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1 MPLS Working Group Bilel Jamoussi, Editor
2 Internet Draft Nortel Networks
3 Expiration Date: August 1999
5 February 1999
7 Constraint-Based LSP Setup using LDP
9 draft-ietf-mpls-cr-ldp-01.txt
11 Status of this Memo
13 This document is an Internet-Draft and is in full conformance with
14 all provisions of Section 10 of RFC2026.
16 Internet-Drafts are working documents of the Internet Engineering
17 Task Force (IETF), its areas, and its working groups. Note that
18 other groups may also distribute working documents as Internet-
19 Drafts.
21 Internet-Drafts are draft documents valid for a maximum of six months
22 and may be updated, replaced, or obsoleted by other documents at any
23 time. It is inappropriate to use Internet- Drafts as reference
24 material or to cite them other than as "work in progress."
26 The list of current Internet-Drafts can be accessed at
27 http://www.ietf.org/ietf/1id-abstracts.txt
29 The list of Internet-Draft Shadow Directories can be accessed at
30 http://www.ietf.org/shadow.html.
32 Distribution of this memo is unlimited.
34 Copyright Notice
36 Copyright (C) The Internet Society (1998). All Rights Reserved.
38 Abstract
40 Label Distribution Protocol (LDP) is defined in [LDP] for
41 distribution of labels inside one MPLS domain. One of the most
42 important services that may be offered using MPLS in general and LDP
43 in particular is support for constraint-based routing of traffic
44 across the routed network. Constraint-based routing offers the
45 opportunity to extend the information used to setup paths beyond what
46 is available for the routing protocol. For instance, an LSP can be
47 setup based on explicit route constraints, QoS constraints, and
48 others. Constraint-based routing (CR) is a mechanism used to meet
49 Traffic Engineering requirements that have been proposed by [FRAME],
50 [ARCH] and [TER]. These requirements may be met by extending LDP for
51 support of constraint-based routed label switched paths (CRLSPs).
53 CR-LDP Specification - 2 - Exp. August 1999
55 Other uses exist for CRLSPs as well ([VPN1], [VPN2] and [VPN3]).
57 This draft specifies mechanisms and TLVs for support of CRLSPs using
58 LDP. The Explicit Route object and procedures are extracted from
59 [ER].
61 Table of Contents
63 1. Introduction ......................................... 3
64 2. Constraint-based Routing Overview .................... 3
65 2.1 Strict and Loose Explicit Routes ..................... 4
66 2.2 Traffic Characteristics .............................. 4
67 2.3 Pre-emption .......................................... 5
68 2.4 Route Pinning ........................................ 5
69 2.5 Resource Class ....................................... 5
70 3. Solution Overview .................................... 5
71 3.1 Required Messages and TLVs ........................... 7
72 3.2 Label Request Message ................................ 7
73 3.3 Label Mapping Message ................................ 8
74 3.4 Notification Message ................................. 9
75 3.5 Release & Withdraw Messages .......................... 9
76 4. Protocol Specification .............................. 9
77 4.1 Explicit Route TLV (ER-TLV) ......................... 10
78 4.2 Explicit Route Hop TLV .............................. 10
79 4.3 Traffic Parameters TLV .............................. 12
80 4.3.1 Semantics ........................................... 13
81 4.3.1.1 Frequency ........................................... 13
82 4.3.1.2 Peak Rate ........................................... 14
83 4.3.1.3 Committed Rate ...................................... 14
84 4.3.1.4 Excess Burst Size .................................... 14
85 4.3.1.5 Peak Rate Token Bucket................................ 14
86 4.3.1.6 Committed Data Rate Token Bucket ..................... 15
87 4.3.1.7 Weight ......................... ..................... 16
88 4.3.2 Procedures ........................................... 16
89 4.3.2.1 Label Request Message ................................ 16
90 4.3.2.2 Label Mapping Message ................................ 16
91 4.3.2.3 Notification Message ................................. 17
92 4.4 Preemption TLV ....................................... 18
93 4.5 LSPID TLV ........................................... 18
94 4.6 Resource Class TLV .................................. 19
95 4.7 ER-Hop Semantics ..................................... 19
96 4.7.1 ER-Hop 1 TLV IPv4 Prefix ............................. 20
97 4.7.2 ER-Hop 2 TLV IPv6 Prefix ............................. 20
98 4.7.3 ER-Hop 3 TLV AS Number ............................... 21
99 4.7.4 ER-Hop 4 TLV LSPID ................................... 21
100 4.8 Processing of the ER-TLV ............................. 22
101 4.8.1 Selection of the next hop ............................ 22
102 4.8.2 Adding the Label Request Message to the next hop ..... 24
103 4.9 Route Pinning TLV ................................... 24
104 4.10 CR-LSP FEC Element ................................... 24
105 4.11 Error Subcodes ...................................... 25
107 CR-LDP Specification - 3 - Exp. August 1999
109 5. Security Considerations .............................. 26
110 6. Acknowledgement ...................................... 26
111 7. References ........................................... 26
112 8. Author Information ................................... 28
114 Appendix A CRLSP Establishment Examples ......................... 30
115 A.1 Strict Explicit Route Example ........................ 30
116 A.2 Node Groups and Specific Nodes Example ............... 31
118 Appendix B QoS Service Examples ................................. 34
119 B.1 Service Examples ..................................... 34
120 B.2 Establishing CR-LSP Supporting Real-Time Applications. 35
121 B.3 Establishing CR-LSP Delay Insensitive Applications ... 36
123 1. Introduction
125 The need for constraint-based routing (CR) in MPLS has been explored
126 elsewhere [ARCH], [FRAME], and [TER]. Explicit routing is a subset
127 of the more general constraint-based routing function. At the MPLS WG
128 meeting held during the Washington IETF there was consensus that LDP
129 should support explicit routing of LSPs with provision for indication
130 of associated (forwarding) priority. In the Chicago meeting, a
131 decision was made that support for explicit path setup in LDP will be
132 moved to a separate document. This document provides that support and
133 it has been accepted as a working document in the Orlando meeting.
134 This specification proposes an end-to-end setup mechanism of a
135 constraint-based routed LSP (CRLSP) initiated by the ingress LSR. We
136 also specify mechanisms to provide means for reservation of resources
137 using LDP.
139 This document introduce TLVs and procedures that provide support for:
141 - Strict and Loose Explicit Routing
142 - Specification of Traffic Parameters
143 - Route Pinning
144 - CRLSP Pre-emption though setup/holding priorities
145 - Handling Failures
146 - LSPID
147 - Resource Class
149 Section 2 introduces the various constraints defined in this
150 specification. Section 3 outlines the CR-LDP solution. Section 4
151 defines the TLVs and procedures used to setup constraint-based routed
152 label switched paths. Appendix A provides several examples of CR-LSP
153 path setup. Appendix B provides Service Definition Examples.
155 2. Constraint-based Routing Overview
157 Constraint-based routing is a mechanism that supports the Traffic
158 Engineering requirements defined in [TER]. Explicit Routing is a
159 subset of the more general constraint-based routing where the
161 CR-LDP Specification - 4 - Exp. August 1999
163 constraint is the explicit route (ER). Other constraints are defined
164 to provide a network operator with control over the path taken by an
165 LSP. This section is an overview of the various constraints supported
166 by this specification.
168 2.1 Strict and Loose Explicit Routes
170 Like any other LSP an CRLSP is a path through an MPLS network. The
171 difference is that while other paths are setup solely based on
172 information in routing tables or from a management system, the
173 constraint-based route is calculated at one point at the edge of
174 network based on criteria, including but not limited to routing
175 information. The intention is that this functionality shall give
176 desired special characteristics to the LSP in order to better support
177 the traffic sent over the LSP. The reason for setting up CRLSPs,
178 might be that one wants to assign certain bandwidth or other Service
179 Class characteristics to the LSP, or that one wants to make sure that
180 alternative routes use physically separate paths through the network.
182 An explicit route is represented in a Label Request Message as a
183 list of nodes or groups of nodes along the constraint-based route.
184 When the CRLSP is established, all or a subset of the nodes in a
185 group may be traversed by the LSP. Certain operations to be
186 performed along the path can also be encoded in the constraint-based
187 route.
189 The capability to specify, in addition to specified nodes, groups of
190 nodes, of which a subset will be traversed by the CRLSP, allows the
191 system a significant amount of local flexibility in fulfilling a
192 request for a constraint-based route. This allows the generator of
193 the constraint-based route to have some degree of imperfect
194 information about the details of the path.
196 The constraint-based route is encoded as a series of ER-Hops
197 contained in a constraint-based route TLV. Each ER-Hop may identify
198 a group of nodes in the constraint-based route. A constraint-based
199 route is then a path including all of the identified groups of nodes.
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
212 specify a constraint on the delay variation that the CRLDP MPLS
213 domain may introduce to a path's traffic.
215 CR-LDP Specification - 5 - Exp. August 1999
217 2.3 Pre-emption
219 CR-LDP signals the resources required by a path on each hop of the
220 route. If a route with sufficient resources can not be found,
221 existing paths may be rerouted to reallocate resources to the new
222 path. This is the process of path pre-emption. Setup and holding
223 priorities are used to rank existing paths (holding priority) and the
224 new path (setup priority) to determine if the new path can pre-empt
225 an existing path.
227 The setupPriority of a new CRLSP and the holdingPriority attributes
228 of the existing CRLSP are used to specify priorities. Signaling a
229 higher holding priority expresses that the path, once it has been
230 established, should have a lower chance of being pre-empted.
231 Signaling a higher setup priority expresses the expectation that, in
232 the case that resource are unavailable, the path is more likely to
233 pre-empt other paths. The exact rules determining bumping are an
234 aspect of network policy.
236 The allocation of setup and holding priority values to paths is an
237 aspect of network policy.
239 The setup and holding priority values range from zero (0) to seven
240 (7). The value zero (0) is the priority assigned to the most
241 important path. It is referred to as the highest priority. Seven (7)
242 is the priority for the least important path. The use of default
243 priority values is an aspect of network policy.
245 The setupPriority of a CRLSP should not be higher (numerically less)
246 than its holdingPriority since it might bump an LSP and be bumped by
247 next "equivalent" request.
249 2.4 Route Pinning
251 Route pinning is applicable to segments of an LSP that are loosely
252 routed - i.e. those segments which are specified with a next hop with
253 the 'L' bit set or where the next hop is an "abstract node". A CRLSP
254 may be setup using route pinning if it is undesirable to change the
255 path used by an LSP because a better next hop becomes available at
256 some LSR along the loosely routed portion of the LSP.
258 2.5 Resource Class
260 Network resources may be classified in various ways by the network
261 operator. These classes are also known as "colors" or "administrative
262 groups". When an CR-LSP is being established, it's necessary to
263 indicate which resource classes the CR-LSP can draw from.
265 3. Solution Overview
267 CRLSP over LDP Specification is designed with the following goals:
269 CR-LDP Specification - 6 - Exp. August 1999
271 1. Meet the requirements outlined in [TER] for performing traffic
272 engineering and provide a solid foundation for performing more
273 general constraint-based routing.
275 2. Build on already specified functionality that meets the
276 requirements whenever possible. Hence, this specifications is
277 based on [LDP] and the Explicit Route object and procedures
278 defined in [ER].
280 3. Keep the solution simple.
282 In this document, support for unidirectional point-to-point CRLSPs is
283 specified. Support for point-to-multipoint, multipoint-to-point, is
284 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 [LDP]:
289 - Basic and/or Extended Discovery Mechanisms.
291 - Use the Label Request Message defined in [LDP] in downstream on
292 demand label advertisement mode with ordered control.
294 - Use the Label Mapping Message defined in [LDP] in downstream on
295 demand mode with ordered control.
297 - Use the Notification Message defined in [LDP].
299 - Use the Withdraw and Release Messages defined in [LDP].
301 - Use the Loop Detection (in the case of loosely routed segments
302 of a CRLSP) mechanisms defined in [LDP].
304 In addition, the following functionality is added to what's defined
305 in [LDP]:
307 - The Label Request Message used to setup a CRLSP includes one or
308 more CR-TLVs defined in Section 4. For instance, the Label Request
309 Message may include the ER-TLV.
311 - An LSR implicitly infers ordered control from the existence of
312 one or more CR-TLVs in the Label Request Message. This means that
313 the LSR can still be configured for independent control for LSPs
314 established as a result of dynamic routing. However, when a Label
315 Request Message includes one or more of the CR-TLVs, then ordered
316 control is used to setup the CRLSP. Note that this is also true
317 for the loosely routed parts of a CRLSP.
319 - New status codes are defined to handle error notification for
320 failure of established paths specified in the CR-TLV.
322 CR-LDP Specification - 7 - Exp. August 1999
324 Examples of CRLSP establishment are given in Appendix A to illustrate
325 how the mechanisms described in this draft work.
327 3.1 Required Messages and TLVs
329 Any Messages, TLVs, and procedures not defined explicitly in this
330 document are defined in the [LDP] Specification. The state
331 transitions which relate to CR-LDP messages can be found in [LDP-
332 STATE].
334 The following subsections are meant as a cross reference to the [LDP]
335 document and indication of additional functionality beyond what's
336 defined in [LDP] where necessary.
338 3.2 Label Request Message
340 The Label Request Message is as defined in 3.5.8 of [LDP] with the
341 following modifications (required only if any of the CR-TLVs is
342 included in the Label Request Message):
344 - Only a single FEC-TLV may be included in the Label Request
345 Message. The CR-LSP FEC TLV should be used.
347 - The Return Message ID TLV is MANDATORY.
349 - The Optional Parameters TLV includes the definition of any of
350 the Constraint-based TLVs specified in Section 4.
352 - The Procedures to handle the Label Request Message are augmented
353 by the procedures for processing of the CR-TLVs as defined in
354 Section 4.
356 The encoding for the CR-LDP Label Request Message is as follows:
358 CR-LDP Specification - 8 - Exp. August 1999
360 0 1 2 3
361 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
362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
363 |U| Label Request (0x0401) | Message Length |
364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
365 | Message ID |
366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
367 | FEC TLV |
368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
369 | Return Message ID TLV (mandatory) |
370 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
371 | LSPID TLV (CR-LDP, mandatory) |
372 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
373 | ER-TLV (CR-LDP, optional) |
374 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
375 | Traffic TLV (CR-LDP, optional) |
376 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
377 | Pinning TLV (CR-LDP, optional) |
378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
379 | Resource Class TLV (CR-LDP, optional) |
380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
381 | Pre-emption TLV (CR-LDP, optional) |
382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
384 3.3 Label Mapping Message
386 The Label Mapping Message is as defined in 3.5.7 of [LDP] with the
387 following modifications:
389 - Only a single Label-TLV may be included in the Label Mapping
390 Message.
392 - The Label Mapping Message MUST include Label Request Message ID
393 TLV.
395 - The Label Mapping Message MUST include LSPID TLV.
397 - The Label Mapping Message Procedures are limited to downstream
398 on demand ordered control mode.
400 A Mapping message is transmitted by a downstream LSR to an upstream
401 LSR under one of the following conditions:
403 1. The LSR is the egress end of the CRLSP and an upstream mapping
404 has been requested.
406 2. The LSR received a mapping from its downstream next hop LSR for
407 an CRLSP for which an upstream request is still pending.
409 The encoding for the CR-LDP Label Mapping Message is as follows:
411 CR-LDP Specification - 9 - Exp. August 1999
413 0 1 2 3
414 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
415 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
416 |U| Label Mapping (0x0400) | Message Length |
417 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
418 | Message ID |
419 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
420 | FEC TLV |
421 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
422 | Label TLV |
423 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
424 | Label Request Message ID TLV (mandatory) |
425 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
426 | LSPID TLV (CR-LDP, mandatory) |
427 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
428 | Traffic TLV (CR-LDP, optional) |
429 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
431 3.4 Notification Message
433 The Notification Message is as defined in Section 3.5.1 of [LDP] and
434 the Status TLV encoding is as defined in Section 3.4.7 of [LDP].
436 Establishment of an Explicitly Routed LSP may fail for a variety of
437 reasons. All such failures are considered advisory conditions and
438 they are signaled by the Notification Message.
440 Notification Messages carry Status TLVs to specify events being
441 signaled. New status codes are defined in Section 4.11 to signal
442 error notifications associated with the establishment of a CRLSP and
443 the processing of the CR-TLV.
445 The Notification Message must carry the LSPID TLV of the
446 corresponding CRLSP.
448 3.5 Release and Withdraw Messages
450 The Label Release and Label Withdraw Messages are used as specified
451 in [LDP] to clear CR-LSPs. These message may also carry the LSPID
452 TLV.
454 4. Protocol Specification
456 The Label Request Messages defined in [LDP] optionally carries one or
457 more of the optional Constraint-based Routing TLVs (CR-TLVs) defined
458 in this section. If needed, other constraints can be supported later
459 through the definition of new TLVs. In this specification, the
460 following TLVs are defined:
462 - Explicit Route TLV
464 CR-LDP Specification - 10 - Exp. August 1999
466 - Explicit Route Hop TLV
467 - Traffic Parameters TLV
468 - Preemption TLV
469 - LSPID TLV
470 - Route Pinning TLV
471 - Resource Class TLV
472 - CRLSP FEC TLV
474 4.1 Explicit Route TLV (ER-TLV)
476 The ER-TLV is an object that specifies the path to be taken by the
477 LSP being established. It is composed of one or more Explicit Route
478 Hop TLVs (ER-Hop TLVs) defined in Section 4.2.
480 0 1 2 3
481 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
482 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
483 |U|F| ER-TLV (0x0800) | Length |
484 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
485 | ER-Hop TLV 1 |
486 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
487 | ER-Hop TLV 2 |
488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
489 ~ ............ ~
490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
491 | ER-Hop TLV n |
492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
494 U bit
495 Unknown TLV bit. As defined in [LDP].
497 F bit
498 Forward unknown TLV bit. As defined in [LDP].
500 Type
501 A two byte field carrying the value of the ER-TLV type which
502 is 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. Each ER-Hop TLV has the form:
515 CR-LDP Specification - 11 - Exp. August 1999
517 0 1 2 3
518 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
519 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
520 |U|F| ER-Hop-Type | Length |
521 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
522 |L| Content // |
523 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
525 U bit
526 Unknown TLV bit. As defined in [LDP].
528 F bit
529 Forward unknown TLV bit. As defined in [LDP].
531 ER-Hop Type
532 A fourteen-bit field indicating the type of contents of
533 the ER-Hop. Currently defined values are:
535 Value Type
536 ----- ------------------------
537 0x801 IPv4 prefix
538 0x802 IPv6 prefix
539 0x803 Autonomous system number
540 0x804 LSPID
542 Length
543 Specifies the length of the value field in bytes.
545 L bit
546 The L bit is an attribute of the ER-Hop. The L bit is set if the
547 ER-Hop represents a loose hop in the explicit route. If the bit is
548 not set, the ER-Hop represents a strict hop in the explicit route.
550 The L bit in the ER-Hop is a one-bit attribute. If the L bit is
551 set, then the value of the attribute is "loose." Otherwise, the
552 value of the attribute is "strict." For brevity, we say that if
553 the value of the ER-Hop attribute is loose then it is a "loose
554 ER-Hop." Otherwise, it's a "strict ER-Hop." Further, we say that
555 the abstract node of a strict or loose ER-Hop is a strict or a
556 loose node, respectively. Loose and strict nodes are always
557 interpreted relative to their prior abstract nodes.
559 The path between a strict node and its prior node MUST include
560 only network nodes from the strict node and its prior abstract
561 node.
563 The path between a loose node and its prior node MAY include other
564 network nodes which are not part of the strict node or its prior
565 abstract node.
567 CR-LDP Specification - 12 - Exp. August 1999
569 Contents
570 A variable length field containing the node or abstract node that
571 is the consecutive nodes that make up the explicit routed LSP.
573 4.3 Traffic Parameters TLV
575 The following sections describe the CRLSP Traffic Parameters. The
576 required characteristics of a CRLSP are expressed by the Traffic
577 Parameter values.
579 A Traffic Parameters TLV, is used to signal the Traffic Parameter
580 values. The Traffic Parameters are defined in the subsequent
581 sections.
583 The Traffic Parameters TLV contains a Flags field, a Frequency, a
584 Weight, and the five Traffic Parameters PDR, PBS, CDR, CBS, EBS. The
585 Traffic Parameters TLV is shown below:
587 0 1 2 3
588 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
589 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
590 |U|F| Traf. Param. TLV (0x0810)| Length |
591 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
592 | Flags | Frequency | Reserved | Weight |
593 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
594 | Peak Data Rate (PDR) |
595 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
596 | Peak Burst Size (PBS) |
597 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
598 | Committed Data Rate (CDR) |
599 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
600 | Committed Burst Size (CBS) |
601 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
602 | Excess Burst Size (EBS) |
603 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
605 U bit
606 Unknown TLV bit. As defined in [LDP].
608 F bit
609 Forward unknown TLV bit. As defined in [LDP].
611 Type
612 A fourteen-bit field carrying the value of the ER-TLV type which
613 is 0x810.
615 Length
616 Specifies the length of the value field in bytes.
618 Flags
619 The Flags field is shown below:
621 CR-LDP Specification - 13 - Exp. August 1999
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 - VeryFrequest
648 3-255 - Reserved
650 Reserved
651 Zero on transmission. Ignored on receipt.
653 Weight
654 An 8 bit unsigned integer indicating the weight of the CRLSP.
655 Valid weight values are from 1 to 255. The value 0 means
656 that weight is not applicable for the CRLSP.
658 Traffic Parameters
659 Each Traffic Parameter is encoded as a 32 bit IEEE single-
660 precision floating point number. A value of positive infinity is
661 represented as an IEEE single-precision floating-point number with
662 an exponent of all ones (255) and a sign and mantissa of all
663 zeros. The values PDR and CDR are in units of bytes per second.
664 The values PBS, CBS and EBS are in units of bytes.
666 The value of PDR MUST be greater than or equal to the value of CDR
667 in a correctly encoded Traffic Parameters TLV.
669 4.3.1 Semantics
671 4.3.1.1 Frequency
673 CR-LDP Specification - 14 - Exp. August 1999
675 The Frequency specifies at what granularity the CDR allocated to the
676 CRLSP is made available. The value VeryFrequently means that the
677 available rate should average at least the CDR when measured over any
678 time interval equal to or longer than the shortest packet time at the
679 CDR. The value Frequently means that the available rate should
680 average at least the CDR when measured over any time interval equal
681 to or longer than a small number of shortest packet times at the CDR.
682 The value Unspecified means that the CDR MAY be provided at any
683 granularity.
685 4.3.1.2 Peak Rate
687 The Peak Rate defines the maximum rate at which traffic SHOULD be
688 sent to the CRLSP. The Peak Rate is useful for the purpose of
689 resource allocation. If resource allocation within the MPLS domain
690 depends on the Peak Rate value then it should be enforced at the
691 ingress to the MPLS domain.
693 The Peak Rate is defined in terms of the two Traffic Parameters PDR
694 and PBS, see section 4.3.1.5 below.
696 4.3.1.3 Committed Rate
698 The Committed Rate defines the rate that the MPLS domain commits to
699 be available to the CRLSP.
701 The Committed Rate is defined in terms of the two Traffic Parameters
702 CDR and CBS, see section 4.3.1.6 below.
704 4.3.1.4 Excess Burst Size
706 The Excess Burst Size may be used at the edge of an MPLS domain for
707 the purpose of traffic conditioning. The EBS MAY be used to measure
708 the extent by which the traffic sent on a CRLSP exceeds the committed
709 rate.
711 The possible traffic conditioning actions, such as passing, marking
712 or dropping, are specific to the MPLS domain.
714 The Excess Burst Size is defined together with the Committed Rate,
715 see section 4.3.1.6 below.
717 4.3.1.5 Peak Rate Token Bucket
719 The Peak Rate of a CRLSP is specified in terms of a token bucket P
720 with token rate PDR and maximum token bucket size PBS.
722 The token bucket P is initially (at time 0) full, i.e., the token
723 count Tp(0) = PBS. Thereafter, the token count Tp, if less than PBS,
724 is incremented by one PDR times per second. When a packet of size B
725 bytes arrives at time t, the following happens:
727 CR-LDP Specification - 15 - Exp. August 1999
729 o If Tp(t)-B >= 0, the packet is not in excess of the peak
730 rate and Tp is decremented by B down to the minimum value
731 of 0, else
733 o the packet is in excess of the peak rate and Tp is
734 not decremented.
736 Note that according to the above definition, a positive infinite
737 value of either PDR or PBS implies that arriving packets are never in
738 excess of the peak rate.
740 The actual implementation of a LSR doesn't need to be modeled
741 according to the above formal token bucket specification.
743 4.3.1.6 Committed Data Rate Token Bucket
745 The committed rate of a CRLSP is specified in terms of a token bucket
746 C with rate CDR. The extent by which the offered rate exceeds the
747 committed rate MAY be measured in terms of another token bucket E,
748 which also operates at rate CDR. The maximum size of the token
749 bucket C is CBS and the maximum size of the token bucket E is EBS.
751 The token buckets C and E are initially (at time 0) full, i.e., the
752 token count Tc(0) = CBS and the token count Te(0) = EBS. Thereafter,
753 the token counts Tc and Te are updated CDR times per second as
754 follows:
756 o If Tc is less than CBS, Tc is incremented by one, else
758 o if Te is less then EBS, Te is incremented by one, else
760 o neither Tc nor Te is incremented.
762 When a packet of size B bytes arrives at time t, the following
763 happens:
765 o If Tc(t)-B >= 0, the packet is not in excess of the Committed
766 Rate and Tc is decremented
767 by B down to the minimum value of 0, else
769 o if Te(t)-B >= 0, the packet is in excess of the Committed Rate
770 but is not in excess of the EBS and Te is
771 decremented by B down to the minimum value of 0, else
773 o the packet is in excess of both the Committed Rate and the EBS
774 and neither Tc nor Tc is decremented.
776 Note that according to the above specification, a CDR value of
777 positive infinity implies that arriving packets are never in excess
778 of either the Committed Rate or EBS. A positive infinite value of
779 either CBS or EBS implies that the respective limit cannot be
781 CR-LDP Specification - 16 - Exp. August 1999
783 exceeded.
785 The actual implementation of a LSR doesn't need to be modeled
786 according to the above formal specification.
788 4.3.1.7 Weight
790 The weight determines the CRLSP's relative share of the possible
791 excess bandwidth above its committed rate. The definition of
792 "relative share" is MPLS domain specific.
794 4.3.2 Procedures
796 4.3.2.1 Label Request Message
798 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
799 which the value of PDR is less than the value of CDR then it MUST
800 send a Notification Message including the Status code Traffic
801 Parameters Unavailable to the upstream LSR from which it received the
802 erroneous message.
804 If a Traffic Parameter is indicated as Negotiable in the Label
805 Request Message by the corresponding Negotiable Flag then an LSR MAY
806 replace the Traffic Parameter value with a smaller value.
808 If the Weight is indicated as Negotiable in the Label Request Message
809 by the corresponding Negotiable Flag then an LSR may adjust replace
810 the Weight value with a lower value (down to 1).
812 If, after possible Traffic Parameter negotiation, an LSR can support
813 the CRLSP Traffic Parameters then the LSR MUST reserve the
814 corresponding resources for the CRLSP.
816 If, after possible Traffic Parameter negotiation, an LSR cannot
817 support the CRLSP Traffic Parameters then the LSR MUST send a
818 notification message that contains the Resource Unavailable status
819 code.
821 4.3.2.2 Label Mapping Message
823 If an LSR receives an incorrectly encoded Traffic Parameters TLV in
824 which the value of PDR is less than the value of CDR then it MUST
825 send a Label Release message containing the Status code Traffic
826 Parameters Unavailable to the LSR from which it received the
827 erroneous message.
829 The egress LSR MUST include the (possibly negotiated) Traffic
830 Parameters and Weight in the Label Mapping message.
832 The Traffic Parameters and the Weight in a Label Mapping message MUST
833 be forwarded unchanged.
835 CR-LDP Specification - 17 - Exp. August 1999
837 An LSR SHOULD adjust the resources that it reserved for a CRLSP when
838 it receives a Label Mapping Message if the Traffic Parameters differ
839 from those in the corresponding Label Request Message.
841 4.3.2.3 Notification Message
843 If an LSR receives a Notification Message for a CRLSP, it SHOULD
844 release any resources that it possibly had reserved for the CRLSP.
846 In addition, on receiving a Notification Message from a Downstream
847 LSR that is associated with a Label Request from an upstream LSR, the
848 local LSR MUST propagate the Notification message using the
849 procedures in [LDP].
851 4.4 Preemption TLV
853 0 1 2 3
854 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
855 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
856 |U|F| Preemption-TLV (0x0820) | Length |
857 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
858 | SetPrio | HoldPrio | Reserved |
859 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
861 U bit
862 Unknown TLV bit. As defined in [LDP].
864 F bit
865 Forward unknown TLV bit. As defined in [LDP].
867 Type
868 A fourteen-bit field carrying the value of the Preemption-TLV
869 type which is 0x810.
871 Length
872 Specifies the length of the value field in bytes.
874 Reserved
875 Zero on transmission. Ignored on receipt.
877 SetPrio
878 A SetupPriority of value zero (0) is the priority assigned to the
879 most important path. It is referred to as the highest priority.
880 Seven (7) is the priority for the least important path. The higher
881 the setup priority, the more paths CR-LDP can bump to set up the
882 path.
884 HoldPrio
885 A HoldingPriority of value zero (0) is the priority assigned to
886 the most important path. It is referred to as the highest
887 priority. Seven (7) is the priority for the least important path.
889 CR-LDP Specification - 18 - Exp. August 1999
891 The higher the holding priority, the less likely it is for CR-LDP
892 to reallocate its bandwidth to a new path.
894 4.5 LSPID TLV
896 LSPID is a unique identifier of a CRLSP within an MPLS network.
898 The LSPID is composed of the ingress LSR Router ID and a Locally
899 unique CRLSP ID to that LSR.
901 The LSPID is useful in network management, in CR-LSP repair, and in
902 using an already established CR-LSP as a hop in an ER-TLV.
904 0 1 2 3
905 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
906 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
907 |U|F| LSPID-TLV (0x0821) | Length |
908 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
909 | Reserved | Local CRLSP ID |
910 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
911 | Ingress LSR Router ID |
912 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
914 U bit
915 Unknown TLV bit. As defined in [LDP].
917 F bit
918 Forward unknown TLV bit. As defined in [LDP].
920 Type
921 A fourteen-bit field carrying the value of the LSPID-TLV
922 type which is 0x821.
924 Length
925 Specifies the length of the value field in bytes.
927 Reserved
928 Zero on transmission. Ignored on receipt.
930 Local CRLSP ID
931 The Local LSP ID is an identifier of the CRLSP locally unique
932 within the Ingress LSR originating the CRLDP.
934 Ingress LSR Router ID
935 A 4 byte field indicating the Ingress LSR ID.
937 4.6 Resource Class (Color) TLV
939 The Resource Class as defined in [TER] is used to specify which links
940 are acceptable by this CRLSP. This information allows for the
942 CR-LDP Specification - 19 - Exp. August 1999
944 networks topology to be pruned.
946 0 1 2 3
947 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
948 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
949 |U|F| ResCls-TLV (0x0822) | Length |
950 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
951 | RsCls |
952 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
954 U bit
955 Unknown TLV bit. As defined in [LDP].
957 F bit
958 Forward unknown TLV bit. As defined in [LDP].
960 Type
961 A fourteen-bit field carrying the value of the ResCls-TLV
962 type which is 0x822.
964 Length
965 Specifies the length of the value field in bytes.
967 RsCls
968 The Resource Class bit mask indicating which of the
969 32 "administrative groups" or "colors" of links
970 the CRLSP can traverse.
972 4.7 ER-Hop semantics
974 4.7.1. ER-Hop 1: The IPv4 prefix
976 The abstract node represented by this ER-Hop is the set of nodes
977 which have an IP address which lies within this prefix. Note that a
978 prefix length of 32 indicates a single IPv4 node.
980 0 1 2 3
981 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
982 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
983 |U|F| 0x801 | Length |
984 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
985 |L| Reserved | PreLen |
986 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
987 | IPv4 Address (4 bytes) |
988 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
990 U bit
991 Unknown TLV bit. As defined in [LDP].
993 F bit
994 Forward unknown TLV bit. As defined in [LDP].
996 CR-LDP Specification - 20 - Exp. August 1999
998 Type
999 IPv4 Address 0x801
1001 Length
1002 Specifies the length of the value field in bytes.
1004 L Bit
1005 Set to indicate Loose hop.
1006 Cleared to indicate a strict hop.
1008 Reserved
1009 Zero on transmission. Ignored on receipt.
1011 PreLen
1012 Prefix Length 1-32
1014 IP Address
1015 A four byte field indicating the IP Address.
1017 4.7.2. ER-Hop 2: The IPv6 address
1019 0 1 2 3
1020 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
1021 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1022 |U|F| 0x802 | Length |
1023 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1024 |L| Reserved | PreLen |
1025 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1026 | IPV6 address |
1027 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1028 | IPV6 address (continued) |
1029 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1030 | IPV6 address (continued) |
1031 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1032 | IPV6 address (continued) |
1033 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1035 U bit
1036 Unknown TLV bit. As defined in [LDP].
1038 F bit
1039 Forward unknown TLV bit. As defined in [LDP].
1041 Type
1042 0x802 IPv6 address
1044 Length
1045 Specifies the length of the value field in bytes.
1047 L Bit
1048 Set to indicate Loose hop.
1050 CR-LDP Specification - 21 - Exp. August 1999
1052 Cleared to indicate a strict hop.
1054 Reserved
1055 Zero on transmission. Ignored on receipt.
1057 PreLen
1058 Prefix Length 1-128
1060 IPv6 address
1061 A 128-bit unicast host address.
1063 4.7.3. ER-Hop 32: The autonomous system number
1065 The abstract node represented by this ER-Hop is the set of nodes
1066 belonging to the autonomous system.
1068 0 1 2 3
1069 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
1070 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1071 |U|F| 0x803 | Length |
1072 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1073 |L| Reserved | AS Number |
1074 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1076 U bit
1077 Unknown TLV bit. As defined in [LDP].
1079 F bit
1080 Forward unknown TLV bit. As defined in [LDP].
1082 Type
1083 AS Number 0x803
1085 Length
1086 Specifies the length of the value field in bytes.
1088 L Bit
1089 Set to indicate Loose hop.
1090 Cleared to indicate a strict hop.
1092 Reserved
1093 Zero on transmission. Ignored on receipt.
1095 AS Number
1096 Autonomous System number
1098 4.7.4. ER-Hop 4: LSPID
1100 The LSPID is used to identify the tunnel ingress point as the next
1101 hop in the ER. This ER-Hop allows for stacking new CR-LSPs within an
1102 already established CR-LSP. It also allows for splicing the CR-LSP
1104 CR-LDP Specification - 22 - Exp. August 1999
1106 being established with an existing CR-LSP.
1108 0 1 2 3
1109 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
1110 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1111 |U|F| 0x804 | Length |
1112 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1113 |L| Reserved | Local LSPID |
1114 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1115 | Ingress LSR Router ID |
1116 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1118 U bit
1119 Unknown TLV bit. As defined in [LDP].
1121 F bit
1122 Forward unknown TLV bit. As defined in [LDP].
1124 Type
1125 LSPID 0x804
1127 Length
1128 Specifies the length of the value field in bytes.
1130 L Bit
1131 Set to indicate Loose hop.
1132 Cleared to indicate a strict hop.
1134 Reserved
1135 Zero on transmission. Ignored on receipt.
1137 Local LSPID
1138 A 2 byte field indicating the LSPID which is unique
1139 with reference to the its Ingress LSR.
1141 Ingress LSR Router ID
1142 A 4 byte field indicating the Ingress LSR ID.
1144 4.8. Processing of the Explicit Route TLV
1146 4.8.1. Selection of the next hop
1148 A Label Request Message containing a explicit route TLV must
1149 determine the next hop for this path. Selection of this next hop may
1150 involve a selection from a set of possible alternatives. The
1151 mechanism for making a selection from this set is implementation
1152 dependent and is outside of the scope of this specification.
1153 Selection of particular paths is also outside of the scope of this
1154 specification, but it is assumed that each node will make a best
1155 effort attempt to determine a loop-free path. Note that such best
1157 CR-LDP Specification - 23 - Exp. August 1999
1159 efforts may be overridden by local policy.
1161 To determine the next hop for the path, a node performs the following
1162 steps:
1164 1) The node receiving the Label Request Message must first
1165 evaluate the first ER-Hop. If the L bit is not set in the first
1166 ER-Hop and if the node is not part of the abstract node described
1167 by the first ER-Hop, it has received the message in error, and
1168 should return a "Bad initial ER-Hop" error. If the L bit is set
1169 and the local node is not part of the abstract node described by
1170 the first ER-Hop, the node selects a next hop that is along the
1171 path to the abstract node described by the first ER-Hop. If there
1172 is no first ER-Hop, the message is also in error and the system
1173 should return a "Bad Explicit Routing TLV" error.
1175 2) If there is no second ER-Hop, this indicates the end of the
1176 explicit route. The explicit route TLV should be removed from the
1177 Label Request Message. This node may or may not be the end of the
1178 LSP. Processing continues with section 4.8.2, where a new
1179 explicit route TLV may be added to the Label Request Message.
1181 3) If the node is also a part of the abstract node described by
1182 the second ER-Hop, then the node deletes the first ER-Hop and
1183 continues processing with step 2, above. Note that this makes the
1184 second ER-Hop into the first ER-Hop of the next iteration.
1186 4) The node determines if it is topologically adjacent to the
1187 abstract node described by the second ER-Hop. If so, the node
1188 selects a particular next hop which is a member of the abstract
1189 node. The node then deletes the first ER-Hop and continues
1190 processing with section 4.8.2.
1192 5) Next, the node selects a next hop within the abstract node of
1193 the first ER-Hop that is along the path to the abstract node of
1194 the second ER-Hop. If no such path exists then there are two
1195 cases:
1197 5a) If the second ER-Hop is a strict ER-Hop, then there is an
1198 error and the node should return a "Bad strict node" error.
1200 5b) Otherwise, if the second ER-Hop is a loose ER-Hop, then the
1201 node selects any next hop that is along the path to the next
1202 abstract node. If no path exists within the MPLS domain, then
1203 there is an error, and the node should return a "Bad loose node"
1204 error.
1206 6) Finally, the node replaces the first ER-Hop with any ER-Hop
1207 that denotes an abstract node containing the next hop. This is
1208 necessary so that when the explicit route is received by the next
1209 hop, it will be accepted.
1211 CR-LDP Specification - 24 - Exp. August 1999
1213 7) Progress the Label Request Message to the next hop.
1215 4.8.2. Adding ER-Hops to the explicit route TLV
1217 After selecting a next hop, the node may alter the explicit route in
1218 the following ways.
1220 If, as part of executing the algorithm in section 4.8.1, the explicit
1221 route TLV is removed, the node may add a new explicit route TLV.
1223 Otherwise, if the node is a member of the abstract node for the first
1224 ER-Hop, then a series of ER-Hops may be inserted before the first
1225 ER-Hop or may replace the first ER-Hop. Each ER-Hop in this series
1226 must denote an abstract node that is a subset of the current abstract
1227 node.
1229 Alternately, if the first ER-Hop is a loose ER-Hop, an arbitrary
1230 series of ER-Hops may be inserted prior to the first ER-Hop.
1232 4.9 Route Pinning TLV
1234 0 1 2 3
1235 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
1236 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1237 |U|F| 0x823 | Length |
1238 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1239 |P| Reserved |
1240 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1242 U bit
1243 Unknown TLV bit. As defined in [LDP].
1245 F bit
1246 Forward unknown TLV bit. As defined in [LDP].
1248 Type
1249 Pinning-TLV type 0x823
1251 Length
1252 Specifies the length of the value field in bytes.
1254 P Bit
1255 The P bit is set to 1 to indicate that route pinning is requested.
1256 The P bit is set to 0 to indicate that route pinning is not
1257 requested
1259 Reserved
1260 Zero on transmission. Ignored on receipt.
1262 4.10 CRLSP FEC Element
1264 CR-LDP Specification - 25 - Exp. August 1999
1266 A new FEC element is introduced in this specification to support CR-
1267 LSPs. The CRLDP FEC Element is an opaque FEC.
1269 FEC Element Type Value
1270 type name
1272 CRLSP 0x04 No value; i.e., 0 value octets;
1273 see below.
1275 CRLSP FEC Element
1276 To be used only in Messages of CR-LSPs.
1278 The CR-LSP FEC TLV encoding is as follows:
1280 0 1 2 3
1281 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
1282 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1283 |U|F| FEC(0x0100) | Length |
1284 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1285 | CR-LSP (4) | Reserved |
1286 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1288 U bit
1289 Unknown TLV bit. As defined in [LDP].
1291 F bit
1292 Forward unknown TLV bit. As defined in [LDP].
1294 Type
1295 FEC TLV type 0x0100
1297 Length
1298 Specifies the length of the value field in bytes.
1300 CR-LSP FEC Element Type
1301 0x04
1303 Reserved
1304 Zero on transmission. Ignored on receipt.
1306 4.11 Error subcodes
1308 In the processing described above, certain errors need to be reported
1309 as part of the Notification Message. This section defines the status
1310 codes for the errors described in this specification.
1312 CR-LDP Specification - 26 - Exp. August 1999
1314 Status Code Type
1315 -------------------------------------- ----------
1316 Bad Explicit Routing TLV Error 0x04000001
1317 Bad Strict Node Error 0x04000002
1318 Bad Loose Node Error 0x04000003
1319 Bad Initial ER-Hop Error 0x04000004
1320 Resource Unavailable 0x04000005
1321 Traffic Parameters Unavailable 0x04000006
1322 Setup abort 0x04000007
1324 5. Security
1326 Pre-emption has to be controlled by the MPLS domain.
1328 Resource reservation requires the LSRs to have an LSP admission
1329 control function.
1331 Normal routing can be bypassed by Traffic Engineered LSPs.
1333 6. Acknowledgments
1335 The messages used to signal the CRLSP setup are based on the work
1336 done by the [LDP] team. The Explicit Route object and procedures used
1337 in this specification are based on [ER].
1339 The authors would also like to acknowledge the careful review and
1340 comments of Ken Hayward, Greg Wright, Geetha Brown, Brian Williams,
1341 Paul Beaubien, Matthew Yuen, Liam Casey, and Ankur Anand.
1343 7. References
1345 [LDP] Andersson et al, "Label Distribution Protocol Specification"
1346 work in progress (draft-ietf-mpls-ldp-03), Feb. 1999.
1348 [ARCH] Rosen et al, "Multiprotocol Label Switching Architecture",
1349 work in progress (draft-ietf-mpls-arch-04), Feb. 1999.
1351 [FRAME] Callon et al, "Framework for Multiprotocol Label Switching",
1352 work in progress (draft-ietf-mpls-framework-02), November
1353 1997.
1355 [TER] Awduche et al, "Requirements for Traffic Engineering Over
1356 MPLS", work in progress (draft-ietf-mpls-traffic-eng-00),
1357 August 1998.
1359 [ER] Guerin et al, "Setting up Reservations on Explicit Paths
1360 using RSVP", work in progress (draft-guerin-expl-path-rsvp-
1361 01)
1362 November 1997.
1364 CR-LDP Specification - 27 - Exp. August 1999
1366 [VPN1] Heinanen et al, "MPLS Mappings of Generic VPN Mechanisms",
1367 work in progress (draft-heinanen-generic-vpn-mpls-00),
1368 August 1998.
1370 [VPN2] Jamieson et al, "MPLS VPN Architecture" work in progress
1371 (draft-jamieson-mpls-vpn-00), August 1998.
1373 [VPN3] T. Li, "CPE based VPNs using MPLS", work in progress (draft-
1374 li-mpls-vpn-00.txt), October 1998.
1376 [LDP-STATE] L. Wu, et. al., "LDP State Machine" work in progress
1377 (draft-ietf-mpls-ldp-state-00), Feb 1999.
1379 CR-LDP Specification - 28 - Exp. August 1999
1381 8. Author Information
1383 Osama S. Aboul-Magd Loa Andersson
1384 Nortel Networks Director Bay Architecture Lab,EMEA
1385 P O Box 3511 Station C Kungsgatan 34, PO Box 1788
1386 Ottawa, ON K1Y 4H7 111 97 Stockholm, Sweden
1387 Canada phone: +46 8 441 78 34
1388 phone: +1 613 763-5827 mobile +46 70 522 78 34
1389 osama@NortelNetworks.com loa_andersson@baynetworks.com
1391 Peter Ashwood-Smith Ross Callon
1392 Nortel Networks IronBridge Networks
1393 P O Box 3511 Station C 55 Hayden Avenue,
1394 Ottawa, ON K1Y 4H7 Lexington, MA 02173
1395 Canada Phone: +1-781-402-8017
1396 phone: +1 613 763-4534 rcallon@ironbridgenetworks.com
1397 petera@NortelNetworks.com
1399 Ram Dantu Paul Doolan
1400 Alcatel USA Inc. Ennovate Networks
1401 IP Competence Center 330 Codman Hill Rd
1402 1201 E. Campbell Road.,446-315 Marlborough MA 01719
1403 Richadson, TX USA., 75081-2206 Phone: 978-263-2002
1404 Phone: 972 996 2938 pdoolan@ennovatenetworks.com
1405 Fax: 972 996 5902
1406 ram.dantu@aud.alcatel.com
1408 Nancy Feldman Andre Fredette
1409 IBM Corp. Nortel Networks
1410 17 Skyline Drive 3 Federal Street
1411 Hawthorne NY 10532 Billerica, MA 01821
1412 Phone: 914-784-3254 fredette@baynetworks.com
1413 nkf@us.ibm.com
1415 Eric Gray Joel M. Halpern
1416 Lucent Technologies, Inc Newbridge Networks Inc.
1417 1600 Osgood St. 593 Herndon Parkway
1418 North Andover, MA 01847 Herndon, VA 20170
1419 Phone: 603-659-3386 phone: 1-703-736-5954
1420 ewgray@lucent.com jhalpern@newbridge.com
1422 Juha Heinanen Fiffi Hellstrand
1423 Telia Finland, Inc. Ericsson Telecom AB
1424 Myyrmaentie 2 S-126 25 STOCKHOLM
1425 01600 VANTAA Sweden
1426 Finland Tel: +46 8 719 4933
1427 Tel: +358 41 500 4808 etxfiff@etxb.ericsson.se
1428 jh@telia.fi
1430 CR-LDP Specification - 29 - Exp. August 1999
1432 Bilel Jamoussi Timothy E. Kilty
1433 Nortel Networks Northchurch Communications
1434 P O Box 3511 Station C 5 Corporate Drive,
1435 Ottawa, ON K1Y 4H7 Andover, MA 018110
1436 Canada phone: 978 691-4656
1437 phone: +1 613 765-4814 tkilty@northc.com
1438 jamoussi@NortelNetworks.com
1440 Andrew G. Malis Muckai K Girish
1441 Ascend Communications, Inc. SBC Technology Resources, Inc.
1442 1 Robbins Road 4698 Willow Road
1443 Westford, MA 01886 Pleasanton, CA 94588
1444 phone: 978 952-7414 Phone: (925) 598-1263
1445 fax: 978 392-2074 Fax: (925) 598-1321
1446 malis@ascend.com mgirish@tri.sbc.com
1448 Kenneth Sundell Pasi Vaananen
1449 Ericsson Nokia Telecommunications
1450 SE-126 25 Stockholm 3 Burlington Woods Drive, Suite 250
1451 Sweden Burlington, MA 01803
1452 kenneth.sundell@etx.ericsson.se Phone: +1-781-238-4981
1453 pasi.vaananen@ntc.nokia.com
1455 Tom Worster Liwen Wu
1456 General DataComm, Inc. Alcatel U.S.A
1457 5 Mount Royal Ave. 44983 Knoll Square
1458 Marlboro MA 01752 Ashburn, Va. 20147
1459 tom.worster@gdc.com USA
1460 Phone: (703) 724-2619
1461 FAX: (703) 724-2005
1462 liwen.wu@adn.alcatel.com
1464 CR-LDP Specification - 30 - Exp. August 1999
1466 Appendix A: CRLSP Establishment Examples
1468 A.1 Strict Explicit Route Example
1470 This appendix provides an example for the setup of a strictly routed
1471 CRLSP. In this example, each abstract node is represented by a
1472 specific node.
1474 The sample network used here is a four node network with two edge
1475 LSRs and two core LSRs as follows:
1477 a b c
1478 LSR1------LSR2------LSR3------LSR4
1480 LSR1 generates a Label Request Message as described in Section 3.1 of
1481 this draft and sends it to LSR2. This message includes the CR-TLV.
1483 The ER-TLV is composed by a vector of three ER-Hop TLVs .
1484 The ER-Hop TLVs used in this example are of type 0x0801 (IPv4 prefix)
1485 with a prefix length of 32. Hence, each ER-Hop TLV identifies a
1486 specific node as opposed to a group of nodes.
1488 At LSR2, the following processing of the ER-TLV per Section 4.8.1 of
1489 this draft takes place:
1491 1) The first hop is part of the abstract node LSR2. Therefore,
1492 the first step passes the test. Go to step 2.
1494 2) There is a second ER-Hop, . Go to step 3.
1496 3) LSR2 is not part of the abstract node described by the second
1497 ER-Hop . Go to Step 4.
1499 4) LSR2 determines that it is topologically adjacent to the
1500 abstract node described by the second ER-Hop . LSR2 selects a
1501 next hop (LSR3) which is the abstract node. LSR2 deletes the first
1502 ER-Hop from the ER-TLV which now becomes . Go to
1503 Section 4.8.2.
1505 At LSR2, the following processing of Section 4.8.2 takes place:
1507 Executing algorithm 4.8.1 did not result in the removal of the
1508 ER-TLV.
1510 Also, LSR2 is not a member of the abstract node described by the
1511 first ER-Hop .
1513 Finally, the first ER-Hop is a strict hop.
1515 Therefore, processing section 4.8.2 does not result in the
1516 insertion of new ER-Hops. The selection of the next hop has been
1518 CR-LDP Specification - 31 - Exp. August 1999
1520 already done is step 4 of Section 4.8.1 and the processing of the
1521 ER-TLV is completed at LSR2. In this case, the Label Request
1522 Message including the ER-TLV is progressed by LSR2 to LSR3.
1524 At LSR3, a similar processing to the ER-TLV takes place except that
1525 the incoming ER-TLV = and the outgoing ER-TLV is .
1527 At LSR4, the following processing of section 4.8.1 takes place:
1529 1) The first hop is part of the abstract node LSR4. Therefore,
1530 the first step passes the test. Go to step 2.
1532 2) There is no second ER-Hop, this indicates the end of the CRLSP.
1533 The ER-TLV is removed from the Label Request Message. Processing
1534 continues with Section 4.8.2.
1536 At LSR4, the following processing of Section 4.8.2 takes place:
1538 Executing algorithm 4.8.1 resulted in the removal of the ER-TLV.
1539 LSR4 does not add a new ER-TLV.
1541 Therefore, processing section 4.8.2 does not result in the
1542 insertion of new ER-Hops. This indicates the end of the CRLSP and
1543 the processing of the ER-TLV is completed at LSR4.
1545 At LSR4, processing of Section 3.2 is invoked. The first condition is
1546 satisfied (LSR4 is the egress end of the CRLSP and upstream mapping
1547 has been requested). Therefore, a Label Mapping Message is generated
1548 by LSR4 and sent to LSR3.
1550 At LSR3, the processing of Section 3.2 is invoked. The second
1551 condition is satisfied (LSR3 received a mapping from its downstream
1552 next hop LSR4 for a CRLSP for which an upstream request is still
1553 pending). Therefore, a Label Mapping Message is generated by LSR3 and
1554 sent to LSR2.
1556 At LSR2, a similar processing to LSR 3 takes place and a Label
1557 Mapping Message is sent back to LSR1 which completes the end-to-end
1558 CRLSP setup.
1560 A.2. Node Groups and Specific Nodes Example
1562 A request at an ingress LSR to setup a CRLSP might originate from a
1563 management system or an application, the details are implementation
1564 specific.
1566 The ingress LSR uses information provided by the management system or
1567 the application and possibly also information from the routing
1568 database to calculated the explicit route and to create the Label
1569 Request Message.
1571 CR-LDP Specification - 32 - Exp. August 1999
1573 The Label request message carries together with other necessary
1574 information a ER-TLV defining the explicitly routed path. In our
1575 example the list of hops in the ER-Hop TLV is supposed to contain an
1576 abstract node representing a group of nodes, an abstract node
1577 representing a specific node, another abstract node representing a
1578 group of nodes, and an abstract node representing a specific egress
1579 point.
1581 In--{Group 1}--{Specific A}--{Group 2}--{Specific Out: B}
1583 The ER-TLV contains four ER-Hop TLVs:
1585 1. An ER-Hop TLV that specifies a group of LSR valid for the first
1586 abstract node representing a group of nodes (Group 1).
1588 2. An ER-Hop TLV that indicates the specific node (Node A).
1590 3. An ER-Hop TLV that specifies a group of LSRs valid for the
1591 second abstract node representing a group of nodes (Group 2).
1593 4. An ER-Hop TLV that indicates the specific egress point for the
1594 CRLSP (Node B).
1596 All the ER-Hop TLVs are strictly routed nodes.
1598 The setup procedure for this CRLSP works as follows:
1600 1. The ingress node sends the Label Request Message to a node that
1601 is a member the group of nodes indicated in the first ER-Hop TLV,
1602 following normal routing for the specific node (A).
1604 2. The node that receives the message identifies itself as part of
1605 the group indicated in the first ER-Hop TLV, and that it is not
1606 the specific node (A) in the second. Further it realizes that the
1607 specific node (A) is not one of its next hops.
1609 3. It keeps the ER-Hop TLVs intact and sends a Label Request
1610 Message to a node that is part of the group indicated in the first
1611 ER-Hop TLV (Group 1), following normal routing for the specific
1612 node (A).
1614 4. The node that receives the message identifies itself as part of
1615 the group indicated in the first ER-Hop TLV, and that it is not
1616 the specific node (A) in the second ER-Hop TLV. Further it
1617 realizes that the specific node (A) is one of its next hops.
1619 5. It removes the first ER-Hop TLVs and sends a Label Request
1620 Message to the specific node (A).
1622 6. The specific node (A) recognizes itself in the first ER-Hop
1623 TLV. Removes the specific ER-Hop TLV.
1625 CR-LDP Specification - 33 - Exp. August 1999
1627 7. It sends a Label Request Message to a node that is a member of
1628 the group (Group 2) indicated in the ER-Hop TLV.
1630 8. The node that receives the message identifies itself as part of
1631 the group indicated in the first ER-Hop TLV, further it realizes
1632 that the specific egress node (B) is one of its next hops.
1634 9. It sends a Label Request Message to the specific egress node
1635 (B).
1637 10. The specific egress node (B) recognizes itself as the egress
1638 for the CRLSP, it returns a Label Mapping Message, that will
1639 traverse the same path as the Label Request Message in the
1640 opposite direction.
1642 CR-LDP Specification - 34 - Exp. August 1999
1644 Appendix B. QoS Service Examples
1646 B.1 Service Examples
1648 Construction of an end-to-end service is the result of the rules
1649 enforced at the edge and the treatment that packets receive at the
1650 network nodes. The rules define the traffic conditioning actions that
1651 are implemented at the edge and they include policing with pass,
1652 mark, and drop capabilities. The edge rules are expected to be
1653 defined by the mutual agreements between the service providers and
1654 their customers and they will constitute an essential part of the
1655 SLA. Therefore edge rules are not included in the signaling protocol.
1657 Packets treatment at a network node is usually referred to as the
1658 local behavior. Local behavior could be specified in many ways. One
1659 example for local behavior specification is the service frequency
1660 introduced in section 4.3.2.1., together with the resource
1661 reservation rules implemented at the nodes.
1663 Edge rules and local behaviors can be viewed as the main building
1664 blocks for the end-to-end service construction. The following table
1665 illustrates the applicability of the building block approach for
1666 constructing different services including those defined for ATM.
1668 Service PDR PBS CDR CBS EBS Service Conditioning
1669 Examples Frequency Action
1670 ---------------------------------------------------------------------------
1672 DS S S =PDR =PBS 0 Frequent drop>PDR
1674 TS S S S S 0 Unspecified drop>PDR,PBS
1675 mark>CDR,CBS
1677 BE inf inf inf inf 0 Unspecified -
1679 FRS S S CIR ~B_C ~B_E Unspecified drop>PDR,PBS
1680 mark>CDR,CBS,EBS
1682 ATM-CBR PCR CDVT =PCR =CDVT 0 VeryFrequent drop>PCR
1684 ATM-VBR.3(rt) PCR CDVT SCR MBS 0 Frequent drop>PCR
1685 mark>SCR,MBS
1687 ATM-VBR.3(nrt) PCR CDVT SCR MBS 0 Unspecified drop>PCR
1688 mark>SCR,MBS
1690 ATM-UBR PCR CDVT - - 0 Unspecified drop>PCR
1692 ATM-GFR.1 PCR CDVT MCR MBS 0 Unspecified drop>PCR
1694 CR-LDP Specification - 35 - Exp. August 1999
1696 ATM-GFR.2 PCR CDVT MCR MBS 0 Unspecified drop>PCR
1697 mark>MCR,MFS
1699 int-serv-CL p m r b 0 Frequent drop>p
1700 drop>r,b
1702 S= User specified
1704 In the above table, the DS refers to a delay sensitive service where
1705 the network commits to deliver with high probability user datagrams
1706 at a rate of PDR with minimum delay and delay requirements. Datagrams
1707 in excess of PDR will be discarded.
1709 The TS refers to a generic throughput sensitive service where the
1710 network commit to deliver with high probability user datagrams at a
1711 rate of at least CDR. The user may transmit at a rate higher than CDR
1712 but datagrams in excess of CDR would have a lower probability of
1713 being delivered.
1715 The BE is the best effort service and it implies that there are no
1716 expected service guarantees from the network.
1718 B.2. Establishing CR-LSP Supporting Real-Time Applications
1720 In this scenario the customer needs to establish an LSP for
1721 supporting real-time applications such voice and video. The Delay-
1722 sensitive (DS) service is requested in this case.
1724 The first step is the specification of the traffic parameters in the
1725 signaling message. The two parameters of interest to the DS service
1726 are the PDR and the PBS and their values are specified by the user
1727 based on his requirements. Since all the traffic parameters are
1728 included in the signaling message, appropriate values must be
1729 assigned to all of them. For DS service, the CDR and the CBS values
1730 are set equal to the PDR and the PBS respectively. An indication of
1731 whether the parameter values are subject to negotiation is flagged.
1733 The transport characteristics of the DS service requires that
1734 Frequent frequency to be requested to reflect the real-time delay
1735 requirements of the service.
1737 In addition to the transport characteristics, both the network
1738 provider and the customer need to agree on the actions enforced at
1739 the edge. The specification of those actions is expected to be a part
1740 of the service level agreement (SLA) negotiation and is not included
1741 in the signaling protocol. For DS service, the edge action is to drop
1742 packets that exceed the PDR and the PBS specifications.
1744 The signaling message will be sent in the direction of the ER path
1745 and the LSP is established following the normal LDP procedures. Each
1747 CR-LDP Specification - 36 - Exp. August 1999
1749 LSR applies its admission control rules. If sufficient resources are
1750 not available and the parameter values are subject to negotiation,
1751 then the LSR could negotiate down either the PDR, the PBS, or both.
1752 The new parameters values are echoed back in the Label Mapping
1753 Message. LSRs might need to re-adjust their resource reservations
1754 based on the new traffic parameter values.
1756 B.3. Establishing CR-LSP Supporting Delay Insensitive Applications
1758 In this example we assume that a throughput sensitive (TS) service is
1759 requested. For resource allocation the user assigns values for PDR,
1760 PBS, CDR, and CBS. The negotiation flag is set if the traffic
1761 parameters are subject to negotiation.
1763 Since the service is delay insensitive by definition, the Unspecified
1764 frequency is signaled to indicate that the service frequency is not
1765 an issue.
1767 Similar to the previous example, the edge actions are not subject for
1768 signaling and are specified in the service level agreement between
1769 the user and the network provider.
1771 For TS service, the edge rules might include marking to indicate high
1772 discard precedence values for all packets that exceed CDR and the
1773 CBS. The edge rules will also include dropping of packets that are do
1774 not conform to either PDR and PBS.
1776 Each LSR of the LSP is expected to run its admission control rules
1777 and negotiate traffic parameters down if sufficient resources do not
1778 exist. The new parameters values are echoed back in the Label Mapping
1779 Message. LSRs might need to re-adjust their resources based on the
1780 new traffic parameter values.