< draft-gandhi-spring-twamp-srpm-00.txt		draft-gandhi-spring-twamp-srpm-01.txt >
	SPRING Working Group R. Gandhi, Ed.		SPRING Working Group R. Gandhi, Ed.
	Internet-Draft C. Filsfils		Internet-Draft C. Filsfils
	Intended Status: Standards Track Cisco Systems, Inc.		Intended Status: Standards Track Cisco Systems, Inc.
	Expires: August 13, 2019 D. Voyer		Expires: November 16, 2019 D. Voyer
	Bell Canada		Bell Canada
	February 9, 2019		M. Chen
			Huawei
			May 15, 2019
	In-band Performance Measurement Using TWAMP		Performance Measurement Using TWAMP
	for Segment Routing Networks		for Segment Routing Networks
	draft-gandhi-spring-twamp-srpm-00		draft-gandhi-spring-twamp-srpm-01
	Abstract		Abstract
	Segment Routing (SR) is applicable to both Multiprotocol Label		Segment Routing (SR) is applicable to both Multiprotocol Label
	Switching (SR-MPLS) and IPv6 (SRv6) data planes. This document		Switching (SR-MPLS) and IPv6 (SRv6) data planes. This document
	specifies procedures for sending and processing in-band probe query		specifies procedures for sending and processing synthetic probe query
	and response messages for Performance Measurement. The procedure		and response messages for Performance Measurement (PM). The
	uses the mechanisms defined in RFC 5357 (Two-Way Active Measurement		procedure uses the mechanisms defined in RFC 5357 (Two-Way Active
	Protocol (TWAMP)) for Delay Measurement, and also uses the mechanisms		Measurement Protocol (TWAMP)) for Delay Measurement, and also uses
	for direct-mode loss measurement defined in this document. The		the mechanisms specified in this document for direct-mode Loss
	procedure specified is applicable to SR-MPLS and SRv6 data planes for		Measurement. The procedure specified is applicable to SR-MPLS and
	both links and end-to-end measurement for SR Policies.		SRv6 data planes for both links and end-to-end measurement for SR
			Policies.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	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/.
	skipping to change at page 2, line 14 ¶		skipping to change at page 2, line 17 ¶
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	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 . . . . . . . . . . . . . . . . . . . . . . . . . 3
	2. Conventions Used in This Document . . . . . . . . . . . . . . 3		2. Conventions Used in This Document . . . . . . . . . . . . . . 3
	2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3		2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
	2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3		2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4
	2.3. Reference Topology . . . . . . . . . . . . . . . . . . . . 4		2.3. Reference Topology . . . . . . . . . . . . . . . . . . . . 4
	2.4. In-band Probe Messages . . . . . . . . . . . . . . . . . . 5
	3. Probe Messages . . . . . . . . . . . . . . . . . . . . . . . . 5		3. Probe Messages . . . . . . . . . . . . . . . . . . . . . . . . 5
	3.1. Probe Query Message . . . . . . . . . . . . . . . . . . . 5		3.1. Probe Query Message . . . . . . . . . . . . . . . . . . . 5
	3.1.1. Delay Measurement Probe Query Message . . . . . . . . 5		3.1.1. Delay Measurement Probe Query Message . . . . . . . . 6
	3.1.2. Loss Measurement Probe Query Message . . . . . . . . . 6		3.1.1.1. Delay Measurement Message Checksum Complement . . 6
			3.1.1.2. Delay Measurement Authentication Mode . . . . . . 7
			3.1.2. Loss Measurement Probe Query Message . . . . . . . . . 7
			3.1.2.1. Loss Measurement Message Checksum Complement . . . 10
			3.1.2.2. Loss Measurement Authentication Mode . . . . . . . 10
	3.1.3. Probe Query for SR Links . . . . . . . . . . . . . . . 10		3.1.3. Probe Query for SR Links . . . . . . . . . . . . . . . 10
	3.1.4. Probe Query for End-to-end Measurement for SR Policy . 11		3.1.4. Probe Query for End-to-end Measurement for SR Policy . 10
	3.1.4.1. Probe Query Message for SR-MPLS Policy . . . . . . 11		3.1.4.1. Probe Query Message for SR-MPLS Policy . . . . . . 10
	3.1.4.2. Probe Query Message for SRv6 Policy . . . . . . . 11		3.1.4.2. Probe Query Message for SRv6 Policy . . . . . . . 11
	3.2. Probe Response Message . . . . . . . . . . . . . . . . . . 12		3.2. Probe Response Message . . . . . . . . . . . . . . . . . . 12
	3.2.1. One-way Measurement . . . . . . . . . . . . . . . . . 12		3.2.1. One-way Measurement Mode . . . . . . . . . . . . . . . 14
	3.2.2. Two-way Measurement . . . . . . . . . . . . . . . . . 12		3.2.2. Two-way Measurement Mode . . . . . . . . . . . . . . . 15
	3.2.2.1. Probe Response Message for SR-MPLS Policy . . . . 13		3.2.2.1. Return Path TLV . . . . . . . . . . . . . . . . . 15
	3.2.2.2. Probe Response Message for SRv6 Policy . . . . . . 13		3.2.2.2. Probe Response Message for SR-MPLS Policy . . . . 16
	4. Packet Loss Calculation . . . . . . . . . . . . . . . . . . . 13		3.2.2.3. Probe Response Message for SRv6 Policy . . . . . . 17
	5. Performance Measurement for P2MP SR Policies . . . . . . . . . 14		3.2.3. Loopback Measurement Mode . . . . . . . . . . . . . . 17
	6. ECMP Support . . . . . . . . . . . . . . . . . . . . . . . . . 14		4. Packet Loss Calculation . . . . . . . . . . . . . . . . . . . 17
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 14		5. Performance Measurement for P2MP SR Policies . . . . . . . . . 18
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15		6. ECMP Support for SR Policies . . . . . . . . . . . . . . . . . 18
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15		7. Security Considerations . . . . . . . . . . . . . . . . . . . 19
	9.1. Normative References . . . . . . . . . . . . . . . . . . . 15		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
	9.2. Informative References . . . . . . . . . . . . . . . . . . 15		9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
	Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 18		9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18		9.2. Informative References . . . . . . . . . . . . . . . . . . 20
			Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 22
			Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
	1. Introduction		1. Introduction
	Segment Routing (SR) technology greatly simplifies network operations		Segment Routing (SR) technology greatly simplifies network operations
	for Software Defined Networks (SDNs). SR is applicable to both		for Software Defined Networks (SDNs). SR is applicable to both
	Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) data planes.		Multiprotocol Label Switching (SR-MPLS) and IPv6 (SRv6) data planes.
	SR takes advantage of the Equal-Cost Multipaths (ECMPs) between		SR takes advantage of the Equal-Cost Multipaths (ECMPs) between
	source, transit and destination nodes. SR Policies as defined in		source, transit and destination nodes. SR Policies as defined in
	[I-D.spring-segment-routing-policy] are used to steer traffic through		[I-D.spring-segment-routing-policy] are used to steer traffic through
	a specific, user-defined path using a stack of Segments. Built-in SR		a specific, user-defined path using a stack of Segments. Built-in SR
	Performance Measurement (PM) is one of the essential requirements to		Performance Measurement (PM) is one of the essential requirements to
	provide Service Level Agreements (SLAs).		provide Service Level Agreements (SLAs).
	The One-Way Active Measurement Protocol (OWAMP) defined in [RFC4656]		The One-Way Active Measurement Protocol (OWAMP) defined in [RFC4656]
	and Two-Way Active Measurement Protocol (TWAMP) defined in [RFC5357]		and Two-Way Active Measurement Protocol (TWAMP) defined in [RFC5357]
	provide capabilities for the measurement of various performance		provide capabilities for the measurement of various performance
	skipping to change at page 3, line 15 ¶		skipping to change at page 3, line 20 ¶
	SR takes advantage of the Equal-Cost Multipaths (ECMPs) between		SR takes advantage of the Equal-Cost Multipaths (ECMPs) between
	source, transit and destination nodes. SR Policies as defined in		source, transit and destination nodes. SR Policies as defined in
	[I-D.spring-segment-routing-policy] are used to steer traffic through		[I-D.spring-segment-routing-policy] are used to steer traffic through
	a specific, user-defined path using a stack of Segments. Built-in SR		a specific, user-defined path using a stack of Segments. Built-in SR
	Performance Measurement (PM) is one of the essential requirements to		Performance Measurement (PM) is one of the essential requirements to
	provide Service Level Agreements (SLAs).		provide Service Level Agreements (SLAs).
	The One-Way Active Measurement Protocol (OWAMP) defined in [RFC4656]		The One-Way Active Measurement Protocol (OWAMP) defined in [RFC4656]
	and Two-Way Active Measurement Protocol (TWAMP) defined in [RFC5357]		and Two-Way Active Measurement Protocol (TWAMP) defined in [RFC5357]
	provide capabilities for the measurement of various performance		provide capabilities for the measurement of various performance
	metrics in IP networks. These protocols rely on control channel		metrics in IP networks using synthetic probe messages. These
	signaling to establish a test channel over an UDP path. These		protocols rely on control channel signaling to establish a test
	protocols lack support for direct-mode Loss Measurement (LM) to		channel over an UDP path. These protocols lack support for
	detect actual data traffic loss which is required in SR networks.		direct-mode Loss Measurement (LM) to detect actual data traffic loss
	The Simple Two-way Active Measurement Protocol (STAMP)		which is required in SR networks. The Simple Two-way Active
	[I-D.ippm-stamp] alleviates the control channel signaling by using		Measurement Protocol (STAMP) [I-D.ippm-stamp] alleviates the control
	configuration data model to provision test channels and required UDP		channel signaling by using configuration data model to provision test
	ports. The TWAMP Light from broadband forum [BBF.TR-390] provides		channels and UDP ports. The TWAMP Light from broadband forum
	simplified mechanisms for active performance measurement in Customer		[BBF.TR-390] provides simplified mechanisms for active performance
	Edge IP networks.		measurement in Customer Edge IP networks.
	This document specifies procedures for sending and processing in-band		This document specifies procedures for sending and processing
	probe query and response messages for Performance Measurement. The		synthetic probe query and response messages for Performance
	procedure uses the mechanisms defined in RFC 5357 (Two-Way Active		Measurement. The procedure uses the mechanisms defined in RFC 5357
	Measurement Protocol (TWAMP)) for Delay Measurement, and also uses		(Two-Way Active Measurement Protocol (TWAMP)) for Delay Measurement
	the mechanisms for direct-mode loss measurement defined in this		(DM), and also uses the mechanisms specified in this document for
	document. The procedure specified is applicable to SR-MPLS and SRv6		direct-mode Loss Measurement (LM). The procedure specified is
	data planes for both links and end-to-end measurement for SR		applicable to SR-MPLS and SRv6 data planes for both links and
	Policies. For SR Policies, there are ECMPs between the source and		end-to-end measurement for SR Policies. For SR Policies, there are
	transit nodes, between transit nodes and between transit and		Equal Cost Multi-Paths (ECMP) between the source and transit nodes,
	destination nodes. This document also defines mechanisms for		between transit nodes and between transit and destination nodes.
	handling ECMPs of SR Policies for performance delay measurement.		This document also defines mechanisms for handling ECMPs of SR
			Policies for performance delay measurement.
	2. Conventions Used in This Document		2. Conventions Used in This Document
	2.1. Requirements Language		2.1. 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
	document are to be interpreted as described in [RFC2119] [RFC8174]		document are to be interpreted as described in [RFC2119] [RFC8174]
	when, and only when, they appear in all capitals, as shown here.		when, and only when, they appear in all capitals, as shown here.
	skipping to change at page 5, line 13 ¶		skipping to change at page 5, line 16 ¶
	leaf nodes [I-D.spring-sr-p2mp-policy].		leaf nodes [I-D.spring-sr-p2mp-policy].
	+-------+ Query +-------+		+-------+ Query +-------+
	| | - - - - - - - - - ->| |		| | - - - - - - - - - ->| |
	| R1 |---------------------| R5 |		| R1 |---------------------| R5 |
	| |<- - - - - - - - - - | |		| |<- - - - - - - - - - | |
	+-------+ Response +-------+		+-------+ Response +-------+
	Reference Topology		Reference Topology
	Both Delay and Loss performance measurement is performed in-band for		For delay and loss measurements, for both links and end-to-end SR
	the traffic traversing between node R1 and node R5. One-way delay		Policies, no PM session is created on the responder node R5. One-way
	and two-way delay measurements are defined in [RFC4656] and		delay and two-way delay measurements are defined in [RFC4656] and
	[RFC5357], respectively. One-way loss measurement provides receive		[RFC5357], respectively. One-way loss measurement provides receive
	packet loss whereas two-way loss measurement provides both transmit		packet loss whereas two-way loss measurement provides both transmit
	and receive packet loss.		and receive packet loss.
	2.4. In-band Probe Messages		For Performance Measurement, synthetic probe query and response
			messages are used as following:
	For both Delay and Loss measurements for links and SR Policies, no PM		o For Delay Measurement, the probe messages are sent on the
	session is created on the responder node. The probe messages for		congruent path of the data traffic by the querier node, and are
	Delay measurement are sent in-band by the querier node to measure the		used to measure the delay experienced by the actual data traffic
	delay experienced by the actual traffic flowing on the links and SR		flowing on the links and SR Policies.
	Policies. For Loss measurement, in-band probe messages are used to
	collect the traffic counter for the incoming link or incoming SID on		o For Loss Measurement, the probe messages are sent on the congruent
	which the probe query message is received at the responder node R5 as		path of the data traffic by the querier node, and are used to
	it has no PM session state present on the node. The performance		collect the receive traffic counters for the incoming link or
	measurement for Delay and Loss using out-of-band probe query messages		incoming SID where the probe query messages are received at the
	are outside the scope of this document.		responder node (incoming link or incoming SID used as the
			responder node has no PM session state present).
			The In-Situ Operations, Administration, and Maintenance (IOAM)
			mechanisms for SR-MPLS defined in [I-D.spring-ioam-sr-mpls] and for
			SRv6 defined in [I-D.spring-srv6-oam] are used to carry PM
			information in-band as part of the data traffic, and are outside the
			scope of this document.
	3. Probe Messages		3. Probe Messages
	3.1. Probe Query Message		3.1. Probe Query Message
	In this document, procedures using [RFC5357] is used for Delay and		In this document, the probe messages defined in [RFC5357] are used
	Loss measurements for SR links and end-to-end SR Policies. A		for Delay and Loss measurements for SR links and end-to-end SR
	user-configured UDP port is used for identifying PM probe packets		Policies. The user-configured UDP ports (separate UDP port for each
	that does not require to bootstrap PM sessions. A UDP port number		message format) are used for identifying the PM probe packets and to
	from the Dynamic and/or Private Ports range 49152-65535 is used as		avoid signaling to bootstrap PM sessions. This approach is similar
	the destination UDP port. This approach is similar to the one		to the one defined in STAMP protocol [I-D.ippm-stamp]. The IPv4 TTL
	defined in STAMP protocol [I-D.ippm-stamp]. The IPv4 TTL or IPv6 Hop		or IPv6 Hop Limit field of the IP header MUST be set to 255.
	Limit field of the IP header MUST be set to 255.
	3.1.1. Delay Measurement Probe Query Message		3.1.1. Delay Measurement Probe Query Message
	The message content for Delay Measurement probe query message using		The message content for Delay Measurement probe query message using
	UDP header [RFC768] is shown in Figure 1. The DM probe query message		UDP header [RFC768] is shown in Figure 1. The DM probe query message
	is sent with user-configured Destination UDP port number [I-D.ippm-		is sent with user-configured Destination UDP port number for DM. The
	stamp]. The Source UDP port is set to the same value for two-way		Destination UDP port cannot be used as Source port, since the message
	delay measurement. The DM probe query message contains the payload		does not have any indication to distinguish between query and
	for delay measurement defined in Section 4.2.1 of [RFC5357] for TWAMP		response. The DM probe query message contains the payload for delay
	or in Section 4.1.2 of [RFC4656] for OWAMP.		measurement defined in Section 4.1.2 of OWAMP [RFC4656]. As an
			alternative, the DM probe query message contains the payload defined
			in Section 4.2.1 of TWAMP [RFC5357].
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| IP Header |		| IP Header |
	. Source IP Address = Querier IPv4 or IPv6 Address .		. Source IP Address = Querier IPv4 or IPv6 Address .
	. Destination IP Address = Responder IPv4 or IPv6 Address .		. Destination IP Address = Responder IPv4 or IPv6 Address .
	. Protocol = UDP .		. Protocol = UDP .
	. Router Alert Option Not Set .		. Router Alert Option Not Set .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| UDP Header |		| UDP Header |
	skipping to change at page 6, line 28 ¶		skipping to change at page 6, line 43 ¶
	. Destination Port = User-configured Port for Delay Measurement.		. Destination Port = User-configured Port for Delay Measurement.
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| Payload = Message as specified in Section 4.2.1 of RFC 5357 |		| Payload = Message as specified in Section 4.2.1 of RFC 5357 |
	| | Payload = Message as specified in Section 4.1.2 of RFC 4656 |		| | Payload = Message as specified in Section 4.1.2 of RFC 4656 |
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Figure 1: DM Probe Query Message		Figure 1: DM Probe Query Message
	Timestamp field is eight bytes and by default uses the IEEE 1588v2		Timestamp field is eight bytes. It is recommended to use the IEEE
	Precision Time Protocol (PTP) truncated 64-bit timestamp format		1588v2 Precision Time Protocol (PTP) truncated 64-bit timestamp
	[IEEE1588].		format [IEEE1588] using the procedure defined in [RFC8186].
	3.1.2. Loss Measurement Probe Query Message		3.1.1.1. Delay Measurement Message Checksum Complement
	The message content for Loss Measurement probe query message using		The Checksum Complement shown in Figure 3 for OWAMP in [RFC7820] and
	UDP header [RFC768] is shown in Figure 2. The LM probe query message		Figure 4 for TWAMP in [RFC7820] for delay measurement message format
	is sent with user-configured Destination UDP port number [I-D.ippm-		follows the procedure defined in [RFC7820] and can be used optionally
	stamp]. The Source UDP port is set to the same value for two-way		with the procedures defined in this document.
	loss measurement. The LM probe query message contains the payload
	for loss measurement defined below.
	+---------------------------------------------------------------+		3.1.1.2. Delay Measurement Authentication Mode
	| IP Header |
	. Source IP Address = Querier IPv4 or IPv6 Address .
	. Destination IP Address = Responder IPv4 or IPv6 Address .
	. Protocol = UDP .
	. Router Alert Option Not Set .
	. .
	+---------------------------------------------------------------+
	| UDP Header |
	. Source Port = As chosen by Querier .
	. Destination Port = User-configured Port for Loss Measurement .		When using the authenticated mode for delay measurement, the matching
	. .		authentication type (e.g. HMAC-SHA-256) and key are user-configured
	+---------------------------------------------------------------+		on both the querier and responder nodes. A different user-configured
	| Sequence Number |		destination UDP port is required for the delay measurement in
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		authentication mode due to the different probe message format.
	| Transmit Counter |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Receive Counter |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender Sequence Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender Counter |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender TTL | Block Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Padding |
	. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 2A: LM Probe Query Message for TWAMP		3.1.2. Loss Measurement Probe Query Message
	+---------------------------------------------------------------+		The message content for Loss Measurement probe query message using
	| IP Header |		UDP header [RFC768] is shown in Figure 2. The LM probe query message
	. Source IP Address = Querier IPv4 or IPv6 Address .		is sent with user-configured Destination UDP port number for LM.
	. Destination IP Address = Responder IPv4 or IPv6 Address .		Different Destination UDP ports are used for direct-mode and
	. Protocol = UDP .		inferred-mode loss measurements. The Destination UDP port cannot be
	. Router Alert Option Not Set .		used as Source port, since the message does not have any indication
	. .		to distinguish between query and response. The LM probe query
	+---------------------------------------------------------------+		message contains the payload for loss measurement as defined in
	| UDP Header |		Figure 2. An alternative, the LM probe query message contains the
	. Source Port = As chosen by Querier .		payload defined in Figure 8.
	. Destination Port = User-configured Port for Loss Measurement .
	. .
	+---------------------------------------------------------------+
	| Sequence Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MBZ (12 octets) |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Transmit Counter |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MBZ (8 octets) |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Receive Counter |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MBZ (8 octets) |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender Sequence Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MBZ (12 octets) |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender Counter |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MBZ (8 octets) |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender TTL | Block Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MBZ (12 octets) |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| HMAC (16 octets) |
	| |
	| |
	| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Padding |
	. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 2B: LM Probe Query Message for TWAMP - Authenticated Mode		Both of these LM message formats define fixed locations for the
			counters in the payload and are easy to implement in hardware. In
			addition, new LM messages do not require any backwards compatibility
			or support for the existing DM message formats in [RFC5357].
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| IP Header |		| IP Header |
	. Source IP Address = Querier IPv4 or IPv6 Address .		. Source IP Address = Querier IPv4 or IPv6 Address .
	. Destination IP Address = Responder IPv4 or IPv6 Address .		. Destination IP Address = Responder IPv4 or IPv6 Address .
	. Protocol = UDP .		. Protocol = UDP .
	. Router Alert Option Not Set .		. Router Alert Option Not Set .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| UDP Header |		| UDP Header |
	skipping to change at page 9, line 4 ¶		skipping to change at page 7, line 42 ¶
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| IP Header |		| IP Header |
	. Source IP Address = Querier IPv4 or IPv6 Address .		. Source IP Address = Querier IPv4 or IPv6 Address .
	. Destination IP Address = Responder IPv4 or IPv6 Address .		. Destination IP Address = Responder IPv4 or IPv6 Address .
	. Protocol = UDP .		. Protocol = UDP .
	. Router Alert Option Not Set .		. Router Alert Option Not Set .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| UDP Header |		| UDP Header |
	. Source Port = As chosen by Querier .		. Source Port = As chosen by Querier .
	. Destination Port = User-configured Port for Loss Measurement .		. Destination Port = User-configured Port for Loss Measurement .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| Sequence Number |		| Sequence Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Transmit Counter |		| Transmit Counter |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender TTL | Block Number |		| Sender TTL |X|B|0|0|0|0|0|0| Block Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Padding |		| |
			. Packet Padding .
	. .		. .
			| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| | Checksum Complement |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 2C: LM Probe Query Message for OWAMP		Figure 2A: LM Probe Query Message for OWAMP
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| IP Header |		| IP Header |
	. Source IP Address = Querier IPv4 or IPv6 Address .		. Source IP Address = Querier IPv4 or IPv6 Address .
	. Destination IP Address = Responder IPv4 or IPv6 Address .		. Destination IP Address = Responder IPv4 or IPv6 Address .
	. Protocol = UDP .		. Protocol = UDP .
	. Router Alert Option Not Set .		. Router Alert Option Not Set .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| UDP Header |		| UDP Header |
	skipping to change at page 9, line 46 ¶		skipping to change at page 8, line 39 ¶
	| MBZ (12 octets) |		| MBZ (12 octets) |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Transmit Counter |		| Transmit Counter |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MBZ (8 octets) |		| MBZ (8 octets) |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender TTL | Block Number |		| Sender TTL |X|B|0|0|0|0|0|0| Block Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MBZ (12 octets) |		| MBZ (12 octets) |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| HMAC (16 octets) |		| HMAC (16 octets) |
	| |		| |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Padding |		| |
			. Packet Padding .
	. .		. .
			| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| | Checksum Complement |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Figure 2D: LM Probe Query Message for OWAMP - Authenticated Mode		Figure 2B: LM Probe Query Message for OWAMP - Authenticated Mode
	Sequence Number (32-bit): As defined in [RFC5357].		Sequence Number (32-bit): As defined in [RFC5357].
	Transmit Counter (64-bit): The number of packets sent by the querier		Transmit Counter (64-bit): The number of packets sent by the querier
	node in the query message and by the responder node in the response		node in the query message and by the responder node in the response
	message. The counter is always written at fixed location in the		message. The counter is always written at the fixed location in the
	probe query and response messages.		probe query and response messages.
	Receive Counter (64-bit): The number of packets received at the		Receive Counter (64-bit): The number of packets received at the
	responder node. It is written by the responder node in the probe		responder node. It is written by the responder node in the probe
	response message.		response message.
	Sender Counter (64-bit): This is the exact copy of the transmit		Sender Counter (64-bit): This is the exact copy of the transmit
	counter from the received query message. It is written by the		counter from the received query message. It is written by the
	responder node in the probe response message.		responder node in the probe response message.
	Sender Sequence Number (32-bit): As defined in [RFC5357].		Sender Sequence Number (32-bit): As defined in [RFC5357].
	Sender TTL: As defined in [RFC5357].		Sender TTL: As defined in [RFC5357].
	Block Number (24-bit): The Loss Measurement using Alternate-Marking		Flag: The meanings of the Flag bits are:
			X: Extended counter format indicator. Indicates the use of
			extended (64-bit) counter values. Initialized to 1 upon creation
			(and prior to transmission) of an LM Query and copied from an LM
			Query to an LM response. Set to 0 when the LM message is
			transmitted or received over an interface that writes 32-bit
			counter values.
			B: Octet (byte) count. When set to 1, indicates that the Counter
			1-4 fields represent octet counts. The octet count applies to all
			packets within the LM scope, and the octet count of a packet sent
			or received over a channel includes the total length of that
			packet (but excludes headers, labels, or framing of the channel
			itself). When set to 0, indicates that the Counter fields
			represent packet counts.
			0: Set to 0.
			Block Number (16-bit): The Loss Measurement using Alternate-Marking
	method defined in [RFC8321] requires to identify the Block Number (or		method defined in [RFC8321] requires to identify the Block Number (or
	color) of the traffic counters. The probe query and response		color) of the traffic counters. The probe query and response
	messages carry Block Number for the traffic counters for loss		messages carry Block Number for the traffic counters for loss
	measurement. In both probe query and response messages, the counters		measurement. In both probe query and response messages, the counters
	MUST belong to the same Block Number.		MUST belong to the same Block Number.
	The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of		HMAC: The PM probe packet in authenticated mode includes a key Hashed
	the SR-MPLS Policy is used for accounting received traffic on the		Message Authentication Code (HMAC) ([RFC2104]) hash. Each probe
	egress node for loss measurement.		query and response messages are authenticated by adding Sequence
			Number with Hashed Message Authentication Code (HMAC) TLV. It can
			use HMAC-SHA-256 truncated to 128 bits (similarly to the use of it in
			IPSec defined in [RFC4868]); hence the length of the HMAC field is 16
			octets.
			HMAC uses own key and the definition of the mechanism to distribute
			the HMAC key is outside the scope of this document.
			In authenticated mode, only the sequence number is encrypted, and the
			other payload fields are sent in clear text. The probe packet MAY
			include Comp.MBZ (Must Be Zero) variable length field to align the
			packet on 16 octets boundary.
			3.1.2.1. Loss Measurement Message Checksum Complement
			The Checksum Complement shown in Figure 2 for loss measurement
			message format follows the procedure defined in [RFC7820] and can be
			used optionally with the procedures defined in this document.
			3.1.2.2. Loss Measurement Authentication Mode
			When using the authenticated mode for loss measurement, the matching
			authentication type (e.g. HMAC-SHA-256) and key are user-configured
			on both the querier and responder nodes. A different user-configured
			destination UDP port is required for the loss measurement in
			authentication mode due to the different message format.
	3.1.3. Probe Query for SR Links		3.1.3. Probe Query for SR Links
	The probe query message as defined in Figure 1 is sent in-band for		The probe query message as defined in Figure 1 is sent on the
	Delay measurement. The probe query message as defined in Figure 2 is		congruent path of the data traffic for Delay measurement. The probe
	sent in-band for Loss measurement.		query message as defined in Figure 2 is sent on the congruent path of
			the data traffic for Loss measurement.
	3.1.4. Probe Query for End-to-end Measurement for SR Policy		3.1.4. Probe Query for End-to-end Measurement for SR Policy
	3.1.4.1. Probe Query Message for SR-MPLS Policy		3.1.4.1. Probe Query Message for SR-MPLS Policy
	The message content for in-band probe query message using UDP header		The message content for the probe query message using UDP header for
	for end-to-end performance measurement of SR-MPLS Policy is shown in		end-to-end performance measurement of SR-MPLS Policy is shown in
	Figure 3.		Figure 3.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Segment List(0) | TC |S| TTL |		| Segment List(1) | TC |S| TTL |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	. .		. .
	. .		. .
	. .		. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Segment List(n) | TC |S| TTL |		| Segment List(n) | TC |S| TTL |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| PSID | TC |S| TTL |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Message as shown in Figure 1 for DM or Figure 2 for LM |		| Message as shown in Figure 1 for DM or Figure 2 for LM |
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Figure 3: Probe Query Message for SR-MPLS Policy		Figure 3: Probe Query Message for SR-MPLS Policy
	The Segment List (SL) can be empty to indicate Implicit NULL label		The Segment List (SL) can be empty to indicate Implicit NULL label
	case.		case.
			The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of
			the SR-MPLS Policy is used for accounting received traffic on the
			egress node for loss measurement. The PSID is not required for
			end-to-end SR Policy delay measurement.
	3.1.4.2. Probe Query Message for SRv6 Policy		3.1.4.2. Probe Query Message for SRv6 Policy
	The in-band probe query messages using UDP header for end-to-end		An SRv6 Policy setup using the SRv6 Segment Routing Header (SRH) and
	performance measurement of an SRv6 Policy is sent using SRv6 Segment		a Segment List as defined in [I-D.6man-segment-routing-header]. The
	Routing Header (SRH) and Segment List of the SRv6 Policy as defined		probe query messages using UDP header for end-to-end performance
	in [I-D.6man-segment-routing-header] and is shown in Figure 4.		measurement of an SRv6 Policy is sent using its SRv6 Segment Routing
			Header (SRH) and Segment List as shown in Figure 4.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| SRH |		| SRH |
	. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .		. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .
	. .		. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Message as shown in Figure 1 for DM or Figure 2 for LM |		| Message as shown in Figure 1 for DM or Figure 2 for LM |
	. (Using IPv6 Addresses) .		. (Using IPv6 Addresses) .
	skipping to change at page 11, line 50 ¶		skipping to change at page 12, line 4 ¶
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| SRH |		| SRH |
	. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .		. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .
	. .		. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Message as shown in Figure 1 for DM or Figure 2 for LM |		| Message as shown in Figure 1 for DM or Figure 2 for LM |
	. (Using IPv6 Addresses) .		. (Using IPv6 Addresses) .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Figure 4: Probe Query Message for SRv6 Policy		Figure 4: Probe Query Message for SRv6 Policy
	For delay measurement of SRv6 Policy, END function END.OTP		For delay measurement of SRv6 Policy using SRH, END function END.OTP
	[I-D.spring-srv6-oam] is used with the target SRv6 SID to punt probe		[I-D.spring-srv6-oam] is used with the target SRv6 SID to punt probe
	messages on the target node, as shown in Figure 4. Similarly, for		messages on the target node, as shown in Figure 4. Similarly, for
	loss measurement of SRv6 Policy, END function END.OP		loss measurement of SRv6 Policy, END function END.OP
	[I-D.spring-srv6-oam] is used with target SRv6 SID to punt probe		[I-D.spring-srv6-oam] is used with target SRv6 SID to punt probe
	messages on the target node.		messages on the target node.
	3.2. Probe Response Message		3.2. Probe Response Message
	The probe response message is sent using the IP/UDP information from		The probe response message is sent using the IP/UDP information from
	the probe query message. The content of the probe response message		the probe query message. The content of the probe response message
	skipping to change at page 12, line 31 ¶		skipping to change at page 12, line 35 ¶
	. Destination IP Address = Source IP Address from Query .		. Destination IP Address = Source IP Address from Query .
	. Protocol = UDP .		. Protocol = UDP .
	. Router Alert Option Not Set .		. Router Alert Option Not Set .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| UDP Header |		| UDP Header |
	. Source Port = As chosen by Responder .		. Source Port = As chosen by Responder .
	. Destination Port = Source Port from Query .		. Destination Port = Source Port from Query .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	| Payload as specified in Section 4.2.1 of RFC 5357, or |		| DM Payload as specified in Section 4.2.1 of RFC 5357, or |
	. Payload as specified in Figure 2 in this document .		. LM Payload as specified in Figure 8 in this document .
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Figure 5: Probe Response Message		Figure 5: Probe Response Message
	3.2.1. One-way Measurement		+---------------------------------------------------------------+
			| IP Header |
			. Source IP Address = Querier IPv4 or IPv6 Address .
			. Destination IP Address = Responder IPv4 or IPv6 Address .
			. Protocol = UDP .
			. Router Alert Option Not Set .
			. .
			+---------------------------------------------------------------+
			| UDP Header |
			. Source Port = As chosen by Querier .
	For one-way performance measurement, the probe response message as		. Destination Port = User-configured Port for Loss Measurement .
	defined in Figure 5 is sent for both SR links and SR Policies.		. .
			+---------------------------------------------------------------+
			| Sequence Number |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Transmit Counter |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Receive Counter |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Sender Sequence Number |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Sender Counter |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Sender TTL |X|B|0|0|0|0|0|0| Block Number |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| |
			. .
			. Packet Padding .
			. .
			| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| | Checksum Complement |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	3.2.2. Two-way Measurement		Figure 8A: LM Probe Response Message for TWAMP
	For two-way performance measurement, when using a bidirectional		+---------------------------------------------------------------+
	channel, the probe response message as defined in Figure 5 is sent		| IP Header |
	back in-band to the querier node.		. Source IP Address = Querier IPv4 or IPv6 Address .
			. Destination IP Address = Responder IPv4 or IPv6 Address .
			. Protocol = UDP .
			. Router Alert Option Not Set .
			. .
			+---------------------------------------------------------------+
			| UDP Header |
			. Source Port = As chosen by Querier .
			. Destination Port = User-configured Port for Loss Measurement .
			. .
			+---------------------------------------------------------------+
			| Sequence Number |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MBZ (12 octets) |
			| |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Transmit Counter |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MBZ (8 octets) |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Receive Counter |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MBZ (8 octets) |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Sender Sequence Number |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MBZ (12 octets) |
			| |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Sender Counter |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MBZ (8 octets) |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Sender TTL |X|B|0|0|0|0|0|0| Block Number |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MBZ (12 octets) |
			| |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| HMAC (16 octets) |
			| |
			| |
			| |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| |
			. .
			. Packet Padding .
			. .
			| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| | Checksum Complement |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of		Figure 8B: LM Probe Response Message for TWAMP - Authenticated Mode
	the forward SR Policy can be used to find the reverse SR Policy to
	send the probe response message for two-way measurement of SR Policy.
	3.2.2.1. Probe Response Message for SR-MPLS Policy		3.2.1. One-way Measurement Mode
			In one-way performance measurement mode, the probe response message
			as defined in Figure 5 is sent for both SR links and SR Policies.
	The message content for sending probe response message in-band using		3.2.2. Two-way Measurement Mode
	UDP header for two-way end-to-end performance measurement of an
	SR-MPLS Policy is shown in Figure 6.		In two-way performance measurement mode, when using a bidirectional
			path, the probe response message as defined in Figure 5 is sent back
			on the congruent path of the data traffic to the querier node.
			3.2.2.1. Return Path TLV
			For two-way performance measurement, the responder node needs to send
			the probe response message on a specific reverse SR path. This way
			the destination node does not require any additional SR Policy state.
			The querier node can request in the probe query message to the
			responder node to send a response back on a given reverse path
			(typically co-routed path for two-way measurement).
			[I-D.ippm-stamp-option-tlv] defines STAMP probe query messages that
			can include one or more optional TLVs. New TLV Type (TBA1) is
			defined in this document for Return Path to carry reverse SR path for
			probe response messages (in the payload of the message). The format
			of the Return Path TLV is shown in Figure 8A and 8B:
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Segment List(0) | TC |S| TTL |		| Type = TBA1 | Length | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Return Path Sub-TLVs |
			. .
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			Figure 8A: Return Path TLV
			0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Type | Length | Reserved |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Segment List(1) |
			. .
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			. .
			. .
			. .
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Segment List(n) |
			. .
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			Figure 8B: Segment List Sub-TLV in Return Path TLV
			The Sub-TLV in the Return Path TLV can be one of the following Types:
			o Type (value 1): SR-MPLS Label Stack of the Reverse SR Policy
			o Type (value 2): SR-MPLS Binding SID [I-D.pce-binding-label-sid] of
			the Reverse SR Policy
			o Type (value 3): SRv6 Segment List of the Reverse SR Policy
			o Type (value 4): SRv6 Binding SID [I-D.pce-binding-label-sid] of
			the Reverse SR Policy
			With sub-TLV Type 1, the Segment List(1) can be used by the responder
			node to compute the next-hop IP address and outgoing interface to
			send the probe response messages.
			The Return Path TLV is optional. The PM querier node MUST only
			insert one Return Path TLV in the probe query message and the
			responder node MUST only process the first Return Path TLV in the
			probe query message and ignore other Return Path TLVs if present.
			The responder node MUST send probe response message back on the
			reverse path specified in the Return Path TLV and MUST NOT add Return
			Path TLV in the probe response message.
			3.2.2.2. Probe Response Message for SR-MPLS Policy
			The message content for sending probe response message using the UDP
			header for two-way end-to-end performance measurement of an SR-MPLS
			Policy is shown in Figure 6.
			0 1 2 3
			0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Segment List(1) | TC |S| TTL |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	. .		. .
	. .		. .
	. .		. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Segment List(n) | TC |S| TTL |		| Segment List(n) | TC |S| TTL |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Message as shown in Figure 5 |		| Message as shown in Figure 5 |
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Figure 6: Probe Response Message for SR-MPLS Policy		Figure 6: Probe Response Message for SR-MPLS Policy
	3.2.2.2. Probe Response Message for SRv6 Policy		The Path Segment Identifier (PSID) [I-D.spring-mpls-path-segment] of
			the forward SR Policy can be used to find the reverse SR Policy to
			send the probe response message for two-way measurement of SR Policy.
	The message content for sending probe response message in-band using		3.2.2.3. Probe Response Message for SRv6 Policy
	UDP header for two-way end-to-end performance measurement of an SRv6
	Policy is shown in Figure 7.		The message content for sending probe response message on the
			congruent path of the data traffic using UDP header for two-way
			end-to-end performance measurement of an SRv6 Policy with SRH is
			shown in Figure 7.
	0 1 2 3		0 1 2 3
	0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1		0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| SRH |		| SRH |
	. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .		. END.OTP (DM) or END.OP (LM) with Target SRv6 SID .
	. .		. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Message as shown in Figure 5 (with IPv6 Addresses) |		| Message as shown in Figure 5 (with IPv6 Addresses) |
	. .		. .
	+---------------------------------------------------------------+		+---------------------------------------------------------------+
	Figure 7: Probe Response Message for SRv6 Policy		Figure 7: Probe Response Message for SRv6 Policy
			3.2.3. Loopback Measurement Mode
			The Loopback measurement mode can be used to measure round-trip delay
			for a bidirectional Path. The probe query messages in this case
			either carry the reverse Path information as part of the SR header or
			set the querier address as the destination address in the IP header.
			The responder node does not process the PM probe messages and
			generate response messages.
	4. Packet Loss Calculation		4. Packet Loss Calculation
	The formula for calculating the one-way packet loss using counters		The formula for calculating the one-way packet loss using packet
	for a given block number is as following:		counters for a given block number is as following:
	o One-way Packet_Loss[n-1, n] = (Sender_Counter[n] -		One-way Packet_Loss[n-1, n]
	Sender_Counter[n-1]) - (Receive_Counter[n] - Receive_Counter[n-1])		= (Sender_Counter[n] - Sender_Counter[n-1])
			- (Receive_Counter[n] - Receive_Counter[n-1])
	5. Performance Measurement for P2MP SR Policies		5. Performance Measurement for P2MP SR Policies
	The procedures for delay and loss measurement described in this		The procedures for delay and loss measurement described in this
	document for Point-to-Point (P2P) SR-MPLS Policies are also equally		document for Point-to-Point (P2P) SR Policies
	applicable to the Point-to-Multipoint (P2MP) SR Policies.		[I-D.spring-segment-routing-policy] are also equally applicable to
			the Point-to-Multipoint (P2MP) SR Policies
			[I-D.spring-sr-p2mp-policy] as following:
	6. ECMP Support		o The querier root node sends probe query messages using the either
			Spray P2MP segment or TreeSID P2MP segment defined in
			[I-D.spring-sr-p2mp-policy] over the P2MP SR Policy.
			o Each responder leaf node sends its IP address in the Source
			Address of the probe response messages. This allows the querier
			root node to identify the responder leaf nodes of the P2MP SR
			Policy.
			o The P2MP root node measures the end-to-end delay and loss
			performance for each P2MP leaf node.
			6. ECMP Support for SR Policies
	An SR Policy can have ECMPs between the source and transit nodes,		An SR Policy can have ECMPs between the source and transit nodes,
	between transit nodes and between transit and destination nodes.		between transit nodes and between transit and destination nodes.
	Usage of Anycast SID [RFC8402] by an SR Policy can result in ECMP		Usage of Anycast SID [RFC8402] by an SR Policy can result in ECMP
	paths via transit nodes part of that Anycast group. The PM probe		paths via transit nodes part of that Anycast group. The PM probe
	messages need to be sent to traverse different ECMP paths to measure		messages need to be sent to traverse different ECMP paths to measure
	performance delay of an SR Policy.		performance delay of an SR Policy.
	Forwarding plane has various hashing functions available to forward		Forwarding plane has various hashing functions available to forward
	packets on specific ECMP paths. Following mechanisms can be used in		packets on specific ECMP paths. Following mechanisms can be used in
	PM probe messages to take advantage of the hashing function in		PM probe messages to take advantage of the hashing function in
	forwarding plane to influence the path taken by them.		forwarding plane to influence the path taken by them.
	o The mechanisms described in [RFC8029] [RFC5884] for handling ECMPs		o The mechanisms described in [RFC8029] and [RFC5884] for handling
	are also applicable to the performance measurement. In the IP/UDP		ECMPs are also applicable to the performance measurement. In the
	header of the PM probe messages, Destination Addresses in 127/8		IP/UDP header of the PM probe messages, Destination Addresses in
	range for IPv4 or 0:0:0:0:0:FFFF:7F00/104 range for IPv6 can be		127/8 range for IPv4 or 0:0:0:0:0:FFFF:7F00/104 range for IPv6 can
	used to exercise a particular ECMP path. As specified in		be used to exercise a particular ECMP path. As specified in
	[RFC6437], 3-tuple of Flow Label, Source Address and Destination		[RFC6437], 3-tuple of Flow Label, Source Address and Destination
	Address fields in the IPv6 header can also be used.		Address fields in the IPv6 header can also be used.
	o For SR-MPLS, entropy label [RFC6790] in the PM probe messages can		o For SR-MPLS Policy, entropy label [RFC6790] can be used in the PM
	be used.		probe messages.
	o For SRv6, Flow Label in SRH [I-D.6man-segment-routing-header] of		o For SRv6 Policy using SRH, Flow Label in the SRH
	the PM probe messages can be used.		[I-D.6man-segment-routing-header] of the PM probe messages can be
			used.
	7. Security Considerations		7. Security Considerations
	The performance measurement is intended for deployment in		The performance measurement is intended for deployment in
	well-managed private and service provider networks. As such, it		well-managed private and service provider networks. As such, it
	assumes that a node involved in a measurement operation has		assumes that a node involved in a measurement operation has
	previously verified the integrity of the path and the identity of the		previously verified the integrity of the path and the identity of the
	far end responder node.		far end responder node.
	If desired, attacks can be mitigated by performing basic validation		If desired, attacks can be mitigated by performing basic validation
	and sanity checks, at the querier, of the counter or timestamp fields		and sanity checks, at the querier, of the counter or timestamp fields
	in received measurement response messages. The minimal state		in received measurement response messages. The minimal state
	associated with these protocols also limits the extent of measurement		associated with these protocols also limits the extent of measurement
	disruption that can be caused by a corrupt or invalid message to a		disruption that can be caused by a corrupt or invalid message to a
	single query/response cycle.		single query/response cycle.
	Use of HMAC-SHA-256 in the authenticated mode defined in this		Use of HMAC-SHA-256 in the authenticated mode protects the data
	document protects the data integrity of the probe messages. SRv6 has		integrity of the probe messages. SRv6 has HMAC protection
	HMAC protection authentication defined for SRH		authentication defined for SRH [I-D.6man-segment-routing-header].
	[I-D.6man-segment-routing-header]. Hence, PM probe messages for SRv6		Hence, PM probe messages for SRv6 may not need authentication mode.
	may not need authentication mode. Cryptographic measures may be		Cryptographic measures may be enhanced by the correct configuration
	enhanced by the correct configuration of access-control lists and		of access-control lists and firewalls.
	firewalls.
	8. IANA Considerations		8. IANA Considerations
	This document does not require any IANA actions.		IANA is requested to allocate values for the following Return Path
			TLV Type for [I-D.ippm-stamp-option-tlv] to be carried in PM probe
			query messages:
			o Type TBA1: Return Path TLV
	9. References		9. References
	9.1. Normative References		9.1. Normative References
	[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,		[RFC768] Postel, J., "User Datagram Protocol", STD 6, RFC 768,
	August 1980.		August 1980.
	[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate		[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
	Requirement Levels", RFC 2119, March 1997.		Requirement Levels", RFC 2119, March 1997.
	skipping to change at page 15, line 47 ¶		skipping to change at page 20, line 19 ¶
	[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.		[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
	Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",		Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
	RFC 5357, October 2008.		RFC 5357, October 2008.
	[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC		[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
	2119 Key Words", RFC 8174, May 2017.		2119 Key Words", RFC 8174, May 2017.
	[I-D.spring-srv6-oam] Ali, Z., et al., "Operations, Administration,		[I-D.spring-srv6-oam] Ali, Z., et al., "Operations, Administration,
	and Maintenance (OAM) in Segment Routing Networks with		and Maintenance (OAM) in Segment Routing Networks with
	IPv6 Data plane (SRv6)", draft-ali-spring-srv6-oam.		IPv6 Data plane (SRv6)", draft-ali-spring-srv6-oam, work
			in progress.
			[I-D.ippm-stamp-option-tlv] Mirsky, G., et al., "Simple Two-way
			Active Measurement Protocol Optional Extensions",
			draft-mirsky-ippm-stamp-option-tlv, work in progress.
	9.2. Informative References		9.2. Informative References
	[IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock		[IEEE1588] IEEE, "1588-2008 IEEE Standard for a Precision Clock
	Synchronization Protocol for Networked Measurement and		Synchronization Protocol for Networked Measurement and
	Control Systems", March 2008.		Control Systems", March 2008.
	[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.		June 2010.
	[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,		[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
	"IPv6 Flow Label Specification", RFC 6437, November 2011.		"IPv6 Flow Label Specification", RFC 6437, November 2011.
	[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and		[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
	L. Yong, "The Use of Entropy Labels in MPLS Forwarding",		L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
	RFC 6790, November 2012.		RFC 6790, November 2012.
			[RFC7820] Mizrahi, T., "UDP Checksum Complement in the One-Way
			Active Measurement Protocol (OWAMP) and Two-Way Active
			Measurement Protocol (TWAMP)", RFC 7820, March 2016.
	[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Kumar, N.,		[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Kumar, N.,
	Aldrin, S. and M. Chen, "Detecting Multiprotocol Label		Aldrin, S. and M. Chen, "Detecting Multiprotocol Label
	Switched (MPLS) Data-Plane Failures", RFC 8029, March		Switched (MPLS) Data-Plane Failures", RFC 8029, March
	2017.		2017.
			[RFC8186] Mirsky, G., and I. Meilik, "Support of the IEEE 1588
			Timestamp Format in a Two-Way Active Measurement Protocol
			(TWAMP)", RFC 8186, June 2017.
	[RFC8321] Fioccola, G. Ed., "Alternate-Marking Method for Passive		[RFC8321] Fioccola, G. Ed., "Alternate-Marking Method for Passive
	and Hybrid Performance Monitoring", RFC 8321, January		and Hybrid Performance Monitoring", RFC 8321, January
	2018.		2018.
	[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,		[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
	Decraene, B., Litkowski, S., and R. Shakir, "Segment		Decraene, B., Litkowski, S., and R. Shakir, "Segment
	Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,		Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
	July 2018, <https://www.rfc-editor.org/info/rfc8402>.		July 2018, <https://www.rfc-editor.org/info/rfc8402>.
	[I-D.spring-segment-routing-policy] Filsfils, C., et al., "Segment		[I-D.spring-segment-routing-policy] Filsfils, C., et al., "Segment
	Routing Policy Architecture",		Routing Policy Architecture",
	draft-ietf-spring-segment-routing-policy, work in		draft-ietf-spring-segment-routing-policy, work in
	progress.		progress.
	[I-D.spring-sr-p2mp-policy] Voyer, D. Ed., et al., "SR Replication		[I-D.spring-sr-p2mp-policy] Voyer, D. Ed., et al., "SR Replication
	Policy for P2MP Service Delivery",		Policy for P2MP Service Delivery",
	draft-voyer-spring-sr-p2mp-policy, work in progress.		draft-voyer-spring-sr-p2mp-policy, work in progress.
	[I-D.spring-mpls-path-segment] Cheng, W., et al., "Path Segment in		[I-D.spring-mpls-path-segment] Cheng, W., et al., "Path Segment in
	MPLS Based Segment Routing Network", draft-cheng-spring-		MPLS Based Segment Routing Network",
	mpls-path-segment, work in progress.		draft-ietf-spring-mpls-path-segment, work in progress.
	[I-D.6man-segment-routing-header] Filsfils, C., et al., "IPv6		[I-D.6man-segment-routing-header] Filsfils, C., et al., "IPv6
	Segment Routing Header (SRH)",		Segment Routing Header (SRH)",
	draft-ietf-6man-segment-routing-header, work in progress.		draft-ietf-6man-segment-routing-header, work in progress.
	[I-D.ippm-stamp] Mirsky, G. et al. "Simple Two-way Active		[I-D.ippm-stamp] Mirsky, G. et al. "Simple Two-way Active
	Measurement Protocol", draft-ietf-ippm-stamp, work in		Measurement Protocol", draft-ietf-ippm-stamp, work in
	progress.		progress.
			[I-D.pce-binding-label-sid] Filsfils, C., et al., "Carrying Binding
			Label Segment-ID in PCE-based Networks",
			draft-sivabalan-pce-binding-label-sid, work in progress.
	[BBF.TR-390] "Performance Measurement from IP Edge to Customer		[BBF.TR-390] "Performance Measurement from IP Edge to Customer
	Equipment using TWAMP Light", BBF TR-390, May 2017.		Equipment using TWAMP Light", BBF TR-390, May 2017.
			[I-D.spring-ioam-sr-mpls] Gandhi, R. Ed., et al., "Segment Routing
			with MPLS Data Plane Encapsulation for In-situ OAM Data",
			draft-gandhi-spring-ioam-sr-mpls, work in progress.
			[RFC2104] Krawczyk, H., Bell-are, M., and R. Canetti, "HMAC: Keyed-
			Hashing for Message Authentication", RFC 2104, February
			1997.
			[RFC4868] Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
			384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007.
	Acknowledgments		Acknowledgments
	TBA		The authors would like to thank Thierry Couture for various
			discussions on the use-cases for TWAMP in segment routing. The
			authors would also like to thank Greg Mirsky for reviewing this
			document and providing useful comments and suggestions.
	Authors' Addresses		Authors' Addresses
	Rakesh Gandhi (editor)		Rakesh Gandhi (editor)
	Cisco Systems, Inc.		Cisco Systems, Inc.
	Canada		Canada
	Email: rgandhi@cisco.com		Email: rgandhi@cisco.com
	Clarence Filsfils		Clarence Filsfils
	Cisco Systems, Inc.		Cisco Systems, Inc.
	Email: cfilsfil@cisco.com		Email: cfilsfil@cisco.com
	Daniel Voyer		Daniel Voyer
	Bell Canada		Bell Canada
	Email: daniel.voyer@bell.ca		Email: daniel.voyer@bell.ca
			Mach(Guoyi) Chen
			Huawei
			Email: mach.chen@huawei.com
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