Network Working Group                                      G. Michaelson
Request for Comments: DRAFT                                        APNIC
Expires December 2006


             Canonical representation of 4-byte AS numbers

draft-michaelson-4byte-as-representation-00.txt


Status of this Memo


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                                Abstract

    A single representation for 4-byte AS numbers is proposed, to avoid any
    confusion in interpreting the two 2-byte quantities that make them. The
    syntax chosen avoids collision with BGP community string parsing of AS
    numbers.

    It is recommended that only this representation be used by all documents
    and systems referring to 4-byte AS numbers.
    Nomenclature


1.0 Proposed canonical 4-byte AS representation

4 Byte AS numbers are defined in [1].

It is proposed to identify 4-byte AS Numbers using a syntax of
<high order 16 bit value in decimal>.<low order 16 bit value in decimal>.

Accordingly, a 4-byte AS Number of value 65546 (decimal) would be
identified as "1.10".

2.0 Terminology

    "2-byte only AS Numbers" refers to AS Numbers in the range 0 - 65535

    "4-byte only AS Numbers" refers to AS Numbers in the range 1.0 -
    65535.65535 (decimal range 65,536 - 4,294,967,295)

    "4-byte AS Numbers" refers to AS Numbers in the range 0.0 - 65535.65535
    (decimal range 0 - 4,294,967,295)

3.0 Discussion

   To avoid confusion, a single notation to represent 4-byte AS is
   required.  Initially, the ":" was proposed to separate the 2-byte
   components. However this clashes with use of the ":" character in
   community attribute syntax.

   This notation has been informally adopted by at least one vendor, and
   used consistently in presentations in the RIR community towards the
   deployment of 4-byte AS. Therefore it seems sensible to formalize its
   use as the preferred representation of a 4-byte AS.

4.0 Author's Note:

   This proposal was motivated by a discussion with Geoff Huston. The
   text of the definition of a 4-byte AS is taken from [2].

5.0 Security Considerations

   Security considerations are not discussed in this memo.

6.0 Author's  Address:

   George Michaelson
   APNIC
   Level 1, 33 Park Road, Milton, Q4064 Australia

7.0 References

[1] http://www1.ietf.org/internet-drafts/draft-ietf-idr-as4bytes-12.txt
[2] http://www.ripe.net/ripe/policies/proposals/2005-12.html

8.0 Comments & Feedback

Comments are solicited and should be addressed to the working group's
mailing list at idr@ietf.org and/or the author.

9.0 Authors email address

ggm@apnic.net

10.0 Copyright Declaration

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