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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documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 6006 (Obsoleted by RFC 8306) == Outdated reference: A later version (-07) exists of draft-dwpz-pce-domain-diverse-01 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--).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: December 5, 2014 June 3, 2014 7 PCE support for Maximizing Diversity 8 draft-dhody-pce-of-diverse-01 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 December 5, 2014. 45 Copyright Notice 47 Copyright (c) 2014 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 . . . . . . . . . . . . . . 6 79 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 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 87 1. Introduction 89 [RFC5440] describes the specifications for the Path Computation 90 Element Communication Protocol (PCEP). PCEP specifies the 91 communication between a Path Computation Client (PCC) and a Path 92 Computation Element (PCE), or between two PCEs based on the PCE 93 architecture [RFC4655]. 95 Further [RFC5440] describes dependent path computation requests in 96 which case computations cannot be performed independently of each 97 other, and usually used for diverse path computation. [RFC5440] and 98 [RFC6006] describe the use of Synchronization VECtor (SVEC) 99 dependency flags (i.e., Node, Link, or Shared Risk Link Group (SRLG) 100 diverse flags). 102 In some scenario it may be noted that full diversity cannot be 103 achieved because of topology considerations, deployment 104 considerations, transient network issues etc. In this case it would 105 be helpful to maximize diversity as much as possible (or in other 106 words minimize the common shared resources (Node, Link or SRLG) 107 between a set of paths during path computation). 109 It is interesting to note that for non synchronized diverse path 110 computation the X bit in Exclude Route Object (XRO) or Explicit 111 Exclusion Route subobject (EXRS) [RFC5521] can be used, where X bit 112 set as 1 indicates that the resource specified SHOULD be excluded 113 from the path computed by the PCE, but MAY be included subject to PCE 114 policy and the absence of a viable path that meets the other 115 constraints and excludes the resource. Thus X bit can be used in a 116 way to maximize diversity (or minimize common shared resources) when 117 full diversity cannot be achieved. 119 This document defines objective function code types for three new 120 objective functions for this purpose to be applied to a set of 121 synchronized path computation requests. 123 1.1. Requirements Language 125 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 126 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 127 document are to be interpreted as described in [RFC2119]. 129 2. Terminology 131 The terminology is as per [RFC5440]. 133 3. Extension to PCEP 135 [RFC5541] describes and define Objective function (OF) used in PCEP 136 protocol. 138 To minimize the common shared resources (Node, Link or SRLG) between 139 a set of paths during path computation three new OF codes are 140 proposed: 142 MSL 144 * Name: Minimize the number of shared (common) Links. 146 * Objective Function Code: TBD 148 * Description: Find a set of paths such that it passes through the 149 least number of shared (common) links. 151 MSN 153 * Name: Minimize the number of shared (common) Nodes. 155 * Objective Function Code: TBD 157 * Description: Find a set of paths such that it passes through the 158 least number of shared (common) nodes. 160 MSS 162 * Name: Minimize the number of shared (common) SRLG. 164 * Objective Function Code: TBD 166 * Description: Find a set of paths such that it share least number 167 of common SRLGs. 169 4. Other Considerations 171 4.1. Relationship between SVEC Diversity Flags and OF 173 [RFC5440] uses SVEC diversity flag for node, link or SRLG to describe 174 the potential disjointness between the set of path computation 175 requests used in PCEP protocol. [I-D.dwpz-pce-domain-diverse] 176 further extends by adding domain-diverse O-bit in SVEC object and a 177 new OF Code for minimizing the number of shared transit domain. 179 This document defines three new OF codes to maximize diversity as 180 much as possible, in other words, minimize the common shared 181 resources (Node,Link or SRLG) between a set of paths. 183 It may be interesting to note that the diversity flags in the SVEC 184 object and OF for diversity can be used together. Some example of 185 usage are listed below - 186 o SVEC object with node-diverse bit=1 - ensure full node-diversity. 188 o SVEC object with node-diverse bit=1 and OF=MSS - full node diverse 189 with as much as SRLG-diversity as possible. 191 o SVEC object with domain-diverse bit=1;link diverse bit=1 and 192 OF=MSS - full domain and node diverse path with as much as SRLG- 193 diversity as possible. 195 o SVEC object with node-diverse bit=1 and OF=MSN - ensure full node- 196 diversity. 198 4.2. Inter-Domain Considerations 200 The mechanics for synchronous end to end path computations using 201 Backward-Recursive PCE-Based Computation (BRPC) procedure [RFC5441] 202 described in [RFC6006]. 204 In H-PCE [RFC6805] architecture, the parent PCE is used to compute a 205 multi-domain path based on the domain connectivity information. The 206 parent PCE may be requested to provide a end to end path or only the 207 sequence of domains. Child PCE should be able to request 208 synchronized diverse end to end paths from its parent PCE. 210 The new objective function described in this document can be used to 211 maximize diversity when full diverse paths cannot be found. 213 4.3. Domain Diversity 215 As per [I-D.dwpz-pce-domain-diverse]. 217 4.4. Diversity v/s Optimality 219 In case of non-synchronized path computation, PCE may be requested to 220 provide an optimal primary path first and then PCC requests for a 221 backup path with exclusion. Note that this approach does not 222 guarantee diversity comparing to disjoint path computations for 223 primary and backup path in a synchronized manner. 225 A synchronized path computation with diversity flags and/or objective 226 function is used to make sure that both the primary path and the 227 backup path can be computed simultaneously with full diversity or 228 optimized to be as diverse as possible. In the latter case we may 229 sacrifice optimal path for diversity, thus there is a trade-off 230 between the two. 232 An implementation may further choose to analyze the trade-off i.e. it 233 may send multiple request to PCE asking to optimize based on 234 diversity as well as say, cost and make an intelligent choice between 235 them. 237 5. Security Considerations 239 TBD. 241 6. Manageability Considerations 243 6.1. Control of Function and Policy 245 TBD. 247 6.2. Information and Data Models 249 TBD. 251 6.3. Liveness Detection and Monitoring 253 TBD. 255 6.4. Verify Correct Operations 257 TBD. 259 6.5. Requirements On Other Protocols 261 TBD. 263 6.6. Impact On Network Operations 265 TBD. 267 7. IANA Considerations 269 As described in Section 3, three new Objective Functions have been 270 defined. IANA has made the following allocations from the PCEP 271 "Objective Function" sub-registry: 273 Value Description Reference 274 (TBD) MSL [This I.D.] 275 (TBD) MSN [This I.D.] 276 (TBD) MSS [This I.D.] 278 8. Acknowledgments 280 We would like to thank Adrian Farrel for pointing out the need for 281 this document. 283 9. References 285 9.1. Normative References 287 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 288 Requirement Levels", BCP 14, RFC 2119, March 1997. 290 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 291 (PCE) Communication Protocol (PCEP)", RFC 5440, March 292 2009. 294 [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of 295 Objective Functions in the Path Computation Element 296 Communication Protocol (PCEP)", RFC 5541, June 2009. 298 9.2. Informative References 300 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 301 Element (PCE)-Based Architecture", RFC 4655, August 2006. 303 [RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A 304 Backward-Recursive PCE-Based Computation (BRPC) Procedure 305 to Compute Shortest Constrained Inter-Domain Traffic 306 Engineering Label Switched Paths", RFC 5441, April 2009. 308 [RFC5521] Oki, E., Takeda, T., and A. Farrel, "Extensions to the 309 Path Computation Element Communication Protocol (PCEP) for 310 Route Exclusions", RFC 5521, April 2009. 312 [RFC6006] Zhao, Q., King, D., Verhaeghe, F., Takeda, T., Ali, Z., 313 and J. Meuric, "Extensions to the Path Computation Element 314 Communication Protocol (PCEP) for Point-to-Multipoint 315 Traffic Engineering Label Switched Paths", RFC 6006, 316 September 2010. 318 [RFC6805] King, D. and A. Farrel, "The Application of the Path 319 Computation Element Architecture to the Determination of a 320 Sequence of Domains in MPLS and GMPLS", RFC 6805, November 321 2012. 323 [I-D.dwpz-pce-domain-diverse] 324 Dhody, D., Wu, Q., Palle, U., and X. Zhang, "PCE support 325 for Domain Diversity", draft-dwpz-pce-domain-diverse-01 326 (work in progress), March 2014. 328 Appendix A. Contributor Addresses 330 Xian Zhang 331 Huawei Technologies 332 Bantian, Longgang District 333 Shenzhen 518129 334 P.R.China 336 EMail: zhang.xian@huawei.com 338 Udayasree Palle 339 Huawei Technologies 340 Leela Palace 341 Bangalore, Karnataka 560008 342 INDIA 344 EMail: udayasree.palle@huawei.com 346 Avantika 347 Huawei Technologies 348 Leela Palace 349 Bangalore, Karnataka 560008 350 INDIA 352 EMail: avantika.sushilkumar@huawei.com 354 Appendix B. Example 356 This section illustrate an example based on SRLG. 358 (1) (2) (3) 359 A---------B---------C---------D 360 | | | | 361 | (2)| (5)| | 362 | | | | 363 +---------E---------F---------+ 364 (4) (2) (5) 366 Node A is Ingress, Node D is Egress. A synchronized path computation 367 requests for SRLG disjoint path may be issued using the SVEC object 368 as described in [RFC5440]. In above topology a full SRLG disjoint 369 paths are not possible because of some topology considerations. 371 In such scenario, an OF MSS maybe used instead to minimize the number 372 of shared (common) SRLG to get maximum diversity when full diversity 373 may not be possible. 375 In case of sequential non-synchronized path computation, primary path 376 will be computed first, say the path is (A--B--C--D) with SRLG list 377 (1,2,3). A backup path computation using XRO and SRLG sub-object 378 with X bit (loose) set as 1, can be used to achieve a similar result. 380 Authors' Addresses 382 Dhruv Dhody 383 Huawei Technologies 384 Leela Palace 385 Bangalore, Karnataka 560008 386 INDIA 388 EMail: dhruv.ietf@gmail.com 390 Qin Wu 391 Huawei Technologies 392 101 Software Avenue, Yuhua District 393 Nanjing, Jiangsu 210012 394 China 396 EMail: bill.wu@huawei.com