wdiff rfc7447.original rfc7447.txt


Internet Engineering Task Force (IETF)                        J. Scudder
Internet-Draft
Request for Comments: 7447                                   K. Kompella
Updates: 6790 (if approved)                                           Juniper Networks
Intended status:
Category: Standards Track                       December 12, 2014
Expires: June 15,                                   January 2015
ISSN: 2070-1721

         Deprecation of BGP Entropy Label Capability Attribute
             draft-ietf-mpls-deprecate-bgp-entropy-label-02

Abstract

   RFC 6790 defines the

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

Status of This Memo

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   This Internet-Draft will expire on June 15, 2015.
   http://www.rfc-editor.org/info/rfc7447.

Copyright Notice

   Copyright (c) 2014 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   3
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   3
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4

1.  Introduction

   [RFC6790] defines the Entropy Label Capability attribute (ELCA), an
   optional, transitive BGP path attribute.  For correct operation, it
   is necessary that an
   intermediate node modifying the next hop of a route must remove the
   ELCA unless the node so 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 attribute.  By
   definition, a node that does not support the ELCA will propagate the attribute.  (This
   attribute (this is a general property of optional, transitive attributes,
   attributes; see [RFC4271].) [RFC4271]).  But such an ELCA-oblivious node is
   likely to also be incapable of processing entropy label-incapable labels and is exactly
   the
   one 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
   any implementation
   implementations MUST NOT generate the attribute.  If received it received, the
   attribute MUST be treated as any other unrecognized optional 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.)

3.  IANA Considerations

   For the reasons given in Section 1, IANA is requested to mark 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

   ELCA, as defined in [RFC6790] S. 5.2, 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 [RFC6790] S. 5.2 receiving ELCA that receive such "tunneled"
   attributes could -- sometimes improperly -- rely on them.  The
   consequence of so doing so could be a black hole in the forwarding path
   for the affected routes.  Whether or not this is a new security issue
   or not
   is somewhat debatable, since to be exploited an attacker would have to be part of the control plane
   control-plane path for the route in question,
   and under question in order for the
   attacker to exploit the issue.  Under those circumstances 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.  Acknowledgements

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

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. 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. 2012,
              <http://www.rfc-editor.org/info/rfc6790>.

6.2.  Informative References

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

   [RFC4272]  Murphy, S., "BGP Security Vulnerabilities Analysis", RFC
              4272, January 2006. 2006,
              <http://www.rfc-editor.org/info/rfc4272>.

Authors' Addresses

   John G. Scudder
   Juniper Networks

   Email:

   EMail: jgs@juniper.net

   Kireeti Kompella
   Juniper Networks

   Email:

   EMail: kireeti@juniper.net