[afnog] Fwd: AS number change could affect Internet routing from 1 January 2009

Mark Tinka mtinka at globaltransit.net
Fri Jul 25 08:33:34 UTC 2008

Thought I'd share this.



----------  Forwarded Message  ----------

Subject: AS number change could affect Internet routing from 
1 January 2009
Date: Friday 25 July 2008
From: secretariat at apnic.net
To: mtinka at globaltransit.net


AS number change could affect Internet routing from 1 
January 2009

    Manufacturers urged to upgrade routers and network 
    software to support the use of four-byte Autonomous 
System numbers
    by 1 January 2009.

Regional Internet Registries (RIRs), including Asia Pacific 
Information Centre (APNIC), have warned that routers and 
management software should be upgraded ahead of the 
distribution of four-byte (also known as 32-bit) Autonomous 
System (AS)

AS numbers are a vital part of the Internet's core routing 
system, the
Border Gateway Protocol (BGP). With existing two-byte AS 
predicted to run out in early 2011, RIRs will issue 
four-byte AS numbers
by default (unless otherwise specifically requested) 
beginning 1 January
2009, as the next phase of a transition from two- to 
four-byte numbers.
Following a globally coordinated policy, RIRs began 
allocating four-byte
AS numbers by request only in January 2007; January 2009 
marks the
transition to allocating four-byte AS numbers by default.

Without timely support from vendors, network operators risk 
routers and network administration systems that won't accept 
expanded four-byte number format. As such, the RIRs urge 
operators to
verify their vendors' routers will support four-byte AS 

Geoff Huston, Chief Scientist at APNIC, expressed severe 
concerns over
failure to prepare for four-byte AS numbers: "AS numbers are 
often used
to identify external relationships, set routing attributes, 
and manage
traffic. Learning from our current experiences with IPv6 
issues, Internet engineers designed four-byte AS numbers to 
be backward
compatible with much of the installed network 
infrastructure. But new
entrants and networks that are expanding or merging will 
need new AS
numbers and as of 1 January 2009 these will be, by default, 
four-byte AS
numbers. If router software and support systems in critical 
parts of the
Internet's infrastructure aren't upgraded by January, we'll 
some significant network routing problems. We're extremely 
that a lot of routers and network management software out 
there cannot
and will not be able to recognize four-byte AS numbers".

An Autonomous System (AS) is a collection of networks, or 
administered as a group sharing a common set of routing 
policies, each
defined with a unique number, or AS number. Massive Internet 
growth has
depleted the existing pool of two-byte AS numbers (65,536 
numbers in
total). As a result, engineers have expanded the AS number 
space from
two bytes to four-bytes, to include over 4 billion AS 
numbers. Some
routers do not currently support the use of four-byte AS 

To help vendors understand what they need to do to provide 
four-byte AS
number support and to help network operators find products 
that support
four-byte AS numbers, APNIC has set up a special website at:


Yours sincerely


APNIC Secretariat
Asia Pacific Network Information Centre (APNIC)     Tel: +61 
7 3858 3100
PO Box 2131 Milton, QLD 4064 Australia              Fax: +61 
7 3858 3199
Level 1, 33 Park Road, Milton, QLD                  

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