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[apnic-talk] [Apnic-announce] AS number change could affect Internet rou

Subject: [apnic-talk] [Apnic-announce] AS number change could affect Internet routing from 1 January 2009
Date: Fri, 25 Jul 2008 11:00:03 +1000 EST

AS number change could affect Internet routing from 1 January 2009

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

Regional Internet Registries (RIRs), including Asia Pacific Network
Information Centre (APNIC), have warned that routers and network
management software should be upgraded ahead of the increased
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 numbers
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 having
routers and network administration systems that won't accept the
expanded four-byte number format. As such, the RIRs urge operators to
verify their vendors' routers will support four-byte AS numbers.

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 preparation
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 encounter
some significant network routing problems. We're extremely concerned
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 routers,
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 numbers.

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                  http://www.apnic.net
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