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-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Proposed canonical 4-byte AS representation 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. Michaelson ^L[Page 1] INTERNET DRAFT July 2006 Nomenclature 4 Byte AS numbers are defined in [1]. It is proposed that 4-byte AS Numbers are represented using a syntax of .. Accordingly, a 4-byte AS Number of value 65546 (decimal) would be represented as the string "1.10". 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) Discussion To avoid confusion, a single notation to represent a 4-byte AS value is required. This is for use in documentation, configuration systems, and external tools and information repositories. Initially, the ":" was proposed to separate the 2-byte components. However this clashes with use of the ":" character in community attribute syntax in BGP and this would have required changes to the routing systems code base in ways which are not acceptable. It is believed that the ":" character would also interfere with the parsing of RPSL objects. This also is not acceptable. The "." denoted representation does not present these problems. 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 across the board. 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]. The author thanks Rüdiger Volk and Joao Damas for feedback and comments on this draft. Michaelson ^L[Page 2] INTERNET DRAFT July 2006 Security Considerations Many systems treat xxx.yyy numeric strings as real number values on input, and convert internally to a canonical floating point representation. Since the precision cannot be guaranteed to be preserved, this risks changing the value of the 32-bit quantity on output, or by mis-placed mathematical calculation. Care must be taken that 4-byte AS are treated as special-purpose strings on input and output, and parsed correctly to a 32 bit quantity. It would be sensible to draft suitable function definitions to define the transform from presentation to internal value, as was done for IPv4 and IPv6 addresses with the inet_pton() and inet_ntop() functions. RPSL needs to be reviewed for conformance with 4-byte AS deployment, and for the syntactic implications of this representation. Author's Address: George Michaelson APNIC Level 1, 33 Park Road, Milton, Q4064 Australia 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 Comments & Feedback Comments are solicited and should be addressed to the working group's mailing list at idr@ietf.org and/or the author. Authors email address ggm@apnic.net Copyright Declaration Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights." "This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR Michaelson ^L[Page 3] INTERNET DRAFT July 2006 IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Michaelson ^L[Page 4]