idr W. Kumari
Internet-Draft Google
Updates: 4271 (if approved) R. Bush
Intended status: Standards Track Internet Initiative Japan
Expires: February 25, 2013 H. Schiller
K. Patel
Cisco Systems
August 26, 2012

Codification of AS 0 processing.


This document updates RFC 4271 and proscribes the use of Autonomous System (AS) 0 in the Border Gateway Protocol (BGP) OPEN and AS_PATH / AS4_PATH BGP attribute.

Status of This Memo

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

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This Internet-Draft will expire on February 25, 2013.

Copyright Notice

Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.

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Table of Contents

1. Introduction

Autonomous System 0 is listed in the IANA Autonomous System Number Registry as "Reserved - May be use to identify non-routed networks" ([IANA.AS_Numbers]).

[RFC6491] specifies that AS number zero in a Route Origin Attestation (ROA) is used to mark a prefix and all its more specific prefixes as not to be used in a routing context. This allows a resource holder to signal that a prefix (and the more specifics) should not be routed by publishing a ROA listing AS0 as the only origin. To respond to this signal requres that BGP implementations do not accept or propagate routes containing AS0.

No clear statement that AS 0 was proscribed could be found in any BGP specification. This document corrects this omission, most importantly in the case of the AS_PATH. This represents an update to the error handling procedures given in [RFC4271] Sections 6.2 and 6.3 by specifying the behavior in the presence of AS0.

At least two implementations discard routes containing AS 0, and this document codifies this behavior.

1.1. Requirements notation

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 [RFC2119].

2. Behavior

A BGP speaker MUST NOT originate or propagate a route with an AS number of zero in the AS_PATH, AS4_PATH, AGGREGATOR or AS4_AGGREGATOR attributes.

An UPDATE message that contains the AS number of zero in the AS_PATH or AGGREGATOR attribute MUST be considered as malformed, and be handled by the procedures specified in [I-D.ietf-idr-error-handling].

An UPDATE message that contains the AS number of zero in the AS4_PATH or AS4_AGGREGATOR attribute MUST be considered as malformed, and be handled by the procedures specified in [I-D.ietf-idr-rfc4893bis].

If a BGP speaker receives zero as the peer AS in an OPEN message, it MUST abort the connection and send a NOTIFICATION with Error Code "OPEN Message Error" and subcode "Bad Peer AS" (see [RFC4271] Section 6.2). A router MUST NOT initiate a connection claiming to be AS number zero.

Authors of future protocol extensions that carry the Autonomous System number are encouraged to keep in mind that AS number zero is reserved and to provide clear direction on how to handle AS number zero.

3. IANA Considerations

The IANA is requested to update the Reference for number 0 in the "Autonomous System (AS) Numbers" registry to reference this document.

4. Security Considerations

By allowing a Resource Public Key Infrastructure (RPKI) resource holder to issue a ROA saying that AS 0 is the only valid origin for a route, we allow them to state that a particular address resource is not in use. By ensuring that all implementations that see AS 0 in a route ignore that route, we prevent a malicious party from announcing routes containing AS 0 in an attempt to hijack those resources.

In addition, by standardizing the behavior upon reception of an AS_PATH (or AS4_PATH) containing AS 0, this document makes the behavior better defined.

5. Acknowledgements

The authors wish to thank Elwyn Davies, Enke Chen, Brian Dickson, Bruno Decraene, Robert Raszuk, Jakob Heitz, Danny McPherson, Chris Morrow, iLya, John Scudder, Jeff Tantsura, Daniel Ginsburg and Susan Hares. Apologies to those we may have missed, it was not intentional.

6. References

6.1. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4271] Rekhter, Y., Li, T. and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006.
[I-D.ietf-idr-error-handling] Scudder, J, Chen, E, Mohapatra, P and K Patel, "Revised Error Handling for BGP UPDATE Messages", Internet-Draft draft-ietf-idr-error-handling-01, December 2011.
[I-D.ietf-idr-rfc4893bis] Vohra, Q and E Chen, "BGP Support for Four-octet AS Number Space", Internet-Draft draft-ietf-idr-rfc4893bis-06, April 2012.
[IANA.AS_Numbers] IANA, "Autonomous System (AS) Numbers", .

6.2. Informative References

[RFC6491] Manderson, T., Vegoda, L. and S. Kent, "Resource Public Key Infrastructure (RPKI) Objects Issued by IANA", RFC 6491, February 2012.

Appendix A. Changes / Author Notes.

[RFC Editor: Please remove this section before publication ]

Draft accepted as IDR Doc, notes reset. Please see notes for draft-wkumari-idr-as0.xml for prior comments.

Changes -00.

Changes -01

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Authors' Addresses

Warren Kumari Google 1600 Amphitheatre Parkway Mountain View, CA, 94043 US EMail:
Randy Bush Internet Initiative Japan 5147 Crystal Springs Bainbridge Island, WA, 98110 US EMail:
Heather Schiller Verizon 22001 Loudoun County Parkway Ashburn, 20147 US EMail:
Keyur Patel Cisco Systems 170 W. Tasman Drive San Jose, CA 95134 USA EMail: