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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'Ta' is mentioned on line 356, but not defined == Missing Reference: 'Tb' is mentioned on line 356, but not defined == Missing Reference: 'TBD1' is mentioned on line 579, but not defined == Missing Reference: 'TBD2' is mentioned on line 689, but not defined == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-13 == Outdated reference: A later version (-10) exists of draft-litkowski-pce-state-sync-07 Summary: 0 errors (**), 0 flaws (~~), 7 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group H. Chen, Ed. 3 Internet-Draft Futurewei 4 Intended status: Standards Track Y. Zhuang, Ed. 5 Expires: January 13, 2021 Q. Wu 6 Huawei 7 D. Ceccarelli 8 Ericsson 9 July 12, 2020 11 PCEP Extensions for LSP scheduling with stateful PCE 12 draft-ietf-pce-stateful-pce-lsp-scheduling-21 14 Abstract 16 This document defines a set of extensions needed to the stateful Path 17 Computation Element (PCE) communication Protocol (PCEP), so as to 18 enable Labeled Switched Path (LSP) scheduling for path computation 19 and LSP setup/deletion based on the actual network resource usage and 20 the duration of a traffic service in a centralized network 21 environment as stated in RFC 8413. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at https://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on January 13, 2021. 40 Copyright Notice 42 Copyright (c) 2020 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (https://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Conventions used in this document . . . . . . . . . . . . . . 4 59 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 60 3. Motivation and Objectives . . . . . . . . . . . . . . . . . . 5 61 4. Procedures and Mechanisms . . . . . . . . . . . . . . . . . . 5 62 4.1. LSP Scheduling Overview . . . . . . . . . . . . . . . . . 5 63 4.2. Support of LSP Scheduling . . . . . . . . . . . . . . . . 7 64 4.2.1. LSP Scheduling . . . . . . . . . . . . . . . . . . . 7 65 4.2.2. Periodical LSP Scheduling . . . . . . . . . . . . . . 7 66 4.3. Scheduled LSP creation . . . . . . . . . . . . . . . . . 9 67 4.4. Scheduled LSP Modifications . . . . . . . . . . . . . . . 10 68 4.5. Scheduled LSP activation and deletion . . . . . . . . . . 11 69 5. PCEP Objects and TLVs . . . . . . . . . . . . . . . . . . . . 11 70 5.1. Stateful PCE Capability TLV . . . . . . . . . . . . . . . 11 71 5.2. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 12 72 5.2.1. SCHED-LSP-ATTRIBUTE TLV . . . . . . . . . . . . . . . 12 73 5.2.2. SCHED-PD-LSP-ATTRIBUTE TLV . . . . . . . . . . . . . 15 74 6. The PCEP Messages . . . . . . . . . . . . . . . . . . . . . . 16 75 6.1. The PCRpt Message . . . . . . . . . . . . . . . . . . . . 16 76 6.2. The PCUpd Message . . . . . . . . . . . . . . . . . . . . 16 77 6.3. The PCInitiate Message . . . . . . . . . . . . . . . . . 17 78 6.4. The PCReq message . . . . . . . . . . . . . . . . . . . . 17 79 6.5. The PCRep Message . . . . . . . . . . . . . . . . . . . . 17 80 6.6. The PCErr Message . . . . . . . . . . . . . . . . . . . . 17 81 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 18 82 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 83 9. Manageability Consideration . . . . . . . . . . . . . . . . . 19 84 9.1. Control of Function and Policy . . . . . . . . . . . . . 19 85 9.2. Information and Data Models . . . . . . . . . . . . . . . 19 86 9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 19 87 9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 20 88 9.5. Requirements On Other Protocols . . . . . . . . . . . . . 20 89 9.6. Impact On Network Operations . . . . . . . . . . . . . . 20 90 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 91 10.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 20 92 10.1.1. Opt Field in SCHED-PD-LSP-ATTRIBUTE TLV . . . . . . 20 93 10.1.2. Schedule TLVs Flag Field . . . . . . . . . . . . . . 21 94 10.2. STATEFUL-PCE-CAPABILITY TLV Flag field . . . . . . . . . 21 95 10.3. PCEP-Error Object . . . . . . . . . . . . . . . . . . . 21 96 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 22 97 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 98 12.1. Normative References . . . . . . . . . . . . . . . . . . 22 99 12.2. Informative References . . . . . . . . . . . . . . . . . 23 100 Appendix A. Contributors Addresses . . . . . . . . . . . . . . . 24 101 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 103 1. Introduction 105 The Path Computation Element Protocol (PCEP) defined in [RFC5440] is 106 used between a Path Computation Element (PCE) and a Path Computation 107 Client (PCC) (or other PCE) to enable path computation of Multi- 108 protocol Label Switching (MPLS) Traffic Engineering Label Switched 109 Paths (TE LSPs). 111 [RFC8231] describes a set of extensions to PCEP to provide stateful 112 control. A stateful PCE has access to not only the information 113 carried by the network's Interior Gateway Protocol (IGP) but also the 114 set of active paths and their reserved resources for its 115 computations. The additional state allows the PCE to compute 116 constrained paths while considering individual LSPs and their 117 interactions. 119 Traditionally, the usage and allocation of network resources, 120 especially bandwidth, can be supported by a Network Management System 121 (NMS) operation such as path pre-establishment. However, this does 122 not provide efficient usage of network resources. The established 123 paths reserve the resources forever, which can not be used by other 124 services even when they are not used for transporting any service. 125 [RFC8413] then provides a framework that describes and discusses the 126 problem, and defines an appropriate architecture for the scheduled 127 reservation of TE resources. 129 The scheduled reservation of TE resources allows network operators to 130 reserve resources in advance according to the agreements with their 131 customers, and allows them to transmit data about scheduling such as 132 a specified start time and duration, for example for a scheduled bulk 133 data replication between data centers. It enables the activation of 134 bandwidth usage at the time the service is really being used while 135 letting other services use it when this service is not using it. The 136 requirement of scheduled LSP provision is mentioned in [RFC8231] and 137 [RFC7399]. A solution for providing more efficient network resource 138 usage for traffic engineering is desired. Also, for deterministic 139 networks [I-D.ietf-detnet-architecture], the scheduled LSP or 140 temporal LSP can provide a better network resource usage for 141 guaranteed links. This idea can also be applied in segment routing 142 [RFC8402] to schedule the network resources over the whole network in 143 a centralized manner as well. 145 With this in mind, this document defines a set of extensions needed 146 to PCEP used for stateful PCEs so as to enable LSP scheduling for 147 path computation and LSP setup/deletion based on the actual network 148 resource usage duration of a traffic service. A scheduled LSP is 149 characterized by a starting time and a duration. When the end of the 150 LSP life is reached, it is deleted to free up the resources for other 151 LSPs (scheduled or not). 153 2. Conventions used in this document 155 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 156 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 157 "OPTIONAL" in this document are to be interpreted as described in BCP 158 14 [RFC2119] [RFC8174] when, and only when, they appear in all 159 capitals, as shown here. 161 2.1. Terminology 163 The following terminologies are re-used from existing PCE documents. 165 o Active Stateful PCE [RFC8231]; 167 o Delegation [RFC8231]; 169 o PCE-Initiated LSP [RFC8281]; 171 o PCC [RFC5440], [RFC8231]; 173 o PCE [RFC5440], [RFC8231]; 175 o TE LSP [RFC5440], [RFC8231]; 177 o TED [RFC5440], [RFC8231]; 179 o LSP-DB [RFC8231]; 181 In addition, this document defines the following terminologies. 183 Scheduled TE LSP (or Scheduled LSP for short): an LSP with the 184 scheduling attributes, that carries traffic flow demand at a 185 starting time and lasts for a certain duration (or from a starting 186 time to an ending time, where the ending time is the starting time 187 plus the duration). A scheduled LSP is also called a temporal 188 LSP. The PCE operates path computation per LSP availability for 189 the required time and duration. 191 Scheduled LSP-DB: a database of scheduled LSPs. 193 Scheduled TED: Traffic engineering database with the awareness of 194 scheduled resources for TE. This database is generated by the PCE 195 from the information in TED and scheduled LSP-DB and allows 196 knowing, at any time, the amount of available resources (does not 197 include failures in the future). 199 Starting time (start-time): This value indicates when the scheduled 200 LSP is used and the corresponding LSP must be setup and active. 201 In other time (i.e., before the starting time or after the 202 starting time plus Duration), the LSP can be inactive to include 203 the possibility of the resources being used by other services. 205 Duration: This value indicates the time duration that the LSP is 206 undertaken by a traffic flow and the corresponding LSP must be 207 setup and active. At the end of which, the LSP is torn down and 208 removed from the database. 210 3. Motivation and Objectives 212 A stateful PCE [RFC8231] can support better efficiency by using LSP 213 scheduling described in the use case of [RFC8051]. This requires the 214 PCE to maintain the scheduled LSPs and their associated resource 215 usage, e.g. bandwidth for Packet-switched network, as well as have 216 the ability to trigger signaling for the LSP setup/tear-down at the 217 correct time. 219 Note that existing configuration tools can be used for LSP 220 scheduling, but as highlighted in section 3.1.3 of [RFC8231] as well 221 as discussions in [RFC8413], doing this as a part of PCEP in a 222 centralized manner, has obvious advantages. 224 This document provides a set of extensions to PCEP to enable LSP 225 scheduling for LSP creation/deletion under the stateful control of a 226 PCE and according to traffic service requests from customers, so as 227 to improve the usage of network resources. 229 4. Procedures and Mechanisms 231 4.1. LSP Scheduling Overview 233 The LSP scheduling allows PCEs and PCCs to provide scheduled LSP for 234 customers' traffic services at its actual usage time, so as to 235 improve the network resource efficient utilization. 237 For stateful PCE supporting LSP scheduling, there are two types of 238 LSP databases used in this document. One is the LSP-DB defined in 239 PCEP [RFC8231], while the other is the scheduled LSP database (SLSP- 240 DB, see section 6). The SLSP-DB records scheduled LSPs and is used 241 in conjunction with the TED and LSP-DB. Note that the two types of 242 LSP databases can be implemented in one physical database or two 243 different databases. This is an implementation matter and this 244 document does not state any preference. 246 Furthermore, a scheduled TED can be generated from the scheduled LSP- 247 DB, LSP-DB and TED to indicate the network links and nodes with 248 resource availability information for now and future. The scheduled 249 TED should be maintained by all PCEs within the network environment. 251 In case of implementing PCC-initiated scheduled LSPs, before a PCC 252 delegates a scheduled LSP, it MAY use the PCReq/PCRep messages to 253 learn the path for the scheduled LSP. A PCC MUST delegate a 254 scheduled LSP with information of its scheduling parameters, 255 including the starting time and the duration using PCRpt message. 256 Since the LSP is not yet signaled, at the time of delegation the LSP 257 would be in down state. Upon receiving the delegation of the 258 scheduled LSP, a stateful PCE SHALL check the scheduled TED for the 259 network resource availability on network nodes and compute a path for 260 the LSP with the scheduling information and update to the PCC as per 261 the active stateful PCE techniques [RFC8231]. 263 Note that the active stateful PCE can update to the PCC with the path 264 for the scheduled LSP at any time. However, the PCC should not 265 signal the LSP over the path on receiving these messages since the 266 path is not active yet; PCC signals the LSP at the starting time. 268 For a multiple PCE environment, a PCE MUST synchronize to other PCEs 269 within the network, so as to keep their scheduling information 270 synchronized. There are many ways that this could be achieved: one 271 such mechanism is described in [I-D.litkowski-pce-state-sync]. Which 272 way is used to achieve this is out of scope for this document. The 273 scheduled TED can be determined from the synchronized SLSP-DB. The 274 PCE with delegation for the scheduled LSP would report the scheduled 275 LSP to other PCEs, any future update to the scheduled LSP is also 276 updated to other PCEs. This way the state of all scheduled LSPs are 277 synchronized among the PCEs. [RFC7399] discusses some 278 synchronization issues and considerations, that are also applicable 279 to the scheduled databases. 281 The scheduled LSP can also be initiated by PCE itself. In case of 282 implementing PCE-initiated scheduled LSP, the stateful PCE shall 283 check the network resource availability for the traffic and computes 284 a path for the scheduled LSP and initiate a scheduled LSP at the PCC 285 and synchronize the scheduled LSP to other PCEs. Note that, the PCC 286 could be notified immediately or at the starting time of the 287 scheduled LSP based on the local policy. For the former SCHED-LSP- 288 ATTRIBUTE TLV (see Section 5.2.1) MUST be included in the message 289 where as for the latter SCHED-LSP-ATTRIBUTE TLV SHOULD NOT be 290 included. Either way the synchronization to other PCEs should be 291 done when the scheduled LSP is created. 293 In both modes, for activation of scheduled LSPs, the PCC could 294 initiate the setup of scheduled LSP at the start time by itself or 295 wait for the PCE to update the PCC to initiate the setup of LSP. 296 Similarly on scheduled usage expires, the PCC could initiate the 297 removal by itself or wait for the PCE to request the removal of the 298 LSP. This is based on the Flag set in SCHED-LSP-ATTRIBUTE TLV. 300 4.2. Support of LSP Scheduling 302 4.2.1. LSP Scheduling 304 For a scheduled LSP, a user configures it with an arbitrary 305 scheduling duration from time Ta to time Tb, which may be represented 306 as [Ta, Tb]. 308 When an LSP is configured with arbitrary scheduling duration [Ta, 309 Tb], a path satisfying the constraints for the LSP in the scheduling 310 duration is computed and the LSP along the path is set up to carry 311 traffic from time Ta to time Tb. 313 4.2.2. Periodical LSP Scheduling 315 In addition to LSP Scheduling at an arbitrary time period, there are 316 also periodical LSP Scheduling. 318 A periodical LSP Scheduling means an LSP has multiple time intervals 319 and the LSP is set up to carry traffic in every time interval. It 320 has a scheduling duration such as [Ta, Tb], a number of repeats such 321 as 10 (repeats 10 times), and a repeat cycle/time interval such as a 322 week (repeats every week). The scheduling interval: "[Ta, Tb] 323 repeats n times with repeat cycle C" represents n+1 scheduling 324 intervals as follows: 326 [Ta, Tb], [Ta+C, Tb+C], [Ta+2C, Tb+2C], ..., [Ta+nC, Tb+nC] 328 When an LSP is configured with a scheduling interval such as "[Ta, 329 Tb] repeats 10 times with a repeat cycle a week" (representing 11 330 scheduling intervals), a path satisfying the constraints for the LSP 331 in every interval represented by the periodical scheduling interval 332 is computed once. And then the LSP along the path is set up to carry 333 traffic in each of the scheduling intervals. If there is no path 334 satisfying the constraints for some of the intervals, the LSP will 335 not be set up at all. It SHOULD generate a PCEP Error (PCErr) with 336 Error-type = 29 (Path computation failure) and Error-value = TBD7 337 (Constraints could not be met for some intervals). 339 4.2.2.1. Elastic Time LSP Scheduling 341 In addition to the basic LSP scheduling at an arbitrary time period, 342 another option is elastic time intervals, which is represented as 343 within -P and Q, where P and Q is an amount of time such as 300 344 seconds. P is called elastic range lower bound and Q is called 345 elastic range upper bound. 347 For a simple time interval such as [Ta, Tb] with an elastic range, 348 elastic time interval: "[Ta, Tb] within -P and Q" means a time period 349 from (Ta+X) to (Tb+X), where -P <= X <= Q. Note that both Ta and Tb 350 are shifted by the same 'X'. 352 When an LSP is configured with elastic time interval "[Ta, Tb] within 353 -P and Q", a path is computed such that the path satisfies the 354 constraints for the LSP in the time period from (Ta+Xv) to (Tb+Xv) 355 and |Xv| is the minimum value for Xv from -P to Q. That is, [Ta+Xv, 356 Tb+Xv] is the time interval closest to time interval [Ta, Tb] within 357 the elastic range. The LSP along the path is set up to carry traffic 358 in the time period from (Ta+Xv) to (Tb+Xv). 360 Similarly, for a recurrent time interval with an elastic range, 361 elastic time interval: "[Ta, Tb] repeats n times with repeat cycle C 362 within -P and Q" represents n+1 simple elastic time intervals as 363 follows: 365 [Ta+X0, Tb+X0], [Ta+C+X1, Tb+C+X1], ..., [Ta+nC+Xn, Tb+nC+Xn] 366 where -P <= Xi <= Q, i = 0, 1, 2, ..., n. 368 If a user wants to keep the same repeat cycle between any two 369 adjacent time intervals, elastic time interval: "[Ta, Tb] repeats n 370 times with repeat cycle C within -P and Q SYNC" may be used, which 371 represents n+1 simple elastic time intervals as follows: 373 [Ta+X, Tb+X], [Ta+C+X, Tb+C+X], ..., [Ta+nC+X, Tb+nC+X] 374 where -P <= X <= Q. 376 4.2.2.2. Grace Periods 378 Besides the stated time scheduling, a user may want to have some 379 grace periods (short for graceful time periods) for each or some of 380 the time intervals for the LSP. Two grace periods may be configured 381 for a time interval. One is the grace period before the time 382 interval, called grace-before, which extends the lifetime of the LSP 383 for grace-before (such as 30 seconds) before the time interval. The 384 other is the one after the time interval, called grace-after, which 385 extends the lifetime of the LSP for grace-after (such as 60 seconds) 386 after the time interval. 388 When an LSP is configured with a simple time interval such as [Ta, 389 Tb] with grace periods such as grace-before GB and grace-after GA, a 390 path is computed such that the path satisfies the constraints for the 391 LSP in the time period from Ta to Tb. The LSP along the path is set 392 up to carry traffic in the time period from (Ta-GB) to (Tb+GA). 393 During grace periods from (Ta-GB) to Ta and from Tb to (Tb+GA), the 394 LSP is up to carry traffic (maybe in best effort). 396 4.3. Scheduled LSP creation 398 In order to realize PCC-Initiated scheduled LSPs in a centralized 399 network environment, a PCC has to separate the setup of an LSP into 400 two steps. The first step is to request/delegate and get an LSP but 401 not signal it over the network. The second step is to signal the 402 scheduled LSP over the LSRs (Label Switching Router) at its starting 403 time. 405 For PCC-Initiated scheduled LSPs, a PCC can delegate the scheduled 406 LSP by sending a path computation report (PCRpt) message by including 407 its demanded resources with the scheduling information to a stateful 408 PCE. Note the PCC MAY use the PCReq/PCRep with scheduling 409 information before delegating. 411 Upon receiving the delegation via PCRpt message, the stateful PCE 412 computes the path for the scheduled LSP per its starting time and 413 duration based on the network resource availability stored in 414 scheduled TED (see Section 4.1). 416 The stateful PCE will send a PCUpd message with the scheduled path 417 information as well as the scheduled resource information for the 418 scheduled LSP to the PCC. The PCE SHOULD add the scheduled LSP into 419 its scheduled LSP-DB and update its scheduled TED. 421 For PCE-Initiated Scheduled LSP, the stateful PCE can compute a path 422 for the scheduled LSP per requests from network management systems 423 automatically based on the network resource availability in the 424 scheduled TED, send a PCInitiate message with the path information 425 back to the PCC. Based on the local policy, the PCInitiate message 426 could be sent immediately to ask PCC to create a scheduled LSP (as 427 per this document) or the PCInitiate message could be sent at the 428 start time to the PCC to create a normal LSP (as per [RFC8281]). 430 For both PCC-Initiated and PCE-Initiated Scheduled LSPs: 432 o The stateful PCE is required to update its local scheduled LSP-DB 433 and scheduled TED with the scheduled LSP. Besides, it shall send 434 a PCRpt message with the scheduled LSP to other PCEs within the 435 network, so as to achieve the scheduling traffic engineering 436 information synchronization. 438 o Upon receiving the PCUpd message or PCInitiate message for the 439 scheduled LSP from PCEs with a found path, the PCC knows that it 440 is a scheduled path for the LSP and does not trigger signaling for 441 the LSP setup on LSRs immediately. 443 o The stateful PCE can update the Scheduled LSP parameters on any 444 network events using the PCUpd message to PCC. These changes are 445 also synchronized to other PCEs. 447 o Based on the configuration (and the C flag in scheduled TLVs), 448 when it is time (i.e., at the start time) for the LSP to be set 449 up, either the PCC triggers the LSP to be signaled or the 450 delegated PCE sends a PCUpd message to the head end LSR providing 451 the updated path to be signaled (with A flag set to indicate LSP 452 activation). 454 4.4. Scheduled LSP Modifications 456 After a scheduled LSP is configured, a user may change its parameters 457 including the requested time as well as the bandwidth. 459 In PCC-Initiated case, the PCC can send a PCRpt message for the 460 scheduled LSP with updated parameters as well as scheduled 461 information included in the SCHED-LSP-ATTRIBUTE TLV (see 462 Section 5.2.1) or SCHED-PD-LSP-ATTRIBUTE TLV (see Section 5.2.2) 463 carried in the LSP Object. The PCE would take the updated resources 464 and schedule into considerations and update the new path for the 465 scheduled LSP to the PCC as well as synchronize to other PCEs in the 466 network. In case path cannot be set based on new requirements, the 467 previous LSP will not be impacted and the same should be conveyed by 468 the use of empty ERO in the PCEP messages. 470 In PCE-Initiated case, the Stateful PCE would recompute the path 471 based on updated parameters as well as scheduled information. In 472 case it has already conveyed to the PCC this information by sending a 473 PCInitiate message, it should update the path and other scheduling 474 and resource information by sending a PCUpd message. 476 4.5. Scheduled LSP activation and deletion 478 In PCC-Initiated case, based on the configuration (and the C flag in 479 scheduled TLVs), when it is time (i.e., at the start time) for the 480 LSP to be set up, either the PCC triggers the LSP to be signaled or 481 the delegated PCE sends a PCUpd message to the head end LSR providing 482 the updated path to be signaled (with A flag set to indicate LSP 483 activation). The PCC would report the status of the active LSP as 484 per the procedures in [RFC8231] and at this time the LSP MUST be 485 considered as part of the LSP-DB. The A flag MUST be set in the 486 scheduled TLVs to indicate that the LSP is active now. After the 487 scheduled duration expires, based on the C flag, the PCC triggers the 488 LSP deletion on itself or the delegated PCE sends a PCUpd message to 489 the PCC to delete the LSP as per the procedures in [RFC8231]. 491 In PCE-Initiated case, based on the local policy, if the scheduled 492 LSP is already conveyed to the PCC at the time of creation, the 493 handling of LSP activation and deletion is handled in the same way as 494 PCC-Initiated case as per the setting of C flag. Otherwise, the PCE 495 would send the PCInitiate message at the start time to the PCC to 496 create a normal LSP without the scheduled TLVs and remove the LSP 497 after the duration expires as per [RFC8281]. 499 5. PCEP Objects and TLVs 501 5.1. Stateful PCE Capability TLV 503 After a PCEP session has been established, a PCC and a PCE indicates 504 its ability to support LSP scheduling during the PCEP session 505 establishment phase. For a multiple-PCE environment, the PCEs should 506 also establish PCEP session and indicate its ability to support LSP 507 scheduling among PCEP peers. The Open Object in the Open message 508 contains the STATEFUL-PCE-CAPABILITY TLV defined in [RFC8231]. Note 509 that the STATEFUL-PCE-CAPABILITY TLV is defined in [RFC8231] and 510 updated in [RFC8281] and [RFC8232]". In this document, we define a 511 new flag bit B (SCHED-LSP-CAPABLITY) flag for the STATEFUL-PCE- 512 CAPABILITY TLV to indicate the support of LSP scheduling and another 513 flag bit PD (PD-LSP-CAPABLITY) to indicate the support of LSP 514 periodical scheduling. 516 B (LSP-SCHEDULING-CAPABILITY - 1 bit) [Bit Position - TBD3]: If set 517 to 1 by a PCC, the B Flag indicates that the PCC allows LSP 518 scheduling; if set to 1 by a PCE, the B Flag indicates that the 519 PCE is capable of LSP scheduling. The B bit MUST be set by both 520 PCEP peers in order to support LSP scheduling for path 521 computation. 523 PD (PD-LSP-CAPABLITY - 1 bit): [Bit Position - TBD4] If set to 1 by 524 a PCC, the PD Flag indicates that the PCC allows LSP scheduling 525 periodically; if set to 1 by a PCE, the PD Flag indicates that the 526 PCE is capable of periodical LSP scheduling. The PD bit MUST be 527 set by both PCEP peers in order to support periodical LSP 528 scheduling for path computation. Setting PD bit requires setting 529 B bit as specified in 5.2.2. Without setting B which indicates 530 basic capability of LSP scheduling, the advanced capability 531 indicated by Setting PD bit (capability of periodical LSP 532 scheduling) could not be achieved. 534 5.2. LSP Object 536 The LSP object is defined in [RFC8231]. This document adds an 537 optional SCHED-LSP-ATTRIBUTE TLV for normal LSP scheduling and an 538 optional SCHED-PD-LSP-ATTRIBUTE TLV for periodical LSP scheduling. 540 The presence of SCHED-LSP-ATTRIBUTE TLV in the LSP object indicates 541 that this LSP is requesting scheduled parameters while the SCHED-PD- 542 LSP-ATTRIBUTE TLV indicates that this scheduled LSP is periodical. 543 The scheduled LSP attribute TLV MUST be present in LSP Object for 544 each scheduled LSP carried in the PCEP messages. For periodical 545 LSPs, the SCHED-PD-LSP-ATTRIBUTE TLV can be used in LSP Object for 546 each periodic scheduled LSP carried in the PCEP messages. 548 Only one of these TLV SHOULD be present in the LSP object. In case 549 more than one scheduling TLV is found, the first instance is 550 processed and others ignored. 552 5.2.1. SCHED-LSP-ATTRIBUTE TLV 554 The SCHED-LSP-ATTRIBUTE TLV MAY be included as an optional TLV within 555 the LSP object for LSP scheduling for the requesting traffic service. 557 This TLV MUST NOT be included unless both PCEP peers have set the B 558 (LSP-SCHEDULING-CAPABILITY bit) in STATEFUL-PCE-CAPABILITY TLV 559 carried in the Open message. 561 The format of the SCHED-LSP-ATTRIBUTE TLV is shown in Figure 1. 563 0 1 2 3 564 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 1 565 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 566 | Type (TBD1) | Length | 567 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 568 | Flags |R|C|A|G| Reserved (0) | 569 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 570 | Start-Time | 571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 | Duration | 573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 574 | GrB / Elastic-Lower-Bound | GrA / Elastic-Upper-Bound | 575 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 577 Figure 1: SCHED-LSP-ATTRIBUTE TLV 579 The type of the TLV is [TBD1] and the TLV has a fixed length of 20 580 octets. 582 The fields in the format are: 584 Flags (8 bits): Following flags are defined in this document 586 R (1 bit): Set to 1 to indicate the Start-Time is a relative 587 time, which is the number of seconds from the current time. It 588 is necessary to synchronize the clocks of the PCEs and PCCs 589 when relative time is used. When the transmission delay from a 590 PCE or PCC to another PCE or PCC is too big such as greater 591 than 1 second, the scheduling interval represented is not 592 accurate if the delay is not considered. Set to 0 to indicate 593 that the 32-bit Start-Time is an absolute time, which is the 594 number of seconds since the epoch. The epoch is 1 January 1970 595 at 00:00 UTC. It wraps around every 2^32 seconds, which is 596 roughly 136 years. The next wraparound will occur in the year 597 2106. After the wraparound, the value of the 32-bit Start-Time 598 is the number of seconds from the time of wraparound because 599 the Start-Time is always a future time. Before the wraparound 600 and within a constant RANGE-START-TIME to reach the wraparound, 601 if the time at which the LSP is to be activated is after the 602 wraparound, the time is represented by the number of seconds 603 from the time of wraparound in the 32-bit Start-Time. RANGE- 604 START-TIME = 2*365*86400 seconds (about 2 years). 606 C (1 bit): Set to 1 to indicate the PCC is responsible to setup 607 and remove the scheduled LSP based on the Start-Time and 608 duration. 610 A (1 bit): Set to 1 to indicate the scheduled LSP has been 611 activated and should be considered as part of LSP-DB (instead 612 of Scheduled LSP-DB). 614 G (1 bit): Set to 1 to indicate the Grace period is included; set 615 to 0 indicate the elastic range is included. 617 Reserved (24 bits): This field MUST be set to zero on transmission 618 and MUST be ignored on receipt. 620 Start-Time (32 bits): This value in seconds, indicates when the 621 scheduled LSP is used to carry traffic and the corresponding LSP 622 must be setup and activated. Value of 0 MUST NOT be used in 623 Start-Time. Note that the transmission delay SHOULD be considered 624 when R=1 and the value of Start-Time is small. 626 Duration (32 bits): The value in seconds, indicates the duration 627 that the LSP is undertaken by a traffic flow and the corresponding 628 LSP must be up to carry traffic. At the expiry of this duration, 629 the LSP is torn down and deleted. Value of 0 MUST NOT be used in 630 Duration since it does not make any sense. The value of Duration 631 SHOULD be greater than a constant MINIMUM-DURATION seconds, where 632 MINIMUM-DURATION is 5. 634 The Start-Time indicates a time at or before which the scheduled LSP 635 must be set up. The value of the Start-Time represents the number of 636 seconds since the epoch when R bit is set to 0. When R bit is set to 637 1, it represents the number of seconds from the current time. 639 In addition, it contains an non zero grace-before and grace-after if 640 grace periods are configured. It includes an non zero elastic range 641 lower bound and upper bound if there is an elastic range configured. 642 A TLV can configure a non-zero grace period or elastic range, but it 643 MUST NOT provide both for an LSP. 645 o GrB (Grace-Before -16 bits): The grace period time length in 646 seconds before the starting time. 648 o GrA (Grace-After -16 bits): The grace period time length in 649 seconds after time interval [starting time, starting time + 650 duration]. 652 o Elastic-Lower-Bound (16 bits): The maximum amount of time in 653 seconds that time interval can shift to lower/left. 655 o Elastic-Upper-Bound (16 bits): The maximum amount of time in 656 seconds that time interval can shift to upper/right. 658 5.2.2. SCHED-PD-LSP-ATTRIBUTE TLV 660 The periodical LSP is a special case of LSP scheduling. The traffic 661 service happens in a series of repeated time intervals. The SCHED- 662 PD-LSP-ATTRIBUTE TLV can be included as an optional TLV within the 663 LSP object for this periodical LSP scheduling. 665 This TLV MUST NOT be included unless both PCEP peers have set the B 666 (LSP-SCHEDULING-CAPABILITY bit) and PD (PD-LSP-CAPABLITY bit) in 667 STATEFUL-PCE-CAPABILITY TLV carried in open message. 669 The format of the SCHED-PD-LSP-ATTRIBUTE TLV is shown in Figure 2. 671 0 1 2 3 672 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 1 673 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 674 | Type (TBD2) | Length | 675 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 676 | Flags |R|C|A| Opt | NR | Reserved (0) | 677 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 678 | Start-Time | 679 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 680 | Duration | 681 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 682 | Repeat-time-length | 683 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 684 | GrB / Elastic-Lower-Bound | GrA / Elastic-Upper-Bound | 685 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 687 Figure 2: SCHED-PD-LSP-ATTRIBUTE TLV 689 The type of the TLV is [TBD2] and the TLV has a fixed length of 24 690 octets. The description, format and meaning of the Flags (R, C and A 691 bit), Start-Time, Duration, GrB, GrA, Elastic-Lower-Bound and 692 Elastic-Upper-Bound fields remains same as SCHED-LSP-ATTRIBUTE TLV. 694 The following fields are new : 696 Opt: (4 bits) Indicates options to repeat. A new registry "Opt" 697 under SCHED-PD-LSP-ATTRIBUTE is created. When a PCE receives a 698 TLV with a Opt value not defined, it does not compute any path for 699 the LSP. It generates a PCEP Error (PCErr) with a PCEP-ERROR 700 object having Error-type = 4 (Not supported object) and Error- 701 value = 4 (Unsupported parameter). 703 Options = 1: repeat every day; 705 Options = 2: repeat every week; 707 Options = 3: repeat every month; 709 Options = 4: repeat every year; 711 Options = 5: repeat every Repeat-time-length. 713 NR: (12 bits) The number of repeats. In each of repeats, LSP 714 carries traffic. 716 Reserved (8 bits): This field MUST be set to zero on transmission 717 and MUST be ignored on receipt. 719 Repeat-time-length: (32 bits) The time in seconds between the start- 720 time of one repetition and the start-time of the next repetition. 722 6. The PCEP Messages 724 6.1. The PCRpt Message 726 Path Computation State Report (PCRpt) is a PCEP message sent by a PCC 727 to a PCE to report the status of one or more LSPs as per [RFC8231]. 728 Each LSP State Report in a PCRpt message contains the actual LSP's 729 path, bandwidth, operational and administrative status, etc. An LSP 730 Status Report carried on a PCRpt message is also used in delegation 731 or revocation of control of an LSP to/from a PCE. In case of 732 scheduled LSP, the scheduled TLVs MUST be carried in the LSP object 733 and the ERO conveys the intended path for the scheduled LSP. The 734 scheduled LSP MUST be delegated to a PCE. This message is also used 735 to synchronize the scheduled LSPs to other PCE as described in 736 [RFC8231] 738 6.2. The PCUpd Message 740 Path Computation Update Request (PCUpd) is a PCEP message sent by a 741 PCE to a PCC to update LSP parameters, on one or more LSPs as per 742 [RFC8231]. Each LSP Update Request on a PCUpd message contains all 743 LSP parameters that a PCE wishes to be set for a given LSP. In case 744 of scheduled LSP, the scheduled TLVs MUST be carried in the LSP 745 object and the ERO conveys the intended path for the scheduled LSP. 746 In case no path can be found, an empty ERO is used. The A bit is 747 used in PCUpd message to indicate the activation of the scheduled LSP 748 in case the PCE is responsible for the activation (as per the C bit). 750 6.3. The PCInitiate Message 752 An LSP Initiate Request (PCInitiate) message is a PCEP message sent 753 by a PCE to a PCC to trigger LSP instantiation or deletion as per 754 [RFC8281]. In case of scheduled LSP, based on the local policy, PCE 755 MAY convey the scheduled LSP to the PCC by including the scheduled 756 TLVs in the LSP object. Or the PCE would initiate the LSP only at 757 the start time of the scheduled LSP as per the [RFC8281] without the 758 use of scheduled TLVs. 760 6.4. The PCReq message 762 The Path Computation Request (PCReq) message is a PCEP message sent 763 by a PCC to a PCE to request a path computation [RFC5440] and it may 764 contain the LSP object [RFC8231] to identify the LSP for which the 765 path computation is requested. In case of scheduled LSP, the 766 scheduled TLVs MUST be carried in the LSP object in PCReq message to 767 request the path computation based on scheduled TED and LSP-DB. A 768 PCC MAY use PCReq message to obtain the scheduled path before 769 delegating the LSP. 771 6.5. The PCRep Message 773 The Path Computation Reply (PCRep) message is a PCEP message sent by 774 a PCE to a PCC in reply to a path computation request [RFC5440] and 775 it may contain the LSP object [RFC8231] to identify the LSP for which 776 the path is computed. A PCRep message can contain either a set of 777 computed paths if the request can be satisfied, or a negative reply 778 if not. The negative reply may indicate the reason why no path could 779 be found. In case of scheduled LSP, the scheduled TLVs MUST be 780 carried in the LSP object in PCRep message to indicate the path 781 computation based on scheduled TED and LSP-DB. A PCC and PCE MAY use 782 PCReq and PCRep message to obtain the scheduled path before 783 delegating the LSP. 785 6.6. The PCErr Message 787 The Path Computation Error (PCErr) message is a PCEP message as 788 described in [RFC5440] for error reporting. The current document 789 defines new error values for several error types to cover failures 790 specific to scheduling and reuse the applicable error types and error 791 values of [RFC5440] and [RFC8231] wherever appropriate. 793 The PCEP extensions for scheduling MUST NOT be used if one or both 794 PCEP speakers have not set the corresponding bits in the STATEFUL- 795 PCE-CAPABILITY TLV in their respective OPEN message. If the PCEP 796 speaker supports the extensions of this specification but did not 797 advertise this capability, then upon receipt of LSP object with the 798 scheduled TLV, it MUST generate a PCEP Error (PCErr) with Error- 799 type=19 (Invalid Operation) and error-value TBD6 (Attempted LSP 800 Scheduling if the scheduling capability was not advertised), and it 801 SHOULD ignore the TLV. As per Section 7.1 of [RFC5440], a legacy 802 PCEP implementation that does not understand this specification, 803 would consider the scheduled TLVs as unknown and ignore them. 805 If the PCC decides that the scheduling parameters proposed in the 806 PCUpd/PCInitiate message are unacceptable, it MUST report this error 807 by including the LSP-ERROR-CODE TLV (Section 7.3.3) with LSP error- 808 value="Unacceptable parameters" in the LSP object (with scheduled 809 TLVs) in the PCRpt message to the PCE. 811 The scheduled TLVs MUST be included in the LSP object for the 812 scheduled LSPs, if the TLV is missing, the receiving PCEP speaker 813 MUST send a PCErr message with Error-type=6 (Mandatory Object 814 missing) and Error-value TBD5 (Scheduled TLV missing). 816 7. Implementation Status 818 [NOTE TO RFC EDITOR : This whole section and the reference to RFC 819 7942 is to be removed before publication as an RFC] 821 This section records the status of known implementations of the 822 protocol defined by this specification at the time of posting of this 823 Internet-Draft, and is based on a proposal described in [RFC7942]. 824 The description of implementations in this section is intended to 825 assist the IETF in its decision processes in progressing drafts to 826 RFCs. Please note that the listing of any individual implementation 827 here does not imply endorsement by the IETF. Furthermore, no effort 828 has been spent to verify the information presented here that was 829 supplied by IETF contributors. This is not intended as, and must not 830 be construed to be, a catalog of available implementations or their 831 features. Readers are advised to note that other implementations may 832 exist. 834 According to [RFC7942], "this will allow reviewers and working groups 835 to assign due consideration to documents that have the benefit of 836 running code, which may serve as evidence of valuable experimentation 837 and feedback that have made the implemented protocols more mature. 838 It is up to the individual working groups to use this information as 839 they see fit". 841 At the time of posting the -09 version of this document, there are no 842 known implementations of this mechanism. It is believed that two 843 vendors/organizations are considering prototype implementations, but 844 these plans are too vague to make any further assertions. 846 8. Security Considerations 848 This document defines LSP-SCHEDULING-CAPABILITY TLV and SCHED-LSP- 849 ATTRIBUTE TLV, the security considerations discussed in [RFC5440], 850 [RFC8231], and [RFC8281] continue to apply. In some deployments the 851 scheduling information could provide details about the network 852 operations that could be deemed as extra sensitive. Additionally, 853 snooping of PCEP messages with such data or using PCEP messages for 854 network reconnaissance may give an attacker sensitive information 855 about the operations of the network. A single PCEP message can now 856 instruct a PCC to set up and tear down an LSP every second for a 857 number of times. That single message could have a significant effect 858 on the network. Thus, such deployment should employ suitable PCEP 859 security mechanisms like TCP Authentication Option (TCP-AO) [RFC5925] 860 or [RFC8253]. The procedure based on Transport Layer Security (TLS) 861 in [RFC8253] is considered a security enhancement and thus is much 862 better suited for the sensitive information. PCCs may also need to 863 apply some form of rate limit to the processing of scheduled LSPs. 865 9. Manageability Consideration 867 9.1. Control of Function and Policy 869 The LSP-Scheduling feature MUST BE controlled per tunnel by the 870 active stateful PCE, the values for parameters like starting time, 871 duration SHOULD BE configurable by customer applications and based on 872 the local policy at PCE. The suggested default values for starting 873 time and duration are one day in seconds from the current time and 874 one year in seconds respectively. One day has 86,400 seconds. One 875 year has 31,536,000 seconds. 877 When configuring the parameters about time, a user SHOULD consider 878 leap-years and leap-seconds. 880 9.2. Information and Data Models 882 An implementation SHOULD allow the operator to view the capability 883 defined in this document. To serve this purpose, the PCEP YANG 884 module [I-D.ietf-pce-pcep-yang] could be extended. 886 9.3. Liveness Detection and Monitoring 888 Mechanisms defined in this document do not imply any new liveness 889 detection and monitoring requirements in addition to those already 890 listed in [RFC5440]. 892 9.4. Verify Correct Operations 894 Mechanisms defined in this document do not imply any new operation 895 verification requirements in addition to those already listed in 896 [RFC5440]. 898 9.5. Requirements On Other Protocols 900 Mechanisms defined in this document do not imply any new requirements 901 on other protocols. 903 9.6. Impact On Network Operations 905 Mechanisms defined in this document do not have any impact on network 906 operations in addition to those already listed in [RFC5440]. 908 10. IANA Considerations 910 10.1. PCEP TLV Type Indicators 912 This document defines the following new PCEP TLVs. IANA maintains a 913 sub-registry "PCEP TLV Type Indicators" in the "Path Computation 914 Element Protocol (PCEP) Numbers" registry. IANA is requested to make 915 the following allocations from this sub-registry. 917 Value Meaning Reference 918 TBD1 SCHED-LSP-ATTRIBUTE This document 919 TBD2 SCHED-PD-LSP-ATTRIBUTE This document 921 10.1.1. Opt Field in SCHED-PD-LSP-ATTRIBUTE TLV 923 IANA is requested to create and maintain a new sub-registry named 924 "SCHED-PD-LSP-ATTRIBUTE TLV Opt field" within the "Path Computation 925 Element Protocol (PCEP) Numbers" registry. Initial values for the 926 sub-registry are given below. New values are assigned by Standards 927 Action [RFC8126]. 929 Value Name Reference 930 ----- ---- ---------- 931 0 Reserved 932 1 REPEAT-EVERY-DAY This document 933 2 REPEAT-EVERY-WEEK This document 934 3 REPEAT-EVERY-MONTH This document 935 4 REPEAT-EVERY-YEAR This document 936 5 REPEAT-EVERY-REPEAT-TIME-LENGTH This document 937 6-14 Unassigned 938 15 Reserved 940 10.1.2. Schedule TLVs Flag Field 942 IANA is requested to create a new sub-registry, named "Schedule TLVs 943 Flag Field", within the "Path Computation Element Protocol (PCEP) 944 Numbers" registry. New values are assigned by Standards Action 945 [RFC8126]. Each bit should be tracked with the following qualities: 947 o Bit number (counting from bit 0 as the most significant bit) 949 o Capability description 951 o Defining RFC 953 The following values are defined in this document: 955 Bit Description Reference 956 0-3 Unassigned 957 4 Relative Time (R-bit) This document 958 5 PCC Responsible (C-bit) This document 959 6 LSP Activated (A-bit) This document 960 7 Grace Period Included (G-bit) This document 962 10.2. STATEFUL-PCE-CAPABILITY TLV Flag field 964 This document defines new bits in the Flags field in the STATEFUL- 965 PCE-CAPABILITY TLV in the OPEN object. IANA maintains a sub-registry 966 "STATEFUL-PCE-CAPABILITY TLV Flag Field" in the "Path Computation 967 Element Protocol (PCEP) Numbers" registry. IANA is requested to make 968 the following allocations from this sub-registry. 970 The following values are defined in this document: 972 Bit Description Reference 973 TBD3 LSP-SCHEDULING-CAPABILITY (B-bit) This document 974 TBD4 PD-LSP-CAPABLITY (PD-bit) This document 976 10.3. PCEP-Error Object 978 IANA is requested to allocate the following new error types to the 979 existing error values within the "PCEP-ERROR Object Error Types and 980 Values" subregistry of the "Path Computation Element Protocol (PCEP) 981 Numbers" registry: 983 Error-Type Meaning 984 6 Mandatory Object missing 986 Error-value 987 TBD5: Scheduled TLV missing 989 19 Invalid Operation 991 Error-value 992 TBD6: Attempted LSP Scheduling if the scheduling 993 capability was not advertised 995 29 Path computation failure 997 Error-value 998 TBD7: Constraints could not be met for some intervals 1000 11. Acknowledgments 1002 The authors of this document would also like to thank Rafal Szarecki, 1003 Adrian Farrel, Cyril Margaria for the review and comments. 1005 12. References 1007 12.1. Normative References 1009 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1010 Requirement Levels", BCP 14, RFC 2119, 1011 DOI 10.17487/RFC2119, March 1997, 1012 . 1014 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 1015 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 1016 DOI 10.17487/RFC5440, March 2009, 1017 . 1019 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1020 Writing an IANA Considerations Section in RFCs", BCP 26, 1021 RFC 8126, DOI 10.17487/RFC8126, June 2017, 1022 . 1024 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1025 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 1026 May 2017, . 1028 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 1029 Computation Element Communication Protocol (PCEP) 1030 Extensions for Stateful PCE", RFC 8231, 1031 DOI 10.17487/RFC8231, September 2017, 1032 . 1034 [RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X., 1035 and D. Dhody, "Optimizations of Label Switched Path State 1036 Synchronization Procedures for a Stateful PCE", RFC 8232, 1037 DOI 10.17487/RFC8232, September 2017, 1038 . 1040 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 1041 Computation Element Communication Protocol (PCEP) 1042 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 1043 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 1044 . 1046 12.2. Informative References 1048 [I-D.ietf-detnet-architecture] 1049 Finn, N., Thubert, P., Varga, B., and J. Farkas, 1050 "Deterministic Networking Architecture", draft-ietf- 1051 detnet-architecture-13 (work in progress), May 2019. 1053 [I-D.ietf-pce-pcep-yang] 1054 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 1055 YANG Data Model for Path Computation Element 1056 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 1057 yang-13 (work in progress), October 2019. 1059 [I-D.litkowski-pce-state-sync] 1060 Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter 1061 Stateful Path Computation Element (PCE) Communication 1062 Procedures.", draft-litkowski-pce-state-sync-07 (work in 1063 progress), January 2020. 1065 [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP 1066 Authentication Option", RFC 5925, DOI 10.17487/RFC5925, 1067 June 2010, . 1069 [RFC7399] Farrel, A. and D. King, "Unanswered Questions in the Path 1070 Computation Element Architecture", RFC 7399, 1071 DOI 10.17487/RFC7399, October 2014, 1072 . 1074 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 1075 Code: The Implementation Status Section", BCP 205, 1076 RFC 7942, DOI 10.17487/RFC7942, July 2016, 1077 . 1079 [RFC8051] Zhang, X., Ed. and I. Minei, Ed., "Applicability of a 1080 Stateful Path Computation Element (PCE)", RFC 8051, 1081 DOI 10.17487/RFC8051, January 2017, 1082 . 1084 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 1085 "PCEPS: Usage of TLS to Provide a Secure Transport for the 1086 Path Computation Element Communication Protocol (PCEP)", 1087 RFC 8253, DOI 10.17487/RFC8253, October 2017, 1088 . 1090 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 1091 Decraene, B., Litkowski, S., and R. Shakir, "Segment 1092 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 1093 July 2018, . 1095 [RFC8413] Zhuang, Y., Wu, Q., Chen, H., and A. Farrel, "Framework 1096 for Scheduled Use of Resources", RFC 8413, 1097 DOI 10.17487/RFC8413, July 2018, 1098 . 1100 Appendix A. Contributors Addresses 1102 Dhruv Dhody 1103 Huawei 1104 Divyashree Techno Park, Whitefield 1105 Bangalore, Karnataka 560066 1106 India 1108 Email: dhruv.ietf@gmail.com 1110 Xufeng Liu 1111 Ericsson 1112 USA 1113 Email: xliu@kuatrotech.com 1115 Mehmet Toy 1116 Verizon 1117 USA 1118 Email: mehmet.toy@verizon.com 1120 Vic Liu 1121 China Mobile 1122 No.32 Xuanwumen West Street, Xicheng District 1123 Beijing, 100053 1124 China 1125 Email: liu.cmri@gmail.com 1127 Lei Liu 1128 Fujitsu 1129 USA 1130 Email: lliu@us.fujitsu.com 1132 Khuzema Pithewan 1133 Infinera 1134 Email: kpithewan@infinera.com 1136 Zitao Wang 1137 Huawei 1138 101 Software Avenue, Yuhua District 1139 Nanjing, Jiangsu 210012 1140 China 1142 Email: wangzitao@huawei.com 1144 Xian Zhang 1145 Huawei Technologies 1146 Research Area F3-1B, 1147 Huawei Industrial Base, 1148 Shenzhen, 518129, China 1150 Email: zhang.xian@huawei.com 1152 Authors' Addresses 1154 Huaimo Chen (editor) 1155 Futurewei 1156 Boston, MA 1157 USA 1159 Email: huaimo.chen@futurewei.com 1161 Yan Zhuang (editor) 1162 Huawei 1163 101 Software Avenue, Yuhua District 1164 Nanjing, Jiangsu 210012 1165 China 1167 Email: zhuangyan.zhuang@huawei.com 1168 Qin Wu 1169 Huawei 1170 101 Software Avenue, Yuhua District 1171 Nanjing, Jiangsu 210012 1172 China 1174 Email: bill.wu@huawei.com 1176 Daniele Ceccarelli 1177 Ericsson 1178 Via A. Negrone 1/A 1179 Genova - Sestri Ponente 1180 Italy 1182 Email: daniele.ceccarelli@ericsson.com