< draft-ietf-lsr-ospf-prefix-originator-01.txt		draft-ietf-lsr-ospf-prefix-originator-02.txt >
	LSR Working Group A. Wang		LSR Working Group A. Wang
	Internet-Draft China Telecom		Internet-Draft China Telecom
	Intended status: Standards Track A. Lindem		Intended status: Standards Track A. Lindem
	Expires: January 2, 2020 Cisco Systems		Expires: February 26, 2020 Cisco Systems
	J. Dong		J. Dong
	Huawei Technologies		Huawei Technologies
	K. Talaulikar		K. Talaulikar
	P. Psenak		P. Psenak
	Cisco Systems		Cisco Systems
	July 1, 2019		August 25, 2019
	OSPF Extension for Prefix Originator		OSPF Extension for Prefix Originator
	draft-ietf-lsr-ospf-prefix-originator-01		draft-ietf-lsr-ospf-prefix-originator-02
	Abstract		Abstract
	This document describes OSPFv2 and OSPFv3 encodings to advertise the		This document describes Open Shortest Path First (OSPF) v2 and OSPFv3
	router-id of the originator of inter-area prefixes for OSPFv2 and		encodings to advertise the router-id of the originator of inter-area
	OSPFv3 LSAs, which are needed in several use cases in multi-area OSPF		prefixes for OSPFv2 and OSPFv3 Link-State Advertisement (LSA), which
	use cases.		are needed in several use cases in multi-area OSPF use cases.
	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-
	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 January 2, 2020.		This Internet-Draft will expire on February 26, 2020.
	Copyright Notice		Copyright Notice
	Copyright (c) 2019 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.
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	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
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	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. Conventions used in this document . . . . . . . . . . . . . . 3		2. Conventions used in this document . . . . . . . . . . . . . . 3
	3. Scenario Description . . . . . . . . . . . . . . . . . . . . 3		3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
	4. Prefix Source Router-ID sub-TLV . . . . . . . . . . . . . . . 4		4. Conventions used in this document . . . . . . . . . . . . . . 4
	5. Extended LSA Elements of Procedure . . . . . . . . . . . . . 5		5. Scenario Description . . . . . . . . . . . . . . . . . . . . 4
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 5		6. Prefix Source Router-ID sub-TLV . . . . . . . . . . . . . . . 5
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6		7. Extended LSA Elements of Procedure . . . . . . . . . . . . . 6
	8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6		8. Security Considerations . . . . . . . . . . . . . . . . . . . 6
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6		9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
	9.1. Normative References . . . . . . . . . . . . . . . . . . 6		10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7
	9.2. Informative References . . . . . . . . . . . . . . . . . 7		11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
	Appendix A. Inter-Area Topology Retrieval Process . . . . . . . 7		11.1. Normative References . . . . . . . . . . . . . . . . . . 7
			11.2. Informative References . . . . . . . . . . . . . . . . . 8
			Appendix A. Inter-Area Topology Retrieval Process . . . . . . . 8
	Appendix B. Special Considerations on Inter-Area Topology		Appendix B. Special Considerations on Inter-Area Topology
	Retrieval . . . . . . . . . . . . . . . . . . . . . 8		Retrieval . . . . . . . . . . . . . . . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
	1. Introduction		1. Introduction
	[I-D.ietf-ospf-mpls-elc] defines mechanisms to signal Entropy Label		[I-D.ietf-ospf-mpls-elc] defines mechanisms to Entropy Readable Label
	Capability (ELC) and Entropy Readable Label Depth (ERLD) for ingress		Depth (ERLD) for ingress Label Switching Router (LSR) to discover
	LSR to discover each LSR's capability of reading the maximum label		each LSR's capability of performing Entropy Label (EL) -based load-
	stack depth and performing EL-based load-balancing in MPLS networks.		balancing in Multi Protocol Label Switch (MPLS) networks. The
	The ingress LSR can use this information to push the appropriate		ingress LSR can use this information to push the appropriate label
	label stack for specific FEC trafffic, especially in segment routing		stack for specific traffic, especially in segment routing
	environments and other stacked LSPs scenarios.		environments and other stacked LSPs scenarios.
	However, in inter-area scenarios, the Area Border Router (ABR) does		However, in inter-area scenarios, the Area Border Router (ABR) does
	not advertise the originating OSPF router-id for inter-area prefixes.		not advertise the originating OSPF router-id for inter-area prefixes.
	An OSPF router in one area doesn't know where the prefixes really		An OSPF router in one area doesn't know where the prefixes really
	came from and can't determine the router that originated inter-area		came from and can't determine the router that originated inter-area
	prefixes and then can't judge the ELC and ERLD capabilities of the		prefixes and then can't judge the ERLD capabilities of the
	destination. It is necessary to transfer the originator information		destination. It is necessary to transfer the originator information
	of these inter-area prefixes to ensure the ingress LSR constructs the		of these inter-area prefixes to ensure the ingress LSR constructs the
	right Label stack.		right Label stack.
	More generally, draft [I-D.ietf-ospf-segment-routing-msd] defines a		More generally, draft [RFC8476] defines a mechanism to advertise
	mechanism to advertise multiple types of supported Maximum SID Depths		multiple types of supported Maximum SID Depths (MSD) at node and/or
	(MSD) at node and/or link granularity. This information will be		link granularity. This information will be referred when the head-
	referred when the head-end router starts to send traffic to		end router starts to send traffic to destination prefixes. In inter-
	destination prefixes. In inter-area scenario, it is also necessary		area scenario, it is also necessary for the sender to learn the
	for the sender to learn the capabilities of the receivers associated		capabilities of the receivers associated with the inter-area
	with the inter-area prefixes.		prefixes.
	There is also another scenario where knowing the originator of inter-		There is also another scenario where knowing the originator of inter-
	area prefixes is useful. For example, BGP-LS [RFC7752] describes		area prefixes is useful. For example, Border Gateway Protocol Link-
	mechanisms using the BGP protocol to advertise Link-State		State (BGP-LS) [RFC7752] describes mechanisms using the BGP protocol
	information. This can enable an SDN controller to collect the		to advertise Link-State information. This can enable an Soft
	underlay network topology automatically.		Definition Network (SDN) controller to collect the underlay network
			topology automatically.
	But if the underlay network is divided into multiple areas and		But if the underlay network is divided into multiple areas and
	running the OSPF protocol, it is not easy for the SDN controller to		running the OSPF protocol, it is not easy for the SDN controller to
	rebuild the multi-area topology, because normally an Area Border		rebuild the multi-area topology, because normally an ABR that
	Router (ABR) that connects multiple areas will hide the detailed		connects multiple areas will hide the detailed topology information
	topology information for these non-backbone areas, and the router in		for these non-backbone areas. If only the router in backbone area
	backbone area that runs the BGP-LS protocol can only learn and report		runs the BGP-LS protocol, it just learn and report the summary
	the summary network information from the non-backbone areas. If the		network information from the non-backbone areas. If the SDN
	SDN controller can learn the originator of the inter-area prefixes,		controller can learn the originator of the inter-area prefixes, it is
	it is possible for them to rebuild the inter-area topology		possible for them to rebuild the inter-area topology automatically.
	automatically.
	[RFC7794] introduces the IS-IS "IPv4/IPv6 Source Router IDs" TLV to		[RFC7794] introduces the Intermediate System to Intermediate System
			(IS-IS) "IPv4/IPv6 Source Router IDs" Type-Length-Value (TLV) to
	advertise the source of the prefixes redistributed from a different		advertise the source of the prefixes redistributed from a different
	IS-IS level. This TLV can be used in the above scenarios. Such		IS-IS level. This TLV can be used in the above scenarios. Such
	solution can also be applied in networks that run the OSPF protocol,		solution can also be applied in networks that run the OSPF protocol,
	but the related Link state Advertisements (LSAs) must be extended.		but the related LSAs TLV must be extended.
	This draft provides such solution for the OSPFv2 and OSPFv3		This draft provides such solution for the OSPFv2 and OSPFv3
	protocols.		protocols.
	2. Conventions used in this document		2. Conventions used in this document
	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] .
	3. Scenario Description		3. Terminology
	Fig.1 illustrates the topology scenario when OSPF is running in		The following terms are used in this document:
			o ABR: Area Border Router
			o ERLD: Entropy Readable Label Depth
			o EL: Entropy Label
			o IS-IS: Intermediate System to Intermediate System
			o LSA: Link-State Advertisement
			o MSD: Maximum SID Depths
			o OSPF: Open Shortest Path First
			o SID: Segment IDentifier
			4. Conventions used in this document
			The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
			"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
			document are to be interpreted as described in [RFC2119] .
			5. Scenario Description
			Figure 1 illustrates the topology scenario when OSPF is running in
	multi-area. R0-R4 are routers in backbone area, S1-S4,T1-T4 are		multi-area. R0-R4 are routers in backbone area, S1-S4,T1-T4 are
	internal routers in area 1 and area 2 respectively. R1 and R3 are		internal routers in area 1 and area 2 respectively. R1 and R3 are
	area border routers between area 0 and area 1. R2 and R4 are area		area border routers between area 0 and area 1. R2 and R4 are area
	border routers between area 0 and area 2. N1 is the network between		border routers between area 0 and area 2. N1 is the network between
	router S1 and S2 and N2 is the network between router T1 and T2. Ls1		router S1 and S2 and N2 is the network between router T1 and T2. Ls1
	is the loopback address of Node S1 and Lt1 is the loopback address of		is the loopback address of Node S1 and Lt1 is the loopback address of
	Node T1.		Node T1.
	+-----------------+		+-----------------+
	|IP SDN Controller|		|IP SDN Controller|
	skipping to change at page 4, line 25 ¶		skipping to change at page 4, line 51 ¶
	| | | | | || | |		| | | | | || | |
	| | | | | || | |		| | | | | || | |
	| +-++ +-++ ++-+ +-++ ++++ +-++|		| +-++ +-++ ++-+ +-++ ++++ +-++|
	| |S4+--------+S3+---+R3+-----------+R4+---+T3+--------+T4||		| |S4+--------+S3+---+R3+-----------+R4+---+T3+--------+T4||
	| +--+ +--+ ++-+ +-++ ++-+ +--+|		| +--+ +--+ ++-+ +-++ ++-+ +--+|
	| | | |		| | | |
	| | | |		| | | |
	| Area 1 | Area 0 | Area 2 |		| Area 1 | Area 0 | Area 2 |
	+---------------------+---------------+--------------------+		+---------------------+---------------+--------------------+
	Fig.1 OSPF Inter-Area Prefix Originator Scenario		Figure 1: OSPF Inter-Area Prefix Originator Scenario
	If S1 wants to send traffic to prefix Lt1 that is connected T1 in		If S1 wants to send traffic to prefix Lt1 that is connected T1 in
	another area, it should know the ELC, ERLD, and MSD values that are		another area, it should know the ERLD, and MSD values that are
	associated with the node T1, and then construct the right label stack		associated with the node T1, and then construct the right label stack
	at the ingress node for the target traffic.		at the ingress node for the target traffic.
	In another scenario, If R0 has some method to learn the originator of		In another scenario, If R0 has some method to learn the originator of
	network N1 and reports such information to IP SDN controller, then it		network N1 and reports such information to IP SDN controller, then it
	is possible for the controller to retrieval the topology in non-		is possible for the controller to retrieval the topology in non-
	backbone area. The topology retrieval process and its usage		backbone area. The topology retrieval process and its usage
	limitation are described in the Appendix A and Appendix B.		limitation are described in the Appendix A and Appendix B.
	From the above scenarios, we can conclude it is useful to introduce		From the above scenarios, we can conclude it is useful to introduce
	and define the prefix originator sub TLV within OSPF.		and define the prefix originator sub TLV within OSPF.
	4. Prefix Source Router-ID sub-TLV		6. Prefix Source Router-ID sub-TLV
	[RFC7684] and [RFC8362] define the TLV extensions for OSPFv2 and		[RFC7684] and [RFC8362] define the TLV extensions for OSPFv2 and
	OSPFv3 respectively. These documents facilitate addition of new		OSPFv3 respectively. These documents facilitate addition of new
	attributes for prefixes and links. Based on these formats, we can		attributes for prefixes. Based on these formats, we can define new
	define new sub-TLV to advertise the "Prefix Source Router ID", as		sub-TLV to advertise the "Prefix Source Router ID", as that defined
	that defined in [RFC7794].		in [RFC7794].
	The "Prefix Source Router-ID" sub-TLV has the following format:		The "Prefix Source Router-ID" sub-TLV has the following format:
	0 1 2 3		0 1 2 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type | Length |		| Type | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Prefix Source Router-ID |		| Prefix Source Router-ID |
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Fig. 2 Prefix Source Router-ID sub-TLV Format		Figure 2: Prefix Source Router-ID sub-TLV Format
	o Source Router-ID Sub-TLV Type: TBD1[RFC7684] or TBD2 [RFC8362]		o Source Router-ID Sub-TLV Type: TBD1[RFC7684] or TBD2 [RFC8362]
	o Length: 4		o Length: 4
	o Value: Router-ID of OSPFv2/OSPFv3 source router		o Value: Router-ID of OSPFv2/OSPFv3 source router
	This sub-TLV can be included in the "OSPFv2 Extended Prefix Opaque		For OSPFv2, this sub-TLV is a sub-TLV of OSPFv2 Extended Prefix TLV,
	LSA" [RFC7684] or the "E-Inter-Area-Prefix-LSA" [RFC8362].		which is included in the "OSPFv2 Extended Prefix Opaque LSA"
			[RFC7684].
	5. Extended LSA Elements of Procedure		For OSPFv3, this sub-TLV is a sub-TLV of "Inter-Area-Prefix TLV",
			which is included in the "E-Inter-Area-Prefix-LSA".
			7. Extended LSA Elements of Procedure
	When an ABR, for example R2 in Fig.1, receives the Router-LSA		When an ABR, for example R2 in Fig.1, receives the Router-LSA
	announcement in area 2, it should originate the corresponding "OSPFv2		announcement in area 2, it should originate the corresponding "OSPFv2
	Extended Prefix Opaque LSA" for OSPFv2 or "E-Inter-Area-Prefix-LSA"		Extended Prefix Opaque LSA" for OSPFv2 or "E-Inter-Area-Prefix-LSA"
	for OSPFv3 that includes the Source Router-ID sub-TLV for the network		for OSPFv3 that includes the Source Router-ID sub-TLV for the network
	prefixes, e.g., for prefix Lt1, N2. etc., which identifies the source		prefixes, e.g., for prefix Lt1, N2. etc., which identifies the source
	router that advertised the prefix.		router that advertised the prefix.
	When S1 in another area receives such LSA, it then can learn that		When S1 in another area receives such LSA, it then can learn that
	prefix Lt1 is associated with node T1, check the ELC, ERLD, or MSD		prefix Lt1 is associated with node T1, check the ERLD, or MSD value
	value according to its necessity, and construct the right label stack		according to its necessity, and construct the right label stack at
	at the ingress node S1 for the traffic destined to Lt1.		the ingress node S1 for the traffic destined to Lt1.
	When R0 receives such LSA, it learns the Prefix Source Router-id and		When R0 receives such LSA, it learns the Prefix Source Router-id and
	includes it in the prefix information advertised to an SDN controller		includes it in the prefix information advertised to an SDN controller
	as described in[I-D.ietf-idr-bgp-ls-segment-routing-ext]. The SDN		as described in[I-D.ietf-idr-bgp-ls-segment-routing-ext]. The SDN
	controller can then use such information to build the inter-area		controller can then use such information to build the inter-area
	topology according to the process described in the Appendix A. The		topology according to the process described in the Appendix A. The
	topology retrieval process may not suitable for some environments as		topology retrieval process may not suitable for some environments as
	stated in Appendix B.		stated in Appendix B.
	6. Security Considerations		8. Security Considerations
	Security concerns for OSPF are addressed in [RFC5709]		Security concerns for OSPF are addressed in [RFC5709]
	Advertisement of the additional information defined in this document		Advertisement of the additional information defined in this document
	introduces no new security concerns		introduces no new security concerns
	7. IANA Considerations		9. IANA Considerations
	This document adds the following new sub-TLV to the registry of		This specification defines one Prefix Source Router-ID sub-TLV as
	"OSPFv2 Extended Prefix TLV Sub-TLVs". The allocation policy is IETF		described in Section 6. This value should be added to the existing
	Review that defined in [RFC7684]		OSPFv2 Extended Prefix TLV Sub-TLVs registry and OSPFv3 Extended-LSA
			Sub-TLVs registry respectively.
			Th following new sub-TLV is added to the registry of "OSPFv2 Extended
			Prefix TLV Sub-TLVs". The allocation policy is IETF Review that
			defined in [RFC7684]
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++
	| Code Point | Description | Status |		| Code Point | Description | Status |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++
	| TBD | Prefix Source Sub-TLV | Allocation from IANA |		| TBD | Prefix Source Sub-TLV | Allocation from IANA |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++
	Fig.3: Prefix Source sub-TLV CodePoint from OSPFv2 Extended Prefix TLV Sub-TLVs		Figure 3: Prefix Source sub-TLV CodePoint from OSPFv2 Extended Prefix TLV Sub-TLVs
			The following sub-TLV is added to the registry of "OSPFv3 Extended-
	This document adds the following sub-TLV to the registry of "OSPFv3		LSA Sub-TLVs". The allocation is IETF Review that defined in
	Extended-LSA Sub-TLVs". The allocation is IETF Review that defined		[RFC8362]
	in [RFC8362]
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++
	| Code Point | Description | Status |		| Code Point | Description | Status |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++
	| TBD | Prefix Source Sub-TLV | Allocation from IANA |		| TBD | Prefix Source Sub-TLV | Allocation from IANA |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++++++++
	Fig.4: Prefix Source sub-TLV CodePoint from OSPFv3 Extended-LSA Sub-TLVs		Figure 4: Prefix Source sub-TLV CodePoint from OSPFv3 Extended-LSA Sub-TLVs
	8. Acknowledgement		10. Acknowledgement
	Many thanks to Les Ginsberg for his valuable suggestions on this		Many thanks to Les Ginsberg for his valuable suggestions on this
	draft. And also thanks Jeff Tantsura,Rob Shakir, Van De Velde		draft. And also thanks Jeff Tantsura,Rob Shakir, Van De Velde
	Gunter, Goethals Dirk, Shaofu Peng, John E Drake for their valuable		Gunter, Goethals Dirk, Shaofu Peng, John E Drake for their valuable
	comments on this draft.		comments on this draft.
	9. References		11. References
	9.1. Normative References
	[I-D.ietf-ospf-mpls-elc]
	Xu, X., Kini, S., Psenak, P., Filsfils, C., and S.
	Litkowski, "Signaling Entropy Label Capability and Entropy
	Readable Label-stack Depth Using OSPF", draft-ietf-ospf-
	mpls-elc-08 (work in progress), May 2019.
	[I-D.ietf-ospf-segment-routing-msd]		11.1. Normative References
	Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
	"Signaling MSD (Maximum SID Depth) using OSPF", draft-
	ietf-ospf-segment-routing-msd-25 (work in progress),
	October 2018.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
	[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,		[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
	Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic		Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
	Authentication", RFC 5709, DOI 10.17487/RFC5709, October		Authentication", RFC 5709, DOI 10.17487/RFC5709, October
	2009, <https://www.rfc-editor.org/info/rfc5709>.		2009, <https://www.rfc-editor.org/info/rfc5709>.
	skipping to change at page 7, line 36 ¶		skipping to change at page 8, line 10 ¶
	[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and		[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
	U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4		U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
	and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,		and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
	March 2016, <https://www.rfc-editor.org/info/rfc7794>.		March 2016, <https://www.rfc-editor.org/info/rfc7794>.
	[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and		[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
	F. Baker, "OSPFv3 Link State Advertisement (LSA)		F. Baker, "OSPFv3 Link State Advertisement (LSA)
	Extensibility", RFC 8362, DOI 10.17487/RFC8362, April		Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
	2018, <https://www.rfc-editor.org/info/rfc8362>.		2018, <https://www.rfc-editor.org/info/rfc8362>.
	9.2. Informative References		[RFC8476] Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
			"Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476,
			DOI 10.17487/RFC8476, December 2018,
			<https://www.rfc-editor.org/info/rfc8476>.
			11.2. Informative References
	[I-D.ietf-idr-bgp-ls-segment-routing-ext]		[I-D.ietf-idr-bgp-ls-segment-routing-ext]
	Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,		Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
	and M. Chen, "BGP Link-State extensions for Segment		and M. Chen, "BGP Link-State extensions for Segment
	Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-15		Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16
	(work in progress), May 2019.		(work in progress), June 2019.
			[I-D.ietf-ospf-mpls-elc]
			Xu, X., Kini, S., Psenak, P., Filsfils, C., and S.
			Litkowski, "Signaling Entropy Label Capability and Entropy
			Readable Label-stack Depth Using OSPF", draft-ietf-ospf-
			mpls-elc-08 (work in progress), May 2019.
	Appendix A. Inter-Area Topology Retrieval Process		Appendix A. Inter-Area Topology Retrieval Process
	When an IP SDN Controller receives this information, it should		When an IP SDN Controller receives this information, it should
	compare the prefix NLRI that included in the BGP-LS packet. When it		compare the prefix NLRI that included in the BGP-LS packet. When it
	encounters the same prefix but with different source router ID, it		encounters the same prefix but with different source router ID, it
	should extract the corresponding area-ID, rebuild the link between		should extract the corresponding area-ID, rebuild the link between
	these two different source routers in non-backbone area. Belows is		these two different source routers in non-backbone area. Belows is
	one example that based on the Fig.1:		one example that based on the Fig.1:
	skipping to change at page 8, line 50 ¶		skipping to change at page 9, line 36 ¶
	and 128 for IPv6 prefixes.		and 128 for IPv6 prefixes.
	Authors' Addresses		Authors' Addresses
	Aijun Wang		Aijun Wang
	China Telecom		China Telecom
	Beiqijia Town, Changping District		Beiqijia Town, Changping District
	Beijing 102209		Beijing 102209
	China		China
	Email: wangaj.bri@chinatelecom.cn		Email: wangaj3@chinatelecom.cn
	Acee Lindem		Acee Lindem
	Cisco Systems		Cisco Systems
	301 Midenhall Way		301 Midenhall Way
	Cary, NC 27513		Cary, NC 27513
	USA		USA
	Email: acee@cisco.com		Email: acee@cisco.com
	Jie Dong		Jie Dong
	Huawei Technologies		Huawei Technologies
	Beijing		Beijing
	China		China
	Email: jie.dong@huawei.com		Email: jie.dong@huawei.com
	Ketan Talaulikar		Ketan Talaulikar
	Cisco Systems		Cisco Systems
	S.No. 154/6, Phase I, Hinjawadi		S.No. 154/6, Phase I, Hinjawadi
End of changes. 36 change blocks.
	94 lines changed or deleted		129 lines changed or added
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