GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc7447

Internet Engineering Task Force (IETF) J. Scudder Request for Comments: 7447 K. Kompella Updates: 6790 Juniper Networks Category: Standards Track February 2015 ISSN: 2070-1721

       Deprecation of BGP Entropy Label Capability Attribute

Abstract

 The BGP Entropy Label Capability attribute is defined in RFC 6790.
 Regrettably, it has a bug: although RFC 6790 mandates that routers
 incapable of processing Entropy Labels must remove the attribute,
 fulfillment of this requirement cannot be guaranteed in practice.
 This specification deprecates the attribute.  A forthcoming document
 will propose a replacement.

Status of This Memo

 This is an Internet Standards Track document.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It represents the consensus of the IETF community.  It has
 received public review and has been approved for publication by the
 Internet Engineering Steering Group (IESG).  Further information on
 Internet Standards is available in Section 2 of RFC 5741.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7447.

Copyright Notice

 Copyright (c) 2015 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.

Scudder & Kompella Standards Track [Page 1] RFC 7447 Deprecation of ELCA February 2015

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
 2.  Deprecation of ELCA . . . . . . . . . . . . . . . . . . . . .   2
 3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
 4.  Security Considerations . . . . . . . . . . . . . . . . . . .   3
 5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   5.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
   5.2.  Informative References  . . . . . . . . . . . . . . . . .   3
 Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   4
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1. Introduction

 [RFC6790] defines the Entropy Label Capability attribute (ELCA), an
 optional, transitive BGP path attribute.  For correct operation, an
 intermediate node modifying the next hop of a route must remove the
 ELCA unless the node doing so is able to process entropy labels.
 Sadly, this requirement cannot be fulfilled with the ELCA as
 specified, because it is an optional, transitive attribute.  By
 definition, a node that does not support the ELCA will propagate the
 attribute (this is a general property of optional, transitive
 attributes; see [RFC4271]).  But such an ELCA-oblivious node is
 likely to be incapable of processing entropy labels and is exactly
 the node that we desire to remove the attribute!
 This specification updates RFC 6790 by deprecating the version of
 ELCA defined in Section 5.2 of that document.  A forthcoming document
 will propose a replacement.  All other sections of RFC 6790 are
 unchanged.

1.1. 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].

2. Deprecation of ELCA

 This document deprecates the ELCA path attribute.  This means that
 implementations MUST NOT generate the attribute.  If received, the
 attribute MUST be treated as any other unrecognized optional,
 transitive attribute as per [RFC4271], until and unless the code
 point is reused by some new specification.  (To the authors' best
 knowledge, there are no implementations of ELCA at the time of
 writing.)

Scudder & Kompella Standards Track [Page 2] RFC 7447 Deprecation of ELCA February 2015

3. IANA Considerations

 For the reasons given in Section 1, IANA has marked attribute 28 "BGP
 Entropy Label Capability Attribute" in the "BGP Path Attributes"
 registry as "deprecated" and has added a reference to this RFC.

4. Security Considerations

 ELCA, as defined in Section 5.2 of [RFC6790], has in common with
 other optional, transitive path attributes the property that it will
 be "tunneled" through intervening routers that don't implement the
 relevant specification.  Unfortunately, as discussed elsewhere in
 this document, implementations of ELCA that receive such "tunneled"
 attributes could -- sometimes improperly -- rely on them.  The
 consequence of doing so could be a black hole in the forwarding path
 for the affected routes.  Whether or not this is a new security issue
 is somewhat debatable, since an attacker would have to be part of the
 control-plane path for the route in question in order for the
 attacker to exploit the issue.  Under those circumstances, an
 attacker already has a panoply of mischief-making tools available, as
 discussed in [RFC4272].
 In any case, this document renders any real or imagined security
 issues with ELCA moot, by deprecating it.

5. References

5.1. Normative References

 [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997,
            <http://www.rfc-editor.org/info/rfc2119>.
 [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
            L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
            RFC 6790, November 2012,
            <http://www.rfc-editor.org/info/rfc6790>.

5.2. Informative References

 [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
            Border Gateway Protocol 4 (BGP-4)", RFC 4271, January
            2006, <http://www.rfc-editor.org/info/rfc4271>.
 [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis", RFC
            4272, January 2006,
            <http://www.rfc-editor.org/info/rfc4272>.

Scudder & Kompella Standards Track [Page 3] RFC 7447 Deprecation of ELCA February 2015

Acknowledgements

 Thanks to Alia Atlas, Bruno Decraene, Martin Djernaes, John Drake,
 Adrian Farrel, Keyur Patel, Ravi Singh, and Kevin Wang for their
 discussion of this issue.

Authors' Addresses

 John G. Scudder
 Juniper Networks
 EMail: jgs@juniper.net
 Kireeti Kompella
 Juniper Networks
 EMail: kireeti@juniper.net

Scudder & Kompella Standards Track [Page 4]

/data/webs/external/dokuwiki/data/pages/rfc/rfc7447.txt · Last modified: 2015/02/03 05:33 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki