draft-ietf-bfd-unaffiliated-echo-03.txt		draft-ietf-bfd-unaffiliated-echo-04.txt
	BFD Working Group W. Cheng		BFD Working Group W. Cheng
	Internet-Draft R. Wang		Internet-Draft R. Wang
	Updates: 5880 (if approved) China Mobile		Updates: 5880 (if approved) China Mobile
	Intended status: Standards Track X. Min, Ed.		Intended status: Standards Track X. Min, Ed.
	Expires: 28 July 2022 ZTE Corp.		Expires: 12 August 2022 ZTE Corp.
	R. Rahman		R. Rahman
	Individual		Individual
	R. Boddireddy		R. Boddireddy
	Juniper Networks		Juniper Networks
	24 January 2022		8 February 2022
	Unaffiliated BFD Echo		Unaffiliated BFD Echo
	draft-ietf-bfd-unaffiliated-echo-03		draft-ietf-bfd-unaffiliated-echo-04
	Abstract		Abstract
	Bidirectional Forwarding Detection (BFD) is a fault detection		Bidirectional Forwarding Detection (BFD) is a fault detection
	protocol that can quickly determine a communication failure between		protocol that can quickly determine a communication failure between
	two forwarding engines. This document proposes a use of the BFD Echo		two forwarding engines. This document proposes a use of the BFD Echo
	where the local system supports BFD but the neighboring system does		where the local system supports BFD but the neighboring system does
	not support BFD.		not support BFD.
	This document updates RFC 5880.		This document updates RFC 5880.
	skipping to change at page 1, line 42 ¶		skipping to change at page 1, line 42 ¶
	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 28 July 2022.		This Internet-Draft will expire on 12 August 2022.
	Copyright Notice		Copyright Notice
	Copyright (c) 2022 IETF Trust and the persons identified as the		Copyright (c) 2022 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 (https://trustee.ietf.org/		Provisions Relating to IETF Documents (https://trustee.ietf.org/
	license-info) in effect on the date of publication of this document.		license-info) in effect on the date of publication of this document.
	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 22 ¶		skipping to change at page 2, line 22 ¶
	provided without warranty as described in the Revised BSD License.		provided without warranty as described in the Revised BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	1.1. Conventions Used in This Document . . . . . . . . . . . . 3		1.1. Conventions Used in This Document . . . . . . . . . . . . 3
	2. Updates to RFC 5880 . . . . . . . . . . . . . . . . . . . . . 3		2. Updates to RFC 5880 . . . . . . . . . . . . . . . . . . . . . 3
	3. Unaffiliated BFD Echo Procedures . . . . . . . . . . . . . . 6		3. Unaffiliated BFD Echo Procedures . . . . . . . . . . . . . . 6
	4. Unaffiliated BFD Echo Applicability . . . . . . . . . . . . . 8		4. Unaffiliated BFD Echo Applicability . . . . . . . . . . . . . 8
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 8		5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
	8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9		8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 9
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9		9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
	9.1. Normative References . . . . . . . . . . . . . . . . . . 9		9.1. Normative References . . . . . . . . . . . . . . . . . . 9
	9.2. Informative References . . . . . . . . . . . . . . . . . 9		9.2. Informative References . . . . . . . . . . . . . . . . . 9
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
	1. Introduction		1. Introduction
	To minimize the impact of device/link faults on services and improve		To minimize the impact of device/link faults on services and improve
	network availability, a network device must be able to quickly detect		network availability, a network device must be able to quickly detect
	skipping to change at page 3, line 43 ¶		skipping to change at page 3, line 43 ¶
	The Unaffiliated BFD Echo described in this document reuses the BFD		The Unaffiliated BFD Echo described in this document reuses the BFD
	Echo function as described in [RFC5880] and [RFC5881], but does not		Echo function as described in [RFC5880] and [RFC5881], but does not
	require BFD Asynchronous or Demand mode. When using the Unaffiliated		require BFD Asynchronous or Demand mode. When using the Unaffiliated
	BFD Echo, only the local system has the BFD protocol enabled; the		BFD Echo, only the local system has the BFD protocol enabled; the
	remote system just loops back the received BFD Echo packets as		remote system just loops back the received BFD Echo packets as
	regular data packets.		regular data packets.
	This document updates [RFC5880] with respect to its descriptions on		This document updates [RFC5880] with respect to its descriptions on
	the BFD Echo function as follows.		the BFD Echo function as follows.
	* The 4th paragraph of Section 3.2 of [RFC5880] is updated as below:		The 4th paragraph of Section 3.2 of [RFC5880] is updated as below:
	* OLD TEXT
	* An adjunct to both modes is the Echo function.
	* NEW TEXT		OLD TEXT
			An adjunct to both modes is the Echo function.
	* An adjunct to both modes is the Echo function, which can also be		NEW TEXT
			An adjunct to both modes is the Echo function, which can also be
	running independently.		running independently.
	* OLD TEXT		OLD TEXT
			Since the Echo function is handling the task of detection, the
	* Since the Echo function is handling the task of detection, the
	rate of periodic transmission of Control packets may be reduced		rate of periodic transmission of Control packets may be reduced
	(in the case of Asynchronous mode) or eliminated completely (in		(in the case of Asynchronous mode) or eliminated completely (in
	the case of Demand mode).		the case of Demand mode).
	* NEW TEXT		NEW TEXT
			Since the Echo function is handling the task of detection, the
	* Since the Echo function is handling the task of detection, the
	rate of periodic transmission of Control packets may be reduced		rate of periodic transmission of Control packets may be reduced
	(in the case of Asynchronous mode) or eliminated completely (in		(in the case of Asynchronous mode) or eliminated completely (in
	the case of Demand mode). The Echo function may also be used		the case of Demand mode). The Echo function may also be used
	independently, with neither Asynchronous nor Demand mode.		independently, with neither Asynchronous nor Demand mode.
	* The 3rd and 9th paragraphs of Section 6.1 of [RFC5880] are updated		The 3rd and 9th paragraphs of Section 6.1 of [RFC5880] are updated as
	as below:		below:
	* OLD TEXT
	* Once the BFD session is Up, a system can choose to start the Echo		OLD TEXT
			Once the BFD session is Up, a system can choose to start the Echo
	function if it desires and the other system signals that it will		function if it desires and the other system signals that it will
	allow it. The rate of transmission of Control packets is		allow it. The rate of transmission of Control packets is
	typically kept low when the Echo function is active.		typically kept low when the Echo function is active.
	* NEW TEXT		NEW TEXT
			When a system is running with Asynchronous or Demand mode, once
	* When a system is running with Asynchronous or Demand mode, once
	the BFD session is Up, it can choose to start the Echo function if		the BFD session is Up, it can choose to start the Echo function if
	it desires and the other system signals that it will allow it.		it desires and the other system signals that it will allow it.
	The rate of transmission of Control packets is typically kept low		The rate of transmission of Control packets is typically kept low
	for Asynchronous mode or eliminated completely for Demand mode		for Asynchronous mode or eliminated completely for Demand mode
	when the Echo function is active.		when the Echo function is active.
	* OLD TEXT		OLD TEXT
			If the session goes Down, the transmission of Echo packets (if
	* If the session goes Down, the transmission of Echo packets (if
	any) ceases, and the transmission of Control packets goes back to		any) ceases, and the transmission of Control packets goes back to
	the slow rate.		the slow rate.
	* NEW TEXT		NEW TEXT
			In Asynchronous mode, if the session goes Down, the transmission
	* In Asynchronous mode, if the session goes Down, the transmission
	of Echo packets (if any) ceases, and the transmission of Control		of Echo packets (if any) ceases, and the transmission of Control
	packets goes back to the slow rate. Demand mode MUST NOT be		packets goes back to the slow rate. Demand mode MUST NOT be
	active if the session goes Down.		active if the session goes Down.
	* The 2nd paragraph of Section 6.4 of [RFC5880] is updated as below:		The 2nd paragraph of Section 6.4 of [RFC5880] is updated as below:
	* OLD TEXT
	* When a system is using the Echo function, it is advantageous to		OLD TEXT
			When a system is using the Echo function, it is advantageous to
	choose a sedate reception rate for Control packets, since liveness		choose a sedate reception rate for Control packets, since liveness
	detection is being handled by the Echo packets. This can be		detection is being handled by the Echo packets. This can be
	controlled by manipulating the Required Min RX Interval field (see		controlled by manipulating the Required Min RX Interval field (see
	section 6.8.3).		section 6.8.3).
	* NEW TEXT		NEW TEXT
			When a system is using the Echo function with Asynchronous mode,
	* When a system is using the Echo function with Asynchronous mode,
	it is advantageous to choose a sedate reception rate for Control		it is advantageous to choose a sedate reception rate for Control
	packets, since liveness detection is being handled by the Echo		packets, since liveness detection is being handled by the Echo
	packets. This can be controlled by manipulating the Required Min		packets. This can be controlled by manipulating the Required Min
	RX Interval field (see section 6.8.3). Note that a system		RX Interval field (see section 6.8.3). Note that a system
	operating in Demand mode would direct the remote system to cease		operating in Demand mode would direct the remote system to cease
	the periodic transmission of BFD Control packets, by setting the		the periodic transmission of BFD Control packets, by setting the
	Demand (D) bit in its BFD Control packets.		Demand (D) bit in its BFD Control packets.
	* The 2nd paragraph of Section 6.8 of [RFC5880] is updated as below:		The 2nd paragraph of Section 6.8 of [RFC5880] is updated as below:
	* OLD TEXT
	* When a system is said to have "the Echo function active" it means		OLD TEXT
			When a system is said to have "the Echo function active" it means
	that the system is sending BFD Echo packets, implying that the		that the system is sending BFD Echo packets, implying that the
	session is Up and the other system has signaled its willingness to		session is Up and the other system has signaled its willingness to
	loop back Echo packets.		loop back Echo packets.
	* NEW TEXT		NEW TEXT
			When a system in Asynchronous or Demand mode is said to have "the
	* When a system in Asynchronous or Demand mode is said to have "the
	Echo function active" it means that the system is sending BFD Echo		Echo function active" it means that the system is sending BFD Echo
	packets, implying that the session is Up and the other system has		packets, implying that the session is Up and the other system has
	signaled its willingness to loop back Echo packets.		signaled its willingness to loop back Echo packets.
	* The 7th paragraph of Section 6.8.3 of [RFC5880] is updated as		The 7th paragraph of Section 6.8.3 of [RFC5880] is updated as below:
	below:
	* OLD TEXT
	* When the Echo function is active, a system SHOULD set		OLD TEXT
			When the Echo function is active, a system SHOULD set
	bfd.RequiredMinRxInterval to a value of not less than one second		bfd.RequiredMinRxInterval to a value of not less than one second
	(1,000,000 microseconds). This is intended to keep received BFD		(1,000,000 microseconds). This is intended to keep received BFD
	Control traffic at a negligible level, since the actual detection		Control traffic at a negligible level, since the actual detection
	function is being performed using BFD Echo packets.		function is being performed using BFD Echo packets.
	* NEW TEXT		NEW TEXT
	* When the Echo function is active with Asynchronous mode, a system		When the Echo function is active with Asynchronous mode, a system
	SHOULD set bfd.RequiredMinRxInterval to a value of not less than		SHOULD set bfd.RequiredMinRxInterval to a value of not less than
	one second (1,000,000 microseconds). This is intended to keep		one second (1,000,000 microseconds). This is intended to keep
	received BFD Control traffic at a negligible level, since the		received BFD Control traffic at a negligible level, since the
	actual detection function is being performed using BFD Echo		actual detection function is being performed using BFD Echo
	packets. While a system operating in Demand mode would not		packets. While a system operating in Demand mode would not
	receive BFD Control traffic.		receive BFD Control traffic.
	* The 1st and 2nd paragraphs of Section 6.8.9 of [RFC5880] are		The 1st and 2nd paragraphs of Section 6.8.9 of [RFC5880] are updated
	updated as below:		as below:
	* OLD TEXT
	* BFD Echo packets MUST NOT be transmitted when bfd.SessionState is		OLD TEXT
			BFD Echo packets MUST NOT be transmitted when bfd.SessionState is
	not Up. BFD Echo packets MUST NOT be transmitted unless the last		not Up. BFD Echo packets MUST NOT be transmitted unless the last
	BFD Control packet received from the remote system contains a		BFD Control packet received from the remote system contains a
	nonzero value in Required Min Echo RX Interval.		nonzero value in Required Min Echo RX Interval.
	* NEW TEXT		NEW TEXT
			When a system is using the Echo function with either Asynchronous
	* When a system is using the Echo function with either Asynchronous
	or Demand mode, BFD Echo packets MUST NOT be transmitted when		or Demand mode, BFD Echo packets MUST NOT be transmitted when
	bfd.SessionState is not Up, and BFD Echo packets MUST NOT be		bfd.SessionState is not Up, and BFD Echo packets MUST NOT be
	transmitted unless the last BFD Control packet received from the		transmitted unless the last BFD Control packet received from the
	remote system contains a nonzero value in Required Min Echo RX		remote system contains a nonzero value in Required Min Echo RX
	Interval.		Interval.
	* OLD TEXT		OLD TEXT
			BFD Echo packets MAY be transmitted when bfd.SessionState is Up.
	* BFD Echo packets MAY be transmitted when bfd.SessionState is Up.
	The interval between transmitted BFD Echo packets MUST NOT be less		The interval between transmitted BFD Echo packets MUST NOT be less
	than the value advertised by the remote system in Required Min		than the value advertised by the remote system in Required Min
	Echo RX Interval...		Echo RX Interval...
	* NEW TEXT		NEW TEXT
			When a system is using the Echo function with either Asynchronous
	* When a system is using the Echo function with either Asynchronous
	or Demand mode, BFD Echo packets MAY be transmitted when		or Demand mode, BFD Echo packets MAY be transmitted when
	bfd.SessionState is Up, and the interval between transmitted BFD		bfd.SessionState is Up, and the interval between transmitted BFD
	Echo packets MUST NOT be less than the value advertised by the		Echo packets MUST NOT be less than the value advertised by the
	remote system in Required Min Echo RX Interval...		remote system in Required Min Echo RX Interval...
	3. Unaffiliated BFD Echo Procedures		3. Unaffiliated BFD Echo Procedures
	Device A Device B		Device A Device B
	BFD Enabled BFD Echo packets loopback		BFD Enabled BFD Echo packets loopback
	+--------+ BFD Echo session +--------+		+--------+ BFD Echo session +--------+
	| A |--------------------------------| B |		| A |--------------------------------| B |
	| |Interface 1 Interface 1| |		| |Interface 1 Interface 1| |
	+--------+ +--------+		+--------+ +--------+
	BFD is supported. BFD is not supported.		BFD is supported. BFD is not supported.
	Figure 1: Unaffiliated BFD Echo diagram		Figure 1: Unaffiliated BFD Echo diagram
	skipping to change at page 9, line 23 ¶		skipping to change at page 9, line 7 ¶
	The authors would like to acknowledge Ketan Talaulikar, Greg Mirsky		The authors would like to acknowledge Ketan Talaulikar, Greg Mirsky
	and Santosh Pallagatti for their careful review and very helpful		and Santosh Pallagatti for their careful review and very helpful
	comments.		comments.
	The authors would like to acknowledge Jeff Haas for his insightful		The authors would like to acknowledge Jeff Haas for his insightful
	review and very helpful comments.		review and very helpful comments.
	8. Contributors		8. Contributors
	Liu Aihua ZTE Email: liu.aihua@zte.com.cn		Liu Aihua
			ZTE
			Email: liu.aihua@zte.com.cn
	Qian Xin ZTE Email: qian.xin2@zte.com.cn		Qian Xin
			ZTE
			Email: qian.xin2@zte.com.cn
	Zhao Yanhua ZTE Email: zhao.yanhua3@zte.com.cn		Zhao Yanhua
			ZTE
			Email: zhao.yanhua3@zte.com.cn
	9. References		9. References
	9.1. Normative References		9.1. 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,
	<https://www.rfc-editor.org/info/rfc2119>.		<https://www.rfc-editor.org/info/rfc2119>.
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