< draft-ietf-mpls-cr-ldp-05.txt		draft-ietf-mpls-cr-ldp-06.txt >
			A new Request for Comments is now available in online RFC libraries.
	MPLS Working Group Bilel Jamoussi, Editor		RFC 3212
	Internet Draft Nortel Networks Corp.
	Expiration Date: August 2001
	O. Aboul-Magd, L. Andersson, P. Ashwood-Smith,
	F. Hellstrand, K. Sundell, Nortel Networks Corp.
	R. Callon, Juniper Networks.
	R. Dantu, L. Wu, Cisco Systems
	P. Doolan, T. Worster, Ennovate Networks Corp.
	N. Feldman, IBM Corp.
	A. Fredette, PhotonEx Corp.
	M. Girish, Atoga Systems
	E. Gray, Sandburst
	J. Halpern, Longitude Systems, Inc.
	J. Heinanen, Telia Finland
	T. Kilty, Newbridge Networks, Inc.
	A. Malis, Vivace Networks
	P. Vaananen, Nokia Telecommunications
	February 2001
	Constraint-Based LSP Setup using LDP
	draft-ietf-mpls-cr-ldp-05.txt
	Status of this Memo
	This document is an Internet-Draft and is in full conformance with
	all provisions of Section 10 of RFC2026.
	Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF), its areas, and its working groups. Note that
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	Drafts.
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	material or to cite them other than as "work in progress.ö
	The list of current Internet-Drafts can be accessed at
	http://www.ietf.org/ietf/1id-abstracts.txt
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	http://www.ietf.org/shadow.html.
	Abstract
	Label Distribution Protocol (LDP) is defined in [1] for distribution
	of labels inside one MPLS domain. One of the most important
	services that may be offered using MPLS in general and LDP in
	particular is support for constraint-based routing of traffic across
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 1
	the routed network. Constraint-based routing offers the opportunity
	to extend the information used to setup paths beyond what is
	available for the routing protocol. For instance, an LSP can be
	setup based on explicit route constraints, QoS constraints, and
	other constraints. Constraint-based routing (CR) is a mechanism used
	to meet Traffic Engineering requirements that have been proposed by,
	[2] and [3]. These requirements may be met by extending LDP for
	support of constraint-based routed label switched paths (CR-LSPs).
	Other uses for CR-LSPs include MPLS-based VPNs [4]. More information
	about the applicability of CR-LDP can be found in [5].
	This draft specifies mechanisms and TLVs for support of CR-LSPs
	using LDP.
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
	NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
	in this document are to be interpreted as described in RFC 2119 [6].
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 2
	Table of Contents
	1. Introduction....................................................4
	2. Constraint-based Routing Overview...............................4
	2.1 Strict and Loose Explicit Routes...............................5
	2.2 Traffic Characteristics........................................5
	2.3 Pre-emption....................................................6
	2.4 Route Pinning..................................................6
	2.5 Resource Class.................................................6
	3. Solution Overview...............................................6
	3.1 Required Messages and TLVs.....................................8
	3.2 Label Request Message..........................................8
	3.3 Label Mapping Message..........................................9
	3.4 Notification Message...........................................9
	3.5 Release , Withdraw, and Abort Messages........................10
	4. Protocol Specification.........................................10
	4.1 Explicit Route TLV (ER-TLV)...................................11
	4.2 Explicit Route Hop TLV (ER-Hop TLV)...........................11
	4.3 Traffic Parameters TLV........................................12
	4.3.1 Semantics...................................................14
	4.3.1.1 Frequency.................................................14
	4.3.1.2 Peak Rate.................................................14
	4.3.1.3 Committed Rate............................................14
	4.3.1.4 Excess Burst Size.........................................15
	4.3.1.5 Peak Rate Token Bucket....................................15
	4.3.1.6 Committed Data Rate Token Bucket..........................15
	4.3.1.7 Weight....................................................16
	4.3.2 Procedures..................................................16
	4.3.2.1 Label Request Message.....................................16
	4.3.2.2 Label Mapping Message.....................................17
	4.3.2.3 Notification Message......................................17
	4.4 Preemption TLV................................................17
	4.5 LSPID TLV.....................................................18
	4.6 Resource Class (Color) TLV....................................20
	4.7 ER-Hop semantics..............................................20
	4.7.1. ER-Hop 1: The IPv4 prefix..................................20
	4.7.2. ER-Hop 2: The IPv6 address.................................21
	4.7.3. ER-Hop 3: The autonomous system number....................21
	4.7.4. ER-Hop 4: LSPID............................................22
	4.8. Processing of the Explicit Route TLV.........................23
	4.8.1. Selection of the next hop..................................23
	4.8.2. Adding ER-Hops to the explicit route TLV...................25
	4.9 Route Pinning TLV.............................................25
	4.10 CR-LSP FEC Element...........................................26
	5. IANA Considerations............................................26
	5.1 TLV Type Name Space...........................................26
	5.2 FEC Type Name Space...........................................27
	5.3 Status Code Space.............................................27
	6. Security.......................................................28
	7. Acknowledgments................................................28
	8. Intellectual Property Consideration............................28
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 3
	9. References.....................................................28
	10. AuthorÆs Addresses............................................29
	Appendix A: CR-LSP Establishment Examples.........................31
	A.1 Strict Explicit Route Example.................................31
	A.2 Node Groups and Specific Nodes Example........................32
	Appendix B. QoS Service Examples..................................35
	B.1 Service Examples..............................................35
	B.2 Establishing CR-LSP Supporting Real-Time Applications.........36
	B.3 Establishing CR-LSP Supporting Delay Insensitive Applications.37
	1. Introduction
	The need for constraint-based routing (CR) in MPLS has been explored
	elsewhere [2], and [3]. Explicit routing is a subset of the more
	general constraint-based routing function. At the MPLS WG meeting
	held during the Washington IETF (December 1997) there was consensus
	that LDP should support explicit routing of LSPs with provision for
	indication of associated (forwarding) priority. In the Chicago
	meeting (August 1998), a decision was made that support for explicit
	path setup in LDP will be moved to a separate document. This
	document provides that support and it has been accepted as a working
	document in the Orlando meeting (December 1998).
	This specification proposes an end-to-end setup mechanism of a
	constraint-based routed LSP (CR-LSP) initiated by the ingress LSR.
	We also specify mechanisms to provide means for reservation of
	resources using LDP.
	This document introduce TLVs and procedures that provide support
	for:
	- Strict and Loose Explicit Routing
	- Specification of Traffic Parameters
	- Route Pinning
	- CR-LSP Pre-emption though setup/holding priorities
	- Handling Failures
	- LSPID
	- Resource Class
	Section 2 introduces the various constraints defined in this
	specification. Section 3 outlines the CR-LDP solution. Section 4
	defines the TLVs and procedures used to setup constraint-based
	routed label switched paths. Appendix A provides several examples
	of CR-LSP path setup. Appendix B provides Service Definition
	Examples.
	2. Constraint-based Routing Overview
	Constraint-based routing is a mechanism that supports the Traffic
	Engineering requirements defined in [3]. Explicit Routing is a
	subset of the more general constraint-based routing where the
	constraint is the explicit route (ER). Other constraints are defined
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 4
	to provide a network operator with control over the path taken by an
	LSP. This section is an overview of the various constraints
	supported by this specification.
	Like any other LSP a CR-LSP is a path through an MPLS network. The
	difference is that while other paths are setup solely based on
	information in routing tables or from a management system, the
	constraint-based route is calculated at one point at the edge of
	network based on criteria, including but not limited to routing
	information. The intention is that this functionality shall give
	desired special characteristics to the LSP in order to better
	support the traffic sent over the LSP. The reason for setting up CR-
	LSPs might be that one wants to assign certain bandwidth or other
	Service Class characteristics to the LSP, or that one wants to make
	sure that alternative routes use physically separate paths through
	the network.
	2.1 Strict and Loose Explicit Routes
	An explicit route is represented in a Label Request Message as a
	list of nodes or groups of nodes along the constraint-based route.
	When the CR-LSP is established, all or a subset of the nodes in a
	group may be traversed by the LSP. Certain operations to be
	performed along the path can also be encoded in the constraint-based
	route.
	The capability to specify, in addition to specified nodes, groups of
	nodes, of which a subset will be traversed by the CR-LSP, allows the
	system a significant amount of local flexibility in fulfilling a
	request for a constraint-based route. This allows the generator of
	the constraint-based route to have some degree of imperfect
	information about the details of the path.
	The constraint-based route is encoded as a series of ER-Hops
	contained in a constraint-based route TLV. Each ER-Hop may identify
	a group of nodes in the constraint-based route. A constraint-based
	route is then a path including all of the identified groups of nodes
	in the order in which they appear in the TLV.
	To simplify the discussion, we call each group of nodes an abstract
	node. Thus, we can also say that a constraint-based route is a path
	including all of the abstract nodes, with the specified operations
	occurring along that path.
	2.2 Traffic Characteristics
	The traffic characteristics of a path are described in the Traffic
	Parameters TLV in terms of a peak rate, committed rate, and service
	granularity. The peak and committed rates describe the bandwidth
	constraints of a path while the service granularity can be used to
	specify a constraint on the delay variation that the CR-LDP MPLS
	domain may introduce to a pathÆs traffic.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 5
	2.3 Pre-emption
	CR-LDP signals the resources required by a path on each hop of the
	route. If a route with sufficient resources can not be found,
	existing paths may be rerouted to reallocate resources to the new
	path. This is the process of path pre-emption. Setup and holding
	priorities are used to rank existing paths (holding priority) and
	the new path (setup priority) to determine if the new path can pre-
	empt an existing path.
	The setupPriority of a new CR-LSP and the holdingPriority attributes
	of the existing CR-LSP are used to specify priorities. Signaling a
	higher holding priority express that the path, once it has been
	established, should have a lower chance of being pre-empted.
	Signaling a higher setup priority expresses the expectation that, in
	the case that resource are unavailable, the path is more likely to
	pre-empt other paths. The exact rules determining bumping are an
	aspect of network policy.
	The allocation of setup and holding priority values to paths is an
	aspect of network policy.
	The setup and holding priority values range from zero (0) to seven
	(7). The value zero (0) is the priority assigned to the most
	important path. It is referred to as the highest priority. Seven (7)
	is the priority for the least important path. The use of default
	priority values is an aspect of network policy. The recommended
	default value is (4).
	The setupPriority of a CR-LSP should not be higher (numerically
	less) than its holdingPriority since it might bump an LSP and be
	bumped by the next "equivalentö request.
	2.4 Route Pinning
	Route pinning is applicable to segments of an LSP that are loosely
	routed - i.e. those segments which are specified with a next hop
	with the öLö bit set or where the next hop is an öabstract nodeö. A
	CR-LSP may be setup using route pinning if it is undesirable to
	change the path used by an LSP even when a better next hop becomes
	available at some LSR along the loosely routed portion of the LSP.
	2.5 Resource Class
	The network operator may classify network resources in various ways.
	These classes are also known as "colorsö or "administrative groupsö.
	When a CR-LSP is being established, itÆs necessary to indicate which
	resource classes the CR-LSP can draw from.
	3. Solution Overview
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 6
	CR-LSP over LDP Specification is designed with the following goals:
	1. Meet the requirements outlined in [3] for performing traffic
	engineering and provide a solid foundation for performing more
	general constraint-based routing.
	2. Build on already specified functionality that meets the
	requirements whenever possible. Hence, this specification is
	based on [1].
	3. Keep the solution simple.
	In this document, support for unidirectional point-to-point CR-LSPs
	is specified. Support for point-to-multipoint, multipoint-to-point,
	is for further study (FFS).
	Support for constraint-based routed LSPs in this specification
	depends on the following minimal LDP behaviors as specified in [1]:
	- Use of Basic and/or Extended Discovery Mechanisms.
	- Use of the Label Request Message defined in [1] in downstream on
	demand label advertisement mode with ordered control.
	- Use of the Label Mapping Message defined in [1] in downstream on
	demand mode with ordered control.
	- Use of the Notification Message defined in [1].
	- Use of the Withdraw and Release Messages defined in [1].
	- Use of the Loop Detection (in the case of loosely routed
	segments of a CR-LSP) mechanisms defined in [1].
	In addition, the following functionality is added to whatÆs defined
	in [1]:
	- The Label Request Message used to setup a CR-LSP includes one or
	more CR-TLVs defined in Section 4. For instance, the Label Request
	Message may include the ER-TLV.
	- An LSR implicitly infers ordered control from the existence of
	one or more CR-TLVs in the Label Request Message. This means that
	the LSR can still be configured for independent control for LSPs
	established as a result of dynamic routing. However, when a Label
	Request Message includes one or more of the CR-TLVs, then ordered
	control is used to setup the CR-LSP. Note that this is also true
	for the loosely routed parts of a CR-LSP.
	- New status codes are defined to handle error notification for
	failure of established paths specified in the CR-TLVs.
	Optional TLVs MUST be implemented to be compliant with the protocol.
	However, they are optionally carried in the CR-LDP messages to
	signal certain characteristics of the CR-LSP being established or
	modified.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 7
	Examples of CR-LSP establishment are given in Appendix A to
	illustrate how the mechanisms described in this draft work.
	3.1 Required Messages and TLVs
	Any Messages, TLVs, and procedures not defined explicitly in this
	document are defined in the LDP Specification [1]. The reader can
	use [7] as an informational document about the state transitions,
	which relate to CR-LDP messages.
	The following subsections are meant as a cross-reference to the [1]
	document and indication of additional functionality beyond whatÆs
	defined in [1] where necessary.
	Note that use of the Status TLV is not limited to Notification
	messages as specified in Section 3.4.6 of [1]. A message other than
	a Notification message may carry a Status TLV as an Optional
	Parameter. When a message other than a Notification carries a
	Status TLV the U-bit of the Status TLV should be set to 1 to
	indicate that the receiver should silently discard the TLV if
	unprepared to handle it.
	3.2 Label Request Message
	The Label Request Message is as defined in 3.5.8 of [1] with the
	following modifications (required only if any of the CR-TLVs is
	included in the Label Request Message):
	- The Label Request Message MUST include a single FEC-TLV element.
	The CR-LSP FEC TLV element SHOULD be used. However, the other FEC-
	TLVs defined in [1] MAY be used instead for certain applications.
	- The Optional Parameters TLV includes the definition of any of
	the Constraint-based TLVs specified in Section 4.
	- The Procedures to handle the Label Request Message are augmented
	by the procedures for processing of the CR-TLVs as defined in
	Section 4.
	The encoding for the CR-LDP Label Request Message is 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|0| Label Request (0x0401) | Message Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Message ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| FEC TLV |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| LSPID TLV (CR-LDP, mandatory) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 8
	| ER-TLV (CR-LDP, optional) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Traffic TLV (CR-LDP, optional) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Pinning TLV (CR-LDP, optional) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Resource Class TLV (CR-LDP, optional) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Pre-emption TLV (CR-LDP, optional) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	3.3 Label Mapping Message
	The Label Mapping Message is as defined in 3.5.7 of [1] with the
	following modifications:
	- The Label Mapping Message MUST include a single Label-TLV.
	- The Label Mapping Message Procedures are limited to downstream
	on demand ordered control mode.
	A Mapping message is transmitted by a downstream LSR to an upstream
	LSR under one of the following conditions:
	1. The LSR is the egress end of the CR-LSP and an upstream
	mapping has been requested.
	2. The LSR received a mapping from its downstream next hop LSR
	for an CR-LSP for which an upstream request is still pending.
	The encoding for the CR-LDP Label Mapping Message is 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|0| Label Mapping (0x0400) | Message Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Message ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| FEC TLV |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Label TLV |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Label Request Message ID TLV |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| LSPID TLV (CR-LDP, optional) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Traffic TLV (CR-LDP, optional) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	3.4 Notification Message
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 9
	The Notification Message is as defined in Section 3.5.1 of [1] and
	the Status TLV encoding is as defined in Section 3.4.6 of [1].
	Establishment of an CR-LSP may fail for a variety of reasons. All
	such failures are considered advisory conditions and they are
	signaled by the Notification Message.
	Notification Messages carry Status TLVs to specify events being
	signaled. New status codes are defined in Section 4.11 to signal
	error notifications associated with the establishment of a CR-LSP
	and the processing of the CR-TLV.
	The Notification Message MAY carry the LSPID TLV of the
	corresponding CR-LSP.
	Notification Messages MUST be forwarded toward the LSR originating
	the Label Request at each hop and at any time that procedures in
	this specification - or in [1] - specify sending of a Notification
	Message in response to a Label Request Message.
	The encoding of the notification message is 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|0| Notification (0x0001) | Message Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Message ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Status (TLV) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Optional Parameters |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	3.5 Release , Withdraw, and Abort Messages
	The Label Release , Label Withdraw, and Label Abort Request Messages
	are used as specified in [1]. These messages may also carry the
	LSPID TLV.
	4. Protocol Specification
	The Label Request Message defined in [1] MUST carry the LSPID TLV
	and MAY carry one or more of the optional Constraint-based Routing
	TLVs (CR-TLVs) defined in this section. If needed, other constraints
	can be supported later through the definition of new TLVs. In this
	specification, the following TLVs are defined:
	- Explicit Route TLV
	- Explicit Route Hop TLV
	- Traffic Parameters TLV
	- Preemption TLV
	- LSPID TLV
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 10
	- Route Pinning TLV
	- Resource Class TLV
	- CR-LSP FEC TLV
	4.1 Explicit Route TLV (ER-TLV)
	The ER-TLV is an object that specifies the path to be taken by the
	LSP being established. It is composed of one or more Explicit Route
	Hop TLVs (ER-Hop TLVs) defined in Section 4.2.
	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|0| Type = 0x0800 | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ER-Hop TLV 1 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ER-Hop TLV 2 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	~ ............ ~
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| ER-Hop TLV n |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the ER-TLV Type =
	0x0800.
	Length
	Specifies the length of the value field in bytes.
	ER-Hop TLVs
	One or more ER-Hop TLVs defined in Section 4.2.
	4.2 Explicit Route Hop TLV (ER-Hop TLV)
	The contents of an ER-TLV are a series of variable length ER-Hop
	TLVs.
	A node receiving a label request message including an ER-Hop type
	that is not supported MUST not progress the label request message to
	the downstream LSR and MUST send back a "No Routeö Notification
	Message.
	Each ER-Hop TLV has the form:
	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|0| Type | Length |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|L| Content // |
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 11
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	ER-Hop Type
	A fourteen-bit field carrying the type of the ER-Hop contents.
	Currently defined values are:
	Value Type
	------ ------------------------
	0x0801 IPv4 prefix
	0x0802 IPv6 prefix
	0x0803 Autonomous system number
	0x0804 LSPID
	Length
	Specifies the length of the value field in bytes.
	L bit
	The L bit in the ER-Hop is a one-bit attribute. If the L bit
	is set, then the value of the attribute is "loose.ö Otherwise,
	the value of the attribute is "strict.ö For brevity, we say
	that if the value of the ER-Hop attribute is loose then it is a
	"loose ER-Hop.ö Otherwise, itÆs a "strict ER-Hop.ö Further,
	we say that the abstract node of a strict or loose ER-Hop is a
	strict or a loose node, respectively. Loose and strict nodes
	are always interpreted relative to their prior abstract nodes.
	The path between a strict node and its prior node MUST include
	only network nodes from the strict node and its prior abstract
	node.
	The path between a loose node and its prior node MAY include
	other network nodes, which are not part of the strict node or
	its prior abstract node.
	Contents
	A variable length field containing a node or abstract node
	which is one of the consecutive nodes that make up the
	explicitly routed LSP.
	4.3 Traffic Parameters TLV
	The following sections describe the CR-LSP Traffic Parameters. The
	required characteristics of a CR-LSP are expressed by the Traffic
	Parameter values.
	A Traffic Parameters TLV, is used to signal the Traffic Parameter
	values. The Traffic Parameters are defined in the subsequent
	sections.
	The Traffic Parameters TLV contains a Flags field, a Frequency, a
	Weight, and the five Traffic Parameters PDR, PBS, CDR, CBS, EBS.
	The Traffic Parameters TLV is shown below:
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 12
	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|0| Type = 0x0810 | Length = 24 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Flags | Frequency | Reserved | Weight |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Peak Data Rate (PDR) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Peak Burst Size (PBS) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Committed Data Rate (CDR) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Committed Burst Size (CBS) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Excess Burst Size (EBS) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the Traffic
	Parameters TLV Type = 0x0810.
	Length
	Specifies the length of the value field in bytes = 24.
	Flags
	The Flags field is shown below:
	+--+--+--+--+--+--+--+--+
	| Res |F6|F5|F4|F3|F2|F1|
	+--+--+--+--+--+--+--+--+
	Res - These bits are reserved.
	Zero on transmission.
	Ignored on receipt.
	F1 - Corresponds to the PDR.
	F2 - Corresponds to the PBS.
	F3 - Corresponds to the CDR.
	F4 - Corresponds to the CBS.
	F5 - Corresponds to the EBS.
	F6 - Corresponds to the Weight.
	Each flag Fi is a Negotiable Flag corresponding to a Traffic
	Parameter. The Negotiable Flag value zero denotes NotNegotiable
	and value one denotes Negotiable.
	Frequency
	The Frequency field is coded as an 8 bit unsigned integer with
	the following code points defined:
	0- Unspecified
	1- Frequent
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 13
	2- VeryFrequent
	3-255 - Reserved
	Reserved - Zero on transmission. Ignored on receipt.
	Weight
	An 8 bit unsigned integer indicating the weight of the CR-LSP.
	Valid weight values are from 1 to 255. The value 0 means that
	weight is not applicable for the CR-LSP.
	Traffic Parameters
	Each Traffic Parameter is encoded as a 32-bit IEEE single-
	precision floating-point number. A value of positive infinity
	is represented as an IEEE single-precision floating-point
	number with an exponent of all ones (255) and a sign and
	mantissa of all zeros. The values PDR and CDR are in units of
	bytes per second. The values PBS, CBS and EBS are in units of
	bytes.
	The value of PDR MUST be greater than or equal to the value of
	CDR in a correctly encoded Traffic Parameters TLV.
	4.3.1 Semantics
	4.3.1.1 Frequency
	The Frequency specifies at what granularity the CDR allocated to the
	CR-LSP is made available. The value VeryFrequent means that the
	available rate should average at least the CDR when measured over
	any time interval equal to or longer than the shortest packet time
	at the CDR. The value Frequent means that the available rate should
	average at least the CDR when measured over any time interval equal
	to or longer than a small number of shortest packet times at the
	CDR.
	The value Unspecified means that the CDR MAY be provided at any
	granularity.
	4.3.1.2 Peak Rate
	The Peak Rate defines the maximum rate at which traffic SHOULD be
	sent to the CR-LSP. The Peak Rate is useful for the purpose of
	resource allocation. If resource allocation within the MPLS domain
	depends on the Peak Rate value then it should be enforced at the
	ingress to the MPLS domain.
	The Peak Rate is defined in terms of the two Traffic Parameters PDR
	and PBS, see section 4.3.1.5 below.
	4.3.1.3 Committed Rate
	The Committed Rate defines the rate that the MPLS domain commits to
	be available to the CR-LSP.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 14
	The Committed Rate is defined in terms of the two Traffic Parameters
	CDR and CBS, see section 4.3.1.6 below.
	4.3.1.4 Excess Burst Size
	The Excess Burst Size may be used at the edge of an MPLS domain for
	the purpose of traffic conditioning. The EBS MAY be used to measure
	the extent by which the traffic sent on a CR-LSP exceeds the
	committed rate.
	The possible traffic conditioning actions, such as passing, marking
	or dropping, are specific to the MPLS domain.
	The Excess Burst Size is defined together with the Committed Rate,
	see section 4.3.1.6 below.
	4.3.1.5 Peak Rate Token Bucket
	The Peak Rate of a CR-LSP is specified in terms of a token bucket P
	with token rate PDR and maximum token bucket size PBS.
	The token bucket P is initially (at time 0) full, i.e., the token
	count Tp(0) = PBS. Thereafter, the token count Tp, if less than
	PBS, is incremented by one PDR times per second. When a packet of
	size B bytes arrives at time t, the following happens:
	- If Tp(t)-B >= 0, the packet is not in excess of the peak rate
	and Tp is decremented by B down to the minimum value of 0, else
	- the packet is in excess of the peak rate and Tp is not
	decremented.
	Note that according to the above definition, a positive infinite
	value of either PDR or PBS implies that arriving packets are never
	in excess of the peak rate.
	The actual implementation of an LSR doesnÆt need to be modeled
	according to the above formal token bucket specification.
	4.3.1.6 Committed Data Rate Token Bucket
	The committed rate of a CR-LSP is specified in terms of a token
	bucket C with rate CDR. The extent by which the offered rate
	exceeds the committed rate MAY be measured in terms of another token
	bucket E, which also operates at rate CDR. The maximum size of the
	token bucket C is CBS and the maximum size of the token bucket E is
	EBS.
	The token buckets C and E are initially (at time 0) full, i.e., the
	token count Tc(0) = CBS and the token count Te(0) = EBS.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 15
	Thereafter, the token counts Tc and Te are updated CDR times per
	second as follows:
	- If Tc is less than CBS, Tc is incremented by one, else
	- if Te is less then EBS, Te is incremented by one, else
	neither Tc nor Te is incremented.
	When a packet of size B bytes arrives at time t, the following
	happens:
	- If Tc(t)-B >= 0, the packet is not in excess of the Committed
	Rate and Tc is decremented by B down to the minimum value of 0,
	else
	- if Te(t)-B >= 0, the packet is in excess of the Committed rate
	but is not in excess of the EBS and Te is decremented by B down to
	the minimum value of 0, else
	- the packet is in excess of both the Committed Rate and the EBS
	and neither Tc nor Te is decremented.
	Note that according to the above specification, a CDR value of
	positive infinity implies that arriving packets are never in excess
	of either the Committed Rate or EBS. A positive infinite value of
	either CBS or EBS implies that the respective limit cannot be
	exceeded.
	The actual implementation of an LSR doesnÆt need to be modeled
	according to the above formal specification.
	4.3.1.7 Weight
	The weight determines the CR-LSPÆs relative share of the possible
	excess bandwidth above its committed rate. The definition of
	"relative shareö is MPLS domain specific.
	4.3.2 Procedures
	4.3.2.1 Label Request Message
	If an LSR receives an incorrectly encoded Traffic Parameters TLV in
	which the value of PDR is less than the value of CDR then it MUST
	send a Notification Message including the Status code "Traffic
	Parameters Unavailableö to the upstream LSR from which it received
	the erroneous message.
	If a Traffic Parameter is indicated as Negotiable in the Label
	Request Message by the corresponding Negotiable Flag then an LSR MAY
	replace the Traffic Parameter value with a smaller value.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 16
	If the Weight is indicated as Negotiable in the Label Request
	Message by the corresponding Negotiable Flag then an LSR may replace
	the Weight value with a lower value (down to 0).
	If, after possible Traffic Parameter negotiation, an LSR can support
	the CR-LSP Traffic Parameters then the LSR MUST reserve the
	corresponding resources for the CR-LSP.
	If, after possible Traffic Parameter negotiation, an LSR cannot
	support the CR-LSP Traffic Parameters then the LSR MUST send a
	Notification Message that contains the "Resource Unavailableö status
	code.
	4.3.2.2 Label Mapping Message
	If an LSR receives an incorrectly encoded Traffic Parameters TLV in
	which the value of PDR is less than the value of CDR then it MUST
	send a Label Release message containing the Status code "Traffic
	Parameters Unavailableö to the LSR from which it received the
	erroneous message. In addition, the LSP should send a Notification
	Message upstream with the status code "Label Request Abortedö.
	If the negotiation flag was set in the label request message, the
	egress LSR MUST include the (possibly negotiated) Traffic Parameters
	and Weight in the Label Mapping message.
	The Traffic Parameters and the Weight in a Label Mapping message
	MUST be forwarded unchanged.
	An LSR SHOULD adjust the resources that it reserved for a CR-LSP
	when it receives a Label Mapping Message if the Traffic Parameters
	differ from those in the corresponding Label Request Message.
	4.3.2.3 Notification Message
	If an LSR receives a Notification Message for a CR-LSP, it SHOULD
	release any resources that it possibly had reserved for the CR-LSP.
	In addition, on receiving a Notification Message from a Downstream
	LSR that is associated with a Label Request from an upstream LSR,
	the local LSR MUST propagate the Notification message using the
	procedures in [1].
	4.4 Preemption TLV
	The defualt value of the setup and holding priorities should be in
	the middle of the range (e.g., 4) so that this feature can be turned
	on gradually in an operational network by increasing or decreasing
	the priority starting at the middle of the range.
	Since the Preemption TLV is an optional TLV, LSPs that are setup
	without an explicitly signaled preemption TLV SHOULD be treated as
	LSPs with the default setup and holding priorities (e.g., 4).
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 17
	When an established LSP is preempted, the LSR that initiates the
	preemption sends a Withdraw Message upstream and a Release Message
	downstream.
	When an LSP in the process of being established (outstanding Label
	Request without getting a Label Mapping back) is preempted, the LSR
	that initiates the preemption, sends a Notification Message upstream
	and an Abort Message downstream.
	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|0| Type = 0x0820 | Length = 4 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| SetPrio | HoldPrio | Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the Preemption-TLV
	Type = 0x0820.
	Length
	Specifies the length of the value field in bytes = 4.
	Reserved
	Zero on transmission. Ignored on receipt.
	SetPrio
	A SetupPriority of value zero (0) is the priority assigned to
	the most important path. It is referred to as the highest
	priority. Seven (7) is the priority for the least important
	path. The higher the setup priority, the more paths CR-LDP can
	bump to set up the path. The default value should be 4.
	HoldPrio
	A HoldingPriority of value zero (0) is the priority assigned to
	the most important path. It is referred to as the highest
	priority. Seven (7) is the priority for the least important
	path. The default value should be 4.
	The higher the holding priority, the less likely it is for CR-
	LDP to reallocate its bandwidth to a new path.
	4.5 LSPID TLV
	LSPID is a unique identifier of a CR-LSP within an MPLS network.
	The LSPID is composed of the ingress LSR Router ID (or any of its
	own Ipv4 addresses) and a Locally unique CR-LSP ID to that LSR.
	The LSPID is useful in network management, in CR-LSP repair, and in
	using an already established CR-LSP as a hop in an ER-TLV.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 18
	An "action indicator flagö is carried in the LSPID TLV. This "action
	indicator flagö indicates explicitly the action that should be taken
	if the LSP already exists on the LSR receiving the message.
	After a CR-LSP is set up, its bandwidth reservation may need to be
	changed by the network operator, due to the new requirements for the
	traffic carried on that CR-LSP. The "action indicator flagö is used
	indicate the need to modify the bandwidth and possibly other
	parameters of an established CR-LSP without service interruption.
	This feature has application in dynamic network resources management
	where traffic of different priorities and service classes is
	involved.
	The procedure for the code point "modifyö is defined in [8]. The
	procedures for other flags are FFS.
	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|0| Type = 0x0821 | Length = 4 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Reserved |ActFlg | Local CR-LSP ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Ingress LSR Router ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the LSPID-TLV
	Type = 0x0821.
	Length
	Specifies the length of the value field in bytes = 4.
	ActFlg
	Action Indicator Flag: A 4-bit field that indicates explicitly
	the action that should be taken if the LSP already exists on
	the LSR receiving the message. A set of indicator code points
	is proposed as follows:
	0000: indicates initial LSP setup
	0001: indicates modify LSP
	Reserved
	Zero on transmission. Ignored on receipt.
	Local CR-LSP ID
	The Local LSP ID is an identifier of the CR-LSP locally unique
	within the Ingress LSR originating the CR-LSP.
	Ingress LSR Router ID
	An LSR may use any of its own IPv4 addresses in this field.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 19
	4.6 Resource Class (Color) TLV
	The Resource Class as defined in [3] is used to specify which links
	are acceptable by this CR-LSP. This information allows for the
	networkÆs topology to be pruned.
	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|0| Type = 0x0822 | Length = 4 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| RsCls |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the ResCls-TLV Type
	= 0x0822.
	Length
	Specifies the length of the value field in bytes = 4.
	RsCls
	The Resource Class bit mask indicating which of the 32
	"administrative groupsö or "colorsö of links the CR-LSP can
	traverse.
	4.7 ER-Hop semantics
	4.7.1. ER-Hop 1: The IPv4 prefix
	The abstract node represented by this ER-Hop is the set of nodes,
	which have an IP address, which lies within this prefix. Note that
	a prefix length of 32 indicates a single IPv4 node.
	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|0| Type = 0x0801 | Length = 8 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|L| Reserved | PreLen |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| IPv4 Address (4 bytes) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the ER-Hop 1, IPv4
	Address, Type = 0x0801
	Length
	Specifies the length of the value field in bytes = 8.
	L Bit
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 20
	Set to indicate Loose hop.
	Cleared to indicate a strict hop.
	Reserved
	Zero on transmission. Ignored on receipt.
	PreLen
	Prefix Length 1-32
	IP Address
	A four-byte field indicating the IP Address.
	4.7.2. ER-Hop 2: The IPv6 address
	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|0| 0x0802 | Length = 20 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|L| Reserved | PreLen |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| IPV6 address |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| IPV6 address (continued) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| IPV6 address (continued) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| IPV6 address (continued) |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the ER-Hop 2, IPv6
	Address, Type = 0x0802
	Length
	Specifies the length of the value field in bytes = 20.
	L Bit
	Set to indicate Loose hop.
	Cleared to indicate a strict hop.
	Reserved
	Zero on transmission. Ignored on receipt.
	PreLen
	Prefix Length 1-128
	IPv6 address
	A 128-bit unicast host address.
	4.7.3. ER-Hop 3: The autonomous system number
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 21
	The abstract node represented by this ER-Hop is the set of nodes
	belonging to the autonomous system.
	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|0| 0x0803 | Length = 4 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|L| Reserved | AS Number |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the ER-Hop 3, AS
	Number, Type = 0x0803
	Length
	Specifies the length of the value field in bytes = 4.
	L Bit
	Set to indicate Loose hop.
	Cleared to indicate a strict hop.
	Reserved
	Zero on transmission. Ignored on receipt.
	AS Number
	Autonomous System number
	4.7.4. ER-Hop 4: LSPID
	The LSPID is used to identify the tunnel ingress point as the next
	hop in the ER. This ER-Hop allows for stacking new CR-LSPs within an
	already established CR-LSP. It also allows for splicing the CR-LSP
	being established with an existing CR-LSP.
	If an LSPID Hop is the last ER-Hop in an ER-TLV, than the LSR may
	splice the CR-LSP of the incoming Label Request to the CR-LSP that
	currently exists with this LSPID. This is useful, for example, at
	the point at which a Label Request used for local repair arrives at
	the next ER-Hop after the loosely specified CR-LSP segment. Use of
	the LSPID Hop in this scenario eliminates the need for ER-Hops to
	keep the entire remaining ER-TLV at each LSR that is at either
	(upstream or downstream) end of a loosely specified CR-LSP segment
	as part of its state information. This is due to the fact that the
	upstream LSR needs only to keep the next ER-Hop and the LSPID and
	the downstream LSR needs only to keep the LSPID in order for each
	end to be able to recognize that the same LSP is being identified.
	If the LSPID Hop is not the last hop in an ER-TLV, the LSR must
	remove the LSP-ID Hop and forward the remaining ER-TLV in a Label
	Request message using an LDP session established with the LSR that
	is the specified CR-LSP's egress. That LSR will continue processing
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 22
	of the CR-LSP Label Request Message. The result is a tunneled, or
	stacked, CR-LSP.
	To support labels negotiated for tunneled CR-LSP segments, an LDP
	session is required [1] between tunnel end points - possibly using
	the existing CR-LSP. Use of the existence of the CR-LSP in lieu of
	a session, or other possible session-less approaches, is FFS.
	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|0| 0x0804 | Length = 8 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|L| Reserved | Local LSPID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| Ingress LSR Router ID |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the ER-Hop 4, LSPID,
	Type = 0x0804
	Length
	Specifies the length of the value field in bytes = 8.
	L Bit
	Set to indicate Loose hop.
	Cleared to indicate a strict hop.
	Reserved
	Zero on transmission. Ignored on receipt.
	Local LSPID
	A 2 byte field indicating the LSPID which is unique with
	reference to its Ingress LSR.
	Ingress LSR Router ID
	An LSR may use any of its own IPv4 addresses in this field.
	4.8. Processing of the Explicit Route TLV
	4.8.1. Selection of the next hop
	A Label Request Message containing an explicit route TLV must
	determine the next hop for this path. Selection of this next hop
	may involve a selection from a set of possible alternatives. The
	mechanism for making a selection from this set is implementation
	dependent and is outside of the scope of this specification.
	Selection of particular paths is also outside of the scope of this
	specification, but it is assumed that each node will make a best
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 23
	effort attempt to determine a loop-free path. Note that such best
	efforts may be overridden by local policy.
	To determine the next hop for the path, a node performs the
	following steps:
	1. The node receiving the Label Request Message must first
	evaluate the first ER-Hop. If the L bit is not set in the first
	ER-Hop and if the node is not part of the abstract node described
	by the first ER-Hop, it has received the message in error, and
	should return a "Bad Initial ER-Hopö error. If the L bit is set
	and the local node is not part of the abstract node described by
	the first ER-Hop, the node selects a next hop that is along the
	path to the abstract node described by the first ER-Hop. If there
	is no first ER-Hop, the message is also in error and the system
	should return a "Bad Explicit Routing TLVö error using a
	Notification Message sent upstream.
	2. If there is no second ER-Hop, this indicates the end of the
	explicit route. The explicit route TLV should be removed from the
	Label Request Message. This node may or may not be the end of
	the LSP. Processing continues with section 4.8.2, where a new
	explicit route TLV may be added to the Label Request Message.
	3. If the node is also a part of the abstract node described by
	the second ER-Hop, then the node deletes the first ER-Hop and
	continues processing with step 2, above. Note that this makes
	the second ER-Hop into the first ER-Hop of the next iteration.
	4. The node determines if it is topologically adjacent to the
	abstract node described by the second ER-Hop. If so, the node
	selects a particular next hop which is a member of the abstract
	node. The node then deletes the first ER-Hop and continues
	processing with section 4.8.2.
	5. Next, the node selects a next hop within the abstract node of
	the first ER-Hop that is along the path to the abstract node of
	the second ER-Hop. If no such path exists then there are two
	cases:
	5.a If the second ER-Hop is a strict ER-Hop, then there is
	an error and the node should return a "Bad Strict Nodeö
	error.
	5.b Otherwise, if the second ER-Hop is a loose ER-Hop, then
	the node selects any next hop that is along the path to the
	next abstract node. If no path exists within the MPLS
	domain, then there is an error, and the node should return a
	"Bad loose nodeö error.
	6. Finally, the node replaces the first ER-Hop with any ER-Hop
	that denotes an abstract node containing the next hop. This is
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 24
	necessary so that when the explicit route is received by the next
	hop, it will be accepted.
	7. Progress the Label Request Message to the next hop.
	4.8.2. Adding ER-Hops to the explicit route TLV
	After selecting a next hop, the node may alter the explicit route in
	the following ways.
	If, as part of executing the algorithm in section 4.8.1, the
	explicit route TLV is removed, the node may add a new explicit route
	TLV.
	Otherwise, if the node is a member of the abstract node for the
	first ER-Hop, then a series of ER-Hops may be inserted before the
	first ER-Hop or may replace the first ER-Hop. Each ER-Hop in this
	series must denote an abstract node that is a subset of the current
	abstract node.
	Alternately, if the first ER-Hop is a loose ER-Hop, an arbitrary
	series of ER-Hops may be inserted prior to the first ER-Hop.
	4.9 Route Pinning TLV
	Section 2.4 describes the use of route pinning. The encoding of the
	Route Pinning TLV is 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|0|0| Type = 0x0823 | Length = 4 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|P| Reserved |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the Pinning-TLV
	Type = 0x0823
	Length
	Specifies the length of the value field in bytes = 4.
	P Bit
	The P bit is set to 1 to indicate that route pinning is
	requested.
	The P bit is set to 0 to indicate that route pinning is not
	requested
	Reserved
	Zero on transmission. Ignored on receipt.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 25
	4.10 CR-LSP FEC Element
	A new FEC element is introduced in this specification to support CR-
	LSPs. A FEC TLV containing a FEC of Element type CR-LSP (0x04) is a
	CR-LSP FEC TLV. The CR-LSP FEC Element is an opaque FEC to be used
	only in Messages of CR-LSPs.
	A single FEC element MUST be included in the Label Request Message.
	The FEC Element SHOULD be the CR-LSP FEC Element. However, one of
	the other FEC elements (Type=0x01, 0x02, 0x03) defined in [1] MAY be
	in CR-LDP messages instead of the CR-LSP FEC Element for certain
	applications. A FEC TLV containing a FEC of Element type CR-LSP
	(0x04) is a CR-LSP FEC TLV.
	FEC Element Type Value
	Type name
	CR-LSP 0x04 No value; i.e., 0 value octets;
	The CR-LSP FEC TLV encoding is 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
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	|0|0| Type = 0x0100 | Length = 1 |
	+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
	| CR-LSP (4) |
	+-+-+-+-+-+-+-+-+
	Type
	A fourteen-bit field carrying the value of the FEC TLV
	Type = 0x0100
	Length
	Specifies the length of the value field in bytes = 1.
	CR-LSP FEC Element Type
	0x04
	5. IANA Considerations
	CR-LDP defines the following name spaces, which require management:
	- TLV types.
	- FEC types.
	- Status codes.
	The following sections provide guidelines for managing these name
	spaces.
	5.1 TLV Type Name Space
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 26
	RFC 3036 [1] defines the LDP TLV name space. This document further
	subdivides the range of RFC 3036 from that TLV space for TLVs
	associated with the CR-LDP in the range 0x0800 - 0x08FF.
	Following the policies outlined in [IANA], TLV types in this range
	are allocated through an IETF Consensus action.
	Initial values for this range are specified in the following table:
	TLV Type
	-------------------------------------- ----------
	Explicite Route TLV 0x0800
	Ipv4 Prefix ER-Hop TLV 0x0801
	Ipv6 Prefix ER-Hop TLV 0x0802
	Autonomous System Number ER-Hop TLV 0x0803
	LSP-ID ER-Hop TLV 0x0804
	Traffic Parameters TLV 0x0810
	Preemption TLV 0x0820
	LSPID TLV 0x0821
	Resource Class TLV 0x0822
	Route Pinning TLV 0x0823
	5.2 FEC Type Name Space
	RFC 3036 defines the FEC Type TLV name space. This document further
	subdivides the range of RFC 3036 from that TLV space for TLVs
	associated with the CR-LDP in the range 100 - 116.
	Following the policies outlined in [IANA], TLV types in this range
	are allocated through an IETF Consensus action.
	Initial values for this range are specified in the follwing table:
	FEC Element TLV Type
	-------------------------------------- ----------
	CR-LSP FEC Element TLV 0x0100
	5.3 Status Code Space
	RFC 3036 defines the Status Code name space. This document further
	subdivides the range of RFC 3036 from that TLV space for TLVs
	associated with the CR-LDP in the range 0x44000000 - 0x440000FF.
	Following the policies outlined in [IANA], TLV types in this range
	are allocated through an IETF Consensus action.
	Initial values for this range are specified in the follwing table:
	Status Code Type
	-------------------------------------- ----------
	Bad Explicit Routing TLV Error 0x44000001
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 27
	Bad Strict Node Error 0x44000002
	Bad Loose Node Error 0x44000003
	Bad Initial ER-Hop Error 0x44000004
	Resource Unavailable 0x44000005
	Traffic Parameters Unavailable 0x44000006
	LSP Preempted 0x44000007
	Modify Request Not Supported 0x44000008
	Setup Abort (Label Request Aborted in [1]) 0x04000015
	6. Security
	CR-LDP inherits the same security mechanism described in Section 4.0
	of [1] to protect against the introduction of spoofed TCP segments
	into LDP session connection streams.
	7. Acknowledgments
	The messages used to signal the CR-LSP setup are based on the work
	done by the [1] team.
	The authors would also like to acknowledge the careful review and
	comments of Ken Hayward, Greg Wright, Geetha Brown, Brian Williams,
	Paul Beaubien, Matthew Yuen, Liam Casey, Ankur Anand, Adrian Farrel.
	8. Intellectual Property Consideration
	The IETF has been notified of intellectual property rights claimed
	in regard to some or all of the specification contained in this
	document. For more information consult the online list of claimed
	rights.
	9. References
	1 Andersson et. al., "Label Distribution Protocol Specification"
	RFC 3036, January 2001.
	2 Rosen et. al., "Multiprotocol Label Switching Architecture",
	RFC 3031, January 2001.
	3 Awduche et. al., "Requirements for Traffic Engineering Over
	MPLS", RFC 2702, September 1999.
	4 Gleeson, et. al., "A Framework for IP Based Virtual Private
	Networks", RFC 2764, February 2000.
	5 B. Jamoussi, et. al., ôApplicability Statement for CR-LDPö, work
	in progress, (draft-ietf-mpls-crldp-applic-01), June 2000.
	6 S. Bradner, "Key words for use in RFCs to Indicate Requirement
	Levelsö, RFC 2119, March 1997.
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 28
	7 L. Wu, et. al., "LDP State Machine", work in progress,
	(draft-ietf-mpls-ldp-state-03), January 2000.
	8 J. Ash, et. al., "LSP Modification Using CR-LDP", work in
	progress, (draft-ietf-mpls-crlsp-modify-02), October 2000.
	10. AuthorÆs Addresses
	Osama S. Aboul-Magd Loa Andersson
	Nortel Networks Nortel Networks
	P O Box 3511 Station C S:t Eriksgatan 115
	Ottawa, ON K1Y 4H7 PO Box 6701
	Canada 113 85 Stockholm
	Phone: +1 613 763-5827 Tel: +46 8 508 835 00
	Osama@nortelnetworks.com Fax: +46 8 508 835 01
	Loa_andersson@nortelnetworks.com
	Peter Ashwood-Smith Ross Callon
	Nortel Networks Juniper Networks
	P O Box 3511 Station C 1194 North Mathilda Avenue,
	Ottawa, ON K1Y 4H7 Sunnyvale, CA 94089
	Canada 978-692-6724
	Phone: +1 613 763-4534 rcallon@juniper.net
	Petera@nortelnetworks.com
	Ram Dantu Paul Doolan
	Cisco Systems Ennovate Networks
	17919 Waterview Parkway 330 Codman Hill Rd
	Dallas, 75252 Marlborough MA 01719
	+1 469 255 0716 Phone: 978-263-2002
	rdantu@cisco.com Pdoolan@ennovatenetworks.com
	Nancy Feldman Andre Fredette
	IBM Research PhotonEx Corporation
	30 Saw Mill River Road 135 South Road
	Hawthorne, NY 10532 Bedford, MA 01730
	Phone: 914-784-3254 email: fredette@photonex.com
	Nkf@us.ibm.com phone: 781-275-8500
	Eric Gray Joel M. Halpern
	600 Federal Drive Longitude Systems, Inc.
	Andover, MA 01810 1319 Shepard Road
	Phone: (978) 689-1610 Sterling, VA 20164
	eric.gray@sandburst.com 703-433-0808 x207
	joel@longsys.com
	Juha Heinanen Fiffi Hellstrand
	Telia Finland, Inc. Nortel Networks
	Myyrmaentie 2 S:t Eriksgatan 115
	01600 VANTAA PO Box 6701, 113 85 Stockholm
	Finland Sweden
	Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 29
	Tel: +358 41 500 4808 +46705593687
	Jh@telia.fi fiffi@nortelnetworks.com
	Bilel Jamoussi Timothy E. Kilty
	Nortel Networks Corp. Newbridge Networks, Inc.
	600 Technology Park Drive 5 Corporate Drive
	Billerica, MA 01821 Andover, MA 01810
	USA USA
	Phone: +1 978 288-4506 phone: 978 691-4656
	Jamoussi@nortelnetworks.com tkilty@northchurch.net
	Andrew G. Malis Muckai K Girish
	Vivace Networks Atoga Systems
	2730 Orchard Parkway 49026 Milmont Drive
	San Jose, CA 95134 Fremont, CA 94538
	Andy.Malis@vivacenetworks.com E-mail: muckai@atoga.com
	Tel: +1 408 383 7223
	Fax: +1 408 904 4748
	Kenneth Sundell Pasi Vaananen
	Nortel Networks Nokia Telecommunications
	S:t Eriksgatan 115 3 Burlington Woods Drive,
	PO Box 6701 Burlington, MA 01803
	113 85 Stockholm Phone: +1-781-238-4981
	Tel: +46 8 508 835 00 pasi.vaananen@nokia.com
	Fax: +46 8 508 835 01
	Ksundell@nortelnetworks.com
	Tom Worster Liwen Wu
	Ennovate Networks Cisco Systems
	60 Codman Hill Rd 250 Apollo Drive
	Boxborough Chelmsford, MA. 01824
	MA 01719 Tel: 978-244-3087.
	tworster@ennovatenetworks.com liwwu@cisco.com
	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 30
	Appendix A: CR-LSP Establishment Examples
	A.1 Strict Explicit Route Example
	This appendix provides an example for the setup of a strictly routed
	CR-LSP. In this example, a specific node represents each abstract
	node.
	The sample network used here is a four node network with two edge
	LSRs and two core LSRs as follows:
	abc
	LSR1------LSR2------LSR3------LSR4
	LSR1 generates a Label Request Message as described in Section 3.1
	of this draft and sends it to LSR2. This message includes the CR-
	TLV.
	A vector of three ER-Hop TLVs <a, b, c> composes the ER-TLV.
	The ER-Hop TLVs used in this example are of type 0x0801 (IPv4
	prefix) with a prefix length of 32. Hence, each ER-Hop TLV
	identifies a specific node as opposed to a group of nodes.
	At LSR2, the following processing of the ER-TLV per Section 4.8.1 of
	this draft takes place:
	1. The node LSR2 is part of the abstract node described by the
	first hop <a>. Therefore, the first step passes the test. Go
	to step 2.
	2. There is a second ER-Hop, <b>. Go to step 3.
	3. LSR2 is not part of the abstract node described by the
	second ER-Hop <b>. Go to Step 4.
	4. LSR2 determines that it is topologically adjacent to the
	abstract node described by the second ER-Hop <b>. LSR2 selects
	a next hop (LSR3) which is the abstract node. LSR2 deletes the
	first ER-Hop <a> from the ER-TLV, which now becomes <b, c>.
	Processing continues with Section 4.8.2.
	At LSR2, the following processing of Section 4.8.2 takes place:
	Executing algorithm 4.8.1 did not result in the removal of the ER-
	TLV.
	Also, LSR2 is not a member of the abstract node described by the
	first ER-Hop <b>.
	Finally, the first ER-Hop <b> is a strict hop.
	Therefore, processing section 4.8.2 does not result in the insertion
	of new ER-Hops. The selection of the next hop has been already done
	is step 4 of Section 4.8.1 and the processing of the ER-TLV is
	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 31
	completed at LSR2. In this case, the Label Request Message including
	the ER-TLV <b, c> is progressed by LSR2 to LSR3.
	At LSR3, a similar processing to the ER-TLV takes place except that
	the incoming ER-TLV = <b, c> and the outgoing ER-TLV is <c>.
	At LSR4, the following processing of section 4.8.1 takes place:
	1. The node LSR4 is part of the abstract node described by the
	first hop <c>. Therefore, the first step passes the test. Go to
	step 2.
	2. There is no second ER-Hop, this indicates the end of the CR-
	LSP. The ER-TLV is removed from the Label Request Message.
	Processing continues with Section 4.8.2.
	At LSR4, the following processing of Section 4.8.2 takes place:
	Executing algorithm 4.8.1 resulted in the removal of the ER-TLV.
	LSR4 does not add a new ER-TLV.
	Therefore, processing section 4.8.2 does not result in the insertion
	of new ER-Hops. This indicates the end of the CR-LSP and the
	processing of the ER-TLV is completed at LSR4.
	At LSR4, processing of Section 3.2 is invoked. The first condition
	is satisfied (LSR4 is the egress end of the CR-LSP and upstream
	mapping has been requested). Therefore, a Label Mapping Message is
	generated by LSR4 and sent to LSR3.
	At LSR3, the processing of Section 3.2 is invoked. The second
	condition is satisfied (LSR3 received a mapping from its downstream
	next hop LSR4 for a CR-LSP for which an upstream request is still
	pending). Therefore, a Label Mapping Message is generated by LSR3
	and sent to LSR2.
	At LSR2, a similar processing to LSR 3 takes place and a Label
	Mapping Message is sent back to LSR1, which completes the end-to-end
	CR-LSP setup.
	A.2 Node Groups and Specific Nodes Example
	A request at ingress LSR to setup a CR-LSP might originate from a
	management system or an application, the details are implementation
	specific.
	The ingress LSR uses information provided by the management system
	or the application and possibly also information from the routing
	database to calculate the explicit route and to create the Label
	Request Message.
	The Label request message carries together with other necessary
	information an ER-TLV defining the explicitly routed path. In our
	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 32
	example the list of hops in the ER-Hop TLV is supposed to contain an
	abstract node representing a group of nodes, an abstract node
	representing a specific node, another abstract node representing a
	group of nodes, and an abstract node representing a specific egress
	point.
	In--{Group 1}--{Specific A}--{Group 2}--{Specific Out: B}
	The ER-TLV contains four ER-Hop TLVs:
	1. An ER-Hop TLV that specifies a group of LSR valid for the
	first abstract node representing a group of nodes (Group 1).
	2. An ER-Hop TLV that indicates the specific node (Node A).
	3. An ER-Hop TLV that specifies a group of LSRs valid for the
	second abstract node representing a group of nodes (Group 2).
	4. An ER-Hop TLV that indicates the specific egress point for
	the CR-LSP (Node B).
	All the ER-Hop TLVs are strictly routed nodes.
	The setup procedure for this CR-LSP works as follows:
	1. The ingress node sends the Label Request Message to a node
	that is a member the group of nodes indicated in the first ER-
	Hop TLV, following normal routing for the specific node (A).
	2. The node that receives the message identifies itself as part
	of the group indicated in the first ER-Hop TLV, and that it is
	not the specific node (A) in the second. Further it realizes
	that the specific node (A) is not one of its next hops.
	3. It keeps the ER-Hop TLVs intact and sends a Label Request
	Message to another node that is part of the group indicated in
	the first ER-Hop TLV (Group 1), following normal routing for
	the specific node (A).
	4. The node that receives the message identifies itself as part
	of the group indicated in the first ER-Hop TLV, and that it is
	not the specific node (A) in the second ER-Hop TLV. Further it
	realizes that the specific node (A) is one of its next hops.
	5. It removes the first ER-Hop TLVs and sends a Label Request
	Message to the specific node (A).
	6. The specific node (A) recognizes itself in the first ER-Hop
	TLV. Removes the specific ER-Hop TLV.
	7. It sends a Label Request Message to a node that is a member
	of the group (Group 2) indicated in the ER-Hop TLV.
	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 33
	8. The node that receives the message identifies itself as part
	of the group indicated in the first ER-Hop TLV, further it
	realizes that the specific egress node (B) is one of its next
	hops.
	9. It sends a Label Request Message to the specific egress node
	(B).
	10. The specific egress node (B) recognizes itself as the
	egress for the CR-LSP, it returns a Label Mapping Message, that
	will traverse the same path as the Label Request Message in the
	opposite direction.
	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 34
	Appendix B. QoS Service Examples
	B.1 Service Examples
	Construction of an end-to-end service is the result of the rules
	enforced at the edge and the treatment that packets receive at the
	network nodes. The rules define the traffic conditioning actions
	that are implemented at the edge and they include policing with
	pass, mark, and drop capabilities. The edge rules are expected tobe
	defined by the mutual agreements between the service providers and
	their customers and they will constitute an essential part of the
	SLA. Therefore edge rules are not included in the signaling
	protocol.
	Packet treatment at a network node is usually referred to as the
	local behavior. Local behavior could be specified in many ways. One
	example for local behavior specification is the service frequency
	introduced in section 4.3.2.1, together with the resource
	reservation rules implemented at the nodes.
	Edge rules and local behaviors can be viewed as the main building
	blocks for the end-to-end service construction. The following table
	illustrates the applicability of the building block approach for
	constructing different services including those defined for ATM.
	Service PDR PBS CDR CBS EBS Service Conditioning
	Examples Frequency Action
	DS S S =PDR =PBS 0 Frequent drop>PDR
	TS S S S S 0 Unspecified drop>PDR,PBS
	mark>CDR,CBS
	BE inf inf inf inf 0 Unspecified -
	FRS S S CIR ~B_C ~B_E Unspecified drop>PDR,PBS
	mark>CDR,CBS,EBS
	ATM-CBR PCR CDVT =PCR =CDVT 0 VeryFrequent drop>PCR
	ATM-VBR.3(rt) PCR CDVT SCR MBS 0 Frequent drop>PCR
	mark>SCR,MBS
	ATM-VBR.3(nrt) PCR CDVT SCR MBS 0 Unspecified drop>PCR
	mark>SCR,MBS
	ATM-UBR PCR CDVT - - 0 Unspecified drop>PCR
	ATM-GFR.1 PCR CDVT MCR MBS 0 Unspecified drop>PCR
	ATM-GFR.2 PCR CDVT MCR MBS 0 Unspecified drop>PCR
	mark>MCR,MFS
	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 35
	int-serv-CL p m r b 0 Frequent drop>p
	drop>r,b
	S= User specified
	In the above table, the DS refers to a delay sensitive service where
	the network commits to deliver with high probability user datagrams
	at a rate of PDR with minimum delay and delay requirements.
	Datagrams in excess of PDR will be discarded.
	The TS refers to a generic throughput sensitive service where the
	network commits to deliver with high probability user datagrams at a
	rate of at least CDR. The user may transmit at a rate higher than
	CDR but datagrams in excess of CDR would have a lower probability of
	being delivered.
	The BE is the best effort service and it implies that there are no
	expected service guarantees from the network.
	B.2 Establishing CR-LSP Supporting Real-Time Applications
	In this scenario the customer needs to establish an LSP for		Title: Constraint-Based LSP Setup using LDP
	supporting real-time applications such as voice and video. The		Author(s): B. Jamoussi, Editor, L. Andersson,
	Delay-sensitive (DS) service is requested in this case.		R. Callon, R. Dantu, L. Wu, P. Doolan, T. Worster,
			N. Feldman, A. Fredette, M. Girish, E. Gray,
			J. Heinanen, T. Kilty, A. Malis
			Status: Standards Track
			Date: January 2002
			Mailbox: Jamoussi@nortelnetworks.com,
			loa.andersson@utfors.se,
			rcallon@juniper.net,
			rdantu@netrake.com, liwwu@cisco.com,
			pdoolan@acm.org,
			fsb@thefsb.org, Nkf@us.ibm.com,
			afredette@charter.net, muckai@atoga.com,
			eric.gray@sandburst.com,
			jh@song.fi, tim-kilty@mediaone.net,
			Andy.Malis@vivacenetworks.com
			Pages: 42
			Characters: 87591
			Updates/Obsoletes/SeeAlso: None
	The first step is the specification of the traffic parameters in the		I-D Tag: draft-ietf-mpls-cr-ldp-06.txt
	signaling message. The two parameters of interest to the DS service
	are the PDR and the PBS and the user based on his requirements
	specifies their values. Since all the traffic parameters are
	included in the signaling message, appropriate values must be
	assigned to all of them. For DS service, the CDR and the CBS values
	are set equal to the PDR and the PBS respectively. An indication of
	whether the parameter values are subject to negotiation is flagged.
	The transport characteristics of the DS service require Frequent		URL: ftp://ftp.rfc-editor.org/in-notes/rfc3212.txt
	frequency to be requested to reflect the real-time delay
	requirements of the service.
	In addition to the transport characteristics, both the network		This document specifies mechanisms and TLVs (Type/Length/Value) for
	provider and the customer need to agree on the actions enforced at		support of CR-LSPs (constraint-based routed Label Switched Path)
	the edge. The specification of those actions is expected to be a		using LDP (Label Distribution Protocol).
	part of the service level agreement (SLA) negotiation and is not
	included in the signaling protocol. For DS service, the edge action
	is to drop packets that exceed the PDR and the PBS specifications.
	The signaling message will be sent in the direction of the ER path
	and the LSP is established following the normal LDP procedures. Each
	LSR applies its admission control rules. If sufficient resources are
	not available and the parameter values are subject to negotiation,
	then the LSR could negotiate down the PDR, the PBS, or both.
	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 36		This specification proposes an end-to-end setup mechanism of a CR-LSP
	The new parameter values are echoed back in the Label Mapping		initiated by the ingress LSR (Label Switching Router). We also
	Message. LSRs might need to re-adjust their resource reservations		specify mechanisms to provide means for reservation of resources
	based on the new traffic parameter values.		using LDP.
	B.3 Establishing CR-LSP Supporting Delay Insensitive Applications		This document is a product of the Multiprotocol Label Switching
			Working Group of the IETF.
	In this example we assume that a throughput sensitive (TS) service		This is now a Proposed Standard Protocol.
	is requested. For resource allocation the user assigns values for
	PDR, PBS, CDR, and CBS. The negotiation flag is set if the traffic
	parameters are subject to negotiation.
	Since the service is delay insensitive by definition, the
	Unspecified frequency is signaled to indicate that the service
	frequency is not an issue.
	Similar to the previous example, the edge actions are not subject		This document specifies an Internet standards track protocol for
	for signaling and are specified in the service level agreement		the Internet community, and requests discussion and suggestions
	between the user and the network provider.		for improvements. Please refer to the current edition of the
			"Internet Official Protocol Standards" (STD 1) for the
			standardization state and status of this protocol. Distribution
			of this memo is unlimited.
	For TS service, the edge rules might include marking to indicate		This announcement is sent to the IETF list and the RFC-DIST list.
	high discard precedence values for all packets that exceed CDR and		Requests to be added to or deleted from the IETF distribution list
	the CBS. The edge rules will also include dropping of packets that		should be sent to IETF-REQUEST@IETF.ORG. Requests to be
	conform to neither PDR nor PBS.		added to or deleted from the RFC-DIST distribution list should
			be sent to RFC-DIST-REQUEST@RFC-EDITOR.ORG.
	Each LSR of the LSP is expected to run its admission control rules		Details on obtaining RFCs via FTP or EMAIL may be obtained by sending
	and negotiate traffic parameters down if sufficient resources do not		an EMAIL message to rfc-info@RFC-EDITOR.ORG with the message body
	exist. The new parameter values are echoed back in the Label Mapping		help: ways_to_get_rfcs. For example:
	Message. LSRs might need to re-adjust their resources based on the
	new traffic parameter values.
	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 37		To: rfc-info@RFC-EDITOR.ORG
	Full Copyright Statement		Subject: getting rfcs
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	Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 38		Requests for special distribution should be addressed to either the
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