draft-ietf-mpls-deprecate-bgp-entropy-label-02.txt   rfc7447.txt 
Internet Engineering Task Force J. Scudder Internet Engineering Task Force (IETF) J. Scudder
Internet-Draft K. Kompella Request for Comments: 7447 K. Kompella
Updates: 6790 (if approved) Juniper Networks Updates: 6790 Juniper Networks
Intended status: Standards Track December 12, 2014 Category: Standards Track February 2015
Expires: June 15, 2015 ISSN: 2070-1721
Deprecation of BGP Entropy Label Capability Attribute Deprecation of BGP Entropy Label Capability Attribute
draft-ietf-mpls-deprecate-bgp-entropy-label-02
Abstract Abstract
RFC 6790 defines the BGP Entropy Label Capability attribute. The BGP Entropy Label Capability attribute is defined in RFC 6790.
Regrettably, it has a bug: although RFC 6790 mandates that Entropy Regrettably, it has a bug: although RFC 6790 mandates that routers
Label-incapable routers must remove the attribute, in practice this incapable of processing Entropy Labels must remove the attribute,
requirement can't be guaranteed to be fulfilled. This specification fulfillment of this requirement cannot be guaranteed in practice.
deprecates the attribute. A forthcoming document will propose a This specification deprecates the attribute. A forthcoming document
replacement. will propose a replacement.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
This Internet-Draft will expire on June 15, 2015. 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 Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
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 1. Introduction
[RFC6790] defines the Entropy Label Capability attribute (ELCA), an [RFC6790] defines the Entropy Label Capability attribute (ELCA), an
optional, transitive BGP path attribute. For correct operation, it optional, transitive BGP path attribute. For correct operation, an
is necessary that an intermediate node modifying the next hop of a intermediate node modifying the next hop of a route must remove the
route must remove the ELCA unless the node so doing is able to ELCA unless the node doing so is able to process entropy labels.
process entropy labels. Sadly, this requirement cannot be fulfilled Sadly, this requirement cannot be fulfilled with the ELCA as
with the ELCA as specified, because it is an optional, transitive specified, because it is an optional, transitive attribute. By
attribute: by definition, a node that does not support the ELCA will definition, a node that does not support the ELCA will propagate the
propagate the attribute. (This is a general property of optional, attribute (this is a general property of optional, transitive
transitive attributes, see [RFC4271].) But such an ELCA-oblivious attributes; see [RFC4271]). But such an ELCA-oblivious node is
node is likely to also be entropy label-incapable and is exactly the likely to be incapable of processing entropy labels and is exactly
one that we desire to remove the attribute! the node that we desire to remove the attribute!
This specification updates RFC 6790 by deprecating the version of This specification updates RFC 6790 by deprecating the version of
ELCA defined in Section 5.2 of that document. A forthcoming document ELCA defined in Section 5.2 of that document. A forthcoming document
will propose a replacement. All other sections of RFC 6790 are will propose a replacement. All other sections of RFC 6790 are
unchanged. unchanged.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. Deprecation of ELCA 2. Deprecation of ELCA
This document deprecates the ELCA path attribute. This means that This document deprecates the ELCA path attribute. This means that
any implementation MUST NOT generate the attribute. If received it implementations MUST NOT generate the attribute. If received, the
MUST be treated as any other unrecognized optional transitive attribute MUST be treated as any other unrecognized optional,
attribute as per [RFC4271], until and unless the code point is reused transitive attribute as per [RFC4271], until and unless the code
by some new specification. (To the authors' best knowledge, there point is reused by some new specification. (To the authors' best
are no implementations of ELCA at the time of writing.) knowledge, there are no implementations of ELCA at the time of
writing.)
3. IANA Considerations 3. IANA Considerations
For the reasons given in Section 1, IANA is requested to mark For the reasons given in Section 1, IANA has marked attribute 28 "BGP
attribute 28 in the "BGP Path Attributes" registry as "deprecated" Entropy Label Capability Attribute" in the "BGP Path Attributes"
and reference this RFC. registry as "deprecated" and has added a reference to this RFC.
4. Security Considerations 4. Security Considerations
ELCA as defined in [RFC6790] S. 5.2, has in common with other ELCA, as defined in Section 5.2 of [RFC6790], has in common with
optional, transitive path attributes the property that it will be other optional, transitive path attributes the property that it will
"tunneled" through intervening routers that don't implement the be "tunneled" through intervening routers that don't implement the
relevant specification. Unfortunately, as discussed elsewhere in relevant specification. Unfortunately, as discussed elsewhere in
this document, implementations of [RFC6790] S. 5.2 receiving such this document, implementations of ELCA that receive such "tunneled"
"tunneled" attributes could -- sometimes improperly -- rely on them. attributes could -- sometimes improperly -- rely on them. The
The consequence of so doing could be a black hole in the forwarding consequence of doing so could be a black hole in the forwarding path
path for the affected routes. Whether this is a new security issue 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 is somewhat debatable, since an attacker would have to be part of the
have to be part of the control plane path for the route in question, control-plane path for the route in question in order for the
and under those circumstances an attacker already has a panoply of attacker to exploit the issue. Under those circumstances, an
mischief-making tools available, as discussed in [RFC4272]. 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 In any case, this document renders any real or imagined security
issues with ELCA moot, by deprecating it. issues with ELCA moot, by deprecating it.
5. Acknowledgements 5. References
Thanks to Alia Atlas, Bruno Decraene, Martin Djernaes, John Drake,
Adrian Farrell, Keyur Patel, Ravi Singh and Kevin Wang for their
discussion of this issue.
6. References
6.1. Normative References 5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. 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 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding", L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, November 2012. RFC 6790, November 2012,
<http://www.rfc-editor.org/info/rfc6790>.
6.2. Informative References 5.2. Informative References
[RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Protocol 4 (BGP-4)", RFC 4271, January 2006. 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 [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", RFC
4272, January 2006. 4272, January 2006,
<http://www.rfc-editor.org/info/rfc4272>.
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 Authors' Addresses
John G. Scudder John G. Scudder
Juniper Networks Juniper Networks
Email: jgs@juniper.net EMail: jgs@juniper.net
Kireeti Kompella Kireeti Kompella
Juniper Networks Juniper Networks
Email: kireeti@juniper.net EMail: kireeti@juniper.net
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