idnits 2.17.1 draft-dhody-pce-of-diverse-04.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (December 11, 2015) is 3058 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 6006 (Obsoleted by RFC 8306) == Outdated reference: A later version (-07) exists of draft-dwpz-pce-domain-diverse-04 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group D. Dhody 3 Internet-Draft Q. Wu 4 Intended status: Standards Track Huawei Technologies 5 Expires: June 13, 2016 December 11, 2015 7 PCE support for Maximizing Diversity 8 draft-dhody-pce-of-diverse-04 10 Abstract 12 The computation of one or a set of Traffic Engineering Label Switched 13 Paths (TE LSPs) in MultiProtocol Label Switching (MPLS) and 14 Generalized MPLS (GMPLS) networks is subject to a set of one or more 15 specific optimization criteria, referred to as objective functions. 17 In the Path Computation Element (PCE) architecture, a Path 18 Computation Client (PCC) may want a set of services that are required 19 to be diverse (disjointed) from each other. In case when full 20 diversity could not be achieved, it is helpful to maximize diversity 21 as much as possible (or in other words, minimize the common shared 22 resources). 24 This document defines objective function code types for three new 25 objective functions for this purpose to be applied to a set of 26 synchronized path computation requests. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at http://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on June 13, 2016. 45 Copyright Notice 47 Copyright (c) 2015 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (http://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 64 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 3. Extension to PCEP . . . . . . . . . . . . . . . . . . . . . . 3 66 4. Other Considerations . . . . . . . . . . . . . . . . . . . . 4 67 4.1. Relationship between SVEC Diversity Flags and OF . . . . 4 68 4.2. Inter-Domain Considerations . . . . . . . . . . . . . . . 5 69 4.3. Domain Diversity . . . . . . . . . . . . . . . . . . . . 5 70 4.4. Diversity v/s Optimality . . . . . . . . . . . . . . . . 5 71 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 72 6. Manageability Considerations . . . . . . . . . . . . . . . . 6 73 6.1. Control of Function and Policy . . . . . . . . . . . . . 6 74 6.2. Information and Data Models . . . . . . . . . . . . . . . 6 75 6.3. Liveness Detection and Monitoring . . . . . . . . . . . . 6 76 6.4. Verify Correct Operations . . . . . . . . . . . . . . . . 6 77 6.5. Requirements On Other Protocols . . . . . . . . . . . . . 6 78 6.6. Impact On Network Operations . . . . . . . . . . . . . . 7 79 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 80 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 81 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 82 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 83 9.2. Informative References . . . . . . . . . . . . . . . . . 7 84 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 9 85 Appendix B. Example . . . . . . . . . . . . . . . . . . . . . . 9 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 88 1. Introduction 90 [RFC5440] describes the specifications for the Path Computation 91 Element Communication Protocol (PCEP). PCEP specifies the 92 communication between a Path Computation Client (PCC) and a Path 93 Computation Element (PCE), or between two PCEs based on the PCE 94 architecture [RFC4655]. 96 Further [RFC5440] describes dependent path computation requests in 97 which case computations cannot be performed independently of each 98 other, and usually used for diverse path computation. [RFC5440] and 99 [RFC6006] describe the use of Synchronization VECtor (SVEC) 100 dependency flags (i.e., Node, Link, or Shared Risk Link Group (SRLG) 101 diverse flags). 103 In some scenario it may be noted that full diversity cannot be 104 achieved because of topology considerations, deployment 105 considerations, transient network issues etc. In this case it would 106 be helpful to maximize diversity as much as possible (or in other 107 words minimize the common shared resources (Node, Link or SRLG) 108 between a set of paths during path computation). 110 It is interesting to note that for non synchronized diverse path 111 computation the X bit in Exclude Route Object (XRO) or Explicit 112 Exclusion Route subobject (EXRS) [RFC5521] can be used, where X bit 113 set as 1 indicates that the resource specified SHOULD be excluded 114 from the path computed by the PCE, but MAY be included subject to PCE 115 policy and the absence of a viable path that meets the other 116 constraints and excludes the resource. Thus X bit can be used in a 117 way to maximize diversity (or minimize common shared resources) when 118 full diversity cannot be achieved. 120 This document defines objective function code types for three new 121 objective functions for this purpose to be applied to a set of 122 synchronized path computation requests. 124 1.1. Requirements Language 126 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 127 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 128 document are to be interpreted as described in [RFC2119]. 130 2. Terminology 132 The terminology is as per [RFC5440]. 134 3. Extension to PCEP 136 [RFC5541] describes and define Objective function (OF) used in PCEP 137 protocol. 139 To minimize the common shared resources (Node, Link or SRLG) between 140 a set of paths during path computation three new OF codes are 141 proposed: 143 MSL 145 * Name: Minimize the number of shared (common) Links. 147 * Objective Function Code: TBD 149 * Description: Find a set of paths such that it passes through the 150 least number of shared (common) links. 152 MSN 154 * Name: Minimize the number of shared (common) Nodes. 156 * Objective Function Code: TBD 158 * Description: Find a set of paths such that it passes through the 159 least number of shared (common) nodes. 161 MSS 163 * Name: Minimize the number of shared (common) SRLG. 165 * Objective Function Code: TBD 167 * Description: Find a set of paths such that it share least number 168 of common SRLGs. 170 4. Other Considerations 172 4.1. Relationship between SVEC Diversity Flags and OF 174 [RFC5440] uses SVEC diversity flag for node, link or SRLG to describe 175 the potential disjointness between the set of path computation 176 requests used in PCEP protocol. [I-D.dwpz-pce-domain-diverse] 177 further extends by adding domain-diverse O-bit in SVEC object and a 178 new OF Code for minimizing the number of shared transit domain. 180 This document defines three new OF codes to maximize diversity as 181 much as possible, in other words, minimize the common shared 182 resources (Node,Link or SRLG) between a set of paths. 184 It may be interesting to note that the diversity flags in the SVEC 185 object and OF for diversity can be used together. Some example of 186 usage are listed below - 187 o SVEC object with node-diverse bit=1 - ensure full node-diversity. 189 o SVEC object with node-diverse bit=1 and OF=MSS - full node diverse 190 with as much as SRLG-diversity as possible. 192 o SVEC object with domain-diverse bit=1;link diverse bit=1 and 193 OF=MSS - full domain and node diverse path with as much as SRLG- 194 diversity as possible. 196 o SVEC object with node-diverse bit=1 and OF=MSN - ensure full node- 197 diversity. 199 4.2. Inter-Domain Considerations 201 The mechanics for synchronous end to end path computations using 202 Backward-Recursive PCE-Based Computation (BRPC) procedure [RFC5441] 203 described in [RFC6006]. 205 In H-PCE [RFC6805] architecture, the parent PCE is used to compute a 206 multi-domain path based on the domain connectivity information. The 207 parent PCE may be requested to provide a end to end path or only the 208 sequence of domains. Child PCE should be able to request 209 synchronized diverse end to end paths from its parent PCE. 211 The new objective function described in this document can be used to 212 maximize diversity when full diverse paths cannot be found. 214 4.3. Domain Diversity 216 As per [I-D.dwpz-pce-domain-diverse]. 218 4.4. Diversity v/s Optimality 220 In case of non-synchronized path computation, PCE may be requested to 221 provide an optimal primary path first and then PCC requests for a 222 backup path with exclusion. Note that this approach does not 223 guarantee diversity comparing to disjoint path computations for 224 primary and backup path in a synchronized manner. 226 A synchronized path computation with diversity flags and/or objective 227 function is used to make sure that both the primary path and the 228 backup path can be computed simultaneously with full diversity or 229 optimized to be as diverse as possible. In the latter case we may 230 sacrifice optimal path for diversity, thus there is a trade-off 231 between the two. 233 An implementation may further choose to analyze the trade-off i.e. it 234 may send multiple request to PCE asking to optimize based on 235 diversity as well as say, cost and make an intelligent choice between 236 them. 238 5. Security Considerations 240 PCEP security mechanisms are described in [RFC5440] and are used to 241 secure entire PCEP messages. Nothing in this document changes the 242 message flows or introduces any new messages, so the security 243 mechanisms set out in [RFC5440] continue to be applicable. 245 This document add new OF codes that may optionally be carried on PCEP 246 messages with OF object [RFC5541] and will be automatically secured 247 using the mechanisms described in [RFC5440]. 249 If a PCEP message is vulnerable to attack (for example, because the 250 security mechanisms are not used), then the OF object could be used 251 as part of an attack; however, it is likely that other objects will 252 provide far more significant ways of attacking a PCE or PCC in this 253 case. 255 6. Manageability Considerations 257 6.1. Control of Function and Policy 259 In addition to [RFC5440], the PCC should construct the SVECs to 260 identify and associate diverse SVEC relationships. Considerations 261 for use of objective functions are mentioned in [RFC5541]. 263 6.2. Information and Data Models 265 The PCEP MIB Module defined in [RFC7420], there are no additional 266 parameters identified in this document. 268 6.3. Liveness Detection and Monitoring 270 [RFC5440] provides a sufficient description for this document. There 271 are no additional considerations. 273 6.4. Verify Correct Operations 275 [RFC5440] provides a sufficient description for this document. There 276 are no additional considerations. 278 6.5. Requirements On Other Protocols 280 [RFC5440] provides a sufficient description for this document. There 281 are no additional considerations. 283 6.6. Impact On Network Operations 285 Mechanisms defined in this document do not have any impact on network 286 operations in addition to those already listed in [RFC5440] and 287 [RFC5541]. 289 7. IANA Considerations 291 As described in Section 3, three new Objective Functions have been 292 defined. IANA has made the following allocations from the PCEP 293 "Objective Function" sub-registry: 295 Value Description Reference 296 (TBD) MSL [This I.D.] 297 (TBD) MSN [This I.D.] 298 (TBD) MSS [This I.D.] 300 8. Acknowledgments 302 We would like to thank Adrian Farrel for pointing out the need for 303 this document. 305 9. References 307 9.1. Normative References 309 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 310 Requirement Levels", BCP 14, RFC 2119, 311 DOI 10.17487/RFC2119, March 1997, 312 . 314 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 315 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 316 DOI 10.17487/RFC5440, March 2009, 317 . 319 [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of 320 Objective Functions in the Path Computation Element 321 Communication Protocol (PCEP)", RFC 5541, 322 DOI 10.17487/RFC5541, June 2009, 323 . 325 9.2. Informative References 327 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 328 Element (PCE)-Based Architecture", RFC 4655, 329 DOI 10.17487/RFC4655, August 2006, 330 . 332 [RFC5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux, 333 "A Backward-Recursive PCE-Based Computation (BRPC) 334 Procedure to Compute Shortest Constrained Inter-Domain 335 Traffic Engineering Label Switched Paths", RFC 5441, 336 DOI 10.17487/RFC5441, April 2009, 337 . 339 [RFC5521] Oki, E., Takeda, T., and A. Farrel, "Extensions to the 340 Path Computation Element Communication Protocol (PCEP) for 341 Route Exclusions", RFC 5521, DOI 10.17487/RFC5521, April 342 2009, . 344 [RFC6006] Zhao, Q., Ed., King, D., Ed., Verhaeghe, F., Takeda, T., 345 Ali, Z., and J. Meuric, "Extensions to the Path 346 Computation Element Communication Protocol (PCEP) for 347 Point-to-Multipoint Traffic Engineering Label Switched 348 Paths", RFC 6006, DOI 10.17487/RFC6006, September 2010, 349 . 351 [RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the 352 Path Computation Element Architecture to the Determination 353 of a Sequence of Domains in MPLS and GMPLS", RFC 6805, 354 DOI 10.17487/RFC6805, November 2012, 355 . 357 [RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J. 358 Hardwick, "Path Computation Element Communication Protocol 359 (PCEP) Management Information Base (MIB) Module", 360 RFC 7420, DOI 10.17487/RFC7420, December 2014, 361 . 363 [I-D.dwpz-pce-domain-diverse] 364 Dhody, D., Wu, Q., Palle, U., and X. Zhang, "PCE support 365 for Domain Diversity", draft-dwpz-pce-domain-diverse-04 366 (work in progress), October 2015. 368 Appendix A. Contributor Addresses 370 Xian Zhang 371 Huawei Technologies 372 Bantian, Longgang District 373 Shenzhen 518129 374 P.R.China 376 EMail: zhang.xian@huawei.com 378 Udayasree Palle 379 Huawei Technologies 380 Divyashree Techno Park, Whitefield 381 Bangalore, Karnataka 560037 382 India 384 EMail: udayasree.palle@huawei.com 386 Avantika 387 Huawei Technologies 388 Divyashree Techno Park, Whitefield 389 Bangalore, Karnataka 560037 390 India 392 EMail: avantika.sushilkumar@huawei.com 394 Appendix B. Example 396 This section illustrate an example based on SRLG. 398 (1) (2) (3) 399 A---------B---------C---------D 400 | | | | 401 | (2)| (5)| | 402 | | | | 403 +---------E---------F---------+ 404 (4) (2) (5) 406 Node A is Ingress, Node D is Egress. A synchronized path computation 407 requests for SRLG disjoint path may be issued using the SVEC object 408 as described in [RFC5440]. In above topology a full SRLG disjoint 409 paths are not possible because of some topology considerations. 411 In such scenario, an OF MSS maybe used instead to minimize the number 412 of shared (common) SRLG to get maximum diversity when full diversity 413 may not be possible. 415 In case of sequential non-synchronized path computation, primary path 416 will be computed first, say the path is (A--B--C--D) with SRLG list 417 (1,2,3). A backup path computation using XRO and SRLG sub-object 418 with X bit (loose) set as 1, can be used to achieve a similar result. 420 Authors' Addresses 422 Dhruv Dhody 423 Huawei Technologies 424 Divyashree Techno Park, Whitefield 425 Bangalore, Karnataka 560037 426 India 428 EMail: dhruv.ietf@gmail.com 430 Qin Wu 431 Huawei Technologies 432 101 Software Avenue, Yuhua District 433 Nanjing, Jiangsu 210012 434 China 436 EMail: bill.wu@huawei.com