draft-ietf-rtgwg-backoff-algo-02.txt		draft-ietf-rtgwg-backoff-algo-03.txt
	Network Working Group B. Decraene		Network Working Group B. Decraene
	Internet-Draft Orange		Internet-Draft Orange
	Intended status: Standards Track S. Litkowski		Intended status: Standards Track S. Litkowski
	Expires: June 19, 2016 Orange Business Service		Expires: January 5, 2017 Orange Business Service
	H. Gredler		H. Gredler
	Private Contributor		RtBrick Inc
	A. Lindem		A. Lindem
	P. Francois		P. Francois
	Cisco Systems		Cisco Systems
	December 17, 2015		C. Bowers
			Juniper Networks, Inc.
			July 4, 2016
	SPF Back-off algorithm for link state IGPs		SPF Back-off algorithm for link state IGPs
	draft-ietf-rtgwg-backoff-algo-02		draft-ietf-rtgwg-backoff-algo-03
	Abstract		Abstract
	This document defines a standard algorithm to back-off link-state IGP		This document defines a standard algorithm to back-off link-state IGP
	SPF computations.		SPF computations.
	Having one standard algorithm improves interoperability by reducing		Having one standard algorithm improves interoperability by reducing
	the probability and/or duration of transient forwarding loops during		the probability and/or duration of transient forwarding loops during
	the IGP convergence when the IGP reacts to multiple proximate IGP		the IGP convergence when the IGP reacts to multiple proximate IGP
	events.		events.
	skipping to change at page 1, line 47 ¶		skipping to change at page 2, line 4 ¶
	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 5, 2017.
	This Internet-Draft will expire on June 19, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2016 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
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	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
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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. High level goals . . . . . . . . . . . . . . . . . . . . . . 3		2. High level goals . . . . . . . . . . . . . . . . . . . . . . 3
	3. Definitions and parameters . . . . . . . . . . . . . . . . . 3		3. Definitions and parameters . . . . . . . . . . . . . . . . . 4
	4. Principles of SPF delay algorithm . . . . . . . . . . . . . . 4		4. Principles of SPF delay algorithm . . . . . . . . . . . . . . 4
	5. Specification of the SPF delay algorithm . . . . . . . . . . 5		5. Specification of the SPF delay state machine . . . . . . . . 5
	6. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 6		5.1. States . . . . . . . . . . . . . . . . . . . . . . . . . 5
	7. Impact on micro-loops . . . . . . . . . . . . . . . . . . . . 6		5.2. States Transitions . . . . . . . . . . . . . . . . . . . 6
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7		5.3. FSM Events . . . . . . . . . . . . . . . . . . . . . . . 7
	9. Security considerations . . . . . . . . . . . . . . . . . . . 7		6. Parameters . . . . . . . . . . . . . . . . . . . . . . . . . 8
	10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7		7. Impact on micro-loops . . . . . . . . . . . . . . . . . . . . 9
	11. References . . . . . . . . . . . . . . . . . . . . . . . . . 7		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
	11.1. Normative References . . . . . . . . . . . . . . . . . . 7		9. Security considerations . . . . . . . . . . . . . . . . . . . 9
	11.2. Informative References . . . . . . . . . . . . . . . . . 7		10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8		11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
			11.1. Normative References . . . . . . . . . . . . . . . . . . 9
			11.2. Informative References . . . . . . . . . . . . . . . . . 9
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
	1. Introduction		1. Introduction
	Link state IGPs, such as IS-IS [ISO10589-Second-Edition] and OSPF		Link state IGPs, such as IS-IS [ISO10589-Second-Edition] and OSPF
	[RFC2328], perform distributed route computation on all routers of		[RFC2328], perform distributed route computation on all routers in
	the area/level. In order to have consistent routing tables across		the area/level. In order to have consistent routing tables across
	the network, such distributed computation requires that all routers		the network, such distributed computation requires that all routers
	have the same version of the network topology (Link State DataBase		have the same version of the network topology (Link State DataBase
	(LSDB)) and perform their computation at the same time.		(LSDB)) and perform their computation at the same time.
	In general, when the network is stable, there is a desire to compute		In general, when the network is stable, there is a desire to compute
	the new SPF as soon as the failure is detected in order to quickly		a new SPF as soon as a failure is detected in order to quickly route
	route around the failure. However, when the network is experiencing		around the failure. However, when the network is experiencing
	multiple proximate failures over a short period of time, there is a		multiple proximate failures over a short period of time, there is a
	conflicting desire to limit the frequency of SPF computations.		conflicting desire to limit the frequency of SPF computations.
	Indeed, this allows a reduction in control plane resources used by		Indeed, this allows a reduction in control plane resources used by
	IGPs and all protocols/subsystem reacting on the attendant route		IGPs and all protocols/subsystems reacting on the attendant route
	change, such as LDP, RSVP-TE, BGP, Fast ReRoute computations, FIB		change, such as LDP, RSVP-TE, BGP, Fast ReRoute computations, FIB
	updates... This will reduce the churn on routers and in the network		updates... This also reduces the churn on routers and in the network
	and, in particular, reduce the side effects such as micro-loops that		and, in particular, reduces the side effects such as micro-loops that
	ensue during IGP convergence.		ensue during IGP convergence.
	To allow for this, IGPs implement a SPF back-off algorithm.		To allow for this, IGPs implement an SPF back-off algorithm.
	Different implementations choose different algorithms. Hence, in a		However, different implementations have choosen different algorithms.
	multi-vendor network, it's not possible to ensure that all routers		Hence, in a multi-vendor network, it's not possible to ensure that
	trigger their SPF computation after the same delay. This situation		all routers trigger their SPF computation after the same delay. This
	increases the average differential delay between routers completing		situation increases the average differential delay between routers
	their SPF computation. It also increases the probability that		completing their SPF computation. It also increases the probability
	different routers compute their FIBs based on a different LSDB		that different routers compute their FIBs based on different LSDB
	versions. Both factors increase the probability and/or duration of		versions. Both factors increase the probability and/or duration of
	micro-loops.		micro-loops.
	To allow multi-vendor networks to have all routers delay their SPF		To allow multi-vendor networks to have all routers delay their SPF
	computations for the same duration, this document specifies a		computations for the same duration, this document specifies a
	standard algorithm. Optionally, implementations may offer		standard algorithm. Optionally, implementations may offer
	alternative algorithms.		alternative algorithms.
	2. High level goals		2. High level goals
	The high level goals of this algorithm are the following:		The high level goals of this algorithm are the following:
	o Very fast convergence for a single event (e.g., link failure).		o Very fast convergence for a single event (e.g., link failure).
	o Slightly paced fast convergence for multiple proximate IGP events		o Paced fast convergence for multiple proximate IGP events while IGP
	while IGP stability is considered acceptable.		stability is considered acceptable.
	o Delayed convergence when the IGP stability is problematic. This		o Delayed convergence when IGP stability is problematic. This will
	will allow the IGP and related processes to conserve resources		allow the IGP and related processes to conserve resources during
	during the period of instability.		the period of instability.
	o Always try to avoid different SPF_DELAY timers values across		o Always try to avoid different SPF_DELAY timers values across
	different routers in the area/level. Even though not all routers		different routers in the area/level. Even though not all routers
	will receive IGP messages at the same time (due to differences		will receive IGP messages at the same time, due to differences
	both in the distance from the originator of the IGP event and in		both in the distance from the originator of the IGP event and in
	flooding implementations).		flooding implementations.
	3. Definitions and parameters		3. Definitions and parameters
	IGP events: An IGP LSDB change requiring a new routing table		IGP events: The reception or origination of an IGP LSDB change
	computation. Examples are a topology change, a prefix change, a		requiring a new routing table computation. Examples are a topology
	metric change on link or prefix...		change, a prefix change, a metric change on a link or prefix... Note
			that locally triggering a routing table computation is not considered
			as an IGP event since other IGP routers are unaware of this
			occurrence.
	Routing table computation: computation of the routing table, by the		Routing table computation: Computation of the routing table, by the
	IGP, using the IGP LSDB. No distinction is made between the type of		IGP, using the IGP LSDB. No distinction is made between the type of
	computation performed. e.g., full SPF, incremental SPF, Partial Route		computation performed. e.g., full SPF, incremental SPF, Partial Route
	Computation (PRC). The type of computation is a local consideration.		Computation (PRC). The type of computation is a local consideration.
	This document may indifferently use the terms routing table		This document may interchangeably use the terms routing table
	computation or SPF computation.		computation and SPF computation.
	The SPF_DELAY is the delay introduced between the IGP event and the		SPF_DELAY: The delay between the first IGP event triggering a new
	start of the routing table computation. It can take the following		routing table computation and the start of that routing table
	values:		computation. It can take the following values:
	INITIAL_WAIT: a very small delay to quickly handle link failure,		INITIAL_SPF_DELAY: A very small delay to quickly handle link
	e.g., 0 milliseconds.		failure, e.g., 0 milliseconds.
	FAST_WAIT: a small delay to have a fast convergence in case of		SHORT_SPF_DELAY: A small delay to have a fast convergence in case of
	single component failure (node, SRLG..), e.g., 50-100 milliseconds.		a single component failure (node, SRLG..), e.g., 50-100
	Note: we want to be fast, but as this failure results in multiple		milliseconds.
	IGP events, being too fast increases the probability to receive
	additional network events immediately after the SPF computation.
	LONG_WAIT: a long delay when the IGP is unstable, e.g., 2 seconds.		LONG_SPF_DELAY: A long delay when the IGP is unstable, e.g., 2
	Note: Allow the IGP network to stabilize.		seconds. Note that this allows the IGP network to stabilize.
	The TIME_TO_LEARN timer is the maximum duration typically needed to		TIME_TO_LEARN_INTERVAL: This is the maximum duration typically needed
	learn all the IGP events related to a single component failure (e.g.,		to learn all the IGP events related to a single component failure
	router failure, SRLG failure), e.g., 1 second. It's mostly dependent		(e.g., router failure, SRLG failure), e.g., 1 second. It's mostly
	on variation of failure detection times between all routers that are		dependent on failure detection time variation between all routers
	adjacent to the failure. Additionally, it may depend on the		that are adjacent to the failure. Additionally, it may depend on the
	different flooding implementations for routers in the network.		different IGP implementations across the network, related to
			origination and flooding of their link state advertisements.
	The HOLD_DOWN timer is the time needed with no received IGP events		HOLD_DOWN_INTERVAL: The time required with no received IGP events
	before considering the IGP to be stable again, allowing the SPF_DELAY		before considering the IGP to be stable again and allowing the
	to be restored to INITIAL_WAIT. e.g., 3 seconds.		SPF_DELAY to be restored to INITIAL_WAIT. e.g., 3 seconds.
	4. Principles of SPF delay algorithm		4. Principles of SPF delay algorithm
	For this first IGP event, we assume that there has been a single		For this first IGP event, we assume that there has been a single
	simple change in the network which can be taken into account using a		simple change in the network which can be taken into account using a
	single routing computation (e.g., link failure, prefix (metric)		single routing computation (e.g., link failure, prefix (metric)
	change) and we optimize for very fast convergence, delaying the		change) and we optimize for very fast convergence, delaying the
	routing computation by INITIAL_WAIT. Under this assumption, there is		routing computation by INITIAL_SPF_DELAY. Under this assumption,
	no benefit in delaying the routing computation. In a typical		there is no benefit in delaying the routing computation. In a
	network, this is the most common type of IGP event. Hence, it makes		typical network, this is the most common type of IGP event. Hence,
	sense to optimize this case.		it makes sense to optimize this case.
	If subsequent IGP events are received in a short period of time		If subsequent IGP events are received in a short period of time
	(TIME_TO_LEARN), we then assume that a single component failed, but		(TIME_TO_LEARN_INTERVAL), we then assume that a single component
	that this failure requires the knowledge of multiple IGP events in		failed, but that this failure requires the knowledge of multiple IGP
	order for the IGP routing to converge. Under this assumption, we		events in order for IGP routing to converge. Under this assumption,
	want fast convergence since this is a normal network situation.		we want fast convergence since this is a normal network situation.
	However, there is a benefit in waiting for all IGP events related to		However, there is a benefit in waiting for all IGP events related to
	this single component failure so that the IGP can compute the post-		this single component failure so that the IGP can compute the post-
	failure routing table in a single route computation. In this		failure routing table in a single route computation. In this
	situation, we delay the routing computation by FAST_WAIT.		situation, we delay the routing computation by LONG_WAIT.
	If IGP events are still received after TIME_TO_LEARN seconds from the		If IGP events are still received after TIME_TO_LEARN_INTERVAL from
	initial IGP event, then the network is presumably experiencing		the initial IGP event received in QUIET state, then the network is
	multiple independent failures and while waiting for network		presumably experiencing multiple independent failures. In this case,
	stability, the computations are delayed for a longer time represented		while waiting for network stability, the computations are delayed for
	by LONG_WAIT. This SPF_delay is kept until no IGP events are		a longer time represented by LONG_SPF_DELAY. This SPF delay is kept
	received for HOLD_DOWN seconds.		until no IGP events are received for HOLDDOWN_INTERVAL.
	Note: previous SPF delay algorithms used to count the number of SPF		Note that previous SPF delay algorithms used to count the number of
	computations. However, as all routers may receive the IGP events at		SPF computations. However, as all routers may receive the IGP events
	different times, we cannot assume that all routers will perform the		at different times, we cannot assume that all routers will perform
	same number of SPF computations or that they will schedule them at		the same number of SPF computations or that they will schedule them
	the same time. For example, assuming that the SPF delay is 50 ms,		at the same time. For example, assuming that the SPF delay is 50 ms,
	router R1 may receive 3 IGP events (E1, E2, E3) in those 50 ms and		router R1 may receive 3 IGP events (E1, E2, E3) in those 50 ms and
	hence will perform a single routing computation. While another		hence will perform a single routing computation. While another
	router R2 may only receive 2 events (E1, E2) in those 50 ms and hence		router R2 may only receive 2 events (E1, E2) in those 50 ms and hence
	will schedule another routing computation when receiving E3. That's		will schedule another routing computation when receiving E3. That's
	why this document defines a time (TIME_TO_LEARN) from the initial		why this document uses a time (TIME_TO_LEARN) from the initial event
	event detection/reception as opposed to defining the number of SPF		detection/reception as opposed to counting the number of SPF
	computations to determine when the IGP is unstable.		computations to determine when the IGP is unstable.
	5. Specification of the SPF delay algorithm		5. Specification of the SPF delay state machine
	When no IGP events have occurred during the HOLD_DOWN interval:		5.1. States
	o The IGP is set to the QUIET state.		This section describes the state machine. The naming and semantics
			of each state corresponds directly to the SPF delay used for IGP
			events received in that state. Three states are defined:
	When the IGP is in the QUIET state and an IGP event is received:		QUIET: This is the initial state, when no IGP events have occured for
			at least HOLDDOWN_INTERVAL since the previous routing table
			computation. The state is meant to handle link failures very
			quickly.
	o The time of this first IGP event is stored in FIRST_EVENT_TIME.		SHORT_WAIT: State entered when an IGP event has been received in
			QUIET state and exited when no IGP events have been received for
			HOLDDOWN_TIMER. This state is meant to handle single component
			failure requiring multiple IGP events (e.g., node, SRLG).
	o The next routing table computation is scheduled at: this IGP event		LONG_WAIT: State reached after TIME_TO_LEARN_INTERVAL. In other
	received time + INITIAL_WAIT.		words, state reached after TIME_TO_LEARN_INTERVAL in state
			SHORT_WAIT. This state is meant to handle multiple independent
			component failures during periods of IGP instability.
	o The IGP is set to the FAST_WAIT state.		5.2. States Transitions
	When the IGP is in the FAST_WAIT state and an IGP event is received:		The FSM is initialized to the QUIET_STATE with all three timers
			deactivated. The following diagram describes briefly the state
			transitions.
	o If more than the TIME_TO_LEARN interval has passed since		+-------------------+
	FIRST_EVENT_TIME, then the IGP is set to the HOLD_DOWN state.		| |<-------------------+
			| QUIET | |
			| |<---------+ |
			+-------------------+ | |
			| | |
			| | |
			| 1: IGP event | |
			| | |
			v | |
			+-------------------+ | |
			+---->| | | |
			| | SHORT_WAIT |----->----+ |
			+-----| | |
			2: +-------------------+ 6: HOLDDOWN_TIMER |
			IGP event | expiration |
			| |
			| |
			| 3: LEARN_TIMER |
			| expiration |
			| |
			v |
			+-------------------+ |
			+---->| | |
			| | LONG_WAIT |------------>-------+
			+-----| |
			4: +-------------------+ 5: HOLDDOWN_TIMER
			IGP event expiration
	o If a routing table computation is not already scheduled, one is		Figure 1: State Machine
	scheduled at: this IGP event received time + FAST_WAIT.
	When the IGP is in the HOLD_DOWN state and an IGP event is received:		5.3. FSM Events
	o If a routing table computation is not already scheduled, one is		This section describes the events and the actions performed in
	scheduled at: this IGP event received time + LONG_WAIT.		response.
			Event 1: IGP events, while in QUIET_STATE.
			Actions on event 1:
			o If SPF_TIMER is not already running, start it with value
			INITIAL_SPF_DELAY.
			o Start LEARN_TIMER with TIME_TO_LEARN_INTERVAL.
			o Start HOLDDOWN_TIMER with HOLDDOWN_INTERVAL.
			o Transition to SHORT_WAIT state.
			Event 2: IGP events, while in SHORT_WAIT.
			Actions on event 2:
			o Reset HOLDDOWN_TIMER to HOLDDOWN_INTERVAL.
			o If SPF_TIMER is not already running, start it with value
			SHORT_SPF_DELAY.
			o Remain in current state.
			Event 3: LEARN_TIMER expiration.
			Actions on event 3:
			o Transition to LONG_WAIT state.
			Event 4: IGP events, while in LONG_WAIT.
			Actions on event 4:
			o Reset HOLDDOWN_TIMER to HOLDDOWN_INTERVAL.
			o If SPF_TIMER is not already running, start it with value
			LONG_SPF_DELAY.
			o Remain in current state.
			Event 5: HOLDDOWN_TIMER expiration, while in LONG_WAIT.
			Actions on event 5:
			o Transition to QUIET state.
			Event 6: HOLDDOWN_TIMER expiration, while in SHORT_WAIT.
			Actions on event 6:
			o Deactivate LEARN_TIMER.
			o Transition to QUIET state.
	6. Parameters		6. Parameters
	All the parameters MUST be configurable. All the delays		All the parameters MUST be configurable. All the delays
	(INITIAL_WAIT, FAST_WAIT, LONG_WAIT, TIME_TO_LEARN, HOLD_DOWN) SHOULD		(INITIAL_SPF_DELAY, SHORT_SPF_DELAY, LONG_SPF_DELAY,
	be configurable at the millisecond granularity. They MUST be		TIME_TO_LEARN_INTERVAL, HOLD_DOWN_INTERVAL) SHOULD be configurable at
	configurable at least at the tenth of second granularity. The		the millisecond granularity. They MUST be configurable at least at
	configurable range for all the parameters SHOULD be at least from 0		the tenth of second granularity. The configurable range for all the
	milliseconds to 60 seconds.		parameters SHOULD at least be from 0 milliseconds to 60 seconds.
	This document does not propose default values for the parameters		This document does not propose default values for the parameters
	because these values are expected to be context dependent.		because these values are expected to be context dependent.
	Implementations are free to propose their own default values.		Implementations are free to propose their own default values.
	When setting the (default) values, one SHOULD consider the customer's		When setting (default) values, one SHOULD consider the customers and
	or their applications' requirements, the computational power of the		their application requirements, the computational power of the
	routers, the size of the network, and, in particular, the number of		routers, the size of the network, and, in particular, the number of
	IP prefixes advertised in the IGP, the frequency and number of IGP		IP prefixes advertised in the IGP, the frequency and number of IGP
	events, the number of protocols reactions/computations triggered by		events, the number of protocols reactions/computations triggered by
	IGP SPF (e.g., BGP, PCEP, Traffic Engineering CSPF, Fast ReRoute		IGP SPF (e.g., BGP, PCEP, Traffic Engineering CSPF, Fast ReRoute
	computations).		computations).
	Note that some or all of these factors may change over the life of		Note that some or all of these factors may change over the life of
	the network. In case of doubt, it's RECOMMENDED to play it safe and		the network. In case of doubt, it's RECOMMENDED to play it safe and
	start with safe, i.e., longer timers.		start with safe, i.e., longer timers.
	skipping to change at page 6, line 46 ¶		skipping to change at page 9, line 13 ¶
	values.		values.
	7. Impact on micro-loops		7. Impact on micro-loops
	Micro-loops during IGP convergence are due to a non-synchronized or		Micro-loops during IGP convergence are due to a non-synchronized or
	non-ordered update of the forwarding information tables (FIB)		non-ordered update of the forwarding information tables (FIB)
	[RFC5715] [RFC6976] [I-D.ietf-rtgwg-spf-uloop-pb-statement]. FIBs		[RFC5715] [RFC6976] [I-D.ietf-rtgwg-spf-uloop-pb-statement]. FIBs
	are installed after multiple steps such as SPF wait time, SPF		are installed after multiple steps such as SPF wait time, SPF
	computation, FIB distribution, and FIB update. This document only		computation, FIB distribution, and FIB update. This document only
	addresses the first contribution. This standardized procedure		addresses the first contribution. This standardized procedure
	reduces the probability and/or duration of micro-loops when the IGP		reduces the probability and/or duration of micro-loops when IGPs
	experience multiple proximate events. It does not prevent all micro-		experience multiple proximate events. It does not prevent all micro-
	loops. However, it is beneficial and its cost seems limited compared		loops. However, it is beneficial and is less complex and costly to
	to full solutions such as [RFC5715] or [RFC6976].		implement when compared to full solutions such as [RFC5715] or
			[RFC6976].
	8. IANA Considerations		8. IANA Considerations
	No IANA actions required.		No IANA actions required.
	9. Security considerations		9. Security considerations
	This algorithm presented in this document does not in any way		The algorithm presented in this document does not compromise IGP
	compromise the security of the IGP. In fact, the HOLD_DOWN state may		security. An attacker having the ability to generate IGP events
	mitigate the effects of Denial-of-Service (DOS) attacks generating		would be able to delay the IGP convergence time. The LONG_SPF_DELAY
	many IGP events.		state may help mitigate the effects of Denial-of-Service (DOS)
			attacks generating many IGP events.
	10. Acknowledgements		10. Acknowledgements
	We would like to acknowledge Les Ginsberg, Uma Chunduri, and Mike		We would like to acknowledge Les Ginsberg, Uma Chunduri, and Mike
	Shand for the discussions and comments related to this document.		Shand for the discussions and comments related to this document.
	11. References		11. References
	11.1. Normative References		11.1. Normative References
	skipping to change at page 8, line 15 ¶		skipping to change at page 10, line 31 ¶
	[RFC6976] Shand, M., Bryant, S., Previdi, S., Filsfils, C.,		[RFC6976] Shand, M., Bryant, S., Previdi, S., Filsfils, C.,
	Francois, P., and O. Bonaventure, "Framework for Loop-Free		Francois, P., and O. Bonaventure, "Framework for Loop-Free
	Convergence Using the Ordered Forwarding Information Base		Convergence Using the Ordered Forwarding Information Base
	(oFIB) Approach", RFC 6976, DOI 10.17487/RFC6976, July		(oFIB) Approach", RFC 6976, DOI 10.17487/RFC6976, July
	2013, <http://www.rfc-editor.org/info/rfc6976>.		2013, <http://www.rfc-editor.org/info/rfc6976>.
	Authors' Addresses		Authors' Addresses
	Bruno Decraene		Bruno Decraene
	Orange		Orange
	38 rue du General Leclerc
	Issy Moulineaux cedex 9 92794
	France
	Email: bruno.decraene@orange.com		Email: bruno.decraene@orange.com
	Stephane Litkowski		Stephane Litkowski
	Orange Business Service		Orange Business Service
	Email: stephane.litkowski@orange.com		Email: stephane.litkowski@orange.com
	Hannes Gredler		Hannes Gredler
	Private Contributor		RtBrick Inc
	Email: hannes@gredler.at
			Email: hannes@rtbrick.com
	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
	Pierre Francois		Pierre Francois
	Cisco Systems		Cisco Systems
	Email: pifranco@cisco.com		Email: pifranco@cisco.com
			Chris Bowers
			Juniper Networks, Inc.
			1194 N. Mathilda Ave.
			Sunnyvale, CA 94089
			US
			Email: cbowers@juniper.net
End of changes. 53 change blocks.
	123 lines changed or deleted		219 lines changed or added
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