< draft-ietf-bfd-yang-00.txt		draft-ietf-bfd-yang-01.txt >
	Network Working Group L. Zheng, Ed.		Network Working Group L. Zheng, Ed.
	Internet-Draft Huawei Technologies		Internet-Draft Huawei Technologies
	Intended status: Standards Track R. Rahman, Ed.		Intended status: Standards Track R. Rahman, Ed.
	Expires: February 20, 2016 Cisco Systems		Expires: August 20, 2016 Cisco Systems
	S. Pallagatti		S. Pallagatti
	Juniper Networks
	M. Jethanandani		M. Jethanandani
	Cisco Systems		Cisco Systems
	G. Mirsky		G. Mirsky
	Ericsson		Ericsson
	August 19, 2015		February 17, 2016
	Yang Data Model for Bidirectional Forwarding Detection (BFD)		Yang Data Model for Bidirectional Forwarding Detection (BFD)
	draft-ietf-bfd-yang-00.txt		draft-ietf-bfd-yang-01.txt
	Abstract		Abstract
	This document defines a YANG data model that can be used to configure		This document defines a YANG data model that can be used to configure
	and manage Bidirectional Forwarding Detection (BFD).		and manage Bidirectional Forwarding Detection (BFD).
	Requirements Language		Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	skipping to change at page 1, line 44 ¶		skipping to change at page 1, line 44 ¶
	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 February 20, 2016.		This Internet-Draft will expire on August 20, 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.
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	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
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	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.1. Contributors . . . . . . . . . . . . . . . . . . . . . . 3		1.1. Contributors . . . . . . . . . . . . . . . . . . . . . . 4
	2. Design of the Data Model . . . . . . . . . . . . . . . . . . 3		2. Design of the Data Model . . . . . . . . . . . . . . . . . . 4
	2.1. Design of Configuration Model . . . . . . . . . . . . . . 4		2.1. Design of Configuration Model . . . . . . . . . . . . . . 4
	2.1.1. Single-hop IP . . . . . . . . . . . . . . . . . . . . 4		2.1.1. Common BFD configuration parameters . . . . . . . . . 5
	2.1.2. Multi-hop IP . . . . . . . . . . . . . . . . . . . . 5		2.1.2. Single-hop IP . . . . . . . . . . . . . . . . . . . . 6
	2.1.3. Traffic Engineering Tunnels . . . . . . . . . . . . . 6		2.1.3. Multi-hop IP . . . . . . . . . . . . . . . . . . . . 6
	2.1.4. LDP Label Switched Paths . . . . . . . . . . . . . . 6		2.1.4. MPLS Traffic Engineering Tunnels . . . . . . . . . . 6
	2.1.5. Link Aggregation Groups . . . . . . . . . . . . . . . 6		2.1.5. MPLS Label Switched Paths . . . . . . . . . . . . . . 7
	2.1.6. Per-interface Configuration . . . . . . . . . . . . . 7		2.1.6. Link Aggregation Groups . . . . . . . . . . . . . . . 7
	2.2. Design of Operational Model . . . . . . . . . . . . . . . 7		2.2. Design of Operational Model . . . . . . . . . . . . . . . 7
	2.3. Notifications . . . . . . . . . . . . . . . . . . . . . . 8		2.3. Notifications . . . . . . . . . . . . . . . . . . . . . . 8
	2.4. RPC Operations . . . . . . . . . . . . . . . . . . . . . 8		2.4. RPC Operations . . . . . . . . . . . . . . . . . . . . . 8
	2.5. BFD Configuration Data Hierarchy . . . . . . . . . . . . 8		2.5. BFD top level hierarchy . . . . . . . . . . . . . . . . . 8
	2.5.1. Centralized BFD Configuration . . . . . . . . . . . . 8		2.6. BFD IP single-hop hierarchy . . . . . . . . . . . . . . . 9
	2.5.2. Configuration in BFD clients . . . . . . . . . . . . 9		2.7. BFD IP multi-hop hierarchy . . . . . . . . . . . . . . . 11
	2.6. Operational Data Hierarchy . . . . . . . . . . . . . . . 11		2.8. BFD over LAG hierarchy . . . . . . . . . . . . . . . . . 13
	2.7. Notifications . . . . . . . . . . . . . . . . . . . . . . 14		2.9. BFD over MPLS LSPs hierarchy . . . . . . . . . . . . . . 15
	2.8. Examples . . . . . . . . . . . . . . . . . . . . . . . . 16		2.10. BFD over MPLS-TE hierarchy . . . . . . . . . . . . . . . 17
	2.9. Interaction with other YANG modules . . . . . . . . . . . 16		2.11. Examples . . . . . . . . . . . . . . . . . . . . . . . . 19
	2.10. BFD Yang Module . . . . . . . . . . . . . . . . . . . . . 16		2.12. Interaction with other YANG modules . . . . . . . . . . . 19
	2.11. BFD Client Example Configuration Yang Module . . . . . . 31		2.13. BFD top-level Yang Module . . . . . . . . . . . . . . . . 19
	2.12. Security Considerations . . . . . . . . . . . . . . . . . 33		2.14. BFD IP single-hop Yang Module . . . . . . . . . . . . . . 32
	2.13. IANA Considerations . . . . . . . . . . . . . . . . . . . 33		2.15. BFD IP multi-hop Yang Module . . . . . . . . . . . . . . 35
	2.14. Acknowledgements . . . . . . . . . . . . . . . . . . . . 33		2.16. BFD over LAG Yang Module . . . . . . . . . . . . . . . . 38
	3. References . . . . . . . . . . . . . . . . . . . . . . . . . 33		2.17. BFD over MPLS Yang Module . . . . . . . . . . . . . . . . 41
	3.1. Normative References . . . . . . . . . . . . . . . . . . 33		2.18. BFD over MPLS-TEYang Module . . . . . . . . . . . . . . . 45
	3.2. Informative References . . . . . . . . . . . . . . . . . 34		2.19. Security Considerations . . . . . . . . . . . . . . . . . 47
	Appendix A. Change log . . . . . . . . . . . . . . . . . . . . . 35		2.20. IANA Considerations . . . . . . . . . . . . . . . . . . . 47
	A.1. Changes between versions -03 and -04 . . . . . . . . . . 35		2.21. Acknowledgements . . . . . . . . . . . . . . . . . . . . 47
	A.2. Changes between versions -02 and -03 . . . . . . . . . . 35		3. References . . . . . . . . . . . . . . . . . . . . . . . . . 47
	A.3. Changes between versions -01 and -02 . . . . . . . . . . 35		3.1. Normative References . . . . . . . . . . . . . . . . . . 47
	A.4. Changes between versions -00 and -01 . . . . . . . . . . 35		3.2. Informative References . . . . . . . . . . . . . . . . . 49
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35		Appendix A. Change log . . . . . . . . . . . . . . . . . . . . . 49
			A.1. Changes between versions -00 and -01 . . . . . . . . . . 49
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 50
	1. Introduction		1. Introduction
	YANG [RFC6020] is a data definition language that was introduced to		YANG [RFC6020] is a data definition language that was introduced to
	define the contents of a conceptual data store that allows networked		define the contents of a conceptual data store that allows networked
	devices to be managed using NETCONF [RFC6241]. YANG is proving		devices to be managed using NETCONF [RFC6241]. YANG is proving
	relevant beyond its initial confines, as bindings to other interfaces		relevant beyond its initial confines, as bindings to other interfaces
	(e.g RESTCONF [I-D.ietf-netconf-restconf]) and encodings other than		(e.g RESTCONF [I-D.ietf-netconf-restconf]) and encodings other than
	XML (e.g JSON) are being defined. Furthermore, YANG data models can		XML (e.g JSON) are being defined. Furthermore, YANG data models can
	be used as the basis of implementation for other interfaces, such as		be used as the basis of implementation for other interfaces, such as
	skipping to change at page 3, line 33 ¶		skipping to change at page 3, line 35 ¶
	over which we have BFD:		over which we have BFD:
	1) Two systems directly connected via IP. This is known as BFD over		1) Two systems directly connected via IP. This is known as BFD over
	single-hop IP [RFC5881]		single-hop IP [RFC5881]
	2) Two systems connected via multiple hops [RFC5883]		2) Two systems connected via multiple hops [RFC5883]
	3) Two systems connected via MPLS Label Switched Paths (LSPs)		3) Two systems connected via MPLS Label Switched Paths (LSPs)
	[RFC5884]		[RFC5884]
	4) Two systems connected via a Link Aggregation Group (LAG) interface		4) Two systems connected via pseudowires (PWs), this is known as
			Virtual Circuit Connectivity Verification (VCCV) [RFC5885]
			5) Two systems connected via a Link Aggregation Group (LAG) interface
	[RFC7130]		[RFC7130]
	BFD typically does not operate on its own. Various control		BFD typically does not operate on its own. Various control
	protocols, also known as BFD clients, use the services provided by		protocols, also known as BFD clients, use the services provided by
	BFD for their own operation [RFC5882]. The obvious candidates which		BFD for their own operation [RFC5882]. The obvious candidates which
	use BFD are those which do not have Hellos to detect failures, e.g.		use BFD are those which do not have Hellos to detect failures, e.g.
	static routes, and routing protocols whose Hellos do not suport sub-		static routes, and routing protocols whose Hellos do not support sub-
	second failure detection, e.g. OSPF and IS-IS.		second failure detection, e.g. OSPF and IS-IS.
	1.1. Contributors		1.1. Contributors
	2. Design of the Data Model		2. Design of the Data Model
	The BFD YANG data model follows a VRF-centric model by augmenting the		Since BFD is used for liveliness detection of various forwarding
	"routing-protocol" data node in [I-D.ietf-netmod-routing-cfg].		paths, there is no uniform key to identify a BFD session. So the BFD
			data model is split in multiple YANG modules where each module
			corresponds to one type of forwarding path. For example, BFD for IP
			single-hop is in one YANG module and BFD for MPLS-TE is in another
			YANG module. The main difference between these modules is how a BFD
			session is uniquely identified, i.e the key for the list containing
			the BFD sessions for that forwarding path. To avoid duplication of
			BFD definitions, we have common types and groupings which are used by
			all the modules.
			The new top-level container "bfd" is augmented by all the YANG
			modules for their respective specific information.
			The "routing-protocol" data node in [I-D.ietf-netmod-routing-cfg] has
			been augmented with the "bfd" data node. Where appropriate for
			specific types of forwarding path, the respective BFD YANG modules
			follow a VRF-centric model by augmenting that new "bfd" node under
			"routing-protocol".
			Each node in every "bfd" sub-tree has a "config" node and an "oper"
			node.
	2.1. Design of Configuration Model		2.1. Design of Configuration Model
	The configuration model consists mainly of the parameters specified		The configuration model consists mainly of the parameters specified
	in [RFC5880]. Some examples are desired minimum transmit interval,		in [RFC5880]. Some examples are desired minimum transmit interval,
	required minimum receive interval, detection multiplier, etc		required minimum receive interval, detection multiplier, etc
	Some implementations have BFD session configuration under the BFD		Some implementations have BFD session configuration under the BFD
	clients. For example, BFD session configuration is under routing		clients. For example, BFD session configuration is under routing
	applications such as OSPF, IS-IS, BGP etc. Other implementations		applications such as OSPF, IS-IS, BGP etc. Other implementations
	have BFD session configuration centralized under BFD, i.e. outside		have BFD session configuration centralized under BFD, i.e. outside
	the multiple BFD clients.		the multiple BFD clients.
	The BFD parameters of interest to a BFD client are mainly the		The BFD parameters of interest to a BFD client are mainly the
	multiplier and interval(s) since those parameters impact the		multiplier and interval(s) since those parameters impact the
	convergence time of the BFD clients when a failure occurs. So the		convergence time of the BFD clients when a failure occurs. Other
	configuration model has groupings, containing multiplier and		parameters such as BFD authentication are not specific to the
	interval(s), which are to be used by BFD clients. Other parameters		requirements of the BFD client. To avoid splitting the BFD
	which remain under BFD control, e.g. demand mode and authentication,		configuration between BFD clients and BFD, all the configuration is
	are configured under BFD.		under BFD. The only BFD configuration under BFD clients should be an
			"enable" knob which makes those clients react to BFD liveliness
			detection events.
	We provide groupings, which contain the basic BFD session parameters,		2.1.1. Common BFD configuration parameters
	for applications to use. This ensures consistency of BFD parameters
	across applications.
	Although [RFC5880] allows for different values for transmit and		The basic BFD configuration parameters are:
	receive intervals, many implementations allow users to specify just
	one interval which is used for both transmit and receive intervals or
	separate values for transmit and receive intervals. Our YANG model
	supports this: there is a choice between "min-interval", used for
	both transmit and receive intervals, and "desired-min-tx-interval"
	and "required-min-rx-interval".
	2.1.1. Single-hop IP		local-multiplier
			This is the detection time multiplier as defined in
			[RFC5880].
	For single-hop IP, the BFD multiplier and interval(s) are configured		desired-min-tx-interval
	in BFD clients. It is highly desirable to have the BFD configuration		This is the Desired Min TX Interval as defined in [RFC5880].
	consistent between those clients. Therefore, we have a grouping for
	BFD configuration that applications can import in their YANG module:
	- This provides consistency since the same grouping is being used in		required-min-rx-interval
	all applications making use of BFD.		This is the Required Min RX Interval as defined in [RFC5880].
	- Not all implementations of those BFD clients have support for BFD,		Although [RFC5880] allows for different values for transmit and
	we must use if-feature in the respective YANG modules.		receive intervals, some implementations allow users to specify just
			one interval which is used for both transmit and receive intervals or
			separate values for transmit and receive intervals. The BFD YANG
			model supports this: there is a choice between "min-interval", used
			for both transmit and receive intervals, and "desired-min-tx-
			interval" and "required-min-rx-interval". This is supported via a
			grouping which is used by the YANG modules for the various forwarding
			paths. There are also intervals for the echo function (if
			supported):
	An application importing the BFD configuration grouping could do so		desired-min-echo-tx-interval
	in a hierarchical manner if it has multiple levels at which BFD		This is the minimum interval that the local system would like
	configuration can be applied. In a subsequent section, we provide an		to use when transmitting BFD echo packets. If 0, the echo
	example of how a BFD client would use the grouping in such a way.		function as defined in [RFC5880] is disabled.
	The configuration items are:		required-min-echo-rx-interval
			This is the Required Min Echo RX Interval as defined in
			[RFC5880].
	enabled		For BFD authentication we have:
	Set to true to enable BFD.
	local-multiplier		key-chain
	This is the detection time multiplier as defined in		This is a reference to key-chain defined in
	[RFC5880].		[I-D.ietf-rtgwg-yang-key-chain]. The keys, cryptographic
			algotihms, key lifetime etc are all defined in the key-chain
			model.
	min-interval		replay-protection
	This is the Desired Min TX Interval and Required Min RX		This specifies meticulous v/s non-meticulous mode as per
	Interval as defined in [RFC5880].		[RFC5880].
	OR		2.1.2. Single-hop IP
	desired-min-tx-interval		For single-hop IP, there is an augment of the "bfd" data node under
	This is the Desired Min TX Interval as defined in [RFC5880].		"routing-protocol" in Section 2. We have a list of IP single-hop
			sessions where each session is uniquely identified by the interface
			and destination address pair. For the configuration parameters we
			use what is defined in Section 2.1.1
	required-min-rx-interval		2.1.3. Multi-hop IP
	This is the Required Min RX Interval as defined in [RFC5880].
	2.1.2. Multi-hop IP		For multi-hop IP, there is an augment of the "bfd" data node under
			"routing-protocol" in Section 2.
	We have a list for BFD sessions over multi-hop IP. The key consists		We have a list for BFD sessions over multi-hop IP. The key consists
	of:		of:
	source address		source address
	Address belonging to the local system as per [RFC5883]		Address belonging to the local system as per [RFC5883]
	destination address		destination address
	Address belonging to the remote system as per [RFC5883]		Address belonging to the remote system as per [RFC5883]
	Since we are following a VRF-centric model we do not need a VRF field		Since we are following a VRF-centric model we do not need a VRF field
	in the key.		in the key.
	Here is the list of parameters:		For the configuration parameters we use what is defined in
			Section 2.1.1
	local-multiplier
	This is the detection time multiplier as defined in
	[RFC5880].
	desired-min-tx-interval
	This is the Desired Min TX Interval as defined in [RFC5880].
	required-min-rx-interval
	This is the Required Min RX Interval as defined in [RFC5880].
	demand-enabled
	Set to true to enable demand mode as defined in [RFC5880].
	enable-authentication
	Set to true to enable BFD authentication.
	authentication-algorithm
	Authentication algorithm to use, if enabled.
	key-chain-name		Here are some extra parameters:
	Key-chain to be used for authentication, if enabled.
	tx-ttl		tx-ttl
	TTL of outgoing BFD control packets.		TTL of outgoing BFD control packets.
	rx-ttl		rx-ttl
	Minimum TTL of incoming BFD control packets.		Minimum TTL of incoming BFD control packets.
	2.1.3. Traffic Engineering Tunnels		2.1.4. MPLS Traffic Engineering Tunnels
	For Traffic Engineering (TE) tunnels, BFD is configured under the TE
	tunnel since it is the Traffic Enginnering application which knows
	the desired failure detection parameters. The grouping for BFD
	clients in Section 2.1.1 can be used by the TE application for the
	basic BFD parameters. For BFD parameters which are specific to the
	TE application, e.g. whether to tear down the tunnel in the event of
	a BFD session failure, these parameters will be defined in the YANG
	model of the TE application.
	2.1.4. LDP Label Switched Paths
	For LDP LSPs, BFD is configured under the LDP FEC. The grouping for
	BFD clients in Section 2.1.1 can be used by the LDP application for
	the basic BFD parameters. For BFD parameters which are specific to
	the LDP application, if any, these parameters will be defined in the
	YANG model of the LDP application.
	2.1.5. Link Aggregation Groups
	Per [RFC7130], configuring BFD on LAG consists of having micro-BFD		For MPLS-TE tunnels, BFD is configured under the MPLS-TE tunnel since
	sessions on each LAG member link. The grouping for BFD clients in		the desired failure detection parameters is a property of the MPLS-TE
	Section 2.1.1 can be used by the LAG application for the basic BFD		tunnel. This is achieved by augmenting the MPLS-TE data model in
	parameters. This grouping can be used per-LAG or per member-link.		[I-D.ietf-teas-yang-te]. For BFD parameters which are specific to
	For BFD parameters which are specific to the LAG application, e.g.		the TE application, e.g. whether to tear down the tunnel in the event
	the IP address of the peer system which can be reached by the LAG,		of a BFD session failure, these parameters will be defined in the
	the parameters will be defined in the YANG model of the LAG		YANG model of the MPLS-TE application.
	application.
	2.1.6. Per-interface Configuration		On top of the usual BFD parameters, we have the following per MPLS-TE
			tunnel:
	With multiplier and intervals configured under the BFD clients, we		encap
	still need a central location to configure authentication, demand		Encapsulation for the BFD packets: choice between IP, G-ACh
	mode, etc. This can be done by configuring the following parameters		and IP with G-ACh as per [RFC5586]
	per interface:
	demand-enabled		For general MPLS-TE data, "mpls-te" data node is added under the top-
	Set to true to enable demand mode as defined in [RFC5880].		level "bfd" node in Section 2. Since some MPLS-TE tunnels are uni-
			directional there is no MPLS-TE configuration for these tunnels on
			the egress node (note that this does not apply to bi-directional
			MPLS-TP tunnels). The BFD parameters for the egress node are added
			under "mpls-te".
	enable-authentication		2.1.5. MPLS Label Switched Paths
	Set to true to enable BFD authentication.
	authentication-algorithm		Here we address MPLS LSPs whose FEC is an IP address. The top-level
	Authentication algorithm to use, if enabled.		"bfd" node in Section 2 is augmented with "mpls" which contains a
			list of sessions uniquely identified by an IP address.
	key-chain-name		Since these LSPs are uni-directional there is no LSP configuration on
	Key-chain to be used for authentication, if enabled.		the egress node. The BFD parameters for the egress node are added
			under "mpls".
	desired-min-echo-tx-interval		2.1.6. Link Aggregation Groups
	This is the minimum interval that the local system would like
	to use when transmitting BFD echo packets. If 0, the echo
	function as defined in [RFC5880] is disabled.
	required-min-echo-rx-interval		Per [RFC7130], configuring BFD on LAG consists of having micro-BFD
	This is the Required Min Echo RX Interval as defined in		sessions on each LAG member link. Since the BFD parameters are an
	[RFC5880].		attribute of the LAG, they should be under the LAG. However there is
			no LAG YANG model which we can augment. So a "lag" data node is
			added to the top-level "bfd" node in Section 2, the configuration is
			per-LAG: we have a list of LAGs. The destination IP address of the
			micro-BFD sessions is configured per-LAG and per address-family (IPv4
			and IPv6)
	2.2. Design of Operational Model		2.2. Design of Operational Model
	The operational model contains both the overall statistics of BFD		The operational model contains both the overall statistics of BFD
	sessions running on the device and the per session operational		sessions running on the device and the per session operational
	statistics. Since BFD is used for liveness detection of arbitrary		information.
	paths, there is no uniform key to identify a BFD session. E.g. a BFD
	single-hop IP session is uniquely identified by the combination of		The overall statistics of BFD sessions consist of number of BFD
	destination IP address and interface whereas a multihop IP session is		sessions, number of BFD sessions up etc. This information is
	uniquely identified by the combination of source IP address and		available globally (i.e. for all BFD sessions) under the top level
	destination IP address (in the context of a VRF). For this reason,		"bfd" node in Section 2 and also per type of forwarding path.
	for per-session operational statistics, we do not have a single list
	with different type BFD sessions. Instead, we have a container where		For each BFD session, mainly three categories of operational items
	we have multiple lists, where each list corresponds to one specific		are shown. The fundamental information of a BFD session such as the
	path type for BFD. For example, we have one operational list for BFD		local discriminator, remote discriminator and the capability of
	single-hop IP, another list for BFD multi-hop IP, etc. In each list,		supporting demand detect mode are shown in the first category. The
	mainly three categories of operational items are shown. The		second category includes a BFD session running information, e.g. the
	fundamental information of a BFD session such as the local		remote BFD state and the diagnostic code received. Another example
	discriminator, remote discriminator and the capability of supporting		is the actual transmit interval between the control packets, which
	demand detect mode are shown in the first category. The second		may be different from the desired minimum transmit interval
	category includes a BFD session running information, e.g. the FSM the		configured, is shown in this category. Similar examples are actual
	device in and diagnostic code received. Another example is the		received interval between the control packets and the actual transmit
	actual transmit interval between the control packets, which may be		interval between the echo packets. The third category contains the
	different from the desired minimum transmit interval configured, is		detailed statistics of the session, e.g. when the session
	shown in this category. Similar examples are actual received		transitioned up/down and how long it has been in that state.
	interval between the control packets and the actual transmit interval
	between the echo packets. The third category contains the detailed
	statistics of the session, e.g. when the session transitioned up/down
	and how long it has been in that state.
	For some session types, there may be more than 1 session on the		For some session types, there may be more than 1 session on the
	virtual path to the destination. For example, with IP multi-hop		virtual path to the destination. For example, with IP multi-hop
	there could be multiple BFD sessions from the source to the same		there could be multiple BFD sessions from the source to the same
	destination to test the various paths (ECMP) to the destination.		destination to test the various paths (ECMP) to the destination.
	Each of the BFD sessions on the same virtual path is uniquely		Each of the BFD sessions on the same virtual path is uniquely
	identified by the source UDP port		identified by the local discriminator.
	2.3. Notifications		2.3. Notifications
	This YANG model defines a list of notifications to inform clients of		This YANG model defines notifications to inform clients of BFD of
	BFD of important events detected during the protocol operation. Pair		important events detected during the protocol operation. Pair of
	of local and remote discriminator identifies a BFD session on local		local and remote discriminator identifies a BFD session on local
	system. Notifications also give more important details about BFD		system. Notifications also give more important details about BFD
	sessions; e.g. new state, time in previous state, routing-instance		sessions; e.g. new state, time in previous state, routing-instance
	and the reason that the BFD session state changed.		and the reason that the BFD session state changed. The notifications
			are defined for each type of forwarding path but use groupings for
			common information.
	2.4. RPC Operations		2.4. RPC Operations
	TBD		TBD
	2.5. BFD Configuration Data Hierarchy		2.5. BFD top level hierarchy
	2.5.1. Centralized BFD Configuration
	The following is the centralized configuration data hierarchy:
	We have a container which contains a list for each session type.
	This contains session configuration for only IP multi-hop sessions.
	We have per-interface configuration for authentication, demand-mode,
	etc. This is used e.g. for IP single-hop sessions whose base BFD
	configuration belongs to the BFD clients.
			At the top level there is no configuration data, only operational
			data. The operational data consist of overall BFD session statistics
			globally and per routing-instance
	module: ietf-bfd		module: ietf-bfd
	augment /rt:routing/rt:routing-instance/rt:routing-protocols/		+--rw bfd!
	rt:routing-protocol:		+--rw config
	+--rw bfd		+--ro oper
	+--rw bfd-cfg		+--ro bfd-session-statistics
	| +--rw bfd-session-cfg		+--ro session-count? uint32
	| | +--rw session-ip-mh* [source-addr dest-addr]		+--ro session-up-count? uint32
	| | +--rw source-addr inet:ip-address		+--ro session-down-count? uint32
	| | +--rw dest-addr inet:ip-address		+--ro session-admin-down-count? uint32
	| | +--rw admin-down? boolean		augment /rt:routing/rt:routing-instance
	| | +--rw local-multiplier? multiplier		/rt:routing-protocols/rt:routing-protocol:
	| | +--rw (interval-config-type)?		+--rw bfd!
	| | | +--:(tx-rx-intervals)		+--rw config
	| | | | +--rw desired-min-tx-interval uint32		+--ro oper
	| | | | +--rw required-min-rx-interval uint32		+--ro bfd-session-statistics
	| | | +--:(single-interval)		+--ro session-count? uint32
	| | | +--rw min-interval uint32		+--ro session-up-count? uint32
	| | +--rw demand-enabled? boolean		+--ro session-down-count? uint32
	| | +--rw enable-authentication? boolean		+--ro session-admin-down-count? uint32
	| | +--rw authentication-parms {bfd-authentication}?
	| | | +--rw key-chain-name? string
	| | | +--rw algorithm? bfd-auth-algorithm
	| | +--rw tx-ttl? ttl
	| | +--rw rx-ttl ttl
	| +--rw bfd-interface-cfg* [interface] {bfd-interface-config}?
	| +--rw interface if:interface-ref
	| +--rw local-multiplier? multiplier
	| +--rw (interval-config-type)?
	| | +--:(tx-rx-intervals)
	| | | +--rw desired-min-tx-interval uint32
	| | | +--rw required-min-rx-interval uint32
	| | +--:(single-interval)
	| | +--rw min-interval uint32
	| +--rw demand-enabled? boolean
	| +--rw enable-authentication? boolean
	| +--rw authentication-parms {bfd-authentication}?
	| | +--rw key-chain-name? string
	| | +--rw algorithm? bfd-auth-algorithm
	| +--rw desired-min-echo-tx-interval? uint32
	| +--rw required-min-echo-rx-interval? uint32
	2.5.2. Configuration in BFD clients
	The following is the configuration data hierarchy for a hypothetical
	BFD client called example-bfd-routing-app. The BFD configuration is
	supported conditionally via use of if-feature.
	We have a list of areas and in each area we have a list of		2.6. BFD IP single-hop hierarchy
	interfaces. The BFD configuration grouping is used in a hierarchical
	fashion, it can be applied in "area" and "interface":
	- If BFD configuration is applied under an interface, that		The configuration and operational data for each BFD IP single-hop
	configuration takes precedence over any BFD configuration, if any, at		session is under "ip-sh" node under routing-instance. Overall BFD IP
	the area level		single-hop session statistics are available per routing-instance and
			globally (for all routing instances).
	- If BFD configuration is applied under an "area" and none of the		module: ietf-bfd-ip-sh
	interfaces in that area has BFD configuration, then all interfaces		augment /bfd:bfd:
	belong to the "area" in question inherit the BFD configuration for		+--rw ip-sh
	the area in question.		+--rw config
			+--ro oper
			+--ro bfd-session-statistics
			+--ro session-count? uint32
			+--ro session-up-count? uint32
			+--ro session-down-count? uint32
			+--ro session-admin-down-count? uint32
			augment /rt:routing/rt:routing-instance/rt:routing-protocols
			/rt:routing-protocol/bfd:bfd:
			+--rw ip-sh
			+--rw config
			| +--rw session-cfg
			| +--rw sessions* [interface dest-addr]
			| +--rw interface if:interface-ref
			| +--rw dest-addr inet:ip-address
			| +--rw source-addr? inet:ip-address
			| +--rw local-multiplier? bfd-multiplier
			| +--rw (interval-config-type)?
			| | +--:(tx-rx-intervals)
			| | | +--rw desired-min-tx-interval uint32
			| | | +--rw required-min-rx-interval uint32
			| | +--:(single-interval)
			| | +--rw min-interval uint32
			| +--rw demand-enabled? boolean
			| +--rw admin-down? boolean
			| +--rw authentication-parms! {bfd-authentication}?
			| | +--rw key-chain? kc:key-chain-ref
			| | +--rw replay-protection? identityref
			| +--rw desired-min-echo-tx-interval? uint32
			| +--rw required-min-echo-rx-interval? uint32
			+--ro oper
			+--ro bfd-session-statistics
			| +--ro session-count? uint32
			| +--ro session-up-count? uint32
			| +--ro session-down-count? uint32
			| +--ro session-admin-down-count? uint32
			+--ro sessions* [interface dest-addr]
			+--ro interface if:interface-ref
			+--ro dest-addr inet:ip-address
			+--ro source-addr? inet:ip-address
			+--ro path-type? identityref
			+--ro local-discriminator? bfd-discriminator
			+--ro remote-discriminator? bfd-discriminator
			+--ro remote-multiplier? bfd-multiplier
			+--ro out-interface? if:interface-ref
			+--ro demand-capability? boolean
			+--ro source-port? inet:port-number
			+--ro dest-port? inet:port-number
			+--ro session-running
			| +--ro session-index? uint32
			| +--ro local-state? bfd-state
			| +--ro remote-state? bfd-state
			| +--ro local-diagnostic? bfd-diagnostic
			| +--ro remote-diagnostic? bfd-diagnostic
			| +--ro detection-mode? enumeration
			| +--ro negotiated-tx-interval? uint32
			| +--ro negotiated-rx-interval? uint32
			| +--ro echo-tx-interval-in-use? uint32
			| +--ro detection-time? uint32
			+--ro sesssion-statistics
			+--ro create-time? yang:date-and-time
			+--ro last-down-time? yang:date-and-time
			+--ro last-up-time? yang:date-and-time
			+--ro down-count? uint32
			+--ro admin-down-count? uint32
			+--ro receive-packet-count? uint64
			+--ro send-packet-count? uint64
			+--ro receive-bad-packet? uint64
			+--ro send-failed-packet? uint64
			notifications:
			+---n bfd-singlehop-notification
			+--ro local-discr? bfd-discriminator
			+--ro remote-discr? bfd-discriminator
			+--ro new-state? bfd-state
			+--ro state-change-reason? string
			+--ro time-in-previous-state? string
			+--ro dest-addr? inet:ip-address
			+--ro source-addr? inet:ip-address
			+--ro session-index? uint32
			+--ro path-type? identityref
			+--ro interface? if:interface-ref
			+--ro echo-enabled? boolean
	- If the BFD client implementation supports "interface all", then all		2.7. BFD IP multi-hop hierarchy
	the interfaces belonging to that area will inherit the BFD
	configuration under "interface all". Additionally, if there is
	specific interface configuration, then the specific interface will
	override the "interface all" parameters.
	- The tx and rx intervals can be configured separately or a single		The configuration and operational data for each BFD IP multi-hop
	interval can be configured.		session is under "ip-mh" node under routing-instance. In the
			operational model we support multiple BFD multi-hop sessions per
			remote address (ECMP), the local discriminator is used as key.
			Overall BFD IP multi-hop session statistics are available per
			routing-instance and globally (for all routing instances).
	module: example-bfd-routing-app		module: ietf-bfd-ip-mh
	+--rw area* [area-id]		augment /bfd:bfd:
	+--rw area-id uint32		+--rw ip-mh
	+--rw bfd-cfg		+--rw config
	| +--rw enabled? boolean		+--ro oper
	| +--rw local-multiplier? multiplier		+--ro bfd-session-statistics
	| +--rw (interval-config-type)?		+--ro session-count? uint32
	| +--:(tx-rx-intervals)		+--ro session-up-count? uint32
	| | +--rw desired-min-tx-interval uint32		+--ro session-down-count? uint32
	| | +--rw required-min-rx-interval uint32		+--ro session-admin-down-count? uint32
	| +--:(single-interval)		augment /rt:routing/rt:routing-instance/rt:routing-protocols
	| +--rw min-interval uint32		/rt:routing-protocol/bfd:bfd:
	+--rw interface* [interface]		+--rw ip-mh
	+--rw interface if:interface-ref		+--rw config
	+--rw bfd-cfg		| +--rw session-cfg
	+--rw enabled? boolean		| +--rw sessions* [source-addr dest-addr]
	+--rw local-multiplier? multiplier		| +--rw source-addr inet:ip-address
	+--rw (interval-config-type)?		| +--rw dest-addr inet:ip-address
	+--:(tx-rx-intervals)		| +--rw local-multiplier? bfd-multiplier
	| +--rw desired-min-tx-interval uint32		| +--rw (interval-config-type)?
	| +--rw required-min-rx-interval uint32		| | +--:(tx-rx-intervals)
	+--:(single-interval)		| | | +--rw desired-min-tx-interval uint32
	+--rw min-interval uint32		| | | +--rw required-min-rx-interval uint32
			| | +--:(single-interval)
			| | +--rw min-interval uint32
			| +--rw demand-enabled? boolean
			| +--rw admin-down? boolean
			| +--rw authentication-parms! {bfd-authentication}?
			| | +--rw key-chain? kc:key-chain-ref
			| | +--rw replay-protection? identityref
			| +--rw tx-ttl? bfd:ttl
			| +--rw rx-ttl bfd:ttl
			+--ro oper
			+--ro bfd-session-statistics
			| +--ro bfd-session-statistics
			| +--ro session-count? uint32
			| +--ro session-up-count? uint32
			| +--ro session-down-count? uint32
			| +--ro session-admin-down-count? uint32
			+--ro session-group* [source-addr dest-addr]
			+--ro source-addr inet:ip-address
			+--ro dest-addr inet:ip-address
			+--ro sessions* [local-discriminator]
			+--ro ttl? bfd:ttl
			+--ro path-type? identityref
			+--ro local-discriminator bfd-discriminator
			+--ro remote-discriminator? bfd-discriminator
			+--ro remote-multiplier? bfd-multiplier
			+--ro out-interface? if:interface-ref
			+--ro demand-capability? boolean
			+--ro source-port? inet:port-number
			+--ro dest-port? inet:port-number
			+--ro session-running
			| +--ro session-index? uint32
			| +--ro local-state? bfd-state
			| +--ro remote-state? bfd-state
			| +--ro local-diagnostic? bfd-diagnostic
			| +--ro remote-diagnostic? bfd-diagnostic
			| +--ro detection-mode? enumeration
			| +--ro negotiated-tx-interval? uint32
			| +--ro negotiated-rx-interval? uint32
			| +--ro echo-tx-interval-in-use? uint32
			| +--ro detection-time? uint32
			+--ro sesssion-statistics
			+--ro create-time? yang:date-and-time
			+--ro last-down-time? yang:date-and-time
			+--ro last-up-time? yang:date-and-time
			+--ro down-count? uint32
			+--ro admin-down-count? uint32
			+--ro receive-packet-count? uint64
			+--ro send-packet-count? uint64
			+--ro receive-bad-packet? uint64
			+--ro send-failed-packet? uint64
			notifications:
			+---n bfd-multihop-notification
			+--ro local-discr? bfd-discriminator
			+--ro remote-discr? bfd-discriminator
			+--ro new-state? bfd-state
			+--ro state-change-reason? string
			+--ro time-in-previous-state? string
			+--ro dest-addr? inet:ip-address
			+--ro source-addr? inet:ip-address
			+--ro session-index? uint32
			+--ro path-type? identityref
			+--ro routing-instance? rt:routing-instance-ref
	2.6. Operational Data Hierarchy		2.8. BFD over LAG hierarchy
	The complete data hierarchy of BFD YANG operational model is		The configuration and operational data for each BFD LAG session is
	presented below.		under "lag" node. Overall BFD LAG session statistics are available
			globally.
	module: ietf-bfd		module: ietf-bfd-lag
	augment /rt:routing/rt:routing-instance/rt:routing-protocols/		augment /bfd:bfd:
	rt:routing-protocol:		+--rw lag
	+--rw bfd		+--rw config
	+--ro bfd-oper		| +--rw session-cfg
	+--ro bfd-session-statistics		| +--rw sessions* [lag-name]
	| +--ro ip-sh-session-num? uint32		| +--rw lag-name if:interface-ref
	| +--ro ip-mh-session-num? uint32		| +--rw ipv4-dest-addr? inet:ipv4-address
	| +--ro total-session-num? uint32		| +--rw ipv6-dest-addr? inet:ipv6-address
	| +--ro session-up-num? uint32		| +--rw local-multiplier? bfd-multiplier
	| +--ro sess-down-num? uint32		| +--rw (interval-config-type)?
	| +--ro sess-admin-down-num? uint32		| | +--:(tx-rx-intervals)
	+--ro bfd-session-lists		| | | +--rw desired-min-tx-interval uint32
	+--ro session-ip-sh* [interface dest-addr]		| | | +--rw required-min-rx-interval uint32
	| +--ro interface if:interface-ref		| | +--:(single-interval)
	| +--ro dest-addr inet:ip-address		| | +--rw min-interval uint32
	| +--ro source-addr? inet:ip-address		| +--rw demand-enabled? boolean
	| +--ro session-type? bfd-session-type		| +--rw admin-down? boolean
	| +--ro local-discriminator? discriminator		| +--rw authentication-parms! {bfd-authentication}?
	| +--ro remote-discriminator? discriminator		| +--rw key-chain? kc:key-chain-ref
	| +--ro remote-multiplier? multiplier		| +--rw replay-protection? identityref
	| +--ro out-interface? if:interface-ref		+--ro oper
	| +--ro demand-capability? boolean		+--ro micro-bfd-ipv4-session-statistics
	| +--ro source-port? inet:port-number		| +--ro bfd-session-statistics
	| +--ro dest-port? inet:port-number		| +--ro session-count? uint32
	| +--ro session-running*		| +--ro session-up-count? uint32
	| | +--ro session-index? uint32		| +--ro session-down-count? uint32
	| | +--ro local-state? state		| +--ro session-admin-down-count? uint32
	| | +--ro remote-state? state		+--ro micro-bfd-ipv6-session-statistics
	| | +--ro local-diagnostic? diagnostic		| +--ro bfd-session-statistics
	| | +--ro remote-diagnostic? diagnostic		| +--ro session-count? uint32
	| | +--ro detection-mode? enumeration		| +--ro session-up-count? uint32
	| | +--ro negotiated-tx-interval? uint32		| +--ro session-down-count? uint32
	| | +--ro negotiated-rx-interval? uint32		| +--ro session-admin-down-count? uint32
	| | +--ro negotiated-echo-tx-interval? uint32		+--ro session-lag* [lag-name]
	| | +--ro detection-time? uint32		+--ro lag-name if:interface-ref
	| +--ro sesssion-statistics*		+--ro use-ipv4? boolean
	| +--ro create-time? yang:date-and-time		+--ro use-ipv6? boolean
	| +--ro last-down-time? yang:date-and-time		+--ro member-links* [member-link]
	| +--ro last-up-time? yang:date-and-time		+--ro member-link if:interface-ref
	| +--ro down-count? uint32		+--ro micro-bfd-ipv4
	| +--ro admin-down-count? uint32		| +--ro path-type? identityref
	| +--ro receive-packet-count? uint64		| +--ro local-discriminator? bfd-discriminator
	| +--ro send-packet-count? uint64		| +--ro remote-discriminator? bfd-discriminator
	| +--ro receive-bad-packet? uint64		| +--ro remote-multiplier? bfd-multiplier
	| +--ro send-failed-packet? uint64		| +--ro out-interface? if:interface-ref
	+--ro session-ip-mh-group* [source-addr dest-addr]		| +--ro demand-capability? boolean
	| +--ro source-addr inet:ip-address		| +--ro source-port? inet:port-number
	| +--ro dest-addr inet:ip-address		| +--ro dest-port? inet:port-number
	| +--ro session-ip-mh* [source-port]		| +--ro session-running
	| +--ro ttl? ttl		| | +--ro session-index? uint32
	| +--ro session-type? bfd-session-type		| | +--ro local-state? bfd-state
	| +--ro local-discriminator? discriminator		| | +--ro remote-state? bfd-state
	| +--ro remote-discriminator? discriminator		| | +--ro local-diagnostic? bfd-diagnostic
	| +--ro remote-multiplier? multiplier		| | +--ro remote-diagnostic? bfd-diagnostic
	| +--ro out-interface? if:interface-ref		| | +--ro detection-mode? enumeration
	| +--ro demand-capability? boolean		| | +--ro negotiated-tx-interval? uint32
	| +--ro source-port inet:port-number		| | +--ro negotiated-rx-interval? uint32
	| +--ro dest-port? inet:port-number		| | +--ro echo-tx-interval-in-use? uint32
	| +--ro session-running*		| | +--ro detection-time? uint32
	| | +--ro session-index? uint32		| +--ro sesssion-statistics
	| | +--ro local-state? state		| +--ro create-time? yang:date-and-time
	| | +--ro remote-state? state		| +--ro last-down-time? yang:date-and-time
	| | +--ro local-diagnostic? diagnostic		| +--ro last-up-time? yang:date-and-time
	| | +--ro remote-diagnostic? diagnostic		| +--ro down-count? uint32
	| | +--ro detection-mode? enumeration		| +--ro admin-down-count? uint32
	| | +--ro negotiated-tx-interval? uint32		| +--ro receive-packet-count? uint64
	| | +--ro negotiated-rx-interval? uint32		| +--ro send-packet-count? uint64
	| | +--ro negotiated-echo-tx-interval? uint32		| +--ro receive-bad-packet? uint64
	| | +--ro detection-time? uint32		| +--ro send-failed-packet? uint64
	| +--ro sesssion-statistics*		+--ro micro-bfd-ipv6
	| +--ro create-time? yang:date-and-time		+--ro path-type? identityref
	| +--ro last-down-time? yang:date-and-time		+--ro local-discriminator? bfd-discriminator
	| +--ro last-up-time? yang:date-and-time		+--ro remote-discriminator? bfd-discriminator
	| +--ro down-count? uint32		+--ro remote-multiplier? bfd-multiplier
	| +--ro admin-down-count? uint32
	| +--ro receive-packet-count? uint64
	| +--ro send-packet-count? uint64
	| +--ro receive-bad-packet? uint64
	| +--ro send-failed-packet? uint64
	+--ro session-te-tunnel* [tunnel-name]
	| +--ro tunnel-name string
	| +--ro session-type? bfd-session-type
	| +--ro local-discriminator? discriminator
	| +--ro remote-discriminator? discriminator
	| +--ro remote-multiplier? multiplier
	| +--ro out-interface? if:interface-ref
	| +--ro demand-capability? boolean
	| +--ro source-port? inet:port-number
	| +--ro dest-port? inet:port-number
	| +--ro session-running*
	| | +--ro session-index? uint32
	| | +--ro local-state? state
	| | +--ro remote-state? state
	| | +--ro local-diagnostic? diagnostic
	| | +--ro remote-diagnostic? diagnostic
	| | +--ro detection-mode? enumeration
	| | +--ro negotiated-tx-interval? uint32
	| | +--ro negotiated-rx-interval? uint32
	| | +--ro negotiated-echo-tx-interval? uint32
	| | +--ro detection-time? uint32
	| +--ro sesssion-statistics*
	| +--ro create-time? yang:date-and-time
	| +--ro last-down-time? yang:date-and-time
	| +--ro last-up-time? yang:date-and-time
	| +--ro down-count? uint32
	| +--ro admin-down-count? uint32
	| +--ro receive-packet-count? uint64
	| +--ro send-packet-count? uint64
	| +--ro receive-bad-packet? uint64
	| +--ro send-failed-packet? uint64
	+--ro session-ldp-lsp-group* [ldp-fec]
	| +--ro ldp-fec inet:ip-prefix
	| +--ro session-ldp-lsp* [source-port]
	| +--ro ttl? ttl
	| +--ro session-type? bfd-session-type
	| +--ro local-discriminator? discriminator
	| +--ro remote-discriminator? discriminator
	| +--ro remote-multiplier? multiplier
	| +--ro out-interface? if:interface-ref
	| +--ro demand-capability? boolean
	| +--ro source-port inet:port-number
	| +--ro dest-port? inet:port-number
	| +--ro session-running*
	| | +--ro session-index? uint32
	| | +--ro local-state? state
	| | +--ro remote-state? state
	| | +--ro local-diagnostic? diagnostic
	| | +--ro remote-diagnostic? diagnostic
	| | +--ro detection-mode? enumeration
	| | +--ro negotiated-tx-interval? uint32
	| | +--ro negotiated-rx-interval? uint32
	| | +--ro negotiated-echo-tx-interval? uint32
	| | +--ro detection-time? uint32
	| +--ro sesssion-statistics*
	| +--ro create-time? yang:date-and-time
	| +--ro last-down-time? yang:date-and-time
	| +--ro last-up-time? yang:date-and-time
	| +--ro down-count? uint32
	| +--ro admin-down-count? uint32
	| +--ro receive-packet-count? uint64
	| +--ro send-packet-count? uint64
	| +--ro receive-bad-packet? uint64
	| +--ro send-failed-packet? uint64
	+--ro session-lag* [lag-name]
	+--ro lag-name if:interface-ref
	+--ro session-lag-micro* [member-link]
	+--ro member-link if:interface-ref
	+--ro session-type? bfd-session-type
	+--ro local-discriminator? discriminator
	+--ro remote-discriminator? discriminator
	+--ro remote-multiplier? multiplier
	+--ro out-interface? if:interface-ref		+--ro out-interface? if:interface-ref
	+--ro demand-capability? boolean		+--ro demand-capability? boolean
	+--ro source-port? inet:port-number		+--ro source-port? inet:port-number
	+--ro dest-port? inet:port-number		+--ro dest-port? inet:port-number
	+--ro session-running*		+--ro session-running
	| +--ro session-index? uint32		| +--ro session-index? uint32
	| +--ro local-state? state		| +--ro local-state? bfd-state
	| +--ro remote-state? state		| +--ro remote-state? bfd-state
	| +--ro local-diagnostic? diagnostic		| +--ro local-diagnostic? bfd-diagnostic
	| +--ro remote-diagnostic? diagnostic		| +--ro remote-diagnostic? bfd-diagnostic
	| +--ro detection-mode? enumeration		| +--ro detection-mode? enumeration
	| +--ro negotiated-tx-interval? uint32		| +--ro negotiated-tx-interval? uint32
	| +--ro negotiated-rx-interval? uint32		| +--ro negotiated-rx-interval? uint32
	| +--ro negotiated-echo-tx-interval? uint32		| +--ro echo-tx-interval-in-use? uint32
	| +--ro detection-time? uint32		| +--ro detection-time? uint32
	+--ro sesssion-statistics*		+--ro sesssion-statistics
	+--ro create-time? yang:date-and-time		+--ro create-time? yang:date-and-time
	+--ro last-down-time? yang:date-and-time		+--ro last-down-time? yang:date-and-time
	+--ro last-up-time? yang:date-and-time		+--ro last-up-time? yang:date-and-time
	+--ro down-count? uint32		+--ro down-count? uint32
	+--ro admin-down-count? uint32		+--ro admin-down-count? uint32
	+--ro receive-packet-count? uint64		+--ro receive-packet-count? uint64
	+--ro send-packet-count? uint64		+--ro send-packet-count? uint64
	+--ro receive-bad-packet? uint64		+--ro receive-bad-packet? uint64
	+--ro send-failed-packet? uint64		+--ro send-failed-packet? uint64
			notifications:
			+---n bfd-lag-notification
			+--ro local-discr? bfd-discriminator
			+--ro remote-discr? bfd-discriminator
			+--ro new-state? bfd-state
			+--ro state-change-reason? string
			+--ro time-in-previous-state? string
			+--ro dest-addr? inet:ip-address
			+--ro source-addr? inet:ip-address
			+--ro session-index? uint32
			+--ro path-type? identityref
			+--ro lag-name? if:interface-ref
			+--ro member-link? if:interface-ref
	2.7. Notifications		2.9. BFD over MPLS LSPs hierarchy
	The BFD YANG data model defines notifications for BFD session state		The configuration is per MPLS FEC under "mpls". In the operational
	changes.		model we support multiple BFD sessions per MPLS FEC (ECMP), the local
			discriminator is used as key.
	module: ietf-bfd		module: ietf-bfd-mpls
	augment /rt:routing/rt:routing-instance/rt:routing-protocols/		augment /bfd:bfd:
	rt:routing-protocol:
			+--rw mpls
			+--rw config
			| +--rw egress
			| +--rw local-multiplier? bfd-multiplier
			| +--rw (interval-config-type)?
			| | +--:(tx-rx-intervals)
			| | | +--rw desired-min-tx-interval uint32
			| | | +--rw required-min-rx-interval uint32
			| | +--:(single-interval)
			| | +--rw min-interval uint32
			| +--rw authentication-parms! {bfd-authentication}?
			| +--rw key-chain? kc:key-chain-ref
			| +--rw replay-protection? identityref
			+--ro oper
			+--ro bfd-session-statistics
			+--ro session-count? uint32
			+--ro session-up-count? uint32
			+--ro session-down-count? uint32
			+--ro session-admin-down-count? uint32
			augment /rt:routing/rt:routing-instance/rt:routing-protocols
			/rt:routing-protocol/bfd:bfd:
			+--rw mpls
			+--rw config
			| +--rw session-cfg
			| +--rw sessions* [mpls-fec]
			| +--rw mpls-fec inet:ip-address
			| +--rw local-multiplier? bfd-multiplier
			| +--rw (interval-config-type)?
			| | +--:(tx-rx-intervals)
			| | | +--rw desired-min-tx-interval uint32
			| | | +--rw required-min-rx-interval uint32
			| | +--:(single-interval)
			| | +--rw min-interval uint32
			| +--rw demand-enabled? boolean
			| +--rw admin-down? boolean
			| +--rw authentication-parms! {bfd-authentication}?
			| +--rw key-chain? kc:key-chain-ref
			| +--rw replay-protection? identityref
			+--ro oper
			+--ro bfd-session-statistics
			| +--ro session-count? uint32
			| +--ro session-up-count? uint32
			| +--ro session-down-count? uint32
			| +--ro session-admin-down-count? uint32
			+--ro session-group* [mpls-fec]
			+--ro mpls-fec inet:ip-address
			+--ro sessions* [local-discriminator]
			+--ro path-type? identityref
			+--ro local-discriminator bfd-discriminator
			+--ro remote-discriminator? bfd-discriminator
			+--ro remote-multiplier? bfd-multiplier
			+--ro out-interface? if:interface-ref
			+--ro demand-capability? boolean
			+--ro source-port? inet:port-number
			+--ro dest-port? inet:port-number
			+--ro session-running
			| +--ro session-index? uint32
			| +--ro local-state? bfd-state
			| +--ro remote-state? bfd-state
			| +--ro local-diagnostic? bfd-diagnostic
			| +--ro remote-diagnostic? bfd-diagnostic
			| +--ro detection-mode? enumeration
			| +--ro negotiated-tx-interval? uint32
			| +--ro negotiated-rx-interval? uint32
			| +--ro echo-tx-interval-in-use? uint32
			| +--ro detection-time? uint32
			+--ro sesssion-statistics
			| +--ro create-time? yang:date-and-time
			| +--ro last-down-time? yang:date-and-time
			| +--ro last-up-time? yang:date-and-time
			| +--ro down-count? uint32
			| +--ro admin-down-count? uint32
			| +--ro receive-packet-count? uint64
			| +--ro send-packet-count? uint64
			| +--ro receive-bad-packet? uint64
			| +--ro send-failed-packet? uint64
			+--ro mpls-dest-address? inet:ip-address
	notifications:		notifications:
	+---n bfd-singlehop-notification		+---n bfd-mpls-notification
	| +--ro local-discr? discriminator		+--ro local-discr? bfd-discriminator
	| +--ro remote-discr? discriminator		+--ro remote-discr? bfd-discriminator
	| +--ro new-state? state		+--ro new-state? bfd-state
	| +--ro state-change-reason? string
	| +--ro time-in-previous-state? string
	| +--ro dest-addr? inet:ip-address
	| +--ro source-addr? inet:ip-address
	| +--ro session-index? uint32
	| +--ro session-type? bfd-session-type
	| +--ro interface? if:interface-ref
	| +--ro echo-enabled? boolean
	+---n bfd-multihop-notification
	| +--ro local-discr? discriminator
	| +--ro remote-discr? discriminator
	| +--ro new-state? state
	| +--ro state-change-reason? string
	| +--ro time-in-previous-state? string
	| +--ro dest-addr? inet:ip-address
	| +--ro source-addr? inet:ip-address
	| +--ro session-index? uint32
	| +--ro session-type? bfd-session-type
	+---n bfd-te-tunnel-notification
	| +--ro local-discr? discriminator
	| +--ro remote-discr? discriminator
	| +--ro new-state? state
	| +--ro state-change-reason? string
	| +--ro time-in-previous-state? string
	| +--ro dest-addr? inet:ip-address
	| +--ro source-addr? inet:ip-address
	| +--ro session-index? uint32
	| +--ro session-type? bfd-session-type
	| +--ro tunnel-name? string
	+---n bfd-ldp-lsp-notification
	| +--ro local-discr? discriminator
	| +--ro remote-discr? discriminator
	| +--ro new-state? state
	| +--ro state-change-reason? string
	| +--ro time-in-previous-state? string
	| +--ro dest-addr? inet:ip-address
	| +--ro source-addr? inet:ip-address
	| +--ro session-index? uint32
	| +--ro session-type? bfd-session-type
	| +--ro ldp-fec? inet:ip-prefix
	| +--ro source-port? inet:port-number
	+---n bfd-lag-notification
	+--ro local-discr? discriminator
	+--ro remote-discr? discriminator
	+--ro new-state? state
	+--ro state-change-reason? string		+--ro state-change-reason? string
	+--ro time-in-previous-state? string		+--ro time-in-previous-state? string
	+--ro dest-addr? inet:ip-address		+--ro dest-addr? inet:ip-address
	+--ro source-addr? inet:ip-address		+--ro source-addr? inet:ip-address
			+--ro session-index? uint32
			+--ro path-type? identityref
			+--ro routing-instance? rt:routing-instance-ref
			+--ro mpls-dest-address? inet:ip-address
	2.8. Examples		2.10. BFD over MPLS-TE hierarchy
	2.9. Interaction with other YANG modules		The MPLS-TE YANG model [I-D.ietf-teas-yang-te] is augmented. BFD is
			configured per MPLS-TE tunnel, and BFD session operational data is
			provided per MPLS-TE LSP.
			module: ietf-bfd-mpls-te
			augment /bfd:bfd:
			+--rw mpls-te
			+--rw config
			| +--rw egress
			| +--rw local-multiplier? bfd-multiplier
			| +--rw (interval-config-type)?
			| | +--:(tx-rx-intervals)
			| | | +--rw desired-min-tx-interval uint32
			| | | +--rw required-min-rx-interval uint32
			| | +--:(single-interval)
			| | +--rw min-interval uint32
			| +--rw authentication-parms! {bfd-authentication}?
			| +--rw key-chain? kc:key-chain-ref
			| +--rw replay-protection? identityref
			+--ro oper
			+--ro bfd-session-statistics
			+--ro session-count? uint32
			+--ro session-up-count? uint32
			+--ro session-down-count? uint32
			+--ro session-admin-down-count? uint32
			augment /te:te/te:tunnels/te:tunnel/te:config:
			+--rw local-multiplier? bfd-multiplier
			+--rw (interval-config-type)?
			| +--:(tx-rx-intervals)
			| | +--rw desired-min-tx-interval uint32
			| | +--rw required-min-rx-interval uint32
			| +--:(single-interval)
			| +--rw min-interval uint32
			+--rw demand-enabled? boolean
			+--rw admin-down? boolean
			+--rw authentication-parms! {bfd-authentication}?
			| +--rw key-chain? kc:key-chain-ref
			| +--rw replay-protection? identityref
			+--rw encap? identityref
			augment /te:te/te:lsps-state/te:lsp:
			+--ro path-type? identityref
			+--ro local-discriminator? bfd-discriminator
			+--ro remote-discriminator? bfd-discriminator
			+--ro remote-multiplier? bfd-multiplier
			+--ro out-interface? if:interface-ref
			+--ro demand-capability? boolean
			+--ro source-port? inet:port-number
			+--ro dest-port? inet:port-number
			+--ro session-running
			| +--ro session-index? uint32
			| +--ro local-state? bfd-state
			| +--ro remote-state? bfd-state
			| +--ro local-diagnostic? bfd-diagnostic
			| +--ro remote-diagnostic? bfd-diagnostic
			| +--ro detection-mode? enumeration
			| +--ro negotiated-tx-interval? uint32
			| +--ro negotiated-rx-interval? uint32
			| +--ro echo-tx-interval-in-use? uint32
			| +--ro detection-time? uint32
			+--ro sesssion-statistics
			| +--ro create-time? yang:date-and-time
			| +--ro last-down-time? yang:date-and-time
			| +--ro last-up-time? yang:date-and-time
			| +--ro down-count? uint32
			| +--ro admin-down-count? uint32
			| +--ro receive-packet-count? uint64
			| +--ro send-packet-count? uint64
			| +--ro receive-bad-packet? uint64
			| +--ro send-failed-packet? uint64
			+--ro mpls-dest-address? inet:ip-address
			notifications:
			+---n bfd-mpls-te-notification
			+--ro local-discr? bfd-discriminator
			+--ro remote-discr? bfd-discriminator
			+--ro new-state? bfd-state
			+--ro state-change-reason? string
			+--ro time-in-previous-state? string
			+--ro dest-addr? inet:ip-address
			+--ro source-addr? inet:ip-address
			+--ro session-index? uint32
			+--ro path-type? identityref
			+--ro mpls-dest-address? inet:ip-address
			+--ro tunnel-name? string
			2.11. Examples
			2.12. Interaction with other YANG modules
	TBD.		TBD.
	2.10. BFD Yang Module		2.13. BFD top-level Yang Module
	<CODE BEGINS> file "ietf-bfd@2015-07-01.yang"		<CODE BEGINS> file "ietf-bfd@2016-02-17.yang"
	module ietf-bfd {		module ietf-bfd {
	namespace "urn:ietf:params:xml:ns:yang:ietf-bfd";		namespace "urn:ietf:params:xml:ns:yang:ietf-bfd";
	// replace with IANA namespace when assigned		// replace with IANA namespace when assigned
	prefix "bfd";		prefix "bfd";
	import ietf-interfaces {		import ietf-interfaces {
	prefix "if";		prefix "if";
	}		}
	import ietf-inet-types {		import ietf-inet-types {
	prefix "inet";		prefix "inet";
	}		}
	import ietf-yang-types {		import ietf-yang-types {
	prefix "yang";		prefix "yang";
	}		}
	import ietf-routing {		import ietf-routing {
	prefix "rt";		prefix "rt";
	}		}
			import ietf-key-chain {
			prefix "kc";
			}
	organization "IETF BFD Working Group";		organization "IETF BFD Working Group";
	contact		contact
	"WG Web: <http://tools.ietf.org/wg/bfd>		"WG Web: <http://tools.ietf.org/wg/bfd>
	WG List: <rtg-bfd@ietf.org>		WG List: <rtg-bfd@ietf.org>
	WG Chair: Jeff Haas		WG Chair: Jeff Haas
	WG Chair: Nobo Akiya		WG Chair: Reshad Rahman
	Editor: Lianshu Zheng and Reshad Rahman";		Editor: Lianshu Zheng and Reshad Rahman";
	description		description
	"This module contains the YANG definition for BFD parameters as		"This module contains the YANG definition for BFD parameters as
	per RFC5880, RFC5881 and RFC5883";		per RFC5880.";
			revision 2016-02-17 {
			description
			"* Split in several modules
			* This module contains common definitions and
			summary information.";
			reference "RFC XXXX: A YANG data model for BFD";
			}
	revision 2015-07-01 {		revision 2015-07-01 {
	description "Initial revision.";		description "Initial revision.";
	reference "RFC XXXX: A YANG data model for BFD";		reference "RFC XXXX: A YANG data model for BFD";
	}		}
	identity bfd {		identity bfd {
	base "rt:routing-protocol";		base "rt:routing-protocol";
	description "BFD protocol";		description "BFD protocol";
	}		}
	typedef discriminator {		typedef bfd-discriminator {
	type uint32 {		type uint32 {
	range 1..4294967295;		range 1..4294967295;
	}		}
	description "BFD discriminator";		description "BFD discriminator";
	}		}
	typedef diagnostic {
			typedef bfd-diagnostic {
	type enumeration {		type enumeration {
	enum none {		enum none {
	value 0;		value 0;
	description "None";		description "None";
	}		}
	enum controlExpiry {		enum controlExpiry {
	value 1;		value 1;
	description "Control timer expiry";		description "Control timer expiry";
	}		}
	enum echoFailed {		enum echoFailed {
	skipping to change at page 18, line 4 ¶		skipping to change at page 21, line 48 ¶
	value 6;		value 6;
	description "Concatenated path down";		description "Concatenated path down";
	}		}
	enum adminDown {		enum adminDown {
	value 7;		value 7;
	description "Admin down";		description "Admin down";
	}		}
	enum reverseConcPathDown {		enum reverseConcPathDown {
	value 8;		value 8;
	description "Reverse concatenated path down";		description "Reverse concatenated path down";
	}		}
	}		}
	description "BFD diagnostic";		description "BFD diagnostic";
	}		}
	typedef state {		typedef bfd-state {
	type enumeration {		type enumeration {
	enum adminDown {		enum adminDown {
	value 0;		value 0;
	description "admindown";		description "admindown";
	}		}
	enum down {		enum down {
	value 1;		value 1;
	description "down";		description "down";
	}		}
	enum init {		enum init {
	value 2;		value 2;
	description "init";		description "init";
	}		}
	enum up {		enum up {
	value 3;		value 3;
	description "up";		description "up";
	}		}
	}		}
	description "BFD state";		description "BFD state";
	}		}
	typedef multiplier {
			typedef bfd-multiplier {
	type uint8 {		type uint8 {
	range 1..255;		range 1..255;
	}		}
	description "Multiplier";		description "Multiplier";
	}		}
	typedef ttl {		typedef ttl {
	type uint8 {		type uint8 {
	range 1..255;		range 1..255;
	}		}
	description "Time To Live";		description "Time To Live";
	}		}
	typedef bfd-session-type {
	type enumeration {		identity bfd-path-type {
	enum ip-single-hop {
	description "IP single hop";
	}
	enum ip-multi-hop {
	description "IP multi hop";
	}
	enum te-tunnel {
	description "Traffic Engineering tunnes";
	}
	enum ldp-lsp {
	description "LDP Label Switched Path";
	}
	enum lag {
	description "Micro-BFD on LAG member links";
	}
	}
	description		description
	"BFD session type, this indicates the path type that BFD is		"Base identity for BFD path type. The session type indicates
	running on";		the type of path on which BFD is running";
	}		}
	typedef bfd-auth-algorithm {		identity bfd-path-ip-sh {
	type enumeration {		base bfd-path-type;
	enum simple-password {		description "BFD on IP single hop";
	description		}
	"Simple password";		identity bfd-path-ip-mh {
	}		base bfd-path-type;
			description "BFD on IP multi hop";
	enum keyed-md5 {		}
	description		identity bfd-path-mpls-te {
	"Keyed message Digest 5";		base bfd-path-type;
	}		description "BFD on MPLS Traffic Engineering";
			}
			identity bfd-path-mpls-lsp {
			base bfd-path-type;
			description "BFD on MPLS Label Switched Path";
			}
			identity bfd-path-lag {
			base bfd-path-type;
			description "Micro-BFD on LAG member links";
			}
	enum meticulous-keyed-md5 {		identity bfd-encap-type {
	description		description
	"Meticulous keyed message Digest 5";		"Base identity for BFD encapsulation type.";
	}		}
			identity bfd-encap-ip {
			base bfd-encap-type;
			description "BFD with IP encapsulation.";
			}
	enum keyed-sha-1 {		feature bfd-authentication {
	description		description "BFD authentication supported";
	"Keyed secure hash algorithm (SHA1) ";		}
			identity bfd-auth-replay-protection {
			description
			"Base identity for BFD authentication replay protection";
			}
			identity bfd-auth-replay-protection-non-meticulous {
			base bfd-auth-replay-protection;
			description "Non-meticulous (see RFC5880)";
			}
			identity bfd-auth-replay-protection-meticulous {
			base bfd-auth-replay-protection;
			description "Meticulous (see RFC5880)";
			}
			grouping bfd-auth-parms {
			description
			"Grouping for BFD authentication parameters
			(see section 6.7 of RFC5880).";
			container authentication-parms {
			if-feature bfd-authentication;
			presence
			"Enables BFD authentication (see section 6.7 of RFC5880).";
			description "Parameters for BFD authentication";
			leaf key-chain {
			type kc:key-chain-ref;
			description "Name of key-chain";
	}		}
	enum meticulous-keyed-sha-1 {		leaf replay-protection {
			type identityref {
			base bfd-auth-replay-protection;
			}
	description		description
	"Meticulous keyed secure hash algorithm (SHA1) ";		"Protection against replays";
	}		}
	}		}
	description "Authentication algorithm";
	}
	feature bfd-interface-config {
	description "BFD per-interface config supported";
	}
	feature bfd-authentication {
	description "BFD authentication supported";
	}		}
	grouping bfd-grouping-base-cfg-parms {		grouping bfd-grouping-base-cfg-parms {
	description "BFD grouping for base config parameters";		description "BFD grouping for base config parameters";
	leaf local-multiplier {		leaf local-multiplier {
	type multiplier;		type bfd-multiplier;
	default 3;		default 3;
	description "Multiplier transmitted by local system";		description "Multiplier transmitted by local system";
	}		}
	choice interval-config-type {		choice interval-config-type {
	description		description
	"Two interval values or 1 value used for both tx and rx";		"Two interval values or 1 value used for both tx and rx";
	case tx-rx-intervals {		case tx-rx-intervals {
	leaf desired-min-tx-interval {		leaf desired-min-tx-interval {
	type uint32;		type uint32;
	units microseconds;		units microseconds;
	mandatory true;		mandatory true;
	description		description
	"Desired minimum transmit interval of control packets";		"Desired minimum transmit interval of control packets";
	skipping to change at page 20, line 40 ¶		skipping to change at page 25, line 14 ¶
	type uint32;		type uint32;
	units microseconds;		units microseconds;
	mandatory true;		mandatory true;
	description		description
	"Desired minimum transmit interval and required " +		"Desired minimum transmit interval and required " +
	"minimum receive interval of control packets";		"minimum receive interval of control packets";
	}		}
	}		}
	}		}
	}		}
	grouping bfd-grouping-common-cfg-parms {		grouping bfd-grouping-common-cfg-parms {
	description "BFD grouping for common config parameters";		description "BFD grouping for common config parameters";
	uses bfd-grouping-base-cfg-parms;		uses bfd-grouping-base-cfg-parms;
	leaf demand-enabled {		leaf demand-enabled {
	type boolean;		type boolean;
	default false;		default false;
	description "To enbale demand mode";		description "To enable demand mode";
	}		}
	leaf enable-authentication {
			leaf admin-down {
	type boolean;		type boolean;
	default false;		default false;
	description		description
	"If set, the Authentication Section is present and the		"Is the BFD session administratively down";
	session is to be authenticated (see RFC5880 section 6.7
	for details).";
	}
	container authentication-parms {
	if-feature bfd-authentication;
	description "Parameters for authentication";
	leaf key-chain-name {
	type string;
	must "../algorithm" {
	error-message
	"May not be configured without algorithm";
	description "Requires algorithm";
	}
	description
	"Key chain name";
	}
	leaf algorithm {
	type bfd-auth-algorithm;
	must "../key-chain" {
	error-message
	"May not be configured without key-chain";
	description "Requires key-chain";
	}
	description "Authentication algorithm to be used";
	}
	}		}
			uses bfd-auth-parms;
	}		}
	grouping bfd-grouping-echo-cfg-parms {		grouping bfd-grouping-echo-cfg-parms {
	description "BFD grouping for echo config parameters";		description "BFD grouping for echo config parameters";
	leaf desired-min-echo-tx-interval {		leaf desired-min-echo-tx-interval {
	type uint32;		type uint32;
	units microseconds;		units microseconds;
	default 0;		default 0;
	description "Desired minumum transmit interval for echo";		description "Desired minumum transmit interval for echo";
	}		}
	leaf required-min-echo-rx-interval {		leaf required-min-echo-rx-interval {
	type uint32;		type uint32;
	units microseconds;		units microseconds;
	default 0;		default 0;
	description "Required minimum receive interval for echo";		description "Required minimum receive interval for echo";
	}		}
	}		}
	grouping bfd-client-base-cfg-parms {		grouping bfd-client-base-cfg-parms {
	description		description
	"BFD grouping for base config parameters which could be used		"BFD grouping which could be used by a protocol which
	by a protocol which is a client of BFD";		is a client of BFD to enable its use of BFD";
	container bfd-cfg {		container bfd-cfg {
	description "BFD configuration";		description "BFD configuration";
	leaf enabled {		leaf enabled {
	type boolean;		type boolean;
	default false;		default false;
	description "True if BFD is enabled";		description "True if BFD is enabled";
	}		}
	uses bfd-grouping-base-cfg-parms;
	}		}
	}		}
	grouping bfd-all-session {		grouping bfd-all-session {
	description "BFD session operational information";		description "BFD session operational information";
	leaf session-type {		leaf path-type {
	type bfd-session-type;		type identityref {
			base bfd-path-type;
			}
	description		description
	"BFD session type, this indicates the path type that BFD is		"BFD session type, this indicates the path type that BFD is
	running on";		running on";
	}		}
	leaf local-discriminator {		leaf local-discriminator {
	type discriminator;		type bfd-discriminator;
	description "Local discriminator";		description "Local discriminator";
	}		}
	leaf remote-discriminator {		leaf remote-discriminator {
	type discriminator;		type bfd-discriminator;
	description "Remote discriminator";		description "Remote discriminator";
	}		}
	leaf remote-multiplier {		leaf remote-multiplier {
	type multiplier;		type bfd-multiplier;
	description "Remote multiplier";		description "Remote multiplier";
	}		}
	leaf out-interface {		leaf out-interface {
	type if:interface-ref;		type if:interface-ref;
	description "Outgoing physical interface name";		description "Outgoing physical interface name";
	}		}
	leaf demand-capability {		leaf demand-capability {
	type boolean;		type boolean;
	description "Local demand mode capability";		description "Local demand mode capability";
	}		}
	skipping to change at page 22, line 46 ¶		skipping to change at page 27, line 4 ¶
	type if:interface-ref;		type if:interface-ref;
	description "Outgoing physical interface name";		description "Outgoing physical interface name";
	}		}
	leaf demand-capability {		leaf demand-capability {
	type boolean;		type boolean;
	description "Local demand mode capability";		description "Local demand mode capability";
	}		}
	leaf source-port {		leaf source-port {
	type inet:port-number;		type inet:port-number;
	description "Source UDP port";		description "Source UDP port";
	}		}
	leaf dest-port {		leaf dest-port {
	type inet:port-number;		type inet:port-number;
	description "Destination UDP port";		description "Destination UDP port";
	}		}
	list session-running {
			container session-running {
	description "BFD session running information";		description "BFD session running information";
	leaf session-index {		leaf session-index {
	type uint32;		type uint32;
	description		description
	"An index used to uniquely identify BFD sessions";		"An index used to uniquely identify BFD sessions";
	}		}
	leaf local-state {		leaf local-state {
	type state;		type bfd-state;
	description "Local state";		description "Local state";
	}		}
	leaf remote-state {		leaf remote-state {
	type state;		type bfd-state;
	description "Remote state";		description "Remote state";
	}		}
	leaf local-diagnostic {		leaf local-diagnostic {
	type diagnostic;		type bfd-diagnostic;
	description "Local diagnostic";		description "Local diagnostic";
	}		}
	leaf remote-diagnostic {		leaf remote-diagnostic {
	type diagnostic;		type bfd-diagnostic;
	description "Remote diagnostic";		description "Remote diagnostic";
	}		}
	leaf detection-mode {		leaf detection-mode {
	type enumeration {		type enumeration {
	enum async-with-echo {		enum async-with-echo {
	value "1";		value "1";
	description "Async with echo";		description "Async with echo";
	}		}
	enum async-without-echo {		enum async-without-echo {
	value "2";		value "2";
	skipping to change at page 24, line 8 ¶		skipping to change at page 28, line 16 ¶
	leaf negotiated-tx-interval {		leaf negotiated-tx-interval {
	type uint32;		type uint32;
	units microseconds;		units microseconds;
	description "Negotiated transmit interval";		description "Negotiated transmit interval";
	}		}
	leaf negotiated-rx-interval {		leaf negotiated-rx-interval {
	type uint32;		type uint32;
	units microseconds;		units microseconds;
	description "Negotiated receive interval";		description "Negotiated receive interval";
	}		}
	leaf negotiated-echo-tx-interval {		leaf echo-tx-interval-in-use {
			when "../../path-type = 'bfd-path-ip-sh'" {
			description
			"Echo is supported for IP single-hop only.";
			}
	type uint32;		type uint32;
	units microseconds;		units microseconds;
	description "Negotiated echo transmit interval";		description "Echo transmit interval in use";
	}		}
	leaf detection-time {		leaf detection-time {
	type uint32;		type uint32;
	units microseconds;		units microseconds;
	description "Detection time";		description "Detection time";
	}		}
	}		}
	list sesssion-statistics {
	description "BFD session statistics";		container sesssion-statistics {
			description "BFD per-session statistics";
	leaf create-time {		leaf create-time {
	type yang:date-and-time;		type yang:date-and-time;
	description		description
	"Time and date when session was created";		"Time and date when session was created";
	}		}
	leaf last-down-time {		leaf last-down-time {
	type yang:date-and-time;		type yang:date-and-time;
	description		description
	"Time and date of last time the session went down";		"Time and date of last time the session went down";
	}		}
	skipping to change at page 25, line 14 ¶		skipping to change at page 29, line 28 ¶
	leaf receive-bad-packet {		leaf receive-bad-packet {
	type uint64;		type uint64;
	description "Received bad packet count";		description "Received bad packet count";
	}		}
	leaf send-failed-packet {		leaf send-failed-packet {
	type uint64;		type uint64;
	description "Packet Failed to Send Count";		description "Packet Failed to Send Count";
	}		}
	}		}
	}		}
			grouping bfd-session-statistics {
			description "Grouping for session counters";
			container bfd-session-statistics {
			description "BFD session counters";
			leaf session-count {
			type uint32;
			description "Number of sessions";
			}
			leaf session-up-count {
			type uint32;
			description "Count of sessions which are up";
			}
			leaf session-down-count {
			type uint32;
			description "Count of sessions which are down";
			}
			leaf session-admin-down-count {
			type uint32;
			description "Count of sessions which are admin-down";
			}
			}
			}
			grouping bfd-notification-parms {
			description
			"This group describes common parameters that will be sent " +
			"as part of BFD notification";
			leaf local-discr {
			type bfd-discriminator;
			description "BFD local discriminator";
			}
			leaf remote-discr {
			type bfd-discriminator;
			description "BFD remote discriminator";
			}
			leaf new-state {
			type bfd-state;
			description "Current BFD state";
			}
			leaf state-change-reason {
			type string;
			description "BFD state change reason";
			}
			leaf time-in-previous-state {
			type string;
			description
			"How long the BFD session was in the previous state";
			}
			leaf dest-addr {
			type inet:ip-address;
			description "BFD peer address";
			}
			leaf source-addr {
			type inet:ip-address;
			description "BFD local address";
			}
			leaf session-index {
			type uint32;
			description "An index used to uniquely identify BFD sessions";
			}
			leaf path-type {
			type identityref {
			base bfd-path-type;
			}
			description "BFD path type";
			}
			}
	augment "/rt:routing/rt:routing-instance/rt:routing-protocols/"		augment "/rt:routing/rt:routing-instance/rt:routing-protocols/"
	+ "rt:routing-protocol" {		+ "rt:routing-protocol" {
	when "rt:type = 'bfd:bfd'" {		when "rt:type = 'bfd:bfd'" {
	description		description
	"This augment is only valid for a protocol instance		"This augment is only valid for a protocol instance
	of BFD.";		of BFD.";
	}		}
	description "BFD augmentation.";		description "BFD augmentation.";
	container bfd {		container bfd {
	description "BFD top-level container";		presence "BFD";
	container bfd-cfg {		description "BFD top level container";
			container config {
			description "BFD configuration container";
			}
			container oper {
			config "false";
			description
			"BFD operational container for this routing instance";
			uses bfd-session-statistics;
			}
			}
			}
			container bfd {
			presence "BFD";
			description "BFD top level container";
			container config {
			description "BFD configuration container";
			}
			container oper {
			config "false";
			description "BFD operational container.";
			uses bfd-session-statistics;
			}
			}
			}
			<CODE ENDS>
			2.14. BFD IP single-hop Yang Module
			<CODE BEGINS> file "ietf-bfd-ip-sh@2016-02-17.yang"
			module ietf-bfd-ip-sh {
			namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-ip-sh";
			// replace with IANA namespace when assigned
			prefix "bfd-ip-sh";
			import ietf-bfd {
			prefix "bfd";
			}
			import ietf-interfaces {
			prefix "if";
			}
			import ietf-inet-types {
			prefix "inet";
			}
			import ietf-routing {
			prefix "rt";
			}
			organization "IETF BFD Working Group";
			contact
			"WG Web: <http://tools.ietf.org/wg/bfd>
			WG List: <rtg-bfd@ietf.org>
			WG Chair: Jeff Haas
			WG Chair: Reshad Rahman
			Editor: Lianshu Zheng and Reshad Rahman";
			description
			"This module contains the YANG definition for BFD IP single-hop
			as per RFC5881.";
			revision 2016-02-17 {
			description "Initial revision.";
			reference "RFC XXXX: A YANG data model for BFD IP single-hop";
			}
			augment "/bfd:bfd" {
			description "BFD augmentation for IP single-hop";
			container ip-sh {
			description "BFD IP single-hop top level container";
			container config {
			description "BFD IP single-hop configuration container";
			}
			container oper {
			config "false";
			description "BFD IP single-hop operational container";
			uses bfd:bfd-session-statistics;
			}
			}
			}
			augment "/rt:routing/rt:routing-instance/rt:routing-protocols/"
			+ "rt:routing-protocol/bfd:bfd" {
			description "BFD augmentation for IP single-hop.";
			container ip-sh {
			description "BFD IP single-hop container";
			container config {
	description "BFD configuration";		description "BFD configuration";
	container bfd-session-cfg {		container session-cfg {
	description "BFD session configuration";		description "BFD IP single-hop session configuration";
	list session-ip-mh {
			list sessions {
			key "interface dest-addr";
			description "List of IP single-hop sessions";
			leaf interface {
			type if:interface-ref;
			description
			"Interface on which the BFD session is running.";
			}
			leaf dest-addr {
			type inet:ip-address;
			description "IP address of the peer";
			}
			leaf source-addr {
			type inet:ip-address;
			description "Local address";
			}
			uses bfd:bfd-grouping-common-cfg-parms;
			uses bfd:bfd-grouping-echo-cfg-parms;
			}
			}
			}
			container oper {
			config "false";
			description "BFD operational container";
			uses bfd:bfd-session-statistics;
			list sessions {
			key "interface dest-addr";
			description "BFD IP single-hop sessions";
			leaf interface {
			type if:interface-ref;
			description
			"Interface on which the BFD session is running.";
			}
			leaf dest-addr {
			type inet:ip-address;
			description "BFD peer address";
			}
			leaf source-addr {
			type inet:ip-address;
			description "BFD source address";
			}
			uses bfd:bfd-all-session;
			}
			}
			}
			}
			notification bfd-singlehop-notification {
			description
			"Notification for BFD single-hop session state change. An " +
			"implementation may rate-limit notifications, e.g. when a" +
			"session is continuously changing state.";
			uses bfd:bfd-notification-parms;
			leaf interface {
			type if:interface-ref;
			description "Interface to which this BFD session belongs to";
			}
			leaf echo-enabled {
			type boolean;
			description "Was echo enabled for BFD";
			}
			}
			}
			<CODE ENDS>
			2.15. BFD IP multi-hop Yang Module
			<CODE BEGINS> file "ietf-bfd-ip-mh@2016-02-17.yang"
			module ietf-bfd-ip-mh {
			namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-ip-mh";
			// replace with IANA namespace when assigned
			prefix "bfd-ip-mh";
			import ietf-bfd {
			prefix "bfd";
			}
			import ietf-inet-types {
			prefix "inet";
			}
			import ietf-routing {
			prefix "rt";
			}
			organization "IETF BFD Working Group";
			contact
			"WG Web: <http://tools.ietf.org/wg/bfd>
			WG List: <rtg-bfd@ietf.org>
			WG Chair: Jeff Haas
			WG Chair: Reshad Rahman
			Editor: Lianshu Zheng and Reshad Rahman";
			description
			"This module contains the YANG definition for BFD IP multi-hop
			asper RFC5883.";
			revision 2016-02-17 {
			description "Initial revision.";
			reference "RFC XXXX: A YANG data model for BFD IP multi-hop";
			}
			augment "/bfd:bfd" {
			description "BFD augmentation for IP multi-hop";
			container ip-mh {
			description "BFD IP multi-hop top level container";
			container config {
			description "BFD IP multi-hop configuration container";
			}
			container oper {
			config "false";
			description "BFD IP multi-hop operational container";
			uses bfd:bfd-session-statistics;
			}
			}
			}
			augment "/rt:routing/rt:routing-instance/rt:routing-protocols/"
			+ "rt:routing-protocol/bfd:bfd" {
			when "rt:type = 'bfd:bfd'" {
			description
			"This augment is only valid for a protocol instance
			of BFD.";
			}
			description "BFD augmentation for IP multi-hop.";
			container ip-mh {
			description "BFD IP multi-hop container";
			container config {
			description "BFD configuration";
			container session-cfg {
			description "BFD IP multi-hop session configuration";
			list sessions {
	key "source-addr dest-addr";		key "source-addr dest-addr";
	description "List of IP multi-hop sessions";		description "List of IP multi-hop sessions";
	leaf source-addr {		leaf source-addr {
	type inet:ip-address;		type inet:ip-address;
	description		description
	"Local IP address";		"Local IP address";
	}		}
	leaf dest-addr {		leaf dest-addr {
	type inet:ip-address;		type inet:ip-address;
	description		description
	"IP address of the peer";		"IP address of the peer";
	}		}
	leaf admin-down {		uses bfd:bfd-grouping-common-cfg-parms;
	type boolean;
	default false;
	description
	"Is the BFD session administratively down";
	}
	uses bfd-grouping-common-cfg-parms;
	leaf tx-ttl {		leaf tx-ttl {
	type ttl;		type bfd:ttl;
	default 255;		default 255;
	description "TTL of outgoing BFD control packets";		description "TTL of outgoing BFD control packets";
	}		}
	leaf rx-ttl {		leaf rx-ttl {
	type ttl;		type bfd:ttl;
	mandatory true;		mandatory true;
	description		description
	"Minimum allowed TTL value for incoming BFD control		"Minimum allowed TTL value for incoming BFD control
	packets";		packets";
	}		}
	}		}
	}		}
	list bfd-interface-cfg {
	if-feature bfd-interface-config;
	key interface;
	description "Per-interface BFD configuration";
	leaf interface {
	type if:interface-ref;
	description "Interface";
	}
	uses bfd-grouping-common-cfg-parms;
	uses bfd-grouping-echo-cfg-parms;
	}
	}		}
	container bfd-oper {
			container oper {
	config "false";		config "false";
	description "BFD operational container";		description "BFD operational container";
	container bfd-session-statistics {		container bfd-session-statistics {
	description "BFD session counters";		description "BFD session counters";
	leaf ip-sh-session-num {		uses bfd:bfd-session-statistics;
	type uint32;
	description "IP single hop session number";
	}
	leaf ip-mh-session-num {
	type uint32;
	description "IP multi hop session Number";
	}
	leaf total-session-num {
	type uint32;
	description "Total session number";
	}
	leaf session-up-num {
	type uint32;
	description "Session up number";
	}
	leaf sess-down-num {
	type uint32;
	description "Session down number";
	}
	leaf sess-admin-down-num {
	type uint32;
	description "Session admin-down number";
	}
	}		}
	container bfd-session-lists {		list session-group {
			key "source-addr dest-addr";
	description		description
	"Contains multiple session lists, one per type";		"BFD IP multi-hop group of sessions. A group of " +
	list session-ip-sh {		"sessions is between 1 source and 1 destination, " +
	key "interface dest-addr";		"each session has a different field in UDP/IP hdr for " +
	description "BFD IP single-hop sessions";		"ECMP.";
	leaf interface {		leaf source-addr {
	type if:interface-ref;		type inet:ip-address;
	description		description "BFD source address";
	"Interface on which the BFD session is running.";
	}
	leaf dest-addr {
	type inet:ip-address;
	description "BFD peer address";
	}
	leaf source-addr {
	type inet:ip-address;
	description "BFD source address";
	}
	uses bfd-all-session;
	}
	list session-ip-mh-group {
	key "source-addr dest-addr";
	description
	"BFD IP multi-hop group of sessions. A group of " +
	"sessions is between 1 source and 1 destination, " +
	"each session uses a different source UDP port for " +
	"ECMP.";
	leaf source-addr {
	type inet:ip-address;
	description "BFD source address";
	}
	leaf dest-addr {
	type inet:ip-address;
	description "BFD peer address";
	}
	list session-ip-mh {
	key "source-port";
	description
	"The BFD sessions between a source and a. " +
	"destination. Source UDP port is unique for " +
	"each session in the group.";
	leaf ttl {
	type ttl;
	description "TTL of outgoing packets";
	}
	uses bfd-all-session;
	}
	}		}
	list session-te-tunnel {		leaf dest-addr {
	key "tunnel-name";		type inet:ip-address;
	description "BFD over TE tunnel";		description "BFD peer address";
	leaf tunnel-name {
	type string;
	description "Name of TE tunnel";
	}
	uses bfd-all-session;
	}		}
	list session-ldp-lsp-group {		list sessions {
	key "ldp-fec";		key "local-discriminator";
	description		description
	"BFD over LDP LSP group of sessions. A group of " +		"The BFD sessions between a source and a. " +
	"sessions is to one LDP FEC, each session uses a " +		"destination. Local discriminator is unique for " +
	"different source UDP port for ECMP.";		"each session in the group.";
	leaf ldp-fec {		leaf ttl {
	type inet:ip-prefix;		type bfd:ttl;
	description "LDP FEC";		description "TTL of outgoing packets";
	}
	list session-ldp-lsp {
	key "source-port";
	description
	"The BFD sessions on an LDP FEC. Source UDP " +
	"port is unique for each session in the group.";
	leaf ttl {
	type ttl;
	description "TTL of outgoing packets";
	}
	uses bfd-all-session;
	}		}
			uses bfd:bfd-all-session;
	}		}
	list session-lag {		}
			}
			}
			}
			notification bfd-multihop-notification {
			description
			"Notification for BFD multi-hop session state change. An " +
			"implementation may rate-limit notifications, e.g. when a" +
			"session is continuously changing state.";
			uses bfd:bfd-notification-parms;
			leaf routing-instance {
			type rt:routing-instance-ref;
			description "Routing instance";
			}
			}
			}
			<CODE ENDS>
			2.16. BFD over LAG Yang Module
			<CODE BEGINS> file "ietf-bfd-lag@2016-02-17.yang"
			module ietf-bfd-lag {
			namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-lag";
			// replace with IANA namespace when assigned
			prefix "bfd-lag";
			import ietf-bfd {
			prefix "bfd";
			}
			import ietf-interfaces {
			prefix "if";
			}
			import ietf-inet-types {
			prefix "inet";
			}
			organization "IETF BFD Working Group";
			contact
			"WG Web: <http://tools.ietf.org/wg/bfd>
			WG List: <rtg-bfd@ietf.org>
			WG Chair: Jeff Haas
			WG Chair: Reshad Rahman
			Editor: Lianshu Zheng and Reshad Rahman";
			description
			"This module contains the YANG definition for BFD over LAG
			interfaces as per RFC7130.";
			revision 2016-02-17 {
			description "Initial revision.";
			reference "RFC XXXX: A YANG data model for BFD over LAG";
			}
			augment "/bfd:bfd" {
			description "BFD augmentation for LAG";
			container lag {
			description "BFD over LAG top level container";
			container config {
			description "BFD over LAG configuration container";
			container session-cfg {
			description "BFD over LAG session configuration";
			list sessions {
	key "lag-name";		key "lag-name";
	description "A LAG interface on which BFD is running";		description "A LAG interface on which BFD is running";
	leaf lag-name {		leaf lag-name {
	type if:interface-ref ;		type if:interface-ref ;
	description "Name of the LAG";		description "Name of the LAG";
	}		}
	list session-lag-micro {		leaf ipv4-dest-addr {
			type inet:ipv4-address;
			description
			"IPv4 address of the peer, for IPv4 micro-BFD.";
			}
			leaf ipv6-dest-addr {
			type inet:ipv6-address;
			description
			"IPv6 address of the peer, for IPv6 micro-BFD.";
			}
			uses bfd:bfd-grouping-common-cfg-parms;
			}
			}
			}
			container oper {
			config "false";
			description "BFD over LAG operational container.";
			container micro-bfd-ipv4-session-statistics {
			description "Micro-BFD IPv4 session counters";
			uses bfd:bfd-session-statistics;
			}
			container micro-bfd-ipv6-session-statistics {
			description "Micro-BFD IPv6 session counters";
			uses bfd:bfd-session-statistics;
			}
			list session-lag {
			key "lag-name";
			description "A LAG interface on which BFD is running";
			leaf lag-name {
			type if:interface-ref ;
			description "Name of the LAG";
			}
			leaf use-ipv4 {
			type boolean;
			description "Using IPv4 micro-BFD.";
			}
			leaf use-ipv6 {
			type boolean;
			description "Using IPv6 micro-BFD.";
			}
			list member-links {
	key "member-link";		key "member-link";
			description
			"Micro-BFD over LAG. This represents one member link";
			leaf member-link {
			type if:interface-ref;
	description		description
	"Micro-BFD over LAG. This represents BFD " +		"Member link on which micro-BFD is running";
	"over one member link";		}
	leaf member-link {		container micro-bfd-ipv4 {
	type if:interface-ref;		when "../use-ipv4 = 'true'" {
	description		description "Needed only if IPv4 is used.";
	"Member link on which micro-BFD is running";
	}		}
	uses bfd-all-session;		description
			"Micro-BFD IPv4 session state on member link";
			uses bfd:bfd-all-session;
			}
			container micro-bfd-ipv6 {
			when "../use-ipv6 = 'true'" {
			description "Needed only if IPv6 is used.";
			}
			description
			"Micro-BFD IPv6 session state on member link";
			uses bfd:bfd-all-session;
	}		}
	}		}
	}		}
	}		}
	}		}
	}		}
			notification bfd-lag-notification {
	grouping bfd-notification-parms {
	description		description
	"This group describes common parameters that will be sent " +		"Notification for BFD over LAG session state change. " +
	"as part of BFD notification";		"An implementation may rate-limit notifications, e.g. when a" +
			"session is continuously changing state.";
	leaf local-discr {		uses bfd:bfd-notification-parms;
	type discriminator;
	description "BFD local discriminator";
	}
	leaf remote-discr {		leaf lag-name {
	type discriminator;		type if:interface-ref;
	description "BFD remote discriminator";		description "LAG interface name";
	}		}
	leaf new-state {		leaf member-link {
	type state;		type if:interface-ref;
	description "Current BFD state";		description "Member link on which BFD is running";
	}		}
			}
			}
			<CODE ENDS>
	leaf state-change-reason {		2.17. BFD over MPLS Yang Module
	type string;
	description "BFD state change reason";
	}
	leaf time-in-previous-state {		<CODE BEGINS> file "ietf-bfd-mpls@2016-02-17.yang"
	type string;		module ietf-bfd-mpls {
	description		namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-mpls";
	"How long the BFD session was in the previous state";		// replace with IANA namespace when assigned
	}		prefix "bfd-mpls";
	leaf dest-addr {		import ietf-bfd {
	type inet:ip-address;		prefix "bfd";
	description "BFD peer address";		}
	}		import ietf-inet-types {
	leaf source-addr {		prefix "inet";
	type inet:ip-address;
	description "BFD local address";
	}
	leaf session-index {
	type uint32;
	description "An index used to uniquely identify BFD sessions";
	}
	leaf session-type {
	type bfd-session-type;
	description "BFD session type";
	}
	}		}
	notification bfd-singlehop-notification {		import ietf-routing {
	description		prefix "rt";
	"Notification for BFD single-hop session state change. An " +		}
	"implementation may rate-limit notifications, e.g. when a" +		organization "IETF BFD Working Group";
	"session is continuously changing state.";
	uses bfd-notification-parms;
	leaf interface {		contact
	type if:interface-ref;		"WG Web: <http://tools.ietf.org/wg/bfd>
	description "Interface to which this BFD session belongs to";		WG List: <rtg-bfd@ietf.org>
	}		WG Chair: Jeff Haas
			WG Chair: Reshad Rahman
			Editor: Lianshu Zheng and Reshad Rahman";
	leaf echo-enabled {		description
	type boolean;		"This module contains the YANG definition for BFD parameters for
	description "Was echo enabled for BFD";		MPLS LSPs as per RFC5884.";
	}
			revision 2016-02-17 {
			description "Initial revision.";
			reference "RFC XXXX: A YANG data model for BFD over MPLS LSPs";
	}		}
	notification bfd-multihop-notification {		identity bfd-encap-gach {
			base bfd:bfd-encap-type;
	description		description
	"Notification for BFD multi-hop session state change. An " +		"BFD with G-ACh encapsulation as per RFC5586.";
	"implementation may rate-limit notifications, e.g. when a" +
	"session is continuously changing state.";
	uses bfd-notification-parms;
	}		}
	notification bfd-te-tunnel-notification {
			identity bfd-encap-ip-gach {
			base bfd:bfd-encap-type;
	description		description
	"Notification for BFD over TE tunnel session state change. " +		"BFD with IP and G-ACh encapsulation as per RFC5586.";
	"An implementation may rate-limit notifications, e.g. when a" +		}
	"session is continuously changing state.";
	uses bfd-notification-parms;		grouping bfd-encap-cfg {
	leaf tunnel-name {		description "Configuration for BFD encapsulation";
	type string;
	description "TE tunnel to which this BFD session belongs to";		leaf encap {
			type identityref {
			base bfd:bfd-encap-type;
			}
			default bfd:bfd-encap-ip;
			description "BFD encapsulation";
	}		}
	}		}
	notification bfd-ldp-lsp-notification {
	description
	"Notification for BFD over LDP LSP session state change. " +
	"An implementation may rate-limit notifications, e.g. when a" +
	"session is continuously changing state.";
	uses bfd-notification-parms;
	leaf ldp-fec {		grouping bfd-mpls-dest-address {
	type inet:ip-prefix;		description "Destination address as per RFC5884";
	description "LDP FEC";
			leaf mpls-dest-address {
			type inet:ip-address;
			config "false";
			description
			"Destination address as per RFC5884.
			Needed if IP encapsulation is used";
	}		}
	leaf source-port {		}
	type inet:port-number;
	description "Source UDP port";		augment "/bfd:bfd" {
			description "BFD augmentation for MPLS";
			container mpls {
			description "BFD MPLS top level container";
			container config {
			description "BFD MPLS configuration container";
			container egress {
			description "Egress configuration";
			uses bfd:bfd-grouping-base-cfg-parms;
			uses bfd:bfd-auth-parms;
			}
			}
			container oper {
			config "false";
			description "BFD MPLS operational container";
			uses bfd:bfd-session-statistics;
			}
	}		}
	}		}
	notification bfd-lag-notification {
			augment "/rt:routing/rt:routing-instance/rt:routing-protocols/"
			+ "rt:routing-protocol/bfd:bfd" {
			description "BFD augmentation for MPLS.";
			container mpls {
			description "BFD MPLS container";
			container config {
			description "BFD MPLS configuration container";
			container session-cfg {
			description "BFD MPLS session configuration";
			list sessions {
			key "mpls-fec";
			description "List of BFD MPLS sessions";
			leaf mpls-fec {
			type inet:ip-address;
			description "MPLS FEC";
			}
			uses bfd:bfd-grouping-common-cfg-parms;
			}
			}
			}
			container oper {
			config "false";
			description "BFD MPLS operational container";
			uses bfd:bfd-session-statistics;
			list session-group {
			key "mpls-fec";
			description
			"BFD MPLS group of sessions. A group of sessions is" +
			"for 1 FEC, each session has a different field in " +
			"UDP/IP hdr for ECMP.";
			leaf mpls-fec {
			type inet:ip-address;
			description "MPLS-FEC";
			}
			list sessions {
			key "local-discriminator";
			description
			"The BFD sessions for an MPLS FEC. Local " +
			"discriminator is unique for each session in the " +
			"group.";
			uses bfd:bfd-all-session;
			uses bfd-mpls:bfd-mpls-dest-address;
			}
			}
			}
			}
			}
			notification bfd-mpls-notification {
	description		description
	"Notification for BFD over LAG session state change. " +		"Notification for BFD over MPLS FEC session state change. " +
	"An implementation may rate-limit notifications, e.g. when a" +		"An implementation may rate-limit notifications, e.g. when a" +
	"session is continuously changing state.";		"session is continuously changing state.";
	uses bfd-notification-parms;
	leaf lag-name {		uses bfd:bfd-notification-parms;
	type if:interface-ref;
	description "LAG interface name";		leaf routing-instance {
			type rt:routing-instance-ref;
			description "Routing instance";
	}		}
	leaf member-link {
	type if:interface-ref;		leaf mpls-dest-address {
	description "Member link on which BFD is running";		type inet:ip-address;
			description
			"Destination address as per RFC5884.
			Needed if IP encapsulation is used";
	}		}
	}		}
	}		}
	<CODE ENDS>		<CODE ENDS>
	2.11. BFD Client Example Configuration Yang Module		2.18. BFD over MPLS-TEYang Module
	module example-bfd-routing-app {		<CODE BEGINS> file "ietf-bfd-mpls-te@2016-02-17.yang"
	namespace "urn:ietf:params:xml:ns:yang:example-bfd-routing-app";		module ietf-bfd-mpls-te {
	prefix bfd-routing-app;		namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-mpls-te";
			// replace with IANA namespace when assigned
			prefix "bfd-mpls-te";
	import ietf-bfd {		import ietf-bfd {
	prefix "bfd";		prefix "bfd";
			}
	}		import ietf-bfd-mpls {
			prefix "bfd-mpls";
			}
	import ietf-interfaces {		import ietf-te {
	prefix "if";		prefix "te";
	}		}
	organization		organization "IETF BFD Working Group";
	"ACME";
	contact
	"acme@acme.com";
	description		contact
	"Testing BFD grouping (simulating a routing application)";		"WG Web: <http://tools.ietf.org/wg/bfd>
			WG List: <rtg-bfd@ietf.org>
			WG Chair: Jeff Haas
			WG Chair: Reshad Rahman
			Editor: Lianshu Zheng and Reshad Rahman";
	revision 2015-07-01 {		description
	description "Initial revision.";		"This module contains the YANG definition for BFD parameters for
	reference "RFC XXXX: An example BFD routing application";		MPLS Traffic Engineering as per RFC5884.";
	}
	feature routing-app-bfd {		revision 2016-02-04 {
	description "BFD configuration under routing-app";		description "Initial revision.";
	}		reference "RFC XXXX: A YANG data model for BFD over MPLS-TE";
			}
	list area {		augment "/bfd:bfd" {
	key "area-id";		description "BFD augmentation for MPLS-TE";
			container mpls-te {
			description "BFD MPLS-TE top level container";
			container config {
			description "BFD MPLS-TE configuration container";
	description "Specify a routing area.";		container egress {
			description "Egress configuration";
	leaf area-id {		uses bfd:bfd-grouping-base-cfg-parms;
	type uint32;
	description "Area";
	}
	uses bfd:bfd-client-base-cfg-parms {		uses bfd:bfd-auth-parms;
	if-feature routing-app-bfd;		}
	}		}
	list interface {		container oper {
	key "interface";		config "false";
	description "List of interfaces";		description "BFD operational container";
	leaf interface {		uses bfd:bfd-session-statistics;
	type if:interface-ref;		}
	description "Interface";		}
	}		}
	uses bfd:bfd-client-base-cfg-parms {
	if-feature routing-app-bfd;
	}
	}
	}		augment "/te:te/te:tunnels/te:tunnel/te:config" {
			description "BFD configuration on MPLS-TE tunnel.";
			uses bfd:bfd-grouping-common-cfg-parms;
			uses bfd-mpls:bfd-encap-cfg;
			}
			augment "/te:te/te:lsps-state/te:lsp" {
			when "/te:te/te:lsps-state/te:lsp/te:origin-type != 'transit'" {
			description "BFD information not needed at transit points";
			}
			description "BFD state information on MPLS-TE LSP.";
			uses bfd:bfd-all-session;
			uses bfd-mpls:bfd-mpls-dest-address;
			}
			notification bfd-mpls-te-notification {
			description
			"Notification for BFD over MPLS-TE session state change. " +
			"An implementation may rate-limit notifications, e.g. when a" +
			"session is continuously changing state.";
			uses bfd:bfd-notification-parms;
			uses bfd-mpls:bfd-mpls-dest-address;
			leaf tunnel-name {
			type string;
			description "MPLS-TE tunnel on which BFD was running.";
			}
			}
	}		}
			<CODE ENDS>
	2.12. Security Considerations		2.19. Security Considerations
	The YANG module defined in this memo is designed to be accessed via		The YANG module defined in this memo is designed to be accessed via
	the NETCONF protocol [RFC6241]. The lowest NETCONF layer is the		the NETCONF protocol [RFC6241]. The lowest NETCONF layer is the
	secure transport layer and the mandatory to implement secure		secure transport layer and the mandatory to implement secure
	transport is SSH [RFC6242]. The NETCONF access control model		transport is SSH [RFC6242]. The NETCONF access control model
	[RFC6536] provides the means to restrict access for particular		[RFC6536] provides the means to restrict access for particular
	NETCONF users to a pre-configured subset of all available NETCONF		NETCONF users to a pre-configured subset of all available NETCONF
	protocol operations and content.		protocol operations and content.
	The YANG module has writeable data nodes which can be used for		The YANG module has writeable data nodes which can be used for
	creation of BFD sessions and modification of BFD session parameters.		creation of BFD sessions and modification of BFD session parameters.
	The system should "police" creation of BFD sessions to prevent new		The system should "police" creation of BFD sessions to prevent new
	sessions from causing existing BFD sessions to fail. For BFD session		sessions from causing existing BFD sessions to fail. For BFD session
	modification, the BFD protocol has mechanisms in place which allow		modification, the BFD protocol has mechanisms in place which allow
	for in service modification.		for in service modification.
	2.13. IANA Considerations		2.20. IANA Considerations
	The IANA is requested to as assign a new new namespace URI from the		The IANA is requested to as assign a new new namespace URI from the
	IETF XML registry.		IETF XML registry.
	URI:TBD		URI:TBD
	2.14. Acknowledgements		2.21. Acknowledgements
	We would also like to thank Nobo Akiya and Jeff Haas for their		We would also like to thank Nobo Akiya and Jeff Haas for their
	encouragement on this work.		encouragement on this work. We would also like to thank Rakesh
			Gandhi and Tarek Saad for their help on the MPLS-TE model.
	3. References		3. References
	3.1. Normative References		3.1. Normative References
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	<http://www.rfc-editor.org/info/rfc2119>.		<http://www.rfc-editor.org/info/rfc2119>.
			[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
			"MPLS Generic Associated Channel", RFC 5586,
			DOI 10.17487/RFC5586, June 2009,
			<http://www.rfc-editor.org/info/rfc5586>.
	[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection		[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
	(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,		(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
	<http://www.rfc-editor.org/info/rfc5880>.		<http://www.rfc-editor.org/info/rfc5880>.
	[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection		[RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
	(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,		(BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881,
	DOI 10.17487/RFC5881, June 2010,		DOI 10.17487/RFC5881, June 2010,
	<http://www.rfc-editor.org/info/rfc5881>.		<http://www.rfc-editor.org/info/rfc5881>.
	[RFC5882] Katz, D. and D. Ward, "Generic Application of		[RFC5882] Katz, D. and D. Ward, "Generic Application of
	skipping to change at page 34, line 24 ¶		skipping to change at page 48, line 33 ¶
	[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection		[RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
	(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,		(BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
	June 2010, <http://www.rfc-editor.org/info/rfc5883>.		June 2010, <http://www.rfc-editor.org/info/rfc5883>.
	[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,		[RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
	"Bidirectional Forwarding Detection (BFD) for MPLS Label		"Bidirectional Forwarding Detection (BFD) for MPLS Label
	Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,		Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
	June 2010, <http://www.rfc-editor.org/info/rfc5884>.		June 2010, <http://www.rfc-editor.org/info/rfc5884>.
			[RFC5885] Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional
			Forwarding Detection (BFD) for the Pseudowire Virtual
			Circuit Connectivity Verification (VCCV)", RFC 5885,
			DOI 10.17487/RFC5885, June 2010,
			<http://www.rfc-editor.org/info/rfc5885>.
	[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for		[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
	the Network Configuration Protocol (NETCONF)", RFC 6020,		the Network Configuration Protocol (NETCONF)", RFC 6020,
	DOI 10.17487/RFC6020, October 2010,		DOI 10.17487/RFC6020, October 2010,
	<http://www.rfc-editor.org/info/rfc6020>.		<http://www.rfc-editor.org/info/rfc6020>.
	[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,		[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
	and A. Bierman, Ed., "Network Configuration Protocol		and A. Bierman, Ed., "Network Configuration Protocol
	(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,		(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
	<http://www.rfc-editor.org/info/rfc6241>.		<http://www.rfc-editor.org/info/rfc6241>.
	[RFC7130] Bhatia, M., Ed., Chen, M., Ed., Boutros, S., Ed.,		[RFC7130] Bhatia, M., Ed., Chen, M., Ed., Boutros, S., Ed.,
	Binderberger, M., Ed., and J. Haas, Ed., "Bidirectional		Binderberger, M., Ed., and J. Haas, Ed., "Bidirectional
	Forwarding Detection (BFD) on Link Aggregation Group (LAG)		Forwarding Detection (BFD) on Link Aggregation Group (LAG)
	Interfaces", RFC 7130, DOI 10.17487/RFC7130, February		Interfaces", RFC 7130, DOI 10.17487/RFC7130, February
	2014, <http://www.rfc-editor.org/info/rfc7130>.		2014, <http://www.rfc-editor.org/info/rfc7130>.
	3.2. Informative References		3.2. Informative References
	[I-D.ietf-netconf-restconf]		[I-D.ietf-netconf-restconf]
	Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF		Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
	Protocol", draft-ietf-netconf-restconf-07 (work in		Protocol", draft-ietf-netconf-restconf-09 (work in
	progress), July 2015.		progress), December 2015.
	[I-D.ietf-netmod-routing-cfg]		[I-D.ietf-netmod-routing-cfg]
	Lhotka, L. and A. Lindem, "A YANG Data Model for Routing		Lhotka, L. and A. Lindem, "A YANG Data Model for Routing
	Management", draft-ietf-netmod-routing-cfg-19 (work in		Management", draft-ietf-netmod-routing-cfg-20 (work in
	progress), May 2015.		progress), October 2015.
	Appendix A. Change log
	RFC Editor: Remove this section upon publication as an RFC.
	A.1. Changes between versions -03 and -04
	o Follow VRF-centric model
	o IP single-hop session configuration in BFD clients
	A.2. Changes between versions -02 and -03
	o Fixed date mismatch		[I-D.ietf-rtgwg-yang-key-chain]
			Lindem, A., Qu, Y., Yeung, D., Chen, H., Zhang, J., and Y.
			Yang, "Key Chain YANG Data Model", draft-ietf-rtgwg-yang-
			key-chain-01 (work in progress), February 2016.
	o Updated authors		[I-D.ietf-teas-yang-te]
			Saad, T., Gandhi, R., Liu, X., Beeram, V., Shah, H., Chen,
			X., Jones, R., and B. Wen, "A YANG Data Model for Traffic
			Engineering Tunnels and Interfaces", draft-ietf-teas-yang-
			te-02 (work in progress), October 2015.
	A.3. Changes between versions -01 and -02		Appendix A. Change log
	o Fixed errors and warnings from "pyang --ietf"		RFC Editor: Remove this section upon publication as an RFC.
	o Added appendix for "Change log"		A.1. Changes between versions -00 and -01
	A.4. Changes between versions -00 and -01		o Remove BFD configuration parameters from BFD clients, all BFD
			configuration parameters in BFD
	In the YANG module section:		o YANG module split in multiple YANG modules (one per type of
			forwarding path)
	o Added missing filename		o For BFD over MPLS-TE we augment MPLS-TE model
	o Added missing CODE ENDS		o For BFD authentication we now use key-chain in
			[I-D.ietf-rtgwg-yang-key-chain]
	Authors' Addresses		Authors' Addresses
	Lianshu Zheng (editor)		Lianshu Zheng (editor)
	Huawei Technologies		Huawei Technologies
	China		China
	Email: vero.zheng@huawei.com		Email: vero.zheng@huawei.com
	Reshad Rahman (editor)		Reshad Rahman (editor)
	skipping to change at page 36, line 4 ¶		skipping to change at page 50, line 18 ¶
	Huawei Technologies		Huawei Technologies
	China		China
	Email: vero.zheng@huawei.com		Email: vero.zheng@huawei.com
	Reshad Rahman (editor)		Reshad Rahman (editor)
	Cisco Systems		Cisco Systems
	Canada		Canada
	Email: rrahman@cisco.com		Email: rrahman@cisco.com
	Santosh Pallagatti		Santosh Pallagatti
	Juniper Networks
	India		India
	Email: santoshpk@juniper.net		Email: santosh.pallagatti@gmail.com
	Mahesh Jethanandani		Mahesh Jethanandani
	Cisco Systems		Cisco Systems
	Email: mjethanandani@gmail.com		Email: mjethanandani@gmail.com
	Greg Mirsky		Greg Mirsky
	Ericsson		Ericsson
	Email: gregory.mirsky@ericsson.com		Email: gregory.mirsky@ericsson.com
End of changes. 205 change blocks.
	901 lines changed or deleted		1580 lines changed or added
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