draft-ietf-mpls-spl-terminology-03.txt		draft-ietf-mpls-spl-terminology-04.txt
	MPLS Working Group L. Andersson		MPLS Working Group L. Andersson
	Internet-Draft Bronze Dragon Consulting		Internet-Draft Bronze Dragon Consulting
	Updates: 3032, 7274 (if approved) K. Kompella		Updates: 3032, 7274 (if approved) K. Kompella
	Intended status: Informational Juniper Networks		Intended status: Standards Track Juniper Networks
	Expires: February 13, 2021 A. Farrel		Expires: March 28, 2021 A. Farrel
	Old Dog Consulting		Old Dog Consulting
	August 12, 2020		September 24, 2020
	Special Purpose Label terminology		Special Purpose Label terminology
	draft-ietf-mpls-spl-terminology-03		draft-ietf-mpls-spl-terminology-04
	Abstract		Abstract
	This document discusses and recommends a terminology that may be used		This document discusses and recommends a terminology that may be used
	when MPLS Special Purpose Labels (SPL) are specified and documented.		when MPLS Special Purpose Labels (SPL) are specified and documented.
			This document applies that terminology change to the relevant IANA
			registry and also clarifies the use of the Entropy Label Indicator
			(7) when immediately preceded by the Extension Label (15).
	This document updates RFC 7274 and RFC 3032.		This document updates RFC 7274 and RFC 3032.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
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	This Internet-Draft will expire on February 13, 2021.		This Internet-Draft will expire on March 28, 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2020 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://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
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 2		1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
			2. Background . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2.1. GMPLS Special Purpose Labels . . . . . . . . . . . . . . 3		2.1. GMPLS Special Purpose Labels . . . . . . . . . . . . . . 3
	3. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3		3. Terminology and Abbreviations . . . . . . . . . . . . . . . . 3
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 4		4. Clarification on Use of Entropy Label Indicator . . . . . . . 5
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5		5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
	7.1. Normative References . . . . . . . . . . . . . . . . . . 5		8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6
	7.2. Informative References . . . . . . . . . . . . . . . . . 5		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6		9.1. Normative References . . . . . . . . . . . . . . . . . . 7
			9.2. Informative References . . . . . . . . . . . . . . . . . 7
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
	1. Introduction		1. Introduction
	RFC 7274 [RFC7274] made some changes to the terminology used for MPLS		RFC 7274 [RFC7274] made some changes to the terminology used for MPLS
	Special Purpose Labels, but did not define consistent terminology.		Special Purpose Labels, but did not define consistent terminology.
	One thing that RFC 7274 did was to deprecate use of the term		One thing that RFC 7274 did was to deprecate use of the term
	"reserved labels" when describing a range of labels allocated from a		"reserved labels" when describing a range of labels allocated from a
	registry maintained by IANA. The term "Reserved" in such a registry		registry maintained by IANA. The term "Reserved" in such a registry
	means "set aside, not to be used", but that range of labels was		means "set aside, not to be used", but that range of labels was
	skipping to change at page 2, line 44 ¶		skipping to change at page 3, line 5 ¶
	At the time of writing the first version of this document, the IETF		At the time of writing the first version of this document, the IETF
	was in the process of allocating the very first SPLs from the		was in the process of allocating the very first SPLs from the
	Extended SPL (eSPL) range [RFC8595]. This document discusses and		Extended SPL (eSPL) range [RFC8595]. This document discusses and
	recommends terminology and abbreviations to be used when talking		recommends terminology and abbreviations to be used when talking
	about and documenting Special Purpose Labels.		about and documenting Special Purpose Labels.
	This document updates RFC 3032 [RFC3032] and RFC 7274 [RFC7274] in		This document updates RFC 3032 [RFC3032] and RFC 7274 [RFC7274] in
	that it changes the terminology for both Base SPLs and Extended SPLs.		that it changes the terminology for both Base SPLs and Extended SPLs.
			This document applies that terminology change to the relevant IANA
			registry and also clarifies the use of the Entropy Label Indicator
			(7) when immediately preceded by the Extension Label (15).
			1.1. Terminology
			The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
			"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
			"OPTIONAL" in this document are to be interpreted as described in BCP
			14 [RFC2119] [RFC8174] when, and only when, they appear in all
			capitals, as shown here.
	2. Background		2. Background
	Two sets of SPLs are defined for use in MPLS:		Two sets of SPLs are defined for use in MPLS:
	The range of 0-15, Base Special Purpose Labels (bSPLs), is		The range of 0-15, Base Special Purpose Labels (bSPLs), is
	specified in RFC 3032 [RFC3032].		specified in RFC 3032 [RFC3032].
	The range 0-1048575 of eSPLs is specified in RFC 7274 [RFC7274].		The range 0-1048575 of eSPLs is specified in RFC 7274 [RFC7274].
	* the values 0-15 have been reserved never to be allocated		* the values 0-15 have been reserved never to be allocated
	skipping to change at page 3, line 39 ¶		skipping to change at page 4, line 12 ¶
	'Special-Purpose MPLS Label Values' registry [bSPL]. The other is		'Special-Purpose MPLS Label Values' registry [bSPL]. The other is
	called 'Extended Special-Purpose MPLS Label Values' registry [eSPL].		called 'Extended Special-Purpose MPLS Label Values' registry [eSPL].
	The difference in the name of the name space and the first registry		The difference in the name of the name space and the first registry
	is only that the MPLS abbreviation is expanded. This document		is only that the MPLS abbreviation is expanded. This document
	changes the name of the first registry to 'Base Special-Purpose MPLS		changes the name of the first registry to 'Base Special-Purpose MPLS
	Label Values', but leaves the name of the latter registry unchanged		Label Values', but leaves the name of the latter registry unchanged
	as 'Extended Special-Purpose MPLS Label Values'.		as 'Extended Special-Purpose MPLS Label Values'.
	The following conventions will be used in specifications and when		The following conventions will be used in specifications and when
	talking about SPLs		talking about SPLs.
	o Collectively, the two ranges are known as Special Purpose Labels
	(SPL).
	o The special purpose labels from the lower range will be called		o Collectively, the two (unrelated) ranges (0-15 and 16-1048575) are
	Base Special Purpose Labels (bSPL).		known as Special Purpose Labels (SPL).
	o The special purpose labels from the higher range will be called		o Special purpose labels from the range 0-15 are called Base Special
	Extended Special Purpose Labels (eSPL).		Purpose Labels (bSPL).
	o The combination of the Extension Label (XL) (value 15 which is a		o Special purpose labels from the range 16-1048575 are called
	bSPL, but that is also called xSPL) and an eSPL is called a		Extended Special Purpose Labels (eSPL). (Note that the reserved
	Composite Special Purpose Label (cSPL).		values 0-15 from the 'Extended Special-Purpose MPLS Label Values'
			registry do not need a name as they are not available for
			allocation and MUST NOT be used.)
	This results in a label stacks such as the illustrative examples		This results in a label stacks such as the illustrative examples
	shown in Figure 1 and Figure 2.		shown in Figure 1 and Figure 2.
	0 31		0 31
	| MPLS Label Stack entry |		| MPLS Label Stack entry |
	+--------+--------+--------+--------+		+--------+--------+--------+--------+
	| MPLS Label Stack entry |		| MPLS Label Stack entry |
	+--------+--------+--------+--------+		+--------+--------+--------+--------+
	bSPL | Base SPL |		bSPL | Base SPL |
	skipping to change at page 4, line 32 ¶		skipping to change at page 5, line 18 ¶
	| MPLS Label Stack entry |		| MPLS Label Stack entry |
	+--------+--------+--------+--------+		+--------+--------+--------+--------+
	xSPL | Extension Label (XL) | <--+		xSPL | Extension Label (XL) | <--+
	+--------+--------+--------+--------+ |--- cSPL		+--------+--------+--------+--------+ |--- cSPL
	eSPL | Extended SPL | <--+		eSPL | Extended SPL | <--+
	+--------+--------+--------+--------+		+--------+--------+--------+--------+
	| MPLS Label Stack entry (cont.) |		| MPLS Label Stack entry (cont.) |
	Figure 2: Example of Label Stack		Figure 2: Example of Label Stack
	4. Security Considerations		4. Clarification on Use of Entropy Label Indicator
			Section 3.1 of [RFC7274] contains two paragraphs that describe the
			use of the Entropy Label Indicator (label 7). These paragraphs have
			introduced some confusion about whether the Entropy Label Indicator
			can be present when immediately preceded by the Extension Label.
			This document updates [RFC7274] by replacing those paragraphs as
			follows.
			OLD
			Values 0-15 of the "Extended Special-Purpose MPLS Label Values"
			registry are set aside as reserved. Furthermore, values 0-6 and
			8-15 MUST NOT appear in the data plane following an XL; an LSR
			processing a packet with an XL at the top of the label stack
			followed by a label with value 0-6 or 8-15 MUST drop the packet.
			Label 7 (when received) retains its meaning as Entropy Label
			Indicator (ELI) whether a regular special-purpose label or an
			ESPL; this is because of backwards compatibility with existing
			implemented and deployed code and hardware that looks for the ELI
			without verifying if the previous label is XL or not. However,
			when an LSR inserts an entropy label, it MUST insert the ELI as a
			regular special-purpose label, not as an ESPL.
			NEW
			Values 0-15 of the "Extended Special-Purpose MPLS Label Values"
			registry are set aside as reserved. Furthermore, an
			implementation MUST NOT place a label with value 0-15 in the label
			stack immediately following an XL; an LSR processing a packet with
			an XL at the top of the label stack immediately followed by a
			label with value 0-15 MUST drop the packet.
			When inspecting a label stack to find an Entropy Label Indicator
			(ELI - label 7) a pre-existing implementation may fail to inspect
			the previous label, and so not notice that it is an XL. Such
			systems can continue to process the entropy information and
			forward the packet when the previous label is an XP without
			causing harm. However, the packet will be dropped when the XL
			reaches the top of the stack at another LSR.
			END
			5. Security Considerations
	The document describes the terminology to be used when describing and		The document describes the terminology to be used when describing and
	specifying the use of SPLs. It does not effect the forwarding in the		specifying the use of SPLs. It does not effect the forwarding in the
	MPLS data plane, nor does it have any effect on how LSPs are		MPLS data plane, nor does it have any effect on how LSPs are
	established by an MPLS control plane or by a centralized controller.		established by an MPLS control plane or by a centralized controller.
	This document does not aim to describe existing implementations of		This document does not aim to describe existing implementations of
	SPLs or potential vulnerabilities of SPLs.		SPLs or potential vulnerabilities of SPLs.
	5. IANA Considerations		6. IANA Considerations
	We request that the name of the IANA registry that today is called		IANA is requested to change the name of the registry that today is
	"Special-Purpose MPLS Label Values" is changed to "Base Special-		called "Special-Purpose MPLS Label Values" is changed to "Base
	Purpose MPLS Label Values".		Special- Purpose MPLS Label Values".
	6. Acknowledgements		7. Acknowledgements
	The authors of this document would like to thank Stewart Bryant for		We like to thank the Routing Directorate reviwer Eric Gray for a
	careful review and constructive suggestions.		detailed, careful and insightful review, and Tom Petch for pointing
			out several issues of clarity.
	We would also like to thank the Routing Directorate reviwer Eric Gray		8. Contributors
	for a detailed, careful and insightful review.
	7. References		The following people contributed text to this document:
	7.1. Normative References		Stewart Bryant
			Futurewei Technologies Inc.
			Email: stewart.bryant@gmail.com
			Figure 3
			9. References
			9.1. Normative References
	[bSPL] "Special-Purpose MPLS Label Values",		[bSPL] "Special-Purpose MPLS Label Values",
	<https://www.iana.org/assignments/mpls-label-values/mpls-		<https://www.iana.org/assignments/mpls-label-values/mpls-
	label-values.xhtml#special-purpose/>.		label-values.xhtml#special-purpose/>.
	[eSPL] "Extended Special-Purpose MPLS Label Values",		[eSPL] "Extended Special-Purpose MPLS Label Values",
	<https://www.iana.org/assignments/mpls-label-values/mpls-		<https://www.iana.org/assignments/mpls-label-values/mpls-
	label-values.xhtml#extended/>.		label-values.xhtml#extended/>.
			[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
			Requirement Levels", BCP 14, RFC 2119,
			DOI 10.17487/RFC2119, March 1997,
			<https://www.rfc-editor.org/info/rfc2119>.
	[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,		[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
	Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack		Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
	Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,		Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
	<https://www.rfc-editor.org/info/rfc3032>.		<https://www.rfc-editor.org/info/rfc3032>.
	[RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating		[RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating
	and Retiring Special-Purpose MPLS Labels", RFC 7274,		and Retiring Special-Purpose MPLS Labels", RFC 7274,
	DOI 10.17487/RFC7274, June 2014,		DOI 10.17487/RFC7274, June 2014,
	<https://www.rfc-editor.org/info/rfc7274>.		<https://www.rfc-editor.org/info/rfc7274>.
			[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
			2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
			May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	[SPL-NAME-SPACE]		[SPL-NAME-SPACE]
	"Special-Purpose Multiprotocol Label Switching (MPLS)		"Special-Purpose Multiprotocol Label Switching (MPLS)
	Label Values", <https://www.iana.org/assignments/mpls-		Label Values", <https://www.iana.org/assignments/mpls-
	label-values/mpls-label-values.xhtml/>.		label-values/mpls-label-values.xhtml/>.
	7.2. Informative References		9.2. Informative References
	[RFC8595] Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based		[RFC8595] Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based
	Forwarding Plane for Service Function Chaining", RFC 8595,		Forwarding Plane for Service Function Chaining", RFC 8595,
	DOI 10.17487/RFC8595, June 2019,		DOI 10.17487/RFC8595, June 2019,
	<https://www.rfc-editor.org/info/rfc8595>.		<https://www.rfc-editor.org/info/rfc8595>.
	Authors' Addresses		Authors' Addresses
	Loa Andersson		Loa Andersson
	Bronze Dragon Consulting		Bronze Dragon Consulting
	Email: loa@pi.nu		Email: loa@pi.nu
	Kireeti Kompella		Kireeti Kompella
	Juniper Networks		Juniper Networks
	Email: kireeti@juniper.net		Email: kireeti@juniper.net
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