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Network Working Group G. Huston Request for Comments: 5396 G. Michaelson Category: Standards Track APNIC

                                                         December 2008

      Textual Representation of Autonomous System (AS) Numbers

Status of This Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

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Abstract

 A textual representation for Autonomous System (AS) numbers is
 defined as the decimal value of the AS number.  This textual
 representation is to be used by all documents, systems, and user
 interfaces referring to AS numbers.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 2
 2.  Taxonomy of Representation Formats  . . . . . . . . . . . . . . 2
 3.  Representation of AS Number Values  . . . . . . . . . . . . . . 2
 4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 3
 5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 3
 6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 3
 7.  Informative References  . . . . . . . . . . . . . . . . . . . . 3

Huston & Michaelson Standards Track [Page 1]  RFC 5396 ASN Notation December 2008

1. Introduction

 A textual representation for Autonomous System (AS) numbers is
 defined as the decimal value of the AS number.  This textual
 representation is to be used by all documents, systems, and user
 interfaces referring to AS numbers.

 This document notes a number of potential representation formats and
 proposes the adoption of a decimal value notation for AS numbers, or
 "asplain" according to the representation taxonomy described here.

2. Taxonomy of Representation Formats

 A taxonomy of representation for AS numbers is as follows:

 asplain
    refers to a syntax scheme of representing all AS numbers using
    decimal integer notation.  Using asplain notation, an AS number of
    value 65526 would be represented as the string "65526" and an AS
    number of value 65546 would be represented as the string "65546".

 asdot+
    refers to a syntax scheme of representing all AS numbers using a
    notation of two integer values joined by a period character: <high
    order 16-bit value in decimal>.<low order 16-bit value in
    decimal>.  Using asdot+ notation, an AS number of value 65526
    would be represented as the string "0.65526" and an AS number of
    value 65546 would be represented as the string "1.10".

 asdot
    refers to a syntax scheme of representing AS number values less
    than 65536 using asplain notation and representing AS number
    values equal to or greater than 65536 using asdot+ notation.
    Using asdot notation, an AS number of value 65526 would be
    represented as the string "65526" and an AS number of value 65546
    would be represented as the string "1.10".

3. Representation of AS Number Values

 To avoid confusion, a single textual notation is useful for
 documentation, configuration systems, reports, and external tools and
 information repositories.  The decimal value representation, or
 "asplain" is proposed as the textual notation to use for AS numbers.

 The "asplain" representation represents the number as its decimal
 value, without any field delimiter, corresponding to the lack of any
 internal structure required by the use of AS numbers in the inter-
 domain routing context.

Huston & Michaelson Standards Track [Page 2]  RFC 5396 ASN Notation December 2008

4. IANA Considerations

 IANA Registries should use decimal representation ("asplain") for AS
 numbers.

5. Security Considerations

 This document does not refer to matters associated with security of
 routing systems.

6. Acknowledgments

 The terminology of "asplain", "asdot", and "asdot+" was originally
 devised and described by Juergen Kammer in January 2007 [KAMMER2007].

7. Informative References

 [KAMMER2007]  Kammer, J., "AS Number Formats", Jan 2007,
               <http://quagga.ncc.eurodata.de/asnumformat.html>.

Authors' Addresses

 Geoff Huston
 Asia Pacific Network Information Centre

 EMail: gih@apnic.net

 George Michaelson
 Asia Pacific Network Information Centre

 EMail: ggm@apnic.net

Huston & Michaelson Standards Track [Page 3]