< draft-ietf-rtgwg-rlfa-node-protection-11.txt		draft-ietf-rtgwg-rlfa-node-protection-12.txt >
	skipping to change at page 1, line 15 ¶		skipping to change at page 1, line 15 ¶
	Intended status: Standards Track S. Hegde		Intended status: Standards Track S. Hegde
	Expires: July 24, 2017 C. Bowers		Expires: July 24, 2017 C. Bowers
	Juniper Networks, Inc.		Juniper Networks, Inc.
	H. Gredler		H. Gredler
	RtBrick, Inc.		RtBrick, Inc.
	S. Litkowski		S. Litkowski
	Orange		Orange
	January 20, 2017		January 20, 2017
	Remote-LFA Node Protection and Manageability		Remote-LFA Node Protection and Manageability
	draft-ietf-rtgwg-rlfa-node-protection-11		draft-ietf-rtgwg-rlfa-node-protection-12
	Abstract		Abstract
	The loop-free alternates computed following the current Remote-LFA		The loop-free alternates computed following the current Remote-LFA
	specification guarantees only link-protection. The resulting Remote-		specification guarantees only link-protection. The resulting Remote-
	LFA nexthops (also called PQ-nodes), may not guarantee node-		LFA nexthops (also called PQ-nodes), may not guarantee node-
	protection for all destinations being protected by it.		protection for all destinations being protected by it.
	This document describes an extension to the Remote Loop-Free based IP		This document describes procedures for determining if a given PQ-node
	fast reroute mechanisms described in [RFC7490], that describes		provides node-protection for a specific destination or not. The
	procedures for determining if a given PQ-node provides node-		document also shows how the same procedure can be utilized for
	protection for a specific destination or not. The document also		collection of complete characteristics for alternate paths.
	shows how the same procedure can be utilized for collection of		Knowledge about the characteristics of all alternate path is
	complete characteristics for alternate paths. Knowledge about the		precursory to apply operator defined policy for eliminating paths not
	characteristics of all alternate path is precursory to apply operator		fitting constraints.
	defined policy for eliminating paths not fitting constraints.
	Requirements Language		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 RFC2119 [RFC2119].		document are to be interpreted as described in RFC2119 [RFC2119].
	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
	skipping to change at page 3, line 8 ¶		skipping to change at page 3, line 6 ¶
	destinations . . . . . . . . . . . . . . . . . . . . 11		destinations . . . . . . . . . . . . . . . . . . . . 11
	2.3.3. Computing Node-Protecting R-LFA Paths for		2.3.3. Computing Node-Protecting R-LFA Paths for
	Destinations with ECMP primary nexthop nodes . . . . 13		Destinations with ECMP primary nexthop nodes . . . . 13
	2.3.4. Limiting extra computational overhead . . . . . . . . 17		2.3.4. Limiting extra computational overhead . . . . . . . . 17
	3. Manageability of Remote-LFA Alternate Paths . . . . . . . . . 18		3. Manageability of Remote-LFA Alternate Paths . . . . . . . . . 18
	3.1. The Problem . . . . . . . . . . . . . . . . . . . . . . . 18		3.1. The Problem . . . . . . . . . . . . . . . . . . . . . . . 18
	3.2. The Solution . . . . . . . . . . . . . . . . . . . . . . 19		3.2. The Solution . . . . . . . . . . . . . . . . . . . . . . 19
	4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19		4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
	5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19		5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 19		6. Security Considerations . . . . . . . . . . . . . . . . . . . 19
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . 19		7. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
	7.1. Normative References . . . . . . . . . . . . . . . . . . 19		7.1. Normative References . . . . . . . . . . . . . . . . . . 20
	7.2. Informative References . . . . . . . . . . . . . . . . . 20		7.2. Informative References . . . . . . . . . . . . . . . . . 20
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
	1. Introduction		1. Introduction
	The Remote-LFA [RFC7490] specification provides loop-free alternates		The Remote-LFA [RFC7490] specification provides loop-free alternates
	that guarantee only link-protection. The resulting Remote-LFA		that guarantee only link-protection. The resulting Remote-LFA
	alternate nexthops (also referred to as the PQ-nodes) may not provide		alternate nexthops (also referred to as the PQ-nodes) may not provide
	node-protection for all destinations covered by the same, in case of		node-protection for all destinations covered by the same Remote-LFA
	failure of the primary nexthop node. Neither does the specification		alternate, in case of failure of the primary nexthop node. Neither
	provide a means to determine the same.		does the specification provide a means to determine the same.
	Also, the LFA Manageability [RFC7916] document requires a computing		Also, the LFA Manageability [RFC7916] document requires a computing
	router to find all possible (including all possible Remote-LFA)		router to find all possible (including all possible Remote-LFA)
	alternate nexthops, collect the complete set of path characteristics		alternate nexthops, collect the complete set of path characteristics
	for each alternate path, run an alternate-selection policy		for each alternate path, run an alternate-selection policy
	(configured by the operator) and find the best alternate path. This		(configured by the operator) and find the best alternate path. This
	will require the Remote-LFA implementation to gather all the required		will require the Remote-LFA implementation to gather all the required
	path characteristics along each link on the entire Remote-LFA		path characteristics along each link on the entire Remote-LFA
	alternate path.		alternate path.
	skipping to change at page 4, line 4 ¶		skipping to change at page 3, line 50 ¶
	This document describes a procedure for determining node-protection		This document describes a procedure for determining node-protection
	with Remote-LFA. The same procedure is also extended for collection		with Remote-LFA. The same procedure is also extended for collection
	of a complete set of path attributes, enabling more accurate policy-		of a complete set of path attributes, enabling more accurate policy-
	based selection for alternate paths obtained with Remote-LFA.		based selection for alternate paths obtained with Remote-LFA.
	1.1. Abbreviations		1.1. Abbreviations
	This document uses the following list of abbreviations.		This document uses the following list of abbreviations.
	LFA - Loop Free Alternates		LFA - Loop Free Alternates
	RLFA or R-LFA - Remote Loop Free Alternates
			RLFA or R-LFA - Remote Loop Free Alternates
	ECMP - Equal Cost Multiple Path		ECMP - Equal Cost Multiple Path
	SPF - Shortest Path First graph computations		SPF - Shortest Path First graph computations
	NH - Next Hop node		NH - Next Hop node
	2. Node Protection with Remote-LFA		2. Node Protection with Remote-LFA
	Node-protection is required to provide protection of traffic on a		Node-protection is required to provide protection of traffic on a
	given forwarding node, against the failure of the first-hop node on		given forwarding node, against the failure of the first-hop node on
	skipping to change at page 18, line 29 ¶		skipping to change at page 18, line 29 ¶
	Once a subset of PQ-nodes is found, computing router shall run a		Once a subset of PQ-nodes is found, computing router shall run a
	forward SPF on each of the PQ-nodes in the subset to continue with		forward SPF on each of the PQ-nodes in the subset to continue with
	procedures proposed in Section 2.3.2.		procedures proposed in Section 2.3.2.
	3. Manageability of Remote-LFA Alternate Paths		3. Manageability of Remote-LFA Alternate Paths
	3.1. The Problem		3.1. The Problem
	With the regular Remote-LFA [RFC7490] functionality the computing		With the regular Remote-LFA [RFC7490] functionality the computing
	router may compute more than one PQ-node as usable Remote-LFA		router may compute more than one PQ-node as usable Remote-LFA
	alternate nexthops. Additionally an alternate selection policy may		alternate nexthops. Additionally [RFC7916] specifies a LFA (and
	be configured to enable the network operator to choose one of them as		Remote-LFA) manageability framework, in which an alternate selection
	the most appropriate Remote-LFA alternate. For such policy-based		policy may be configured to let the network operator choose one of
	alternate selection to run, all the relevant path characteristics for		them as the most appropriate Remote-LFA alternate. For such policy-
	each the alternate paths (one through each of the PQ-nodes), needs to		based alternate selection to run, the computing router needs to
	be collected. As mentioned before in Section 2.3 the R-LFA alternate		collect all the relevant path characteristics (as specified in
	path through a given PQ-node to a given destination is comprised of		section 6.2.4 of [RFC7916]) for each of the alternate paths (one
	two path segments.		through each of the PQ-nodes). As mentioned before in Section 2.3
			the R-LFA alternate path through a given PQ-node to a given
			destination is comprised of two path segments. Section 6.2.5.4 of
			[RFC7916] specifies that any kind of alternate selection policy must
			consider path characteristics for both path segments while evaluating
			one or more RLFA alternate path(s).
	The first path segment (i.e. from the computing router to the PQ-		The first path segment (i.e. from the computing router to the PQ-
	node) can be calculated from the regular forward SPF done as part of		node) can be calculated from the regular forward SPF done as part of
	standard and remote LFA computations. However without the mechanism		standard and remote LFA computations. However without the mechanism
	proposed in section Section 2.3.2 of this document, there is no way		proposed in Section 2.3.2 of this document, there is no way to
	to determine the path characteristics for the second path segment		determine the path characteristics for the second path segment (i.e.
	(i.e. from the PQ-node to the destination). In the absence of the		from the PQ-node to the destination). In the absence of the path
	path characteristics for the second path segment, two Remote-LFA		characteristics for the second path segment, two Remote-LFA alternate
	alternate paths may be equally preferred based on the first path		paths may be equally preferred based on the first path segments
	segments characteristics only, although the second path segment		characteristics only, although the second path segment attributes may
	attributes may be different.		be different.
	3.2. The Solution		3.2. The Solution
	The additional forward SPF computation proposed in Section 2.3.2		The additional forward SPF computation proposed in Section 2.3.2
	document shall also collect links, nodes and path characteristics		document shall also collect links, nodes and path characteristics
	along the second path segment. This shall enable collection of		along the second path segment. This shall enable collection of
	complete path characteristics for a given Remote-LFA alternate path		complete path characteristics for a given Remote-LFA alternate path
	to a given destination. The complete alternate path characteristics		to a given destination. The complete alternate path characteristics
	shall then facilitate more accurate alternate path selection while		shall then facilitate more accurate alternate path selection while
	running the alternate selection policy.		running the alternate selection policy.
	skipping to change at page 19, line 29 ¶		skipping to change at page 19, line 29 ¶
	subset. The detailed suggestion on how to select this subset is		subset. The detailed suggestion on how to select this subset is
	specified in the same section. While this limits the number of		specified in the same section. While this limits the number of
	possible alternate paths provided to the alternate-selection policy,		possible alternate paths provided to the alternate-selection policy,
	this is needed to keep the computational complexity within affordable		this is needed to keep the computational complexity within affordable
	limits. However if the alternate-selection policy is very		limits. However if the alternate-selection policy is very
	restrictive this may leave few destinations in the entire topology		restrictive this may leave few destinations in the entire topology
	without protection. Yet this limitation provides a necessary		without protection. Yet this limitation provides a necessary
	tradeoff between extensive coverage and immense computational		tradeoff between extensive coverage and immense computational
	overhead.		overhead.
			The mechanism proposed in this section does not modify or invalidate
			[RFC7916] or any parts of it. This document specifies a mechanism to
			meet the requirements specified in section 6.5.2.4 in [RFC7916].
	4. Acknowledgements		4. Acknowledgements
	Many thanks to Bruno Decraene for providing his useful comments. We		Many thanks to Bruno Decraene for providing his useful comments. We
	would also like to thank Uma Chunduri for reviewing this document and		would also like to thank Uma Chunduri for reviewing this document and
	providing valuable feedback. Also, many thanks to Harish Raghuveer		providing valuable feedback. Also, many thanks to Harish Raghuveer
	for his review and comments on the initial versions of this document.		for his review and comments on the initial versions of this document.
	5. IANA Considerations		5. IANA Considerations
	N/A. - No protocol changes are proposed in this document.		N/A. - No protocol changes are proposed in this document.
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