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2 MPLS Working Group Bilel Jamoussi, Editor
3 Internet Draft Nortel Networks Corp.
4 Expiration Date: January 2001
6 O. Aboul-Magd, L. Andersson, P. Ashwood-Smith,
7 F. Hellstrand, K. Sundell, Nortel Networks Corp.
8 R. Callon, Juniper Networks.
9 R. Dantu, IPmobile
10 P. Doolan, T. Worster, Ennovate Networks Corp.
11 N. Feldman, IBM Corp.
12 A. Fredette, PhotonEx Corp.
13 M. Girish, Atoga Systems
14 E. Gray, Zaffire, Inc.
15 J. Halpern, Longitude Systems, Inc.
16 J. Heinanen, Telia Finland
17 T. Kilty, Newbridge Networks, Inc.
18 A. Malis, Vivace Networks
19 P. Vaananen, Nokia Telecommunications
20 L. Wu, Cisco Systems
22 July 2000
24 Constraint-Based LSP Setup using LDP
26 draft-ietf-mpls-cr-ldp-04.txt
28 Status of this Memo
30 This document is an Internet-Draft and is in full conformance with
31 all provisions of Section 10 of RFC2026.
33 Internet-Drafts are working documents of the Internet Engineering
34 Task Force (IETF), its areas, and its working groups. Note that
35 other groups may also distribute working documents as Internet-
36 Drafts.
38 Internet-Drafts are draft documents valid for a maximum of six
39 months and may be updated, replaced, or obsoleted by other documents
40 at any time. It is inappropriate to use Internet-Drafts as reference
41 material or to cite them other than as _work in progress._
43 The list of current Internet-Drafts can be accessed at
44 http://www.ietf.org/ietf/1id-abstracts.txt
46 The list of Internet-Draft Shadow Directories can be accessed at
47 http://www.ietf.org/shadow.html.
49 Abstract
51 Label Distribution Protocol (LDP) is defined in [1] for distribution
52 of labels inside one MPLS domain. One of the most important
53 services that may be offered using MPLS in general and LDP in
54 particular is support for constraint-based routing of traffic across
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], [3] and [4]. 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 [5]. More information
64 about the applicability of CR-LDP can be found in [6].
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 [7].
73 Table of Contents
75 1. Introduction....................................................4
76 2. Constraint-based Routing Overview...............................4
77 2.1 Strict and Loose Explicit Routes...............................5
78 2.2 Traffic Characteristics........................................5
79 2.3 Pre-emption....................................................6
80 2.4 Route Pinning..................................................6
81 2.5 Resource Class.................................................6
82 3. Solution Overview...............................................7
83 3.1 Required Messages and TLVs.....................................8
84 3.2 Label Request Message..........................................8
85 3.3 Label Mapping Message..........................................9
86 3.4 Notification Message..........................................10
87 3.5 Release , Withdraw, and Abort Messages........................10
88 4. Protocol Specification.........................................10
89 4.1 Explicit Route TLV (ER-TLV)...................................11
90 4.2 Explicit Route Hop TLV (ER-Hop TLV)...........................11
91 4.3 Traffic Parameters TLV........................................12
92 4.3.1 Semantics...................................................14
93 4.3.1.1 Frequency.................................................14
94 4.3.1.2 Peak Rate.................................................14
95 4.3.1.3 Committed Rate............................................15
96 4.3.1.4 Excess Burst Size.........................................15
97 4.3.1.5 Peak Rate Token Bucket....................................15
98 4.3.1.6 Committed Data Rate Token Bucket..........................15
99 4.3.1.7 Weight....................................................16
100 4.3.2 Procedures..................................................16
101 4.3.2.1 Label Request Message.....................................16
102 4.3.2.2 Label Mapping Message.....................................17
103 4.3.2.3 Notification Message......................................17
104 4.4 Preemption TLV................................................17
105 4.5 LSPID TLV.....................................................18
106 4.6 Resource Class (Color) TLV....................................20
107 4.7 ER-Hop semantics..............................................20
108 4.7.1. ER-Hop 1: The IPv4 prefix..................................20
109 4.7.2. ER-Hop 2: The IPv6 address.................................21
110 4.7.3. ER-Hop 3: The autonomous system number....................22
111 4.7.4. ER-Hop 4: LSPID............................................22
112 4.8. Processing of the Explicit Route TLV.........................23
113 4.8.1. Selection of the next hop..................................23
114 4.8.2. Adding ER-Hops to the explicit route TLV...................25
115 4.9 Route Pinning TLV.............................................25
116 4.10 CR-LSP FEC Element...........................................26
117 4.11 TLV Type Summary.............................................26
118 4.12 FEC Type Summary.............................................27
119 4.13 Status Code Summary..........................................27
120 5. IANA Considerations............................................27
121 5.1 TLV Type Name Space...........................................27
122 5.2 FEC Type Name Space...........................................27
123 5.3 Status Code Space.............................................27
124 6. Security.......................................................28
125 7. Acknowledgments................................................28
126 8. Intellectual Property Consideration............................28
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 [3], [2], and [4]. Explicit routing is a subset of the
141 more general constraint-based routing function. At the MPLS WG
142 meeting held during the Washington IETF (December 1997) there was
143 consensus that LDP should support explicit routing of LSPs with
144 provision for indication of associated (forwarding) priority. In
145 the Chicago meeting (August 1998), a decision was made that support
146 for explicit path setup in LDP will be moved to a separate document.
147 This document provides that support and it has been accepted as a
148 working 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 [4]. 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
178 to provide a network operator with control over the path taken by an
179 LSP. This section is an overview of the various constraints
180 supported by this specification.
182 Like any other LSP a CR-LSP is a path through an MPLS network. The
183 difference is that while other paths are setup solely based on
184 information in routing tables or from a management system, the
185 constraint-based route is calculated at one point at the edge of
186 network based on criteria, including but not limited to routing
187 information. The intention is that this functionality shall give
188 desired special characteristics to the LSP in order to better
189 support the traffic sent over the LSP. The reason for setting up CR-
190 LSPs might be that one wants to assign certain bandwidth or other
191 Service Class characteristics to the LSP, or that one wants to make
192 sure that alternative routes use physically separate paths through
193 the network.
195 2.1 Strict and Loose Explicit Routes
197 An explicit route is represented in a Label Request Message as a
198 list of nodes or groups of nodes along the constraint-based route.
199 When the CR-LSP is established, all or a subset of the nodes in a
200 group may be traversed by the LSP. Certain operations to be
201 performed along the path can also be encoded in the constraint-based
202 route.
204 The capability to specify, in addition to specified nodes, groups of
205 nodes, of which a subset will be traversed by the CR-LSP, allows the
206 system a significant amount of local flexibility in fulfilling a
207 request for a constraint-based route. This allows the generator of
208 the constraint-based route to have some degree of imperfect
209 information about the details of the path.
211 The constraint-based route is encoded as a series of ER-Hops
212 contained in a constraint-based route TLV. Each ER-Hop may identify
213 a group of nodes in the constraint-based route. A constraint-based
214 route is then a path including all of the identified groups of nodes
215 in the order in which they appear in the TLV.
217 To simplify the discussion, we call each group of nodes an abstract
218 node. Thus, we can also say that a constraint-based route is a path
219 including all of the abstract nodes, with the specified operations
220 occurring along that path.
222 2.2 Traffic Characteristics
224 The traffic characteristics of a path are described in the Traffic
225 Parameters TLV in terms of a peak rate, committed rate, and service
226 granularity. The peak and committed rates describe the bandwidth
227 constraints of a path while the service granularity can be used to
228 specify a constraint on the delay variation that the CR-LDP MPLS
229 domain may introduce to a path's traffic.
231 2.3 Pre-emption
233 CR-LDP signals the resources required by a path on each hop of the
234 route. If a route with sufficient resources can not be found,
235 existing paths may be rerouted to reallocate resources to the new
236 path. This is the process of path pre-emption. Setup and holding
237 priorities are used to rank existing paths (holding priority) and
238 the new path (setup priority) to determine if the new path can pre-
239 empt an existing path.
241 The setupPriority of a new CR-LSP and the holdingPriority attributes
242 of the existing CR-LSP are used to specify priorities. Signaling a
243 higher holding priority express that the path, once it has been
244 established, should have a lower chance of being pre-empted.
245 Signaling a higher setup priority expresses the expectation that, in
246 the case that resource are unavailable, the path is more likely to
247 pre-empt other paths. The exact rules determining bumping are an
248 aspect of network policy.
250 The allocation of setup and holding priority values to paths is an
251 aspect of network policy.
253 The setup and holding priority values range from zero (0) to seven
254 (7). The value zero (0) is the priority assigned to the most
255 important path. It is referred to as the highest priority. Seven (7)
256 is the priority for the least important path. The use of default
257 priority values is an aspect of network policy. The recommended
258 default value is (4).
260 The setupPriority of a CR-LSP should not be higher (numerically
261 less) than its holdingPriority since it might bump an LSP and be
262 bumped by the next _equivalent_ request.
264 2.4 Route Pinning
266 Route pinning is applicable to segments of an LSP that are loosely
267 routed - i.e. those segments which are specified with a next hop
268 with the _L_ bit set or where the next hop is an _abstract node_. A
269 CR-LSP may be setup using route pinning if it is undesirable to
270 change the path used by an LSP even when a better next hop becomes
271 available at some LSR along the loosely routed portion of the LSP.
273 2.5 Resource Class
275 The network operator may classify network resources in various ways.
276 These classes are also known as _colors_ or _administrative groups_.
277 When a CR-LSP is being established, it's necessary to indicate which
278 resource classes the CR-LSP can draw from.
280 3. Solution Overview
282 CR-LSP over LDP Specification is designed with the following goals:
284 1. Meet the requirements outlined in [4] for performing traffic
285 engineering and provide a solid foundation for performing
286 more general constraint-based routing.
288 2. Build on already specified functionality that meets the
289 requirements whenever possible. Hence, this specification is
290 based on [1].
292 3. Keep the solution simple.
294 In this document, support for unidirectional point-to-point CR-LSPs
295 is specified. Support for point-to-multipoint, multipoint-to-point,
296 is for further study (FFS).
298 Support for constraint-based routed LSPs in this specification
299 depends on the following minimal LDP behaviors as specified in [1]:
301 - Use of Basic and/or Extended Discovery Mechanisms.
302 - Use of the Label Request Message defined in [1] in downstream
303 on demand label advertisement mode with ordered control.
304 - Use of the Label Mapping Message defined in [1] in downstream
305 on demand mode with ordered control.
306 - Use of the Notification Message defined in [1].
307 - Use of the Withdraw and Release Messages defined in [1].
308 - Use of the Loop Detection (in the case of loosely routed
309 segments of a CR-LSP) mechanisms defined in [1].
311 In addition, the following functionality is added to what's defined
312 in [1]:
314 - The Label Request Message used to setup a CR-LSP includes one
315 or more CR-TLVs defined in Section 4. For instance, the Label
316 Request Message may include the ER-TLV.
317 - An LSR implicitly infers ordered control from the existence of
318 one or more CR-TLVs in the Label Request Message. This means
319 that the LSR can still be configured for independent control
320 for LSPs established as a result of dynamic routing. However,
321 when a Label Request Message includes one or more of the CR-
322 TLVs, then ordered control is used to setup the CR-LSP. Note
323 that this is also true for the loosely routed parts of a CR-
324 LSP.
325 - New status codes are defined to handle error notification for
326 failure of established paths specified in the CR-TLVs.
328 Optional TLVs MUST be implemented to be compliant with the protocol.
329 However, they are optionally carried in the CR-LDP messages to
330 signal certain characteristics of the CR-LSP being established or
331 modified.
333 Examples of CR-LSP establishment are given in Appendix A to
334 illustrate how the mechanisms described in this draft work.
336 3.1 Required Messages and TLVs
338 Any Messages, TLVs, and procedures not defined explicitly in this
339 document are defined in the LDP Specification [1]. The reader can
340 use [8] as an informational document about the state transitions,
341 which relate to CR-LDP messages.
343 The following subsections are meant as a cross-reference to the [1]
344 document and indication of additional functionality beyond what's
345 defined in [1] where necessary.
347 Note that use of the Status TLV is not limited to Notification
348 messages as specified in Section 3.4.6 of [1]. A message other than
349 a Notification message may carry a Status TLV as an Optional
350 Parameter. When a message other than a Notification carries a
351 Status TLV the U-bit of the Status TLV should be set to 1 to
352 indicate that the receiver should silently discard the TLV if
353 unprepared to handle it.
355 3.2 Label Request Message
357 The Label Request Message is as defined in 3.5.8 of [1] with the
358 following modifications (required only if any of the CR-TLVs is
359 included in the Label Request Message):
361 - The Label Request Message MUST include a single FEC-TLV
362 element. The CR-LSP FEC TLV element SHOULD be used. However,
363 the other FEC-TLVs defined in [1] MAY be used instead for
364 certain applications.
366 - The Optional Parameters TLV includes the definition of any of
367 the Constraint-based TLVs specified in Section 4.
369 - The Procedures to handle the Label Request Message are
370 augmented by the procedures for processing of the CR-TLVs as
371 defined in Section 4.
373 The encoding for the CR-LDP Label Request Message is as follows:
375 0 1 2 3
376 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
377 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
378 |0| Label Request (0x0401) | Message Length |
379 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
380 | Message ID |
381 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
382 | FEC TLV |
383 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
384 | LSPID TLV (CR-LDP, mandatory) |
385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
386 | ER-TLV (CR-LDP, optional) |
387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
388 | Traffic TLV (CR-LDP, optional) |
389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
390 | Pinning TLV (CR-LDP, optional) |
391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
392 | Resource Class TLV (CR-LDP, optional) |
393 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
394 | Pre-emption TLV (CR-LDP, optional) |
395 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
397 3.3 Label Mapping Message
399 The Label Mapping Message is as defined in 3.5.7 of [1] with the
400 following modifications:
402 - The Label Mapping Message MUST include a single Label-TLV.
404 - The Label Mapping Message Procedures are limited to downstream
405 on demand ordered control mode.
407 A Mapping message is transmitted by a downstream LSR to an upstream
408 LSR under one of the following conditions:
410 1. The LSR is the egress end of the CR-LSP and an upstream
411 mapping has been requested.
413 2. The LSR received a mapping from its downstream next hop LSR
414 for an CR-LSP for which an upstream request is still
415 pending.
417 The encoding for the CR-LDP Label Mapping Message is as follows:
419 0 1 2 3
420 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
421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
422 |0| Label Mapping (0x0400) | Message Length |
423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
424 | Message ID |
425 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
426 | FEC TLV |
427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
428 | Label TLV |
429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
430 | Label Request Message ID TLV |
431 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
432 | LSPID TLV (CR-LDP, optional) |
433 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
434 | Traffic TLV (CR-LDP, optional) |
435 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
437 3.4 Notification Message
439 The Notification Message is as defined in Section 3.5.1 of [1] and
440 the Status TLV encoding is as defined in Section 3.4.6 of [1].
441 Establishment of an CR-LSP may fail for a variety of reasons. All
442 such failures are considered advisory conditions and they are
443 signaled by the Notification Message.
445 Notification Messages carry Status TLVs to specify events being
446 signaled. New status codes are defined in Section 4.11 to signal
447 error notifications associated with the establishment of a CR-LSP
448 and the processing of the CR-TLV.
450 The Notification Message MAY carry the LSPID TLV of the
451 corresponding CR-LSP.
453 Notification Messages MUST be forwarded toward the LSR originating
454 the Label Request at each hop and at any time that procedures in
455 this specification - or in [1] - specify sending of a Notification
456 Message in response to a Label Request Message.
458 The encoding of the notification message is as follows:
460 0 1 2 3
461 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
462 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
463 |0| Notification (0x0001) | Message Length |
464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
465 | Message ID |
466 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
467 | Status (TLV) |
468 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
469 | Optional Parameters |
470 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
472 3.5 Release , Withdraw, and Abort Messages
474 The Label Release , Label Withdraw, and Label Abort Request Messages
475 are used as specified in [1]. These messages may also carry the
476 LSPID TLV.
478 4. Protocol Specification
480 The Label Request Message defined in [1] MUST carry the LSPID TLV
481 and MAY carry one or more of the optional Constraint-based Routing
482 TLVs (CR-TLVs) defined in this section. If needed, other constraints
483 can be supported later through the definition of new TLVs. In this
484 specification, the following TLVs are defined:
486 - Explicit Route TLV
487 - Explicit Route Hop TLV
488 - Traffic Parameters TLV
489 - Preemption TLV
490 - LSPID TLV
491 - Route Pinning TLV
492 - Resource Class TLV
493 - CR-LSP FEC TLV
495 4.1 Explicit Route TLV (ER-TLV)
497 The ER-TLV is an object that specifies the path to be taken by the
498 LSP being established. It is composed of one or more Explicit Route
499 Hop TLVs (ER-Hop TLVs) defined in Section 4.2.
501 0 1 2 3
502 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
503 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
504 |0|0| Type = 0x0800 | Length |
505 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
506 | ER-Hop TLV 1 |
507 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
508 | ER-Hop TLV 2 |
509 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
510 ~ ............ ~
511 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
512 | ER-Hop TLV n |
513 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
515 Type
516 A fourteen-bit field carrying the value of the ER-TLV Type =
517 0x0800.
519 Length
520 Specifies the length of the value field in bytes.
522 ER-Hop TLVs
523 One or more ER-Hop TLVs defined in Section 4.2.
525 4.2 Explicit Route Hop TLV (ER-Hop TLV)
527 The contents of an ER-TLV are a series of variable length ER-Hop
528 TLVs.
530 A node receiving a label request message including an ER-Hop type
531 that is not supported MUST not progress the label request message to
532 the downstream LSR and MUST send back a _No Route_ Notification
533 Message.
535 Each ER-Hop TLV has the form:
537 0 1 2 3
538 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
539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
540 |0|0| Type | Length |
541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
542 |L| Content // |
543 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
545 ER-Hop Type
546 A fourteen-bit field carrying the type of the ER-Hop contents.
547 Currently defined values are:
549 Value Type
550 ------ ------------------------
551 0x0801 IPv4 prefix
552 0x0802 IPv6 prefix
553 0x0803 Autonomous system number
554 0x0804 LSPID
556 Length
557 Specifies the length of the value field in bytes.
559 L bit
560 The L bit in the ER-Hop is a one-bit attribute. If the L bit
561 is set, then the value of the attribute is _loose._ Otherwise,
562 the value of the attribute is _strict._ For brevity, we say
563 that if the value of the ER-Hop attribute is loose then it is a
564 _loose ER-Hop._ Otherwise, it's a _strict ER-Hop._ Further,
565 we say that the abstract node of a strict or loose ER-Hop is a
566 strict or a loose node, respectively. Loose and strict nodes
567 are always interpreted relative to their prior abstract nodes.
568 The path between a strict node and its prior node MUST include
569 only network nodes from the strict node and its prior abstract
570 node.
572 The path between a loose node and its prior node MAY include
573 other network nodes, which are not part of the strict node or
574 its prior abstract node.
576 Contents
577 A variable length field containing a node or abstract node
578 which is one of the consecutive nodes that make up the
579 explicitly routed LSP.
581 4.3 Traffic Parameters TLV
583 The following sections describe the CR-LSP Traffic Parameters. The
584 required characteristics of a CR-LSP are expressed by the Traffic
585 Parameter values.
587 A Traffic Parameters TLV, is used to signal the Traffic Parameter
588 values. The Traffic Parameters are defined in the subsequent
589 sections.
591 The Traffic Parameters TLV contains a Flags field, a Frequency, a
592 Weight, and the five Traffic Parameters PDR, PBS, CDR, CBS, EBS.
593 The Traffic Parameters TLV is shown below:
595 0 1 2 3
596 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
597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
598 |0|0| Type = 0x0810 | Length = 24 |
599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
600 | Flags | Frequency | Reserved | Weight |
601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
602 | Peak Data Rate (PDR) |
603 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
604 | Peak Burst Size (PBS) |
605 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
606 | Committed Data Rate (CDR) |
607 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
608 | Committed Burst Size (CBS) |
609 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
610 | Excess Burst Size (EBS) |
611 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
613 Type
614 A fourteen-bit field carrying the value of the Traffic
615 Parameters TLV Type = 0x0810.
617 Length
618 Specifies the length of the value field in bytes = 24.
620 Flags
621 The Flags field is shown below:
623 +--+--+--+--+--+--+--+--+
624 | Res |F6|F5|F4|F3|F2|F1|
625 +--+--+--+--+--+--+--+--+
627 Res - These bits are reserved.
628 Zero on transmission.
629 Ignored on receipt.
630 F1 - Corresponds to the PDR.
631 F2 - Corresponds to the PBS.
632 F3 - Corresponds to the CDR.
633 F4 - Corresponds to the CBS.
634 F5 - Corresponds to the EBS.
635 F6 - Corresponds to the Weight.
637 Each flag Fi is a Negotiable Flag corresponding to a Traffic
638 Parameter. The Negotiable Flag value zero denotes NotNegotiable
639 and value one denotes Negotiable.
641 Frequency
642 The Frequency field is coded as an 8 bit unsigned integer with
643 the following code points defined:
645 0- Unspecified
646 1- Frequent
647 2- VeryFrequent
648 3-255 - Reserved
649 Reserved - Zero on transmission. Ignored on receipt.
651 Weight
652 An 8 bit unsigned integer indicating the weight of the CR-LSP.
653 Valid weight values are from 1 to 255. The value 0 means that
654 weight is not applicable for the CR-LSP.
656 Traffic Parameters
657 Each Traffic Parameter is encoded as a 32-bit IEEE single-
658 precision floating-point number. A value of positive infinity
659 is represented as an IEEE single-precision floating-point
660 number with an exponent of all ones (255) and a sign and
661 mantissa of all zeros. The values PDR and CDR are in units of
662 bytes per second. The values PBS, CBS and EBS are in units of
663 bytes.
665 The value of PDR MUST be greater than or equal to the value of
666 CDR in a correctly encoded Traffic Parameters TLV.
668 4.3.1 Semantics
670 4.3.1.1 Frequency
672 The Frequency specifies at what granularity the CDR allocated to the
673 CR-LSP is made available. The value VeryFrequent means that the
674 available rate should average at least the CDR when measured over
675 any time interval equal to or longer than the shortest packet time
676 at the CDR. The value Frequent means that the available rate should
677 average at least the CDR when measured over any time interval equal
678 to or longer than a small number of shortest packet times at the
679 CDR.
681 The value Unspecified means that the CDR MAY be provided at any
682 granularity.
684 4.3.1.2 Peak Rate
686 The Peak Rate defines the maximum rate at which traffic SHOULD be
687 sent to the CR-LSP. The Peak Rate is useful for the purpose of
688 resource allocation. If resource allocation within the MPLS domain
689 depends on the Peak Rate value then it should be enforced at the
690 ingress to the MPLS domain.
692 The Peak Rate is defined in terms of the two Traffic Parameters PDR
693 and PBS, see section 4.3.1.5 below.
695 4.3.1.3 Committed Rate
697 The Committed Rate defines the rate that the MPLS domain commits to
698 be available to the CR-LSP.
700 The Committed Rate is defined in terms of the two Traffic Parameters
701 CDR and CBS, see section 4.3.1.6 below.
703 4.3.1.4 Excess Burst Size
705 The Excess Burst Size may be used at the edge of an MPLS domain for
706 the purpose of traffic conditioning. The EBS MAY be used to measure
707 the extent by which the traffic sent on a CR-LSP exceeds the
708 committed rate.
710 The possible traffic conditioning actions, such as passing, marking
711 or dropping, are specific to the MPLS domain.
713 The Excess Burst Size is defined together with the Committed Rate,
714 see section 4.3.1.6 below.
716 4.3.1.5 Peak Rate Token Bucket
718 The Peak Rate of a CR-LSP is specified in terms of a token bucket P
719 with token rate PDR and maximum token bucket size PBS.
721 The token bucket P is initially (at time 0) full, i.e., the token
722 count Tp(0) = PBS. Thereafter, the token count Tp, if less than
723 PBS, is incremented by one PDR times per second. When a packet of
724 size B bytes arrives at time t, the following happens:
726 - If Tp(t)-B >= 0, the packet is not in excess of the peak rate
727 and Tp is decremented by B down to the minimum value of 0, else
729 - the packet is in excess of the peak rate and Tp is not
730 decremented.
732 Note that according to the above definition, a positive infinite
733 value of either PDR or PBS implies that arriving packets are never
734 in excess of the peak rate.
736 The actual implementation of an LSR doesn't need to be modeled
737 according to the above formal token bucket specification.
739 4.3.1.6 Committed Data Rate Token Bucket
741 The committed rate of a CR-LSP is specified in terms of a token
742 bucket C with rate CDR. The extent by which the offered rate
743 exceeds the committed rate MAY be measured in terms of another token
744 bucket E, which also operates at rate CDR. The maximum size of the
745 token bucket C is CBS and the maximum size of the token bucket E is
746 EBS.
748 The token buckets C and E are initially (at time 0) full, i.e., the
749 token count Tc(0) = CBS and the token count Te(0) = EBS.
750 Thereafter, the token counts Tc and Te are updated CDR times per
751 second as follows:
753 - If Tc is less than CBS, Tc is incremented by one, else
754 - if Te is less then EBS, Te is incremented by one, else
755 - neither Tc nor Te is incremented.
757 When a packet of size B bytes arrives at time t, the following
758 happens:
760 - If Tc(t)-B >= 0, the packet is not in excess of the Committed
761 Rate and Tc is decremented by B down to the minimum value of 0,
762 else
763 - if Te(t)-B >= 0, the packet is in excess of the Committed rate
764 but is not in excess of the EBS and Te is decremented by B down
765 to the minimum value of 0, else
766 - the packet is in excess of both the Committed Rate and the EBS
767 and neither Tc nor Te is decremented.
769 Note that according to the above specification, a CDR value of
770 positive infinity implies that arriving packets are never in excess
771 of either the Committed Rate or EBS. A positive infinite value of
772 either CBS or EBS implies that the respective limit cannot be
773 exceeded.
775 The actual implementation of an LSR doesn't need to be modeled
776 according to the above formal specification.
778 4.3.1.7 Weight
780 The weight determines the CR-LSP's relative share of the possible
781 excess bandwidth above its committed rate. The definition of
782 _relative share_ is MPLS domain specific.
784 4.3.2 Procedures
786 4.3.2.1 Label Request Message
788 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
789 which the value of PDR is less than the value of CDR then it MUST
790 send a Notification Message including the Status code _Traffic
791 Parameters Unavailable_ to the upstream LSR from which it received
792 the erroneous message.
794 If a Traffic Parameter is indicated as Negotiable in the Label
795 Request Message by the corresponding Negotiable Flag then an LSR MAY
796 replace the Traffic Parameter value with a smaller value.
798 If the Weight is indicated as Negotiable in the Label Request
799 Message by the corresponding Negotiable Flag then an LSR may replace
800 the Weight value with a lower value (down to 0).
802 If, after possible Traffic Parameter negotiation, an LSR can support
803 the CR-LSP Traffic Parameters then the LSR MUST reserve the
804 corresponding resources for the CR-LSP.
806 If, after possible Traffic Parameter negotiation, an LSR cannot
807 support the CR-LSP Traffic Parameters then the LSR MUST send a
808 Notification Message that contains the _Resource Unavailable_ status
809 code.
811 4.3.2.2 Label Mapping Message
813 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
814 which the value of PDR is less than the value of CDR then it MUST
815 send a Label Release message containing the Status code _Traffic
816 Parameters Unavailable_ to the LSR from which it received the
817 erroneous message. In addition, the LSP should send a Notification
818 Message upstream with the status code _Label Request Aborted_.
820 If the negotiation flag was set in the label request message, the
821 egress LSR MUST include the (possibly negotiated) Traffic Parameters
822 and Weight in the Label Mapping message.
824 The Traffic Parameters and the Weight in a Label Mapping message
825 MUST be forwarded unchanged.
827 An LSR SHOULD adjust the resources that it reserved for a CR-LSP
828 when it receives a Label Mapping Message if the Traffic Parameters
829 differ from those in the corresponding Label Request Message.
831 4.3.2.3 Notification Message
833 If an LSR receives a Notification Message for a CR-LSP, it SHOULD
834 release any resources that it possibly had reserved for the CR-LSP.
835 In addition, on receiving a Notification Message from a Downstream
836 LSR that is associated with a Label Request from an upstream LSR,
837 the local LSR MUST propagate the Notification message using the
838 procedures in [1].
840 4.4 Preemption TLV
842 The defualt value of the setup and holding priorities should be in
843 the middle of the range (e.g., 4) so that this feature can be turned
844 on gradually in an operational network by increasing or decreasing
845 the priority starting at the middle of the range.
847 Since the Preemption TLV is an optional TLV, LSPs that are setup
848 without an explicitly signaled preemption TLV SHOULD be treated as
849 LSPs with the default setup and holding priorities (e.g., 4).
851 When an established LSP is preempted, the LSR that initiates the
852 preemption sends a Withdraw Message upstream and a Release Message
853 downstream.
855 When an LSP in the process of being established (outstanding Label
856 Request without getting a Label Mapping back) is preempted, the LSR
857 that initiates the preemption, sends a Notification Message upstream
858 and an Abort Message downstream.
860 0 1 2 3
861 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
862 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
863 |0|0| Type = 0x0820 | Length = 4 |
864 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
865 | SetPrio | HoldPrio | Reserved |
866 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
868 Type
869 A fourteen-bit field carrying the value of the Preemption-TLV
870 Type = 0x0820.
872 Length
873 Specifies the length of the value field in bytes = 4.
875 Reserved
876 Zero on transmission. Ignored on receipt.
878 SetPrio
879 A SetupPriority of value zero (0) is the priority assigned to
880 the most important path. It is referred to as the highest
881 priority. Seven (7) is the priority for the least important
882 path. The higher the setup priority, the more paths CR-LDP can
883 bump to set up the path. The default value should be 4.
885 HoldPrio
886 A HoldingPriority of value zero (0) is the priority assigned to
887 the most important path. It is referred to as the highest
888 priority. Seven (7) is the priority for the least important
889 path. The default value should be 4.
890 The higher the holding priority, the less likely it is for CR-
891 LDP to reallocate its bandwidth to a new path.
893 4.5 LSPID TLV
895 LSPID is a unique identifier of a CR-LSP within an MPLS network.
897 The LSPID is composed of the ingress LSR Router ID (or any of its
898 own Ipv4 addresses) and a Locally unique CR-LSP ID to that LSR.
900 The LSPID is useful in network management, in CR-LSP repair, and in
901 using an already established CR-LSP as a hop in an ER-TLV.
903 An _action indicator flag_ is carried in the LSPID TLV. This _action
904 indicator flag_ indicates explicitly the action that should be taken
905 if the LSP already exists on the LSR receiving the message.
907 After a CR-LSP is set up, its bandwidth reservation may need to be
908 changed by the network operator, due to the new requirements for the
909 traffic carried on that CR-LSP. The _action indicator flag_ is used
910 indicate the need to modify the bandwidth and possibly other
911 parameters of an established CR-LSP without service interruption.
912 This feature has application in dynamic network resources management
913 where traffic of different priorities and service classes is
914 involved.
916 The procedure for the code point _modify_ is defined in [9]. The
917 procedures for other flags are FFS.
919 0 1 2 3
920 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
921 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
922 |0|0| Type = 0x0821 | Length = 4 |
923 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
924 | Reserved |ActFlg | Local CR-LSP ID |
925 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
926 | Ingress LSR Router ID |
927 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
929 Type
930 A fourteen-bit field carrying the value of the LSPID-TLV
931 Type = 0x0821.
933 Length
934 Specifies the length of the value field in bytes = 4.
936 ActFlg
937 Action Indicator Flag: A 4-bit field that indicates explicitly
938 the action that should be taken if the LSP already exists on
939 the LSR receiving the message. A set of indicator code points
940 is proposed as follows:
942 0000: indicates initial LSP setup
943 0001: indicates modify LSP
944 Reserved
945 Zero on transmission. Ignored on receipt.
947 Local CR-LSP ID
948 The Local LSP ID is an identifier of the CR-LSP locally unique
949 within the Ingress LSR originating the CR-LSP.
951 Ingress LSR Router ID
952 An LSR may use any of its own IPv4 addresses in this field.
954 4.6 Resource Class (Color) TLV
956 The Resource Class as defined in [4] is used to specify which links
957 are acceptable by this CR-LSP. This information allows for the
958 network's topology to be pruned.
960 0 1 2 3
961 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
962 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
963 |0|0| Type = 0x0822 | Length = 4 |
964 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
965 | RsCls |
966 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
968 Type
969 A fourteen-bit field carrying the value of the ResCls-TLV Type
970 = 0x0822.
972 Length
973 Specifies the length of the value field in bytes = 4.
975 RsCls
976 The Resource Class bit mask indicating which of the 32
977 _administrative groups_ or _colors_ of links the CR-LSP can
978 traverse.
980 4.7 ER-Hop semantics
982 4.7.1. ER-Hop 1: The IPv4 prefix
984 The abstract node represented by this ER-Hop is the set of nodes,
985 which have an IP address, which lies within this prefix. Note that
986 a prefix length of 32 indicates a single IPv4 node.
988 0 1 2 3
989 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
990 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
991 |0|0| Type = 0x0801 | Length = 8 |
992 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
993 |L| Reserved | PreLen |
994 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
995 | IPv4 Address (4 bytes) |
996 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
998 Type
999 A fourteen-bit field carrying the value of the ER-Hop 1, IPv4
1000 Address, Type = 0x0801
1002 Length
1003 Specifies the length of the value field in bytes = 8.
1005 L Bit
1006 Set to indicate Loose hop.
1007 Cleared to indicate a strict hop.
1009 Reserved
1010 Zero on transmission. Ignored on receipt.
1012 PreLen
1013 Prefix Length 1-32
1015 IP Address
1016 A four-byte field indicating the IP Address.
1018 4.7.2. ER-Hop 2: The IPv6 address
1020 0 1 2 3
1021 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
1022 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1023 |0|0| 0x0802 | Length = 20 |
1024 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1025 |L| Reserved | PreLen |
1026 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1027 | IPV6 address |
1028 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1029 | IPV6 address (continued) |
1030 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1031 | IPV6 address (continued) |
1032 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1033 | IPV6 address (continued) |
1034 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1036 Type
1037 A fourteen-bit field carrying the value of the ER-Hop 2, IPv6
1038 Address, Type = 0x0802
1040 Length
1041 Specifies the length of the value field in bytes = 20.
1043 L Bit
1044 Set to indicate Loose hop.
1045 Cleared to indicate a strict hop.
1047 Reserved
1048 Zero on transmission. Ignored on receipt.
1050 PreLen
1051 Prefix Length 1-128
1053 IPv6 address
1054 A 128-bit unicast host address.
1056 4.7.3. ER-Hop 3: The autonomous system number
1058 The abstract node represented by this ER-Hop is the set of nodes
1059 belonging to the autonomous system.
1061 0 1 2 3
1062 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
1063 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1064 |0|0| 0x0803 | Length = 4 |
1065 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1066 |L| Reserved | AS Number |
1067 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1069 Type
1070 A fourteen-bit field carrying the value of the ER-Hop 3, AS
1071 Number, Type = 0x0803
1073 Length
1074 Specifies the length of the value field in bytes = 4.
1076 L Bit
1077 Set to indicate Loose hop.
1078 Cleared to indicate a strict hop.
1080 Reserved
1081 Zero on transmission. Ignored on receipt.
1083 AS Number
1084 Autonomous System number
1086 4.7.4. ER-Hop 4: LSPID
1088 The LSPID is used to identify the tunnel ingress point as the next
1089 hop in the ER. This ER-Hop allows for stacking new CR-LSPs within an
1090 already established CR-LSP. It also allows for splicing the CR-LSP
1091 being established with an existing CR-LSP.
1093 If an LSPID Hop is the last ER-Hop in an ER-TLV, than the LSR may
1094 splice the CR-LSP of the incoming Label Request to the CR-LSP that
1095 currently exists with this LSPID. This is useful, for example, at
1096 the point at which a Label Request used for local repair arrives at
1097 the next ER-Hop after the loosely specified CR-LSP segment. Use of
1098 the LSPID Hop in this scenario eliminates the need for ER-Hops to
1099 keep the entire remaining ER-TLV at each LSR that is at either
1100 (upstream or downstream) end of a loosely specified CR-LSP segment
1101 as part of its state information. This is due to the fact that the
1102 upstream LSR needs only to keep the next ER-Hop and the LSPID and
1103 the downstream LSR needs only to keep the LSPID in order for each
1104 end to be able to recognize that the same LSP is being identified.
1106 If the LSPID Hop is not the last hop in an ER-TLV, the LSR must
1107 remove the LSP-ID Hop and forward the remaining ER-TLV in a Label
1108 Request message using an LDP session established with the LSR that
1109 is the specified CR-LSP's egress. That LSR will continue processing
1110 of the CR-LSP Label Request Message. The result is a tunneled, or
1111 stacked, CR-LSP.
1113 To support labels negotiated for tunneled CR-LSP segments, an LDP
1114 session is required [1] between tunnel end points - possibly using
1115 the existing CR-LSP. Use of the existence of the CR-LSP in lieu of
1116 a session, or other possible session-less approaches, is FFS.
1118 0 1 2 3
1119 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
1120 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1121 |0|0| 0x0804 | Length = 8 |
1122 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1123 |L| Reserved | Local LSPID |
1124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1125 | Ingress LSR Router ID |
1126 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1128 Type
1129 A fourteen-bit field carrying the value of the ER-Hop 4, LSPID,
1130 Type = 0x0804
1132 Length
1133 Specifies the length of the value field in bytes = 8.
1135 L Bit
1136 Set to indicate Loose hop.
1137 Cleared to indicate a strict hop.
1139 Reserved
1140 Zero on transmission. Ignored on receipt.
1142 Local LSPID
1143 A 2 byte field indicating the LSPID which is unique with
1144 reference to its Ingress LSR.
1146 Ingress LSR Router ID
1147 An LSR may use any of its own IPv4 addresses in this field.
1149 4.8. Processing of the Explicit Route TLV
1151 4.8.1. Selection of the next hop
1153 A Label Request Message containing an explicit route TLV must
1154 determine the next hop for this path. Selection of this next hop
1155 may involve a selection from a set of possible alternatives. The
1156 mechanism for making a selection from this set is implementation
1157 dependent and is outside of the scope of this specification.
1159 Selection of particular paths is also outside of the scope of this
1160 specification, but it is assumed that each node will make a best
1161 effort attempt to determine a loop-free path. Note that such best
1162 efforts may be overridden by local policy.
1164 To determine the next hop for the path, a node performs the
1165 following steps:
1167 1. The node receiving the Label Request Message must first
1168 evaluate the first ER-Hop. If the L bit is not set in the
1169 first ER-Hop and if the node is not part of the abstract node
1170 described by the first ER-Hop, it has received the message in
1171 error, and should return a _Bad Initial ER-Hop_ error. If the
1172 L bit is set and the local node is not part of the abstract
1173 node described by the first ER-Hop, the node selects a next
1174 hop that is along the path to the abstract node described by
1175 the first ER-Hop. If there is no first ER-Hop, the message is
1176 also in error and the system should return a _Bad Explicit
1177 Routing TLV_ error using a Notification Message sent upstream.
1179 2. If there is no second ER-Hop, this indicates the end of the
1180 explicit route. The explicit route TLV should be removed from
1181 the Label Request Message. This node may or may not be the
1182 end of the LSP. Processing continues with section 4.8.2,
1183 where a new explicit route TLV may be added to the Label
1184 Request Message.
1186 3. If the node is also a part of the abstract node described by
1187 the second ER-Hop, then the node deletes the first ER-Hop and
1188 continues processing with step 2, above. Note that this makes
1189 the second ER-Hop into the first ER-Hop of the next iteration.
1191 4. The node determines if it is topologically adjacent to the
1192 abstract node described by the second ER-Hop. If so, the node
1193 selects a particular next hop which is a member of the
1194 abstract node. The node then deletes the first ER-Hop and
1195 continues processing with section 4.8.2.
1197 5. Next, the node selects a next hop within the abstract node of
1198 the first ER-Hop that is along the path to the abstract node
1199 of the second ER-Hop. If no such path exists then there are
1200 two cases:
1202 5.a If the second ER-Hop is a strict ER-Hop, then there is
1203 an error and the node should return a _Bad Strict Node_
1204 error.
1206 5.b Otherwise, if the second ER-Hop is a loose ER-Hop, then
1207 the node selects any next hop that is along the path to the
1208 next abstract node. If no path exists within the MPLS
1209 domain, then there is an error, and the node should return a
1210 _Bad loose node_ error.
1212 6. Finally, the node replaces the first ER-Hop with any ER-Hop
1213 that denotes an abstract node containing the next hop. This
1214 is necessary so that when the explicit route is received by
1215 the next hop, it will be accepted.
1217 7. Progress the Label Request Message to the next hop.
1219 4.8.2. Adding ER-Hops to the explicit route TLV
1221 After selecting a next hop, the node may alter the explicit route in
1222 the following ways.
1224 If, as part of executing the algorithm in section 4.8.1, the
1225 explicit route TLV is removed, the node may add a new explicit route
1226 TLV.
1228 Otherwise, if the node is a member of the abstract node for the
1229 first ER-Hop, then a series of ER-Hops may be inserted before the
1230 first ER-Hop or may replace the first ER-Hop. Each ER-Hop in this
1231 series must denote an abstract node that is a subset of the current
1232 abstract node.
1234 Alternately, if the first ER-Hop is a loose ER-Hop, an arbitrary
1235 series of ER-Hops may be inserted prior to the first ER-Hop.
1237 4.9 Route Pinning TLV
1239 Section 2.4 describes the use of route pinning. The encoding of the
1240 Route Pinning TLV is as follows:
1242 0 1 2 3
1243 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
1244 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1245 |0|0| Type = 0x0823 | Length = 4 |
1246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1247 |P| Reserved |
1248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1250 Type
1251 A fourteen-bit field carrying the value of the Pinning-TLV
1252 Type = 0x0823
1254 Length
1255 Specifies the length of the value field in bytes = 4.
1257 P Bit
1258 The P bit is set to 1 to indicate that route pinning is
1259 requested.
1260 The P bit is set to 0 to indicate that route pinning is not
1261 requested
1262 Reserved
1263 Zero on transmission. Ignored on receipt.
1265 4.10 CR-LSP FEC Element
1267 A new FEC element is introduced in this specification to support CR-
1268 LSPs. A FEC TLV containing a FEC of Element type CR-LSP (0x04) is a
1269 CR-LSP FEC TLV. The CR-LSP FEC Element is an opaque FEC to be used
1270 only in Messages of CR-LSPs.
1272 A single FEC element MUST be included in the Label Request Message.
1273 The FEC Element SHOULD be the CR-LSP FEC Element. However, one of
1274 the other FEC elements (Type=0x01, 0x02, 0x03) defined in [1] MAY be
1275 in CR-LDP messages instead of the CR-LSP FEC Element for certain
1276 applications. A FEC TLV containing a FEC of Element type CR-LSP
1277 (0x04) is a CR-LSP FEC TLV.
1279 FEC Element Type Value
1280 Type name
1282 CR-LSP 0x04 No value; i.e., 0 value octets;
1284 The CR-LSP FEC TLV encoding is as follows:
1286 0 1 2 3
1287 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
1288 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1289 |0|0| Type = 0x0100 | Length = 1 |
1290 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1291 | CR-LSP (4) |
1292 +-+-+-+-+-+-+-+-+
1294 Type
1295 A fourteen-bit field carrying the value of the FEC TLV
1296 Type = 0x0100
1298 Length
1299 Specifies the length of the value field in bytes = 1.
1301 CR-LSP FEC Element Type
1302 0x04
1304 4.11 TLV Type Summary
1306 TLV Type
1307 -------------------------------------- ----------
1308 Explicit Route TLV 0x0800
1309 Ipv4 Prefix ER-Hop TLV 0x0801
1310 Ipv6 Prefix ER-Hop TLV 0x0802
1311 Autonomous System Number ER-Hop TLV 0x0803
1312 LSP-ID ER-Hop TLV 0x0804
1313 Traffic Parameters TLV 0x0810
1314 Preemption TLV 0x0820
1315 LSPID TLV 0x0821
1316 Resource Class TLV 0x0822
1317 Route Pinning TLV 0x0823
1319 4.12 FEC Type Summary
1321 FEC Element TLV Type
1322 -------------------------------------- ----------
1323 CR-LSP FEC Element TLV 0x0100
1325 4.13 Status Code Summary
1327 Status Code Type
1328 -------------------------------------- ----------
1329 Bad Explicit Routing TLV Error 0x44000001
1330 Bad Strict Node Error 0x44000002
1331 Bad Loose Node Error 0x44000003
1332 Bad Initial ER-Hop Error 0x44000004
1333 Resource Unavailable 0x44000005
1334 Traffic Parameters Unavailable 0x44000006
1335 LSP Preempted 0x44000007
1336 Modify Request Not Supported 0x44000008
1337 Setup Abort (Label Request Aborted in [1]) 0x04000015
1339 5. IANA Considerations
1341 CR-LDP defines the following name spaces, which require management:
1343 - TLV types.
1344 - FEC types.
1345 - Status codes.
1347 The following sections provide guidelines for managing these name
1348 spaces.
1350 5.1 TLV Type Name Space
1352 TLV types in the range 0x0800 - 0x08FF are allocated to CR-LDP base
1353 protocol. Following the policies outlined in [IANA], TLV types in
1354 this range are allocated through an IETF Consensus action.
1356 5.2 FEC Type Name Space
1358 FEC Type 100 is allocated to CR-LDP.
1360 5.3 Status Code Space
1362 The range for Status Codes is 0x44000000 - 0x440000FF.
1364 Following the policies outlined in [IANA], Status Codes in the range
1365 0x44000000 - 0x440000FF are allocated through an IETF Consensus
1366 action.
1368 6. Security
1370 CR-LDP inherits the same security mechanism described in Section 4.0
1371 of [1] to protect against the introduction of spoofed TCP segments
1372 into LDP session connection streams.
1374 7. Acknowledgments
1376 The messages used to signal the CR-LSP setup are based on the work
1377 done by the [1] team.
1379 The authors would also like to acknowledge the careful review and
1380 comments of Ken Hayward, Greg Wright, Geetha Brown, Brian Williams,
1381 Paul Beaubien, Matthew Yuen, Liam Casey, Ankur Anand, Adrian Farrel.
1383 8. Intellectual Property Consideration
1385 The IETF has been notified of intellectual property rights claimed
1386 in regard to some or all of the specification contained in this
1387 document. For more information consult the online list of claimed
1388 rights.
1390 9. References
1392 1 Andersson et al, "Label Distribution Protocol Specification"
1393 work in progress (draft-ietf-mpls-ldp-08), June 2000.
1395 2 Callon et al, "Framework for Multiprotocol Label Switching",
1396 work in progress (draft-ietf-mpls-framework-05), September 1999.
1398 3 Rosen et al, "Multiprotocol Label Switching Architecture",
1399 work in progress (draft-ietf-mpls-arch-06), August 1999.
1401 4 Awduche et al, "Requirements for Traffic Engineering Over
1402 MPLS", RFC 2702, September 1999.
1404 5 B. Gleeson, et. al., "A Framework for IP Based Virtual Private
1405 Networks", RFC 2764, February 2000.
1407 6 B. Jamoussi, et. al., _Applicability Statement for CR-LDP_, work
1408 in progress, (draft-ietf-mpls-crldp-applic-01), June 2000.
1410 7 S. Bradner, "Key words for use in RFCs to Indicate Requirement
1411 Levels_, RFC 2119, March 1997.
1413 8 L. Wu, et. al., "LDP State Machine", work in progress,
1414 (draft-ietf-mpls-ldp-state-03), January 2000.
1416 9 J. Ash, et. al., "LSP Modification Using CR-LDP", work in
1417 progress, (draft-ietf-mpls-crlsp-modify-01), February 2000.
1419 10. Author's Addresses
1421 Osama S. Aboul-Magd Loa Andersson
1422 Nortel Networks Nortel Networks
1423 P O Box 3511 Station C S:t Eriksgatan 115
1424 Ottawa, ON K1Y 4H7 PO Box 6701
1425 Canada 113 85 Stockholm
1426 Phone: +1 613 763-5827 Tel: +46 8 508 835 00
1427 Osama@nortelnetworks.com Fax: +46 8 508 835 01
1428 Loa_andersson@nortelnetworks.com
1430 Peter Ashwood-Smith Ross Callon
1431 Nortel Networks Juniper Networks
1432 P O Box 3511 Station C 1194 North Mathilda Avenue,
1433 Ottawa, ON K1Y 4H7 Sunnyvale, CA 94089
1434 Canada 978-692-6724
1435 Phone: +1 613 763-4534 rcallon@juniper.net
1436 Petera@nortelnetworks.com
1438 Ram Dantu Paul Doolan
1439 IPmobile Ennovate Networks
1440 1651 North Glenville, Suite 216 330 Codman Hill Rd
1441 Richardson, TX 75081 Marlborough MA 01719
1442 +1-972-234-6070 extension 211 Phone: 978-263-2002
1443 rdantu@ipmobile.com Pdoolan@ennovatenetworks.com
1445 Nancy Feldman Andre Fredette
1446 IBM Corp. PhotonEx Corporation
1447 17 Skyline Drive 135 South Road
1448 Hawthorne NY 10532 Bedford, MA 01730
1449 Phone: 914-784-3254 email: fredette@photonex.com
1450 Nkf@us.ibm.com phone: 781-275-8500
1452 Eric Gray Joel M. Halpern
1453 Zaffire, Inc Longitude Systems, Inc.
1454 2630 Orchard Parkway, 1319 Shepard Road
1455 San Jose, CA 95134-2020 Sterling, VA 20164
1456 Phone: 408-894-7362 703-433-0808 x207
1457 egray@zaffire.com joel@longsys.com
1459 Juha Heinanen Fiffi Hellstrand
1460 Telia Finland, Inc. Nortel Networks
1461 Myyrmaentie 2 S:t Eriksgatan 115
1462 01600 VANTAA PO Box 6701, 113 85 Stockholm
1463 Finland Sweden
1464 Tel: +358 41 500 4808 +46705593687
1465 Jh@telia.fi fiffi@nortelnetworks.com
1466 Bilel Jamoussi Timothy E. Kilty
1467 Nortel Networks Corp. Newbridge Networks, Inc.
1468 600 Technology Park Drive 5 Corporate Drive
1469 Billerica, MA 01821 Andover, MA 01810
1470 USA USA
1471 Phone: +1 978 288-4506 phone: 978 691-4656
1472 Jamoussi@nortelnetworks.com tkilty@northchurch.net
1474 Andrew G. Malis Muckai K Girish
1475 Vivace Networks Atoga Systems
1476 2730 Orchard Parkway 49026 Milmont Drive
1477 San Jose, CA 95134 Fremont, CA 94538
1478 Andy.Malis@vivacenetworks.com E-mail: muckai@atoga.com
1479 Tel: +1 408 383 7223
1480 Fax: +1 408 904 4748
1482 Kenneth Sundell Pasi Vaananen
1483 Nortel Networks Nokia Telecommunications
1484 S:t Eriksgatan 115 3 Burlington Woods Drive,
1485 PO Box 6701 Burlington, MA 01803
1486 113 85 Stockholm Phone: +1-781-238-4981
1487 Tel: +46 8 508 835 00 pasi.vaananen@nokia.com
1488 Fax: +46 8 508 835 01
1489 Ksundell@nortelnetworks.com
1491 Tom Worster Liwen Wu
1492 Ennovate Networks Cisco Systems
1493 60 Codman Hill Rd 250 Apollo Drive
1494 Boxborough Chelmsford, MA. 01824
1495 MA 01719 Tel: 978-244-3087.
1496 tworster@ennovatenetworks.com liwwu@cisco.com
1497 Appendix A: CR-LSP Establishment Examples
1499 A.1 Strict Explicit Route Example
1501 This appendix provides an example for the setup of a strictly routed
1502 CR-LSP. In this example, a specific node represents each abstract
1503 node.
1505 The sample network used here is a four node network with two edge
1506 LSRs and two core LSRs as follows:
1508 abc
1509 LSR1------LSR2------LSR3------LSR4
1511 LSR1 generates a Label Request Message as described in Section 3.1
1512 of this draft and sends it to LSR2. This message includes the CR-
1513 TLV.
1515 A vector of three ER-Hop TLVs composes the ER-TLV.
1516 The ER-Hop TLVs used in this example are of type 0x0801 (IPv4
1517 prefix) with a prefix length of 32. Hence, each ER-Hop TLV
1518 identifies a specific node as opposed to a group of nodes.
1519 At LSR2, the following processing of the ER-TLV per Section 4.8.1 of
1520 this draft takes place:
1522 1) The node LSR2 is part of the abstract node described by the
1523 first hop . Therefore, the first step passes the test.
1524 Go to step 2.
1526 2) There is a second ER-Hop, . Go to step 3.
1528 3) LSR2 is not part of the abstract node described by the
1529 second ER-Hop . Go to Step 4.
1531 4) LSR2 determines that it is topologically adjacent to the
1532 abstract node described by the second ER-Hop . LSR2
1533 selects a next hop (LSR3) which is the abstract node. LSR2
1534 deletes the first ER-Hop from the ER-TLV, which now
1535 becomes . Processing continues with Section 4.8.2.
1537 At LSR2, the following processing of Section 4.8.2 takes place:
1538 Executing algorithm 4.8.1 did not result in the removal of the ER-
1539 TLV.
1541 Also, LSR2 is not a member of the abstract node described by the
1542 first ER-Hop .
1544 Finally, the first ER-Hop is a strict hop.
1546 Therefore, processing section 4.8.2 does not result in the insertion
1547 of new ER-Hops. The selection of the next hop has been already done
1548 is step 4 of Section 4.8.1 and the processing of the ER-TLV is
1549 completed at LSR2. In this case, the Label Request Message including
1550 the ER-TLV is progressed by LSR2 to LSR3.
1552 At LSR3, a similar processing to the ER-TLV takes place except that
1553 the incoming ER-TLV = and the outgoing ER-TLV is .
1555 At LSR4, the following processing of section 4.8.1 takes place:
1557 1) The node LSR4 is part of the abstract node described by the
1558 first hop . Therefore, the first step passes the test. Go
1559 to step 2.
1560 2) There is no second ER-Hop, this indicates the end of the CR-
1561 LSP. The ER-TLV is removed from the Label Request Message.
1562 Processing continues with Section 4.8.2.
1564 At LSR4, the following processing of Section 4.8.2 takes place:
1565 Executing algorithm 4.8.1 resulted in the removal of the ER-TLV.
1566 LSR4 does not add a new ER-TLV.
1568 Therefore, processing section 4.8.2 does not result in the insertion
1569 of new ER-Hops. This indicates the end of the CR-LSP and the
1570 processing of the ER-TLV is completed at LSR4.
1572 At LSR4, processing of Section 3.2 is invoked. The first condition
1573 is satisfied (LSR4 is the egress end of the CR-LSP and upstream
1574 mapping has been requested). Therefore, a Label Mapping Message is
1575 generated by LSR4 and sent to LSR3.
1577 At LSR3, the processing of Section 3.2 is invoked. The second
1578 condition is satisfied (LSR3 received a mapping from its downstream
1579 next hop LSR4 for a CR-LSP for which an upstream request is still
1580 pending). Therefore, a Label Mapping Message is generated by LSR3
1581 and sent to LSR2.
1583 At LSR2, a similar processing to LSR 3 takes place and a Label
1584 Mapping Message is sent back to LSR1, which completes the end-to-end
1585 CR-LSP setup.
1587 A.2 Node Groups and Specific Nodes Example
1589 A request at ingress LSR to setup a CR-LSP might originate from a
1590 management system or an application, the details are implementation
1591 specific.
1593 The ingress LSR uses information provided by the management system
1594 or the application and possibly also information from the routing
1595 database to calculate the explicit route and to create the Label
1596 Request Message.
1598 The Label request message carries together with other necessary
1599 information an ER-TLV defining the explicitly routed path. In our
1600 example the list of hops in the ER-Hop TLV is supposed to contain an
1601 abstract node representing a group of nodes, an abstract node
1602 representing a specific node, another abstract node representing a
1603 group of nodes, and an abstract node representing a specific egress
1604 point.
1606 In--{Group 1}--{Specific A}--{Group 2}--{Specific Out: B}
1607 The ER-TLV contains four ER-Hop TLVs:
1609 1. An ER-Hop TLV that specifies a group of LSR valid for the
1610 first abstract node representing a group of nodes (Group 1).
1612 2. An ER-Hop TLV that indicates the specific node (Node A).
1614 3. An ER-Hop TLV that specifies a group of LSRs valid for the
1615 second abstract node representing a group of nodes (Group
1616 2).
1618 4. An ER-Hop TLV that indicates the specific egress point for
1619 the CR-LSP (Node B).
1621 All the ER-Hop TLVs are strictly routed nodes.
1622 The setup procedure for this CR-LSP works as follows:
1624 1. The ingress node sends the Label Request Message to a node
1625 that is a member the group of nodes indicated in the first
1626 ER-Hop TLV, following normal routing for the specific node
1627 (A).
1629 2. The node that receives the message identifies itself as part
1630 of the group indicated in the first ER-Hop TLV, and that it
1631 is not the specific node (A) in the second. Further it
1632 realizes that the specific node (A) is not one of its next
1633 hops.
1635 3. It keeps the ER-Hop TLVs intact and sends a Label Request
1636 Message to another node that is part of the group indicated
1637 in the first ER-Hop TLV (Group 1), following normal routing
1638 for the specific node (A).
1640 4. The node that receives the message identifies itself as part
1641 of the group indicated in the first ER-Hop TLV, and that it
1642 is not the specific node (A) in the second ER-Hop TLV.
1643 Further it realizes that the specific node (A) is one of its
1644 next hops.
1646 5. It removes the first ER-Hop TLVs and sends a Label Request
1647 Message to the specific node (A).
1649 6. The specific node (A) recognizes itself in the first ER-Hop
1650 TLV. Removes the specific ER-Hop TLV.
1652 7. It sends a Label Request Message to a node that is a member
1653 of the group (Group 2) indicated in the ER-Hop TLV.
1655 8. The node that receives the message identifies itself as part
1656 of the group indicated in the first ER-Hop TLV, further it
1657 realizes that the specific egress node (B) is one of its
1658 next hops.
1660 9. It sends a Label Request Message to the specific egress node
1661 (B).
1663 10.The specific egress node (B) recognizes itself as the egress
1664 for the CR-LSP, it returns a Label Mapping Message, that
1665 will traverse the same path as the Label Request Message in
1666 the opposite direction.
1668 Appendix B. QoS Service Examples
1670 B.1 Service Examples
1672 Construction of an end-to-end service is the result of the rules
1673 enforced at the edge and the treatment that packets receive at the
1674 network nodes. The rules define the traffic conditioning actions
1675 that are implemented at the edge and they include policing with
1676 pass, mark, and drop capabilities. The edge rules are expected tobe
1677 defined by the mutual agreements between the service providers and
1678 their customers and they will constitute an essential part of the
1679 SLA. Therefore edge rules are not included in the signaling
1680 protocol.
1682 Packet treatment at a network node is usually referred to as the
1683 local behavior. Local behavior could be specified in many ways. One
1684 example for local behavior specification is the service frequency
1685 introduced in section 4.3.2.1, together with the resource
1686 reservation rules implemented at the nodes.
1688 Edge rules and local behaviors can be viewed as the main building
1689 blocks for the end-to-end service construction. The following table
1690 illustrates the applicability of the building block approach for
1691 constructing different services including those defined for ATM.
1693 Service PDR PBS CDR CBS EBS Service Conditioning
1694 Examples Frequency Action
1696 DS S S =PDR =PBS 0 Frequent drop>PDR
1698 TS S S S S 0 Unspecified drop>PDR,PBS
1699 mark>CDR,CBS
1701 BE inf inf inf inf 0 Unspecified -
1703 FRS S S CIR ~B_C ~B_E Unspecified drop>PDR,PBS
1704 mark>CDR,CBS,EBS
1706 ATM-CBR PCR CDVT =PCR =CDVT 0 VeryFrequent drop>PCR
1708 ATM-VBR.3(rt) PCR CDVT SCR MBS 0 Frequent drop>PCR
1709 mark>SCR,MBS
1711 ATM-VBR.3(nrt) PCR CDVT SCR MBS 0 Unspecified drop>PCR
1712 mark>SCR,MBS
1714 ATM-UBR PCR CDVT - - 0 Unspecified drop>PCR
1716 ATM-GFR.1 PCR CDVT MCR MBS 0 Unspecified drop>PCR
1718 ATM-GFR.2 PCR CDVT MCR MBS 0 Unspecified drop>PCR
1719 mark>MCR,MFS
1720 int-serv-CL p m r b 0 Frequent drop>p
1721 drop>r,b
1723 S= User specified
1725 In the above table, the DS refers to a delay sensitive service where
1726 the network commits to deliver with high probability user datagrams
1727 at a rate of PDR with minimum delay and delay requirements.
1728 Datagrams in excess of PDR will be discarded.
1730 The TS refers to a generic throughput sensitive service where the
1731 network commits to deliver with high probability user datagrams at a
1732 rate of at least CDR. The user may transmit at a rate higher than
1733 CDR but datagrams in excess of CDR would have a lower probability of
1734 being delivered.
1736 The BE is the best effort service and it implies that there are no
1737 expected service guarantees from the network.
1739 B.2 Establishing CR-LSP Supporting Real-Time Applications
1741 In this scenario the customer needs to establish an LSP for
1742 supporting real-time applications such as voice and video. The
1743 Delay-sensitive (DS) service is requested in this case.
1745 The first step is the specification of the traffic parameters in the
1746 signaling message. The two parameters of interest to the DS service
1747 are the PDR and the PBS and the user based on his requirements
1748 specifies their values. Since all the traffic parameters are
1749 included in the signaling message, appropriate values must be
1750 assigned to all of them. For DS service, the CDR and the CBS values
1751 are set equal to the PDR and the PBS respectively. An indication of
1752 whether the parameter values are subject to negotiation is flagged.
1754 The transport characteristics of the DS service require Frequent
1755 frequency to be requested to reflect the real-time delay
1756 requirements of the service.
1758 In addition to the transport characteristics, both the network
1759 provider and the customer need to agree on the actions enforced at
1760 the edge. The specification of those actions is expected to be a
1761 part of the service level agreement (SLA) negotiation and is not
1762 included in the signaling protocol. For DS service, the edge action
1763 is to drop packets that exceed the PDR and the PBS specifications.
1764 The signaling message will be sent in the direction of the ER path
1765 and the LSP is established following the normal LDP procedures. Each
1766 LSR applies its admission control rules. If sufficient resources are
1767 not available and the parameter values are subject to negotiation,
1768 then the LSR could negotiate down the PDR, the PBS, or both.
1770 The new parameter values are echoed back in the Label Mapping
1771 Message. LSRs might need to re-adjust their resource reservations
1772 based on the new traffic parameter values.
1774 B.3 Establishing CR-LSP Supporting Delay Insensitive Applications
1776 In this example we assume that a throughput sensitive (TS) service
1777 is requested. For resource allocation the user assigns values for
1778 PDR, PBS, CDR, and CBS. The negotiation flag is set if the traffic
1779 parameters are subject to negotiation.
1780 Since the service is delay insensitive by definition, the
1781 Unspecified frequency is signaled to indicate that the service
1782 frequency is not an issue.
1784 Similar to the previous example, the edge actions are not subject
1785 for signaling and are specified in the service level agreement
1786 between the user and the network provider.
1788 For TS service, the edge rules might include marking to indicate
1789 high discard precedence values for all packets that exceed CDR and
1790 the CBS. The edge rules will also include dropping of packets that
1791 conform to neither PDR nor PBS.
1793 Each LSR of the LSP is expected to run its admission control rules
1794 and negotiate traffic parameters down if sufficient resources do not
1795 exist. The new parameter values are echoed back in the Label Mapping
1796 Message. LSRs might need to re-adjust their resources based on the
1797 new traffic parameter values.
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