much
more
> convenient boundary for lots of code implementations and lots of
hardware,
> so, 32 bits is the chosen number for the sake of simplicity.

Of course, every ASN would not be active.  But if we'd have 32 bit 
ASNs, there would be "no need" (or so folks would argue) to be strict 
in the policies -- everyone and their uncle could have one.  Folks 
could even get ones for their homes, theis SOHO deployments, or their 
3-person, on-the-side consulting companies.  And logically, each of 
these should have their own PI prefixes and a slot in the global 
routing table.

Scalable? NO.  Not just the number of routes, but also the churn those 
routes would make.. Oh god.

It's better to try to stick to 16 bit ASNs for now, and make stricter 
policies and reclaim the space if needed.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings





More information about the NANOG mailing list