Guidelines for creation, selection, and registration of an Autonomous System (AS)
RFC 1930
Document | Type |
RFC - Best Current Practice
(March 1996; No errata)
Also known as BCP 6
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Authors | John Hawkinson , Tony Bates | ||
Last updated | 2013-03-02 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 1930 (Best Current Practice) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group J. Hawkinson Request for Comments: 1930 BBN Planet BCP: 6 T. Bates Category: Best Current Practice MCI March 1996 Guidelines for creation, selection, and registration of an Autonomous System (AS) Status of this Memo This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited. Abstract This memo discusses when it is appropriate to register and utilize an Autonomous System (AS), and lists criteria for such. ASes are the unit of routing policy in the modern world of exterior routing, and are specifically applicable to protocols like EGP (Exterior Gateway Protocol, now at historical status; see [EGP]), BGP (Border Gateway Protocol, the current de facto standard for inter-AS routing; see [BGP-4]), and IDRP (The OSI Inter-Domain Routing Protocol, which the Internet is expected to adopt when BGP becomes obsolete; see [IDRP]). It should be noted that the IDRP equivalent of an AS is the RDI, or Routing Domain Identifier. Table of Contents 1. Introduction ............................................ 2 2. Motivation .............................................. 2 3. Definitions ............................................. 2 4. Common errors in allocating ASes ........................ 5 5. Criteria for the decision -- do I need an AS? .......... 5 5.1 Sample Cases ........................................... 6 5.2 Other Factors .......................................... 7 6. Speculation ............................................. 7 7. One prefix, one origin AS ............................... 8 8. IGP issues .............................................. 8 9. AS Space exhaustion ..................................... 8 10. Reserved AS Numbers .................................... 9 11. Security Considerations ................................ 9 12. Acknowledgments ........................................ 9 13. References ............................................. 9 14. Authors' Addresses ..................................... 10 Hawkinson & Bates Best Current Practice [Page 1] RFC 1930 Guidelines for creation of an AS March 1996 1. Introduction This memo discusses when it is appropriate to register and utilize an Autonomous System (AS), and lists criteria for such. ASes are the unit of routing policy in the modern world of exterior routing, and are specifically applicable to protocols like EGP (Exterior Gateway Protocol, now at historical status; see [EGP]), BGP (Border Gateway Protocol, the current de facto standard for inter-AS routing; see [BGP-4]), and IDRP (The OSI Inter-Domain Routing Protocol, which the Internet is expected to adopt when BGP becomes obsolete; see [IDRP]). It should be noted that the IDRP equivalent of an AS is the RDI, or Routing Domain Identifier. 2. Motivation This memo is aimed at network operators and service providers who need to understand under what circumstances they should make use of an AS. It is expected that the reader is familiar with routing protocols and will be someone who configures and operates Internet networks. Unfortunately, there is a great deal of confusion in how ASes should be used today; this memo attempts to clear up some of this confusion, as well as acting as a simple guide to today's exterior routing. 3. Definitions This document refers to the term "prefix" throughout. In the current classless Internet (see [CIDR]), a block of class A, B, or C networks may be referred to by merely a prefix and a mask, so long as such a block of networks begins and ends on a power-of-two boundary. For example, the networks: 192.168.0.0/24 192.168.1.0/24 192.168.2.0/24 192.168.3.0/24 can be simply referred to as: 192.168.0.0/22 The term "prefix" as it is used here is equivalent to "CIDR block", and in simple terms may be thought of as a group of one or more networks. We use the term "network" to mean classful network, or "A, B, C network". The definition of AS has been unclear and ambiguous for some time. [BGP-4] states: Hawkinson & Bates Best Current Practice [Page 2] RFC 1930 Guidelines for creation of an AS March 1996 The classic definition of an Autonomous System is a set of routers under a single technical administration, using an interior gateway protocol and common metrics to route packets within the AS, andShow full document text