Reservation of Last Autonomous System (AS) Numbers
draft-ietf-idr-last-as-reservation-02

The information below is for an old version of the document
Document Type Active Internet-Draft (idr WG)
Last updated 2014-03-04 (latest revision 2014-02-06)
Stream IETF
Intended RFC status Proposed Standard
Formats plain text pdf html bibtex
Stream WG state WG Consensus: Waiting for Write-Up
Document shepherd Susan Hares
IESG IESG state I-D Exists
Consensus Boilerplate Yes
Telechat date
Responsible AD (None)
Send notices to (None)
IDR                                                              J. Haas
Internet-Draft                                          Juniper Networks
Intended status: Informational                               J. Mitchell
Expires: August 10, 2014                           Microsoft Corporation
                                                        February 6, 2014

           Reservation of Last Autonomous System (AS) Numbers
                 draft-ietf-idr-last-as-reservation-02

Abstract

   This document reserves two Autonomous System numbers (ASNs) at the
   end of the 16 bit and 32 bit ranges, described in this document as
   "Last ASNs" and provides guidance to implementers and operators on
   their use.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on August 10, 2014.

Copyright Notice

   Copyright (c) 2014 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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Haas & Mitchell          Expires August 10, 2014                [Page 1]
Internet-Draft             Last AS Reservation             February 2014

1.  Introduction

   IANA has reserved the last Autonomous System Number (ASN), 65535, of
   the 16 bit autonomous system number range for over a decade with the
   intention that it not be used by network operators running BGP
   [RFC4271].  Since the introduction of BGP Support for Four-Octet AS
   Number Space [RFC6793], IANA has also reserved the last ASN of the 32
   bit autonomous system number range, 4294967295.  This reservation has
   been documented in the IANA Autonomous System Numbers Registry
   [IANA.AS].  Although these "Last ASNs" border on Private Use ASN
   [RFC6996] ranges, they are not defined or reserved as Private Use
   ASNs by [IANA.AS].  This document describes the reasoning for
   reserving these Last ASNs and provides guidance both to operators and
   to implementers on their use.

2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  Reasons for Last ASNs Reservation

   A subset of the BGP communities of ASN 65535, the last ASN of the 16
   bit range, are reserved for use by Well-known communities as
   described in [RFC1997] and [IANA.WK].  Although this is not currently
   true of ASN 4294967295, if there is a future need for another Special
   Use ASN that is not designed to be globally routable, or the
   associated BGP communities of such an ASN, ASN 4294967295 could be a
   valid candidate for such purpose.  This document does not prescribe
   any such Special Use to this ASN at the time of publication.

4.  Operational Considerations

   Operators SHOULD NOT use these Last ASNs as if they are Private Use
   ASNs or for any other purpose.  Operational use of these Last ASNs
   could have undesirable results.  For example; use of AS 65535 as if
   it were a Private Use ASN, may result in inadvertent use of BGP Well-
   known Community values [IANA.WK], causing undesireable routing
   behavior.

   These last ASNs MUST NOT be advertised to the global Internet within
   AS_PATH or AS4_PATH attributes.  Operators that choose to do
   filtering of Private Use ASNs within the AS_PATH and AS4_PATH
   attributes SHOULD also filter these Last ASNs.

Haas & Mitchell          Expires August 10, 2014                [Page 2]
Internet-Draft             Last AS Reservation             February 2014

5.  Implementation Considerations

   While these Last ASNs are reserved, they remain valid ASNs from a BGP
   protocol perspective.  Therefore, implementations of BGP [RFC4271]
   SHOULD NOT treat the use of these Last ASNs as any type of protocol
   error.  However, implementations MAY generate a local warning message
Show full document text