draft-ietf-grow-bgp-gshut-09.txt		draft-ietf-grow-bgp-gshut-10.txt
	Network Working Group P. Francois		Network Working Group P. Francois, Ed.
	Internet-Draft Individual Contributor		Internet-Draft Individual Contributor
	Intended status: Informational B. Decraene		Intended status: Informational B. Decraene, Ed.
	Expires: January 4, 2018 Orange		Expires: January 28, 2018 Orange
	C. Pelsser		C. Pelsser
	Strasbourg University		Strasbourg University
	K. Patel		K. Patel
	Arrcus, Inc.		Arrcus, Inc.
	C. Filsfils		C. Filsfils
	Cisco Systems		Cisco Systems
	July 3, 2017		July 27, 2017
	Graceful BGP session shutdown		Graceful BGP session shutdown
	draft-ietf-grow-bgp-gshut-09		draft-ietf-grow-bgp-gshut-10
	Abstract		Abstract
	This draft describes operational procedures aimed at reducing the		This draft describes operational procedures aimed at reducing the
	amount of traffic lost during planned maintenances of routers or		amount of traffic lost during planned maintenances of routers or
	links, involving the shutdown of BGP peering sessions. It defines a		links, involving the shutdown of BGP peering sessions. It defines a
	well-known BGP community, called GRACEFUL_SHUTDOWN, to signal the		well-known BGP community, called GRACEFUL_SHUTDOWN, to signal the
	graceful shutdown of paths.		graceful shutdown of paths.
	Status of This Memo		Status of This Memo
	skipping to change at page 1, line 41 ¶		skipping to change at page 1, line 41 ¶
	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 http://datatracker.ietf.org/drafts/current/.		Drafts is at http://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 4, 2018.		This Internet-Draft will expire on January 28, 2018.
	Copyright Notice		Copyright Notice
	Copyright (c) 2017 IETF Trust and the persons identified as the		Copyright (c) 2017 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
	skipping to change at page 2, line 25 ¶		skipping to change at page 2, line 25 ¶
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
	3. Packet loss upon manual EBGP session shutdown . . . . . . . . 4		3. Packet loss upon manual EBGP session shutdown . . . . . . . . 4
	4. Practices to avoid packet losses . . . . . . . . . . . . . . 4		4. Practices to avoid packet losses . . . . . . . . . . . . . . 4
	4.1. Improving availability of alternate paths . . . . . . . . 4		4.1. Improving availability of alternate paths . . . . . . . . 4
	4.2. Make before break convergence: graceful shutdown . . . . 5		4.2. Make before break convergence: graceful shutdown . . . . 5
	4.3. Forwarding modes and transient forwarding loops during		4.3. Forwarding modes and transient forwarding loops during
	convergence . . . . . . . . . . . . . . . . . . . . . . . 5		convergence . . . . . . . . . . . . . . . . . . . . . . . 5
	5. EBGP graceful shutdown procedure . . . . . . . . . . . . . . 5		5. EBGP graceful shutdown procedure . . . . . . . . . . . . . . 5
	5.1. Pre-configuration . . . . . . . . . . . . . . . . . . . . 5		5.1. Pre-configuration . . . . . . . . . . . . . . . . . . . . 5
	5.2. Operations at maintenance time . . . . . . . . . . . . . 6		5.2. Operations at maintenance time . . . . . . . . . . . . . 6
	5.3. BGP implementation support for g-Shut . . . . . . . . . . 6		5.3. BGP implementation support for graceful shutdown . . . . 6
	6. Beyond EBGP graceful shutdown . . . . . . . . . . . . . . . . 7		6. Beyond EBGP graceful shutdown . . . . . . . . . . . . . . . . 7
	6.1. IBGP graceful shutdown . . . . . . . . . . . . . . . . . 7		6.1. IBGP graceful shutdown . . . . . . . . . . . . . . . . . 7
	6.2. Link Up cases . . . . . . . . . . . . . . . . . . . . . . 7		6.2. EBGP session establishment . . . . . . . . . . . . . . . 7
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 9		8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
	9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9		9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
	10.1. Normative References . . . . . . . . . . . . . . . . . . 9		10.1. Normative References . . . . . . . . . . . . . . . . . . 9
	10.2. Informative References . . . . . . . . . . . . . . . . . 9		10.2. Informative References . . . . . . . . . . . . . . . . . 9
	Appendix A. Alternative techniques with limited applicability . 10		Appendix A. Alternative techniques with limited applicability . 10
	A.1. Multi Exit Discriminator tweaking . . . . . . . . . . . . 10		A.1. Multi Exit Discriminator tweaking . . . . . . . . . . . . 10
	A.2. IGP distance Poisoning . . . . . . . . . . . . . . . . . 10		A.2. IGP distance Poisoning . . . . . . . . . . . . . . . . . 10
	Appendix B. Configuration Examples . . . . . . . . . . . . . . . 10		Appendix B. Configuration Examples . . . . . . . . . . . . . . . 10
	B.1. Cisco IOS XR . . . . . . . . . . . . . . . . . . . . . . 11		B.1. Cisco IOS XR . . . . . . . . . . . . . . . . . . . . . . 11
	B.2. BIRD . . . . . . . . . . . . . . . . . . . . . . . . . . 11		B.2. BIRD . . . . . . . . . . . . . . . . . . . . . . . . . . 11
	B.3. OpenBGPD . . . . . . . . . . . . . . . . . . . . . . . . 12		B.3. OpenBGPD . . . . . . . . . . . . . . . . . . . . . . . . 11
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	Routing changes in BGP can be caused by planned, maintenance		Routing changes in BGP can be caused by planned maintenance
	operations. This document discusses operational procedures to be		operations. This document discusses operational procedures to be
	applied in order to reduce or eliminate losses of packets during the		applied in order to reduce or eliminate loss of packets during the
	maintenance. These losses come from the transient lack of		maintenance. These losses come from the transient lack of
	reachability during the BGP convergence following the shutdown of an		reachability during the BGP convergence following the shutdown of an
	EBGP peering session between two Autonomous System Border Routers		EBGP peering session between two Autonomous System Border Routers
	(ASBR).		(ASBR).
	This document presents procedures for the cases where the forwarding		This document presents procedures for the cases where the forwarding
	plane is impacted by the maintenance, hence when the use of Graceful		plane is impacted by the maintenance, hence when the use of Graceful
	Restart does not apply.		Restart does not apply.
	The procedures described in this document can be applied to reduce or		The procedures described in this document can be applied to reduce or
	avoid packet loss for outbound and inbound traffic flows initially		avoid packet loss for outbound and inbound traffic flows initially
	forwarded along the peering link to be shut down. These procedures		forwarded along the peering link to be shut down. These procedures
	trigger, in both involved ASes, rerouting to the alternate path,		trigger, in both ASes, rerouting to the alternate path if one exists
	while allowing routers to keep using old paths until alternate ones		within the AS, while allowing the use of the old path until alternate
	are learned, installed in the RIB and in the FIB. This ensures that		ones are learned. This ensures that routers always have a valid
	routers always have a valid route available during the convergence		route available during the convergence process.
	process.
	The goal of the document is to meet the requirements described in		The goal of the document is to meet the requirements described in
	[RFC6198] at best, without changing the BGP protocol.		[RFC6198] at best, without changing the BGP protocol.
	This document defines a well-known community [RFC1997], called		This document defines a well-known community [RFC1997], called
	GRACEFUL_SHUTDOWN, for the purpose of reducing the management		GRACEFUL_SHUTDOWN, for the purpose of reducing the management
	overhead of gracefully shutting down BGP sessions. The well-known		overhead of gracefully shutting down BGP sessions. The well-known
	community allows implementers to provide an automated graceful		community allows implementers to provide an automated graceful
	shutdown mechanism that does not require any router reconfiguration		shutdown mechanism that does not require any router reconfiguration
	at maintenance time.		at maintenance time.
	skipping to change at page 4, line 11 ¶		skipping to change at page 4, line 11 ¶
	Loss of Connectivity (LoC: the state when a router has no path toward		Loss of Connectivity (LoC: the state when a router has no path toward
	an affected prefix.		an affected prefix.
	3. Packet loss upon manual EBGP session shutdown		3. Packet loss upon manual EBGP session shutdown
	Packets can be lost during a manual shutdown of an EBGP session for		Packets can be lost during a manual shutdown of an EBGP session for
	two reasons.		two reasons.
	First, routers involved in the convergence process can transiently		First, routers involved in the convergence process can transiently
	lack of paths toward an affected prefix, and drop traffic destined to		lack paths toward an affected prefix, and drop traffic destined to
	this prefix. This is because alternate paths can be hidden by nodes		this prefix. This is because alternate paths can be hidden by nodes
	of an AS. This happens when the paths are not selected as best by		of an AS. This happens when the paths are not selected as best by
	the ASBR that receive them on an EBGP session, or by Route Reflectors		the ASBR that receive them on an EBGP session, or by Route Reflectors
	that do not propagate them further in the IBGP topology because they		that do not propagate them further in the IBGP topology because they
	do not select them as best.		do not select them as best.
	Second, within the AS, the FIB of routers can be transiently		Second, within the AS, the FIB of routers can be transiently
	inconsistent during the BGP convergence and packets toward affected		inconsistent during the BGP convergence and packets toward affected
	prefixes can loop and be dropped. Note that these loops only happen		prefixes can loop and be dropped. Note that these loops only happen
	when ASBR-to-ASBR encapsulation is not used within the AS.		when ASBR-to-ASBR encapsulation is not used within the AS.
	skipping to change at page 4, line 33 ¶		skipping to change at page 4, line 33 ¶
	This document only addresses the first reason.		This document only addresses the first reason.
	4. Practices to avoid packet losses		4. Practices to avoid packet losses
	This section describes means for an ISP to reduce the transient loss		This section describes means for an ISP to reduce the transient loss
	of packets upon a manual shutdown of a BGP session.		of packets upon a manual shutdown of a BGP session.
	4.1. Improving availability of alternate paths		4.1. Improving availability of alternate paths
	All solutions that increase the availability of alternate BGP paths		All solutions that increase the availability of alternate BGP paths
	at routers performing packet lookups in BGP tables such as		at routers performing forwarding lookups from BGP routes such as
	[I-D.ietf-idr-best-external] and [RFC7911] help in reducing the LoC		[I-D.ietf-idr-best-external] and [RFC7911] help in reducing the LoC
	bound with manual shutdown of EBGP sessions.		bound with the shutdown of EBGP sessions.
	One of such solutions increasing diversity in such a way that, at any		Any such solution where, at any single step of the convergence
	single step of the convergence process following the EBGP session		process following the EBGP session shutdown, a BGP router does not
	shutdown, a BGP router does not receive a message withdrawing the		receive a message withdrawing the only path it currently knows for a
	only path it currently knows for a given NLRI, allows for a		given NLRI, allows for a simplified graceful shutdown procedure.
	simplified graceful shutdown procedure.
	Note that the LoC for the inbound traffic of the maintained router,		Note that the LoC for the inbound traffic of graceful shutdown
	induced by a lack of alternate path propagation within the IBGP		initiator, due to the lack of an alternate path on the graceful
	topology of a receiver AS is not under the control of the operator		shutdown receiver is not under the control of the Initiator AS. The
	performing the maintenance. The part of the procedure aimed at		part of the procedure aimed at avoiding LoC for incoming traffic
	avoiding LoC for incoming paths can thus be applied even if no LoC		should thus be applied even if no LoC are expected for the outgoing
	are expected for the outgoing paths.		traffic.
	4.2. Make before break convergence: graceful shutdown		4.2. Make before break convergence: graceful shutdown
	The goal of this procedure is to retain the paths to be shutdown		The goal of this procedure is to retain the paths to be shutdown
	between the peers, but with a lower LOCAL_PREF value, allowing the		between the peers, but with a lower LOCAL_PREF value, allowing the
	paths to remain in use while alternate paths are selected and		paths to remain in use while alternate paths are selected and
	propagated, rather than simply withdrawing the paths.		propagated, rather than simply withdrawing the paths. The LOCAL_PREF
			value must be lower than the one of the alternate path. 0 being the
			lowest value, it can be used in all cases, except if it already has a
			special meaning within the AS.
	Section 5 describes configurations and actions to be performed for		Section 5 describes configurations and actions to be performed for
	the graceful shutdown of BGP sessions.		the graceful shutdown of BGP sessions.
	4.3. Forwarding modes and transient forwarding loops during convergence		4.3. Forwarding modes and transient forwarding loops during convergence
	The graceful shutdown procedure or the solutions improving the		The graceful shutdown procedure or the solutions improving the
	availability of alternate paths, do not change the fact that BGP		availability of alternate paths, do not change the fact that BGP
	convergence and the subsequent FIB updates are run independently on		convergence and the subsequent FIB updates are run independently on
	each router of the ASes. If the AS applying the solution does not		each router of the ASes. If the AS applying the solution does not
	skipping to change at page 6, line 16 ¶		skipping to change at page 6, line 16 ¶
	On the graceful shutdown initiator, upon maintenance time, it is		On the graceful shutdown initiator, upon maintenance time, it is
	required to:		required to:
	o apply an outbound BGP route policy on the EBGP session to be		o apply an outbound BGP route policy on the EBGP session to be
	shutdown. This policy tags the paths propagated over the session		shutdown. This policy tags the paths propagated over the session
	with the GRACEFUL_SHUTDOWN community. This will trigger the BGP		with the GRACEFUL_SHUTDOWN community. This will trigger the BGP
	implementation to re-advertise all active routes previously		implementation to re-advertise all active routes previously
	advertised, and tag them with the GRACEFUL_SHUTDOWN community.		advertised, and tag them with the GRACEFUL_SHUTDOWN community.
	o apply an inbound BGP route policy on the maintained EBGP session		o apply an inbound BGP route policy on the EBGP session to be
	to tag the paths received over the session with the		shutdown. This policy tags the paths received over the session
	GRACEFUL_SHUTDOWN community.		with the GRACEFUL_SHUTDOWN community and sets LOCAL_PREF to a low
			value.
	o wait for convergence to happen.		o wait for convergence to happen.
	o shutdown the EBGP session, optionally using		o shutdown the EBGP session, optionally using
	[I-D.ietf-idr-shutdown] to communicate the reason of the shutdown.		[I-D.ietf-idr-shutdown] to communicate the reason of the shutdown.
	In the case of a shutdown of the whole router, in addition to the		In the case of a shutdown of the whole router, in addition to the
	graceful shutdown of all EBGP sessions, there is a need to graceful		graceful shutdown of all EBGP sessions, there is a need to graceful
	shutdown the routes originated by this router (e.g, BGP aggregates		shutdown the routes originated by this router (e.g, BGP aggregates
	redistributed from other protocols, including static routes). This		redistributed from other protocols, including static routes). This
	can be performed by tagging such routes with the GRACEFUL_SHUTDOWN		can be performed by tagging such routes with the GRACEFUL_SHUTDOWN
	community.		community and setting LOCAL_PREF to a low value.
	5.3. BGP implementation support for g-Shut		5.3. BGP implementation support for graceful shutdown
	A BGP router implementation MAY provide features aimed at automating		A BGP router implementation MAY provide features aimed at automating
	the application of the graceful shutdown procedures described above.		the application of the graceful shutdown procedures described above.
	Upon a session shutdown specified as graceful by the operator, a BGP		Upon a session shutdown specified as graceful by the operator, a BGP
	implementation supporting a graceful shutdown feature SHOULD:		implementation supporting a graceful shutdown feature SHOULD:
	1. Update all the paths propagated over the corresponding EBGP		1. Update all the paths propagated over the corresponding EBGP
	session, tagging the GRACEFUL_SHUTDOWN community to them. Any		session, tagging the GRACEFUL_SHUTDOWN community to them. Any
	subsequent update sent over the session being gracefully shut		subsequent update sent over the session being gracefully shut
	down would be tagged with the GRACEFUL_SHUTDOWN community.		down SHOULD be tagged with the GRACEFUL_SHUTDOWN community.
	2. Lower the LOCAL_PREF value of the paths received over the EBGP		2. Lower the LOCAL_PREF value of the paths received over the EBGP
	session being shut down.		session being shut down and set the GRACEFUL_SHUTDOWN community.
	3. Optionally shut down the session after a configured time.		3. Optionally shut down the session after a configured time.
	4. Prevent the GRACEFUL_SHUTDOWN community from being inherited by a		4. Prevent the GRACEFUL_SHUTDOWN community from being inherited by a
	path that would aggregate some paths tagged with the GSHUT		path that would aggregate some paths tagged with the GSHUT
	community. This behavior avoids the GSHUT procedure to be		community. This behavior avoids the GSHUT procedure to be
	applied to the aggregate upon the graceful shutdown of one of its		applied to the aggregate upon the graceful shutdown of one of its
	covered prefixes.		covered prefixes.
	A BGP implementation supporting a graceful shutdown feature SHOULD		A BGP implementation supporting a graceful shutdown feature SHOULD
	skipping to change at page 7, line 23 ¶		skipping to change at page 7, line 24 ¶
	6.1. IBGP graceful shutdown		6.1. IBGP graceful shutdown
	For the shutdown of an IBGP session, provided the IBGP topology is		For the shutdown of an IBGP session, provided the IBGP topology is
	viable after the maintenance of the session, i.e, if all BGP speakers		viable after the maintenance of the session, i.e, if all BGP speakers
	of the AS have an IBGP signaling path for all prefixes advertised on		of the AS have an IBGP signaling path for all prefixes advertised on
	this graceful shutdown IBGP session, then the shutdown of an IBGP		this graceful shutdown IBGP session, then the shutdown of an IBGP
	session does not lead to transient unreachability. As a consequence,		session does not lead to transient unreachability. As a consequence,
	no specific graceful shutdown action is required.		no specific graceful shutdown action is required.
	6.2. Link Up cases		6.2. EBGP session establishment
	We identify two potential causes for transient packet losses upon an		We identify two potential causes for transient packet losses upon the
	EBGP link up event. The first one is local to the graceful no-shut		establishment of an EBGP session. The first one is local to the
	initiator, the second one is due to the BGP convergence following the		startup initiator, the second one is due to the BGP convergence
	injection of new best paths within the IBGP topology.		following the injection of new best paths within the IBGP topology.
	6.2.1. Unreachability local to the ASBR		6.2.1. Unreachability local to the ASBR
	An ASBR that selects as best a path received over a newly brought up		An ASBR that selects as best a path received over a newly established
	EBGP session may transiently drop traffic. This can typically happen		EBGP session may transiently drop traffic. This can typically happen
	when the NEXT_HOP attribute differs from the IP address of the EBGP		when the NEXT_HOP attribute differs from the IP address of the EBGP
	peer, and the receiving ASBR has not yet resolved the MAC address		peer, and the receiving ASBR has not yet resolved the MAC address
	associated with the IP address of that "third party" NEXT_HOP.		associated with the IP address of that "third party" NEXT_HOP.
	A BGP speaker implementation could avoid such losses by ensuring that		A BGP speaker implementation may avoid such losses by ensuring that
	"third party" NEXT_HOPs are resolved before installing paths using		"third party" NEXT_HOPs are resolved before installing paths using
	these in the RIB.		these in the RIB.
	If the link up event corresponds to an EBGP session that is being		Alternatively, the operator (script) may ping third party NEXT_HOPs
	manually brought up, over an already up multi-access link, then the		that are expected to be used before establishing the session. By
	operator can ping third party NEXT_HOP that are expected to be used		proceeding like this, the MAC addresses associated with these third
	before actually bringing the session up, or ping directed broadcast		party NEXT_HOPs are resolved by the startup initiator.
	the subnet IP address of the link. By proceeding like this, the MAC
	addresses associated with these third party NEXT_HOP will be resolved
	by the graceful no-shut initiator.
	6.2.2. IBGP convergence		6.2.2. IBGP convergence
	Corner cases leading to LoC can occur during an EBGP link up event.		Corner cases leading to LoC can occur during the establishment of an
			EBGP session.
	A typical example for such transient unreachability for a given		A typical example for such transient unreachability for a given
	prefix is the following:		prefix is the following:
	Let's consider 3 route reflectors RR1, RR2, RR3. There is a full		Let's consider 3 route reflectors RR1, RR2, RR3. There is a full
	mesh of IBGP session between them.		mesh of IBGP sessions between them.
	1. RR1 is initially advertising the current best path to the		1. RR1 is initially advertising the current best path to the
	members of its IBGP RR full-mesh. It propagated that path within		members of its IBGP RR full-mesh. It propagated that path within
	its RR full-mesh. RR2 knows only that path toward the prefix.		its RR full-mesh. RR2 knows only that path toward the prefix.
	2. RR3 receives a new best path originated by the "graceful no-		2. RR3 receives a new best path originated by the startup
	shut" initiator, being one of its RR clients. RR3 selects it as		initiator, being one of its RR clients. RR3 selects it as best,
	best, and propagates an UPDATE within its RR full-mesh, i.e., to		and propagates an UPDATE within its RR full-mesh, i.e., to RR1 and
	RR1 and RR2.		RR2.
	3. RR1 receives that path, reruns its decision process, and picks		3. RR1 receives that path, reruns its decision process, and picks
	this new path as best. As a result, RR1 withdraws its previously		this new path as best. As a result, RR1 withdraws its previously
	announced best-path on the IBGP sessions of its RR full-mesh.		announced best-path on the IBGP sessions of its RR full-mesh.
	4. If, for any reason, RR3 processes the withdraw generated in		4. If, for any reason, RR3 processes the withdraw generated in
	step 3, before processing the update generated in step 2, RR3		step 3, before processing the update generated in step 2, RR3
	transiently suffers from unreachability for the affected prefix.		transiently suffers from unreachability for the affected prefix.
	The use of [I-D.ietf-idr-best-external] among the RR of the IBGP		The use of [I-D.ietf-idr-best-external] among the RR of the IBGP
	skipping to change at page 9, line 17 ¶		skipping to change at page 9, line 17 ¶
	By providing the graceful shutdown service to a neighboring AS, an		By providing the graceful shutdown service to a neighboring AS, an
	ISP provides means to this neighbor and possibly its downstream ASes		ISP provides means to this neighbor and possibly its downstream ASes
	to lower the LOCAL_PREF value assigned to the paths received from		to lower the LOCAL_PREF value assigned to the paths received from
	this neighbor.		this neighbor.
	The neighbor could abuse the technique and do inbound traffic		The neighbor could abuse the technique and do inbound traffic
	engineering by declaring some prefixes as undergoing a maintenance so		engineering by declaring some prefixes as undergoing a maintenance so
	as to switch traffic to another peering link.		as to switch traffic to another peering link.
	If this behavior is not tolerated by the ISP, it SHOULD monitor the		If this behavior is not tolerated by the ISP, it SHOULD monitor the
	use of the graceful shutdown community by this neighbor.		use of the graceful shutdown community.
	9. Acknowledgments		9. Acknowledgments
	The authors wish to thank Olivier Bonaventure, Pradosh Mohapatra and		The authors wish to thank Olivier Bonaventure, Pradosh Mohapatra, Job
	Job Snijders for their useful comments on this work.		Snijders and John Heasley for their useful comments.
	10. References		10. References
	10.1. Normative References		10.1. Normative References
	[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities		[RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities
	Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,		Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
	<http://www.rfc-editor.org/info/rfc1997>.		<http://www.rfc-editor.org/info/rfc1997>.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	skipping to change at page 11, line 21 ¶		skipping to change at page 11, line 21 ¶
	route-policy AS64497-ebgp-inbound		route-policy AS64497-ebgp-inbound
	! normally this policy would contain much more		! normally this policy would contain much more
	if community matches-any comm-graceful-shutdown then		if community matches-any comm-graceful-shutdown then
	set local-preference 0		set local-preference 0
	endif		endif
	end-policy		end-policy
	!		!
	router bgp 64496		router bgp 64496
	neighbor 2001:db8:1:2::1		neighbor 2001:db8:1:2::1
	remote-as 64497		remote-as 64497
	description a fantastic EBGP neighbor
	address-family ipv6 unicast		address-family ipv6 unicast
	send-community-ebgp		send-community-ebgp
	route-policy AS64497-ebgp-inbound in		route-policy AS64497-ebgp-inbound in
	route-policy AS65040v6-bgp-out out
	!		!
	!		!
	!		!
	B.2. BIRD		B.2. BIRD
	function honor_graceful_shutdown() {		function honor_graceful_shutdown() {
	if (65535, 0) ~ bgp_community then {		if (65535, 0) ~ bgp_community then {
	bgp_local_pref = 0;		bgp_local_pref = 0;
	}		}
	}		}
	filter AS64497_ebgp_inbound		filter AS64497_ebgp_inbound
	{		{
	# normally this policy would contain much more		# normally this policy would contain much more
	honor_graceful_shutdown();		honor_graceful_shutdown();
	}		}
	protocol bgp peer_64497_1 {		protocol bgp peer_64497_1 {
	description "a fantastic EBGP neighbor";
	neighbor 2001:db8:1:2::1 as 64497;		neighbor 2001:db8:1:2::1 as 64497;
	local as 64496;		local as 64496;
	import keep filtered;		import keep filtered;
	import filter AS64497_ebgp_inbound;		import filter AS64497_ebgp_inbound;
	export filter AS64497_ebgp_outbound;
	}		}
	B.3. OpenBGPD		B.3. OpenBGPD
	AS 64496		AS 64496
	router-id 192.0.2.1		router-id 192.0.2.1
	neighbor 2001:db8:1:2::1 {		neighbor 2001:db8:1:2::1 {
	descr "a fantastic EBGP neighbor"
	remote-as 64497		remote-as 64497
	}		}
	# normally this policy would contain much more		# normally this policy would contain much more
	match from any community GRACEFUL_SHUTDOWN set { localpref 0 }		match from any community GRACEFUL_SHUTDOWN set { localpref 0 }
	Authors' Addresses		Authors' Addresses
	Pierre Francois		Pierre Francois (editor)
	Individual Contributor		Individual Contributor
	Email: pfrpfr@gmail.com		Email: pfrpfr@gmail.com
	Bruno Decraene		Bruno Decraene (editor)
	Orange		Orange
	Email: bruno.decraene@orange.com		Email: bruno.decraene@orange.com
	Cristel Pelsser		Cristel Pelsser
	Strasbourg University		Strasbourg University
	Email: pelsser@unistra.fr		Email: pelsser@unistra.fr
	Keyur Patel		Keyur Patel
End of changes. 40 change blocks.
	69 lines changed or deleted		64 lines changed or added
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