More Number Scarcity

by Leo Vegoda on April 2, 2012

Last year ICANN allocated the last five IPv4 blocks to the Regional Internet Registries (RIRs). Since then we have seen a concerted effort on the part of network and content providers to make sure they support IPv6, so they’ll be ready for the next few billion Internet users. But there’s another Internet number resource which is running short: 16-bit Autonomous System Numbers (ASNs).

Internet networks learn how to reach destinations (IP addresses) using an IETF protocol called the Boarder Gateway Protocol (BGP). BGP uses unique Autonomous System (AS) numbers to identify individual networks (routing domains) in order to announce the reachability of destinations (IP addresses). Originally, BGP used 16-bit numbers, allowing slightly more than 65,000 ASs

Internet growth in the 1990s made it clear that a 16-bit number space is insufficient and the first proposals for a 32-bit number space, allowing about 4.3 billion AS numbers, were published in 2001. In parallel with this work, the addressing community began developing a transition policy in the RIRs’ open policy forums and socialising it with network operators, the consumers of AS numbers.

The IETF work was published as a standards track RFC in 2007. And while IPv4 and IPv6 networks do not interoperate, networks that don’t know about 32-bit AS numbers can still communicate with networks using 32-bit AS number using a transition mechanism described in the RFC. The RIR community work was ratified as a Global Policy in 2008 and included a timetable for the transition. This echoed the timetables the addressing communities had agreed to in the policies governing AS number assignments in each of their regions.

These regional policies have promoted 32-bit AS number assignments and now require the RIRs to treat all AS numbers as part of the same 32-bit pool. Unfortunately, lots of networks reported problems making use of 32-bit ASNs. In the region served by the RIPE NCC, which has had the most success at assigning 32-bit ASNs [PDF, 2.66 MB] (PDF slides 8 & 9), they still comprise just a third of the total ASN assignments. The reason for the huge disparity in acceptance between the five regions is not clear. Earlier this month, John Curran, ARIN’s CEO & President, asked the ARIN community for an easy, straightforward answer to this question.

One of the reasons networks have problems deploying 32-bit AS numbers is that network providers who have not upgraded their equipment will see the same transition AS number being used by different network providers. This duplication of AS numbers causes problems for monitoring tools and even path selection mechanisms. But there are just three blocks of 16-bit ASNs left, so the time is rapidly approaching when networks won’t be able to swap out a 32-bit AS number for a 16-bit replacement AS number. There won’t be any new 16-bit AS numbers left.

Much has been written about the lack of IPv4 addresses and its impact on the potential economic growth of countries and industries.  The need to transition to IPv6 has triggered coordinated action plans from major network, content and access providers to support both IPv4 and IPv6.  However, little attention has been paid to the diminishing pool of 16-bit ASN numbers, which are another enabler of Internet growth.  The technical community has defined a 32-bit ASN specification; the addressing communities have implemented suitable assignment policies; what is now needed is widespread acceptance of 32-bit AS numbers by network providers.


Stéphane Bortzmeyer 04.03.12 at 1:10 am

“Boarder Gateway Protocol” is a protocol for the ICANN board? :-)

Jim Fleming 04.05.12 at 1:01 pm

“Unfortunately, lots of networks reported problems making use of 32-bit ASNs.”…”The reason for the huge disparity in acceptance between the five regions is not clear.”
1. When people begin to work with large numbers that are artificially made scarce, such as 32-bit ASNs, they have to ask the obvious question: Why are there ONLY five regions ?

2. Unique 32-bit ASNs can easily be mapped from either a 5-bit or 6-bit alphabets and common brand names of 6 or 5 letters. There is
no need for IANA or RIRs.

3. Legacy 16-bit ASNs are desirable because (some) people think the day may come when /16s are the basic unit of IANA allocation in address spaces, as opposed to /8s.

The U.S. FCC may be in the best position to sort out what amounts to a Spectrum Management Task. Free market forces in the .USA may also play a role. Those forces may favor small and scarce like 16-bit ASNs.

Free 30-bit ASNs spread across the 32-bit spectrum may also cause people to value 16-bit ASNs

Jim Fleming 04.05.12 at 5:02 pm

“Last year ICANN allocated the last five IPv4 blocks to the Regional Internet Registries (RIRs). ”
“There won’t be any new 16-bit AS numbers left.”

ICANN and the RIRs have thrived on initial (virgin) allocations.

The U.S. telecom market is the only one in the world that encourages Free-Market forces. That allows the best of breed to emerge.

ICANN was not created to last forever. If all goes well, network operators will have more choices.

Who knows ? Maybe a .ASN top level domain will catch on where people register their ASNs and buy and sell them.

There may also be a movement to segregate 16-bit players and 32-bit players into Rings or Clouds. There is a bit allocated for that in the 160-bit IP Header with VVRR as the first 4 bits. IPv4 (0100) is Ring 0 to Ring 0.

The IEEE, ITU, FCC plus the Free Market will likely play a part in how ASNs (Artificially Scarce Numbers) are managed.

Jim Fleming 04.06.12 at 2:14 pm

There is another school of thought that “LESS is MORE”

12-bits may be sufficient for a US FCC regulated ASN community

The US FCC has now engaged major carriers to combat route hi-jacking. That is easier to do when there are less ASNs considered to be “valid” in the Internet CORE (Ring 0 as opposed to Ring 1)

Route-hijacking and other games are made easier with BGP. People now want to restrict and secure BGP to end the games. Fewer ASNs may give people the impression things are better (controlled/managed).

12-bits would be easier than 16-bits to use as a replacement for /8s in the IANA allocations.

12-bits also are interesting when mapped to 16-bits with guard bits (G)
It only takes 3 symbols from a 4-bit alphabet to ID a carrier – the US FCC has a lot of experience with call letters and radio licensing

Carriers would likely jump at the chance to be one of the Top 4096 ASNs sanctioned (accredited) by the US FCC or the ITU

If the US Government and FCC legislate a smaller CORE and have the rest of the world proxy via IPv6 (or whatever) then Americans may enjoy a more stable, secure and higher performance platform.

With a 32-bit ASN there is little value in being unique or exclusive – an ISP is one of 4+ billion – nothing special.

Jim Fleming 04.07.12 at 7:58 am

If the following 4-bit Alphabet is used to create 16-bit ASNs

“0123 4567 89AB CDEF”

F A C E = 0xB2C0 = 45760

If “0123456789ABCDEF” was used then FACE=64206

The 4-bit Alphabet can also be used to create 12-bit ASNs and Ports and Realms and TLDs .ETC

.ETC = 0x01c = 28

Jim Fleming 04.08.12 at 9:29 am

From the ZOOM://BOX

30-bit ASNs are FREE – no RIRs or IANA needed – just select your 6-letter BRAND*** and buy a LLLLLL.NET domain (for now, before the .NET RE-Launch using Name.Coin)

or buy a .ASN domain ?

*** use the 5-bit binary Alphabet “0[A-Z]12389″

30-bits are handy – they fit in the DNS AAAA records for multi-homing with 30+30+68 – two 30-bit legacy LOCations on Ring 0 and Ring 1 and a 68-bit ID


12-12-12 is an important Flag.Day for 12-bit fields

A ZOOM://BOX has no back-haul to the legacy Internet – Mules (clients) move info from Community to Community
see also http://TIGER.TOYS

Jim Fleming 04.11.12 at 7:55 am

from the ZOOM://BOX

the S.A.N.D alphabet only has 4 symobols “SAND”

S=00 A=01 N=10 D=11

ASN=010010 which is 0x12 = 18 decimal = 022 (octal)

.ASN can be one symbol or icon with a 6-bit code point (022)

.DNS=111000 = 030 (octal) = 24 decimal

FRAG6 comes from the deprecated Fragmentation Field in the 160-bit IP Header. The 13 bits are reduced to 12 with the left-most bit joining the 0MF bits for a 4-bit Mode Field. The 12 remaining FRAG bits are split 6+6 for Source and Destination addressing. Those bits are 000000 for now which is .AAA

.DNS .ASN has .AAA

Jim Fleming 04.11.12 at 4:06 pm

“.DNS .ASN has .AAA”

.BTW – Where did AAA go ?
aaa Authentication, Authorization and Accounting

Who knows ?

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