idnits 2.17.1 draft-dhody-pce-of-diverse-00.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 (March 26, 2014) is 3678 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documents in RFCs) -- Obsolete informational reference (is this intentional?): RFC 6006 (Obsoleted by RFC 8306) == Outdated reference: A later version (-07) exists of draft-dwpz-pce-domain-diverse-00 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 2 comments (--).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: September 27, 2014 March 26, 2014 7 PCE support for Maximizing Diversity 8 draft-dhody-pce-of-diverse-00 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 September 27, 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 . . . . . . . . . . . . . . . . . . . 5 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 . . . . . . . . . . . . . . . . . . . . . . . 6 81 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 82 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 83 9.2. Informative References . . . . . . . . . . . . . . . . . 7 84 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 8 86 1. Introduction 88 [RFC5440] describes the specifications for the Path Computation 89 Element Communication Protocol (PCEP). PCEP specifies the 90 communication between a Path Computation Client (PCC) and a Path 91 Computation Element (PCE), or between two PCEs based on the PCE 92 architecture [RFC4655]. 94 Further [RFC5440] describes dependent path computation requests in 95 which case computations cannot be performed independently of each 96 other used for diverse path computation. [RFC5440] and [RFC6006] 97 describe the use of Synchronization VECtor (SVEC) dependency flags 98 (i.e., Node, Link, or Shared Risk Link Group (SRLG) diverse flags). 100 In some scenario it may be noted that full diversity cannot be 101 achieved because of topology considerations, deployment 102 considerations, transient network issues etc. In this case it would 103 be helpful to maximize diversity as much as possible (or in other 104 words minimize the common shared resources (Node, Link or SRLG) 105 between a set of paths during path computation). 107 It is interesting to note that for non synchronized diverse path 108 computation the X bit in XRO or EXRS [RFC5521] sub-objects can be 109 used, where X bit set as 1 indicates that the resource specified 110 SHOULD be excluded from the path computed by the PCE, but MAY be 111 included subject to PCE policy and the absence of a viable path that 112 meets the other constraints and excludes the resource. 114 This document defines objective function code types for three new 115 objective functions for this purpose to be applied to a set of 116 synchronized path computation requests. 118 1.1. Requirements Language 120 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 121 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 122 document are to be interpreted as described in [RFC2119]. 124 2. Terminology 126 The terminology is as per [RFC5440]. 128 3. Extension to PCEP 130 [RFC5541] describes and define Objective function (OF) used in PCEP 131 protocol. 133 To minimize the common shared resources (Node, Link or SRLG) between 134 a set of paths during path computation three new OF codes are 135 proposed: 137 MSL 139 * Name: Minimize the number of shared (common) Links. 141 * Objective Function Code: TBD 142 * Description: Find a set of paths such that it passes through the 143 least number of shared (common) links. 145 MSN 147 * Name: Minimize the number of shared (common) Nodes. 149 * Objective Function Code: TBD 151 * Description: Find a set of paths such that it passes through the 152 least number of shared (common) nodes. 154 MSS 156 * Name: Minimize the number of shared (common) SRLG. 158 * Objective Function Code: TBD 160 * Description: Find a set of paths such that it share least number 161 of common SRLGs. 163 4. Other Considerations 165 4.1. Relationship between SVEC Diversity Flags and OF 167 [RFC5440] uses SVEC diversity flag for node, link or SRLG to describe 168 the potential disjointness between the set of path computation 169 requests used in PCEP protocol. [I-D.dwpz-pce-domain-diverse] 170 further extends by adding domain-diverse O-bit in SVEC object and a 171 new OF Code for minimizing the number of shared transit domain. 173 This document defines three new OF codes to maximize diversity as 174 much as possible, in other words, minimize the common shared 175 resources (Node,Link or SRLG) between a set of paths. 177 It may be interesting to note that the diversity flags in the SVEC 178 object and OF for diversity can be used together. Some example of 179 usage are listed below - 181 o SVEC object with node-diverse bit=1 - ensure full node-diversity. 183 o SVEC object with node-diverse bit=1 and OF=MSS - full node diverse 184 with as much as SRLG-diversity as possible. 186 o SVEC object with domain-diverse bit=1;link diverse bit=1 and 187 OF=MSS - full domain and node diverse path with as much as SRLG- 188 diversity as possible. 190 o SVEC object with node-diverse bit=1 and OF=MSN - ensure full node- 191 diversity. 193 4.2. Inter-Domain Considerations 195 The mechanics for synchronous end to end path computations using 196 Backward-Recursive PCE-Based Computation (BRPC) procedure [RFC5441] 197 described in [RFC6006]. 199 In H-PCE [RFC6805] architecture, the parent PCE is used to compute a 200 multi-domain path based on the domain connectivity information. The 201 parent PCE may be requested to provide a end to end path or only the 202 sequence of domains. Child PCE should be able to request 203 synchronized diverse end to end paths from its parent PCE. 205 The new objective function described in this document can be used to 206 maximize diversity when full diverse paths cannot be found. 208 4.3. Domain Diversity 210 As per [I-D.dwpz-pce-domain-diverse]. 212 4.4. Diversity v/s Optimality 214 In case of non-synchronized path computation, PCE may be requested to 215 provide an optimal primary path first and then PCC requests for a 216 backup path with exclusion. Note that this approach does not 217 guarantee diversity comparing to disjoint path computations for 218 primary and backup path in a synchronized manner. 220 A synchronized path computation with diversity flags and/or objective 221 function is used to make sure that both the primary path and the 222 backup path can be computed simultaneously with full diversity or 223 optimized to be as diverse as possible. In the latter case we may 224 sacrifice optimal path for diversity, thus there is a trade-off 225 between the two. 227 An implementation may further choose to analyze the trade-off i.e. it 228 may send multiple request to PCE asking to optimize based on 229 diversity as well as say, cost and make an intelligent choice between 230 them. 232 5. Security Considerations 234 TBD. 236 6. Manageability Considerations 238 6.1. Control of Function and Policy 240 TBD. 242 6.2. Information and Data Models 244 TBD. 246 6.3. Liveness Detection and Monitoring 248 TBD. 250 6.4. Verify Correct Operations 252 TBD. 254 6.5. Requirements On Other Protocols 256 TBD. 258 6.6. Impact On Network Operations 260 TBD. 262 7. IANA Considerations 264 As described in Section 3, three new Objective Functions have been 265 defined. IANA has made the following allocations from the PCEP 266 "Objective Function" sub-registry: 268 Value Description Reference 269 (TBD) MSL [This I.D.] 270 (TBD) MSN [This I.D.] 271 (TBD) MSS [This I.D.] 273 8. Acknowledgments 275 We would like to thank Adrian Farrel for pointing out the need for 276 this document. 278 9. References 279 9.1. Normative References 281 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 282 Requirement Levels", BCP 14, RFC 2119, March 1997. 284 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 285 (PCE) Communication Protocol (PCEP)", RFC 5440, March 286 2009. 288 [RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of 289 Objective Functions in the Path Computation Element 290 Communication Protocol (PCEP)", RFC 5541, June 2009. 292 9.2. Informative References 294 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 295 Element (PCE)-Based Architecture", RFC 4655, August 2006. 297 [RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A 298 Backward-Recursive PCE-Based Computation (BRPC) Procedure 299 to Compute Shortest Constrained Inter-Domain Traffic 300 Engineering Label Switched Paths", RFC 5441, April 2009. 302 [RFC5521] Oki, E., Takeda, T., and A. Farrel, "Extensions to the 303 Path Computation Element Communication Protocol (PCEP) for 304 Route Exclusions", RFC 5521, April 2009. 306 [RFC6006] Zhao, Q., King, D., Verhaeghe, F., Takeda, T., Ali, Z., 307 and J. Meuric, "Extensions to the Path Computation Element 308 Communication Protocol (PCEP) for Point-to-Multipoint 309 Traffic Engineering Label Switched Paths", RFC 6006, 310 September 2010. 312 [RFC6805] King, D. and A. Farrel, "The Application of the Path 313 Computation Element Architecture to the Determination of a 314 Sequence of Domains in MPLS and GMPLS", RFC 6805, November 315 2012. 317 [I-D.dwpz-pce-domain-diverse] 318 Dhody, D., Wu, Q., Palle, U., and X. Zhang, "PCE support 319 for Domain Diversity", draft-dwpz-pce-domain-diverse-00 320 (work in progress), September 2013. 322 Appendix A. Contributor Addresses 324 Xian Zhang 325 Huawei Technologies 326 Bantian, Longgang District 327 Shenzhen 518129 328 P.R.China 330 EMail: zhang.xian@huawei.com 332 Udayasree Palle 333 Huawei Technologies 334 Leela Palace 335 Bangalore, Karnataka 560008 336 INDIA 338 EMail: udayasree.palle@huawei.com 340 Avantika 341 Huawei Technologies 342 Leela Palace 343 Bangalore, Karnataka 560008 344 INDIA 346 EMail: avantika.sushilkumar@huawei.com 348 Authors' Addresses 350 Dhruv Dhody 351 Huawei Technologies 352 Leela Palace 353 Bangalore, Karnataka 560008 354 INDIA 356 EMail: dhruv.ietf@gmail.com 358 Qin Wu 359 Huawei Technologies 360 101 Software Avenue, Yuhua District 361 Nanjing, Jiangsu 210012 362 China 364 EMail: bill.wu@huawei.com