< draft-ietf-ospf-link-overload-13.txt		draft-ietf-ospf-link-overload-14.txt >
	Open Shortest Path First IGP S. Hegde		Open Shortest Path First IGP S. Hegde
	Internet-Draft Juniper Networks, Inc.		Internet-Draft Juniper Networks, Inc.
	Intended status: Standards Track P. Sarkar		Intended status: Standards Track P. Sarkar
	Expires: July 25, 2018 H. Gredler		Expires: July 28, 2018 Arrcus Inc.
			H. Gredler
	Individual		Individual
	M. Nanduri		M. Nanduri
	ebay Corporation		ebay Corporation
	L. Jalil		L. Jalil
	Verizon		Verizon
	January 21, 2018		January 24, 2018
	OSPF Graceful Link shutdown		OSPF Graceful Link shutdown
	draft-ietf-ospf-link-overload-13		draft-ietf-ospf-link-overload-14
	Abstract		Abstract
	When a link is being prepared to be taken out of service, the traffic		When a link is being prepared to be taken out of service, the traffic
	needs to be diverted from both ends of the link. Increasing the		needs to be diverted from both ends of the link. Increasing the
	metric to the highest value on one side of the link is not sufficient		metric to the highest value on one side of the link is not sufficient
	to divert the traffic flowing in the other direction.		to divert the traffic flowing in the other direction.
	It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be		It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be
	able to advertise a link as being in a graceful-shutdown state to		able to advertise a link as being in a graceful-shutdown state to
	skipping to change at page 2, line 10 ¶		skipping to change at page 2, line 10 ¶
	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 July 25, 2018.		This Internet-Draft will expire on July 28, 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 2, line 35 ¶		skipping to change at page 2, line 35 ¶
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
	3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4		3. Flooding Scope . . . . . . . . . . . . . . . . . . . . . . . 4
	4. Graceful-Link-Shutdown sub-TLV . . . . . . . . . . . . . . . 4		4. Graceful-Link-Shutdown sub-TLV . . . . . . . . . . . . . . . 4
	4.1. OSPFv2 graceful-link-shutdown sub-TLV . . . . . . . . . . 4		4.1. OSPFv2 graceful-link-shutdown sub-TLV . . . . . . . . . . 4
	4.2. Remote IPv4 Address Sub-TLV . . . . . . . . . . . . . . . 5		4.2. Remote IPv4 Address Sub-TLV . . . . . . . . . . . . . . . 5
	4.3. Local/Remote Interface ID Sub-TLV . . . . . . . . . . . . 5		4.3. Local/Remote Interface ID Sub-TLV . . . . . . . . . . . . 6
	4.4. OSPFv3 Graceful-Link-Shutdown sub-TLV . . . . . . . . . . 6		4.4. OSPFv3 Graceful-Link-Shutdown sub-TLV . . . . . . . . . . 6
	4.5. BGP-LS Graceful-Link-Shutdown TLV . . . . . . . . . . . . 6		4.5. BGP-LS Graceful-Link-Shutdown TLV . . . . . . . . . . . . 7
	4.6. Distinguishing parallel links . . . . . . . . . . . . . . 7		4.6. Distinguishing parallel links . . . . . . . . . . . . . . 7
	5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 8		5. Elements of procedure . . . . . . . . . . . . . . . . . . . . 8
	5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 8		5.1. Point-to-point links . . . . . . . . . . . . . . . . . . 8
	5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 9		5.2. Broadcast/NBMA links . . . . . . . . . . . . . . . . . . 9
	5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 9		5.3. Point-to-multipoint links . . . . . . . . . . . . . . . . 9
	5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 9		5.4. Unnumbered interfaces . . . . . . . . . . . . . . . . . . 10
	5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 10		5.5. Hybrid Broadcast and P2MP interfaces . . . . . . . . . . 10
	6. Backward compatibility . . . . . . . . . . . . . . . . . . . 10		6. Maximum TE Metric . . . . . . . . . . . . . . . . . . . . . . 10
	7. Applications . . . . . . . . . . . . . . . . . . . . . . . . 10		7. Backward compatibility . . . . . . . . . . . . . . . . . . . 10
	7.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 10		8. Applications . . . . . . . . . . . . . . . . . . . . . . . . 11
	7.2. Controller based Traffic Engineering Deployments . . . . 11		8.1. Pseudowire Services . . . . . . . . . . . . . . . . . . . 11
	7.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 12		8.2. Controller based Traffic Engineering Deployments . . . . 12
	7.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 13		8.3. L3VPN Services and sham-links . . . . . . . . . . . . . . 13
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 13		8.4. Hub and spoke deployment . . . . . . . . . . . . . . . . 13
	9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13		9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
	10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13		10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
	11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14		11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
	11.1. Normative References . . . . . . . . . . . . . . . . . . 14		12. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
	11.2. Informative References . . . . . . . . . . . . . . . . . 14		12.1. Normative References . . . . . . . . . . . . . . . . . . 14
			12.2. Informative References . . . . . . . . . . . . . . . . . 15
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
	1. Introduction		1. Introduction
	When a node is being prepared for a planned maintenance or upgrade,		When a node is being prepared for a planned maintenance or upgrade,
	[RFC6987] provides mechanisms to advertise the node being in a		[RFC6987] provides mechanisms to advertise the node being in a
	graceful-shutdown state by setting all outgoing link costs to		graceful-shutdown state by setting all outgoing link costs to
	MaxLinkMetric (0xffff). These procedures are specific to the		MaxLinkMetric (0xffff). These procedures are specific to the
	maintenance activity on a node and cannot be used when a single link		maintenance activity on a node and cannot be used when a single link
	on the node requires maintenance.		on the node requires maintenance.
	skipping to change at page 3, line 38 ¶		skipping to change at page 3, line 39 ¶
	underlying network going offline for maintenance, it is useful to		underlying network going offline for maintenance, it is useful to
	divert the traffic away from the node before the maintenance is		divert the traffic away from the node before the maintenance is
	actually performed. Since the nodes in the underlying network are		actually performed. Since the nodes in the underlying network are
	not visible to OSPF, the existing stub router mechanism described in		not visible to OSPF, the existing stub router mechanism described in
	[RFC6987] cannot be used. In a service provider's network, there may		[RFC6987] cannot be used. In a service provider's network, there may
	be many CE-to-CE connections that run over a single PE. It is		be many CE-to-CE connections that run over a single PE. It is
	cumbersome to change the metric on every CE-to-CE connection in both		cumbersome to change the metric on every CE-to-CE connection in both
	directions. This document provides a mechanism to change metric in		directions. This document provides a mechanism to change metric in
	other direction of the link and also use the link as a last-resort-		other direction of the link and also use the link as a last-resort-
	link if no alternate paths are available. An application specific to		link if no alternate paths are available. An application specific to
	this use case is described in detail in Section 7.1.		this use case is described in detail in Section 8.1.
	The procedures described in this draft may be used to divert the		The procedures described in this draft may be used to divert the
	traffic away from the link in other scenarios and is not restricted		traffic away from the link in other scenarios and is not restricted
	to link-shutdown or link-replacement activity.		to link-shutdown or link-replacement activity.
	This document provides mechanisms to advertise graceful-link-shutdown		This document provides mechanisms to advertise graceful-link-shutdown
	state in the flexible encodings provided by OSPFv2 Prefix/Link		state in the flexible encodings provided by OSPFv2 Prefix/Link
	Attribute Advertisement [RFC7684]. Throughout this document, OSPF is		Attribute Advertisement [RFC7684]. Throughout this document, OSPF is
	used when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or		used when the text applies to both OSPFv2 and OSPFv3. OSPFv2 or
	OSPFv3 is used when the text is specific to one version of the OSPF		OSPFv3 is used when the text is specific to one version of the OSPF
	skipping to change at page 4, line 29 ¶		skipping to change at page 4, line 29 ¶
	so that LSP ingress routers/controllers can learn about the		so that LSP ingress routers/controllers can learn about the
	impending maintenance activity and apply specific policies to re-		impending maintenance activity and apply specific policies to re-
	route the LSPs for traffic-engineering based deployments.		route the LSPs for traffic-engineering based deployments.
	4. Allow the link to be used as last resort link to prevent traffic		4. Allow the link to be used as last resort link to prevent traffic
	disruption when alternate paths are not available.		disruption when alternate paths are not available.
	3. Flooding Scope		3. Flooding Scope
	The graceful-link-shutdown information is flooded in area-scoped		The graceful-link-shutdown information is flooded in area-scoped
	Extended Link Opaque LSA [RFC7684]. The Graceful-Link-Shutdown sub-		Extended Link Opaque LSA [RFC7684] for OSPFv2 and E-Router-LSA for
	TLV MAY be processed by the head-end nodes or the controller as		OSPFv3 [I-D.ietf-ospf-ospfv3-lsa-extend]. The Graceful-Link-Shutdown
	described in the Section 7. The procedures for processing the		sub-TLV MAY be processed by the head-end nodes or the controller as
			described in the Section 8. The procedures for processing the
	Graceful-Link-Shutdown sub-TLV are described in Section 5.		Graceful-Link-Shutdown sub-TLV are described in Section 5.
	4. Graceful-Link-Shutdown sub-TLV		4. Graceful-Link-Shutdown sub-TLV
	4.1. OSPFv2 graceful-link-shutdown sub-TLV		4.1. OSPFv2 graceful-link-shutdown sub-TLV
	The Graceful-Link-Shutdown sub-TLV identifies the link as being		The Graceful-Link-Shutdown sub-TLV identifies the link as being
	gracefully shutdown. It is advertised in extended Link TLV of the		gracefully shutdown. It is advertised in extended Link TLV of the
	Extended Link Opaque LSA as defined in [RFC7684].		Extended Link Opaque LSA as defined in [RFC7684].
	skipping to change at page 7, line 4 ¶		skipping to change at page 7, line 23 ¶
	Type : TBA (Suggested value 7)		Type : TBA (Suggested value 7)
	Length: 0		Length: 0
	4.5. BGP-LS Graceful-Link-Shutdown TLV		4.5. BGP-LS Graceful-Link-Shutdown TLV
	BGP-LS as defined in [RFC7752] is a mechanism to distribute network		BGP-LS as defined in [RFC7752] is a mechanism to distribute network
	information to external entities using BGP routing protocol.		information to external entities using BGP routing protocol.
	Graceful-link-shutdown is an imporatant link information that the		Graceful-link-shutdown is an imporatant link information that the
	external entities can use for various use cases as defined in		external entities can use for various use cases as defined in
	Section 7. BGP Link NLRI is used to carry the link information. A		Section 8. BGP Link NLRI is used to carry the link information. A
	new TLV called Graceful-Link-Shutdown is defined to describe the link		new TLV called Graceful-Link-Shutdown is defined to describe the link
	attribute corresponding to graceful-link-shutdown state.		attribute corresponding to graceful-link-shutdown state. The TLV
			format is as described in [RFC7752] sec 3.1. There is no value field
			and length field is set to zero for this TLV.
	4.6. Distinguishing parallel links		4.6. Distinguishing parallel links
	++++++++++I.w I.y +++++++++		++++++++++I.w I.y +++++++++
	|Router A|------------------|Router B |		|Router A|------------------|Router B |
	| |------------------| |		| |------------------| |
	++++++++++I.x I.z++++++++++		++++++++++I.x I.z++++++++++
	Figure 5: Parallel Linkls		Figure 5: Parallel Linkls
	skipping to change at page 7, line 35 ¶		skipping to change at page 8, line 10 ¶
	Link-ID: Router-ID B		Link-ID: Router-ID B
	Link-Data = I.w		Link-Data = I.w
	A third node (controller or head-end) in the network cannot		A third node (controller or head-end) in the network cannot
	distinguish the Interface on router B which is connected to this		distinguish the Interface on router B which is connected to this
	particular Interface with the above information. Interface with		particular Interface with the above information. Interface with
	address I.y or I.z could be chosen due to this ambiguity. In such		address I.y or I.z could be chosen due to this ambiguity. In such
	cases Remote-IPv4 Address sub-TLV should be originated and added to		cases Remote-IPv4 Address sub-TLV should be originated and added to
	the extended link-TLV. The use cases as described in Section 7		the extended link-TLV. The use cases as described in Section 8
	require controller or head-end nodes to interpret the graceful-link-		require controller or head-end nodes to interpret the graceful-link-
	shutdown information and hence the need for the RemoteIPv4 address		shutdown information and hence the need for the RemoteIPv4 address
	sub-TLV. I.y is carried in the extended-link-TLV which unambiguously		sub-TLV. I.y is carried in the extended-link-TLV which unambiguously
	identifies the interface on the remote side. OSPFv3 Router-link-TLV		identifies the interface on the remote side. OSPFv3 Router-link-TLV
	as described in [I-D.ietf-ospf-ospfv3-lsa-extend] contains Interface		as described in [I-D.ietf-ospf-ospfv3-lsa-extend] contains Interface
	ID and neighbor's Interface-ID which can uniquely identify connecting		ID and neighbor's Interface-ID which can uniquely identify connecting
	interface on the remote side and hence OSPFv3 does not require		interface on the remote side and hence OSPFv3 does not require
	seperate Remote-IPv6 address to be advertised along with OSPFv3-		seperate Remote-IPv6 address to be advertised along with OSPFv3-
	Graceful-Link-Shutdown sub-TLV.		Graceful-Link-Shutdown sub-TLV.
	5. Elements of procedure		5. Elements of procedure
	As defined in [RFC7684] every link on the node will have a separate		As defined in [RFC7684] every link on the node will have a separate
	Extended Link Opaque LSA. The node that has the link to be taken out		Extended Link Opaque LSA. The node that has the link to be taken out
	of service SHOULD advertise the Graceful-Link-Shutdown sub-TLV in the		of service MUST advertise the Graceful-Link-Shutdown sub-TLV in the
	Extended Link TLV of the Extended Link Opaque LSA as defined in		Extended Link TLV of the Extended Link Opaque LSA as defined in
	[RFC7684] for OSPFv2. The Graceful-Link-Shutdown sub-TLV indicates		[RFC7684] for OSPFv2 and Router-Link TLV of E-Router-LSA for OSPFv3.
	that the link identified by the sub-TLV is subjected to maintenance.		The Graceful-Link-Shutdown sub-TLV indicates that the link identified
	The Graceful-Link-Shutdown information is advertised as a property of		by the sub-TLV is subjected to maintenance. The Graceful-Link-
	the link and is flooded across the area. This information can be		Shutdown information is advertised as a property of the link and is
	used by ingress routers or controllers to take special actions. An		flooded across the area. This information can be used by ingress
	application specific to this use case is described in Section 7.2.		routers or controllers to take special actions. An application
			specific to this use case is described in Section 8.2.
	The precise action taken by the remote node at the other end of the		The precise action taken by the remote node at the other end of the
	link identified for graceful-shutdown depends on the link type.		link identified for graceful-shutdown depends on the link type.
	5.1. Point-to-point links		5.1. Point-to-point links
	The node that has the link to be taken out of service MUST set metric		The node that has the link to be taken out of service MUST set metric
	of the link to MaxLinkMetric (0xffff) and re-originate its router-		of the link to MaxLinkMetric (0xffff) and re-originate its router-
	LSA. MAX-TE-METRIC is a constant defined by this draft and set to		LSA. MAX-TE-METRIC (0xfffffffe). The TE metric SHOULD be set to
	0xfffffffe. The TE metric SHOULD be set to MAX-TE-METRIC		MAX-TE-METRIC (0xfffffffe) and the node SHOULD re-originate the
	(0xfffffffe) and the node SHOULD re-originate the corresponding TE		corresponding TE Link Opaque LSAs. When a Graceful-Link-Shutdown
	Link Opaque LSAs. When a Graceful-Link-Shutdown sub-TLV is received		sub-TLV is received for a point-to-point link, the remote node MUST
	for a point-to-point link, the remote node MUST identify the local		identify the local link which corresponds to the graceful-shutdown
	link which corresponds to the graceful-shutdown link and set the		link and set the metric to MaxLinkMetric (0xffff) and the remote node
	metric to MaxLinkMetric (0xffff) and the remote node MUST re-		MUST re-originate its router-LSA with the changed metric. The TE
	originate its router-LSA with the changed metric. The TE metric		metric SHOULD be set to MAX-TE-METRIC (0xfffffffe) and the TE opaque
	SHOULD be set to MAX-TE-METRIC (0xfffffffe) and the TE opaque LSA for		LSA for the link SHOULD be re-originated with new value.
	the link SHOULD be re-originated with new value.
	The Extended link opaque LSAs and the Extended link TLV are not		The Extended link opaque LSAs and the Extended link TLV are not
	scoped for multi-topology [RFC4915]. In multi-topology deployments		scoped for multi-topology [RFC4915]. In multi-topology deployments
	[RFC4915], the Graceful-Link-Shutdown sub-TLV advertised in an		[RFC4915], the Graceful-Link-Shutdown sub-TLV advertised in an
	Extended Link opaque LSA corresponds to all the topologies which		Extended Link opaque LSA corresponds to all the topologies which
	include the link. The receiver node SHOULD change the metric in the		include the link. The receiver node SHOULD change the metric in the
	reverse direction for all the topologies which include the remote		reverse direction for all the topologies which include the remote
	link and re-originate the router-LSA as defined in [RFC4915].		link and re-originate the router-LSA as defined in [RFC4915].
	When the originator of the Graceful-Link-Shutdown sub-TLV purges the		When the originator of the Graceful-Link-Shutdown sub-TLV purges the
	skipping to change at page 10, line 17 ¶		skipping to change at page 10, line 31 ¶
	Hybrid Broadcast and P2MP interfaces represent a broadcast network		Hybrid Broadcast and P2MP interfaces represent a broadcast network
	modeled as P2MP interfaces. [RFC6845] describes procedures to handle		modeled as P2MP interfaces. [RFC6845] describes procedures to handle
	these interfaces. Operation for the Hybrid interfaces is similar to		these interfaces. Operation for the Hybrid interfaces is similar to
	the P2MP interfaces. When a Graceful-Link-Shutdown sub-TLV is		the P2MP interfaces. When a Graceful-Link-Shutdown sub-TLV is
	received for a hybrid link, the remote node MUST identify the		received for a hybrid link, the remote node MUST identify the
	neighbor which corresponds to the graceful-shutdown link and set the		neighbor which corresponds to the graceful-shutdown link and set the
	metric to MaxLinkMetric (0xffff). All the remote nodes connected to		metric to MaxLinkMetric (0xffff). All the remote nodes connected to
	originator MUST re-originate the router-LSA with the changed metric		originator MUST re-originate the router-LSA with the changed metric
	for the neighbor.		for the neighbor.
	6. Backward compatibility		6. Maximum TE Metric
			MAX-TE-METRIC is a new fixed architectural value introduced in this
			document.
			The metric value indicates that a link with this metric should be
			used as a last-resort link to carry the traffic. It is defined to be
			of value 0xfffffffe.
			7. Backward compatibility
	The mechanisms described in the document are fully backward		The mechanisms described in the document are fully backward
	compatible. It is required that the node adverting the Graceful-		compatible. It is required that the node adverting the Graceful-
	Link-Shutdown sub-TLV as well as the node at the remote end of the		Link-Shutdown sub-TLV as well as the node at the remote end of the
	graceful-shutdown link support the extensions described herein for		graceful-shutdown link support the extensions described herein for
	the traffic to diverted from the graceful-shutdown link. If the		the traffic to diverted from the graceful-shutdown link. If the
	remote node doesn't support the capability, it will still use the		remote node doesn't support the capability, it will still use the
	graceful-shutdown link but there are no other adverse effects. In		graceful-shutdown link but there are no other adverse effects. In
	the case of broadcast links using two-part metrics, the backward		the case of broadcast links using two-part metrics, the backward
	compatibility procedures as described in [RFC8042] are applicable.		compatibility procedures as described in [RFC8042] are applicable.
	7. Applications		8. Applications
	7.1. Pseudowire Services		8.1. Pseudowire Services
	Many service providers offer pseudo-wire services to customers using		Many service providers offer pseudo-wire services to customers using
	L2 circuits. The IGP protocol that runs in the customer network		L2 circuits. The IGP protocol that runs in the customer network
	would also run over the pseudo-wire to create a seamless private		would also run over the pseudo-wire to create a seamless private
	network for the customer. Service providers want to offer graceful-		network for the customer. Service providers want to offer graceful-
	shutdown functionality when the PE device is taken-out for		shutdown functionality when the PE device is taken-out for
	maintenance. The provider should guarantee that the PE is taken out		maintenance. The provider should guarantee that the PE is taken out
	for maintenance only after the service is successfully diverted on an		for maintenance only after the service is successfully diverted on an
	alternate path. There can be large number of customers attached to a		alternate path. There can be large number of customers attached to a
	PE node and the remote end-points for these pseudo-wires are spread		PE node and the remote end-points for these pseudo-wires are spread
	skipping to change at page 11, line 32 ¶		skipping to change at page 12, line 6 ¶
	Figure 6: Pseudowire Services		Figure 6: Pseudowire Services
	In the example shown in Figure 6, when the PE1 node is going out of		In the example shown in Figure 6, when the PE1 node is going out of
	service for maintenance, service providers set the PE1 to graceful-		service for maintenance, service providers set the PE1 to graceful-
	link-shutdown state. The PE1 going in to maintenance state triggers		link-shutdown state. The PE1 going in to maintenance state triggers
	all the CEs connected to the PE (CE1 in this case) to set their		all the CEs connected to the PE (CE1 in this case) to set their
	pseudowire links passing via PE1 to graceful-link-shutdown state.		pseudowire links passing via PE1 to graceful-link-shutdown state.
	The mechanisms used to communicate between PE1 and CE1 is outside the		The mechanisms used to communicate between PE1 and CE1 is outside the
	scope of this document. CE1 sets the graceful-link-shutdown state on		scope of this document. CE1 sets the graceful-link-shutdown state on
	its private VLAN connecting CE3, CE2 and CE4 and changes the metric		its private VLAN connecting CE3, CE2 and CE4 and changes the metric
	to MAX_METRIC and re-originates the corresponding LSA. The remote		to MaxLinkMetric and re-originates the corresponding LSA. The remote
	end of the link at CE3, CE2, and CE4 also set the metric on the link		end of the link at CE3, CE2, and CE4 also set the metric on the link
	to MaxLinkMetric and the traffic from both directions gets diverted		to MaxLinkMetric and the traffic from both directions gets diverted
	away from the pseudowires.		away from the pseudowires.
	7.2. Controller based Traffic Engineering Deployments		8.2. Controller based Traffic Engineering Deployments
	In controller-based deployments where the controller participates in		In controller-based deployments where the controller participates in
	the IGP protocol, the controller can also receive the graceful-link-		the IGP protocol, the controller can also receive the graceful-link-
	shutdown information as a warning that link maintenance is imminent.		shutdown information as a warning that link maintenance is imminent.
	Using this information, the controller can find alternate paths for		Using this information, the controller can find alternate paths for
	traffic which uses the affected link. The controller can apply		traffic which uses the affected link. The controller can apply
	various policies and re-route the LSPs away from the link undergoing		various policies and re-route the LSPs away from the link undergoing
	maintenance. If there are no alternate paths satisfying the traffic		maintenance. If there are no alternate paths satisfying the traffic
	engineering constraints, the controller might temporarily relax those		engineering constraints, the controller might temporarily relax those
	constraints and put the service on a different path. Increasing the		constraints and put the service on a different path. Increasing the
	skipping to change at page 12, line 31 ¶		skipping to change at page 13, line 7 ¶
	of 10 Gbps bandwidth on each link. The links P1->P3 and P3->P2 have		of 10 Gbps bandwidth on each link. The links P1->P3 and P3->P2 have
	only 1 Gbps capacity and there is no alternate path satisfying the		only 1 Gbps capacity and there is no alternate path satisfying the
	bandwidth constraint of 10Gbps. When P1->P2 link is being prepared		bandwidth constraint of 10Gbps. When P1->P2 link is being prepared
	for maintenance, the controller receives the graceful-link-shutdown		for maintenance, the controller receives the graceful-link-shutdown
	information, as there is no alternate path available which satisfies		information, as there is no alternate path available which satisfies
	the constraints, the controller chooses a path that is less optimal		the constraints, the controller chooses a path that is less optimal
	and temporarily sets up an alternate path via P1->P3->P2. Once the		and temporarily sets up an alternate path via P1->P3->P2. Once the
	traffic is diverted, the P1->P2 link can be taken out of service for		traffic is diverted, the P1->P2 link can be taken out of service for
	maintenance/upgrade.		maintenance/upgrade.
	7.3. L3VPN Services and sham-links		8.3. L3VPN Services and sham-links
	Many service providers offer L3VPN services to customers and CE-PE		Many service providers offer L3VPN services to customers and CE-PE
	links run OSPF [RFC4577]. When PE is taken out of service for		links run OSPF [RFC4577]. When PE is taken out of service for
	maintenance, all the links on the PE can be set to graceful-link-		maintenance, all the links on the PE can be set to graceful-link-
	shutdown state which will gurantee that the traffic to/from dual-		shutdown state which will gurantee that the traffic to/from dual-
	homed CEs gets diverted. The interaction between OSPF and BGP is		homed CEs gets diverted. The interaction between OSPF and BGP is
	outside the scope of this document. [RFC6987] based mechanism with		outside the scope of this document. [RFC6987] based mechanism with
	summaries and externals advertised with high metrics could also be		summaries and externals advertised with high metrics could also be
	used to achieve the same functionality when implementations support		used to achieve the same functionality when implementations support
	high metrics advertisement for summaries and externals.		high metrics advertisement for summaries and externals.
	Another useful usecase is when ISPs provide sham-link services to		Another useful usecase is when ISPs provide sham-link services to
	customers [RFC4577]. When PE goes out of service for maintenance,		customers [RFC4577]. When PE goes out of service for maintenance,
	all sham-links on the PE can be set to graceful-link-shutdown state		all sham-links on the PE can be set to graceful-link-shutdown state
	and traffic can be divered from both ends without having to touch the		and traffic can be divered from both ends without having to touch the
	configurations on the remote end of the sham-links.		configurations on the remote end of the sham-links.
	7.4. Hub and spoke deployment		8.4. Hub and spoke deployment
	OSPF is largely deployed in Hub and Spoke deployments with a large		OSPF is largely deployed in Hub and Spoke deployments with a large
	number of spokes connecting to the Hub. It is a general practice to		number of spokes connecting to the Hub. It is a general practice to
	deploy multiple Hubs with all spokes connecting to these Hubs to		deploy multiple Hubs with all spokes connecting to these Hubs to
	achieve redundancy. The [RFC6987] mechanism can be used to divert		achieve redundancy. The [RFC6987] mechanism can be used to divert
	the spoke-to-spoke traffic from the overloaded hub router. The		the spoke-to-spoke traffic from the overloaded hub router. The
	traffic that flows from spokes via the hub into an external network		traffic that flows from spokes via the hub into an external network
	may not be diverted in certain scenarios.When a Hub node goes down		may not be diverted in certain scenarios.When a Hub node goes down
	for maintenance, all links on the Hub can be set to graceful-link-		for maintenance, all links on the Hub can be set to graceful-link-
	shutdown state and traffic gets divered from the spoke sites as well		shutdown state and traffic gets divered from the spoke sites as well
	without having to make configuration changes on the spokes.		without having to make configuration changes on the spokes.
	8. Security Considerations		9. Security Considerations
	This document does not introduce any further security issues other		This document does not introduce any further security issues other
	than those discussed in [RFC2328] and [RFC5340].		than those discussed in [RFC2328] and [RFC5340].
	9. IANA Considerations		10. IANA Considerations
	This specification updates one OSPF registry:		This specification updates one OSPF registry:
	OSPFv2 Extended Link TLV Sub-TLVs		OSPFv2 Extended Link TLV Sub-TLVs
	i) Graceful-Link-Shutdown Sub-TLV - Suggested value 7		i) Graceful-Link-Shutdown Sub-TLV - Suggested value 7
	ii) Remote IPv4 Address Sub-TLV - Suggested value 8		ii) Remote IPv4 Address Sub-TLV - Suggested value 8
	iii) Local/Remote Interface ID Sub-TLV - Suggested Value 9		iii) Local/Remote Interface ID Sub-TLV - Suggested Value 9
	OSPFv3 Extended-LSA sub-TLV Registry		OSPFv3 Extended-LSA sub-TLV Registry
	i) Graceful-Link-Shutdown sub-TLV - suggested value 7		i) Graceful-Link-Shutdown sub-TLV - suggested value 7
	BGP-LS Link NLRI Registry [RFC7752]		BGP-LS Link NLRI Registry [RFC7752]
	i)Graceful-Link-Shutdown TLV - Suggested 1101		i)Graceful-Link-Shutdown TLV - Suggested 1101
	10. Acknowledgements		11. Acknowledgements
	Thanks to Chris Bowers for valuable inputs and edits to the document.		Thanks to Chris Bowers for valuable inputs and edits to the document.
	Thanks to Jeffrey Zhang, Acee Lindem and Ketan Talaulikar for inputs.		Thanks to Jeffrey Zhang, Acee Lindem and Ketan Talaulikar for inputs.
	Thanks to Karsten Thomann for careful review and inputs on the		Thanks to Karsten Thomann for careful review and inputs on the
	applications where graceful-link-shutdown is useful.		applications where graceful-link-shutdown is useful.
	11. References		12. References
	11.1. Normative References		12.1. Normative References
	[I-D.ietf-ospf-ospfv3-lsa-extend]		[I-D.ietf-ospf-ospfv3-lsa-extend]
	Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3		Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
	LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-10		LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-10
	(work in progress), May 2016.		(work in progress), May 2016.
			[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
			Requirement Levels", BCP 14, RFC 2119,
			DOI 10.17487/RFC2119, March 1997,
			<https://www.rfc-editor.org/info/rfc2119>.
	[RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast		[RFC6845] Sheth, N., Wang, L., and J. Zhang, "OSPF Hybrid Broadcast
	and Point-to-Multipoint Interface Type", RFC 6845,		and Point-to-Multipoint Interface Type", RFC 6845,
	DOI 10.17487/RFC6845, January 2013,		DOI 10.17487/RFC6845, January 2013,
	<https://www.rfc-editor.org/info/rfc6845>.		<https://www.rfc-editor.org/info/rfc6845>.
			[RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D.
			McPherson, "OSPF Stub Router Advertisement", RFC 6987,
			DOI 10.17487/RFC6987, September 2013,
			<https://www.rfc-editor.org/info/rfc6987>.
	[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,		[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
	Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute		Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
	Advertisement", RFC 7684, DOI 10.17487/RFC7684, November		Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
	2015, <https://www.rfc-editor.org/info/rfc7684>.		2015, <https://www.rfc-editor.org/info/rfc7684>.
	[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and		[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
	S. Ray, "North-Bound Distribution of Link-State and		S. Ray, "North-Bound Distribution of Link-State and
	Traffic Engineering (TE) Information Using BGP", RFC 7752,		Traffic Engineering (TE) Information Using BGP", RFC 7752,
	DOI 10.17487/RFC7752, March 2016,		DOI 10.17487/RFC7752, March 2016,
	<https://www.rfc-editor.org/info/rfc7752>.		<https://www.rfc-editor.org/info/rfc7752>.
	[RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part		[RFC8042] Zhang, Z., Wang, L., and A. Lindem, "OSPF Two-Part
	Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016,		Metric", RFC 8042, DOI 10.17487/RFC8042, December 2016,
	<https://www.rfc-editor.org/info/rfc8042>.		<https://www.rfc-editor.org/info/rfc8042>.
	11.2. Informative References		12.2. Informative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,
	<https://www.rfc-editor.org/info/rfc2119>.
	[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,		[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
	DOI 10.17487/RFC2328, April 1998,		DOI 10.17487/RFC2328, April 1998,
	<https://www.rfc-editor.org/info/rfc2328>.		<https://www.rfc-editor.org/info/rfc2328>.
	[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in		[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
	Support of Generalized Multi-Protocol Label Switching		Support of Generalized Multi-Protocol Label Switching
	(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,		(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
	<https://www.rfc-editor.org/info/rfc4203>.		<https://www.rfc-editor.org/info/rfc4203>.
	skipping to change at page 15, line 24 ¶		skipping to change at page 15, line 45 ¶
	[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF		[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
	for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,		for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
	<https://www.rfc-editor.org/info/rfc5340>.		<https://www.rfc-editor.org/info/rfc5340>.
	[RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton,		[RFC5817] Ali, Z., Vasseur, JP., Zamfir, A., and J. Newton,
	"Graceful Shutdown in MPLS and Generalized MPLS Traffic		"Graceful Shutdown in MPLS and Generalized MPLS Traffic
	Engineering Networks", RFC 5817, DOI 10.17487/RFC5817,		Engineering Networks", RFC 5817, DOI 10.17487/RFC5817,
	April 2010, <https://www.rfc-editor.org/info/rfc5817>.		April 2010, <https://www.rfc-editor.org/info/rfc5817>.
	[RFC6987] Retana, A., Nguyen, L., Zinin, A., White, R., and D.
	McPherson, "OSPF Stub Router Advertisement", RFC 6987,
	DOI 10.17487/RFC6987, September 2013,
	<https://www.rfc-editor.org/info/rfc6987>.
	Authors' Addresses		Authors' Addresses
	Shraddha Hegde		Shraddha Hegde
	Juniper Networks, Inc.		Juniper Networks, Inc.
	Embassy Business Park		Embassy Business Park
	Bangalore, KA 560093		Bangalore, KA 560093
	India		India
	Email: shraddha@juniper.net		Email: shraddha@juniper.net
	Pushpasis Sarkar		Pushpasis Sarkar
	Individual		Arrcus Inc.
	Email: pushpasis.ietf@gmail.com		Email: pushpasis.ietf@gmail.com
	Hannes Gredler		Hannes Gredler
	Individual		Individual
	Email: hannes@gredler.at		Email: hannes@gredler.at
	Mohan Nanduri		Mohan Nanduri
	ebay Corporation		ebay Corporation
	2025 Hamilton Avenue		2025 Hamilton Avenue
	San Jose, CA 98052		San Jose, CA 98052
	US		US
	Email: mnanduri@ebay.com		Email: mnanduri@ebay.com
	Luay Jalil		Luay Jalil
	Verizon		Verizon
End of changes. 36 change blocks.
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