draft-ietf-rtgwg-multihomed-prefix-lfa-05.txt		draft-ietf-rtgwg-multihomed-prefix-lfa-06.txt
	Routing Area Working Group P. Sarkar, Ed.		Routing Area Working Group P. Sarkar, Ed.
	Internet-Draft Arrcus, Inc.		Internet-Draft Arrcus, Inc.
	Updates: 5286 (if approved) S. Hegde		Updates: 5286 (if approved) S. Hegde
	Intended status: Standards Track Juniper Networks, Inc.		Intended status: Standards Track Juniper Networks, Inc.
	Expires: August 10, 2018 U. Chunduri, Ed.		Expires: August 12, 2018 U. Chunduri, Ed.
	Huawei USA		Huawei USA
	J. Tantsura		J. Tantsura
	Individual		Nuage Networks
	H. Gredler		H. Gredler
	RtBrick, Inc.		RtBrick, Inc.
	February 6, 2018		February 8, 2018
	LFA selection for Multi-Homed Prefixes		LFA selection for Multi-Homed Prefixes
	draft-ietf-rtgwg-multihomed-prefix-lfa-05		draft-ietf-rtgwg-multihomed-prefix-lfa-06
	Abstract		Abstract
	This document shares experience gained from implementing algorithms		This document shares experience gained from implementing algorithms
	to determine Loop-Free Alternates for multi-homed prefixes. In		to determine Loop-Free Alternates for multi-homed prefixes. In
	particular, this document provides explicit inequalities that can be		particular, this document provides explicit inequalities that can be
	used to evaluate neighbors as a potential alternates for multi-homed		used to evaluate neighbors as a potential alternates for multi-homed
	prefixes. It also provides detailed criteria for evaluating		prefixes. It also provides detailed criteria for evaluating
	potential alternates for external prefixes advertised by OSPF ASBRs.		potential alternates for external prefixes advertised by OSPF ASBRs.
	This documents updates and expands some of the "Routing Aspects" as		This documents updates and expands some of the "Routing Aspects" as
	specified in Section 6 of [RFC 5286].		specified in Section 6 of RFC 5286.
	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 2, line 4 ¶		skipping to change at page 2, line 4 ¶
	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-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on August 10, 2018.		This Internet-Draft will expire on August 12, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2018 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
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 10, line 5 ¶		skipping to change at page 10, line 5 ¶
	This document also defines the inequalities defined in [RFC5286]		This document also defines the inequalities defined in [RFC5286]
	specifically for the alternate loop-free ASBR evaluation.		specifically for the alternate loop-free ASBR evaluation.
	4.2.1. Rules to select alternate ASBR		4.2.1. Rules to select alternate ASBR
	The process to select an alternate ASBR is best explained using the		The process to select an alternate ASBR is best explained using the
	rules below. The below process is applied when primary ASBR for the		rules below. The below process is applied when primary ASBR for the
	concerned prefix is chosen and there is an alternate ASBR originating		concerned prefix is chosen and there is an alternate ASBR originating
	same prefix.		same prefix.
	1. If RFC1583Compatibility is disabled		1. If RFC1583Compatibility is disabled
	1a. if primary ASBR and alternate ASBR are intra area		1a. if primary ASBR and alternate ASBR are intra area
	non-backbone path go to step 2.		non-backbone path go to step 2.
	1b. If primary ASBR and alternate ASBR belong to		1b. If primary ASBR and alternate ASBR belong to
	intra-area backbone and/or inter-area path go		intra-area backbone and/or inter-area path go
	to step 2.		to step 2.
	1c. for other paths, skip this alternate ASBR and		1c. for other paths, skip this alternate ASBR and
	consider next ASBR.		consider next ASBR.
	2. If cost type (type1/type2) advertised by alternate		2. If cost type (type1/type2) advertised by alternate
	ASBR same as primary		ASBR same as primary
	2a. If not, same skip alternate ASBR and consider		2a. If not, same skip alternate ASBR and consider next ASBR.
	next ASBR.		2b. If same proceed to step 3.
	2b. If same proceed to step 3.
	3. If cost type is type1		3. If cost type is type1
	3a. If cost is same, program ECMP and return.		3a. If cost is same, program ECMP and return.
	3b. else go to step 5.		3b. else go to step 5.
	4 If cost type is type 2		4 If cost type is type 2
	4a. If cost is different, skip alternate ASBR and		4a. If cost is different, skip alternate ASBR and
	consider next ASBR.		consider next ASBR.
	4b. If type2 cost is same, proceed to step 4c to compare		4b. If type2 cost is same, proceed to step 4c to compare
	compare type 1 cost.		compare type 1 cost.
	4c. If type1 cost is also same program ECMP and return.		4c. If type1 cost is also same program ECMP and return.
	4d. If type 1 cost is different go to step 5.		4d. If type 1 cost is different go to step 5.
	5. If route type (type 5/type 7)		5. If route type (type 5/type 7)
	5a. If route type is same, check route p-bit,		5a. If route type is same, check route p-bit,
	forwarding address field for routes from both		forwarding address field for routes from both
	ASBRs match. If p-bit matches proceed to step 6.		ASBRs match. If p-bit matches proceed to step 6.
	If not, skip this alternate ASBR and consider		If not, skip this alternate ASBR and consider
	next ASBR.		next ASBR.
	5b. If route type is not same, skip this alternate ASBR		5b. If route type is not same, skip this alternate ASBR
	and consider next alternate ASBR.		and consider next alternate ASBR.
	6. Apply inequality on the alternate ASBR.		6. Apply inequality on the alternate ASBR.
	Figure 5: Rules for selecting alternate ASBR in OSPF		Figure 5: Rules for selecting alternate ASBR in OSPF
	4.2.2. Multiple ASBRs belonging different area		4.2.2. Multiple ASBRs belonging different area
	When "RFC1583compatibility" is set to disabled, OSPF [RFC2328]		When "RFC1583compatibility" is set to disabled, OSPF [RFC2328]
	defines certain rules of preference to choose the ASBRs. While		defines certain rules of preference to choose the ASBRs. While
	selecting alternate ASBR for loop evaluation for LFA, these rules		selecting alternate ASBR for loop evaluation for LFA, these rules
	should be applied and ensured that the alternate neighbor does not		should be applied and ensured that the alternate neighbor does not
	loop the traffic back.		loop the traffic back.
	skipping to change at page 17, line 43 ¶		skipping to change at page 17, line 43 ¶
	Uma Chunduri (editor)		Uma Chunduri (editor)
	Huawei USA		Huawei USA
	2330 Central Expressway		2330 Central Expressway
	Santa Clara, CA 95050		Santa Clara, CA 95050
	USA		USA
	Email: uma.chunduri@huawei.com		Email: uma.chunduri@huawei.com
	Jeff Tantsura		Jeff Tantsura
	Individual		Nuage Networks
			755 Ravendale Drive
			Mountain View, CA 94043
			USA
	Email: jefftant.ietf@gmail.com		Email: jefftant.ietf@gmail.com
	Hannes Gredler		Hannes Gredler
	RtBrick, Inc.		RtBrick, Inc.
	Email: hannes@rtbrick.com		Email: hannes@rtbrick.com
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