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1 MPLS Working Group Bilel Jamoussi, Editor
2 Internet Draft Nortel Networks Corp.
3 Expiration Date: March 2000
4 September 1999
6 Constraint-Based LSP Setup using LDP
8 draft-ietf-mpls-cr-ldp-03.txt
10 Status of this Memo
12 This document is an Internet-Draft and is in full conformance with
13 all provisions of Section 10 of RFC2026.
15 Internet-Drafts are working documents of the Internet Engineering
16 Task Force (IETF), its areas, and its working groups. Note that
17 other groups may also distribute working documents as Internet-
18 Drafts.
20 Internet-Drafts are draft documents valid for a maximum of six
21 months and may be updated, replaced, or obsoleted by other documents
22 at any time. It is inappropriate to use Internet-Drafts as reference
23 material or to cite them other than as _work in progress._
25 The list of current Internet-Drafts can be accessed at
26 http://www.ietf.org/ietf/1id-abstracts.txt
28 The list of Internet-Draft Shadow Directories can be accessed at
29 http://www.ietf.org/shadow.html.
31 Abstract
33 Label Distribution Protocol (LDP) is defined in [1] for distribution
34 of labels inside one MPLS domain. One of the most important
35 services that may be offered using MPLS in general and LDP in
36 particular is support for constraint-based routing of traffic across
37 the routed network. Constraint-based routing offers the opportunity
38 to extend the information used to setup paths beyond what is
39 available for the routing protocol. For instance, an LSP can be
40 setup based on explicit route constraints, QoS constraints, and
41 other constraints. Constraint-based routing (CR) is a mechanism used
42 to meet Traffic Engineering requirements that have been proposed by
43 [2], [3] and [4]. These requirements may be met by extending LDP for
44 support of constraint-based routed label switched paths (CR-LSPs).
45 Other uses for CR-LSPs include MPLS-based VPNs.
47 This draft specifies mechanisms and TLVs for support of CR-LSPs
48 using LDP.
50 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 1 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
52 Table of Contents
54 1. Introduction....................................................3
55 2. Constraint-based Routing Overview...............................3
56 2.1 Strict and Loose Explicit Routes...............................4
57 2.2 Traffic Characteristics........................................4
58 2.3 Pre-emption....................................................5
59 2.4 Route Pinning..................................................5
60 2.5 Resource Class.................................................5
61 3. Solution Overview...............................................6
62 3.1 Required Messages and TLVs.....................................7
63 3.2 Label Request Message..........................................7
64 3.3 Label Mapping Message..........................................8
65 3.4 Notification Message...........................................8
66 3.5 Release , Withdraw, and Abort Messages.........................9
67 4. Protocol Specification..........................................9
68 4.1 Explicit Route TLV (ER-TLV)...................................10
69 4.2 Explicit Route Hop TLV (ER-Hop TLV)...........................10
70 4.3 Traffic Parameters TLV........................................11
71 4.3.1 Semantics...................................................13
72 4.3.1.1 Frequency.................................................13
73 4.3.1.2 Peak Rate.................................................13
74 4.3.1.3 Committed Rate............................................14
75 4.3.1.4 Excess Burst Size.........................................14
76 4.3.1.5 Peak Rate Token Bucket....................................14
77 4.3.1.6 Committed Data Rate Token Bucket..........................14
78 4.3.1.7 Weight....................................................15
79 4.3.2 Procedures..................................................15
80 4.3.2.1 Label Request Message.....................................15
81 4.3.2.2 Label Mapping Message.....................................16
82 4.3.2.3 Notification Message......................................16
83 4.4 Preemption TLV................................................16
84 4.5 LSPID TLV.....................................................17
85 4.6 Resource Class (Color) TLV....................................18
86 4.7 ER-Hop semantics..............................................19
87 4.7.1. ER-Hop 1: The IPv4 prefix..................................19
88 4.7.2. ER-Hop 2: The IPv6 address.................................20
89 4.7.3. ER-Hop 3: The autonomous system number....................20
90 4.7.4. ER-Hop 4: LSPID............................................21
91 4.8. Processing of the Explicit Route TLV.........................22
92 4.8.1. Selection of the next hop..................................22
93 4.8.2. Adding ER-Hops to the explicit route TLV...................23
94 4.9 Route Pinning TLV.............................................24
95 4.10 CR-LSP FEC Element...........................................24
96 4.11 Error subcodes...............................................25
97 5. Security.......................................................25
98 6. Acknowledgments................................................25
99 7. Intellectual Property Consideration............................26
100 8. References.....................................................26
101 9. Author's Addresses.............................................26
102 Appendix A: CR-LSP Establishment Examples.........................29
104 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 2 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
106 A.1 Strict Explicit Route Example.................................29
107 A.2 Node Groups and Specific Nodes Example........................30
108 Appendix B. QoS Service Examples..................................33
109 B.1 Service Examples..............................................33
110 B.2 Establishing CR-LSP Supporting Real-Time Applications.........34
111 B.3 Establishing CR-LSP Supporting Delay Insensitive Applications.35
112 Appendix C. LSP Modification Using CR-LDP.........................36
113 C.1 Introduction..................................................36
114 C.2 Basic Procedure...............................................37
115 C.3 Priority Handling.............................................38
116 C.4 Modification Failure Case Handling............................39
118 1. Introduction
120 The need for constraint-based routing (CR) in MPLS has been explored
121 elsewhere [3], [2], and [4]. Explicit routing is a subset of the
122 more general constraint-based routing function. At the MPLS WG
123 meeting held during the Washington IETF (December 1997) there was
124 consensus that LDP should support explicit routing of LSPs with
125 provision for indication of associated (forwarding) priority. In
126 the Chicago meeting (August 1998), a decision was made that support
127 for explicit path setup in LDP will be moved to a separate document.
128 This document provides that support and it has been accepted as a
129 working document in the Orlando meeting (December 1998).
131 This specification proposes an end-to-end setup mechanism of a
132 constraint-based routed LSP (CR-LSP) initiated by the ingress LSR.
133 We also specify mechanisms to provide means for reservation of
134 resources using LDP.
136 This document introduce TLVs and procedures that provide support
137 for:
138 - Strict and Loose Explicit Routing
139 - Specification of Traffic Parameters
140 - Route Pinning
141 - CR-LSP Pre-emption though setup/holding priorities
142 - Handling Failures
143 - LSPID
144 - Resource Class
146 Section 2 introduces the various constraints defined in this
147 specification. Section 3 outlines the CR-LDP solution. Section 4
148 defines the TLVs and procedures used to setup constraint-based
149 routed label switched paths. Appendix A provides several examples
150 of CR-LSP path setup. Appendix B provides Service Definition
151 Examples.
153 2. Constraint-based Routing Overview
155 Constraint-based routing is a mechanism that supports the Traffic
156 Engineering requirements defined in [4]. Explicit Routing is a
157 subset of the more general constraint-based routing where the
159 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 3 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
161 constraint is the explicit route (ER). Other constraints are defined
162 to provide a network operator with control over the path taken by an
163 LSP. This section is an overview of the various constraints
164 supported by this specification.
166 2.1 Strict and Loose Explicit Routes
168 Like any other LSP a CR-LSP is a path through an MPLS network. The
169 difference is that while other paths are setup solely based on
170 information in routing tables or from a management system, the
171 constraint-based route is calculated at one point at the edge of
172 network based on criteria, including but not limited to routing
173 information. The intention is that this functionality shall give
174 desired special characteristics to the LSP in order to better
175 support the traffic sent over the LSP. The reason for setting up CR-
176 LSPs might be that one wants to assign certain bandwidth or other
177 Service Class characteristics to the LSP, or that one wants to make
178 sure that alternative routes use physically separate paths through
179 the network.
181 An explicit route is represented in a Label Request Message as a
182 list of nodes or groups of nodes along the constraint-based route.
183 When the CR-LSP is established, all or a subset of the nodes in a
184 group may be traversed by the LSP. Certain operations to be
185 performed along the path can also be encoded in the constraint-based
186 route.
188 The capability to specify, in addition to specified nodes, groups of
189 nodes, of which a subset will be traversed by the CR-LSP, allows the
190 system a significant amount of local flexibility in fulfilling a
191 request for a constraint-based route. This allows the generator of
192 the constraint-based route to have some degree of imperfect
193 information about the details of the path.
195 The constraint-based route is encoded as a series of ER-Hops
196 contained in a constraint-based route TLV. Each ER-Hop may identify
197 a group of nodes in the constraint-based route. A constraint-based
198 route is then a path including all of the identified groups of nodes
199 in the order in which they appear in the TLV.
201 To simplify the discussion, we call each group of nodes an abstract
202 node. Thus, we can also say that a constraint-based route is a path
203 including all of the abstract nodes, with the specified operations
204 occurring along that path.
206 2.2 Traffic Characteristics
208 The traffic characteristics of a path are described in the Traffic
209 Parameters TLV in terms of a peak rate, committed rate, and service
210 granularity. The peak and committed rates describe the bandwidth
211 constraints of a path while the service granularity can be used to
213 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 4 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
215 specify a constraint on the delay variation that the CR-LDP MPLS
216 domain may introduce to a path's traffic.
218 2.3 Pre-emption
220 CR-LDP signals the resources required by a path on each hop of the
221 route. If a route with sufficient resources can not be found,
222 existing paths may be rerouted to reallocate resources to the new
223 path. This is the process of path pre-emption. Setup and holding
224 priorities are used to rank existing paths (holding priority) and
225 the new path (setup priority) to determine if the new path can pre-
226 empt an existing path.
228 The setupPriority of a new CR-LSP and the holdingPriority attributes
229 of the existing CR-LSP are used to specify priorities. Signaling a
230 higher holding priority express that the path, once it has been
231 established, should have a lower chance of being pre-empted.
232 Signaling a higher setup priority expresses the expectation that, in
233 the case that resource are unavailable, the path is more likely to
234 pre-empt other paths. The exact rules determining bumping are an
235 aspect of network policy.
237 The allocation of setup and holding priority values to paths is an
238 aspect of network policy.
240 The setup and holding priority values range from zero (0) to seven
241 (7). The value zero (0) is the priority assigned to the most
242 important path. It is referred to as the highest priority. Seven (7)
243 is the priority for the least important path. The use of default
244 priority values is an aspect of network policy.
246 The setupPriority of a CR-LSP should not be higher (numerically
247 less) than its holdingPriority since it might bump an LSP and be
248 bumped by the next _equivalent_ request.
250 2.4 Route Pinning
252 Route pinning is applicable to segments of an LSP that are loosely
253 routed - i.e. those segments which are specified with a next hop
254 with the `L' bit set or where the next hop is an _abstract node_. A
255 CR-LSP may be setup using route pinning if it is undesirable to
256 change the path used by an LSP even when a better next hop becomes
257 available at some LSR along the loosely routed portion of the LSP.
259 2.5 Resource Class
261 The network operator may classify network resources in various ways.
262 These classes are also known as _colors_ or _administrative groups_.
263 When a CR-LSP is being established, it's necessary to indicate which
264 resource classes the CR-LSP can draw from.
266 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 5 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
268 3. Solution Overview
270 CR-LSP over LDP Specification is designed with the following goals:
272 1. Meet the requirements outlined in [4] for performing traffic
273 engineering and provide a solid foundation for performing
274 more general constraint-based routing.
276 2. Build on already specified functionality that meets the
277 requirements whenever possible. Hence, this specification is
278 based on [1].
280 3. Keep the solution simple.
282 In this document, support for unidirectional point-to-point CR-LSPs
283 is specified. Support for point-to-multipoint, multipoint-to-point,
284 is for further study (FFS).
286 Support for constraint-based routed LSPs in this specification
287 depends on the following minimal LDP behaviors as specified in [1]:
289 - Use of Basic and/or Extended Discovery Mechanisms.
290 - Use of the Label Request Message defined in [1] in downstream
291 on demand label advertisement mode with ordered control.
292 - Use of the Label Mapping Message defined in [1] in downstream
293 on demand mode with ordered control.
294 - Use of the Notification Message defined in [1].
295 - Use of the Withdraw and Release Messages defined in [1].
296 - Use of the Loop Detection (in the case of loosely routed
297 segments of a CR-LSP) mechanisms defined in [1].
299 In addition, the following functionality is added to what's defined
300 in [1]:
302 - The Label Request Message used to setup a CR-LSP includes one
303 or more CR-TLVs defined in Section 4. For instance, the Label
304 Request Message may include the ER-TLV.
305 - An LSR implicitly infers ordered control from the existence of
306 one or more CR-TLVs in the Label Request Message. This means
307 that the LSR can still be configured for independent control
308 for LSPs established as a result of dynamic routing. However,
309 when a Label Request Message includes one or more of the CR-
310 TLVs, then ordered control is used to setup the CR-LSP. Note
311 that this is also true for the loosely routed parts of a CR-
312 LSP.
313 - New status codes are defined to handle error notification for
314 failure of established paths specified in the CR-TLVs.
316 Optional TLVs are not required in the CR-LDP messages for the
317 messages to be compliant with the protocol. Optional parameters MAY
318 be required for a particular operation to work (or work correctly),
319 however.
321 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 6 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
323 Examples of CR-LSP establishment are given in Appendix A to
324 illustrate how the mechanisms described in this draft work.
326 3.1 Required Messages and TLVs
328 Any Messages, TLVs, and procedures not defined explicitly in this
329 document are defined in the LDP Specification [1]. The state
330 transitions, which relate to CR-LDP messages, can be found in [5].
331 The following subsections are meant as a cross-reference to the [1]
332 document and indication of additional functionality beyond what's
333 defined in [1] where necessary.
335 3.2 Label Request Message
337 The Label Request Message is as defined in 3.5.8 of [1] with the
338 following modifications (required only if any of the CR-TLVs is
339 included in the Label Request Message):
341 - Only a single FEC-TLV may be included in the Label Request
342 Message. The CR-LSP FEC TLV should be used.
344 - The Optional Parameters TLV includes the definition of any of
345 the Constraint-based TLVs specified in Section 4.
347 - The Procedures to handle the Label Request Message are
348 augmented by the procedures for processing of the CR-TLVs as
349 defined in Section 4.
351 The encoding for the CR-LDP Label Request Message is as follows:
353 0 1 2 3
354 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
355 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
356 |0| Label Request (0x0401) | Message Length |
357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
358 | Message ID |
359 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
360 | FEC TLV |
361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
362 | LSPID TLV (CR-LDP, mandatory) |
363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
364 | ER-TLV (CR-LDP, optional) |
365 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
366 | Traffic TLV (CR-LDP, optional) |
367 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
368 | Pinning TLV (CR-LDP, optional) |
369 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
370 | Resource Class TLV (CR-LDP, optional) |
371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
372 | Pre-emption TLV (CR-LDP, optional) |
373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
375 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 7 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
377 3.3 Label Mapping Message
379 The Label Mapping Message is as defined in 3.5.7 of [1] with the
380 following modifications:
382 - Only a single Label-TLV may be included in the Label Mapping
383 Message.
385 - The Label Mapping Message Procedures are limited to downstream
386 on demand ordered control mode.
388 A Mapping message is transmitted by a downstream LSR to an upstream
389 LSR under one of the following conditions:
391 1. The LSR is the egress end of the CR-LSP and an upstream
392 mapping has been requested.
394 2. The LSR received a mapping from its downstream next hop LSR
395 for an CR-LSP for which an upstream request is still
396 pending.
398 The encoding for the CR-LDP Label Mapping Message is as follows:
400 0 1 2 3
401 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
402 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
403 |0| Label Mapping (0x0400) | Message Length |
404 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
405 | Message ID |
406 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
407 | FEC TLV |
408 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
409 | Label TLV |
410 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
411 | Label Request Message ID TLV |
412 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
413 | LSPID TLV (CR-LDP, optional) |
414 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
415 | Traffic TLV (CR-LDP, optional) |
416 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
418 3.4 Notification Message
420 The Notification Message is as defined in Section 3.5.1 of [1] and
421 the Status TLV encoding is as defined in Section 3.4.6 of [1].
422 Establishment of an CR-LSP may fail for a variety of reasons. All
423 such failures are considered advisory conditions and they are
424 signaled by the Notification Message.
426 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 8 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
428 Notification Messages carry Status TLVs to specify events being
429 signaled. New status codes are defined in Section 4.11 to signal
430 error notifications associated with the establishment of a CR-LSP
431 and the processing of the CR-TLV.
433 The Notification Message may carry the LSPID TLV of the
434 corresponding CR-LSP.
436 Notification Messages MUST be forwarded toward the LSR originating
437 the Label Request at each hop and at any time that procedures in
438 this specification - or in [1] - specify sending of a Notification
439 Message in response to a Label Request Message.
441 The encoding of the notification message is as follows:
443 0 1 2 3
444 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
445 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
446 |0| Notification (0x0001) | Message Length |
447 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
448 | Message ID |
449 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
450 | Status (TLV) |
451 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
452 | Optional Parameters |
453 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
455 3.5 Release , Withdraw, and Abort Messages
457 The Label Release , Label Withdraw, and Label Abort Request Messages
458 are used as specified in [1]. These messages may also carry the
459 LSPID TLV.
461 4. Protocol Specification
463 The Label Request Message defined in [1] optionally carries one or
464 more of the optional Constraint-based Routing TLVs (CR-TLVs) defined
465 in this section. If needed, other constraints can be supported later
466 through the definition of new TLVs. In this specification, the
467 following TLVs are defined:
469 - Explicit Route TLV
470 - Explicit Route Hop TLV
471 - Traffic Parameters TLV
472 - Preemption TLV
473 - LSPID TLV
474 - Route Pinning TLV
475 - Resource Class TLV
476 - CR-LSP FEC TLV
478 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 9 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
480 4.1 Explicit Route TLV (ER-TLV)
482 The ER-TLV is an object that specifies the path to be taken by the
483 LSP being established. It is composed of one or more Explicit Route
484 Hop TLVs (ER-Hop TLVs) defined in Section 4.2.
486 0 1 2 3
487 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
488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
489 |0|0| ER-TLV (0x0800) | Length |
490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
491 | ER-Hop TLV 1 |
492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
493 | ER-Hop TLV 2 |
494 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
495 ~ ............ ~
496 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
497 | ER-Hop TLV n |
498 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
500 Type
501 A two-byte field carrying the value of the ER-TLV type whichis
502 0x800.
504 Length
505 Specifies the length of the value field in bytes.
507 ER-Hop TLVs
508 One or more ER-Hop TLVs defined in Section 4.2.
510 4.2 Explicit Route Hop TLV (ER-Hop TLV)
512 The contents of an ER-TLV are a series of variable length ER-Hop
513 TLVs.
515 A node receiving a label request message including an ER-Hop type
516 that is not supported should not progress the label request message
517 to the downstream LSR and should send back a _No Route_ Notification
518 Message.
520 Each ER-Hop TLV has the form:
522 0 1 2 3
523 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
524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
525 |0|0| ER-Hop-Type | Length |
526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
527 |L| Content // |
528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
530 ER-Hop Type
532 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 10 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
534 A fourteen-bit field indicating the type of contents of the ER-
535 Hop. Currently defined values are:
537 Value Type
538 ----- ------------------------
539 0x801 IPv4 prefix
540 0x802 IPv6 prefix
541 0x803 Autonomous system number
542 0x804 LSPID
544 Length
545 Specifies the length of the value field in bytes.
547 L bit
548 The L bit in the ER-Hop is a one-bit attribute. If the L bit
549 is set, then the value of the attribute is _loose._ Otherwise,
550 the value of the attribute is _strict._ For brevity, we say
551 that if the value of the ER-Hop attribute is loose then it is a
552 _loose ER-Hop._ Otherwise, it's a _strict ER-Hop._ Further,
553 we say that the abstract node of a strict or loose ER-Hop is a
554 strict or a loose node, respectively. Loose and strict nodes
555 are always interpreted relative to their prior abstract nodes.
556 The path between a strict node and its prior node MUST include
557 only network nodes from the strict node and its prior abstract
558 node.
560 The path between a loose node and its prior node MAY include
561 other network nodes, which are not part of the strict node or
562 its prior abstract node.
564 Contents
565 A variable length field containing a node or abstract node
566 which is one of the consecutive nodes that make up the
567 explicitly routed LSP.
569 4.3 Traffic Parameters TLV
571 The following sections describe the CR-LSP Traffic Parameters. The
572 required characteristics of a CR-LSP are expressed by the Traffic
573 Parameter values.
575 A Traffic Parameters TLV, is used to signal the Traffic Parameter
576 values. The Traffic Parameters are defined in the subsequent
577 sections.
579 The Traffic Parameters TLV contains a Flags field, a Frequency, a
580 Weight, and the five Traffic Parameters PDR, PBS, CDR, CBS, EBS.
581 The Traffic Parameters TLV is shown below:
583 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 11 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
585 0 1 2 3
586 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
587 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
588 |0|0| Traf. Param. TLV (0x0810)| Length |
589 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
590 | Flags | Frequency | Reserved | Weight |
591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
592 | Peak Data Rate (PDR) |
593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
594 | Peak Burst Size (PBS) |
595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
596 | Committed Data Rate (CDR) |
597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
598 | Committed Burst Size (CBS) |
599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
600 | Excess Burst Size (EBS) |
601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
603 Type
604 A fourteen-bit field carrying the value of the ER-TLV type
605 which is 0x810.
607 Length
608 Specifies the length of the value field in bytes.
610 Flags
611 The Flags field is shown below:
613 +--+--+--+--+--+--+--+--+
614 | Res |F6|F5|F4|F3|F2|F1|
615 +--+--+--+--+--+--+--+--+
617 Res - These bits are reserved.
618 Zero on transmission.
619 Ignored on receipt.
620 F1 - Corresponds to the PDR.
621 F2 - Corresponds to the PBS.
622 F3 - Corresponds to the CDR.
623 F4 - Corresponds to the CBS.
624 F5 - Corresponds to the EBS.
625 F6 - Corresponds to the Weight.
627 Each flag Fi is a Negotiable Flag corresponding to a Traffic
628 Parameter. The Negotiable Flag value zero denotes NotNegotiable
629 and value one denotes Negotiable.
631 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 12 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
633 Frequency
634 The Frequency field is coded as an 8 bit unsigned integer with
635 the following code points defined:
637 0- Unspecified
638 1- Frequent
639 2- VeryFrequent
640 3-255 - Reserved
641 Reserved - Zero on transmission. Ignored on receipt.
643 Weight
644 An 8 bit unsigned integer indicating the weight of the CR-LSP.
645 Valid weight values are from 1 to 255. The value 0 means that
646 weight is not applicable for the CR-LSP.
648 Traffic Parameters
649 Each Traffic Parameter is encoded as a 32-bit IEEE single-
650 precision floating-point number. A value of positive infinity
651 is represented as an IEEE single-precision floating-point
652 number with an exponent of all ones (255) and a sign and
653 mantissa of all zeros. The values PDR and CDR are in units of
654 bytes per second. The values PBS, CBS and EBS are in units of
655 bytes.
657 The value of PDR MUST be greater than or equal to the value of
658 CDR in a correctly encoded Traffic Parameters TLV.
660 4.3.1 Semantics
662 4.3.1.1 Frequency
664 The Frequency specifies at what granularity the CDR allocated to the
665 CR-LSP is made available. The value VeryFrequent means that the
666 available rate should average at least the CDR when measured over
667 any time interval equal to or longer than the shortest packet time
668 at the CDR. The value Frequent means that the available rate should
669 average at least the CDR when measured over any time interval equal
670 to or longer than a small number of shortest packet times at the
671 CDR.
673 The value Unspecified means that the CDR MAY be provided at any
674 granularity.
676 4.3.1.2 Peak Rate
678 The Peak Rate defines the maximum rate at which traffic SHOULD be
679 sent to the CR-LSP. The Peak Rate is useful for the purpose of
680 resource allocation. If resource allocation within the MPLS domain
681 depends on the Peak Rate value then it should be enforced at the
682 ingress to the MPLS domain.
684 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 13 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
686 The Peak Rate is defined in terms of the two Traffic Parameters PDR
687 and PBS, see section 4.3.1.5 below.
689 4.3.1.3 Committed Rate
691 The Committed Rate defines the rate that the MPLS domain commits to
692 be available to the CR-LSP.
694 The Committed Rate is defined in terms of the two Traffic Parameters
695 CDR and CBS, see section 4.3.1.6 below.
697 4.3.1.4 Excess Burst Size
699 The Excess Burst Size may be used at the edge of an MPLS domain for
700 the purpose of traffic conditioning. The EBS MAY be used to measure
701 the extent by which the traffic sent on a CR-LSP exceeds the
702 committed rate.
704 The possible traffic conditioning actions, such as passing, marking
705 or dropping, are specific to the MPLS domain.
707 The Excess Burst Size is defined together with the Committed Rate,
708 see section 4.3.1.6 below.
710 4.3.1.5 Peak Rate Token Bucket
712 The Peak Rate of a CR-LSP is specified in terms of a token bucket P
713 with token rate PDR and maximum token bucket size PBS.
715 The token bucket P is initially (at time 0) full, i.e., the token
716 count Tp(0) = PBS. Thereafter, the token count Tp, if less than
717 PBS, is incremented by one PDR times per second. When a packet of
718 size B bytes arrives at time t, the following happens:
720 - If Tp(t)-B >= 0, the packet is not in excess of the peak rate
721 and Tp is decremented by B down to the minimum value of 0, else
723 - the packet is in excess of the peak rate and Tp is not
724 decremented.
726 Note that according to the above definition, a positive infinite
727 value of either PDR or PBS implies that arriving packets are never
728 in excess of the peak rate.
730 The actual implementation of an LSR doesn't need to be modeled
731 according to the above formal token bucket specification.
733 4.3.1.6 Committed Data Rate Token Bucket
735 The committed rate of a CR-LSP is specified in terms of a token
736 bucket C with rate CDR. The extent by which the offered rate
737 exceeds the committed rate MAY be measured in terms of another token
739 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 14 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
741 bucket E, which also operates at rate CDR. The maximum size of the
742 token bucket C is CBS and the maximum size of the token bucket E is
743 EBS.
745 The token buckets C and E are initially (at time 0) full, i.e., the
746 token count Tc(0) = CBS and the token count Te(0) = EBS.
747 Thereafter, the token counts Tc and Te are updated CDR times per
748 second as follows:
750 - If Tc is less than CBS, Tc is incremented by one, else
751 - if Te is less then EBS, Te is incremented by one, else
752 - neither Tc nor Te is incremented.
754 When a packet of size B bytes arrives at time t, the following
755 happens:
757 - If Tc(t)-B >= 0, the packet is not in excess of the Committed
758 Rate and Tc is decremented by B down to the minimum value of 0,
759 else
760 - if Te(t)-B >= 0, the packet is in excess of the Committed rate
761 but is not in excess of the EBS and Te is decremented by B down
762 to the minimum value of 0, else
763 - the packet is in excess of both the Committed Rate and the EBS
764 and neither Tc nor Te is decremented.
766 Note that according to the above specification, a CDR value of
767 positive infinity implies that arriving packets are never in excess
768 of either the Committed Rate or EBS. A positive infinite value of
769 either CBS or EBS implies that the respective limit cannot be
770 exceeded.
772 The actual implementation of an LSR doesn't need to be modeled
773 according to the above formal specification.
775 4.3.1.7 Weight
777 The weight determines the CR-LSP's relative share of the possible
778 excess bandwidth above its committed rate. The definition of
779 _relative share_ is MPLS domain specific.
781 4.3.2 Procedures
783 4.3.2.1 Label Request Message
785 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
786 which the value of PDR is less than the value of CDR then it MUST
787 send a Notification Message including the Status code _Traffic
788 Parameters Unavailable_ to the upstream LSR from which it received
789 the erroneous message.
791 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 15 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
793 If a Traffic Parameter is indicated as Negotiable in the Label
794 Request Message by the corresponding Negotiable Flag then an LSR MAY
795 replace the Traffic Parameter value with a smaller value.
797 If the Weight is indicated as Negotiable in the Label Request
798 Message by the corresponding Negotiable Flag then an LSR may replace
799 the Weight value with a lower value (down to 0).
801 If, after possible Traffic Parameter negotiation, an LSR can support
802 the CR-LSP Traffic Parameters then the LSR MUST reserve the
803 corresponding resources for the CR-LSP.
805 If, after possible Traffic Parameter negotiation, an LSR cannot
806 support the CR-LSP Traffic Parameters then the LSR MUST send a
807 Notification Message that contains the _Resource Unavailable_ status
808 code.
810 4.3.2.2 Label Mapping Message
812 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
813 which the value of PDR is less than the value of CDR then it MUST
814 send a Label Release message containing the Status code _Traffic
815 Parameters Unavailable_ to the LSR from which it received the
816 erroneous message. In addition, the LSP should send a Notification
817 Message upstream with the status code _Label Request Aborted_.
819 If the negotiation flag was set in the label request message, the
820 egress LSR MUST include the (possibly negotiated) Traffic Parameters
821 and Weight in the Label Mapping message.
823 The Traffic Parameters and the Weight in a Label Mapping message
824 MUST be forwarded unchanged.
826 An LSR SHOULD adjust the resources that it reserved for a CR-LSP
827 when it receives a Label Mapping Message if the Traffic Parameters
828 differ from those in the corresponding Label Request Message.
830 4.3.2.3 Notification Message
832 If an LSR receives a Notification Message for a CR-LSP, it SHOULD
833 release any resources that it possibly had reserved for the CR-LSP.
834 In addition, on receiving a Notification Message from a Downstream
835 LSR that is associated with a Label Request from an upstream LSR,
836 the local LSR MUST propagate the Notification message using the
837 procedures in [1].
839 4.4 Preemption TLV
841 The defualt value of the setup and holding priorities should be in
842 the middle of the range (e.g., 4) so that this feature can be turned
843 on gradually in an operational network by increasing or decerasing
844 the priority starting at the middle of the range.
846 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 16 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
848 0 1 2 3
849 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
850 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
851 |0|0| Preemption-TLV (0x0820) | Length |
852 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
853 | SetPrio | HoldPrio | Reserved |
854 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
856 Type
857 A fourteen-bit field carrying the value of the Preemption-TLV
858 type which is 0x820.
860 Length
861 Specifies the length of the value field in bytes.
863 Reserved
864 Zero on transmission. Ignored on receipt.
866 SetPrio
867 A SetupPriority of value zero (0) is the priority assigned to
868 the most important path. It is referred to as the highest
869 priority. Seven (7) is the priority for the least important
870 path. The higher the setup priority, the more paths CR-LDP can
871 bump to set up the path. The default value should be 4.
873 HoldPrio
874 A HoldingPriority of value zero (0) is the priority assigned to
875 the most important path. It is referred to as the highest
876 priority. Seven (7) is the priority for the least important
877 path. The default value should be 4.
878 The higher the holding priority, the less likely it is for CR-
879 LDP to reallocate its bandwidth to a new path.
881 4.5 LSPID TLV
883 LSPID is a unique identifier of a CR-LSP within an MPLS network.
885 The LSPID is composed of the ingress LSR Router ID (or any of its
886 own Ipv4 addresses) and a Locally unique CR-LSP ID to that LSR.
888 The LSPID is useful in network management, in CR-LSP repair, and in
889 using an already established CR-LSP as a hop in an ER-TLV.
891 An _action indicator flag_ is carried in the LSPID TLV. This _action
892 indicator flag_ indicates explicitly the action that should be taken
893 if the LSP already exists on the LSR receiving the message.
895 After a CR-LSP is set up, its bandwidth reservation may need to be
896 changed by the network operator, due to the new requirements for the
897 traffic carried on that CR-LSP. The _action indicator flag_ is used
899 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 17 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
901 indicate the need to modify the bandwidth and possibly other
902 parameters of an established CR-LSP without service interruption.
903 This feature has application in dynamic network resources management
904 where traffic of different priorities and service classes is
905 involved.
907 The procedure for the code point _modify_ is defined in Appendix C.
908 The procedures for other flags are FFS.
910 0 1 2 3
911 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
912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
913 |0|0| LSPID-TLV (0x0821) | Length |
914 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
915 | Reserved |ActFlg | Local CR-LSP ID |
916 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
917 | Ingress LSR Router ID |
918 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
920 Type
921 A fourteen-bit field carrying the value of the LSPID-TLV type
922 which is 0x821.
924 Length
925 Specifies the length of the value field in bytes.
927 ActFlg
928 Action Indicator Flag: A 4-bit field that indicates explicitly
929 the action that should be taken if the LSP already exists on
930 the LSR receiving the message. A set of indicator code points
931 is proposed as follows:
933 0000: indicates initial LSP setup
934 0001: indicates modify LSP
935 Reserved
936 Zero on transmission. Ignored on receipt.
938 Local CR-LSP ID
939 The Local LSP ID is an identifier of the CR-LSP locally unique
940 within the Ingress LSR originating the CR-LSP.
942 Ingress LSR Router ID
943 An LSR may use any of its own IPv4 addresses in this field.
945 4.6 Resource Class (Color) TLV
947 The Resource Class as defined in [4] is used to specify which links
948 are acceptable by this CR-LSP. This information allows for the
949 network's topology to be pruned.
951 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 18 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
953 0 1 2 3
954 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
955 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
956 |0|0| ResCls-TLV (0x0822) | Length |
957 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
958 | RsCls |
959 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
961 Type
962 A fourteen-bit field carrying the value of the ResCls-TLV type
963 which is 0x822.
965 Length
966 Specifies the length of the value field in bytes.
968 RsCls
969 The Resource Class bit mask indicating which of the 32
970 _administrative groups_ or _colors_ of links the CR-LSP can
971 traverse.
973 4.7 ER-Hop semantics
975 4.7.1. ER-Hop 1: The IPv4 prefix
977 The abstract node represented by this ER-Hop is the set of nodes,
978 which have an IP address, which lies within this prefix. Note that
979 a prefix length of 32 indicates a single IPv4 node.
981 0 1 2 3
982 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
983 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
984 |0|0| 0x801 | Length |
985 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
986 |L| Reserved | PreLen |
987 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
988 | IPv4 Address (4 bytes) |
989 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
991 Type
992 IPv4 Address 0x801
994 Length
995 Specifies the length of the value field in bytes.
997 L Bit
998 Set to indicate Loose hop.
999 Cleared to indicate a strict hop.
1001 Reserved
1002 Zero on transmission. Ignored on receipt.
1004 PreLen
1006 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 19 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
1008 Prefix Length 1-32
1010 IP Address
1011 A four-byte field indicating the IP Address.
1013 4.7.2. ER-Hop 2: The IPv6 address
1015 0 1 2 3
1016 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
1017 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1018 |0|0| 0x802 | Length |
1019 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1020 |L| Reserved | PreLen |
1021 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1022 | IPV6 address |
1023 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1024 | IPV6 address (continued) |
1025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1026 | IPV6 address (continued) |
1027 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1028 | IPV6 address (continued) |
1029 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1031 Type
1032 0x802 IPv6 address
1034 Length
1035 Specifies the length of the value field in bytes.
1037 L Bit
1038 Set to indicate Loose hop.
1039 Cleared to indicate a strict hop.
1041 Reserved
1042 Zero on transmission. Ignored on receipt.
1044 PreLen
1045 Prefix Length 1-128
1047 IPv6 address
1048 A 128-bit unicast host address.
1050 4.7.3. ER-Hop 3: The autonomous system number
1052 The abstract node represented by this ER-Hop is the set of nodes
1053 belonging to the autonomous system.
1055 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 20 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
1057 0 1 2 3
1058 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
1059 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1060 |0|0| 0x803 | Length |
1061 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1062 |L| Reserved | AS Number |
1063 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1065 Type
1066 AS Number 0x803
1068 Length
1069 Specifies the length of the value field in bytes.
1071 L Bit
1072 Set to indicate Loose hop.
1073 Cleared to indicate a strict hop.
1075 Reserved
1076 Zero on transmission. Ignored on receipt.
1078 AS Number
1079 Autonomous System number
1081 4.7.4. ER-Hop 4: LSPID
1083 The LSPID is used to identify the tunnel ingress point as the next
1084 hop in the ER. This ER-Hop allows for stacking new CR-LSPs within an
1085 already established CR-LSP. It also allows for splicing the CR-LSP
1086 being established with an existing CR-LSP.
1088 If an LSPID Hop is the last ER-Hop in an ER-TLV, than the LSR may
1089 splice the CR-LSP of the incoming Label Request to the CR-LSP that
1090 currently exists with this LSPID. This is useful, for example, at
1091 the point at which a Label Request used for local repair arrives at
1092 the next ER-Hop after the loosely specified CR-LSP segment. Use of
1093 the LSPID Hop in this scenario eliminates the need for ER-Hops to
1094 keep the entire remaining ER-TLV at each LSR that is at either
1095 (upstream or downstream) end of a loosely specified CR-LSP segment
1096 as part of its state information. This is due to the fact that the
1097 upstream LSR needs only to keep the next ER-Hop and the LSPID and
1098 the downstream LSR needs only to keep the LSPID in order for each
1099 end to be able to recognize that the same LSP is being identified.
1101 If the LSPID Hop is not the last hop in an ER-TLV, the LSR must
1102 forward the remaining ER-TLV in a Label Request message, using the
1103 CR-LSP specified by the LSPID, to the LSR that is the CR-LSP's
1104 egress. That LSR will continue processing of the CR-LSP Label
1105 Request Message. The result is a tunneled, or stacked, CR-LSP.
1107 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 21 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
1109 0 1 2 3
1110 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
1111 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1112 |0|0| 0x804 | Length |
1113 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1114 |L| Reserved | Local LSPID |
1115 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1116 | Ingress LSR Router ID |
1117 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1119 Type
1120 LSPID 0x804
1122 Length
1123 Specifies the length of the value field in bytes.
1125 L Bit
1126 Set to indicate Loose hop.
1127 Cleared to indicate a strict hop.
1129 Reserved
1130 Zero on transmission. Ignored on receipt.
1132 Local LSPID
1133 A 2 byte field indicating the LSPID which is unique with
1134 reference to its Ingress LSR.
1136 Ingress LSR Router ID
1137 An LSR may use any of its own IPv4 addresses in this field.
1139 4.8. Processing of the Explicit Route TLV
1141 4.8.1. Selection of the next hop
1143 A Label Request Message containing an explicit route TLV must
1144 determine the next hop for this path. Selection of this next hop
1145 may involve a selection from a set of possible alternatives. The
1146 mechanism for making a selection from this set is implementation
1147 dependent and is outside of the scope of this specification.
1148 Selection of particular paths is also outside of the scope of this
1149 specification, but it is assumed that each node will make a best
1150 effort attempt to determine a loop-free path. Note that such best
1151 efforts may be overridden by local policy.
1153 To determine the next hop for the path, a node performs the
1154 following steps:
1156 1. The node receiving the Label Request Message must first
1157 evaluate the first ER-Hop. If the L bit is not set in the
1158 first ER-Hop and if the node is not part of the abstract node
1159 described by the first ER-Hop, it has received the message in
1161 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 22 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
1163 error, and should return a _Bad Initial ER-Hop_ error. If the
1164 L bit is set and the local node is not part of the abstract
1165 node described by the first ER-Hop, the node selects a next
1166 hop that is along the path to the abstract node described by
1167 the first ER-Hop. If there is no first ER-Hop, the message is
1168 also in error and the system should return a _Bad Explicit
1169 Routing TLV_ error using a Notification Message sent upstream.
1171 2. If there is no second ER-Hop, this indicates the end of the
1172 explicit route. The explicit route TLV should be removed from
1173 the Label Request Message. This node may or may not be the
1174 end of the LSP. Processing continues with section 4.8.2,
1175 where a new explicit route TLV may be added to the Label
1176 Request Message.
1178 3. If the node is also a part of the abstract node described by
1179 the second ER-Hop, then the node deletes the first ER-Hop and
1180 continues processing with step 2, above. Note that this makes
1181 the second ER-Hop into the first ER-Hop of the next iteration.
1183 4. The node determines if it is topologically adjacent to the
1184 abstract node described by the second ER-Hop. If so, the node
1185 selects a particular next hop which is a member of the
1186 abstract node. The node then deletes the first ER-Hop and
1187 continues processing with section 4.8.2.
1189 5. Next, the node selects a next hop within the abstract node of
1190 the first ER-Hop that is along the path to the abstract node
1191 of the second ER-Hop. If no such path exists then there are
1192 two cases:
1194 5.a If the second ER-Hop is a strict ER-Hop, then there is
1195 an error and the node should return a _Bad Strict Node_
1196 error.
1198 5.b Otherwise, if the second ER-Hop is a loose ER-Hop, then
1199 the node selects any next hop that is along the path to the
1200 next abstract node. If no path exists within the MPLS
1201 domain, then there is an error, and the node should return a
1202 _Bad loose node_ error.
1204 6. Finally, the node replaces the first ER-Hop with any ER-Hop
1205 that denotes an abstract node containing the next hop. This
1206 is necessary so that when the explicit route is received by
1207 the next hop, it will be accepted.
1209 7. Progress the Label Request Message to the next hop.
1211 4.8.2. Adding ER-Hops to the explicit route TLV
1213 After selecting a next hop, the node may alter the explicit route in
1214 the following ways.
1216 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 23 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
1218 If, as part of executing the algorithm in section 4.8.1, the
1219 explicit route TLV is removed, the node may add a new explicit route
1220 TLV.
1222 Otherwise, if the node is a member of the abstract node for the
1223 first ER-Hop, then a series of ER-Hops may be inserted before the
1224 first ER-Hop or may replace the first ER-Hop. Each ER-Hop in this
1225 series must denote an abstract node that is a subset of the current
1226 abstract node.
1228 Alternately, if the first ER-Hop is a loose ER-Hop, an arbitrary
1229 series of ER-Hops may be inserted prior to the first ER-Hop.
1231 4.9 Route Pinning TLV
1233 Section 2.4 describes the use of route pinning. The encoding of the
1234 Route Pinning TLV is as follows:
1236 0 1 2 3
1237 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
1238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1239 |0|0| 0x823 | Length |
1240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1241 |P| Reserved |
1242 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1244 Type
1245 Pinning-TLV type 0x823
1247 Length
1248 Specifies the length of the value field in bytes.
1250 P Bit
1251 The P bit is set to 1 to indicate that route pinning is
1252 requested.
1253 The P bit is set to 0 to indicate that route pinning is not
1254 requested
1256 Reserved
1257 Zero on transmission. Ignored on receipt.
1259 4.10 CR-LSP FEC Element
1261 A new FEC element is introduced in this specification to support CR-
1262 LSPs. This new FEC element does not preclude the use of other FECs
1263 elements (Type=0x01, 0x02, 0x03) defined in the LDP spec in CR-LDP
1264 messages. The CR-LDP FEC Element is an opaque FEC to be used only in
1265 Messages of CR-LSPs.
1267 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 24 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
1269 FEC Element Type Value
1270 Type name
1272 CR-LSP 0x04 No value; i.e., 0 value octets;
1274 The CR-LSP FEC TLV encoding is as follows:
1276 0 1 2 3
1277 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
1278 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1279 |0|0| FEC(0x0100) | Length |
1280 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1281 | CR-LSP (4) |
1282 +-+-+-+-+-+-+-+-+
1284 Type
1285 FEC TLV type 0x0100
1287 Length
1288 Specifies the length of the value field in bytes.
1290 CR-LSP FEC Element Type
1291 0x04
1293 4.11 Error subcodes
1295 In the processing described above, certain errors need to be
1296 reported as part of the Notification Message. This section defines
1297 the status codes for the errors described in this specification.
1299 Status Code Type
1300 -------------------------------------- ----------
1301 Bad Explicit Routing TLV Error 0x44000001
1302 Bad Strict Node Error 0x44000002
1303 Bad Loose Node Error 0x44000003
1304 Bad Initial ER-Hop Error 0x44000004
1305 Resource Unavailable 0x44000005
1306 Traffic Parameters Unavailable 0x44000006
1307 Setup Abort (Label Request Aborted in [1]) 0x04000015
1308 Modify Request Not Supported 0x44000008
1310 5. Security
1312 Pre-emption has to be controlled by the MPLS domain.
1314 Resource reservation requires the LSRs to have an LSP admission
1315 control function.
1317 Traffic Engineered LSPs can bypass normal routing.
1319 6. Acknowledgments
1321 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 25 Internet Draft Constraint-Based LSP Setup using LDP September, 1999
1323 The messages used to signal the CR-LSP setup are based on the work
1324 done by the [1] team.
1326 The authors would also like to acknowledge the careful review and
1327 comments of Ken Hayward, Greg Wright, Geetha Brown, Brian Williams,
1328 Paul Beaubien, Matthew Yuen, Liam Casey, Ankur Anand, Adrian Farrel.
1330 7. Intellectual Property Consideration
1332 The IETF has been notified of intellectual property rights claimed
1333 in regard to some or all of the specification contained in this
1334 document. For more information consult the online list of claimed
1335 rights.
1337 8. References
1339 1 Andersson et al, "Label Distribution Protocol Specification"
1340 work in progress (draft-ietf-mpls-ldp-05), June 1999.
1342 2 Callon et al, "Framework for Multiprotocol Label Switching",
1343 work in progress (draft-ietf-mpls-framework-05), September 1999.
1345 3 Rosen et al, "Multiprotocol Label Switching Architecture",
1346 work in progress (draft-ietf-mpls-arch-06), September 1999.
1348 4 Awduche et al, "Requirements for Traffic Engineering Over
1349 MPLS", RFC 2702, September 1999.
1351 5 L. Wu, et. al., "LDP State Machine" work in progress
1352 (draft-ietf-mpls-ldp-state-00), Feb 1999.
1354 9. Author's Addresses
1356 Osama S. Aboul-Magd Loa Andersson
1357 Nortel Networks Nortel Networks
1358 P O Box 3511 Station C S:t Eriksgatan 115
1359 Ottawa, ON K1Y 4H7 PO Box 6701
1360 Canada 113 85 Stockholm
1361 Phone: +1 613 763-5827 Tel: +46 8 508 835 00
1362 Osama@nortelnetworks.com Fax: +46 8 508 835 01
1363 Loa_andersson@nortelnetworks.com
1365 Peter Ashwood-Smith Ross Callon
1366 Nortel Networks IronBridge Networks
1367 P O Box 3511 Station C 55 Hayden Avenue,
1368 Ottawa, ON K1Y 4H7 Lexington, MA 02173
1369 Canada Phone: +1-781-402-8017
1370 Phone: +1 613 763-4534 Rcallon@ironbridgenetworks.com
1371 Petera@nortelnetworks.com
1373 Ram Dantu Paul Doolan
1374 Alcatel USA Inc. Ennovate Networks
1376 Jamoussi, et. al. draft-ietf-mpls-crldp-03.txt 26 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1378 IP Competence Center 330 Codman Hill Rd
1379 1201 E. Campbell Road.,446-315 Marlborough MA 01719
1380 Richadson, TX USA., 75081-2206 Phone: 978-263-2002
1381 Phone: 972 996 2938 Pdoolan@ennovatenetworks.com
1382 Fax: 972 996 5902
1383 Ram.dantu@alcatel.com
1385 Nancy Feldman Andre Fredette
1386 IBM Corp. Nortel Networks
1387 17 Skyline Drive 600 Technology Park Drive
1388 Hawthorne NY 10532 Billerica, MA 01821
1389 Phone: 914-784-3254 978-288-8524
1390 Nkf@us.ibm.com Fredette@nortelnetworks.com
1392 Eric Gray Joel M. Halpern
1393 Lucent Technologies, Inc Institutional Venture Partners
1394 1600 Osgood St. 650-926-5633
1395 North Andover, MA 01847 Joel@mcquillan.com
1396 Phone: 603-659-3386
1397 Ewgray@lucent.com
1399 Juha Heinanen Fiffi Hellstrand
1400 Telia Finland, Inc. Ericsson Telecom AB
1401 Myyrmaentie 2 S-126 25 STOCKHOLM
1402 01600 VANTAA Sweden
1403 Finland Tel: +46 8 719 4933
1404 Tel: +358 41 500 4808 Etxfiff@etxb.ericsson.se
1405 Jh@telia.fi
1407 Bilel Jamoussi Timothy E. Kilty
1408 Nortel Networks Corp. Northchurch Communications
1409 600 Technology Park Drive 5 Corporate Drive,
1410 Billerica, MA 01821 Andover, MA 018110
1411 USA phone: 978 691-4656
1412 Phone: +1 978 288-4506 Tkilty@northc.com
1413 Jamoussi@nortelnetworks.com
1415 Andrew G. Malis Muckai K Girish
1416 Ascend Communications, Inc. SBC Technology Resources,
1417 1 Robbins Road 4698 Willow Road
1418 Westford, MA 01886 Pleasanton, CA 94588
1419 Phone: 978 952-7414 Phone: (925) 598-1263
1420 fax: 978 392-2074 Fax: (925) 598-1321
1421 Malis@ascend.com Mgirish@tri.sbc.com
1423 Kenneth Sundell Pasi Vaananen
1424 Nortel Networks Nokia Telecommunications
1425 S:t Eriksgatan 115 3 Burlington Woods Drive,
1426 PO Box 6701 Burlington, MA 01803
1427 113 85 Stockholm Phone: +1-781-238-4981
1428 Tel: +46 8 508 835 00 Pasi.vaanenen@ntc.nokia.com
1429 Fax: +46 8 508 835 01
1431 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 27 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1433 Ksundell@nortelnetworks.com
1435 Tom Worster Liwen Wu
1436 Nokia Alcatel U.S.A
1437 3 Burlington Woods Dr. 44983 Knoll Square
1438 Suite 250 Ashburn, Va. 20147
1439 Burlington MA 01803 USA Phone: (703) 724-2619
1440 +1 617 247 2624 FAX: (703) 724-2005
1441 Tom.worster@nokia.com Liwen.wu@and.alcatel.com
1443 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 28 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1445 Appendix A: CR-LSP Establishment Examples
1447 A.1 Strict Explicit Route Example
1449 This appendix provides an example for the setup of a strictly routed
1450 CR-LSP. In this example, a specific node represents each abstract
1451 node.
1453 The sample network used here is a four node network with two edge
1454 LSRs and two core LSRs as follows:
1456 abc
1457 LSR1------LSR2------LSR3------LSR4
1459 LSR1 generates a Label Request Message as described in Section 3.1
1460 of this draft and sends it to LSR2. This message includes the CR-
1461 TLV.
1463 A vector of three ER-Hop TLVs composes the ER-TLV.
1464 The ER-Hop TLVs used in this example are of type 0x0801 (IPv4
1465 prefix) with a prefix length of 32. Hence, each ER-Hop TLV
1466 identifies a specific node as opposed to a group of nodes.
1467 At LSR2, the following processing of the ER-TLV per Section 4.8.1 of
1468 this draft takes place:
1470 1) The node LSR2 is part of the abstract node described by the
1471 first hop . Therefore, the first step passes the test.
1472 Go to step 2.
1474 2) There is a second ER-Hop, . Go to step 3.
1476 3) LSR2 is not part of the abstract node described by the
1477 second ER-Hop . Go to Step 4.
1479 4) LSR2 determines that it is topologically adjacent to the
1480 abstract node described by the second ER-Hop . LSR2
1481 selects a next hop (LSR3) which is the abstract node. LSR2
1482 deletes the first ER-Hop from the ER-TLV, which now
1483 becomes . Processing continues with Section 4.8.2.
1485 At LSR2, the following processing of Section 4.8.2 takes place:
1486 Executing algorithm 4.8.1 did not result in the removal of the ER-
1487 TLV.
1489 Also, LSR2 is not a member of the abstract node described by the
1490 first ER-Hop .
1492 Finally, the first ER-Hop is a strict hop.
1494 Therefore, processing section 4.8.2 does not result in the insertion
1495 of new ER-Hops. The selection of the next hop has been already done
1496 is step 4 of Section 4.8.1 and the processing of the ER-TLV is
1498 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 29 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1500 completed at LSR2. In this case, the Label Request Message including
1501 the ER-TLV is progressed by LSR2 to LSR3.
1503 At LSR3, a similar processing to the ER-TLV takes place except that
1504 the incoming ER-TLV = and the outgoing ER-TLV is .
1506 At LSR4, the following processing of section 4.8.1 takes place:
1508 1) The node LSR4 is part of the abstract node described by the
1509 first hop . Therefore, the first step passes the test. Go
1510 to step 2.
1511 2) There is no second ER-Hop, this indicates the end of the CR-
1512 LSP. The ER-TLV is removed from the Label Request Message.
1513 Processing continues with Section 4.8.2.
1515 At LSR4, the following processing of Section 4.8.2 takes place:
1516 Executing algorithm 4.8.1 resulted in the removal of the ER-TLV.
1517 LSR4 does not add a new ER-TLV.
1519 Therefore, processing section 4.8.2 does not result in the insertion
1520 of new ER-Hops. This indicates the end of the CR-LSP and the
1521 processing of the ER-TLV is completed at LSR4.
1523 At LSR4, processing of Section 3.2 is invoked. The first condition
1524 is satisfied (LSR4 is the egress end of the CR-LSP and upstream
1525 mapping has been requested). Therefore, a Label Mapping Message is
1526 generated by LSR4 and sent to LSR3.
1528 At LSR3, the processing of Section 3.2 is invoked. The second
1529 condition is satisfied (LSR3 received a mapping from its downstream
1530 next hop LSR4 for a CR-LSP for which an upstream request is still
1531 pending). Therefore, a Label Mapping Message is generated by LSR3
1532 and sent to LSR2.
1534 At LSR2, a similar processing to LSR 3 takes place and a Label
1535 Mapping Message is sent back to LSR1, which completes the end-to-end
1536 CR-LSP setup.
1538 A.2 Node Groups and Specific Nodes Example
1540 A request at ingress LSR to setup a CR-LSP might originate from a
1541 management system or an application, the details are implementation
1542 specific.
1544 The ingress LSR uses information provided by the management system
1545 or the application and possibly also information from the routing
1546 database to calculate the explicit route and to create the Label
1547 Request Message.
1549 The Label request message carries together with other necessary
1550 information an ER-TLV defining the explicitly routed path. In our
1551 example the list of hops in the ER-Hop TLV is supposed to contain an
1553 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 30 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1555 abstract node representing a group of nodes, an abstract node
1556 representing a specific node, another abstract node representing a
1557 group of nodes, and an abstract node representing a specific egress
1558 point.
1560 In--{Group 1}--{Specific A}--{Group 2}--{Specific Out: B}
1561 The ER-TLV contains four ER-Hop TLVs:
1563 1. An ER-Hop TLV that specifies a group of LSR valid for the
1564 first abstract node representing a group of nodes (Group 1).
1566 2. An ER-Hop TLV that indicates the specific node (Node A).
1568 3. An ER-Hop TLV that specifies a group of LSRs valid for the
1569 second abstract node representing a group of nodes (Group
1570 2).
1572 4. An ER-Hop TLV that indicates the specific egress point for
1573 the CR-LSP (Node B).
1575 All the ER-Hop TLVs are strictly routed nodes.
1576 The setup procedure for this CR-LSP works as follows:
1578 1. The ingress node sends the Label Request Message to a node
1579 that is a member the group of nodes indicated in the first
1580 ER-Hop TLV, following normal routing for the specific node
1581 (A).
1583 2. The node that receives the message identifies itself as part
1584 of the group indicated in the first ER-Hop TLV, and that it
1585 is not the specific node (A) in the second. Further it
1586 realizes that the specific node (A) is not one of its next
1587 hops.
1589 3. It keeps the ER-Hop TLVs intact and sends a Label Request
1590 Message to another node that is part of the group indicated
1591 in the first ER-Hop TLV (Group 1), following normal routing
1592 for the specific node (A).
1594 4. The node that receives the message identifies itself as part
1595 of the group indicated in the first ER-Hop TLV, and that it
1596 is not the specific node (A) in the second ER-Hop TLV.
1597 Further it realizes that the specific node (A) is one of its
1598 next hops.
1600 5. It removes the first ER-Hop TLVs and sends a Label Request
1601 Message to the specific node (A).
1603 6. The specific node (A) recognizes itself in the first ER-Hop
1604 TLV. Removes the specific ER-Hop TLV.
1606 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 31 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1608 7. It sends a Label Request Message to a node that is a member
1609 of the group (Group 2) indicated in the ER-Hop TLV.
1611 8. The node that receives the message identifies itself as part
1612 of the group indicated in the first ER-Hop TLV, further it
1613 realizes that the specific egress node (B) is one of its
1614 next hops.
1616 9. It sends a Label Request Message to the specific egress node
1617 (B).
1619 10.The specific egress node (B) recognizes itself as the egress
1621 for the CR-LSP, it returns a Label Mapping Message, that
1622 will traverse the same path as the Label Request Message in
1623 the opposite direction.
1625 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 32 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1627 Appendix B. QoS Service Examples
1629 B.1 Service Examples
1631 Construction of an end-to-end service is the result of the rules
1632 enforced at the edge and the treatment that packets receive at the
1633 network nodes. The rules define the traffic conditioning actions
1634 that are implemented at the edge and they include policing with
1635 pass, mark, and drop capabilities. The edge rules are expected tobe
1636 defined by the mutual agreements between the service providers and
1637 their customers and they will constitute an essential part of the
1638 SLA. Therefore edge rules are not included in the signaling
1639 protocol.
1641 Packet treatment at a network node is usually referred to as the
1642 local behavior. Local behavior could be specified in many ways. One
1643 example for local behavior specification is the service frequency
1644 introduced in section 4.3.2.1, together with the resource
1645 reservation rules implemented at the nodes.
1647 Edge rules and local behaviors can be viewed as the main building
1648 blocks for the end-to-end service construction. The following table
1649 illustrates the applicability of the building block approach for
1650 constructing different services including those defined for ATM.
1652 Service PDR PBS CDR CBS EBS Service Conditioning
1653 Examples Frequency Action
1655 DS S S =PDR =PBS 0 Frequent drop>PDR
1657 TS S S S S 0 Unspecified drop>PDR,PBS
1658 mark>CDR,CBS
1660 BE inf inf inf inf 0 Unspecified -
1662 FRS S S CIR ~B_C ~B_E Unspecified drop>PDR,PBS
1663 mark>CDR,CBS,EBS
1665 ATM-CBR PCR CDVT =PCR =CDVT 0 VeryFrequent drop>PCR
1667 ATM-VBR.3(rt) PCR CDVT SCR MBS 0 Frequent drop>PCR
1668 mark>SCR,MBS
1670 ATM-VBR.3(nrt) PCR CDVT SCR MBS 0 Unspecified drop>PCR
1671 mark>SCR,MBS
1673 ATM-UBR PCR CDVT - - 0 Unspecified drop>PCR
1675 ATM-GFR.1 PCR CDVT MCR MBS 0 Unspecified drop>PCR
1677 ATM-GFR.2 PCR CDVT MCR MBS 0 Unspecified drop>PCR
1678 mark>MCR,MFS
1680 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 33 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1682 int-serv-CL p m r b 0 Frequent drop>p
1683 drop>r,b
1685 S= User specified
1687 In the above table, the DS refers to a delay sensitive service where
1688 the network commits to deliver with high probability user datagrams
1689 at a rate of PDR with minimum delay and delay requirements.
1690 Datagrams in excess of PDR will be discarded.
1692 The TS refers to a generic throughput sensitive service where the
1693 network commits to deliver with high probability user datagrams at a
1694 rate of at least CDR. The user may transmit at a rate higher than
1695 CDR but datagrams in excess of CDR would have a lower probability of
1696 being delivered.
1698 The BE is the best effort service and it implies that there are no
1699 expected service guarantees from the network.
1701 B.2 Establishing CR-LSP Supporting Real-Time Applications
1703 In this scenario the customer needs to establish an LSP for
1704 supporting real-time applications such as voice and video. The
1705 Delay-sensitive (DS) service is requested in this case.
1707 The first step is the specification of the traffic parameters in the
1708 signaling message. The two parameters of interest to the DS service
1709 are the PDR and the PBS and the user based on his requirements
1710 specifies their values. Since all the traffic parameters are
1711 included in the signaling message, appropriate values must be
1712 assigned to all of them. For DS service, the CDR and the CBS values
1713 are set equal to the PDR and the PBS respectively. An indication of
1714 whether the parameter values are subject to negotiation is flagged.
1716 The transport characteristics of the DS service require Frequent
1717 frequency to be requested to reflect the real-time delay
1718 requirements of the service.
1720 In addition to the transport characteristics, both the network
1721 provider and the customer need to agree on the actions enforced at
1722 the edge. The specification of those actions is expected to be a
1723 part of the service level agreement (SLA) negotiation and is not
1724 included in the signaling protocol. For DS service, the edge action
1725 is to drop packets that exceed the PDR and the PBS specifications.
1726 The signaling message will be sent in the direction of the ER path
1727 and the LSP is established following the normal LDP procedures. Each
1728 LSR applies its admission control rules. If sufficient resources are
1729 not available and the parameter values are subject to negotiation,
1730 then the LSR could negotiate down the PDR, the PBS, or both.
1732 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 34 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1734 The new parameter values are echoed back in the Label Mapping
1735 Message. LSRs might need to re-adjust their resource reservations
1736 based on the new traffic parameter values.
1738 B.3 Establishing CR-LSP Supporting Delay Insensitive Applications
1740 In this example we assume that a throughput sensitive (TS) service
1741 is requested. For resource allocation the user assigns values for
1742 PDR, PBS, CDR, and CBS. The negotiation flag is set if the traffic
1743 parameters are subject to negotiation.
1744 Since the service is delay insensitive by definition, the
1745 Unspecified frequency is signaled to indicate that the service
1746 frequency is not an issue.
1748 Similar to the previous example, the edge actions are not subject
1749 for signaling and are specified in the service level agreement
1750 between the user and the network provider.
1752 For TS service, the edge rules might include marking to indicate
1753 high discard precedence values for all packets that exceed CDR and
1754 the CBS. The edge rules will also include dropping of packets that
1755 conform to neither PDR nor PBS.
1757 Each LSR of the LSP is expected to run its admission control rules
1758 and negotiate traffic parameters down if sufficient resources do not
1759 exist. The new parameter values are echoed back in the Label Mapping
1760 Message. LSRs might need to re-adjust their resources based on the
1761 new traffic parameter values.
1763 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 35 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1765 Appendix C. LSP Modification Using CR-LDP
1767 After a CR-LSP is set up, its bandwidth reservation may need to be
1768 changed by the network operator, due to the new requirements for the
1769 traffic carried on that CR-LSP. This contribution presents an
1770 approach to modify the bandwidth and possibly other parameters of an
1771 established CR-LSP using CR-LDP without service interruption. The
1772 LSP modification feature can be supported by CR-LDP with a minor
1773 extension of an _action indicator flag_. This feature has
1774 application in dynamic network resources management where traffic of
1775 different priorities and service classes is involved.
1777 Conventions used in this Appendix:
1779 L: LSP (Label Switched Path)
1780 Lid: LSPID (LSP Identifier)
1781 T: Traffic Parameters
1782 R: LSR (Label Switching Router)
1783 FTN: FEC To NHLFE
1784 FEC: Forwarding Equivalence Class
1785 NHLFE: Next Hop Label Forwarding Entity
1786 TLV: Type Length Value
1788 C.1 Introduction
1790 Consider an LSP L1 that has been established with its set of traffic
1791 parameters T0. A certain amount of bandwidth is reserved along the
1792 path of L1. Consider then that some changes are required on L1. For
1793 example, the bandwidth of L1 needs to be increased to accommodate
1794 the increased traffic on L1. Or the SLA associated with L1 needs to
1795 be modified because a different service class is desired. The
1796 network operator, in these cases, would like to modify the
1797 characteristics of L1, for example, to change its traffic parameter
1798 set from T0 to T1, without releasing the LSP L1 to interrupt the
1799 service. In some other cases, network operators may want to reroute
1800 a CR-LSP to a different path for either improved performance or
1801 better network resource utilization. In all these cases, LSP
1802 modification is required. In section C.2 below, a method to modify
1803 an active LSP using CR-LDP is presented. The concept of LSPID in CR-
1804 LDP is used to achieve the LSP modification, without releasing the
1805 LSP and interrupting the service and, without double booking the
1806 bandwidth. Only a minimum extension on CR-LDP, an action indication
1807 flag of _modify_ is needed in order to explicitly specify the
1808 behavior, and allow the existing LSPID to support other networking
1809 capabilities in the future. Section 4.5 specifies the action
1810 indication flag of _modify_ for CR-LDP. An example is described to
1811 demonstrate an application of the presented method in dynamically
1812 managing network bandwidth requirements without interrupting
1813 service.
1815 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 36 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1817 C.2 Basic Procedure
1819 LSP modification can only be allowed when the LSP is already set up
1820 and active. That is, modification is not defined nor allowed during
1821 the LSP establishment or label release/withdraw phases. Only
1822 modification requested by the ingress LSR of the LSP is considered
1823 in this draft for CR-LSP. Ingress LSR cannot modify an LSP before a
1824 previous modification procedure is completed.
1826 Assume that CR-LSP L1 is set up with LSPID L-id1, which is unique in
1827 the MPLS network. The ingress LSR R1 of L1 has in its FTN (FEC To
1828 NHLFE) table FEC1 -> Label A mapping where A is the outgoing label
1829 for LSP L1. To modify the characteristics of L1, R1 sends a Label
1830 Request Message. In the messages, the TLVs will have the new
1831 requested values, and the LSPID TLV is included which indicates the
1832 value of L-id1. The Traffic Parameters TLV, the ER-TLV, the Resource
1833 Class (color) TLV and the Preemption TLV can have values different
1834 from those in the original Label Request Message, which has been
1835 used to set up L1 earlier. Thus, L1 can be changed in its bandwidth
1836 request (traffic parameter TLV), its traffic service class (traffic
1837 parameter TLV), the route it traverses (ER TLV) and its setup and
1838 holding (Preemption TLV) priorities. The ingress LSR R1 now still
1839 has the entry in FTN as FEC1 -> Label A. R1 is waiting to establish
1840 another entry for FEC1.
1842 When an LSR Ri along the path of L1 receives the Label Request
1843 message, its behavior is the same as that of receiving any Label
1844 request message. The only extension is that Ri examines the LSPID
1845 carried in the Label Request Message, L-id1 and identifies if it
1846 already has L-id1. If Ri does not have L-id1, Ri behaves the same as
1847 receiving a new Label Request message. If Ri already has L-id1, Ri
1848 takes the newly received Traffic Parameter TLV and computes the new
1849 bandwidth required and derives the new service class. Compared with
1850 the already reserved bandwidth for L-id1, Ri now reserves only the
1851 difference of the bandwidth requirements. This prevents Ri from
1852 doing bandwidth double booking. If a new service class is requested,
1853 Ri also prepares to receive the traffic on L1 in, perhaps a
1854 different type of queue, just the same as handling it for a Label
1855 Request Message. Ri assigns a new label for the Label Request
1856 Message.
1858 When the Label Mapping message is received, two sets of labels exist
1859 for the same LSPID. Then the ingress LSR R1 will have two outgoing
1860 labels, A and B, associated with the same FEC, where B is the new
1861 outgoing label received for LSP L1. The ingress LSR R1 can now
1862 activate the new entry in FTN, FEC1 - > Label B. This means that R1
1863 swaps traffic on L1 to the new label _B_ (_new_ path) for L1. The
1864 packets can now be sent with the new label B, with the new set of
1865 traffic parameters if any, on a new path, that is, if a new path is
1866 requested in the Label Request Message for the modification. All the
1867 other LSRs along the path will start to receive the incoming packets
1868 with the new label. For the incoming new label, the LSR has already
1870 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 37 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1872 established its mapping to the new outgoing label. Thus, the packets
1873 will be sent out with the new outgoing label. The LSRs do not have
1874 to implement new procedures to track the new and old
1875 characteristics of the LSP.
1877 The ingress LSR R1 then starts to release the original label A for
1878 LSP L1. The Label Release Message is sent by R1 towards the down
1879 stream LSRs. The Release message carries the LSPID of L-id1 and the
1880 Label TLV to indicate which label is to be released. The Release
1881 Message is propagated to the egress LSR to release the original
1882 labels previously used for L1. Upon receiving the Label Release
1883 Message, LSR R1 examines the LSPID, L-id1 and finds out that the L-
1884 id1 has still another set of label (incoming/outgoing) under it.
1885 Thus, the old label is released without releasing the resource in
1886 use. That is, if the bandwidth has been decreased for L1, the delta
1887 bandwidth is released. Otherwise, no bandwidth is released. This
1888 modification procedure can not only be applied to modify the traffic
1889 parameters and/or service class of an active LSP, but also to
1890 reroute an existing LSP, and/or change its setup/holding priority if
1891 desired. After the release procedure, the modification of the LSP is
1892 completed.
1894 The method described above follows the normal behavior of Label
1895 Request / Mapping / Notification / Release /Withdraw procedure of a
1896 CR-LDP operated LSR with a specific action taken on LSPID. If Label
1897 Withdraw Message is used to withdraw a label associated with an
1898 LSPID, the Label TLV should be included to specify which label to
1899 withdraw. Since the LSPID can also be used for other feature
1900 support, an action indication flag of _modify_ assigned to the LSPID
1901 would explicitly explain the action/semantics that should be
1902 associated with the messaging procedure. The details of this flag
1903 are addressed in Section 4.5.
1905 C.3 Priority Handling
1907 When sending a Label Request Message for an active LSP L1 to request
1908 changes, the setup priority used in the label Request Message can be
1909 different from the one used in the previous Label Request Message,
1910 effectively indicating the priority of this _modification_ request.
1911 Network operators can use this feature to decide what priority is to
1912 be assigned to a modification request, based on their
1913 policies/algorithms and other traffic situations in the network. For
1914 example, the priority for modification can be determined by the
1915 priority of the customer/LSP. If a customer has exceeded the
1916 reserved bandwidth of its VPN LSP tunnel by too much, the
1917 modification request's priority may be given higher.
1918 The Label Request message for the modification of an active LSP can
1919 also be sent with a holding priority different from its previous
1920 one. This effectively changes the holding priority of the LSP. Upon
1921 receiving a Label Request Message that requests a new holding
1922 priority, the LSR assigns the new holding priority to the bandwidth.
1923 That is, the new holding priority is assigned to both the existing
1925 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 38 Internet Draft Constraint-Based LSP Setup using LDP August, 1999
1927 incoming / outgoing labels and the new labels to be established for
1928 the LSPID in question. In this way self-bumping is prevented.
1930 C.4 Modification Failure Case Handling
1932 A modification attempt may fail due to insufficient resource or
1933 other situations. A Notification message is sent back to the ingress
1934 LSR R1 to indicate the failure of Label Request Message that
1935 intended to modify the LSP. Retry may be attempted if desired by the
1936 network operator.
1938 If the LSP on the original path failed when a modification attempt
1939 is in progress, the attempt should be aborted by using the Label
1940 Abort Request message as specified in LDP draft.
1942 Full Copyright Statement
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1961 Jamoussi, et. al. draft-ietf-mpls-cr-ldp-03.txt 39