Network Working Group G. Michaelson Internet-Draft APNIC Intended status: Informational October 15, 2006 Expires: April 18, 2007 Canonical Textual Representation of 4-byte AS Numbers draft-michaelson-4byte-as-representation-02 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. This Internet-Draft will expire on April 18, 2007. Copyright Notice Copyright (C) The Internet Society (2006). Michaelson Expires April 18, 2007 [Page 1] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 Abstract A single textual representation for 4-byte Autonomous System (AS) numbers is defined, to avoid any confusion in interpreting the two 2-byte quantities of which it is comprised. The syntax chosen avoids collision with Border Gateway Protocol (BGP) community string parsing of AS numbers. It is recommended that only this textual representation be used by all documents and systems referring to 4-byte AS numbers. Michaelson Expires April 18, 2007 [Page 2] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 1. Nomenclature 4 Byte AS numbers are defined in [IDR4BYTES] 4-byte AS numbers are represented 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 represented as the string "1.10". Michaelson Expires April 18, 2007 [Page 3] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 2. 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) Michaelson Expires April 18, 2007 [Page 4] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 3. Discussion To avoid confusion, a single textual notation to represent a 4-byte AS number is defined. This is for use in documentation, configuration systems, and external tools and information repositories. 2-byte only AS numbers MAY be represented as a 16 bit value decimal number, with no leading zeros, or ".". They may also be represented as 4-byte AS numbers. 4-byte AS numbers MAY be represented identically as 2-byte only AS numbers, if their value lies in the range 0 - 65535. Otherwise, they MUST be represented identically as for 4-byte only AS numbers. For values in the range 0 - 65535 the canonical 4-byte AS number representation is 0. < 16 bit decimal value > . all other 4-byte AS numbers take a non-zero value in the high order 16 bit decimal value. 4-byte only AS numbers MUST be represented as two pairs of 16-bit decimal values with no leading zeros, separated by the "." character. The first decimal value is the high-order 16 bits, the second decimal value is the low order 16 bits. During the transitional period, when not all systems understand 4 byte AS numbers, it may be neccessary to continue to use two notations to represent the 16-bit values which represent the AS numbers 0 - 65535. These 2 byte AS numbers need a canonical textual representation in 4-byte AS number representation. Once all systems are converted to using 4-byte AS numbers, only 4 byte AS number representation should be used. Michaelson Expires April 18, 2007 [Page 5] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 4. Historical Approaches 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. Routing Protocol Specification Language (RPSL) [RFC2622] [RFC4012] AS-Set objects use the ":" character to denote sequences of AS objects forming a chain. Since the AS object would have had the ":" character embedded in the instance name, this would have required double-parsing to find 4-byte AS number in AS-Set chains. 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 Regional Internet Registry (RIR) community towards the deployment of 4-byte AS numbers. Therefore it seems sensible to formalize its use as the preferred representation of a 4-byte AS numbers across the board. Michaelson Expires April 18, 2007 [Page 6] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 5. IANA Considerations This document recommends changes to an existing IANA Registry, the as number assignments registry. This document makes changes to the IANA Considerations text in [IDR4BYTES] as follows: It is recommended that upon approval of this document, the IANA will change the rules for representation of the assignments in the "AUTONOMOUS SYSTEM NUMBERS" registry located at http://www.iana.org/assignments/as-numbers New line in the registry will be: 1.0 - 65535.65535 Reserved by the IANA maintained subsequently in the documented textual representation as assignments are made to the RIR. Michaelson Expires April 18, 2007 [Page 7] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 6. Acknowledgements This proposal was motivated by a discussion with Geoff Huston. The text of the definition of a 4-byte AS is taken from [RIPE2005-12] The author thanks Rudiger Volk, Joao Damas, Joe Abley, Peter Koch and Henk Uijterwaal for feedback and extensive comments on this draft. Michaelson Expires April 18, 2007 [Page 8] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 7. Implementation Notes Many programming languages 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 arithmetical calculation. Care must be taken that 4-byte AS numbers 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. The [RFC2622] and [RFC4012] specifications, and systems which manipulate AS numbers need to be reviewed for conformance with 4-byte AS number textual representation, and for the syntactic implications of this representation. Michaelson Expires April 18, 2007 [Page 9] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 8. Changes since the -01 draft An IANA Considerations section has been added to amend an existing registry. The document now clarifies that it refers to a textual representation, the binary representation used on-the-wire is unaffected by this draft. Michaelson Expires April 18, 2007 [Page 10] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 9. Informative References [IDR4BYTES] Vohra, Q. and E. Chen, "draft-ietf-idr-as4bytes-12", Dec 2005, . [RFC2622] Alaettinoglu, C., Villamizar, C., Gerich, E., Kessens, D., Meyer, D., Bates, T., Karrenberg, D., and M. Terpstra, "Routing Policy Specification Language (RPSL)", RFC 2622, June 1999. [RFC4012] Blunk, L., Damas, J., Parent, F., and A. Robachevsky, "Routing Policy Specification Language next generation (RPSLng)", RFC 4012, March 2005. [RIPE2005-12] Huston, G., "4-Byte AS Number Policy", Dec 2005, < http://www.ripe.net/ripe/policies/proposals/2005-12.html>. Michaelson Expires April 18, 2007 [Page 11] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 Author's Address George Michaelson Asia Pacific Network Information Centre Level 1, 33 Park Road Milton, Queensland 4064 AU Phone: +61 7 3858 3100 Email: ggm@apnic.net Michaelson Expires April 18, 2007 [Page 12] Internet-Draft Canonical Textual Form of 4-byte ASN October 2006 Full Copyright Statement 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. 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