Textual Representation of Autonomous System (AS) Numbers
A single decimal notation for writing Autonomous System numbers.
Huston, G. and G. Michaelson, "Textual Representation of Autonomous System (AS) Numbers", RFC 5396, DOI 10.17487/RFC5396, December 2008, <https://www.rfc-editor.org/info/rfc5396>.
@misc{rfc5396,
series = {Request for Comments},
number = 5396,
howpublished = {RFC 5396},
publisher = {RFC Editor},
doi = {10.17487/RFC5396},
url = {https://www.rfc-editor.org/info/rfc5396},
author = {G. Huston and G. Michaelson},
title = {{Textual Representation of Autonomous System (AS) Numbers}},
pagetotal = 3,
year = 2008,
month = dec,
} RFC text
Contents
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.
Copyright Notice
Copyright (c) 2008 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 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 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
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.
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
ISO Plain Language
On this page
§1Why Choose One Textual Form
The RFC proposes decimal notation for Autonomous System numbers in documents, systems, and user interfaces. It calls this form asplain.
The document notes other formats in use: asdot+ splits the number into two decimal values joined by a period, while asdot uses plain notation below 65536 and asdot+ for larger values.
One number can be written in several ways. The RFC proposes one consistent form to avoid confusion.
§2Three Representation Formats
asplain writes every AS number as a decimal integer, such as 65546. asdot+ writes two decimal components separated by a period, such as 1.10. asdot uses asplain below 65536 and asdot+ for values equal to or above 65536.
The RFC proposes asplain because it presents the AS number as a single value without field delimiters.
Asplain is one continuous decimal number. The other notations add a period and divide the number into parts.
§3The Proposed Standard Representation
The document proposes asplain for documentation, configuration systems, reports, external tools, and information repositories. It says IANA registries should use decimal representation.
The security section says the document does not address security matters associated with routing systems.
The RFC recommends writing AS numbers as decimal values in registries and other text. It does not define a routing security mechanism.