< draft-ietf-bier-entropy-staged-dc-clos-00.txt		draft-ietf-bier-entropy-staged-dc-clos-01.txt >
	Network Working Group J. Xie		Network Working Group J. Xie
	Internet-Draft Huawei Technologies		Internet-Draft Huawei Technologies
	Intended status: Informational X. Xu		Intended status: Informational X. Xu
	Expires: April 25, 2019 Alibaba Inc.		Expires: November 9, 2019 Alibaba Inc.
	G. Yan		G. Yan
	M. McBride		M. McBride
	Huawei Technologies		Huawei Technologies
	October 22, 2018		May 8, 2019
	Use of BIER Entropy for Data Center CLOS Networks		Use of BIER Entropy for Data Center Clos Networks
	draft-ietf-bier-entropy-staged-dc-clos-00		draft-ietf-bier-entropy-staged-dc-clos-01
	Abstract		Abstract
	Bit Index Explicit Replication (BIER) introduces a new multicast-		Bit Index Explicit Replication (BIER) introduces a new multicast-
	specific BIER Header. BIER can be applied to the Multi Protocol		specific BIER Header. BIER can be applied to the Multi Protocol
	Label Switching (MPLS) data plane or Non-MPLS data plane. Entropy is		Label Switching (MPLS) data plane or Non-MPLS data plane. Entropy is
	a technique used in BIER to support load-balancing. This document		a technique used in BIER to support load-balancing. This document
	examines and describes how BIER Entropy is to be applied to Data		examines and describes how BIER Entropy is to be applied to Data
	Center CLOS networks for path selection.		Center Clos networks for path selection.
	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].		document are to be interpreted as described in [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 1, line 45 ¶		skipping to change at page 1, line 45 ¶
	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 April 25, 2019.		This Internet-Draft will expire on November 9, 2019.
	Copyright Notice		Copyright Notice
	Copyright (c) 2018 IETF Trust and the persons identified as the		Copyright (c) 2019 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
	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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Problem Statement and Considerations . . . . . . . . . . . . 3		3. Problem Statement and Considerations . . . . . . . . . . . . 3
	3.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 3		3.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 3
	3.2. Considerations . . . . . . . . . . . . . . . . . . . . . 4		3.2. Considerations . . . . . . . . . . . . . . . . . . . . . 4
	4. Use of BIER Entropy for DC CLOS Network . . . . . . . . . . . 5		4. Use of BIER Entropy for DC Clos Network . . . . . . . . . . . 5
	4.1. Use of BIER Entropy for DC CLOS Network . . . . . . . . . 5		4.1. Use of BIER Entropy for DC Clos Network . . . . . . . . . 5
	4.2. Steering for elephant flows . . . . . . . . . . . . . . . 6		4.2. Steering for elephant flows . . . . . . . . . . . . . . . 6
	4.3. Path Division for Tenant flows to different SIs . . . . . 6		4.3. Path Division for Tenant flows to different SIs . . . . . 6
	4.4. Link Failure and Convergence . . . . . . . . . . . . . . 6		4.4. Link Failure and Convergence . . . . . . . . . . . . . . 6
	5. Data-Plane Processing . . . . . . . . . . . . . . . . . . . . 7		5. Data-Plane Processing . . . . . . . . . . . . . . . . . . . . 7
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 7		6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
	8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7		8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	9.1. Normative References . . . . . . . . . . . . . . . . . . 7		9.1. Normative References . . . . . . . . . . . . . . . . . . 7
	9.2. Informative References . . . . . . . . . . . . . . . . . 8		9.2. Informative References . . . . . . . . . . . . . . . . . 8
	skipping to change at page 2, line 50 ¶		skipping to change at page 2, line 50 ¶
	1. Introduction		1. Introduction
	Bit Index Explicit Replication (BIER) [RFC8279] is an architecture		Bit Index Explicit Replication (BIER) [RFC8279] is an architecture
	that provides optimal multicast forwarding without requiring		that provides optimal multicast forwarding without requiring
	intermediate routers to maintain any per-flow state by using a		intermediate routers to maintain any per-flow state by using a
	multicast-specific BIER header. [RFC8296] defines two types of BIER		multicast-specific BIER header. [RFC8296] defines two types of BIER
	encapsulation formats: one is MPLS encapsulation, the other is non-		encapsulation formats: one is MPLS encapsulation, the other is non-
	MPLS encapsulation. Entropy is a technique used in BIER to support		MPLS encapsulation. Entropy is a technique used in BIER to support
	load-balancing. This document examines and describes how BIER		load-balancing. This document examines and describes how BIER
	Entropy is to be applied to Data Center CLOS networks for path		Entropy is to be applied to Data Center Clos networks for path
	selection.		selection.
	2. Terminology		2. Terminology
	Readers of this document are assumed to be familiar with the		Readers of this document are assumed to be familiar with the
	terminology and concepts of the documents listed as Normative		terminology and concepts of the documents listed as Normative
	References.		References.
	3. Problem Statement and Considerations		3. Problem Statement and Considerations
	3.1. Problem Statement		3.1. Problem Statement
	A common choice for a horizontally scalable topology used in Data		A common choice for a horizontally scalable topology used in Data
	Center is a CLOS topology. This topology features an odd number of		Center is a Clos topology. This topology features an odd number of
	stages, for example, a 5-Stage CLOS Topology as a example in		stages, for example, a 5-Stage Clos Topology as a example in
	[RFC7938].		[RFC7938].
	ECMP is the fundamental load-sharing mechanism used by a CLOS		ECMP is the fundamental load-sharing mechanism used by a Clos
	topology. Effectively, every lower-tier device will use all of its		topology. Effectively, every lower-tier device will use all of its
	directly attached upper-tier devices to load-share traffic destined		directly attached upper-tier devices to load-share traffic destined
	to the same IP prefix. The number of ECMP paths between any two Tier		to the same IP prefix. The number of ECMP paths between any two Tier
	3 devices in CLOS topology is equal to the number of the devices in		3 devices in Clos topology is equal to the number of the devices in
	the middle stage (Tier 1). For example, Figure 1 illustrates a		the middle stage (Tier 1). For example, Figure 1 illustrates a
	topology where Tier 3 device L1 has four paths to reach servers X and		topology where Tier 3 device L1 has four paths to reach servers X and
	Y, via Tier 2 devices S1 and S2 and then Tier 1 devices S11, S12, S21		Y, via Tier 2 devices S1 and S2 and then Tier 1 devices S11, S12, S21
	and S22 respectively.		and S22 respectively.
	Tier 1		Tier 1
	+-----+		+-----+
	Cluster |SUPER|		Cluster |SUPER|
	+----------------------------+ +--| S11 |--+		+----------------------------+ +--| S11 |--+
	| | | +-----+ |		| | | +-----+ |
	skipping to change at page 4, line 30 ¶		skipping to change at page 4, line 30 ¶
	| | | | | | | | | | | |		| | | | | | | | | | | |
	| +-----+ +-----+ | | +-----+ | +-----+ +-----+		| +-----+ +-----+ | | +-----+ | +-----+ +-----+
	| | LEAF| | LEAF| | +--|SUPER|--+ | LEAF| | LEAF|		| | LEAF| | LEAF| | +--|SUPER|--+ | LEAF| | LEAF|
	| | L1 | | L2 | Tier 3 | | S22 | Tier 3 | L3 | | L4 |		| | L1 | | L2 | Tier 3 | | S22 | Tier 3 | L3 | | L4 |
	| +-----+ +-----+ | +-----+ +-----+ +-----+		| +-----+ +-----+ | +-----+ +-----+ +-----+
	| | | | | | | | | |		| | | | | | | | | |
	| O O O O | X Y O O		| O O O O | X Y O O
	| Servers | Servers		| Servers | Servers
	+----------------------------+		+----------------------------+
	Figure 1: 5-Stage CLOS Topology		Figure 1: 5-Stage Clos Topology
	When BIER is deployed in a multi-tenant data center network		When BIER is deployed in a multi-tenant data center network
	environment for efficient delivery of Broadcast, Unknown-unicast and		environment for efficient delivery of Broadcast, Unknown-unicast and
	Multicast (BUM) traffic, a network operator may want a deterministic		Multicast (BUM) traffic, a network operator may want a deterministic
	path for every packet. For example, when L1 needs to send a BUM		path for every packet. For example, when L1 needs to send a BUM
	packet to L3 and L4, which are in different SIs, L1 has to send the		packet to L3 and L4, which are in different SIs, L1 has to send the
	packet twice, and expects the packet along two deterministic paths of		packet twice, and expects the packet along two deterministic paths of
	L1->S1->S11-->L3 and L1->S2->S21-->L4 seperately. Another example of		L1->S1->S11-->L3 and L1->S2->S21-->L4 seperately. Another example of
	using a deterministic path in a DC is for per-flow steering of		using a deterministic path in a DC is for per-flow steering of
	"elephant" flows defined in [I-D.ietf-spring-segment-routing-msdc].		"elephant" flows defined in [I-D.ietf-spring-segment-routing-msdc].
	skipping to change at page 5, line 19 ¶		skipping to change at page 5, line 19 ¶
	If one wants, however, to get a deterministic path from the equal		If one wants, however, to get a deterministic path from the equal
	cost paths, one can use part of the 20-bit entropy field. For		cost paths, one can use part of the 20-bit entropy field. For
	example, bit 0 to bit 2 of entropy label can represent a value of 0		example, bit 0 to bit 2 of entropy label can represent a value of 0
	to 7, and thus can be used to select a deterministic path from 8		to 7, and thus can be used to select a deterministic path from 8
	equal cost paths. And thus, a 20-bit entropy label can be used by		equal cost paths. And thus, a 20-bit entropy label can be used by
	routers in different tiers to select a deterministic path		routers in different tiers to select a deterministic path
	independently by using different parts of the 20-bit entropy label,		independently by using different parts of the 20-bit entropy label,
	and form an end-to-end deterministic path.		and form an end-to-end deterministic path.
	This is simple and applicable especially for DC CLOS networks,		This is simple and applicable especially for DC Clos networks,
	because data delivery in DC CLOS networks for tenants is always		because data delivery in DC Clos networks for tenants is always
	multi-staged, with the upstream direction stages having equal cost		multi-staged, with the upstream direction stages having equal cost
	paths.		paths.
	4. Use of BIER Entropy for DC CLOS Network		4. Use of BIER Entropy for DC Clos Network
	4.1. Use of BIER Entropy for DC CLOS Network		4.1. Use of BIER Entropy for DC Clos Network
	Take the 5-stage CLOS network in figure 1 as an example.		Take the 5-stage Clos network in figure 1 as an example.
	Tier 2 in every cluster has N nodes, and the Tier 1 has M nodes. M		Tier 2 in every cluster has N nodes, and the Tier 1 has M nodes. M
	is equal to N multiplied by P.		is equal to N multiplied by P.
	Tier 3 switches, in upstream direction, act as stage 1 of data		Tier 3 switches, in upstream direction, act as stage 1 of data
	delivery and have N equal cost paths to every BFERs in other		delivery and have N equal cost paths to every BFERs in other
	clusters. Tier 2 switches, in upstream direction, act as stage 2 of		clusters. Tier 2 switches, in upstream direction, act as stage 2 of
	data delivery and have P equal cost paths to every BFERs in other		data delivery and have P equal cost paths to every BFERs in other
	clusters.		clusters.
	skipping to change at page 7, line 50 ¶		skipping to change at page 7, line 50 ¶
	[I-D.ietf-mpls-spring-entropy-label]		[I-D.ietf-mpls-spring-entropy-label]
	Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,		Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
	Shakir, R., and J. Tantsura, "Entropy label for SPRING		Shakir, R., and J. Tantsura, "Entropy label for SPRING
	tunnels", draft-ietf-mpls-spring-entropy-label-12 (work in		tunnels", draft-ietf-mpls-spring-entropy-label-12 (work in
	progress), July 2018.		progress), July 2018.
	[I-D.ietf-spring-segment-routing-msdc]		[I-D.ietf-spring-segment-routing-msdc]
	Filsfils, C., Previdi, S., Dawra, G., Aries, E., and P.		Filsfils, C., Previdi, S., Dawra, G., Aries, E., and P.
	Lapukhov, "BGP-Prefix Segment in large-scale data		Lapukhov, "BGP-Prefix Segment in large-scale data
	centers", draft-ietf-spring-segment-routing-msdc-10 (work		centers", draft-ietf-spring-segment-routing-msdc-11 (work
	in progress), October 2018.		in progress), November 2018.
	[RFC7938] Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of		[RFC7938] Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of
	BGP for Routing in Large-Scale Data Centers", RFC 7938,		BGP for Routing in Large-Scale Data Centers", RFC 7938,
	DOI 10.17487/RFC7938, August 2016,		DOI 10.17487/RFC7938, August 2016,
	<https://www.rfc-editor.org/info/rfc7938>.		<https://www.rfc-editor.org/info/rfc7938>.
	[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,		[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
	Przygienda, T., and S. Aldrin, "Multicast Using Bit Index		Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
	Explicit Replication (BIER)", RFC 8279,		Explicit Replication (BIER)", RFC 8279,
	DOI 10.17487/RFC8279, November 2017,		DOI 10.17487/RFC8279, November 2017,
End of changes. 17 change blocks.
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