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.
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	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.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
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	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
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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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