draft-smack-mpls-rfc4379bis-08.txt		draft-smack-mpls-rfc4379bis-09.txt
	Network Working Group K. Kompella		Network Working Group K. Kompella
	Internet-Draft Juniper Networks, Inc.		Internet-Draft Juniper Networks
	Obsoletes: 4379, 6829 (if approved) C. Pignataro		Obsoletes: 4379, 6829 (if approved) C. Pignataro
	Intended status: Standards Track N. Kumar		Intended status: Standards Track N. Kumar
	Expires: May 22, 2016 Cisco		Expires: June 20, 2016 Cisco
	S. Aldrin		S. Aldrin
	Google		Google
	M. Chen		M. Chen
	Huawei		Huawei
	November 19, 2015		December 18, 2015
	Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures		Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures
	draft-smack-mpls-rfc4379bis-08		draft-smack-mpls-rfc4379bis-09
	Abstract		Abstract
	This document describes a simple and efficient mechanism that can be		This document describes a simple and efficient mechanism that can be
	used to detect data plane failures in Multi-Protocol Label Switching		used to detect data plane failures in Multi-Protocol Label Switching
	(MPLS) Label Switched Paths (LSPs). There are two parts to this		(MPLS) Label Switched Paths (LSPs). There are two parts to this
	document: information carried in an MPLS "echo request" and "echo		document: information carried in an MPLS "echo request" and "echo
	reply" for the purposes of fault detection and isolation, and		reply" for the purposes of fault detection and isolation, and
	mechanisms for reliably sending the echo reply.		mechanisms for reliably sending the echo reply.
	skipping to change at page 1, line 43		skipping to change at page 1, line 43
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on May 22, 2016.		This Internet-Draft will expire on June 20, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	skipping to change at page 2, line 37		skipping to change at page 2, line 37
	3.1. Return Codes . . . . . . . . . . . . . . . . . . . . . . 13		3.1. Return Codes . . . . . . . . . . . . . . . . . . . . . . 13
	3.2. Target FEC Stack . . . . . . . . . . . . . . . . . . . . 13		3.2. Target FEC Stack . . . . . . . . . . . . . . . . . . . . 13
	3.2.1. LDP IPv4 Prefix . . . . . . . . . . . . . . . . . . . 15		3.2.1. LDP IPv4 Prefix . . . . . . . . . . . . . . . . . . . 15
	3.2.2. LDP IPv6 Prefix . . . . . . . . . . . . . . . . . . . 15		3.2.2. LDP IPv6 Prefix . . . . . . . . . . . . . . . . . . . 15
	3.2.3. RSVP IPv4 LSP . . . . . . . . . . . . . . . . . . . . 15		3.2.3. RSVP IPv4 LSP . . . . . . . . . . . . . . . . . . . . 15
	3.2.4. RSVP IPv6 LSP . . . . . . . . . . . . . . . . . . . . 16		3.2.4. RSVP IPv6 LSP . . . . . . . . . . . . . . . . . . . . 16
	3.2.5. VPN IPv4 Prefix . . . . . . . . . . . . . . . . . . . 16		3.2.5. VPN IPv4 Prefix . . . . . . . . . . . . . . . . . . . 16
	3.2.6. VPN IPv6 Prefix . . . . . . . . . . . . . . . . . . . 17		3.2.6. VPN IPv6 Prefix . . . . . . . . . . . . . . . . . . . 17
	3.2.7. L2 VPN Endpoint . . . . . . . . . . . . . . . . . . . 18		3.2.7. L2 VPN Endpoint . . . . . . . . . . . . . . . . . . . 18
	3.2.8. FEC 128 Pseudowire - IPv4 (Deprecated) . . . . . . . 18		3.2.8. FEC 128 Pseudowire - IPv4 (Deprecated) . . . . . . . 18
	3.2.9. FEC 128 Pseudowire - IPv4 (Current) . . . . . . . . . 19		3.2.9. FEC 128 Pseudowire - IPv4 (Current) . . . . . . . . . 18
	3.2.10. FEC 129 Pseudowire - IPv4 . . . . . . . . . . . . . . 20		3.2.10. FEC 129 Pseudowire - IPv4 . . . . . . . . . . . . . . 19
	3.2.11. BGP Labeled IPv4 Prefix . . . . . . . . . . . . . . . 21		3.2.11. BGP Labeled IPv4 Prefix . . . . . . . . . . . . . . . 20
	3.2.12. BGP Labeled IPv6 Prefix . . . . . . . . . . . . . . . 21		3.2.12. BGP Labeled IPv6 Prefix . . . . . . . . . . . . . . . 20
	3.2.13. Generic IPv4 Prefix . . . . . . . . . . . . . . . . . 22		3.2.13. Generic IPv4 Prefix . . . . . . . . . . . . . . . . . 21
	3.2.14. Generic IPv6 Prefix . . . . . . . . . . . . . . . . . 22		3.2.14. Generic IPv6 Prefix . . . . . . . . . . . . . . . . . 21
	3.2.15. Nil FEC . . . . . . . . . . . . . . . . . . . . . . . 23		3.2.15. Nil FEC . . . . . . . . . . . . . . . . . . . . . . . 22
	3.2.16. FEC 128 Pseudowire - IPv6 . . . . . . . . . . . . . . 23		3.2.16. FEC 128 Pseudowire - IPv6 . . . . . . . . . . . . . . 22
	3.2.17. FEC 129 Pseudowire - IPv6 . . . . . . . . . . . . . . 24		3.2.17. FEC 129 Pseudowire - IPv6 . . . . . . . . . . . . . . 23
	3.3. Downstream Mapping . . . . . . . . . . . . . . . . . . . 25		3.3. Downstream Mapping (Deprecated) . . . . . . . . . . . . . 24
	3.3.1. Multipath Information Encoding . . . . . . . . . . . 28		3.4. Downstream Detailed Mapping . . . . . . . . . . . . . . . 24
	3.3.2. Downstream Router and Interface . . . . . . . . . . . 30		3.4.1. Multipath Information Encoding . . . . . . . . . . . 24
	3.4. Pad TLV . . . . . . . . . . . . . . . . . . . . . . . . . 31		3.4.2. Downstream Router and Interface . . . . . . . . . . . 26
	3.5. Vendor Enterprise Number . . . . . . . . . . . . . . . . 31		3.5. Pad TLV . . . . . . . . . . . . . . . . . . . . . . . . . 27
	3.6. Interface and Label Stack . . . . . . . . . . . . . . . . 32		3.6. Vendor Enterprise Number . . . . . . . . . . . . . . . . 27
	3.7. Errored TLVs . . . . . . . . . . . . . . . . . . . . . . 33		3.7. Interface and Label Stack . . . . . . . . . . . . . . . . 27
	3.8. Reply TOS Byte TLV . . . . . . . . . . . . . . . . . . . 33		3.8. Errored TLVs . . . . . . . . . . . . . . . . . . . . . . 29
	4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 34		3.9. Reply TOS Byte TLV . . . . . . . . . . . . . . . . . . . 29
	4.1. Dealing with Equal-Cost Multi-Path (ECMP) . . . . . . . . 34		4. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 29
	4.2. Testing LSPs That Are Used to Carry MPLS Payloads . . . . 35		4.1. Dealing with Equal-Cost Multi-Path (ECMP) . . . . . . . . 30
	4.3. Sending an MPLS Echo Request . . . . . . . . . . . . . . 35		4.2. Testing LSPs That Are Used to Carry MPLS Payloads . . . . 31
	4.4. Receiving an MPLS Echo Request . . . . . . . . . . . . . 36		4.3. Sending an MPLS Echo Request . . . . . . . . . . . . . . 31
	4.4.1. FEC Validation . . . . . . . . . . . . . . . . . . . 42		4.4. Receiving an MPLS Echo Request . . . . . . . . . . . . . 32
	4.5. Sending an MPLS Echo Reply . . . . . . . . . . . . . . . 43		4.4.1. FEC Validation . . . . . . . . . . . . . . . . . . . 38
	4.6. Receiving an MPLS Echo Reply . . . . . . . . . . . . . . 44		4.5. Sending an MPLS Echo Reply . . . . . . . . . . . . . . . 39
	4.7. Issue with VPN IPv4 and IPv6 Prefixes . . . . . . . . . . 44		4.6. Receiving an MPLS Echo Reply . . . . . . . . . . . . . . 40
	4.8. Non-compliant Routers . . . . . . . . . . . . . . . . . . 45		4.7. Issue with VPN IPv4 and IPv6 Prefixes . . . . . . . . . . 40
	5. Security Considerations . . . . . . . . . . . . . . . . . . . 45		4.8. Non-compliant Routers . . . . . . . . . . . . . . . . . . 41
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46		5. Security Considerations . . . . . . . . . . . . . . . . . . . 41
	6.1. Message Types, Reply Modes, Return Codes . . . . . . . . 47		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42
	6.2. TLVs . . . . . . . . . . . . . . . . . . . . . . . . . . 47		6.1. Message Types, Reply Modes, Return Codes . . . . . . . . 43
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 48		6.2. TLVs . . . . . . . . . . . . . . . . . . . . . . . . . . 43
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 49		7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 44
	8.1. Normative References . . . . . . . . . . . . . . . . . . 49		8. References . . . . . . . . . . . . . . . . . . . . . . . . . 45
	8.2. Informative References . . . . . . . . . . . . . . . . . 50		8.1. Normative References . . . . . . . . . . . . . . . . . . 45
			8.2. Informative References . . . . . . . . . . . . . . . . . 46
			Appendix A. Deprecated TLVs . . . . . . . . . . . . . . . . . . 47
			A.1. FEC 128 Pseudowire . . . . . . . . . . . . . . . . . . . 47
			A.2. Downstream Mapping(DSMAP) . . . . . . . . . . . . . . . . 48
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 51
	1. Introduction		1. Introduction
	This document describes a simple and efficient mechanism that can be		This document describes a simple and efficient mechanism that can be
	used to detect data plane failures in MPLS Label Switched Paths		used to detect data plane failures in MPLS Label Switched Paths
	(LSPs). There are two parts to this document: information carried in		(LSPs). There are two parts to this document: information carried in
	an MPLS "echo request" and "echo reply", and mechanisms for		an MPLS "echo request" and "echo reply", and mechanisms for
	transporting the echo reply. The first part aims at providing enough		transporting the echo reply. The first part aims at providing enough
	information to check correct operation of the data plane, as well as		information to check correct operation of the data plane, as well as
	skipping to change at page 11, line 34		skipping to change at page 11, line 34
	. .		. .
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Types are defined below; Length is the length of the Value field in		Types are defined below; Length is the length of the Value field in
	octets. The Value field depends on the Type; it is zero padded to		octets. The Value field depends on the Type; it is zero padded to
	align to a 4-octet boundary. TLVs may be nested within other TLVs,		align to a 4-octet boundary. TLVs may be nested within other TLVs,
	in which case the nested TLVs are called sub-TLVs. Sub-TLVs have		in which case the nested TLVs are called sub-TLVs. Sub-TLVs have
	independent types and MUST also be 4-octet aligned.		independent types and MUST also be 4-octet aligned.
	Two examples follow. The Label Distribution Protocol (LDP) IPv4 FEC		Two examples of how TLV and sub-TLV length are computed, and of how
	sub-TLV has the following format:		sub-TLVs are padded to be 4-octet aligned as follows:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type = 1 (LDP IPv4 FEC) | Length = 5 |		| Type = 1 (LDP IPv4 FEC) | Length = 5 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| IPv4 prefix |		| IPv4 prefix |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Prefix Length | Must Be Zero |		| Prefix Length | Must Be Zero |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	skipping to change at page 14, line 5		skipping to change at page 14, line 5
	The Return Subcode contains the point in the label stack where		The Return Subcode contains the point in the label stack where
	processing was terminated. If the RSC is 0, no labels were		processing was terminated. If the RSC is 0, no labels were
	processed. Otherwise the packet would have been label switched at		processed. Otherwise the packet would have been label switched at
	depth RSC.		depth RSC.
	3.2. Target FEC Stack		3.2. Target FEC Stack
	A Target FEC Stack is a list of sub-TLVs. The number of elements is		A Target FEC Stack is a list of sub-TLVs. The number of elements is
	determined by looking at the sub-TLV length fields.		determined by looking at the sub-TLV length fields.
	Sub-Type Length Value Field		Sub-Type Length Value Field
	-------- ------ -----------		-------- ------ -----------
	1 5 LDP IPv4 prefix		1 5 LDP IPv4 prefix
	2 17 LDP IPv6 prefix		2 17 LDP IPv6 prefix
	3 20 RSVP IPv4 LSP		3 20 RSVP IPv4 LSP
	4 56 RSVP IPv6 LSP		4 56 RSVP IPv6 LSP
	5 Not Assigned		5 Not Assigned
	6 13 VPN IPv4 prefix		6 13 VPN IPv4 prefix
	7 25 VPN IPv6 prefix		7 25 VPN IPv6 prefix
	8 14 L2 VPN endpoint		8 14 L2 VPN endpoint
	9 10 "FEC 128" Pseudowire - IPv4 (deprecated)		9 10 "FEC 128" Pseudowire - IPv4 (deprecated)
	10 14 "FEC 128" Pseudowire - IPv4		10 14 "FEC 128" Pseudowire - IPv4
	11 16+ "FEC 129" Pseudowire - IPv4		11 16+ "FEC 129" Pseudowire - IPv4
	12 5 BGP labeled IPv4 prefix		12 5 BGP labeled IPv4 prefix
	13 17 BGP labeled IPv6 prefix		13 17 BGP labeled IPv6 prefix
	14 5 Generic IPv4 prefix		14 5 Generic IPv4 prefix
	15 17 Generic IPv6 prefix		15 17 Generic IPv6 prefix
	16 4 Nil FEC		16 4 Nil FEC
	24 38 "FEC 128" Pseudowire - IPv6		24 38 "FEC 128" Pseudowire - IPv6
	25 40+ "FEC 129" Pseudowire - IPv6		25 40+ "FEC 129" Pseudowire - IPv6
	Other FEC Types will be defined as needed.		Other FEC Types will be defined as needed.
	Note that this TLV defines a stack of FECs, the first FEC element		Note that this TLV defines a stack of FECs, the first FEC element
	corresponding to the top of the label stack, etc.		corresponding to the top of the label stack, etc.
	An MPLS echo request MUST have a Target FEC Stack that describes the		An MPLS echo request MUST have a Target FEC Stack that describes the
	FEC Stack being tested. For example, if an LSR X has an LDP mapping		FEC Stack being tested. For example, if an LSR X has an LDP mapping
	[RFC5036] for 192.168.1.1 (say, label 1001), then to verify that		[RFC5036] for 192.168.1.1 (say, label 1001), then to verify that
	label 1001 does indeed reach an egress LSR that announced this prefix		label 1001 does indeed reach an egress LSR that announced this prefix
	via LDP, X can send an MPLS echo request with an FEC Stack TLV with		via LDP, X can send an MPLS echo request with an FEC Stack TLV with
	one FEC in it, namely, of type LDP IPv4 prefix, with prefix		one FEC in it, namely, of type LDP IPv4 prefix, with prefix
	192.168.1.1/32, and send the echo request with a label of 1001.		192.168.1.1/32, and send the echo request with a label of 1001.
	Say LSR X wanted to verify that a label stack of <1001, 23456> is the		Say LSR X wanted to verify that a label stack of <1001, 23456> is the
	right label stack to use to reach a VPN IPv4 prefix [see section		right label stack to use to reach a VPN IPv4 prefix [see
	3.2.5] of 10/8 in VPN foo. Say further that LSR Y with loopback		Section 3.2.5] of 10/8 in VPN foo. Say further that LSR Y with
	address 192.168.1.1 announced prefix 10/8 with Route Distinguisher		loopback address 192.168.1.1 announced prefix 10/8 with Route
	RD-foo-Y (which may in general be different from the Route		Distinguisher RD-foo-Y (which may in general be different from the
	Distinguisher that LSR X uses in its own advertisements for VPN foo),		Route Distinguisher that LSR X uses in its own advertisements for VPN
	label 23456 and BGP next hop 192.168.1.1 [RFC4271]. Finally, suppose		foo), label 23456 and BGP next hop 192.168.1.1 [RFC4271]. Finally,
	that LSR X receives a label binding of 1001 for 192.168.1.1 via LDP.		suppose that LSR X receives a label binding of 1001 for 192.168.1.1
	X has two choices in sending an MPLS echo request: X can send an MPLS		via LDP. X has two choices in sending an MPLS echo request: X can
	echo request with an FEC Stack TLV with a single FEC of type VPN IPv4		send an MPLS echo request with an FEC Stack TLV with a single FEC of
	prefix with a prefix of 10/8 and a Route Distinguisher of RD-foo-Y.		type VPN IPv4 prefix with a prefix of 10/8 and a Route Distinguisher
	Alternatively, X can send an FEC Stack TLV with two FECs, the first		of RD-foo-Y. Alternatively, X can send an FEC Stack TLV with two
	of type LDP IPv4 with a prefix of 192.168.1.1/32 and the second of		FECs, the first of type LDP IPv4 with a prefix of 192.168.1.1/32 and
	type of IP VPN with a prefix 10/8 with Route Distinguisher of RD-foo-		the second of type of IP VPN with a prefix 10/8 with Route
	Y. In either case, the MPLS echo request would have a label stack of		Distinguisher of RD-foo-Y. In either case, the MPLS echo request
	<1001, 23456>. (Note: in this example, 1001 is the "outer" label and		would have a label stack of <1001, 23456>. (Note: in this example,
	23456 is the "inner" label.)		1001 is the "outer" label and 23456 is the "inner" label.)
	3.2.1. LDP IPv4 Prefix		3.2.1. LDP IPv4 Prefix
	The IPv4 Prefix FEC is defined in [RFC5036]. When an LDP IPv4 prefix		The IPv4 Prefix FEC is defined in [RFC5036]. When an LDP IPv4 prefix
	is encoded in a label stack, the following format is used. The value		is encoded in a label stack, the following format is used. The value
	consists of 4 octets of an IPv4 prefix followed by 1 octet of prefix		consists of 4 octets of an IPv4 prefix followed by 1 octet of prefix
	length in bits; the format is given below. The IPv4 prefix is in		length in bits; the format is given below. The IPv4 prefix is in
	network byte order; if the prefix is shorter than 32 bits, trailing		network byte order; if the prefix is shorter than 32 bits, trailing
	bits SHOULD be set to zero. See [RFC5036] for an example of a		bits SHOULD be set to zero. See [RFC5036] for an example of a
	Mapping for an IPv4 FEC.		Mapping for an IPv4 FEC.
	skipping to change at page 18, line 7		skipping to change at page 18, line 7
	| IPv6 prefix |		| IPv6 prefix |
	| |		| |
	| |		| |
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Prefix Length | Must Be Zero |		| Prefix Length | Must Be Zero |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	The Route Distinguisher is identical to the VPN IPv4 Prefix RD,		The Route Distinguisher is identical to the VPN IPv4 Prefix RD,
	except that it functions here to allow the creation of distinct		except that it functions here to allow the creation of distinct
	routes to IPv6 prefixes. See section 3.2.5. When matching this		routes to IPv6 prefixes. See Section 3.2.5. When matching this
	field to local FEC information, it is treated as an opaque value.		field to local FEC information, it is treated as an opaque value.
	3.2.7. L2 VPN Endpoint		3.2.7. L2 VPN Endpoint
	VPLS stands for Virtual Private LAN Service. The terms VPLS BGP NLRI		VPLS stands for Virtual Private LAN Service. The terms VPLS BGP NLRI
	and VE ID (VPLS Edge Identifier) are defined in [RFC4761]. This		and VE ID (VPLS Edge Identifier) are defined in [RFC4761]. This
	document uses the simpler term L2 VPN endpoint when referring to a		document uses the simpler term L2 VPN endpoint when referring to a
	VPLS BGP NLRI. The Route Distinguisher is an 8-octet identifier used		VPLS BGP NLRI. The Route Distinguisher is an 8-octet identifier used
	to distinguish information about various L2 VPNs advertised by a		to distinguish information about various L2 VPNs advertised by a
	node. The VE ID is a 2-octet identifier used to identify a		node. The VE ID is a 2-octet identifier used to identify a
	skipping to change at page 18, line 43		skipping to change at page 18, line 43
	| Route Distinguisher |		| Route Distinguisher |
	| (8 octets) |		| (8 octets) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Sender's VE ID | Receiver's VE ID |		| Sender's VE ID | Receiver's VE ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Encapsulation Type | Must Be Zero |		| Encapsulation Type | Must Be Zero |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	3.2.8. FEC 128 Pseudowire - IPv4 (Deprecated)		3.2.8. FEC 128 Pseudowire - IPv4 (Deprecated)
	FEC 128 (0x80) is defined in [RFC4447], as are the terms PW ID		See Appendix A.1 for details
	(Pseudowire ID) and PW Type (Pseudowire Type). A PW ID is a non-zero
	32-bit connection ID. The PW Type is a 15-bit number indicating the
	encapsulation type. It is carried right justified in the field below
	termed encapsulation type with the high-order bit set to zero. Both
	of these fields are treated in this protocol as opaque values.
	When an FEC 128 is encoded in a label stack, the following format is
	used. The value field consists of the remote PE IPv4 address (the
	destination address of the targeted LDP session), the PW ID, and the
	encapsulation type as follows:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Remote PE IPv4 Address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| PW ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| PW Type | Must Be Zero |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	This FEC is deprecated and is retained only for backward
	compatibility. Implementations of LSP ping SHOULD accept and process
	this TLV, but SHOULD send LSP ping echo requests with the new TLV
	(see next section), unless explicitly configured to use the old TLV.
	An LSR receiving this TLV SHOULD use the source IP address of the LSP
	echo request to infer the sender's PE address.
	3.2.9. FEC 128 Pseudowire - IPv4 (Current)		3.2.9. FEC 128 Pseudowire - IPv4 (Current)
	FEC 128 (0x80) is defined in [RFC4447], as are the terms PW ID		FEC 128 (0x80) is defined in [RFC4447], as are the terms PW ID
	(Pseudowire ID) and PW Type (Pseudowire Type). A PW ID is a non-zero		(Pseudowire ID) and PW Type (Pseudowire Type). A PW ID is a non-zero
	32-bit connection ID. The PW Type is a 15-bit number indicating the		32-bit connection ID. The PW Type is a 15-bit number indicating the
	encapsulation type. It is carried right justified in the field below		encapsulation type. It is carried right justified in the field below
	termed encapsulation type with the high-order bit set to zero.		termed encapsulation type with the high-order bit set to zero.
	Both of these fields are treated in this protocol as opaque values.		Both of these fields are treated in this protocol as opaque values.
	skipping to change at page 25, line 5		skipping to change at page 24, line 5
	Sender's PE IPv6 Address: The source IP address of the target IPv6		Sender's PE IPv6 Address: The source IP address of the target IPv6
	LDP session. 16 octets.		LDP session. 16 octets.
	Remote PE IPv6 Address: The destination IP address of the target IPv6		Remote PE IPv6 Address: The destination IP address of the target IPv6
	LDP session. 16 octets.		LDP session. 16 octets.
	The other fields are the same as FEC 129 Pseudowire IPv4 in		The other fields are the same as FEC 129 Pseudowire IPv4 in
	Section 3.2.10.		Section 3.2.10.
	3.3. Downstream Mapping		3.3. Downstream Mapping (Deprecated)
	The Downstream Mapping object is a TLV that MAY be included in an
	echo request message. Only one Downstream Mapping object may appear
	in an echo request. The presence of a Downstream Mapping object is a
	request that Downstream Mapping objects be included in the echo
	reply. If the replying router is the destination of the FEC, then a
	Downstream Mapping TLV SHOULD NOT be included in the echo reply.
	Otherwise the replying router SHOULD include a Downstream Mapping
	object for each interface over which this FEC could be forwarded.
	For a more precise definition of the notion of "downstream", see
	section 3.3.2, "Downstream Router and Interface".
	The Length is K + M + 4*N octets, where M is the Multipath Length,
	and N is the number of Downstream Labels. Values for K are found in
	the description of Address Type below. The Value field of a
	Downstream Mapping has the following format:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| MTU | Address Type | DS Flags |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Downstream IP Address (4 or 16 octets) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Downstream Interface Address (4 or 16 octets) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Multipath Type| Depth Limit | Multipath Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	. .
	. (Multipath Information) .
	. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Downstream Label | Protocol |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	. .
	. .
	. .
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Downstream Label | Protocol |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Maximum Transmission Unit (MTU)
	The MTU is the size in octets of the largest MPLS frame (including
	label stack) that fits on the interface to the Downstream LSR.
	Address Type
	The Address Type indicates if the interface is numbered or
	unnumbered. It also determines the length of the Downstream IP
	Address and Downstream Interface fields. The resulting total for
	the initial part of the TLV is listed in the table below as "K
	Octets". The Address Type is set to one of the following values:
	Type # Address Type K Octets
	------ ------------ --------
	1 IPv4 Numbered 16
	2 IPv4 Unnumbered 16
	3 IPv6 Numbered 40
	4 IPv6 Unnumbered 28
	DS Flags
	The DS Flags field is a bit vector with the following format:
	0 1 2 3 4 5 6 7
	+-+-+-+-+-+-+-+-+
	| Rsvd(MBZ) |I|N|
	+-+-+-+-+-+-+-+-+
	Two flags are defined currently, I and N. The remaining flags MUST
	be set to zero when sending and ignored on receipt.
	Flag Name and Meaning
	---- ----------------
	I Interface and Label Stack Object Request
	When this flag is set, it indicates that the replying
	router SHOULD include an Interface and Label Stack
	Object in the echo reply message.
	N Treat as a Non-IP Packet
	Echo request messages will be used to diagnose non-IP
	flows. However, these messages are carried in IP
	packets. For a router that alters its ECMP algorithm
	based on the FEC or deep packet examination, this flag
	requests that the router treat this as it would if the
	determination of an IP payload had failed.
	Downstream IP Address and Downstream Interface Address
	IPv4 addresses and interface indices are encoded in 4 octets; IPv6
	addresses are encoded in 16 octets.
	If the interface to the downstream LSR is numbered, then the
	Address Type MUST be set to IPv4 or IPv6, the Downstream IP
	Address MUST be set to either the downstream LSR's Router ID or
	the interface address of the downstream LSR, and the Downstream
	Interface Address MUST be set to the downstream LSR's interface
	address.
	If the interface to the downstream LSR is unnumbered, the Address
	Type MUST be IPv4 Unnumbered or IPv6 Unnumbered, the Downstream IP
	Address MUST be the downstream LSR's Router ID, and the Downstream
	Interface Address MUST be set to the index assigned by the
	upstream LSR to the interface.
	If an LSR does not know the IP address of its neighbor, then it
	MUST set the Address Type to either IPv4 Unnumbered or IPv6
	Unnumbered. For IPv4, it must set the Downstream IP Address to
	127.0.0.1; for IPv6 the address is set to 0::1. In both cases,
	the interface index MUST be set to 0. If an LSR receives an Echo
	Request packet with either of these addresses in the Downstream IP
	Address field, this indicates that it MUST bypass interface
	verification but continue with label validation.
	If the originator of an Echo Request packet wishes to obtain
	Downstream Mapping information but does not know the expected
	label stack, then it SHOULD set the Address Type to either IPv4
	Unnumbered or IPv6 Unnumbered. For IPv4, it MUST set the
	Downstream IP Address to 224.0.0.2; for IPv6 the address MUST be
	set to FF02::2. In both cases, the interface index MUST be set to
	0. If an LSR receives an Echo Request packet with the all-routers
	multicast address, then this indicates that it MUST bypass both
	interface and label stack validation, but return Downstream
	Mapping TLVs using the information provided.
	Multipath Type
	The following Multipath Types are defined:
	Key Type Multipath Information
	--- ---------------- ---------------------
	0 no multipath Empty (Multipath Length = 0)
	2 IP address IP addresses
	4 IP address range low/high address pairs
	8 Bit-masked IP IP address prefix and bit mask
	address set
	9 Bit-masked label set Label prefix and bit mask
	Type 0 indicates that all packets will be forwarded out this one
	interface.
	Types 2, 4, 8, and 9 specify that the supplied Multipath
	Information will serve to exercise this path.
	Depth Limit
	The Depth Limit is applicable only to a label stack and is the
	maximum number of labels considered in the hash; this SHOULD be
	set to zero if unspecified or unlimited.
	Multipath Length
	The length in octets of the Multipath Information.
	Multipath Information
	Address or label values encoded according to the Multipath Type.
	See the next section below for encoding details.
	Downstream Label(s)
	The set of labels in the label stack as it would have appeared if
	this router were forwarding the packet through this interface.
	Any Implicit Null labels are explicitly included. Labels are
	treated as numbers, i.e., they are right justified in the field.
	A Downstream Label is 24 bits, in the same format as an MPLS label		See Appendix A.2 for more details.
	minus the TTL field, i.e., the MSBit of the label is bit 0, the
	LSBit is bit 19, the Traffic Class (TC) bits are bits 20-22, and
	bit 23 is the S bit. The replying router SHOULD fill in the TC
	and S bits; the LSR receiving the echo reply MAY choose to ignore
	these bits. Protocol
	The Protocol is taken from the following table:		3.4. Downstream Detailed Mapping
	Protocol # Signaling Protocol		The format of this TLV is defined in section 3.3 of [RFC6424]
	---------- ------------------
	0 Unknown
	1 Static
	2 BGP
	3 LDP
	4 RSVP-TE
	3.3.1. Multipath Information Encoding		3.4.1. Multipath Information Encoding
	The Multipath Information encodes labels or addresses that will		The Multipath Information encodes labels or addresses that will
	exercise this path. The Multipath Information depends on the		exercise this path. The Multipath Information depends on the
	Multipath Type. The contents of the field are shown in the table		Multipath Type. The contents of the field are shown in the table
	above. IPv4 addresses are drawn from the range 127/8; IPv6 addresses		above. IPv4 addresses are drawn from the range 127/8; IPv6 addresses
	are drawn from the range 0:0:0:0:0:FFFF:7F00/104. Labels are treated		are drawn from the range 0:0:0:0:0:FFFF:7F00/104. Labels are treated
	as numbers, i.e., they are right justified in the field. For Type 4,		as numbers, i.e., they are right justified in the field. For Type 4,
	ranges indicated by Address pairs MUST NOT overlap and MUST be in		ranges indicated by Address pairs MUST NOT overlap and MUST be in
	ascending sequence.		ascending sequence.
	skipping to change at page 30, line 35		skipping to change at page 26, line 8
	Multipath Information is null (i.e., Multipath Length = 0, or for		Multipath Information is null (i.e., Multipath Length = 0, or for
	Types 8 and 9, a mask of all zeros), the type MUST be set to 0.		Types 8 and 9, a mask of all zeros), the type MUST be set to 0.
	For example, suppose LSR X at hop 10 has two downstream LSRs, Y and		For example, suppose LSR X at hop 10 has two downstream LSRs, Y and
	Z, for the FEC in question. The received X could return Multipath		Z, for the FEC in question. The received X could return Multipath
	Type 4, with low/high IP addresses of 127.1.1.1->127.1.1.255 for		Type 4, with low/high IP addresses of 127.1.1.1->127.1.1.255 for
	downstream LSR Y and 127.2.1.1->127.2.1.255 for downstream LSR Z.		downstream LSR Y and 127.2.1.1->127.2.1.255 for downstream LSR Z.
	The head end reflects this information to LSR Y. Y, which has three		The head end reflects this information to LSR Y. Y, which has three
	downstream LSRs, U, V, and W, computes that 127.1.1.1->127.1.1.127		downstream LSRs, U, V, and W, computes that 127.1.1.1->127.1.1.127
	would go to U and 127.1.1.128-> 127.1.1.255 would go to V. Y would		would go to U and 127.1.1.128-> 127.1.1.255 would go to V. Y would
	then respond with 3 Downstream Mappings: to U, with Multipath Type 4		then respond with 3 "Downstream Detailed Mapping" TLVs: to U, with
	(127.1.1.1->127.1.1.127); to V, with Multipath Type 4		Multipath Type 4 (127.1.1.1->127.1.1.127); to V, with Multipath Type
	(127.1.1.127->127.1.1.255); and to W, with Multipath Type 0.		4 (127.1.1.127->127.1.1.255); and to W, with Multipath Type 0.
	Note that computing Multipath Information may impose a significant		Note that computing Multipath Information may impose a significant
	processing burden on the receiver. A receiver MAY thus choose to		processing burden on the receiver. A receiver MAY thus choose to
	process a subset of the received prefixes. The sender, on receiving		process a subset of the received prefixes. The sender, on receiving
	a reply to a Downstream Mapping with partial information, SHOULD		a reply to a Downstream Detailed Mapping with partial information,
	assume that the prefixes missing in the reply were skipped by the		SHOULD assume that the prefixes missing in the reply were skipped by
	receiver, and MAY re-request information about them in a new echo		the receiver, and MAY re-request information about them in a new echo
	request.		request.
	3.3.2. Downstream Router and Interface		The encoding of Multipath information in scenarios where few LSRs
			apply Entropy label based load balancing while other LSRs are non-EL
			(IP based) load balancing will be defined in a different document.
			The encoding of multipath information in scenarios where LSR have
			Layer 2 ECMP over Link Aggregation Group (LAG) interfaces will be
			defined in different document.
			3.4.2. Downstream Router and Interface
	The notion of "downstream router" and "downstream interface" should		The notion of "downstream router" and "downstream interface" should
	be explained. Consider an LSR X. If a packet that was originated		be explained. Consider an LSR X. If a packet that was originated
	with TTL n>1 arrived with outermost label L and TTL=1 at LSR X, X		with TTL n>1 arrived with outermost label L and TTL=1 at LSR X, X
	must be able to compute which LSRs could receive the packet if it was		must be able to compute which LSRs could receive the packet if it was
	originated with TTL=n+1, over which interface the request would		originated with TTL=n+1, over which interface the request would
	arrive and what label stack those LSRs would see. (It is outside the		arrive and what label stack those LSRs would see. (It is outside the
	scope of this document to specify how this computation is done.) The		scope of this document to specify how this computation is done.) The
	set of these LSRs/interfaces consists of the downstream routers/		set of these LSRs/interfaces consists of the downstream routers/
	interfaces (and their corresponding labels) for X with respect to L.		interfaces (and their corresponding labels) for X with respect to L.
	Each pair of downstream router and interface requires a separate		Each pair of downstream router and interface requires a separate
	Downstream Mapping to be added to the reply.		Downstream Detailed Mapping to be added to the reply.
	The case where X is the LSR originating the echo request is a special		The case where X is the LSR originating the echo request is a special
	case. X needs to figure out what LSRs would receive the MPLS echo		case. X needs to figure out what LSRs would receive the MPLS echo
	request for a given FEC Stack that X originates with TTL=1.		request for a given FEC Stack that X originates with TTL=1.
	The set of downstream routers at X may be alternative paths (see the		The set of downstream routers at X may be alternative paths (see the
	discussion below on ECMP) or simultaneous paths (e.g., for MPLS		discussion below on ECMP) or simultaneous paths (e.g., for MPLS
	multicast). In the former case, the Multipath Information is used as		multicast). In the former case, the Multipath Information is used as
	a hint to the sender as to how it may influence the choice of these		a hint to the sender as to how it may influence the choice of these
	alternatives.		alternatives.
	3.4. Pad TLV		3.5. Pad TLV
	The value part of the Pad TLV contains a variable number (>= 1) of		The value part of the Pad TLV contains a variable number (>= 1) of
	octets. The first octet takes values from the following table; all		octets. The first octet takes values from the following table; all
	the other octets (if any) are ignored. The receiver SHOULD verify		the other octets (if any) are ignored. The receiver SHOULD verify
	that the TLV is received in its entirety, but otherwise ignores the		that the TLV is received in its entirety, but otherwise ignores the
	contents of this TLV, apart from the first octet.		contents of this TLV, apart from the first octet.
	Value Meaning		Value Meaning
	----- -------		----- -------
	1 Drop Pad TLV from reply		1 Drop Pad TLV from reply
	2 Copy Pad TLV to reply		2 Copy Pad TLV to reply
	3-255 Reserved for future use		3-255 Reserved for future use
	3.5. Vendor Enterprise Number		3.6. Vendor Enterprise Number
	SMI Private Enterprise Numbers are maintained by IANA. The Length is		SMI Private Enterprise Numbers are maintained by IANA. The Length is
	always 4; the value is the SMI Private Enterprise code, in network		always 4; the value is the SMI Private Enterprise code, in network
	octet order, of the vendor with a Vendor Private extension to any of		octet order, of the vendor with a Vendor Private extension to any of
	the fields in the fixed part of the message, in which case this TLV		the fields in the fixed part of the message, in which case this TLV
	MUST be present. If none of the fields in the fixed part of the		MUST be present. If none of the fields in the fixed part of the
	message have Vendor Private extensions, inclusion of this TLV is		message have Vendor Private extensions, inclusion of this TLV is
	OPTIONAL. Vendor Private ranges for Message Types, Reply Modes, and		OPTIONAL. Vendor Private ranges for Message Types, Reply Modes, and
	Return Codes have been defined. When any of these are used, the		Return Codes have been defined. When any of these are used, the
	Vendor Enterprise Number TLV MUST be included in the message.		Vendor Enterprise Number TLV MUST be included in the message.
	3.6. Interface and Label Stack		3.7. Interface and Label Stack
	The Interface and Label Stack TLV MAY be included in a reply message		The Interface and Label Stack TLV MAY be included in a reply message
	to report the interface on which the request message was received and		to report the interface on which the request message was received and
	the label stack that was on the packet when it was received. Only		the label stack that was on the packet when it was received. Only
	one such object may appear. The purpose of the object is to allow		one such object may appear. The purpose of the object is to allow
	the upstream router to obtain the exact interface and label stack		the upstream router to obtain the exact interface and label stack
	information as it appears at the replying LSR.		information as it appears at the replying LSR.
	The Length is K + 4*N octets; N is the number of labels in the label		The Length is K + 4*N octets; N is the number of labels in the label
	stack. Values for K are found in the description of Address Type		stack. Values for K are found in the description of Address Type
	below. The Value field of a Downstream Mapping has the following		below. The Value field of this TLV has the following format:
	format:
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Address Type | Must Be Zero |		| Address Type | Must Be Zero |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| IP Address (4 or 16 octets) |		| IP Address (4 or 16 octets) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Interface (4 or 16 octets) |		| Interface (4 or 16 octets) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	skipping to change at page 33, line 23		skipping to change at page 29, line 10
	If the interface is unnumbered, the Address Type MUST be either		If the interface is unnumbered, the Address Type MUST be either
	IPv4 Unnumbered or IPv6 Unnumbered, the IP Address MUST be the		IPv4 Unnumbered or IPv6 Unnumbered, the IP Address MUST be the
	LSR's Router ID, and the Interface MUST be set to the index		LSR's Router ID, and the Interface MUST be set to the index
	assigned to the interface.		assigned to the interface.
	Label Stack		Label Stack
	The label stack of the received echo request message. If any TTL		The label stack of the received echo request message. If any TTL
	values have been changed by this router, they SHOULD be restored.		values have been changed by this router, they SHOULD be restored.
	3.7. Errored TLVs		3.8. Errored TLVs
	The following TLV is a TLV that MAY be included in an echo reply to		The following TLV is a TLV that MAY be included in an echo reply to
	inform the sender of an echo request of mandatory TLVs either not		inform the sender of an echo request of mandatory TLVs either not
	supported by an implementation or parsed and found to be in error.		supported by an implementation or parsed and found to be in error.
	The Value field contains the TLVs that were not understood, encoded		The Value field contains the TLVs that were not understood, encoded
	as sub-TLVs.		as sub-TLVs.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Type = 9 | Length |		| Type = 9 | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Value |		| Value |
	. .		. .
	. .		. .
	. .		. .
	| |		| |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	3.8. Reply TOS Byte TLV		3.9. Reply TOS Byte TLV
	This TLV MAY be used by the originator of the echo request to request		This TLV MAY be used by the originator of the echo request to request
	that an echo reply be sent with the IP header TOS byte set to the		that an echo reply be sent with the IP header TOS byte set to the
	value specified in the TLV. This TLV has a length of 4 with the		value specified in the TLV. This TLV has a length of 4 with the
	following value field.		following value field.
	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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+		+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Reply-TOS Byte| Must Be Zero |		| Reply-TOS Byte| Must Be Zero |
	skipping to change at page 35, line 12		skipping to change at page 30, line 45
	Since the actual LSP and path that a given packet may take may not be		Since the actual LSP and path that a given packet may take may not be
	known a priori, it is useful if MPLS echo requests can exercise all		known a priori, it is useful if MPLS echo requests can exercise all
	possible paths. This, although desirable, may not be practical,		possible paths. This, although desirable, may not be practical,
	because the algorithms that a given LSR uses to distribute packets		because the algorithms that a given LSR uses to distribute packets
	over alternative paths may be proprietary.		over alternative paths may be proprietary.
	To achieve some degree of coverage of alternate paths, there is a		To achieve some degree of coverage of alternate paths, there is a
	certain latitude in choosing the destination IP address and source		certain latitude in choosing the destination IP address and source
	UDP port for an MPLS echo request. This is clearly not sufficient;		UDP port for an MPLS echo request. This is clearly not sufficient;
	in the case of traceroute, more latitude is offered by means of the		in the case of traceroute, more latitude is offered by means of the
	Multipath Information of the Downstream Mapping TLV. This is used as		Multipath Information of the Downstream Detailed Mapping TLV. This
	follows. An ingress LSR periodically sends an MPLS traceroute		is used as follows. An ingress LSR periodically sends an MPLS
	message to determine whether there are multipaths for a given LSP.		traceroute message to determine whether there are multipaths for a
	If so, each hop will provide some information how each of its		given LSP. If so, each hop will provide some information how each of
	downstream paths can be exercised. The ingress can then send MPLS		its downstream paths can be exercised. The ingress can then send
	echo requests that exercise these paths. If several transit LSRs		MPLS echo requests that exercise these paths. If several transit
	have ECMP, the ingress may attempt to compose these to exercise all		LSRs have ECMP, the ingress may attempt to compose these to exercise
	possible paths. However, full coverage may not be possible.		all possible paths. However, full coverage may not be possible.
	4.2. Testing LSPs That Are Used to Carry MPLS Payloads		4.2. Testing LSPs That Are Used to Carry MPLS Payloads
	To detect certain LSP breakages, it may be necessary to encapsulate		To detect certain LSP breakages, it may be necessary to encapsulate
	an MPLS echo request packet with at least one additional label when		an MPLS echo request packet with at least one additional label when
	testing LSPs that are used to carry MPLS payloads (such as LSPs used		testing LSPs that are used to carry MPLS payloads (such as LSPs used
	to carry L2VPN and L3VPN traffic. For example, when testing LDP or		to carry L2VPN and L3VPN traffic. For example, when testing LDP or
	RSVP-TE LSPs, just sending an MPLS echo request packet may not detect		RSVP-TE LSPs, just sending an MPLS echo request packet may not detect
	instances where the router immediately upstream of the destination of		instances where the router immediately upstream of the destination of
	the LSP ping may forward the MPLS echo request successfully over an		the LSP ping may forward the MPLS echo request successfully over an
	skipping to change at page 36, line 36		skipping to change at page 32, line 21
	the Sequence Number by 1. However, a sender MAY choose to send a		the Sequence Number by 1. However, a sender MAY choose to send a
	group of echo requests with the same Sequence Number to improve the		group of echo requests with the same Sequence Number to improve the
	chance of arrival of at least one packet with that Sequence Number.		chance of arrival of at least one packet with that Sequence Number.
	The TimeStamp Sent is set to the time-of-day in NTP format that the		The TimeStamp Sent is set to the time-of-day in NTP format that the
	echo request is sent. The TimeStamp Received is set to zero.		echo request is sent. The TimeStamp Received is set to zero.
	An MPLS echo request MUST have an FEC Stack TLV. Also, the Reply		An MPLS echo request MUST have an FEC Stack TLV. Also, the Reply
	Mode must be set to the desired reply mode; the Return Code and		Mode must be set to the desired reply mode; the Return Code and
	Subcode are set to zero. In the "traceroute" mode, the echo request		Subcode are set to zero. In the "traceroute" mode, the echo request
	SHOULD include a Downstream Mapping TLV.		SHOULD include a Downstream Detailed Mapping TLV.
	4.4. Receiving an MPLS Echo Request		4.4. Receiving an MPLS Echo Request
	Sending an MPLS echo request to the control plane is triggered by one		Sending an MPLS echo request to the control plane is triggered by one
	of the following packet processing exceptions: Router Alert option,		of the following packet processing exceptions: Router Alert option,
	IP TTL expiration, MPLS TTL expiration, MPLS Router Alert label, or		IP TTL expiration, MPLS TTL expiration, MPLS Router Alert label, or
	the destination address in the 127/8 address range. The control		the destination address in the 127/8 address range. The control
	plane further identifies it by UDP destination port 3503.		plane further identifies it by UDP destination port 3503.
	For reporting purposes the bottom of stack is considered to be stack-		For reporting purposes the bottom of stack is considered to be stack-
	skipping to change at page 37, line 31		skipping to change at page 33, line 14
	Handle, Sequence Number, and Timestamp Sent are not examined, but		Handle, Sequence Number, and Timestamp Sent are not examined, but
	are included in the MPLS echo reply message.		are included in the MPLS echo reply message.
	The algorithm uses the following variables and identifiers:		The algorithm uses the following variables and identifiers:
	Interface-I: the interface on which the MPLS echo request was		Interface-I: the interface on which the MPLS echo request was
	received.		received.
	Stack-R: the label stack on the packet as it was received.		Stack-R: the label stack on the packet as it was received.
	Stack-D: the label stack carried in the Downstream Mapping		Stack-D: the label stack carried in the "Label Stack sub-
	TLV (not always present)		TLV" in Downstream Detailed Mapping TLV (not
			always present)
	Label-L: the label from the actual stack currently being		Label-L: the label from the actual stack currently being
	examined. Requires no initialization.		examined. Requires no initialization.
	Label-stack-depth: the depth of label being verified. Initialized		Label-stack-depth: the depth of label being verified. Initialized
	to the number of labels in the received label		to the number of labels in the received label
	stack S.		stack S.
	FEC-stack-depth: depth of the FEC in the Target FEC Stack that		FEC-stack-depth: depth of the FEC in the Target FEC Stack that
	should be used to verify the current actual		should be used to verify the current actual
	skipping to change at page 39, line 29		skipping to change at page 35, line 16
	}		}
	If the label operation is "Swap or Pop and Switch based on Popped		If the label operation is "Swap or Pop and Switch based on Popped
	Label" {		Label" {
	Set Best-return-code to 8 ("Label switched at stack-depth") and		Set Best-return-code to 8 ("Label switched at stack-depth") and
	Best-rtn-subcode to Label-stack-depth to report transit		Best-rtn-subcode to Label-stack-depth to report transit
	switching.		switching.
	If a Downstream Mapping TLV is present in the received echo		If a Downstream Detailed Mapping TLV is present in the received
	request {		echo request {
	If the IP address in the TLV is 127.0.0.1 or 0::1 {		If the IP address in the TLV is 127.0.0.1 or 0::1 {
	Set Best-return-code to 6 ("Upstream Interface Index		Set Best-return-code to 6 ("Upstream Interface Index
	Unknown"). An Interface and Label Stack TLV SHOULD be		Unknown"). An Interface and Label Stack TLV SHOULD be
	included in the reply and filled with Interface-I and		included in the reply and filled with Interface-I and
	Stack-R.		Stack-R.
	}		}
	Else {		Else {
	Verify that the IP address, interface address, and label		Verify that the IP address, interface address, and label
	stack in the Downstream Mapping TLV match Interface-I and		stack in the Downstream Detailed Mapping TLV match
	Stack-R. If there is a mismatch, set Best-return-code to		Interface-I and Stack-R. If there is a mismatch, set
	5, "Downstream Mapping Mismatch". An Interface and Label		Best-return-code to 5, "Downstream Mapping Mismatch". An
	Stack TLV SHOULD be included in the reply and filled in		Interface and Label Stack TLV SHOULD be included in the
	based on Interface-I and Stack-R. Go to step 7 (Send		reply and filled in based on Interface-I and Stack-R. Go
	Reply Packet).		to step 7 (Send Reply Packet).
	}		}
	}		}
	For each available downstream ECMP path {		For each available downstream ECMP path {
	Retrieve output interface from the NHLFE entry.		Retrieve output interface from the NHLFE entry.
	/* Note: this return code is set even if Label-stack-depth		/* Note: this return code is set even if Label-stack-depth
	skipping to change at page 40, line 15		skipping to change at page 36, line 4
	}		}
	For each available downstream ECMP path {		For each available downstream ECMP path {
	Retrieve output interface from the NHLFE entry.		Retrieve output interface from the NHLFE entry.
	/* Note: this return code is set even if Label-stack-depth		/* Note: this return code is set even if Label-stack-depth
	is one */		is one */
	If the output interface is not MPLS enabled {		If the output interface is not MPLS enabled {
	Set Best-return-code to Return Code 9, "Label switched		Set Best-return-code to Return Code 9, "Label switched
	but no MPLS forwarding at stack-depth" and set Best-rtn-		but no MPLS forwarding at stack-depth" and set Best-rtn-
	subcode to Label-stack-depth and goto Send_Reply_Packet.		subcode to Label-stack-depth and goto Send_Reply_Packet.
	}		}
	If a Downstream Mapping TLV is present {		If a Downstream Detailed Mapping TLV is present {
	A Downstream Mapping TLV SHOULD be included in the echo		A Downstream Detailed Mapping TLV SHOULD be included in
	reply (see section 3.3) filled in with information about		the echo reply (see Section 3.4) filled in with
	the current ECMP path.		information about the current ECMP path.
	}		}
	}		}
	If no Downstream Mapping TLV is present, or the Downstream IP		If no Downstream Detailed Mapping TLV is present, or the
	Address is set to the ALLROUTERS multicast address, go to step		Downstream IP Address is set to the ALLROUTERS multicast
	7 (Send Reply Packet).		address, go to step 7 (Send Reply Packet).
	If the "Validate FEC Stack" flag is not set and the LSR is not		If the "Validate FEC Stack" flag is not set and the LSR is not
	configured to perform FEC checking by default, go to step 7		configured to perform FEC checking by default, go to step 7
	(Send Reply Packet).		(Send Reply Packet).
	/* Validate the Target FEC Stack in the received echo request.		/* Validate the Target FEC Stack in the received echo request.
	First determine FEC-stack-depth from the Downstream Mapping		First determine FEC-stack-depth from the Downstream Detailed
	TLV. This is done by walking through Stack-D (the Downstream		Mapping TLV. This is done by walking through Stack-D (the
	labels) from the bottom, decrementing the number of labels for		Downstream labels) from the bottom, decrementing the number of
	each non-Implicit Null label, while incrementing FEC-stack-		labels for each non-Implicit Null label, while incrementing
	depth for each label. If the Downstream Mapping TLV contains		FEC-stack-depth for each label. If the Downstream Detailed
	one or more Implicit Null labels, FEC-stack-depth may be		Mapping TLV contains one or more Implicit Null labels, FEC-
	greater than Label-stack-depth. To be consistent with the		stack-depth may be greater than Label-stack-depth. To be
	above stack-depths, the bottom is considered to be entry 1.		consistent with the above stack-depths, the bottom is
			considered to be entry 1.
	*/		*/
	Set FEC-stack-depth to 0. Set i to Label-stack-depth.		Set FEC-stack-depth to 0. Set i to Label-stack-depth.
	While (i > 0 ) do {		While (i > 0 ) do {
	++FEC-stack-depth.		++FEC-stack-depth.
	if Stack-D[FEC-stack-depth] != 3 (Implicit Null)		if Stack-D[FEC-stack-depth] != 3 (Implicit Null)
	--i.		--i.
	}		}
	skipping to change at page 41, line 32		skipping to change at page 37, line 22
	}		}
	Go to step 7 (Send Reply Packet).		Go to step 7 (Send Reply Packet).
	}		}
	5. Egress Processing:		5. Egress Processing:
	/* These steps are performed by the LSR that identified itself as		/* These steps are performed by the LSR that identified itself as
	the tail-end LSR for an LSP. */		the tail-end LSR for an LSP. */
	If received echo request contains no Downstream Mapping TLV, or		If received echo request contains no Downstream Detailed Mapping
	the Downstream IP Address is set to 127.0.0.1 or 0::1 go to step 6		TLV, or the Downstream IP Address is set to 127.0.0.1 or 0::1 go
	(Egress FEC Validation).		to step 6 (Egress FEC Validation).
	Verify that the IP address, interface address, and label stack in		Verify that the IP address, interface address, and label stack in
	the Downstream Mapping TLV match Interface-I and Stack-R. If not,		the Downstream Detailed Mapping TLV match Interface-I and Stack-R.
	set Best-return-code to 5, "Downstream Mapping Mis-match". A		If not, set Best-return-code to 5, "Downstream Mapping Mis-match".
	Received Interface and Label Stack TLV SHOULD be created for the		A Received Interface and Label Stack TLV SHOULD be created for the
	echo response packet. Go to step 7 (Send Reply Packet).		echo response packet. Go to step 7 (Send Reply Packet).
	6. Egress FEC Validation:		6. Egress FEC Validation:
	/* This is a loop for all entries in the Target FEC Stack starting		/* This is a loop for all entries in the Target FEC Stack starting
	with FEC-stack-depth. */		with FEC-stack-depth. */
	Perform FEC checking by following the algorithm described in		Perform FEC checking by following the algorithm described in
	subsection 4.4.1 for Label-L and the FEC at FEC-stack-depth.		subsection 4.4.1 for Label-L and the FEC at FEC-stack-depth.
	skipping to change at page 44, line 9		skipping to change at page 39, line 48
	replier are synchronized). The FEC Stack TLV from the echo request		replier are synchronized). The FEC Stack TLV from the echo request
	MAY be copied to the reply.		MAY be copied to the reply.
	The replier MUST fill in the Return Code and Subcode, as determined		The replier MUST fill in the Return Code and Subcode, as determined
	in the previous subsection.		in the previous subsection.
	If the echo request contains a Pad TLV, the replier MUST interpret		If the echo request contains a Pad TLV, the replier MUST interpret
	the first octet for instructions regarding how to reply.		the first octet for instructions regarding how to reply.
	If the replying router is the destination of the FEC, then Downstream		If the replying router is the destination of the FEC, then Downstream
	Mapping TLVs SHOULD NOT be included in the echo reply.		Detailed Mapping TLVs SHOULD NOT be included in the echo reply.
	If the echo request contains a Downstream Mapping TLV, and the		If the echo request contains a Downstream Detailed Mapping TLV, and
	replying router is not the destination of the FEC, the replier SHOULD		the replying router is not the destination of the FEC, the replier
	compute its downstream routers and corresponding labels for the		SHOULD compute its downstream routers and corresponding labels for
	incoming label, and add Downstream Mapping TLVs for each one to the		the incoming label, and add Downstream Detailed Mapping TLVs for each
	echo reply it sends back.		one to the echo reply it sends back.
	If the Downstream Mapping TLV contains Multipath Information		If the Downstream Detailed Mapping TLV contains Multipath Information
	requiring more processing than the receiving router is willing to		requiring more processing than the receiving router is willing to
	perform, the responding router MAY choose to respond with only a		perform, the responding router MAY choose to respond with only a
	subset of multipaths contained in the echo request Downstream		subset of multipaths contained in the echo request Downstream
	Mapping. (Note: The originator of the echo request MAY send another		Detailed Mapping. (Note: The originator of the echo request MAY send
	echo request with the Multipath Information that was not included in		another echo request with the Multipath Information that was not
	the reply.)		included in the reply.)
	Except in the case of Reply Mode 4, "Reply via application level		Except in the case of Reply Mode 4, "Reply via application level
	control channel", echo replies are always sent in the context of the		control channel", echo replies are always sent in the context of the
	IP/MPLS network.		IP/MPLS network.
	4.6. Receiving an MPLS Echo Reply		4.6. Receiving an MPLS Echo Reply
	An LSR X should only receive an MPLS echo reply in response to an		An LSR X should only receive an MPLS echo reply in response to an
	MPLS echo request that it sent. Thus, on receipt of an MPLS echo		MPLS echo request that it sent. Thus, on receipt of an MPLS echo
	reply, X should parse the packet to ensure that it is well-formed,		reply, X should parse the packet to ensure that it is well-formed,
	then attempt to match up the echo reply with an echo request that it		then attempt to match up the echo reply with an echo request that it
	had previously sent, using the destination UDP port and the Sender's		had previously sent, using the destination UDP port and the Sender's
	Handle. If no match is found, then X jettisons the echo reply;		Handle. If no match is found, then X jettisons the echo reply;
	otherwise, it checks the Sequence Number to see if it matches.		otherwise, it checks the Sequence Number to see if it matches.
	If the echo reply contains Downstream Mappings, and X wishes to		If the echo reply contains Downstream Detailed Mappings, and X wishes
	traceroute further, it SHOULD copy the Downstream Mapping(s) into its		to traceroute further, it SHOULD copy the Downstream Detailed
	next echo request(s) (with TTL incremented by one).		Mapping(s) into its next echo request(s) (with TTL incremented by
			one).
	4.7. Issue with VPN IPv4 and IPv6 Prefixes		4.7. Issue with VPN IPv4 and IPv6 Prefixes
	Typically, an LSP ping for a VPN IPv4 prefix or VPN IPv6 prefix is		Typically, an LSP ping for a VPN IPv4 prefix or VPN IPv6 prefix is
	sent with a label stack of depth greater than 1, with the innermost		sent with a label stack of depth greater than 1, with the innermost
	label having a TTL of 1. This is to terminate the ping at the egress		label having a TTL of 1. This is to terminate the ping at the egress
	PE, before it gets sent to the customer device. However, under		PE, before it gets sent to the customer device. However, under
	certain circumstances, the label stack can shrink to a single label		certain circumstances, the label stack can shrink to a single label
	before the ping hits the egress PE; this will result in the ping		before the ping hits the egress PE; this will result in the ping
	terminating prematurely. One such scenario is a multi-AS Carrier's		terminating prematurely. One such scenario is a multi-AS Carrier's
	skipping to change at page 45, line 21		skipping to change at page 41, line 14
	4.8. Non-compliant Routers		4.8. Non-compliant Routers
	If the egress for the FEC Stack being pinged does not support MPLS		If the egress for the FEC Stack being pinged does not support MPLS
	ping, then no reply will be sent, resulting in possible "false		ping, then no reply will be sent, resulting in possible "false
	negatives". If in "traceroute" mode, a transit LSR does not support		negatives". If in "traceroute" mode, a transit LSR does not support
	LSP ping, then no reply will be forthcoming from that LSR for some		LSP ping, then no reply will be forthcoming from that LSR for some
	TTL, say, n. The LSR originating the echo request SHOULD try sending		TTL, say, n. The LSR originating the echo request SHOULD try sending
	the echo request with TTL=n+1, n+2, ..., n+k to probe LSRs further		the echo request with TTL=n+1, n+2, ..., n+k to probe LSRs further
	down the path. In such a case, the echo request for TTL > n SHOULD		down the path. In such a case, the echo request for TTL > n SHOULD
	be sent with Downstream Mapping TLV "Downstream IP Address" field set		be sent with Downstream Detailed Mapping TLV "Downstream IP Address"
	to the ALLROUTERs multicast address until a reply is received with a		field set to the ALLROUTERs multicast address until a reply is
	Downstream Mapping TLV. The label stack MAY be omitted from the		received with a Downstream Detailed Mapping TLV. The label stack TLV
	Downstream Mapping TLV. Furthermore, the "Validate FEC Stack" flag		MAY be omitted from the Downstream Detailed Mapping TLV.
	SHOULD NOT be set until an echo reply packet with a Downstream		Furthermore, the "Validate FEC Stack" flag SHOULD NOT be set until an
	Mapping TLV is received.		echo reply packet with a Downstream Detailed Mapping TLV is received.
	5. Security Considerations		5. Security Considerations
	Overall, the security needs for LSP ping are similar to those of ICMP		Overall, the security needs for LSP ping are similar to those of ICMP
	ping.		ping.
	There are at least three approaches to attacking LSRs using the		There are at least three approaches to attacking LSRs using the
	mechanisms defined here. One is a Denial-of-Service attack, by		mechanisms defined here. One is a Denial-of-Service attack, by
	sending MPLS echo requests/replies to LSRs and thereby increasing		sending MPLS echo requests/replies to LSRs and thereby increasing
	their workload. The second is obfuscating the state of the MPLS data		their workload. The second is obfuscating the state of the MPLS data
	skipping to change at page 48, line 14		skipping to change at page 44, line 7
	values in the range 31744-32767 and 64512-65535 are for Vendor		values in the range 31744-32767 and 64512-65535 are for Vendor
	Private Use, and MUST NOT be allocated.		Private Use, and MUST NOT be allocated.
	If a TLV or sub-TLV has a Type that falls in the range for Vendor		If a TLV or sub-TLV has a Type that falls in the range for Vendor
	Private Use, the Length MUST be at least 4, and the first four octets		Private Use, the Length MUST be at least 4, and the first four octets
	MUST be that vendor's SMI Private Enterprise Number, in network octet		MUST be that vendor's SMI Private Enterprise Number, in network octet
	order. The rest of the Value field is private to the vendor.		order. The rest of the Value field is private to the vendor.
	TLVs and sub-TLVs defined in this document are the following:		TLVs and sub-TLVs defined in this document are the following:
	Type Sub-Type Value Field		Type Sub-Type Value Field
	---- -------- -----------		---- -------- -----------
	1 Target FEC Stack		1 Target FEC Stack
	1 LDP IPv4 prefix		1 LDP IPv4 prefix
	2 LDP IPv6 prefix		2 LDP IPv6 prefix
	3 RSVP IPv4 LSP		3 RSVP IPv4 LSP
	4 RSVP IPv6 LSP		4 RSVP IPv6 LSP
	5 Not Assigned		5 Not Assigned
	6 VPN IPv4 prefix		6 VPN IPv4 prefix
	7 VPN IPv6 prefix		7 VPN IPv6 prefix
	8 L2 VPN endpoint		8 L2 VPN endpoint
	9 "FEC 128" Pseudowire - IPv4 (Deprecated)		9 "FEC 128" Pseudowire - IPv4 (Deprecated)
	10 "FEC 128" Pseudowire - IPv4		10 "FEC 128" Pseudowire - IPv4
	11 "FEC 129" Pseudowire - IPv4		11 "FEC 129" Pseudowire - IPv4
	12 BGP labeled IPv4 prefix		12 BGP labeled IPv4 prefix
	13 BGP labeled IPv6 prefix		13 BGP labeled IPv6 prefix
	14 Generic IPv4 prefix		14 Generic IPv4 prefix
	15 Generic IPv6 prefix		15 Generic IPv6 prefix
	16 Nil FEC		16 Nil FEC
	24 "FEC 128" Pseudowire - IPv6		24 "FEC 128" Pseudowire - IPv6
	25 "FEC 129" Pseudowire - IPv6		25 "FEC 129" Pseudowire - IPv6
	2 Downstream Mapping		2 Downstream Mapping
	3 Pad		3 Pad
	4 Not Assigned		4 Not Assigned
	5 Vendor Enterprise Number		5 Vendor Enterprise Number
	6 Not Assigned		6 Not Assigned
	7 Interface and Label Stack		7 Interface and Label Stack
	8 Not Assigned		8 Not Assigned
	9 Errored TLVs		9 Errored TLVs
	Any value The TLV not understood		Any value The TLV not understood
	10 Reply TOS Byte		10 Reply TOS Byte
	7. Acknowledgements		7. Acknowledgements
	The original acknowledgements from RFC 4379 state the following:		The original acknowledgements from RFC 4379 state the following:
	This document is the outcome of many discussions among many		This document is the outcome of many discussions among many
	people, including Manoj Leelanivas, Paul Traina, Yakov Rekhter,		people, including Manoj Leelanivas, Paul Traina, Yakov Rekhter,
	Der-Hwa Gan, Brook Bailey, Eric Rosen, Ina Minei, Shivani		Der-Hwa Gan, Brook Bailey, Eric Rosen, Ina Minei, Shivani
	Aggarwal, and Vanson Lim.		Aggarwal, and Vanson Lim.
	The description of the Multipath Information sub-field of the		The description of the Multipath Information sub-field of the
	Downstream Mapping TLV was adapted from text suggested by Curtis		Downstream Mapping TLV was adapted from text suggested by Curtis
	Villamizar.		Villamizar.
	We would like to thank Loa Andersson for motivating the advancement		We would like to thank Loa Andersson for motivating the advancement
	of this bis specification. We also would like to thank Alexander		of this bis specification.
	Vainshtein for his review and comments.
			We also would like to thank Alexander Vainshtein, Yimin Shen, Curtis
			Villamizar, David Allan for their review and comments.
	8. References		8. References
	8.1. Normative References		8.1. Normative References
	[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -		[RFC1122] Braden, R., Ed., "Requirements for Internet Hosts -
	Communication Layers", STD 3, RFC 1122,		Communication Layers", STD 3, RFC 1122,
	DOI 10.17487/RFC1122, October 1989,		DOI 10.17487/RFC1122, October 1989,
	<http://www.rfc-editor.org/info/rfc1122>.		<http://www.rfc-editor.org/info/rfc1122>.
	skipping to change at page 50, line 20		skipping to change at page 46, line 15
	[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an		[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
	IANA Considerations Section in RFCs", BCP 26, RFC 5226,		IANA Considerations Section in RFCs", BCP 26, RFC 5226,
	DOI 10.17487/RFC5226, May 2008,		DOI 10.17487/RFC5226, May 2008,
	<http://www.rfc-editor.org/info/rfc5226>.		<http://www.rfc-editor.org/info/rfc5226>.
	[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,		[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
	"Network Time Protocol Version 4: Protocol and Algorithms		"Network Time Protocol Version 4: Protocol and Algorithms
	Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,		Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
	<http://www.rfc-editor.org/info/rfc5905>.		<http://www.rfc-editor.org/info/rfc5905>.
			[RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for
			Performing Label Switched Path Ping (LSP Ping) over MPLS
			Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011,
			<http://www.rfc-editor.org/info/rfc6424>.
	[RFC7506] Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert		[RFC7506] Raza, K., Akiya, N., and C. Pignataro, "IPv6 Router Alert
	Option for MPLS Operations, Administration, and		Option for MPLS Operations, Administration, and
	Maintenance (OAM)", RFC 7506, DOI 10.17487/RFC7506, April		Maintenance (OAM)", RFC 7506, DOI 10.17487/RFC7506, April
	2015, <http://www.rfc-editor.org/info/rfc7506>.		2015, <http://www.rfc-editor.org/info/rfc7506>.
	8.2. Informative References		8.2. Informative References
	[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,		[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
	RFC 792, DOI 10.17487/RFC0792, September 1981,		RFC 792, DOI 10.17487/RFC0792, September 1981,
	<http://www.rfc-editor.org/info/rfc792>.		<http://www.rfc-editor.org/info/rfc792>.
	skipping to change at page 51, line 19		skipping to change at page 47, line 19
	[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,		[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
	"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,		"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
	October 2007, <http://www.rfc-editor.org/info/rfc5036>.		October 2007, <http://www.rfc-editor.org/info/rfc5036>.
	[RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual		[RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual
	Circuit Connectivity Verification (VCCV): A Control		Circuit Connectivity Verification (VCCV): A Control
	Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,		Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085,
	December 2007, <http://www.rfc-editor.org/info/rfc5085>.		December 2007, <http://www.rfc-editor.org/info/rfc5085>.
			Appendix A. Deprecated TLVs
			A.1. FEC 128 Pseudowire
			FEC 128 (0x80) is defined in [RFC4447], as are the terms PW ID
			(Pseudowire ID) and PW Type (Pseudowire Type). A PW ID is a non-zero
			32-bit connection ID. The PW Type is a 15-bit number indicating the
			encapsulation type. It is carried right justified in the field below
			termed encapsulation type with the high-order bit set to zero. Both
			of these fields are treated in this protocol as opaque values.
			When an FEC 128 is encoded in a label stack, the following format is
			used. The value field consists of the remote PE IPv4 address (the
			destination address of the targeted LDP session), the PW ID, and the
			encapsulation type as follows:
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Remote PE IPv4 Address |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| PW ID |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| PW Type | Must Be Zero |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			This FEC is deprecated and is retained only for backward
			compatibility. Implementations of LSP ping SHOULD accept and process
			this TLV, but SHOULD send LSP ping echo requests with the new TLV
			(see next section), unless explicitly configured to use the old TLV.
			An LSR receiving this TLV SHOULD use the source IP address of the LSP
			echo request to infer the sender's PE address.
			A.2. Downstream Mapping(DSMAP)
			The Downstream Mapping object is a TLV that MAY be included in an
			echo request message. Only one Downstream Mapping object may appear
			in an echo request. The presence of a Downstream Mapping object is a
			request that Downstream Mapping objects be included in the echo
			reply. If the replying router is the destination of the FEC, then a
			Downstream Mapping TLV SHOULD NOT be included in the echo reply.
			Otherwise the replying router SHOULD include a Downstream Mapping
			object for each interface over which this FEC could be forwarded.
			For a more precise definition of the notion of "downstream", see
			section 3.3.2, "Downstream Router and Interface".
			The Length is K + M + 4*N octets, where M is the Multipath Length,
			and N is the number of Downstream Labels. Values for K are found in
			the description of Address Type below. The Value field of a
			Downstream Mapping has the following format:
			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
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| MTU | Address Type | DS Flags |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Downstream IP Address (4 or 16 octets) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Downstream Interface Address (4 or 16 octets) |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Multipath Type| Depth Limit | Multipath Length |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			. .
			. (Multipath Information) .
			. .
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Downstream Label | Protocol |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			. .
			. .
			. .
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			| Downstream Label | Protocol |
			+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
			Maximum Transmission Unit (MTU)
			The MTU is the size in octets of the largest MPLS frame (including
			label stack) that fits on the interface to the Downstream LSR.
			Address Type
			The Address Type indicates if the interface is numbered or
			unnumbered. It also determines the length of the Downstream IP
			Address and Downstream Interface fields. The resulting total for
			the initial part of the TLV is listed in the table below as "K
			Octets". The Address Type is set to one of the following values:
			Type # Address Type K Octets
			------ ------------ --------
			1 IPv4 Numbered 16
			2 IPv4 Unnumbered 16
			3 IPv6 Numbered 40
			4 IPv6 Unnumbered 28
			DS Flags
			The DS Flags field is a bit vector with the following format:
			0 1 2 3 4 5 6 7
			+-+-+-+-+-+-+-+-+
			| Rsvd(MBZ) |I|N|
			+-+-+-+-+-+-+-+-+
			Two flags are defined currently, I and N. The remaining flags MUST
			be set to zero when sending and ignored on receipt.
			Flag Name and Meaning
			---- ----------------
			I Interface and Label Stack Object Request
			When this flag is set, it indicates that the replying
			router SHOULD include an Interface and Label Stack
			Object in the echo reply message.
			N Treat as a Non-IP Packet
			Echo request messages will be used to diagnose non-IP
			flows. However, these messages are carried in IP
			packets. For a router that alters its ECMP algorithm
			based on the FEC or deep packet examination, this flag
			requests that the router treat this as it would if the
			determination of an IP payload had failed.
			Downstream IP Address and Downstream Interface Address
			IPv4 addresses and interface indices are encoded in 4 octets; IPv6
			addresses are encoded in 16 octets.
			If the interface to the downstream LSR is numbered, then the
			Address Type MUST be set to IPv4 or IPv6, the Downstream IP
			Address MUST be set to either the downstream LSR's Router ID or
			the interface address of the downstream LSR, and the Downstream
			Interface Address MUST be set to the downstream LSR's interface
			address.
			If the interface to the downstream LSR is unnumbered, the Address
			Type MUST be IPv4 Unnumbered or IPv6 Unnumbered, the Downstream IP
			Address MUST be the downstream LSR's Router ID, and the Downstream
			Interface Address MUST be set to the index assigned by the
			upstream LSR to the interface.
			If an LSR does not know the IP address of its neighbor, then it
			MUST set the Address Type to either IPv4 Unnumbered or IPv6
			Unnumbered. For IPv4, it must set the Downstream IP Address to
			127.0.0.1; for IPv6 the address is set to 0::1. In both cases,
			the interface index MUST be set to 0. If an LSR receives an Echo
			Request packet with either of these addresses in the Downstream IP
			Address field, this indicates that it MUST bypass interface
			verification but continue with label validation.
			If the originator of an Echo Request packet wishes to obtain
			Downstream Mapping information but does not know the expected
			label stack, then it SHOULD set the Address Type to either IPv4
			Unnumbered or IPv6 Unnumbered. For IPv4, it MUST set the
			Downstream IP Address to 224.0.0.2; for IPv6 the address MUST be
			set to FF02::2. In both cases, the interface index MUST be set to
			0. If an LSR receives an Echo Request packet with the all-routers
			multicast address, then this indicates that it MUST bypass both
			interface and label stack validation, but return Downstream
			Mapping TLVs using the information provided.
			Multipath Type
			The following Multipath Types are defined:
			Key Type Multipath Information
			--- ---------------- ---------------------
			0 no multipath Empty (Multipath Length = 0)
			2 IP address IP addresses
			4 IP address range low/high address pairs
			8 Bit-masked IP IP address prefix and bit mask
			address set
			9 Bit-masked label set Label prefix and bit mask
			Type 0 indicates that all packets will be forwarded out this one
			interface.
			Types 2, 4, 8, and 9 specify that the supplied Multipath
			Information will serve to exercise this path.
			Depth Limit
			The Depth Limit is applicable only to a label stack and is the
			maximum number of labels considered in the hash; this SHOULD be
			set to zero if unspecified or unlimited.
			Multipath Length
			The length in octets of the Multipath Information.
			Multipath Information
			Address or label values encoded according to the Multipath Type.
			See the next section below for encoding details.
			Downstream Label(s)
			The set of labels in the label stack as it would have appeared if
			this router were forwarding the packet through this interface.
			Any Implicit Null labels are explicitly included. Labels are
			treated as numbers, i.e., they are right justified in the field.
			A Downstream Label is 24 bits, in the same format as an MPLS label
			minus the TTL field, i.e., the MSBit of the label is bit 0, the
			LSBit is bit 19, the Traffic Class (TC) bits are bits 20-22, and
			bit 23 is the S bit. The replying router SHOULD fill in the TC
			and S bits; the LSR receiving the echo reply MAY choose to ignore
			these bits. Protocol
			The Protocol is taken from the following table:
			Protocol # Signaling Protocol
			---------- ------------------
			0 Unknown
			1 Static
			2 BGP
			3 LDP
			4 RSVP-TE
	Authors' Addresses		Authors' Addresses
	Kireeti Kompella		Kireeti Kompella
	Juniper Networks, Inc.		Juniper Networks, Inc.
	Email: kireeti.kompella@gmail.com		Email: kireeti.kompella@gmail.com
	Carlos Pignataro		Carlos Pignataro
	Cisco Systems, Inc.		Cisco Systems, Inc.
	Email: cpignata@cisco.com		Email: cpignata@cisco.com
	Nagendra Kumar		Nagendra Kumar
	Cisco Systems, Inc.		Cisco Systems, Inc.
	Email: naikumar@cisco.com		Email: naikumar@cisco.com
End of changes. 49 change blocks.
	400 lines changed or deleted		433 lines changed or added
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