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Network Working Group                                          G. HustonRequest for Comments: 5396                                 G. MichaelsonCategory: Standards Track                                          APNIC                                                           December 2008Textual Representation of Autonomous System (AS) NumbersStatus 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.Copyright Notice   Copyright (c) 2008 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document.   Please review these documents carefully, as they describe your rights   and restrictions with respect to this document.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 Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .22.  Taxonomy of Representation Formats  . . . . . . . . . . . . . .23.  Representation of AS Number Values  . . . . . . . . . . . . . .24.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .35.  Security Considerations . . . . . . . . . . . . . . . . . . . .36.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . .37.  Informative References  . . . . . . . . . . . . . . . . . . . .3Huston & Michaelson         Standards Track                     [Page 1]

RFC 5396                      ASN Notation                 December 20081.  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 20084.  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.netHuston & Michaelson         Standards Track                     [Page 3]