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1 MPLS Working Group Bilel Jamoussi, Editor
2 Internet Draft Nortel Networks Corp.
3 Expiration Date: August 2001
5 O. Aboul-Magd, L. Andersson, P. Ashwood-Smith,
6 F. Hellstrand, K. Sundell, Nortel Networks Corp.
7 R. Callon, Juniper Networks.
8 R. Dantu, L. Wu, Cisco Systems
9 P. Doolan, T. Worster, Ennovate Networks Corp.
10 N. Feldman, IBM Corp.
11 A. Fredette, PhotonEx Corp.
12 M. Girish, Atoga Systems
13 E. Gray, Sandburst
14 J. Halpern, Longitude Systems, Inc.
15 J. Heinanen, Telia Finland
16 T. Kilty, Newbridge Networks, Inc.
17 A. Malis, Vivace Networks
18 P. Vaananen, Nokia Telecommunications
20 February 2001
22 Constraint-Based LSP Setup using LDP
24 draft-ietf-mpls-cr-ldp-05.txt
26 Status of this Memo
28 This document is an Internet-Draft and is in full conformance with
29 all provisions of Section 10 of RFC2026.
31 Internet-Drafts are working documents of the Internet Engineering
32 Task Force (IETF), its areas, and its working groups. Note that
33 other groups may also distribute working documents as Internet-
34 Drafts.
36 Internet-Drafts are draft documents valid for a maximum of six
37 months and may be updated, replaced, or obsoleted by other documents
38 at any time. It is inappropriate to use Internet-Drafts as reference
39 material or to cite them other than as "work in progress.�
41 The list of current Internet-Drafts can be accessed at
42 http://www.ietf.org/ietf/1id-abstracts.txt
44 The list of Internet-Draft Shadow Directories can be accessed at
45 http://www.ietf.org/shadow.html.
47 Abstract
49 Label Distribution Protocol (LDP) is defined in [1] for distribution
50 of labels inside one MPLS domain. One of the most important
51 services that may be offered using MPLS in general and LDP in
52 particular is support for constraint-based routing of traffic across
54 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 1
55 the routed network. Constraint-based routing offers the opportunity
56 to extend the information used to setup paths beyond what is
57 available for the routing protocol. For instance, an LSP can be
58 setup based on explicit route constraints, QoS constraints, and
59 other constraints. Constraint-based routing (CR) is a mechanism used
60 to meet Traffic Engineering requirements that have been proposed by,
61 [2] and [3]. These requirements may be met by extending LDP for
62 support of constraint-based routed label switched paths (CR-LSPs).
63 Other uses for CR-LSPs include MPLS-based VPNs [4]. More information
64 about the applicability of CR-LDP can be found in [5].
66 This draft specifies mechanisms and TLVs for support of CR-LSPs
67 using LDP.
69 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
70 NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL"
71 in this document are to be interpreted as described in RFC 2119 [6].
73 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 2
74 Table of Contents
76 1. Introduction....................................................4
77 2. Constraint-based Routing Overview...............................4
78 2.1 Strict and Loose Explicit Routes...............................5
79 2.2 Traffic Characteristics........................................5
80 2.3 Pre-emption....................................................6
81 2.4 Route Pinning..................................................6
82 2.5 Resource Class.................................................6
83 3. Solution Overview...............................................6
84 3.1 Required Messages and TLVs.....................................8
85 3.2 Label Request Message..........................................8
86 3.3 Label Mapping Message..........................................9
87 3.4 Notification Message...........................................9
88 3.5 Release , Withdraw, and Abort Messages........................10
89 4. Protocol Specification.........................................10
90 4.1 Explicit Route TLV (ER-TLV)...................................11
91 4.2 Explicit Route Hop TLV (ER-Hop TLV)...........................11
92 4.3 Traffic Parameters TLV........................................12
93 4.3.1 Semantics...................................................14
94 4.3.1.1 Frequency.................................................14
95 4.3.1.2 Peak Rate.................................................14
96 4.3.1.3 Committed Rate............................................14
97 4.3.1.4 Excess Burst Size.........................................15
98 4.3.1.5 Peak Rate Token Bucket....................................15
99 4.3.1.6 Committed Data Rate Token Bucket..........................15
100 4.3.1.7 Weight....................................................16
101 4.3.2 Procedures..................................................16
102 4.3.2.1 Label Request Message.....................................16
103 4.3.2.2 Label Mapping Message.....................................17
104 4.3.2.3 Notification Message......................................17
105 4.4 Preemption TLV................................................17
106 4.5 LSPID TLV.....................................................18
107 4.6 Resource Class (Color) TLV....................................20
108 4.7 ER-Hop semantics..............................................20
109 4.7.1. ER-Hop 1: The IPv4 prefix..................................20
110 4.7.2. ER-Hop 2: The IPv6 address.................................21
111 4.7.3. ER-Hop 3: The autonomous system number....................21
112 4.7.4. ER-Hop 4: LSPID............................................22
113 4.8. Processing of the Explicit Route TLV.........................23
114 4.8.1. Selection of the next hop..................................23
115 4.8.2. Adding ER-Hops to the explicit route TLV...................25
116 4.9 Route Pinning TLV.............................................25
117 4.10 CR-LSP FEC Element...........................................26
118 5. IANA Considerations............................................26
119 5.1 TLV Type Name Space...........................................26
120 5.2 FEC Type Name Space...........................................27
121 5.3 Status Code Space.............................................27
122 6. Security.......................................................28
123 7. Acknowledgments................................................28
124 8. Intellectual Property Consideration............................28
126 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 3
127 9. References.....................................................28
128 10. Author�s Addresses............................................29
129 Appendix A: CR-LSP Establishment Examples.........................31
130 A.1 Strict Explicit Route Example.................................31
131 A.2 Node Groups and Specific Nodes Example........................32
132 Appendix B. QoS Service Examples..................................35
133 B.1 Service Examples..............................................35
134 B.2 Establishing CR-LSP Supporting Real-Time Applications.........36
135 B.3 Establishing CR-LSP Supporting Delay Insensitive Applications.37
137 1. Introduction
139 The need for constraint-based routing (CR) in MPLS has been explored
140 elsewhere [2], and [3]. Explicit routing is a subset of the more
141 general constraint-based routing function. At the MPLS WG meeting
142 held during the Washington IETF (December 1997) there was consensus
143 that LDP should support explicit routing of LSPs with provision for
144 indication of associated (forwarding) priority. In the Chicago
145 meeting (August 1998), a decision was made that support for explicit
146 path setup in LDP will be moved to a separate document. This
147 document provides that support and it has been accepted as a working
148 document in the Orlando meeting (December 1998).
150 This specification proposes an end-to-end setup mechanism of a
151 constraint-based routed LSP (CR-LSP) initiated by the ingress LSR.
152 We also specify mechanisms to provide means for reservation of
153 resources using LDP.
155 This document introduce TLVs and procedures that provide support
156 for:
157 - Strict and Loose Explicit Routing
158 - Specification of Traffic Parameters
159 - Route Pinning
160 - CR-LSP Pre-emption though setup/holding priorities
161 - Handling Failures
162 - LSPID
163 - Resource Class
165 Section 2 introduces the various constraints defined in this
166 specification. Section 3 outlines the CR-LDP solution. Section 4
167 defines the TLVs and procedures used to setup constraint-based
168 routed label switched paths. Appendix A provides several examples
169 of CR-LSP path setup. Appendix B provides Service Definition
170 Examples.
172 2. Constraint-based Routing Overview
174 Constraint-based routing is a mechanism that supports the Traffic
175 Engineering requirements defined in [3]. Explicit Routing is a
176 subset of the more general constraint-based routing where the
177 constraint is the explicit route (ER). Other constraints are defined
179 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 4
180 to provide a network operator with control over the path taken by an
181 LSP. This section is an overview of the various constraints
182 supported by this specification.
184 Like any other LSP a CR-LSP is a path through an MPLS network. The
185 difference is that while other paths are setup solely based on
186 information in routing tables or from a management system, the
187 constraint-based route is calculated at one point at the edge of
188 network based on criteria, including but not limited to routing
189 information. The intention is that this functionality shall give
190 desired special characteristics to the LSP in order to better
191 support the traffic sent over the LSP. The reason for setting up CR-
192 LSPs might be that one wants to assign certain bandwidth or other
193 Service Class characteristics to the LSP, or that one wants to make
194 sure that alternative routes use physically separate paths through
195 the network.
197 2.1 Strict and Loose Explicit Routes
199 An explicit route is represented in a Label Request Message as a
200 list of nodes or groups of nodes along the constraint-based route.
201 When the CR-LSP is established, all or a subset of the nodes in a
202 group may be traversed by the LSP. Certain operations to be
203 performed along the path can also be encoded in the constraint-based
204 route.
206 The capability to specify, in addition to specified nodes, groups of
207 nodes, of which a subset will be traversed by the CR-LSP, allows the
208 system a significant amount of local flexibility in fulfilling a
209 request for a constraint-based route. This allows the generator of
210 the constraint-based route to have some degree of imperfect
211 information about the details of the path.
213 The constraint-based route is encoded as a series of ER-Hops
214 contained in a constraint-based route TLV. Each ER-Hop may identify
215 a group of nodes in the constraint-based route. A constraint-based
216 route is then a path including all of the identified groups of nodes
217 in the order in which they appear in the TLV.
219 To simplify the discussion, we call each group of nodes an abstract
220 node. Thus, we can also say that a constraint-based route is a path
221 including all of the abstract nodes, with the specified operations
222 occurring along that path.
224 2.2 Traffic Characteristics
226 The traffic characteristics of a path are described in the Traffic
227 Parameters TLV in terms of a peak rate, committed rate, and service
228 granularity. The peak and committed rates describe the bandwidth
229 constraints of a path while the service granularity can be used to
230 specify a constraint on the delay variation that the CR-LDP MPLS
231 domain may introduce to a path�s traffic.
233 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 5
234 2.3 Pre-emption
236 CR-LDP signals the resources required by a path on each hop of the
237 route. If a route with sufficient resources can not be found,
238 existing paths may be rerouted to reallocate resources to the new
239 path. This is the process of path pre-emption. Setup and holding
240 priorities are used to rank existing paths (holding priority) and
241 the new path (setup priority) to determine if the new path can pre-
242 empt an existing path.
244 The setupPriority of a new CR-LSP and the holdingPriority attributes
245 of the existing CR-LSP are used to specify priorities. Signaling a
246 higher holding priority express that the path, once it has been
247 established, should have a lower chance of being pre-empted.
248 Signaling a higher setup priority expresses the expectation that, in
249 the case that resource are unavailable, the path is more likely to
250 pre-empt other paths. The exact rules determining bumping are an
251 aspect of network policy.
253 The allocation of setup and holding priority values to paths is an
254 aspect of network policy.
256 The setup and holding priority values range from zero (0) to seven
257 (7). The value zero (0) is the priority assigned to the most
258 important path. It is referred to as the highest priority. Seven (7)
259 is the priority for the least important path. The use of default
260 priority values is an aspect of network policy. The recommended
261 default value is (4).
263 The setupPriority of a CR-LSP should not be higher (numerically
264 less) than its holdingPriority since it might bump an LSP and be
265 bumped by the next "equivalent� request.
267 2.4 Route Pinning
269 Route pinning is applicable to segments of an LSP that are loosely
270 routed - i.e. those segments which are specified with a next hop
271 with the �L� bit set or where the next hop is an �abstract node�. A
272 CR-LSP may be setup using route pinning if it is undesirable to
273 change the path used by an LSP even when a better next hop becomes
274 available at some LSR along the loosely routed portion of the LSP.
276 2.5 Resource Class
278 The network operator may classify network resources in various ways.
279 These classes are also known as "colors� or "administrative groups�.
280 When a CR-LSP is being established, it�s necessary to indicate which
281 resource classes the CR-LSP can draw from.
283 3. Solution Overview
285 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 6
286 CR-LSP over LDP Specification is designed with the following goals:
288 1. Meet the requirements outlined in [3] for performing traffic
289 engineering and provide a solid foundation for performing more
290 general constraint-based routing.
292 2. Build on already specified functionality that meets the
293 requirements whenever possible. Hence, this specification is
294 based on [1].
296 3. Keep the solution simple.
298 In this document, support for unidirectional point-to-point CR-LSPs
299 is specified. Support for point-to-multipoint, multipoint-to-point,
300 is for further study (FFS).
302 Support for constraint-based routed LSPs in this specification
303 depends on the following minimal LDP behaviors as specified in [1]:
305 - Use of Basic and/or Extended Discovery Mechanisms.
306 - Use of the Label Request Message defined in [1] in downstream on
307 demand label advertisement mode with ordered control.
308 - Use of the Label Mapping Message defined in [1] in downstream on
309 demand mode with ordered control.
310 - Use of the Notification Message defined in [1].
311 - Use of the Withdraw and Release Messages defined in [1].
312 - Use of the Loop Detection (in the case of loosely routed
313 segments of a CR-LSP) mechanisms defined in [1].
315 In addition, the following functionality is added to what�s defined
316 in [1]:
318 - The Label Request Message used to setup a CR-LSP includes one or
319 more CR-TLVs defined in Section 4. For instance, the Label Request
320 Message may include the ER-TLV.
322 - An LSR implicitly infers ordered control from the existence of
323 one or more CR-TLVs in the Label Request Message. This means that
324 the LSR can still be configured for independent control for LSPs
325 established as a result of dynamic routing. However, when a Label
326 Request Message includes one or more of the CR-TLVs, then ordered
327 control is used to setup the CR-LSP. Note that this is also true
328 for the loosely routed parts of a CR-LSP.
330 - New status codes are defined to handle error notification for
331 failure of established paths specified in the CR-TLVs.
333 Optional TLVs MUST be implemented to be compliant with the protocol.
334 However, they are optionally carried in the CR-LDP messages to
335 signal certain characteristics of the CR-LSP being established or
336 modified.
338 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 7
339 Examples of CR-LSP establishment are given in Appendix A to
340 illustrate how the mechanisms described in this draft work.
342 3.1 Required Messages and TLVs
344 Any Messages, TLVs, and procedures not defined explicitly in this
345 document are defined in the LDP Specification [1]. The reader can
346 use [7] as an informational document about the state transitions,
347 which relate to CR-LDP messages.
349 The following subsections are meant as a cross-reference to the [1]
350 document and indication of additional functionality beyond what�s
351 defined in [1] where necessary.
353 Note that use of the Status TLV is not limited to Notification
354 messages as specified in Section 3.4.6 of [1]. A message other than
355 a Notification message may carry a Status TLV as an Optional
356 Parameter. When a message other than a Notification carries a
357 Status TLV the U-bit of the Status TLV should be set to 1 to
358 indicate that the receiver should silently discard the TLV if
359 unprepared to handle it.
361 3.2 Label Request Message
363 The Label Request Message is as defined in 3.5.8 of [1] with the
364 following modifications (required only if any of the CR-TLVs is
365 included in the Label Request Message):
367 - The Label Request Message MUST include a single FEC-TLV element.
368 The CR-LSP FEC TLV element SHOULD be used. However, the other FEC-
369 TLVs defined in [1] MAY be used instead for certain applications.
371 - The Optional Parameters TLV includes the definition of any of
372 the Constraint-based TLVs specified in Section 4.
374 - The Procedures to handle the Label Request Message are augmented
375 by the procedures for processing of the CR-TLVs as defined in
376 Section 4.
378 The encoding for the CR-LDP Label Request Message is as follows:
380 0 1 2 3
381 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
382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
383 |0| Label Request (0x0401) | Message Length |
384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
385 | Message ID |
386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
387 | FEC TLV |
388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
389 | LSPID TLV (CR-LDP, mandatory) |
390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
392 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 8
393 | ER-TLV (CR-LDP, optional) |
394 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
395 | Traffic TLV (CR-LDP, optional) |
396 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
397 | Pinning TLV (CR-LDP, optional) |
398 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
399 | Resource Class TLV (CR-LDP, optional) |
400 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
401 | Pre-emption TLV (CR-LDP, optional) |
402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
404 3.3 Label Mapping Message
406 The Label Mapping Message is as defined in 3.5.7 of [1] with the
407 following modifications:
409 - The Label Mapping Message MUST include a single Label-TLV.
411 - The Label Mapping Message Procedures are limited to downstream
412 on demand ordered control mode.
414 A Mapping message is transmitted by a downstream LSR to an upstream
415 LSR under one of the following conditions:
417 1. The LSR is the egress end of the CR-LSP and an upstream
418 mapping has been requested.
420 2. The LSR received a mapping from its downstream next hop LSR
421 for an CR-LSP for which an upstream request is still pending.
423 The encoding for the CR-LDP Label Mapping Message is as follows:
425 0 1 2 3
426 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
427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
428 |0| Label Mapping (0x0400) | Message Length |
429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
430 | Message ID |
431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
432 | FEC TLV |
433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
434 | Label TLV |
435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
436 | Label Request Message ID TLV |
437 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
438 | LSPID TLV (CR-LDP, optional) |
439 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
440 | Traffic TLV (CR-LDP, optional) |
441 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
443 3.4 Notification Message
445 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 9
446 The Notification Message is as defined in Section 3.5.1 of [1] and
447 the Status TLV encoding is as defined in Section 3.4.6 of [1].
448 Establishment of an CR-LSP may fail for a variety of reasons. All
449 such failures are considered advisory conditions and they are
450 signaled by the Notification Message.
452 Notification Messages carry Status TLVs to specify events being
453 signaled. New status codes are defined in Section 4.11 to signal
454 error notifications associated with the establishment of a CR-LSP
455 and the processing of the CR-TLV.
457 The Notification Message MAY carry the LSPID TLV of the
458 corresponding CR-LSP.
460 Notification Messages MUST be forwarded toward the LSR originating
461 the Label Request at each hop and at any time that procedures in
462 this specification - or in [1] - specify sending of a Notification
463 Message in response to a Label Request Message.
465 The encoding of the notification message is as follows:
467 0 1 2 3
468 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
469 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
470 |0| Notification (0x0001) | Message Length |
471 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
472 | Message ID |
473 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
474 | Status (TLV) |
475 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
476 | Optional Parameters |
477 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
479 3.5 Release , Withdraw, and Abort Messages
481 The Label Release , Label Withdraw, and Label Abort Request Messages
482 are used as specified in [1]. These messages may also carry the
483 LSPID TLV.
485 4. Protocol Specification
487 The Label Request Message defined in [1] MUST carry the LSPID TLV
488 and MAY carry one or more of the optional Constraint-based Routing
489 TLVs (CR-TLVs) defined in this section. If needed, other constraints
490 can be supported later through the definition of new TLVs. In this
491 specification, the following TLVs are defined:
493 - Explicit Route TLV
494 - Explicit Route Hop TLV
495 - Traffic Parameters TLV
496 - Preemption TLV
497 - LSPID TLV
499 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 10
500 - Route Pinning TLV
501 - Resource Class TLV
502 - CR-LSP FEC TLV
504 4.1 Explicit Route TLV (ER-TLV)
506 The ER-TLV is an object that specifies the path to be taken by the
507 LSP being established. It is composed of one or more Explicit Route
508 Hop TLVs (ER-Hop TLVs) defined in Section 4.2.
510 0 1 2 3
511 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
512 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
513 |0|0| Type = 0x0800 | Length |
514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
515 | ER-Hop TLV 1 |
516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
517 | ER-Hop TLV 2 |
518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
519 ~ ............ ~
520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
521 | ER-Hop TLV n |
522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
524 Type
525 A fourteen-bit field carrying the value of the ER-TLV Type =
526 0x0800.
528 Length
529 Specifies the length of the value field in bytes.
531 ER-Hop TLVs
532 One or more ER-Hop TLVs defined in Section 4.2.
534 4.2 Explicit Route Hop TLV (ER-Hop TLV)
536 The contents of an ER-TLV are a series of variable length ER-Hop
537 TLVs.
539 A node receiving a label request message including an ER-Hop type
540 that is not supported MUST not progress the label request message to
541 the downstream LSR and MUST send back a "No Route� Notification
542 Message.
544 Each ER-Hop TLV has the form:
546 0 1 2 3
547 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
548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
549 |0|0| Type | Length |
550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
551 |L| Content // |
553 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 11
554 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
556 ER-Hop Type
557 A fourteen-bit field carrying the type of the ER-Hop contents.
558 Currently defined values are:
560 Value Type
561 ------ ------------------------
562 0x0801 IPv4 prefix
563 0x0802 IPv6 prefix
564 0x0803 Autonomous system number
565 0x0804 LSPID
567 Length
568 Specifies the length of the value field in bytes.
570 L bit
571 The L bit in the ER-Hop is a one-bit attribute. If the L bit
572 is set, then the value of the attribute is "loose.� Otherwise,
573 the value of the attribute is "strict.� For brevity, we say
574 that if the value of the ER-Hop attribute is loose then it is a
575 "loose ER-Hop.� Otherwise, it�s a "strict ER-Hop.� Further,
576 we say that the abstract node of a strict or loose ER-Hop is a
577 strict or a loose node, respectively. Loose and strict nodes
578 are always interpreted relative to their prior abstract nodes.
579 The path between a strict node and its prior node MUST include
580 only network nodes from the strict node and its prior abstract
581 node.
583 The path between a loose node and its prior node MAY include
584 other network nodes, which are not part of the strict node or
585 its prior abstract node.
587 Contents
588 A variable length field containing a node or abstract node
589 which is one of the consecutive nodes that make up the
590 explicitly routed LSP.
592 4.3 Traffic Parameters TLV
594 The following sections describe the CR-LSP Traffic Parameters. The
595 required characteristics of a CR-LSP are expressed by the Traffic
596 Parameter values.
598 A Traffic Parameters TLV, is used to signal the Traffic Parameter
599 values. The Traffic Parameters are defined in the subsequent
600 sections.
602 The Traffic Parameters TLV contains a Flags field, a Frequency, a
603 Weight, and the five Traffic Parameters PDR, PBS, CDR, CBS, EBS.
604 The Traffic Parameters TLV is shown below:
606 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 12
607 0 1 2 3
608 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
609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
610 |0|0| Type = 0x0810 | Length = 24 |
611 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
612 | Flags | Frequency | Reserved | Weight |
613 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
614 | Peak Data Rate (PDR) |
615 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
616 | Peak Burst Size (PBS) |
617 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
618 | Committed Data Rate (CDR) |
619 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
620 | Committed Burst Size (CBS) |
621 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
622 | Excess Burst Size (EBS) |
623 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
625 Type
626 A fourteen-bit field carrying the value of the Traffic
627 Parameters TLV Type = 0x0810.
629 Length
630 Specifies the length of the value field in bytes = 24.
632 Flags
633 The Flags field is shown below:
635 +--+--+--+--+--+--+--+--+
636 | Res |F6|F5|F4|F3|F2|F1|
637 +--+--+--+--+--+--+--+--+
639 Res - These bits are reserved.
640 Zero on transmission.
641 Ignored on receipt.
642 F1 - Corresponds to the PDR.
643 F2 - Corresponds to the PBS.
644 F3 - Corresponds to the CDR.
645 F4 - Corresponds to the CBS.
646 F5 - Corresponds to the EBS.
647 F6 - Corresponds to the Weight.
649 Each flag Fi is a Negotiable Flag corresponding to a Traffic
650 Parameter. The Negotiable Flag value zero denotes NotNegotiable
651 and value one denotes Negotiable.
653 Frequency
654 The Frequency field is coded as an 8 bit unsigned integer with
655 the following code points defined:
657 0- Unspecified
658 1- Frequent
660 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 13
661 2- VeryFrequent
662 3-255 - Reserved
663 Reserved - Zero on transmission. Ignored on receipt.
665 Weight
666 An 8 bit unsigned integer indicating the weight of the CR-LSP.
667 Valid weight values are from 1 to 255. The value 0 means that
668 weight is not applicable for the CR-LSP.
670 Traffic Parameters
671 Each Traffic Parameter is encoded as a 32-bit IEEE single-
672 precision floating-point number. A value of positive infinity
673 is represented as an IEEE single-precision floating-point
674 number with an exponent of all ones (255) and a sign and
675 mantissa of all zeros. The values PDR and CDR are in units of
676 bytes per second. The values PBS, CBS and EBS are in units of
677 bytes.
679 The value of PDR MUST be greater than or equal to the value of
680 CDR in a correctly encoded Traffic Parameters TLV.
682 4.3.1 Semantics
684 4.3.1.1 Frequency
686 The Frequency specifies at what granularity the CDR allocated to the
687 CR-LSP is made available. The value VeryFrequent means that the
688 available rate should average at least the CDR when measured over
689 any time interval equal to or longer than the shortest packet time
690 at the CDR. The value Frequent means that the available rate should
691 average at least the CDR when measured over any time interval equal
692 to or longer than a small number of shortest packet times at the
693 CDR.
695 The value Unspecified means that the CDR MAY be provided at any
696 granularity.
698 4.3.1.2 Peak Rate
700 The Peak Rate defines the maximum rate at which traffic SHOULD be
701 sent to the CR-LSP. The Peak Rate is useful for the purpose of
702 resource allocation. If resource allocation within the MPLS domain
703 depends on the Peak Rate value then it should be enforced at the
704 ingress to the MPLS domain.
706 The Peak Rate is defined in terms of the two Traffic Parameters PDR
707 and PBS, see section 4.3.1.5 below.
709 4.3.1.3 Committed Rate
711 The Committed Rate defines the rate that the MPLS domain commits to
712 be available to the CR-LSP.
714 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 14
715 The Committed Rate is defined in terms of the two Traffic Parameters
716 CDR and CBS, see section 4.3.1.6 below.
718 4.3.1.4 Excess Burst Size
720 The Excess Burst Size may be used at the edge of an MPLS domain for
721 the purpose of traffic conditioning. The EBS MAY be used to measure
722 the extent by which the traffic sent on a CR-LSP exceeds the
723 committed rate.
725 The possible traffic conditioning actions, such as passing, marking
726 or dropping, are specific to the MPLS domain.
728 The Excess Burst Size is defined together with the Committed Rate,
729 see section 4.3.1.6 below.
731 4.3.1.5 Peak Rate Token Bucket
733 The Peak Rate of a CR-LSP is specified in terms of a token bucket P
734 with token rate PDR and maximum token bucket size PBS.
736 The token bucket P is initially (at time 0) full, i.e., the token
737 count Tp(0) = PBS. Thereafter, the token count Tp, if less than
738 PBS, is incremented by one PDR times per second. When a packet of
739 size B bytes arrives at time t, the following happens:
741 - If Tp(t)-B >= 0, the packet is not in excess of the peak rate
742 and Tp is decremented by B down to the minimum value of 0, else
744 - the packet is in excess of the peak rate and Tp is not
745 decremented.
747 Note that according to the above definition, a positive infinite
748 value of either PDR or PBS implies that arriving packets are never
749 in excess of the peak rate.
751 The actual implementation of an LSR doesn�t need to be modeled
752 according to the above formal token bucket specification.
754 4.3.1.6 Committed Data Rate Token Bucket
756 The committed rate of a CR-LSP is specified in terms of a token
757 bucket C with rate CDR. The extent by which the offered rate
758 exceeds the committed rate MAY be measured in terms of another token
759 bucket E, which also operates at rate CDR. The maximum size of the
760 token bucket C is CBS and the maximum size of the token bucket E is
761 EBS.
763 The token buckets C and E are initially (at time 0) full, i.e., the
764 token count Tc(0) = CBS and the token count Te(0) = EBS.
766 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 15
767 Thereafter, the token counts Tc and Te are updated CDR times per
768 second as follows:
770 - If Tc is less than CBS, Tc is incremented by one, else
771 - if Te is less then EBS, Te is incremented by one, else
772 neither Tc nor Te is incremented.
774 When a packet of size B bytes arrives at time t, the following
775 happens:
777 - If Tc(t)-B >= 0, the packet is not in excess of the Committed
778 Rate and Tc is decremented by B down to the minimum value of 0,
779 else
781 - if Te(t)-B >= 0, the packet is in excess of the Committed rate
782 but is not in excess of the EBS and Te is decremented by B down to
783 the minimum value of 0, else
785 - the packet is in excess of both the Committed Rate and the EBS
786 and neither Tc nor Te is decremented.
788 Note that according to the above specification, a CDR value of
789 positive infinity implies that arriving packets are never in excess
790 of either the Committed Rate or EBS. A positive infinite value of
791 either CBS or EBS implies that the respective limit cannot be
792 exceeded.
794 The actual implementation of an LSR doesn�t need to be modeled
795 according to the above formal specification.
797 4.3.1.7 Weight
799 The weight determines the CR-LSP�s relative share of the possible
800 excess bandwidth above its committed rate. The definition of
801 "relative share� is MPLS domain specific.
803 4.3.2 Procedures
805 4.3.2.1 Label Request Message
807 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
808 which the value of PDR is less than the value of CDR then it MUST
809 send a Notification Message including the Status code "Traffic
810 Parameters Unavailable� to the upstream LSR from which it received
811 the erroneous message.
813 If a Traffic Parameter is indicated as Negotiable in the Label
814 Request Message by the corresponding Negotiable Flag then an LSR MAY
815 replace the Traffic Parameter value with a smaller value.
817 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 16
818 If the Weight is indicated as Negotiable in the Label Request
819 Message by the corresponding Negotiable Flag then an LSR may replace
820 the Weight value with a lower value (down to 0).
822 If, after possible Traffic Parameter negotiation, an LSR can support
823 the CR-LSP Traffic Parameters then the LSR MUST reserve the
824 corresponding resources for the CR-LSP.
826 If, after possible Traffic Parameter negotiation, an LSR cannot
827 support the CR-LSP Traffic Parameters then the LSR MUST send a
828 Notification Message that contains the "Resource Unavailable� status
829 code.
831 4.3.2.2 Label Mapping Message
833 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
834 which the value of PDR is less than the value of CDR then it MUST
835 send a Label Release message containing the Status code "Traffic
836 Parameters Unavailable� to the LSR from which it received the
837 erroneous message. In addition, the LSP should send a Notification
838 Message upstream with the status code "Label Request Aborted�.
840 If the negotiation flag was set in the label request message, the
841 egress LSR MUST include the (possibly negotiated) Traffic Parameters
842 and Weight in the Label Mapping message.
844 The Traffic Parameters and the Weight in a Label Mapping message
845 MUST be forwarded unchanged.
847 An LSR SHOULD adjust the resources that it reserved for a CR-LSP
848 when it receives a Label Mapping Message if the Traffic Parameters
849 differ from those in the corresponding Label Request Message.
851 4.3.2.3 Notification Message
853 If an LSR receives a Notification Message for a CR-LSP, it SHOULD
854 release any resources that it possibly had reserved for the CR-LSP.
855 In addition, on receiving a Notification Message from a Downstream
856 LSR that is associated with a Label Request from an upstream LSR,
857 the local LSR MUST propagate the Notification message using the
858 procedures in [1].
860 4.4 Preemption TLV
862 The defualt value of the setup and holding priorities should be in
863 the middle of the range (e.g., 4) so that this feature can be turned
864 on gradually in an operational network by increasing or decreasing
865 the priority starting at the middle of the range.
867 Since the Preemption TLV is an optional TLV, LSPs that are setup
868 without an explicitly signaled preemption TLV SHOULD be treated as
869 LSPs with the default setup and holding priorities (e.g., 4).
871 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 17
872 When an established LSP is preempted, the LSR that initiates the
873 preemption sends a Withdraw Message upstream and a Release Message
874 downstream.
876 When an LSP in the process of being established (outstanding Label
877 Request without getting a Label Mapping back) is preempted, the LSR
878 that initiates the preemption, sends a Notification Message upstream
879 and an Abort Message downstream.
881 0 1 2 3
882 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
883 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
884 |0|0| Type = 0x0820 | Length = 4 |
885 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
886 | SetPrio | HoldPrio | Reserved |
887 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
889 Type
890 A fourteen-bit field carrying the value of the Preemption-TLV
891 Type = 0x0820.
893 Length
894 Specifies the length of the value field in bytes = 4.
896 Reserved
897 Zero on transmission. Ignored on receipt.
899 SetPrio
900 A SetupPriority of value zero (0) is the priority assigned to
901 the most important path. It is referred to as the highest
902 priority. Seven (7) is the priority for the least important
903 path. The higher the setup priority, the more paths CR-LDP can
904 bump to set up the path. The default value should be 4.
906 HoldPrio
907 A HoldingPriority of value zero (0) is the priority assigned to
908 the most important path. It is referred to as the highest
909 priority. Seven (7) is the priority for the least important
910 path. The default value should be 4.
911 The higher the holding priority, the less likely it is for CR-
912 LDP to reallocate its bandwidth to a new path.
914 4.5 LSPID TLV
916 LSPID is a unique identifier of a CR-LSP within an MPLS network.
918 The LSPID is composed of the ingress LSR Router ID (or any of its
919 own Ipv4 addresses) and a Locally unique CR-LSP ID to that LSR.
921 The LSPID is useful in network management, in CR-LSP repair, and in
922 using an already established CR-LSP as a hop in an ER-TLV.
924 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 18
925 An "action indicator flag� is carried in the LSPID TLV. This "action
926 indicator flag� indicates explicitly the action that should be taken
927 if the LSP already exists on the LSR receiving the message.
929 After a CR-LSP is set up, its bandwidth reservation may need to be
930 changed by the network operator, due to the new requirements for the
931 traffic carried on that CR-LSP. The "action indicator flag� is used
932 indicate the need to modify the bandwidth and possibly other
933 parameters of an established CR-LSP without service interruption.
934 This feature has application in dynamic network resources management
935 where traffic of different priorities and service classes is
936 involved.
938 The procedure for the code point "modify� is defined in [8]. The
939 procedures for other flags are FFS.
941 0 1 2 3
942 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
943 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
944 |0|0| Type = 0x0821 | Length = 4 |
945 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
946 | Reserved |ActFlg | Local CR-LSP ID |
947 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
948 | Ingress LSR Router ID |
949 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
951 Type
952 A fourteen-bit field carrying the value of the LSPID-TLV
953 Type = 0x0821.
955 Length
956 Specifies the length of the value field in bytes = 4.
958 ActFlg
959 Action Indicator Flag: A 4-bit field that indicates explicitly
960 the action that should be taken if the LSP already exists on
961 the LSR receiving the message. A set of indicator code points
962 is proposed as follows:
964 0000: indicates initial LSP setup
965 0001: indicates modify LSP
966 Reserved
967 Zero on transmission. Ignored on receipt.
969 Local CR-LSP ID
970 The Local LSP ID is an identifier of the CR-LSP locally unique
971 within the Ingress LSR originating the CR-LSP.
973 Ingress LSR Router ID
974 An LSR may use any of its own IPv4 addresses in this field.
976 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 19
977 4.6 Resource Class (Color) TLV
979 The Resource Class as defined in [3] is used to specify which links
980 are acceptable by this CR-LSP. This information allows for the
981 network�s topology to be pruned.
983 0 1 2 3
984 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
985 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
986 |0|0| Type = 0x0822 | Length = 4 |
987 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
988 | RsCls |
989 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
991 Type
992 A fourteen-bit field carrying the value of the ResCls-TLV Type
993 = 0x0822.
995 Length
996 Specifies the length of the value field in bytes = 4.
998 RsCls
999 The Resource Class bit mask indicating which of the 32
1000 "administrative groups� or "colors� of links the CR-LSP can
1001 traverse.
1003 4.7 ER-Hop semantics
1005 4.7.1. ER-Hop 1: The IPv4 prefix
1007 The abstract node represented by this ER-Hop is the set of nodes,
1008 which have an IP address, which lies within this prefix. Note that
1009 a prefix length of 32 indicates a single IPv4 node.
1011 0 1 2 3
1012 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
1013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1014 |0|0| Type = 0x0801 | Length = 8 |
1015 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1016 |L| Reserved | PreLen |
1017 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1018 | IPv4 Address (4 bytes) |
1019 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1021 Type
1022 A fourteen-bit field carrying the value of the ER-Hop 1, IPv4
1023 Address, Type = 0x0801
1025 Length
1026 Specifies the length of the value field in bytes = 8.
1028 L Bit
1030 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 20
1031 Set to indicate Loose hop.
1032 Cleared to indicate a strict hop.
1034 Reserved
1035 Zero on transmission. Ignored on receipt.
1037 PreLen
1038 Prefix Length 1-32
1040 IP Address
1041 A four-byte field indicating the IP Address.
1043 4.7.2. ER-Hop 2: The IPv6 address
1045 0 1 2 3
1046 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
1047 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1048 |0|0| 0x0802 | Length = 20 |
1049 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1050 |L| Reserved | PreLen |
1051 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1052 | IPV6 address |
1053 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1054 | IPV6 address (continued) |
1055 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1056 | IPV6 address (continued) |
1057 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1058 | IPV6 address (continued) |
1059 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1061 Type
1062 A fourteen-bit field carrying the value of the ER-Hop 2, IPv6
1063 Address, Type = 0x0802
1065 Length
1066 Specifies the length of the value field in bytes = 20.
1068 L Bit
1069 Set to indicate Loose hop.
1070 Cleared to indicate a strict hop.
1072 Reserved
1073 Zero on transmission. Ignored on receipt.
1075 PreLen
1076 Prefix Length 1-128
1078 IPv6 address
1079 A 128-bit unicast host address.
1081 4.7.3. ER-Hop 3: The autonomous system number
1083 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 21
1084 The abstract node represented by this ER-Hop is the set of nodes
1085 belonging to the autonomous system.
1087 0 1 2 3
1088 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
1089 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1090 |0|0| 0x0803 | Length = 4 |
1091 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1092 |L| Reserved | AS Number |
1093 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1095 Type
1096 A fourteen-bit field carrying the value of the ER-Hop 3, AS
1097 Number, Type = 0x0803
1099 Length
1100 Specifies the length of the value field in bytes = 4.
1102 L Bit
1103 Set to indicate Loose hop.
1104 Cleared to indicate a strict hop.
1106 Reserved
1107 Zero on transmission. Ignored on receipt.
1109 AS Number
1110 Autonomous System number
1112 4.7.4. ER-Hop 4: LSPID
1114 The LSPID is used to identify the tunnel ingress point as the next
1115 hop in the ER. This ER-Hop allows for stacking new CR-LSPs within an
1116 already established CR-LSP. It also allows for splicing the CR-LSP
1117 being established with an existing CR-LSP.
1119 If an LSPID Hop is the last ER-Hop in an ER-TLV, than the LSR may
1120 splice the CR-LSP of the incoming Label Request to the CR-LSP that
1121 currently exists with this LSPID. This is useful, for example, at
1122 the point at which a Label Request used for local repair arrives at
1123 the next ER-Hop after the loosely specified CR-LSP segment. Use of
1124 the LSPID Hop in this scenario eliminates the need for ER-Hops to
1125 keep the entire remaining ER-TLV at each LSR that is at either
1126 (upstream or downstream) end of a loosely specified CR-LSP segment
1127 as part of its state information. This is due to the fact that the
1128 upstream LSR needs only to keep the next ER-Hop and the LSPID and
1129 the downstream LSR needs only to keep the LSPID in order for each
1130 end to be able to recognize that the same LSP is being identified.
1132 If the LSPID Hop is not the last hop in an ER-TLV, the LSR must
1133 remove the LSP-ID Hop and forward the remaining ER-TLV in a Label
1134 Request message using an LDP session established with the LSR that
1135 is the specified CR-LSP's egress. That LSR will continue processing
1137 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 22
1138 of the CR-LSP Label Request Message. The result is a tunneled, or
1139 stacked, CR-LSP.
1141 To support labels negotiated for tunneled CR-LSP segments, an LDP
1142 session is required [1] between tunnel end points - possibly using
1143 the existing CR-LSP. Use of the existence of the CR-LSP in lieu of
1144 a session, or other possible session-less approaches, is FFS.
1146 0 1 2 3
1147 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
1148 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1149 |0|0| 0x0804 | Length = 8 |
1150 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1151 |L| Reserved | Local LSPID |
1152 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1153 | Ingress LSR Router ID |
1154 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1156 Type
1157 A fourteen-bit field carrying the value of the ER-Hop 4, LSPID,
1158 Type = 0x0804
1160 Length
1161 Specifies the length of the value field in bytes = 8.
1163 L Bit
1164 Set to indicate Loose hop.
1165 Cleared to indicate a strict hop.
1167 Reserved
1168 Zero on transmission. Ignored on receipt.
1170 Local LSPID
1171 A 2 byte field indicating the LSPID which is unique with
1172 reference to its Ingress LSR.
1174 Ingress LSR Router ID
1175 An LSR may use any of its own IPv4 addresses in this field.
1177 4.8. Processing of the Explicit Route TLV
1179 4.8.1. Selection of the next hop
1181 A Label Request Message containing an explicit route TLV must
1182 determine the next hop for this path. Selection of this next hop
1183 may involve a selection from a set of possible alternatives. The
1184 mechanism for making a selection from this set is implementation
1185 dependent and is outside of the scope of this specification.
1186 Selection of particular paths is also outside of the scope of this
1187 specification, but it is assumed that each node will make a best
1189 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 23
1190 effort attempt to determine a loop-free path. Note that such best
1191 efforts may be overridden by local policy.
1193 To determine the next hop for the path, a node performs the
1194 following steps:
1196 1. The node receiving the Label Request Message must first
1197 evaluate the first ER-Hop. If the L bit is not set in the first
1198 ER-Hop and if the node is not part of the abstract node described
1199 by the first ER-Hop, it has received the message in error, and
1200 should return a "Bad Initial ER-Hop� error. If the L bit is set
1201 and the local node is not part of the abstract node described by
1202 the first ER-Hop, the node selects a next hop that is along the
1203 path to the abstract node described by the first ER-Hop. If there
1204 is no first ER-Hop, the message is also in error and the system
1205 should return a "Bad Explicit Routing TLV� error using a
1206 Notification Message sent upstream.
1208 2. If there is no second ER-Hop, this indicates the end of the
1209 explicit route. The explicit route TLV should be removed from the
1210 Label Request Message. This node may or may not be the end of
1211 the LSP. Processing continues with section 4.8.2, where a new
1212 explicit route TLV may be added to the Label Request Message.
1214 3. If the node is also a part of the abstract node described by
1215 the second ER-Hop, then the node deletes the first ER-Hop and
1216 continues processing with step 2, above. Note that this makes
1217 the second ER-Hop into the first ER-Hop of the next iteration.
1219 4. The node determines if it is topologically adjacent to the
1220 abstract node described by the second ER-Hop. If so, the node
1221 selects a particular next hop which is a member of the abstract
1222 node. The node then deletes the first ER-Hop and continues
1223 processing with section 4.8.2.
1225 5. Next, the node selects a next hop within the abstract node of
1226 the first ER-Hop that is along the path to the abstract node of
1227 the second ER-Hop. If no such path exists then there are two
1228 cases:
1230 5.a If the second ER-Hop is a strict ER-Hop, then there is
1231 an error and the node should return a "Bad Strict Node�
1232 error.
1234 5.b Otherwise, if the second ER-Hop is a loose ER-Hop, then
1235 the node selects any next hop that is along the path to the
1236 next abstract node. If no path exists within the MPLS
1237 domain, then there is an error, and the node should return a
1238 "Bad loose node� error.
1240 6. Finally, the node replaces the first ER-Hop with any ER-Hop
1241 that denotes an abstract node containing the next hop. This is
1243 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 24
1244 necessary so that when the explicit route is received by the next
1245 hop, it will be accepted.
1247 7. Progress the Label Request Message to the next hop.
1249 4.8.2. Adding ER-Hops to the explicit route TLV
1251 After selecting a next hop, the node may alter the explicit route in
1252 the following ways.
1254 If, as part of executing the algorithm in section 4.8.1, the
1255 explicit route TLV is removed, the node may add a new explicit route
1256 TLV.
1258 Otherwise, if the node is a member of the abstract node for the
1259 first ER-Hop, then a series of ER-Hops may be inserted before the
1260 first ER-Hop or may replace the first ER-Hop. Each ER-Hop in this
1261 series must denote an abstract node that is a subset of the current
1262 abstract node.
1264 Alternately, if the first ER-Hop is a loose ER-Hop, an arbitrary
1265 series of ER-Hops may be inserted prior to the first ER-Hop.
1267 4.9 Route Pinning TLV
1269 Section 2.4 describes the use of route pinning. The encoding of the
1270 Route Pinning TLV is as follows:
1272 0 1 2 3
1273 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
1274 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1275 |0|0| Type = 0x0823 | Length = 4 |
1276 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1277 |P| Reserved |
1278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1280 Type
1281 A fourteen-bit field carrying the value of the Pinning-TLV
1282 Type = 0x0823
1284 Length
1285 Specifies the length of the value field in bytes = 4.
1287 P Bit
1288 The P bit is set to 1 to indicate that route pinning is
1289 requested.
1290 The P bit is set to 0 to indicate that route pinning is not
1291 requested
1293 Reserved
1294 Zero on transmission. Ignored on receipt.
1296 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 25
1297 4.10 CR-LSP FEC Element
1299 A new FEC element is introduced in this specification to support CR-
1300 LSPs. A FEC TLV containing a FEC of Element type CR-LSP (0x04) is a
1301 CR-LSP FEC TLV. The CR-LSP FEC Element is an opaque FEC to be used
1302 only in Messages of CR-LSPs.
1304 A single FEC element MUST be included in the Label Request Message.
1305 The FEC Element SHOULD be the CR-LSP FEC Element. However, one of
1306 the other FEC elements (Type=0x01, 0x02, 0x03) defined in [1] MAY be
1307 in CR-LDP messages instead of the CR-LSP FEC Element for certain
1308 applications. A FEC TLV containing a FEC of Element type CR-LSP
1309 (0x04) is a CR-LSP FEC TLV.
1311 FEC Element Type Value
1312 Type name
1314 CR-LSP 0x04 No value; i.e., 0 value octets;
1316 The CR-LSP FEC TLV encoding is as follows:
1318 0 1 2 3
1319 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
1320 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1321 |0|0| Type = 0x0100 | Length = 1 |
1322 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1323 | CR-LSP (4) |
1324 +-+-+-+-+-+-+-+-+
1326 Type
1327 A fourteen-bit field carrying the value of the FEC TLV
1328 Type = 0x0100
1330 Length
1331 Specifies the length of the value field in bytes = 1.
1333 CR-LSP FEC Element Type
1335 0x04
1337 5. IANA Considerations
1339 CR-LDP defines the following name spaces, which require management:
1341 - TLV types.
1342 - FEC types.
1343 - Status codes.
1345 The following sections provide guidelines for managing these name
1346 spaces.
1348 5.1 TLV Type Name Space
1350 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 26
1351 RFC 3036 [1] defines the LDP TLV name space. This document further
1352 subdivides the range of RFC 3036 from that TLV space for TLVs
1353 associated with the CR-LDP in the range 0x0800 - 0x08FF.
1355 Following the policies outlined in [IANA], TLV types in this range
1356 are allocated through an IETF Consensus action.
1358 Initial values for this range are specified in the following table:
1360 TLV Type
1361 -------------------------------------- ----------
1362 Explicite Route TLV 0x0800
1363 Ipv4 Prefix ER-Hop TLV 0x0801
1364 Ipv6 Prefix ER-Hop TLV 0x0802
1365 Autonomous System Number ER-Hop TLV 0x0803
1366 LSP-ID ER-Hop TLV 0x0804
1367 Traffic Parameters TLV 0x0810
1368 Preemption TLV 0x0820
1369 LSPID TLV 0x0821
1370 Resource Class TLV 0x0822
1371 Route Pinning TLV 0x0823
1373 5.2 FEC Type Name Space
1375 RFC 3036 defines the FEC Type TLV name space. This document further
1376 subdivides the range of RFC 3036 from that TLV space for TLVs
1377 associated with the CR-LDP in the range 100 - 116.
1379 Following the policies outlined in [IANA], TLV types in this range
1380 are allocated through an IETF Consensus action.
1382 Initial values for this range are specified in the follwing table:
1384 FEC Element TLV Type
1385 -------------------------------------- ----------
1386 CR-LSP FEC Element TLV 0x0100
1388 5.3 Status Code Space
1390 RFC 3036 defines the Status Code name space. This document further
1391 subdivides the range of RFC 3036 from that TLV space for TLVs
1392 associated with the CR-LDP in the range 0x44000000 - 0x440000FF.
1394 Following the policies outlined in [IANA], TLV types in this range
1395 are allocated through an IETF Consensus action.
1397 Initial values for this range are specified in the follwing table:
1399 Status Code Type
1400 -------------------------------------- ----------
1401 Bad Explicit Routing TLV Error 0x44000001
1403 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 27
1404 Bad Strict Node Error 0x44000002
1405 Bad Loose Node Error 0x44000003
1406 Bad Initial ER-Hop Error 0x44000004
1407 Resource Unavailable 0x44000005
1408 Traffic Parameters Unavailable 0x44000006
1409 LSP Preempted 0x44000007
1410 Modify Request Not Supported 0x44000008
1411 Setup Abort (Label Request Aborted in [1]) 0x04000015
1413 6. Security
1415 CR-LDP inherits the same security mechanism described in Section 4.0
1416 of [1] to protect against the introduction of spoofed TCP segments
1417 into LDP session connection streams.
1419 7. Acknowledgments
1421 The messages used to signal the CR-LSP setup are based on the work
1422 done by the [1] team.
1424 The authors would also like to acknowledge the careful review and
1425 comments of Ken Hayward, Greg Wright, Geetha Brown, Brian Williams,
1426 Paul Beaubien, Matthew Yuen, Liam Casey, Ankur Anand, Adrian Farrel.
1428 8. Intellectual Property Consideration
1430 The IETF has been notified of intellectual property rights claimed
1431 in regard to some or all of the specification contained in this
1432 document. For more information consult the online list of claimed
1433 rights.
1435 9. References
1437 1 Andersson et. al., "Label Distribution Protocol Specification"
1438 RFC 3036, January 2001.
1440 2 Rosen et. al., "Multiprotocol Label Switching Architecture",
1441 RFC 3031, January 2001.
1443 3 Awduche et. al., "Requirements for Traffic Engineering Over
1444 MPLS", RFC 2702, September 1999.
1446 4 Gleeson, et. al., "A Framework for IP Based Virtual Private
1447 Networks", RFC 2764, February 2000.
1449 5 B. Jamoussi, et. al., �Applicability Statement for CR-LDP�, work
1450 in progress, (draft-ietf-mpls-crldp-applic-01), June 2000.
1452 6 S. Bradner, "Key words for use in RFCs to Indicate Requirement
1453 Levels�, RFC 2119, March 1997.
1455 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 28
1456 7 L. Wu, et. al., "LDP State Machine", work in progress,
1457 (draft-ietf-mpls-ldp-state-03), January 2000.
1459 8 J. Ash, et. al., "LSP Modification Using CR-LDP", work in
1460 progress, (draft-ietf-mpls-crlsp-modify-02), October 2000.
1462 10. Author�s Addresses
1464 Osama S. Aboul-Magd Loa Andersson
1465 Nortel Networks Nortel Networks
1466 P O Box 3511 Station C S:t Eriksgatan 115
1467 Ottawa, ON K1Y 4H7 PO Box 6701
1468 Canada 113 85 Stockholm
1469 Phone: +1 613 763-5827 Tel: +46 8 508 835 00
1470 Osama@nortelnetworks.com Fax: +46 8 508 835 01
1471 Loa_andersson@nortelnetworks.com
1473 Peter Ashwood-Smith Ross Callon
1474 Nortel Networks Juniper Networks
1475 P O Box 3511 Station C 1194 North Mathilda Avenue,
1476 Ottawa, ON K1Y 4H7 Sunnyvale, CA 94089
1477 Canada 978-692-6724
1478 Phone: +1 613 763-4534 rcallon@juniper.net
1479 Petera@nortelnetworks.com
1481 Ram Dantu Paul Doolan
1482 Cisco Systems Ennovate Networks
1483 17919 Waterview Parkway 330 Codman Hill Rd
1484 Dallas, 75252 Marlborough MA 01719
1485 +1 469 255 0716 Phone: 978-263-2002
1486 rdantu@cisco.com Pdoolan@ennovatenetworks.com
1488 Nancy Feldman Andre Fredette
1489 IBM Research PhotonEx Corporation
1490 30 Saw Mill River Road 135 South Road
1491 Hawthorne, NY 10532 Bedford, MA 01730
1492 Phone: 914-784-3254 email: fredette@photonex.com
1493 Nkf@us.ibm.com phone: 781-275-8500
1495 Eric Gray Joel M. Halpern
1496 600 Federal Drive Longitude Systems, Inc.
1497 Andover, MA 01810 1319 Shepard Road
1498 Phone: (978) 689-1610 Sterling, VA 20164
1499 eric.gray@sandburst.com 703-433-0808 x207
1500 joel@longsys.com
1502 Juha Heinanen Fiffi Hellstrand
1503 Telia Finland, Inc. Nortel Networks
1504 Myyrmaentie 2 S:t Eriksgatan 115
1505 01600 VANTAA PO Box 6701, 113 85 Stockholm
1506 Finland Sweden
1508 Jamoussi, et. al. draft-ietf-mpls-crldp-05.txt 29
1509 Tel: +358 41 500 4808 +46705593687
1510 Jh@telia.fi fiffi@nortelnetworks.com
1512 Bilel Jamoussi Timothy E. Kilty
1513 Nortel Networks Corp. Newbridge Networks, Inc.
1514 600 Technology Park Drive 5 Corporate Drive
1515 Billerica, MA 01821 Andover, MA 01810
1516 USA USA
1517 Phone: +1 978 288-4506 phone: 978 691-4656
1518 Jamoussi@nortelnetworks.com tkilty@northchurch.net
1520 Andrew G. Malis Muckai K Girish
1521 Vivace Networks Atoga Systems
1522 2730 Orchard Parkway 49026 Milmont Drive
1523 San Jose, CA 95134 Fremont, CA 94538
1524 Andy.Malis@vivacenetworks.com E-mail: muckai@atoga.com
1525 Tel: +1 408 383 7223
1526 Fax: +1 408 904 4748
1528 Kenneth Sundell Pasi Vaananen
1529 Nortel Networks Nokia Telecommunications
1530 S:t Eriksgatan 115 3 Burlington Woods Drive,
1531 PO Box 6701 Burlington, MA 01803
1532 113 85 Stockholm Phone: +1-781-238-4981
1533 Tel: +46 8 508 835 00 pasi.vaananen@nokia.com
1534 Fax: +46 8 508 835 01
1535 Ksundell@nortelnetworks.com
1537 Tom Worster Liwen Wu
1538 Ennovate Networks Cisco Systems
1539 60 Codman Hill Rd 250 Apollo Drive
1540 Boxborough Chelmsford, MA. 01824
1541 MA 01719 Tel: 978-244-3087.
1542 tworster@ennovatenetworks.com liwwu@cisco.com
1544 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 30
1545 Appendix A: CR-LSP Establishment Examples
1547 A.1 Strict Explicit Route Example
1549 This appendix provides an example for the setup of a strictly routed
1550 CR-LSP. In this example, a specific node represents each abstract
1551 node.
1553 The sample network used here is a four node network with two edge
1554 LSRs and two core LSRs as follows:
1556 abc
1557 LSR1------LSR2------LSR3------LSR4
1559 LSR1 generates a Label Request Message as described in Section 3.1
1560 of this draft and sends it to LSR2. This message includes the CR-
1561 TLV.
1563 A vector of three ER-Hop TLVs composes the ER-TLV.
1564 The ER-Hop TLVs used in this example are of type 0x0801 (IPv4
1565 prefix) with a prefix length of 32. Hence, each ER-Hop TLV
1566 identifies a specific node as opposed to a group of nodes.
1567 At LSR2, the following processing of the ER-TLV per Section 4.8.1 of
1568 this draft takes place:
1570 1. The node LSR2 is part of the abstract node described by the
1571 first hop . Therefore, the first step passes the test. Go
1572 to step 2.
1574 2. There is a second ER-Hop, . Go to step 3.
1576 3. LSR2 is not part of the abstract node described by the
1577 second ER-Hop . Go to Step 4.
1579 4. LSR2 determines that it is topologically adjacent to the
1580 abstract node described by the second ER-Hop . LSR2 selects
1581 a next hop (LSR3) which is the abstract node. LSR2 deletes the
1582 first ER-Hop from the ER-TLV, which now becomes .
1583 Processing continues with Section 4.8.2.
1585 At LSR2, the following processing of Section 4.8.2 takes place:
1586 Executing algorithm 4.8.1 did not result in the removal of the ER-
1587 TLV.
1589 Also, LSR2 is not a member of the abstract node described by the
1590 first ER-Hop .
1592 Finally, the first ER-Hop is a strict hop.
1594 Therefore, processing section 4.8.2 does not result in the insertion
1595 of new ER-Hops. The selection of the next hop has been already done
1596 is step 4 of Section 4.8.1 and the processing of the ER-TLV is
1598 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 31
1599 completed at LSR2. In this case, the Label Request Message including
1600 the ER-TLV is progressed by LSR2 to LSR3.
1602 At LSR3, a similar processing to the ER-TLV takes place except that
1603 the incoming ER-TLV = and the outgoing ER-TLV is .
1605 At LSR4, the following processing of section 4.8.1 takes place:
1607 1. The node LSR4 is part of the abstract node described by the
1608 first hop . Therefore, the first step passes the test. Go to
1609 step 2.
1611 2. There is no second ER-Hop, this indicates the end of the CR-
1612 LSP. The ER-TLV is removed from the Label Request Message.
1613 Processing continues with Section 4.8.2.
1615 At LSR4, the following processing of Section 4.8.2 takes place:
1616 Executing algorithm 4.8.1 resulted in the removal of the ER-TLV.
1617 LSR4 does not add a new ER-TLV.
1619 Therefore, processing section 4.8.2 does not result in the insertion
1620 of new ER-Hops. This indicates the end of the CR-LSP and the
1621 processing of the ER-TLV is completed at LSR4.
1623 At LSR4, processing of Section 3.2 is invoked. The first condition
1624 is satisfied (LSR4 is the egress end of the CR-LSP and upstream
1625 mapping has been requested). Therefore, a Label Mapping Message is
1626 generated by LSR4 and sent to LSR3.
1628 At LSR3, the processing of Section 3.2 is invoked. The second
1629 condition is satisfied (LSR3 received a mapping from its downstream
1630 next hop LSR4 for a CR-LSP for which an upstream request is still
1631 pending). Therefore, a Label Mapping Message is generated by LSR3
1632 and sent to LSR2.
1634 At LSR2, a similar processing to LSR 3 takes place and a Label
1635 Mapping Message is sent back to LSR1, which completes the end-to-end
1636 CR-LSP setup.
1638 A.2 Node Groups and Specific Nodes Example
1640 A request at ingress LSR to setup a CR-LSP might originate from a
1641 management system or an application, the details are implementation
1642 specific.
1644 The ingress LSR uses information provided by the management system
1645 or the application and possibly also information from the routing
1646 database to calculate the explicit route and to create the Label
1647 Request Message.
1649 The Label request message carries together with other necessary
1650 information an ER-TLV defining the explicitly routed path. In our
1652 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 32
1653 example the list of hops in the ER-Hop TLV is supposed to contain an
1654 abstract node representing a group of nodes, an abstract node
1655 representing a specific node, another abstract node representing a
1656 group of nodes, and an abstract node representing a specific egress
1657 point.
1659 In--{Group 1}--{Specific A}--{Group 2}--{Specific Out: B}
1660 The ER-TLV contains four ER-Hop TLVs:
1662 1. An ER-Hop TLV that specifies a group of LSR valid for the
1663 first abstract node representing a group of nodes (Group 1).
1665 2. An ER-Hop TLV that indicates the specific node (Node A).
1667 3. An ER-Hop TLV that specifies a group of LSRs valid for the
1668 second abstract node representing a group of nodes (Group 2).
1670 4. An ER-Hop TLV that indicates the specific egress point for
1671 the CR-LSP (Node B).
1673 All the ER-Hop TLVs are strictly routed nodes.
1674 The setup procedure for this CR-LSP works as follows:
1676 1. The ingress node sends the Label Request Message to a node
1677 that is a member the group of nodes indicated in the first ER-
1678 Hop TLV, following normal routing for the specific node (A).
1680 2. The node that receives the message identifies itself as part
1681 of the group indicated in the first ER-Hop TLV, and that it is
1682 not the specific node (A) in the second. Further it realizes
1683 that the specific node (A) is not one of its next hops.
1685 3. It keeps the ER-Hop TLVs intact and sends a Label Request
1686 Message to another node that is part of the group indicated in
1687 the first ER-Hop TLV (Group 1), following normal routing for
1688 the specific node (A).
1690 4. The node that receives the message identifies itself as part
1691 of the group indicated in the first ER-Hop TLV, and that it is
1692 not the specific node (A) in the second ER-Hop TLV. Further it
1693 realizes that the specific node (A) is one of its next hops.
1695 5. It removes the first ER-Hop TLVs and sends a Label Request
1696 Message to the specific node (A).
1698 6. The specific node (A) recognizes itself in the first ER-Hop
1699 TLV. Removes the specific ER-Hop TLV.
1701 7. It sends a Label Request Message to a node that is a member
1702 of the group (Group 2) indicated in the ER-Hop TLV.
1704 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 33
1705 8. The node that receives the message identifies itself as part
1706 of the group indicated in the first ER-Hop TLV, further it
1707 realizes that the specific egress node (B) is one of its next
1708 hops.
1710 9. It sends a Label Request Message to the specific egress node
1711 (B).
1713 10. The specific egress node (B) recognizes itself as the
1714 egress for the CR-LSP, it returns a Label Mapping Message, that
1715 will traverse the same path as the Label Request Message in the
1716 opposite direction.
1718 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 34
1719 Appendix B. QoS Service Examples
1721 B.1 Service Examples
1723 Construction of an end-to-end service is the result of the rules
1724 enforced at the edge and the treatment that packets receive at the
1725 network nodes. The rules define the traffic conditioning actions
1726 that are implemented at the edge and they include policing with
1727 pass, mark, and drop capabilities. The edge rules are expected tobe
1728 defined by the mutual agreements between the service providers and
1729 their customers and they will constitute an essential part of the
1730 SLA. Therefore edge rules are not included in the signaling
1731 protocol.
1733 Packet treatment at a network node is usually referred to as the
1734 local behavior. Local behavior could be specified in many ways. One
1735 example for local behavior specification is the service frequency
1736 introduced in section 4.3.2.1, together with the resource
1737 reservation rules implemented at the nodes.
1739 Edge rules and local behaviors can be viewed as the main building
1740 blocks for the end-to-end service construction. The following table
1741 illustrates the applicability of the building block approach for
1742 constructing different services including those defined for ATM.
1744 Service PDR PBS CDR CBS EBS Service Conditioning
1745 Examples Frequency Action
1747 DS S S =PDR =PBS 0 Frequent drop>PDR
1749 TS S S S S 0 Unspecified drop>PDR,PBS
1750 mark>CDR,CBS
1752 BE inf inf inf inf 0 Unspecified -
1754 FRS S S CIR ~B_C ~B_E Unspecified drop>PDR,PBS
1755 mark>CDR,CBS,EBS
1757 ATM-CBR PCR CDVT =PCR =CDVT 0 VeryFrequent drop>PCR
1759 ATM-VBR.3(rt) PCR CDVT SCR MBS 0 Frequent drop>PCR
1760 mark>SCR,MBS
1762 ATM-VBR.3(nrt) PCR CDVT SCR MBS 0 Unspecified drop>PCR
1763 mark>SCR,MBS
1765 ATM-UBR PCR CDVT - - 0 Unspecified drop>PCR
1767 ATM-GFR.1 PCR CDVT MCR MBS 0 Unspecified drop>PCR
1769 ATM-GFR.2 PCR CDVT MCR MBS 0 Unspecified drop>PCR
1770 mark>MCR,MFS
1772 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 35
1773 int-serv-CL p m r b 0 Frequent drop>p
1774 drop>r,b
1776 S= User specified
1778 In the above table, the DS refers to a delay sensitive service where
1779 the network commits to deliver with high probability user datagrams
1780 at a rate of PDR with minimum delay and delay requirements.
1781 Datagrams in excess of PDR will be discarded.
1783 The TS refers to a generic throughput sensitive service where the
1784 network commits to deliver with high probability user datagrams at a
1785 rate of at least CDR. The user may transmit at a rate higher than
1786 CDR but datagrams in excess of CDR would have a lower probability of
1787 being delivered.
1789 The BE is the best effort service and it implies that there are no
1790 expected service guarantees from the network.
1792 B.2 Establishing CR-LSP Supporting Real-Time Applications
1794 In this scenario the customer needs to establish an LSP for
1795 supporting real-time applications such as voice and video. The
1796 Delay-sensitive (DS) service is requested in this case.
1798 The first step is the specification of the traffic parameters in the
1799 signaling message. The two parameters of interest to the DS service
1800 are the PDR and the PBS and the user based on his requirements
1801 specifies their values. Since all the traffic parameters are
1802 included in the signaling message, appropriate values must be
1803 assigned to all of them. For DS service, the CDR and the CBS values
1804 are set equal to the PDR and the PBS respectively. An indication of
1805 whether the parameter values are subject to negotiation is flagged.
1807 The transport characteristics of the DS service require Frequent
1808 frequency to be requested to reflect the real-time delay
1809 requirements of the service.
1811 In addition to the transport characteristics, both the network
1812 provider and the customer need to agree on the actions enforced at
1813 the edge. The specification of those actions is expected to be a
1814 part of the service level agreement (SLA) negotiation and is not
1815 included in the signaling protocol. For DS service, the edge action
1816 is to drop packets that exceed the PDR and the PBS specifications.
1817 The signaling message will be sent in the direction of the ER path
1818 and the LSP is established following the normal LDP procedures. Each
1819 LSR applies its admission control rules. If sufficient resources are
1820 not available and the parameter values are subject to negotiation,
1821 then the LSR could negotiate down the PDR, the PBS, or both.
1823 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 36
1824 The new parameter values are echoed back in the Label Mapping
1825 Message. LSRs might need to re-adjust their resource reservations
1826 based on the new traffic parameter values.
1828 B.3 Establishing CR-LSP Supporting Delay Insensitive Applications
1830 In this example we assume that a throughput sensitive (TS) service
1831 is requested. For resource allocation the user assigns values for
1832 PDR, PBS, CDR, and CBS. The negotiation flag is set if the traffic
1833 parameters are subject to negotiation.
1834 Since the service is delay insensitive by definition, the
1835 Unspecified frequency is signaled to indicate that the service
1836 frequency is not an issue.
1838 Similar to the previous example, the edge actions are not subject
1839 for signaling and are specified in the service level agreement
1840 between the user and the network provider.
1842 For TS service, the edge rules might include marking to indicate
1843 high discard precedence values for all packets that exceed CDR and
1844 the CBS. The edge rules will also include dropping of packets that
1845 conform to neither PDR nor PBS.
1847 Each LSR of the LSP is expected to run its admission control rules
1848 and negotiate traffic parameters down if sufficient resources do not
1849 exist. The new parameter values are echoed back in the Label Mapping
1850 Message. LSRs might need to re-adjust their resources based on the
1851 new traffic parameter values.
1853 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 37
1854 Full Copyright Statement
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1868 English.
1870 The limited permissions granted above are perpetual and will not be
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1873 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-04.txt 38