< draft-ietf-trill-multi-topology-05.txt		draft-ietf-trill-multi-topology-06.txt >
	INTERNET-DRAFT Donald Eastlake		INTERNET-DRAFT Donald Eastlake
	Intended status: Proposed Standard Mingui Zhang		Intended status: Proposed Standard Mingui Zhang
	Updates: 6325, 7177 Huawei		Huawei
	Ayan Banerjee		Ayan Banerjee
	Cisco		Cisco
	Expires: May 11, 2018 November 12, 2017		Expires: September 8, 2018 March 9, 2018
	TRILL: Multi-Topology		Transparent Interconnection of Lots of Links (TRILL):
	<draft-ietf-trill-multi-topology-05.txt>		Multi-Topology
			<draft-ietf-trill-multi-topology-06.txt>
	Abstract		Abstract
	This document specifies extensions to the IETF TRILL (Transparent		This document specifies extensions to the IETF TRILL (Transparent
	Interconnection of Lots of Links) protocol to support multi-topology		Interconnection of Lots of Links) protocol to support multi-topology
	routing of unicast and multi-destination traffic based on IS-IS		routing of unicast and multi-destination traffic based on IS-IS
	(Intermediate System to Intermediate System) multi-topology specified		(Intermediate System to Intermediate System) multi-topology specified
	in RFC 5120. This document updates RFC 6325 and RFC 7177.		in RFC 5120.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted to IETF in full conformance with the		This Internet-Draft is submitted to IETF in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Distribution of this document is unlimited. Comments should be sent		Distribution of this document is unlimited. Comments should be sent
	to the TRILL working group mailing list.		to the TRILL working group mailing list.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	skipping to change at page 2, line 12 ¶		skipping to change at page 2, line 12 ¶
	Shadow Directories can be accessed at		Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.		http://www.ietf.org/shadow.html.
	INTERNET-DRAFT TRILL: Multi-Topology		INTERNET-DRAFT TRILL: Multi-Topology
	Table of Contents		Table of Contents
	1. Introduction............................................3		1. Introduction............................................3
	1.1 Terminology............................................4		1.1 Terminology............................................4
	2. Topologies..............................................6		2. Topologies..............................................5
	2.1 Special Topology Zero..................................6		2.1 Special Topology Zero..................................5
	2.2 Links and Multi-Topology...............................6		2.2 Links and Multi-Topology...............................5
	2.3 TRILL Switches and Multi-Topology......................6		2.3 TRILL Switches and Multi-Topology......................5
	2.4 TRILL Data Packets and Multi-Topology..................7		2.4 TRILL Data Packets and Multi-Topology..................6
	2.4.1 Explicit Topology Labeling Support...................7		2.4.1 Explicit Topology Labeling Support...................6
	2.4.2 The Explicit Topology Label..........................8		2.4.2 The Explicit Topology Label..........................7
	2.4.3 TRILL Use of the MT Label............................9		2.4.3 TRILL Use of the MT Label............................8
	3. TRILL Multi-Topology Adjacency and Routing.............11
	3.1 Adjacency (Updates to RFC 7177).......................11
	3.2 TRILL Switch Nicknames................................11
	3.3 TRILL Unicast Routing.................................12
	3.4 TRILL Multi-Destination Routing.......................12
	3.4.1 Distribution Trees..................................12
	3.4.2 Multi-Access Links..................................14
	4. Mixed Links............................................15		3. TRILL Multi-Topology Adjacency and Routing.............10
			3.1 Adjacency.............................................10
			3.2 TRILL Switch Nicknames................................10
			3.3 TRILL Unicast Routing.................................11
			3.4 TRILL Multi-Destination Routing.......................11
			3.4.1 Distribution Trees..................................11
			3.4.2 Multi-Access Links..................................13
	5. Other Multi-Topology Considerations....................16		4. Mixed Links............................................14
	5.1 Address Learning......................................16
	5.1.1 Data Plane Learning.................................16
	5.1.2 Multi-Topology ESADI................................16
	5.2 Legacy Stubs..........................................16
	5.3 RBridge Channel Messages..............................16
	5.4 Implementations Considerations........................17
	6. Allocation Considerations..............................18		5. Other Multi-Topology Considerations....................15
	6.1 IEEE Registration Authority Considerations............18		5.1 Address Learning......................................15
	6.2 IANA Considerations...................................18		5.1.1 Data Plane Learning.................................15
			5.1.2 Multi-Topology ESADI................................15
			5.2 Legacy Stubs..........................................15
			5.3 RBridge Channel Messages..............................15
			5.4 Implementations Considerations........................16
	7. Security Considerations................................19		6. Allocation Considerations..............................17
			6.1 IEEE Registration Authority Considerations............17
			6.2 IANA Considerations...................................17
	Normative References......................................20		7. Security Considerations................................18
	Informative References....................................21
	Acknowledgements..........................................22		Normative References......................................19
			Informative References....................................20
	Appendix A: Differences from RFC 5120.....................23		Acknowledgements..........................................21
			Appendix A: Differences from RFC 5120.....................21
	Authors' Addresses........................................24		Authors' Addresses........................................22
	INTERNET-DRAFT TRILL: Multi-Topology		INTERNET-DRAFT TRILL: Multi-Topology
	1. Introduction		1. Introduction
	This document specifies extensions to the IETF TRILL (Transparent		This document specifies extensions to the IETF TRILL (Transparent
	Interconnection of Lots of Links) protocol [RFC6325] [RFC7177]		Interconnection of Lots of Links) protocol [RFC6325] [RFC7177]
	[RFC7780] to support multi-topology routing for both unicast and		[RFC7780] to support multi-topology routing for both unicast and
	multi-destination traffic based on IS-IS (Intermediate System to		multi-destination traffic based on IS-IS (Intermediate System to
	Intermediate System, [IS-IS]) multi-topology [RFC5120].		Intermediate System, [IS-IS]) multi-topology [RFC5120].
	Implementation and use of multi-topology are optional and use		Implementation and use of multi-topology are optional and use
	requires configuration. It is anticipated that not all TRILL campuses		requires configuration. It is anticipated that not all TRILL
	will need or use multi-topology.		campuses will need or use multi-topology.
	This document updates [RFC7177] as specified in Section 3.1. This
	document updates numerous aspects of [RFC6325] including changing
	routing (Sections 3.3 and 3.4), address learning (Section 5.1), and
	distribution tree construction (Section 3.4), to take multi-topology
	into account.
	Multi-topology creates different topologies or subsets from a single		Multi-topology creates different topologies or subsets from a single
	physical TRILL campus topology. This is different from Data Labels		physical TRILL campus topology. This is different from Data Labels
	(VLANs and Fine Grained Labels [RFC7172]). Data Labels specify		(VLANs and Fine Grained Labels [RFC7172]). Data Labels specify
	communities of end stations and can be viewed as creating virtual		communities of end stations and can be viewed as creating virtual
	topologies of end station connectivity. However, in a single topology		topologies of end station connectivity. However, in a single topology
	TRILL campus, TRILL Data packets can use any part of the physical		TRILL campus, TRILL Data packets can use any part of the physical
	topology of TRILL switches and links between TRILL switches,		topology of TRILL switches and links between TRILL switches,
	regardless of the Data Label of that packet's payload. In a multi-		regardless of the Data Label of that packet's payload. In a multi-
	topology TRILL campus, TRILL data packets in a topology are		topology TRILL campus, TRILL data packets in a topology are
	skipping to change at page 4, line 4 ¶		skipping to change at page 3, line 51 ¶
	multicast or IPv6 islands, routing a class of traffic so that it		multicast or IPv6 islands, routing a class of traffic so that it
	avoids certain TRILL switches that lack some characteristic needed by		avoids certain TRILL switches that lack some characteristic needed by
	that traffic, or making a class of traffic avoid certain links due to		that traffic, or making a class of traffic avoid certain links due to
	security, reliability, or other concerns.		security, reliability, or other concerns.
	It is possible for a particular topology to not be fully connected,		It is possible for a particular topology to not be fully connected,
	either intentionally or due to node or link failures or incorrect		either intentionally or due to node or link failures or incorrect
	configuration. This results in two or more islands of that topology		configuration. This results in two or more islands of that topology
	that cannot communicate. In such a case, end station connected in		that cannot communicate. In such a case, end station connected in
	that topology to different islands will be unable to communicate with		that topology to different islands will be unable to communicate with
	INTERNET-DRAFT TRILL: Multi-Topology
	each other.		each other.
	Multi-topology TRILL supports regions of topology-ignorant TRILL		Multi-topology TRILL supports regions of topology-ignorant TRILL
	switches as part of a multi-topology campus; however, such regions		switches as part of a multi-topology campus; however, such regions
	can only ingress to, egress from, or transit TRILL Data packets in		can only ingress to, egress from, or transit TRILL Data packets in
	the special base topology zero.		the special base topology zero.
			INTERNET-DRAFT TRILL: Multi-Topology
	1.1 Terminology		1.1 Terminology
	The terminology and acronyms of [RFC6325] are used in this document.		The terminology and acronyms of [RFC6325] are used in this document.
	Some of these are listed below for convenience along with some		Some of these are listed below for convenience along with some
	additional terms.		additional terms.
	campus - The name for a TRILL network, like "bridged LAN" is a		campus - The name for a TRILL network, like "bridged LAN" is a
	name for a bridged network. It does not have any academic		name for a bridged network. It does not have any academic
	implication.		implication.
	DRB - Designated RBridge [RFC7177].		DRB - Designated RBridge [RFC7177].
	FGL - Fine-Grained Labeling or Fine-Grained Labeled or Fine-		FGL - Fine-Grained Labeling or Fine-Grained Labeled or Fine-
	Grained Label [RFC7172]. By implication, an "FGL TRILL		Grained Label [RFC7172]. By implication, an "FGL TRILL
	switch" does not support MT.		switch" does not support multi-topology (MT).
	IS - Intermediate System [IS-IS].		IS - Intermediate System [IS-IS].
	LSP - [IS-IS] Link State PDU (Protocol Data Unit). For TRILL this		LSP - [IS-IS] Link State PDU (Protocol Data Unit). For TRILL this
	includes L1-LSPs and E-L1FS-LSPs [RFC7780].		includes L1-LSPs and E-L1FS-LSPs [RFC7780].
	MT - Multi-Topology, this document and [RFC5120].		MT - Multi-Topology, this document and [RFC5120].
	MT TRILL Switch - A TRILL switch supporting the multi-topology		MT TRILL Switch - A TRILL switch supporting the multi-topology
	feature specified in this document. An MT TRILL switch MUST		feature specified in this document. An MT TRILL switch MUST
	skipping to change at page 5, line 5 ¶		skipping to change at page 4, line 47 ¶
	TRILL - Transparent Interconnection of Lots of Links or Tunneled		TRILL - Transparent Interconnection of Lots of Links or Tunneled
	Routing in the Link Layer [RFC6325].		Routing in the Link Layer [RFC6325].
	TRILL Switch - A device implementing the TRILL protocol. TRILL		TRILL Switch - A device implementing the TRILL protocol. TRILL
	switches are [IS-IS] Intermediate Systems (routers).		switches are [IS-IS] Intermediate Systems (routers).
	VL - VLAN Labeling or VLAN Labeled or VLAN Label [RFC7172]. By		VL - VLAN Labeling or VLAN Labeled or VLAN Label [RFC7172]. By
	implication, a "VL RBridge" or "VL TRILL switch" does not		implication, a "VL RBridge" or "VL TRILL switch" does not
	support FGL or MT.		support FGL or MT.
	INTERNET-DRAFT TRILL: Multi-Topology
	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] [RFC8174]
			when, and only when, they appear in all capitals, as shown here.
	INTERNET-DRAFT TRILL: Multi-Topology		INTERNET-DRAFT TRILL: Multi-Topology
	2. Topologies		2. Topologies
	In TRILL multi-topology, a topology is a subset of the TRILL switches		In TRILL multi-topology, a topology is a subset of the TRILL switches
	and of the links between TRILL switches in the TRILL campus. TRILL		and of the links between TRILL switches in the TRILL campus. TRILL
	Data packets are constrained to the subset of switches and links		Data packets are constrained to the subset of switches and links
	corresponding to the packet's topology. TRILL multi-topology is based		corresponding to the packet's topology. TRILL multi-topology is based
	on [RFC5120] IS-IS multi-topology. See Appendix A for differences		on [RFC5120] IS-IS multi-topology. See Appendix A for differences
	skipping to change at page 9, line 18 ¶		skipping to change at page 8, line 18 ¶
	version zero.		version zero.
	R - A 2-bit reserved field that MUST be sent as zero and ignored		R - A 2-bit reserved field that MUST be sent as zero and ignored
	on receipt.		on receipt.
	MT-ID - The 12-bit topology using the topology number space of the		MT-ID - The 12-bit topology using the topology number space of the
	MT TLV [RFC5120].		MT TLV [RFC5120].
	2.4.3 TRILL Use of the MT Label		2.4.3 TRILL Use of the MT Label
	With the addition of the MT label, the four standardized content		With the addition of the version zero MT label, the four standardized
	varieties for the TRILL Data packet data labeling area (the area		content varieties for the TRILL Data packet data labeling area (the
	after the Inner.MacSA (or Flag Word if the Flag Word is present		area after the Inner.MacSA (or Flag Word if the Flag Word is present
	[RFC7780]) and before the payload) are as show below. {PRI, D} is a		[RFC7780]) and before the payload) are as show below. TRILL Data
	3-bit priority and a drop eligibility indicator bit [RFC7780]. All		packets received with any other data labeling are discarded. {PRI,
	MT TRILL switches MUST support FGL, in the sense of being FGL safe		D} is a 3-bit priority and a drop eligibility indicator bit
	[RFC7172], and thus MUST support all four data labeling area contents		[RFC7780].
	shown below.
			All MT TRILL switches MUST support FGL, in the sense of being FGL
			safe [RFC7172], and thus MUST support all four data labeling area
			contents shown below. (This requirement is imposed, rather than
			having FGL support and MT support be independent, to reduce the
			number of variations in RBridges and simplify testing.)
	1. C-VLAN [RFC6325]		1. C-VLAN [RFC6325]
	1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3		1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| C-VLAN = 0x8100 | PRI |D| VLAN ID |		| C-VLAN = 0x8100 | PRI |D| VLAN ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	2. FGL [RFC7172]		2. FGL [RFC7172]
	1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3		1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| FGL = 0x893B | PRI |D| FGL High Part |		| FGL = 0x893B | PRI |D| FGL High Part |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| FGL = 0x893B | PRI |D| FGL Low Part |		| FGL = 0x893B | PRI |D| FGL Low Part |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			INTERNET-DRAFT TRILL: Multi-Topology
	3. MT C-VLAN [this document]		3. MT C-VLAN [this document]
	1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3		1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MT Ethertype = TBD | 0 | R | MT-ID |		| MT Ethertype = TBD | 0 | R | MT-ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| C-VLAN = 0x8100 | PRI |D| VLAN ID |		| C-VLAN = 0x8100 | PRI |D| VLAN ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	INTERNET-DRAFT TRILL: Multi-Topology
	4. MT FGL [this document] [RFC7172]		4. MT FGL [this document] [RFC7172]
	1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3		1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MT Ethertype = TBD | 0 | R | MT-ID |		| MT Ethertype = TBD | 0 | R | MT-ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| FGL = 0x893B | PRI |D| FGL High Part |		| FGL = 0x893B | PRI |D| FGL High Part |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| FGL = 0x893B | PRI |D| FGL Low Part |		| FGL = 0x893B | PRI |D| FGL Low Part |
	skipping to change at page 11, line 10 ¶		skipping to change at page 10, line 10 ¶
	Inclusion or use of S-VLAN or further stacked tags are beyond the		Inclusion or use of S-VLAN or further stacked tags are beyond the
	scope of this document but, as stated in [RFC6325], are obvious		scope of this document but, as stated in [RFC6325], are obvious
	extensions.		extensions.
	INTERNET-DRAFT TRILL: Multi-Topology		INTERNET-DRAFT TRILL: Multi-Topology
	3. TRILL Multi-Topology Adjacency and Routing		3. TRILL Multi-Topology Adjacency and Routing
	Routing calculations in IS-IS are based on adjacency. Section 3.1		Routing calculations in IS-IS are based on adjacency. Section 3.1
	specifies multi-topology updates to the TRILL adjacency specification		specifies multi-topology TRILL adjacency. Section 3.2 describes the
	[RFC7177]. Section 3.2 describes the handling of nicknames.		handling of nicknames. Sections 3.3 and 3.4 specify how unicast and
	Sections 3.3 and 3.4 specify how unicast and multi-destination TRILL		multi-destination TRILL multi-topology routing differ from the TRILL
	multi-topology routing differ from the TRILL base protocol routing.		base protocol routing.
	3.1 Adjacency (Updates to RFC 7177)		3.1 Adjacency
	There is no change in the determination or announcement of adjacency		There is no change in the determination or announcement of adjacency
	for topology zero which is as specified in [RFC7177]. When a		for topology zero which is as specified in [RFC7177]. When a
	topology zero adjacency reaches the Report state as specified in		topology zero adjacency reaches the Report state as specified in
	[RFC7177], the adjacency is announced in core LSPs using the Extended		[RFC7177], the adjacency is announced in core LSPs using the Extended
	Intermediate System Reachability TLV (#22). This will be compatible		Intermediate System Reachability TLV (#22). This will be compatible
	with any legacy topology-ignorant RBridges that might not support E-		with any legacy topology-ignorant RBridges that might not support E-
	L1FS FS-LSPs [RFC7780].		L1FS FS-LSPs [RFC7780].
	Adjacency is announced for non-zero topologies in LSPs using the MT		Adjacency is announced for non-zero topologies in LSPs using the MT
	skipping to change at page 13, line 22 ¶		skipping to change at page 12, line 22 ¶
	consists of disjoint islands, each distribution tree		consists of disjoint islands, each distribution tree
	construction for topology T is local to one such island.		construction for topology T is local to one such island.
	o Only the Nickname sub-TLV, Trees sub-TLV, Tree Identifiers sub-		o Only the Nickname sub-TLV, Trees sub-TLV, Tree Identifiers sub-
	TLV, and Trees Used sub-TLV occurring in an MT Router		TLV, and Trees Used sub-TLV occurring in an MT Router
	Capabilities TLV (#144) specifying topology T are used in		Capabilities TLV (#144) specifying topology T are used in
	determining the tree root(s), if any, for a connected area of		determining the tree root(s), if any, for a connected area of
	non-zero topology T.		non-zero topology T.
	+ There may be non-zero topologies with no multi-destination		+ There may be non-zero topologies with no multi-destination
	traffic or, as descried in [RFC5120], even topologies with		traffic or, as described in [RFC5120], even topologies with
	no traffic at all. For example, if only known destination		no traffic at all. For example, if only known destination
	unicast IPv6 TRILL Data packets were in topology T and all		unicast IPv6 TRILL Data packets were in topology T and all
	multi-destination IPv6 TRILL Data packets were in some other		multi-destination IPv6 TRILL Data packets were in some other
	topology, there would be no need for a distribution tree for		topology, there would be no need for a distribution tree for
	topology T. For this reasons, a Number of Trees to Compute		topology T. For this reason, a Number of Trees to Compute
	of zero in the Trees sub-TLV for the TRILL switch holding		of zero in the Trees sub-TLV for the TRILL switch holding
	the highest priority to be a tree root for a non-zero		the highest priority to be a tree root for a non-zero
	topology T is honored and causes no distribution trees to be		topology T is honored and causes no distribution trees to be
	calculated for non-zero topology T. This is different from		calculated for non-zero topology T. This is different from
	the base topology zero where, as specified in [RFC6325], a		the base topology zero where, as specified in [RFC6325], a
	zero Number of Trees to Compute causes one tree to be		zero Number of Trees to Compute causes one tree to be
	computed.		computed.
	o Nicknames are allocated as described in Section 3.2. If a		o Nicknames are allocated as described in Section 3.2. If a
	TRILL switch advertising that it provides topology T service		TRILL switch advertising that it provides topology T service
	skipping to change at page 21, line 9 ¶		skipping to change at page 20, line 9 ¶
	[RFC7780] - Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A.,		[RFC7780] - Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A.,
	Ghanwani, A., and S. Gupta, "Transparent Interconnection of		Ghanwani, A., and S. Gupta, "Transparent Interconnection of
	Lots of Links (TRILL): Clarifications, Corrections, and		Lots of Links (TRILL): Clarifications, Corrections, and
	Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016,		Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016,
	INTERNET-DRAFT TRILL: Multi-Topology		INTERNET-DRAFT TRILL: Multi-Topology
	<http://www.rfc-editor.org/info/rfc7780>.		<http://www.rfc-editor.org/info/rfc7780>.
			[RFC8174] - Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
			2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May
			2017, <http://www.rfc-editor.org/info/rfc8174>
	Informative References		Informative References
	[RFC8139] - Eastlake 3rd, D., Li, Y., Umair, M., Banerjee, A., and F.		[RFC8139] - Eastlake 3rd, D., Li, Y., Umair, M., Banerjee, A., and F.
	Hu, "Transparent Interconnection of Lots of Links (TRILL):		Hu, "Transparent Interconnection of Lots of Links (TRILL):
	Appointed Forwarders", RFC 8139, DOI 10.17487/RFC8139, June		Appointed Forwarders", RFC 8139, DOI 10.17487/RFC8139, June
	2017, <https://www.rfc-editor.org/info/rfc8139>.		2017, <https://www.rfc-editor.org/info/rfc8139>.
	[RFC7175] - Manral, V., Eastlake 3rd, D., Ward, D., and A. Banerjee,		[RFC7175] - Manral, V., Eastlake 3rd, D., Ward, D., and A. Banerjee,
	"Transparent Interconnection of Lots of Links (TRILL):		"Transparent Interconnection of Lots of Links (TRILL):
	Bidirectional Forwarding Detection (BFD) Support", RFC 7175,		Bidirectional Forwarding Detection (BFD) Support", RFC 7175,
	skipping to change at page 22, line 14 ¶		skipping to change at page 21, line 14 ¶
	INTERNET-DRAFT TRILL: Multi-Topology		INTERNET-DRAFT TRILL: Multi-Topology
	Acknowledgements		Acknowledgements
	The comments and contributions of the following are gratefully		The comments and contributions of the following are gratefully
	acknowledged:		acknowledged:
	Vishwas Manral and Martin Vigoureux		Vishwas Manral and Martin Vigoureux
	The document was prepared in raw nroff. All macros used were defined
	within the source file.
	INTERNET-DRAFT TRILL: Multi-Topology
	Appendix A: Differences from RFC 5120		Appendix A: Differences from RFC 5120
	TRILL multi-topology, as specified in this document, differs from RFC		TRILL multi-topology, as specified in this document, differs from RFC
	5120 as follows:		5120 as follows:
	1. [RFC5120] provides for unicast multi-topology. This document		1. [RFC5120] provides for unicast multi-topology. This document
	extends that to cover multi-destination TRILL data distribution		extends that to cover multi-destination TRILL data distribution
	(see Section 3.4).		(see Section 3.4).
	2. [RFC5120] assumes the topology of data packets is always		2. [RFC5120] assumes the topology of data packets is always
	skipping to change at page 25, line 9 ¶		skipping to change at page 23, line 9 ¶
	Cisco		Cisco
	170 W. Tasman Drive		170 W. Tasman Drive
	San Jose, CA 95134		San Jose, CA 95134
	Email: ayabaner@cisco.com		Email: ayabaner@cisco.com
	INTERNET-DRAFT TRILL: Multi-Topology		INTERNET-DRAFT TRILL: Multi-Topology
	Copyright, Disclaimer, and Additional IPR Provisions		Copyright, Disclaimer, and Additional IPR Provisions
	Copyright (c) 2017 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
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://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
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	76 lines changed or deleted		72 lines changed or added
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