< draft-ietf-bfd-unsolicited-02.txt		draft-ietf-bfd-unsolicited-03.txt >
	Network Working Group E. Chen		Network Working Group E. Chen
	Internet-Draft Cisco Systems		Internet-Draft Palo Alto Networks
	Intended status: Standards Track N. Shen		Intended status: Standards Track N. Shen
	Expires: January 29, 2021 Zededa		Expires: October 24, 2021 Zededa
	R. Raszuk		R. Raszuk
	Bloomberg LP		NTT Network Innovations
	R. Rahman		R. Rahman
	Cisco Systems		April 22, 2021
	July 28, 2020
	Unsolicited BFD for Sessionless Applications		Unsolicited BFD for Sessionless Applications
	draft-ietf-bfd-unsolicited-02		draft-ietf-bfd-unsolicited-03
	Abstract		Abstract
	For operational simplification of "sessionless" applications using		For operational simplification of "sessionless" applications using
	BFD, in this document we present procedures for "unsolicited BFD"		BFD, in this document we present procedures for "unsolicited BFD"
	that allow a BFD session to be initiated by only one side, and be		that allow a BFD session to be initiated by only one side, and be
	established without explicit per-session configuration or		established without explicit per-session configuration or
	registration by the other side (subject to certain per-interface or		registration by the other side (subject to certain per-interface or
	per-router policies).		per-router policies).
	skipping to change at page 1, line 48 ¶		skipping to change at page 1, line 47 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on January 29, 2021.		This Internet-Draft will expire on October 24, 2021.
	Copyright Notice		Copyright Notice
	Copyright (c) 2020 IETF Trust and the persons identified as the		Copyright (c) 2021 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(https://trustee.ietf.org/license-info) in effect on the date of		(https://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Procedures for Unsolicited BFD . . . . . . . . . . . . . . . 3		2. Procedures for Unsolicited BFD . . . . . . . . . . . . . . . 3
	3. YANG Data Model . . . . . . . . . . . . . . . . . . . . . . . 4		3. YANG Data Model . . . . . . . . . . . . . . . . . . . . . . . 4
	3.1. Unsolicited BFD Hierarchy . . . . . . . . . . . . . . . . 4		3.1. Unsolicited BFD Hierarchy . . . . . . . . . . . . . . . . 4
	3.2. Unsolicited BFD Module . . . . . . . . . . . . . . . . . 5		3.2. Unsolicited BFD Module . . . . . . . . . . . . . . . . . 5
	4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 9		5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
	5.1. BFD Protocol Security Considerations . . . . . . . . . . 9		6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
	5.2. YANG Module Security Considerations . . . . . . . . . . . 9		6.1. BFD Protocol Security Considerations . . . . . . . . . . 9
	6. References . . . . . . . . . . . . . . . . . . . . . . . . . 10		6.2. YANG Module Security Considerations . . . . . . . . . . . 9
	6.1. Normative References . . . . . . . . . . . . . . . . . . 10		7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10
	6.2. Informative References . . . . . . . . . . . . . . . . . 11		7.1. Normative References . . . . . . . . . . . . . . . . . . 10
			7.2. Informative References . . . . . . . . . . . . . . . . . 12
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	The current implementation and deployment practice for BFD ([RFC5880]		The current implementation and deployment practice for BFD ([RFC5880]
	and [RFC5881]) usually requires BFD sessions be explicitly configured		and [RFC5881]) usually requires BFD sessions be explicitly configured
	or registered on both sides. This requirement is not an issue when		or registered on both sides. This requirement is not an issue when
	an application like BGP [RFC4271] has the concept of a "session" that		an application like BGP [RFC4271] has the concept of a "session" that
	involves both sides for its establishment. However, this requirement		involves both sides for its establishment. However, this requirement
	can be operationally challenging when the prerequisite "session" does		can be operationally challenging when the prerequisite "session" does
	skipping to change at page 3, line 48 ¶		skipping to change at page 3, line 49 ¶
	Server, multiple BGP paths (when exist) can be made available to the		Server, multiple BGP paths (when exist) can be made available to the
	clients of the Router Server as described in [RFC7947]. The		clients of the Router Server as described in [RFC7947]. The
	"unsolicited BFD" can be used in BGP route selection by these clients		"unsolicited BFD" can be used in BGP route selection by these clients
	to eliminate paths with "inaccessible nexthops".		to eliminate paths with "inaccessible nexthops".
	2. Procedures for Unsolicited BFD		2. Procedures for Unsolicited BFD
	With "unsolicited BFD", one side takes the "Active role" and the		With "unsolicited BFD", one side takes the "Active role" and the
	other side takes only the "Passive role" as described in [RFC5880].		other side takes only the "Passive role" as described in [RFC5880].
	On the passive side, the "unsolicited BFD" SHOULD be configured		On the passive side, the "unsolicited BFD" SHOULD be explicitely
	explicitly on an interface. The BFD parameters can be either per-		configured on an interface or globally (apply to all interfaces).
	interface or per-router based. It MAY also choose to use the		The BFD parameters can be either per-interface or per-router based.
	parameters that the active side uses in its BFD Control packets. The
	"Discriminator", however, MUST be chosen to allow multiple
	unsolicited BFD sessions.
	The active side initiates the BFD Control packets as specified in		It MAY also choose to use the parameters that the active side uses in
	[RFC5880]. The passive side does not initiates the BFD Control		its BFD Control packets. The "My Discriminator", however, MUST be
	packets.		chosen to allow multiple unsolicited BFD sessions.
			The active side starts sending the BFD Control packets as specified
			in [RFC5880]. The passive side does not send BFD Control packets.
	When the passive side receives a BFD Control packet from the active		When the passive side receives a BFD Control packet from the active
	side with 0 as the "remote-discriminator", and it does not find an		side with 0 as "Your Discriminator", and it does not find an existing
	existing session with the same source address as in the packet and		session with the same source address and the same "Discriminator"
	"unsolicited BFD" is allowed on the interface by local policy, it		pairs as in the packet and "unsolicited BFD" is allowed on the
	SHOULD then create a matching BFD session toward the active side		interface by local policy, it SHOULD then create a matching BFD
	(based on the source address and destination address in the BFD		session toward the active side (based on the source address and
	Control packet) as if the session were locally registered. It would		destination address in the BFD Control packet) as if the session were
	then start sending the BFD Control packets and perform necessary		locally registered. It would then start sending the BFD Control
	procedure for bringing up, maintaining and tearing down the BFD		packets and perform necessary procedure for bringing up, maintaining
	session. If the BFD session fails to get established within certain		and tearing down the BFD session. If the BFD session fails to get
	specified time, or if an established BFD session goes down, the		established within certain specified time, or if an established BFD
	passive side would stop sending BFD Control packets and delete the		session goes down, the passive side would stop sending BFD Control
	BFD session created until the BFD Control packets is initiated by the		packets and delete the BFD session created until the BFD Control
	active side again.		packets is initiated by the active side again.
	The "Passive role" may change to the "Active role" when a local		The "Passive role" may change to the "Active role" when a local
	client registers for the same BFD session, and from the "Active role		client registers for the same BFD session, and from the "Active role
	" to the "Passive role " when there is no longer any locally		" to the "Passive role " when there is no longer any locally
	registered client for the BFD session.		registered client for the BFD session.
	3. YANG Data Model		3. YANG Data Model
	This section extends the YANG data model for BFD [I-D.ietf-bfd-yang]		This section extends the YANG data model for BFD [I-D.ietf-bfd-yang]
	to cover the unsolicited BFD.		to cover the unsolicited BFD.
	skipping to change at page 6, line 30 ¶		skipping to change at page 6, line 30 ¶
	"RFC 8349: A YANG Data Model for Routing Management		"RFC 8349: A YANG Data Model for Routing Management
	(NMDA version)";		(NMDA version)";
	}		}
	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>
	Editors: Enke Chen (enkechen@cisco.com),		Editors: Enke Chen (enchen@paloaltonetworks.com),
	Naiming Shen (naiming@cisco.com),		Naiming Shen (naiming@zededa.com),
	Robert Raszuk (robert@raszuk.net),		Robert Raszuk (robert@raszuk.net),
	Reshad Rahman (rrahman@cisco.com)";		Reshad Rahman (reshad@yahoo.com)";
	description		description
	"This module contains the YANG definition for BFD unsolicited		"This module contains the YANG definition for BFD unsolicited
	as per RFC YYYY.		as per RFC YYYY.
	Copyright (c) 2018 IETF Trust and the persons		Copyright (c) 2018 IETF Trust and the persons
	identified as authors of the code. All rights reserved.		identified as authors of the code. All rights reserved.
	Redistribution and use in source and binary forms, with or		Redistribution and use in source and binary forms, with or
	without modification, is permitted pursuant to, and subject		without modification, is permitted pursuant to, and subject
	skipping to change at page 9, line 9 ¶		skipping to change at page 9, line 9 ¶
	}		}
	}		}
	}		}
	<CODE ENDS>		<CODE ENDS>
	4. IANA Considerations		4. IANA Considerations
	This documents makes no IANA requests.		This documents makes no IANA requests.
	5. Security Considerations		5. Acknowledgments
	5.1. BFD Protocol Security Considerations		Authors would like to thank Acee Lindem, Greg Mirsky and Raj Chetan
			for their review and valuable input.
			6. Security Considerations
			6.1. BFD Protocol Security Considerations
	The same security considerations as those described in [RFC5880] and		The same security considerations as those described in [RFC5880] and
	[RFC5881] apply to this document. With "unsolicited BFD" there is		[RFC5881] apply to this document. With "unsolicited BFD" there is
	potential risk for excessive resource usage by BFD from "unexpected"		potential risk for excessive resource usage by BFD from "unexpected"
	remote systems. To mitigate such risks, the following measures are		remote systems. To mitigate such risks, the following measures are
	RECOMMENDED:		RECOMMENDED:
	o Limit the feature to specific interfaces, and to a single-hop BFD		o Limit the feature to specific interfaces, and to a single-hop BFD
	with "TTL=255" [RFC5082]. In addition make sure the source		with "TTL=255" [RFC5082]. For numbered interfaces source address
	address of an incoming BFD packet belongs to the subnet of the		of an incoming BFD packet should belongs to the subnet of the
	interface from which the BFD packet is received.		interface from which the BFD packet is received. For unnumbered
			interfaces the above check should be alinged with routing protocol
			addresses running on such pair of interfaces.
	o Apply "access control" to allow BFD packets only from certain		o Apply "access control" to allow BFD packets only from certain
	subnets or hosts.		subnets or hosts.
	o Deploy the feature only in certain "trustworthy" environment,		o Deploy the feature only in certain "trustworthy" environment,
	e.g., at an IXP, or between a provider and its customers.		e.g., at an IXP, or between a provider and its customers.
	o Adjust BFD parameters as needed for the particular deployment and		o Adjust BFD parameters as needed for the particular deployment and
	scale.		scale.
	o Use BFD authentication.		o Use BFD authentication.
	5.2. YANG Module Security Considerations		6.2. YANG Module Security Considerations
	The YANG module specified in this document defines a schema for data		The YANG module specified in this document defines a schema for data
	that is designed to be accessed via network management protocols such		that is designed to be accessed via network management protocols such
	as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer		as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer
	is the secure transport layer, and the mandatory-to-implement secure		is the secure transport layer, and the mandatory-to-implement secure
	transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer		transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer
	is HTTPS, and the mandatory-to-implement secure transport is TLS		is HTTPS, and the mandatory-to-implement secure transport is TLS
	[RFC5246].		[RFC5246].
	The NETCONF access control model [RFC6536] provides the means to		The NETCONF access control model [RFC6536] provides the means to
	skipping to change at page 10, line 9 ¶		skipping to change at page 10, line 17 ¶
	default). These data nodes may be considered sensitive or vulnerable		default). These data nodes may be considered sensitive or vulnerable
	in some network environments. Write operations (e.g., edit-config)		in some network environments. Write operations (e.g., edit-config)
	to these data nodes without proper protection can have a negative		to these data nodes without proper protection can have a negative
	effect on network operations. These are the subtrees and data nodes		effect on network operations. These are the subtrees and data nodes
	and their sensitivity/vulnerability:		and their sensitivity/vulnerability:
	/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh		/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
	/unsolicited:		/unsolicited:
	o data node "enable" enables creation of unsolicited BFD IP single-		o data node "enable" enables creation of unsolicited BFD IP single-
	hop sessions globally, i.e. on all interfaces. See Section 5.1.		hop sessions globally, i.e. on all interfaces. See Section 6.1.
	o data nodes local-multiplier, desired-min-tx-interval, required-		o data nodes local-multiplier, desired-min-tx-interval, required-
	min-rx-interval and min-interval all impact the parameters of the		min-rx-interval and min-interval all impact the parameters of the
	unsolicited BFD IP single-hop sessions.		unsolicited BFD IP single-hop sessions.
	/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh		/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
	/interfaces/interface/unsolicited:		/interfaces/interface/unsolicited:
	o data node "enable" enables creation of unsolicited BFD IP single-		o data node "enable" enables creation of unsolicited BFD IP single-
	hop sessions on a specific interface. See Section 5.1.		hop sessions on a specific interface. See Section 6.1.
	o data nodes local-multiplier, desired-min-tx-interval, required-		o data nodes local-multiplier, desired-min-tx-interval, required-
	min-rx-interval and min-interval all impact the parameters of the		min-rx-interval and min-interval all impact the parameters of the
	unsolicited BFD IP single-hop sessions on the interface.		unsolicited BFD IP single-hop sessions on the interface.
	Some of the readable data nodes in this YANG module may be considered		Some of the readable data nodes in this YANG module may be considered
	sensitive or vulnerable in some network environments. It is thus		sensitive or vulnerable in some network environments. It is thus
	important to control read access (e.g., via get, get-config, or		important to control read access (e.g., via get, get-config, or
	notification) to these data nodes. These are the subtrees and data		notification) to these data nodes. These are the subtrees and data
	nodes and their sensitivity/vulnerability:		nodes and their sensitivity/vulnerability:
	/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh		/routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh
	/sessions/session/unsolicited: access to this information discloses		/sessions/session/unsolicited: access to this information discloses
	the role of the local system in the creation of the unsolicited BFD		the role of the local system in the creation of the unsolicited BFD
	session.		session.
	6. References		7. References
	6.1. Normative References		7.1. Normative References
	[I-D.ietf-bfd-yang]		[I-D.ietf-bfd-yang]
	Rahman, R., Zheng, L., Jethanandani, M., Pallagatti, S.,		Rahman, R., Zheng, L., Jethanandani, M., Pallagatti, S.,
	and G. Mirsky, "YANG Data Model for Bidirectional		and G. Mirsky, "YANG Data Model for Bidirectional
	Forwarding Detection (BFD)", draft-ietf-bfd-yang-17 (work		Forwarding Detection (BFD)", draft-ietf-bfd-yang-17 (work
	in progress), August 2018.		in progress), August 2018.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", BCP 14, RFC 2119,		Requirement Levels", BCP 14, RFC 2119,
	DOI 10.17487/RFC2119, March 1997,		DOI 10.17487/RFC2119, March 1997,
	skipping to change at page 11, line 41 ¶		skipping to change at page 12, line 5 ¶
	<https://www.rfc-editor.org/info/rfc6536>.		<https://www.rfc-editor.org/info/rfc6536>.
	[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF		[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
	Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,		Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
	<https://www.rfc-editor.org/info/rfc8040>.		<https://www.rfc-editor.org/info/rfc8040>.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,		2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
	May 2017, <https://www.rfc-editor.org/info/rfc8174>.		May 2017, <https://www.rfc-editor.org/info/rfc8174>.
	6.2. Informative References		7.2. Informative References
	[I-D.ietf-idr-rs-bfd]		[I-D.ietf-idr-rs-bfd]
	Bush, R., Haas, J., Scudder, J., Nipper, A., and C.		Bush, R., Haas, J., Scudder, J., Nipper, A., and C.
	Dietzel, "Making Route Servers Aware of Data Link Failures		Dietzel, "Making Route Servers Aware of Data Link Failures
	at IXPs", draft-ietf-idr-rs-bfd-08 (work in progress),		at IXPs", draft-ietf-idr-rs-bfd-09 (work in progress),
	September 2019.		September 2020.
	[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A		[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
	Border Gateway Protocol 4 (BGP-4)", RFC 4271,		Border Gateway Protocol 4 (BGP-4)", RFC 4271,
	DOI 10.17487/RFC4271, January 2006,		DOI 10.17487/RFC4271, January 2006,
	<https://www.rfc-editor.org/info/rfc4271>.		<https://www.rfc-editor.org/info/rfc4271>.
	[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.		[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
	Pallagatti, "Seamless Bidirectional Forwarding Detection		Pallagatti, "Seamless Bidirectional Forwarding Detection
	(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,		(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
	<https://www.rfc-editor.org/info/rfc7880>.		<https://www.rfc-editor.org/info/rfc7880>.
	skipping to change at page 12, line 23 ¶		skipping to change at page 12, line 36 ¶
	<https://www.rfc-editor.org/info/rfc7911>.		<https://www.rfc-editor.org/info/rfc7911>.
	[RFC7947] Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,		[RFC7947] Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
	"Internet Exchange BGP Route Server", RFC 7947,		"Internet Exchange BGP Route Server", RFC 7947,
	DOI 10.17487/RFC7947, September 2016,		DOI 10.17487/RFC7947, September 2016,
	<https://www.rfc-editor.org/info/rfc7947>.		<https://www.rfc-editor.org/info/rfc7947>.
	Authors' Addresses		Authors' Addresses
	Enke Chen		Enke Chen
	Cisco Systems		Palo Alto Networks
	560 McCarthy Blvd.
	Milpitas, CA 95035
	USA
	Email: enkechen@cisco.com		Email: enchen@paloaltonetworks.com
	Naiming Shen		Naiming Shen
	Zededa		Zededa
	Email: naiming@zededa.com		Email: naiming@zededa.com
	Robert Raszuk		Robert Raszuk
	Bloomberg LP		NTT Network Innovations
	731 Lexington Ave		940 Stewart Dr
	New York City, NY 10022		Sunnyvale, CA 94085
	USA		USA
	Email: robert@raszuk.net		Email: robert@raszuk.net
	Reshad Rahman		Reshad Rahman
	Cisco Systems
	2000 Innovation Drive
	Kanata, Ontario K2K 3E8
	Canada
	Email: rrahman@cisco.com		Email: reshad@yahoo.com
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