draft-ietf-mpls-icmp-00.txt		draft-ietf-mpls-icmp-01.txt
	MPLS Working Group		MPLS Working Group R.Bonica
	INTERNET DRAFT Ron Bonica		Internet Draft MCIWorldCom
	July 1999 MCI WorldCom		Document: draft-ietf-mpls-icmp-01.txt D.Tappan
	Expires January 2000 Daniel C. Tappan
	Cisco Systems		Cisco Systems
	Der-Hwa Gan		D.Gan
	Juniper Networks		Juniper Networks
			December 1999
	ICMP Extensions for MultiProtocol Label Switching		ICMP Extensions for MultiProtocol Label Switching
	draft-ietf-mpls-icmp-00.txt
	Status of this Memo		Status of this Memo
	This document is an Internet-Draft and is in full conformance with		This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of [RFC-2026].		all provisions of Section 10 of [RFC-2026].
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that		Task Force (IETF), its areas, and its working groups. Note that
	other groups may also distribute working documents as Internet-		other groups may also distribute working documents as Internet-
	Drafts.		Drafts. Internet-Drafts are draft documents valid for a maximum of
			six months and may be updated, replaced, or obsoleted by other
	Internet-Drafts are draft documents valid for a maximum of six		documents at any time. It is inappropriate to use Internet-Drafts as
	months and may be updated, replaced, or obsoleted by other documents
	at any time. It is inappropriate to use Internet- Drafts as
	reference material or to cite them other than as "work in progress."		reference material or to cite them other than as "work in progress."
	The list of current Internet-Drafts can be accessed at		The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt.		http://www.ietf.org/ietf/1id-abstracts.txt
	The list of Internet-Draft Shadow Directories can be accessed at		The list of Internet-Draft Shadow Directories can be accessed at
	http://www.ietf.org/shadow.html.		http://www.ietf.org/shadow.html.
	1. Abstract		1. Abstract
	The current memo proposes extensions to ICMP that permit LSRs to		The current memo proposes extensions to ICMP that permit Label
	append MPLS information to ICMP messages.		Switching Routers to append MPLS information to ICMP messages.
	2. Conventions used in this document		2. Conventions used in this document
	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" are to		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
	be interpreted as described in [RFC-2119].		this document are to be interpreted as described in [RFC-2119].
	3. Introduction		3. Introduction
	Routers and destination hosts use the Internet Control Message		Routers and destination hosts use the Internet Control Message
	Protocol (ICMP) [RFC-792] to convey control information to source		Protocol (ICMP) [RFC-792] to convey control information to source
	hosts. Network operators use this information to detect and diagnose		hosts. Network operators use this information to diagnose routing
	Layer 3 routing problems.		problems.
			Bonica, Tappan, Hwa Draft-Expires May 2000 1
	When a router receives an undeliverable IP datagram, it can send an		When a router receives an undeliverable IP datagram, it can send an
	ICMP message to the host that originated the datagram. The ICMP		ICMP message to the host that originated the datagram. The ICMP
	message indicates why the datagram could not be delivered. It also		message indicates why the datagram could not be delivered. It also
	contains the IP header and leading payload bytes of the		contains the IP header and leading payload octets of the "original
	undeliverable datagram.		datagram".
	MPLS Label Switching Routers (LSRs) also use ICMP to convey control		In this document, the term "original datagram" refers to the
			datagram to which the ICMP message is a response.
			MPLS Label Switching Routers (LSR) also use ICMP to convey control
	information to source hosts. Sections 2.3 and 2.4 of [ENCODE]		information to source hosts. Sections 2.3 and 2.4 of [ENCODE]
	describe the interaction between MPLS and ICMP.		describe the interaction between MPLS and ICMP.
	When an LSR receives an undeliverable MPLS labeled datagram, it		When an LSR receives an undeliverable MPLS encapsulated datagram, it
	removes the entire MPLS label stack, exposing the encapsulated IP		removes the entire MPLS label stack, exposing the previously
	datagram. The router then submits the IP datagram to a network-		encapsulated IP datagram. The LSR then submits the IP datagram to a
	forwarding module for error processing. Error processing can include		network-forwarding module for error processing. Error processing can
	ICMP message generation.		include ICMP message generation.
	Although the ICMP message contains the non-delivery reason, IP		The ICMP message indicates why the original datagram could not be
	header and leading payload bytes, it contains no information		delivered. It also contains the IP header and leading octets of the
	regarding the MPLS label stack that encapsulated the datagram when		original datagram.
	it arrived at the LSR.
	The current memo proposes extensions to ICMP that permit LSRs to		The ICMP message, however, includes no information regarding the
	append MPLS label stack information to the ICMP message body. Hence,		MPLS label stack that encapsulated the original datagram when it
	ICMP messages regarding undeliverable MPLS encapsulated datagrams		arrived at the LSR. This omission is significant because the LSR
	SHOULD include the MPLS label stack, as it arrived at the router		would have routed the original datagram based upon information
	that is sending the ICMP message. The ICMP message MUST also include		contained by the MPLS label stack.
	the IP header and leading payload bytes of the undeliverable
	datagram.
	Network operators will use this information to detect and diagnose		The current memo proposes extensions to ICMP that permit an LSR to
	MPLS problems.		append MPLS label stack information to ICMP messages. ICMP messages
			regarding MPLS encapsulated datagrams SHOULD include the MPLS label
			stack, as it arrived at the router that is sending the ICMP message.
			The ICMP message MUST also include the IP header and leading payload
			octets of the original datagram.
			Network operators will use this information to diagnose routing
			problems.
	4. Motivation		4. Motivation
	ICMP extensions defined in the current memo support enhancements to		ICMP extensions defined in the current memo support enhancements to
	TRACEROUTE. The enhanced TRACEROUTE, like older TRACEROUTE		TRACEROUTE. The enhanced TRACEROUTE, like older implementations,
	implementations, reports each IP router and LSR that a datagram		indicates which nodes the original datagram visited en route to its
	visits en route to its destination. The enhanced TRACEROUTE differs		ultimate destination. It differs from older implementations in that
	from older implementations in that it indicates which nodes were		it also indicates the original datagrams MPLS encapsulation status
	visited while traversing a Label Switched Path (LSP).		as it arrived at each node.
	Figure 1 contains sample output from an enhanced TRACEROUTE		Figure 1 contains sample output from an enhanced TRACEROUTE
	implementation.		implementation.
			Bonica,Tappan,Gan Draft-Expires May 2000 2
	>Traceroute 166.45.2.74		>Traceroute 166.45.2.74
	traceroute to 166.45.2.74, 30 hops max, 40 byte packets		traceroute to 166.45.2.74, 30 hops max, 40 byte packets
	1 166.45.5.1 1.281 ms 1.103 ms 1.096 ms		1 166.45.5.1 1.281 ms 1.103 ms 1.096 ms
			2 166.45.4.1 1.281 ms 1.103 ms 1.096 ms mplsLabel1=2001
	2 166.45.4.1 1.281 ms 1.103 ms 1.096 ms		mplsExpBits1=0
	mplsLabel1=2001 mplsExpBits1=0		3 166.45.3.1 1.281 ms 1.103 ms 1.096 ms mplsLabel1=2002
	3 166.45.3.1 1.281 ms 1.103 ms 1.096 ms		mplsExpBits1=0
	mplsLabel1=2002 mplsExpBits1=0		4 166.45.6.1 1.281 ms 1.103 ms 1.096 ms mplsLabel1=2003
	4 166.45.6.1 1.281 ms 1.103 ms 1.096 ms		mplsExpBits1=0
	mplsLabel1=2003 mplsExpBits1=0
	5 166.45.2.1 1.281 ms 1.103 ms 1.096 ms		5 166.45.2.1 1.281 ms 1.103 ms 1.096 ms
	6 166.45.2.74 1.281 ms 1.103 ms 1.096 ms		6 166.45.2.74 1.281 ms 1.103 ms 1.096 ms
	Figure 1. Enhanced TRACEROUTE sample output		Figure 1. Enhanced TRACEROUTE sample output
	5. Disclaimer		5. Disclaimer
	The current memo does not define the general relationship between		The current memo does not define the general relationship between
	ICMP and MPLS. Sections 2.3 and 2.4 of [ENCODE] define this		ICMP and MPLS. Sections 2.3 and 2.4 of [ENCODE] define this
	relationship.		relationship.
	Specifically, this document defers to [ENCODE] with respect to the		Specifically, this document defers to [ENCODE] with respect to the
	following issues:		following issues:
	- conditions upon which LSRs emit ICMP messages		- conditions upon which an LSR emits ICMP messages
	- handling of ICMP messages bound for hosts that are identified		- handling of ICMP messages bound for hosts that are identified
	by private addresses		by private addresses
	The current memo does not define encapsulation specific TTL		The current memo does not define encapsulation specific TTL
	manipulation procedures. It defers to Section 10 of [MPLSATM] and		manipulation procedures. It defers to Section 10 of [MPLSATM] and
	Section 5.4 of [MPLSFRAME] in this matter.		Section 5.4 of [MPLSFRAME] in this matter.
	When encapsulation specific TTL manipulation procedures defeat the		When encapsulation specific TTL manipulation procedures defeat the
	basic TRACEROUTE mechanism, they will also defeat enhanced		basic TRACEROUTE mechanism, they will also defeat enhanced
	TRACEROUTE implementations.		TRACEROUTE implementations.
	6. Backward Compatibility		The current memo does not address extensions to ICMPv6. These should
			be addressed in a separate draft.
	ICMP extensions proposed in this document MUST be backward		6. Formal Syntax
	compatible with the syntax described in RFC-792. Extensions proposed
	in this memo MUST NOT change or deprecate any field defined in RFC-
	792.
	7. Formal Syntax		This section defines a data structure that an LSR can append to
			selected ICMP messages. The data structure contains the MPLS label
			stack that encapsulated the original datagram when it arrived at the
			LSR.
	This section describes a data structure that can be appended to the		The data structure defined herein can be appended to the following
	following ICMP message types:		ICMP message types:
			Bonica,Tappan,Gan Draft-Expires May 2000 3
	1) Destination Unreachable		1) Destination Unreachable
	2) Time Exceeded		2) Time Exceeded
	3) Parameter Problem		3) Parameter Problem
	4) Source Quench		4) Source Quench
	5) Redirect		5) Redirect
	The above listed ICMP message types specify a fixed length of 56		According to RFC-792, the final field contained by each of these
	bytes. When the data structure defined in this section is appended		ICMP message types reflects the IP header and leading 64 bits of the
	to an ICMP message, the ICMP _total length_ field MUST equal the		original datagram. [RFC-1812] recommends that this final field be
	data structure length plus 56.		extended to include as much of the original datagram as possible.
			When an LSR appends the data structure defined herein to an ICMP
			message, the final field of the ICMP message body MUST contain the
			first 128 octets of the original datagram. At least 20 of these 128
			octets represent the IP header of the original datagram.
			If the original datagram was shorter than 128 octets, the final
			field MUST be padded with 0's.
			When an LSR appends the data structure defined herein to an ICMP
			message, the ICMP "total length" MUST be equal to the data structure
			length plus 156. The first octet of the data structure must be
			displaced 156 octets from the beginning of the ICMP message.
	The data structure defined in this section consists of a common		The data structure defined in this section consists of a common
	header followed by object instances. Each object instance consists		header followed by object instances. Each object instance consists
	of an object header plus contents.		of an object header plus contents.
	Currently, only one object class is defined. This object class		Currently, two object classes are defined. One object class contains
	contains an entire MPLS label stack, formatted exactly as it was		an entire MPLS label stack, formatted exactly as it was when it
	when it arrived at the LSR that sends the ICMP message.		arrived at the LSR that sends the ICMP message. The other contains
			some portion of the original datagram that could not be included in
			the final field of the ICMP message body (i.e., the octet 129 and
			beyond).
			Both object classes are optional.
	In the future, additional object classes may be defined.		In the future, additional object classes may be defined.
	7.1 Common Header		6.1 Common Header
	0 1 2 3		0 1 2 3
	+-------------+-------------+-------------+-------------+		+-------------+-------------+-------------+-------------+
	| Vers | (Reserved) | Checksum |		| Vers | (Reserved) | Checksum |
	+-------------+-------------+-------------+-------------+		+-------------+-------------+-------------+-------------+
	The fields in the common header are as follows:		The fields in the common header are as follows:
			Bonica,Tappan,Gan Draft-Expires May 2000 4
	Vers: 4 bits		Vers: 4 bits
	ICMP extension version number. This is version 1.		ICMP extension version number.
			This is version 2.
	Checksum: 16 bits		Checksum: 16 bits
	The one's complement of the one's complement sum of the data		The one's complement of the one's complement sum of the data
	structure, with the checksum field replaced by zero for the		structure, with the checksum field replaced by zero for the purpose
	purpose of computing the checksum. An all-zero value means that		of computing the checksum. An all-zero value means that no checksum
	no checksum was transmitted.		was transmitted.
	If the checksum field contains a value other than described
	above, bytes 56 and beyond of the ICMP message do not contain
	the data structure described by this memo. These bytes may
	contain an extended ICMP payload as described in Section 4.3.2.3
	of [RFC-1812].
	Reserved:		If the checksum field contains a value other than described above,
			the ICMP message does not include the extensions described in this
			memo. This, however, does not imply that the ICMP message is
			malformed. It may be in strict compliance with RFC-1812.
	Must be set to 0.		Reserved: Must be set to 0.
	7.2 Object Header		6.2 Object Header
	Every object consists of one or more 32-bit words with a one-word		Every object consists of one or more 32-bit words with a one-word
	header, with the following format:		header, with the following format:
	0 1 2 3
	+-------------+-------------+-------------+-------------+		+-------------+-------------+-------------+-------------+
	| Length | Class-Num | C-Type |		| Length | Class-Num | C-Type |
	+-------------+-------------+-------------+-------------+		+-------------+-------------+-------------+-------------+
	| |		| |
	// (Object contents) //		| // (Object contents) // |
	| |		| |
	+-------------+-------------+-------------+-------------+		+-------------+-------------+-------------+-------------+
	An object header has the following fields:		An object header has the following fields:
	Length: 16 bits		Length: 16 bits
	Length of the object, measured in bytes, including the object		Length of the object, measured in octets, including the object
	header and object contents.		header and object contents.
	Class-Num: 8 bits		Class-Num: 8 bits
	Identifies object class. Currently, the only one object class		Identifies object class.
	is defined. This is the MPLS Stack Entry Object.
	C-Type: 8 bits		C-Type: 8 bits
	Identifies object sub-type. Currently, only one object sub-type		Identifies object sub-type.
	is defined.
	7.3 MPLS Stack Entry Object Class		Bonica,Tappan,Gan Draft-Expires May 2000 5
	An instance of the MPLS Entry Object class represents the entire		6.3 MPLS Stack Entry Object Class
	MPLS label stack, formatted exactly as it was when it arrived at the
	LSR that sends the ICMP message.
	In the illustration below, bytes 0-3 depict the first member of the		A single instance of the MPLS Entry Object class represents the
			entire MPLS label stack, formatted exactly as it was when it arrived
			at the LSR that sends the ICMP message
			In the illustration below, octets 0-3 depict the first member of the
	MPLS label stack. Each remaining member of the MPLS label stack is		MPLS label stack. Each remaining member of the MPLS label stack is
	represented by another 4 bytes that share the same format.		represented by another 4 octets that share the same format.
	Syntax follows:		Syntax follows:
	MPLS Stack Entry Class = 1, C-Type = 1.		MPLS Stack Entry Class = 1, C-Type = 1.
	0 1 2 3		0 1 2 3
	+-------------+-------------+-------------+-------------+		+-------------+-------------+-------------+-------------+
	| Label |EXP |S| TTL |		| Label |EXP |S| TTL |
	+-------------+-------------+-------------+-------------+		+-------------+-------------+-------------+-------------+
	| |		| |
	// Remaining MPLS Stack Entries //		| // Remaining MPLS Stack Entries // |
	| |		| |
	+-------------+-------------+-------------+-------------+		+-------------+-------------+-------------+-------------+
	Label: 20 bits		Label: 20 bits
	Exp: Experimental Use, 3 bits		Exp: Experimental Use, 3 bits
	S: Bottom of Stack, 1 bit		S: Bottom of Stack, 1 bit
	TTL: Time to Live, 8 bits		TTL: Time to Live, 8 bits
			6.4 Extended Payload Object Class
			An instance of the Extended Payload Object class represents some
			portion of the original datagram that could not be fit in the final
			field of the ICMP message body (i.e., octets beyond 128).
			Syntax follows:
			MPLS Stack Entry Class = 2, C-Type = 1.
			0 1 2 3
			+-------------+-------------+-------------+-------------+
			| |
			| // Remaining MPLS Stack Entries // |
			| |
			+-------------+-------------+-------------+-------------+
			Bonica,Tappan,Gan Draft-Expires May 2000 6
			7. Backward Compatibility
			ICMP extensions proposed in this document MUST be backward
			compatible with the syntax described in RFC-792. Extensions proposed
			in this memo MUST NOT change or deprecate any field defined in RFC-
			792.
			The extensions defined herein are in keeping with the spirit, if not
			the letter of RFC-1812. In order to support IP-in-IP tunneling, RFC-
			1812 extends the final field of selected ICMP messages to include a
			greater portion of the original datagram. Unfortunately, it extends
			this field to a variable length without adding a length attribute.
			This memo binds the length of that final field to an arbitrarily
			large value (128 octets). Fixing the length of that field
			facilitates extension of the ICMP message. An additional object is
			provided through which octets 129 and beyond can be appended to the
			ICMP message.
			As few datagrams contain L3 or L4 header information beyond octet
			128, it is unlikely that the extensions described herein will
			disable any applications that rely upon RFC-1812 style ICMP
			messages.
	8.Security Considerations		8.Security Considerations
	This memo presents no security considerations beyond those already		This memo presents no security considerations beyond those already
	presented by current ICMP applications (e.g., traceroute).		presented by current ICMP applications (e.g., traceroute).
	9. References		9. References
	[ARCH], Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol		[ARCH], Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
	Label Switching Architecture", Internet Draft <draft-ietf-mpls-arch-		Label Switching Architecture", Internet Draft <draft-ietf-mpls-arch-
	02.txt>, July, 1998		06.txt>, August, 1999
	[ENCODE], Rosen, E., Rekhter, Y., Tappan, D, Farinacci, D.,		[ENCODE], Rosen, E., Rekhter, Y., Tappan, D, Farinacci, D.,
	Fedorkow, G., Li, T., Conta, A., _MPLS Stack Encoding_, Internet		Fedorkow, G., Li, T., Conta, A., "MPLS Stack Encoding", Internet
	Draft, <draft-ietf-mpls-label-encapse-03.txt>, September 1998.		Draft, <draft-ietf-mpls-label-encapse-07.txt>, September 1999.
	[FRAME], Callon, R., Doolan, P., Feldman, N., Fredette, A.,		[FRAME], Callon, R., Doolan, P., Feldman, N., Fredette, A., Swallow,
	Swallow, G., and A. Viswanathan, "A Framework for Multiprotocol		G., and A. Viswanathan, "A Framework for Multiprotocol Label
	Label Switching", Internet Draft <draft-ietf-mpls-framework-02.txt>,		Switching", Internet Draft <draft-ietf-mpls-framework-05.txt>,
	November 1997.		September 1999.
	[MPLSATM], Davie, B., Lawrence, J., McCloghrie, K., Rekhter, Y.,		[MPLSATM], Davie, B., Lawrence, J., McCloghrie, K., Rekhter, Y.,
	Rosen, E., Swallow, G, _MPLS using ATM VC Switching_, <draft-ietf-		Rosen, E., Swallow, G, "MPLS using ATM VC Switching", <draft-ietf-
	mpls-atm-01.txt>, November, 1998.		mpls-atm-01.txt>, November, 1998.
	[MPLSFRAME], Conta, A., Doolan, P., Malis, A., _Use of Label		Bonica,Tappan,Gan Draft-Expires May 2000 7
	Switching on Frame Relay Networks_, <draft-ietf-mpls-fr-03.txt>,		[MPLSFRAME], Conta, A., Doolan, P., Malis, A., "Use of Label
			Switching on Frame Relay Networks", <draft-ietf-mpls-fr-03.txt>,
	November, 1998.		November, 1998.
	[RFC-792], Postel, J., _Internet Control Message Protocol_, RFC 792,		[RFC-792], Postel, J., "Internet Control Message Protocol", RFC 792,
	ISI, September 1981.		ISI, September 1981.
	[RFC-1812], Baker, F., _Requirements for IP Version 4 Routers_, RFC		[RFC-1812], Baker, F., "Requirements for IP Version 4 Routers", RFC
	1812, June 1995.		1812, June 1995.
	[RFC-2026], Bradner, S., _Internet Standards Process _ Revision 3_,		[RFC-2026], Bradner, S., "Internet Standards Process Revision 3",
	RFC 2026, Harvard University, October 1996.		RFC 2026, Harvard University, October 1996.
	[RFC-2119], Bradner, S,, "Key words for use in RFCs to Indicate		[RFC-2119], Bradner, S,, "Key words for use in RFCs to Indicate
	Requirement Levels", RFC 2119, Harvard University, March 1997		Requirement Levels", RFC 2119, Harvard University, March 1997
	10. Author's Addresses		10. Acknowledgments
			Thanks to Yakov Rekhter and Mike Heard for their contributions to
			this memo.
			11. Author's Addresses
	Ronald P. Bonica		Ronald P. Bonica
	MCI WorldCom		MCI WorldCom
	2100 Reston Parkway		22001 Loudoun County Pkwy
	Reston, Virginia, U.S.A. 20191		Ashburn, Virginia, 20147
	Phone: +1 703 715 7176		Phone: 703 886 1681
	Email: rbonica@mci.net		Email: rbonica@mci.net
	Daniel C. Tappan		Daniel C. Tappan
	Cisco Systems		Cisco Systems
	250 Apollo Drive		250 Apollo Drive
	Chelmsford, Massachusetts, 01824		Chelmsford, Massachusetts, 01824
	Email: tappan@cisco.com		Email: tappan@cisco.com
	Der-Hwa Gan		Der-Hwa Gan
	Juniper Networks		Juniper Networks
	385 Ravendale Drive		385 Ravendale Drive
	Mountain View, California 94043		Mountain View, California 94043
	Email: dhg@juniper.net		Email: dhg@juniper.net
			Bonica,Tappan,Gan Draft-Expires May 2000 8
			Full Copyright Statement
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			followed, or as required to translate it into
			Bonica,Tappan,Gan Draft-Expires May 2000 9
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