Trabalho De Rede

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

...