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Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 CCAMP G. Martinelli, Ed. 3 Internet-Draft Cisco 4 Intended status: Informational H. Zhang, Ed. 5 Expires: September 6, 2018 Huawei Technologies 6 G. Galimberti 7 Cisco 8 Y. Lee 9 F. Zhang 10 Huawei Technologies 11 March 5, 2018 13 Information Model for Wavelength Switched Optical Networks (WSONs) with 14 Impairments Validation 15 draft-ietf-ccamp-wson-iv-info-06 17 Abstract 19 This document defines an information model to support Impairment- 20 Aware (IA) Routing and Wavelength Assignment (RWA) functionality. 21 This information model extends the information model for impairment- 22 free RWA process in WSON to facilitate computation of paths where 23 optical impairment constraints need to considered. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on September 6, 2018. 42 Copyright Notice 44 Copyright (c) 2018 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (https://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 60 2. Definitions, Applicability and Properties . . . . . . . . . . 3 61 2.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3 62 2.2. Applicability . . . . . . . . . . . . . . . . . . . . . . 4 63 2.3. Properties . . . . . . . . . . . . . . . . . . . . . . . 5 64 3. ITU-T List of Optical Parameters . . . . . . . . . . . . . . 6 65 4. Background from WSON-RWA Information Model . . . . . . . . . 8 66 5. Optical Impairment Information Model . . . . . . . . . . . . 9 67 5.1. The Optical Impairment Vector . . . . . . . . . . . . . . 10 68 5.2. Node Information . . . . . . . . . . . . . . . . . . . . 10 69 5.2.1. Impairment Matrix . . . . . . . . . . . . . . . . . . 10 70 5.2.2. Impairment Resource Block Information . . . . . . . . 12 71 5.3. Link Information . . . . . . . . . . . . . . . . . . . . 12 72 5.4. Path Information . . . . . . . . . . . . . . . . . . . . 12 73 6. Encoding Considerations . . . . . . . . . . . . . . . . . . . 13 74 7. Control Plane Architectures . . . . . . . . . . . . . . . . . 13 75 7.1. IV-Centralized . . . . . . . . . . . . . . . . . . . . . 14 76 7.2. IV-Distributed . . . . . . . . . . . . . . . . . . . . . 14 77 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 78 9. Contributing Authors . . . . . . . . . . . . . . . . . . . . 14 79 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 80 11. Security Considerations . . . . . . . . . . . . . . . . . . . 15 81 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 82 12.1. Normative References . . . . . . . . . . . . . . . . . . 16 83 12.2. Informative References . . . . . . . . . . . . . . . . . 16 84 Appendix A. FAQ . . . . . . . . . . . . . . . . . . . . . . . . 17 85 A.1. Why the Application Code does not suffice for Optical 86 Impairment Validation? . . . . . . . . . . . . . . . . . 17 87 A.2. Are DWDM network multivendor? . . . . . . . . . . . . . . 18 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 90 1. Introduction 92 In the context of Wavelength Switched Optical Network (WSON), 93 [RFC6163] describes the basic framework for a GMPLS and PCE-based 94 Routing and Wavelength Assignment (RWA) control plane. The 95 associated information model [RFC7446] defines information/parameters 96 required by an RWA process without optical impairment considerations. 98 There are cases of WSON where optical impairments play a significant 99 role and are considered as important constraints. The framework 100 document [RFC6566] defines the problem scope and related control 101 plane architectural options for the Impairment Aware RWA (IA-RWA) 102 operation. Options include different combinations of Impairment 103 Validation (IV) and RWA functions in term of different combination of 104 control plane functions (i.e., PCE, Routing, Signaling). 106 A Control Plane with RWA-IA will not be able to solve the optical 107 impairment problem in a detailed and exhaustive way, however, it may 108 take advantage of some data plane knowledge to make better decisions 109 during its path computing phase. The final outcome will be a path, 110 instantiated through a wavelength in the data plane, that has a 111 "better chance" to work than that path were calculated without IA 112 information. "Better chance" means that path setup may still fail 113 and the GMPLS control plane will follow its usual procedures upon 114 errors and failures. A control plane will not replace a the network 115 design phase that remains a fundamental step for DWDM Optical 116 Networks. As the non-linear impairments which need to be considered 117 in the calculation of an optical path will be vendor-dependent, the 118 parameters considered in this document is not an exhaustive list. 120 This document provides an information model for the impairment aware 121 case to allow the impairment validation function implemented in the 122 control plane or enabled by control plane available information. 123 This model goes in addition to [RFC7446] and shall support any 124 control plane architectural option described by the framework 125 document (see sections 4.2 and 4.3 of [RFC6566]) where a set of 126 combinations of control plane functions vs. IV function is provided. 128 2. Definitions, Applicability and Properties 130 This section provides some concepts to help understand the model and 131 to make a clear separation from data plane definitions (ITU-T 132 recommendations). The first sub-section provides definitions while 133 the Applicability sections uses the defined definitions to scope this 134 document. 136 2.1. Definitions 138 o Computational Model / Optical Computational Model. 139 Defined by ITU standard documents (e.g. [ITU.G680]). In this 140 context we look for models able to compute optical impairments for 141 a given lightpath. 143 o Information Model. 145 Defined by IETF (this document) and provides the set of 146 information required by control plane to apply the Computational 147 Model. 149 o Level of Approximation. 150 This concept refers to the Computational Model as it may compute 151 optical impairment with a certain level of uncertainty. This 152 level is generally not measured but [RFC6566] Section 4.1.1 153 provides a rough classification about it. 155 o Feasible Path. 156 It is the output of the C-SPF with RWA-IV capability. It's an 157 optical path that satisfies optical impairment constraints. The 158 path, instantiated through wavelength(s), may actually work or not 159 work depending of the level of approximation. 161 o Existing Service Disruption. 162 An effect known to optical network designers is the cross- 163 interaction among spectrally adjacent wavelengths: an existing 164 wavelength may experience increased BER due to the setup of an 165 adjacent wavelength. Solving this problem is a typical optical 166 network design activity. Just as an example, a simple solution is 167 adding optical margins (e.g., additional OSNR), although complex 168 and detailed methods exist. 170 o DWDM Line Segments. 171 [ITU.G680] provides definition and picture for the "Situation 1" 172 DWDM Line segments: " Situation 1 - The optical path between two 173 consecutive 3R regenerators is composed of DWDM line segments from 174 a single vendor and OADMs and PXCs from another vendor". Document 175 [RFC6566] Figure 1 shows an LSP composed by two DWDM line segments 176 according to [ITU.G680] definition. 178 2.2. Applicability 180 This document targets at Scenario C defined in [RFC6566] section 181 4.1.1. as approximate impairment estimation. The Approximate 182 concept refer to the fact that this Information Model covers 183 information mainly provided by [ITU.G680] Computational Model. 185 Computational models having no or little approximation, referred as 186 IV-Detailed in the [RFC6566], currently does not exist in term of 187 ITU-T recommendation. They generally deal with non-linear optical 188 impairment and are usually vendor specific. 190 The Information Model defined in this document does not speculate 191 about the mathematical formulas used to fill up information model 192 parameters, hence it does not preclude changing the computational 193 model. At the same time, the authors do not believe this Information 194 Model is exhaustive and if necessary further documents will cover 195 additional models after they become available. 197 The result of RWA-IV process implementing this Information Model is a 198 path (and a wavelength in the data plane) that has better chance to 199 be feasible than if it was computed without any IV function. The 200 Existing Service Disruption, as per the definition above, would still 201 be a problem left to a network design phase. 203 2.3. Properties 205 An information model may have several attributes or properties that 206 need to be defined for each optical parameter made available to the 207 control plane. The properties will help to determine how the control 208 plane can deal with a specific impairment parameter, depending on 209 architectural options chosen within the overall impairment framework 210 [RFC6566]. In some case, properties value will help to identify the 211 level of approximation supported by the IV process. 213 o Time Dependency 214 This identifies how an impairment parameter may vary with time. 215 There could be cases where there is no time dependency, while in 216 other cases there may be need of re-evaluation after a certain 217 time. In this category, variations in impairments due to 218 environmental factors such as those discussed in [ITU.GSUP47] are 219 considered. In some cases, an impairment parameter that has time 220 dependency may be considered as a constant for approximation. In 221 this information model, we do neglect this property. 223 o Wavelength Dependency 224 This property identifies if an impairment parameter can be 225 considered as constant over all the wavelength spectrum of 226 interest or not. Also in this case a detailed impairment 227 evaluation might lead to consider the exact value while an 228 approximation IV might take a constant value for all wavelengths. 229 In this information model, we consider both case: dependency / no 230 dependency on a specific wavelength. This property appears 231 directly in the information model definitions and related 232 encoding. 234 o Linearity 235 As impairments are representation of physical effects, there are 236 some that have a linear behaviour while other are non-linear. 237 Linear approximation is in scope of Scenario C of [RFC6566]. 238 During the impairment validation process, this property implies 239 that the optical effect (or quantity) satisfies the superposition 240 principle, thus a final result can be calculated by the sum of 241 each component. The linearity implies the additivity of optical 242 quantities considered during an impairment validation process. 243 The non-linear effects in general do not satisfy this property. 244 The information model presented in this document however, easily 245 allow introduction of non-linear optical effects with a linear 246 approximated contribution to the linear ones. 248 o Multi-Channel 249 There are cases where a channel's impairments take different 250 values depending on the aside wavelengths already in place, this 251 is mostly due to non-linear impairments. The result would be a 252 dependency among different LSPs sharing the same path. This 253 information model do not consider this kind of property. 255 The following table summarise the above considerations where in the 256 first column reports the list of properties to be considered for each 257 optical parameter, while the second column states if this property is 258 taken into account or not by this information model. 260 +-----------------------+----------------------+ 261 | Property | Info Model Awareness | 262 +-----------------------+----------------------+ 263 | Time Dependency | no | 264 | Wavelength Dependency | yes | 265 | Linearity | yes | 266 | Multi-channel | no | 267 +-----------------------+----------------------+ 269 Table 1: Optical Impairment Properties 271 3. ITU-T List of Optical Parameters 273 As stated by Section 2.2 this Information Model does not intend to be 274 exhaustive and targets an approximate computational model although 275 not precluding future evolutions towards more detailed or different 276 impairments estimation methods. 278 On the same line, ITU SG15/Q6 provides (through [LS78]) a list of 279 optical parameters with following observations: 281 (a) the problem of calculating the non-linear impairments in a 282 multi-vendor environment is not solved. The transfer functions 283 works only for the so called [ITU.G680] "Situation 1". 285 (b) The generated list of parameters is not exhaustive however 286 provide a guideline for control plane optical impairment 287 awareness. 289 In particular, [ITU.G680] contains many parameters that would be 290 required to estimate linear impairments. Some of the Computational 291 Models defined within [ITU.G680] requires parameters defined in 292 other documents like [ITU.G671]. The purpose of the list here below 293 makes this match between the two documents. 295 [ITU.G697] defines parameters can be monitored in an optical network. 296 This Information Model and associated encoding document will reuse 297 [ITU.G697] parameters identifiers and encoding for the purpose of 298 path computation. 300 The list of optical parameters starts from [ITU.G680] Section 9 which 301 provides the optical computational models for the following p: 303 G-1 OSNR. Section 9.1 305 G-2 Chromatic Dispersion (CD). Section 9.2 307 G-3 Polarization Mode Dispersion (PMD). Section 9.3 309 G-4 Polarization Dependent Loss (PDL). Section 9.3 311 In addition to the above, the following list of parameters has been 312 mentioned by [LS78]: 314 L-1 "Channel frequency range", [ITU.G671]. This parameter is part 315 of the application code and encoded through Optical Interface 316 Class as defined in [RFC7446]. 318 L-2 "Modulation format and rate". This parameter is part of the 319 application code and encoded through Optical Interface Class as 320 defined in [RFC7446]. 322 L-3 "Channel power". Required by G-1. 324 L-4 "Ripple". According to [ITU.G680], this parameter can be taken 325 into account as additional OSNR penalty. 327 L-5 "Channel signal-spontaneous noise figure", [ITU.G680]. 328 Required by OSNR calculation (see G-1) above. 330 L-6 "Channel chromatic dispersion (for fibre segment or network 331 element)". Already in G-2 above. 333 L-7 "Channel local chromatic dispersion (for a fibre segment)". 334 Already in G-2 above (since consider both local and fiber 335 dispersions). 337 L-8 "Differential group delay (for a network element)", [ITU.G671]. 338 Required by G-3. 340 L-9 "Polarisation mode dispersion (for a fibre segment)", 341 [ITU.G650.2], [ITU.G680]. Defined above as G-3. 343 L-10 "Polarization dependent loss (for a network element)", 344 [ITU.G671] and [ITU.G680]. Defined above as G-4. 346 L-11 "Reflectance". From [ITU.G671] Section 3.2.2.37 is the ratio 347 of reflected power Pr to incident power Pi at a given port of a 348 passive component, for given conditions of spectral 349 composition, polarization and geometrical distribution. 350 Generally expressed in dB. Might be monitored in some critical 351 cases. We neglect this effect as first approximation. 353 L-12 "Channel Isolation". From [ITU.G671] Section 3.2.2.2 (Adjacent 354 Channel Isolation) and Section 3.2.2.29 (Non Adjacent Channel 355 Isolation). Document [ITU.GSUP39] provide the formula for 356 calculation as channel cross-talk and measure it in dB. This 357 parameterer shall be considered for path computation. 359 L-13 "Channel extinction". From [ITU.G671] Section 3.2.2.9 needed 360 for Interferometric Crosstalk. Document [ITU.GSUP39] has the 361 formula for penalty computation. Unit of measurement is dB. 363 L-14 "Attenuation coefficient (for a fibre segment)". Document 364 [ITU.G650.1] Section 3.6.2. The unit of measure is dB. This 365 is a typical link parameter (as associated to a fiber). 367 L-15 "Non-linear coefficient (for a fibre segment)", [ITU.G650.2]. 368 Required for Non-Linear Optical Impairment Computational 369 Models. Neglected by this document. 371 The final list of parameters is G-1, G-2, G-3, G-4, L-3, L-4, L-5, 372 L-8, L-12, L-13, L-14. 374 4. Background from WSON-RWA Information Model 376 In this section we report terms already defined for the WSON-RWA 377 (impairment free) as in [RFC7446] and [RFC7579]. The purpose is to 378 provide essential information that will be reused or extended for the 379 impairment case. 381 In particular [RFC7446] Section 4.1 defines the ConnectivityMatrix 382 and states that such matrix does not represent any particular 383 internal blocking behaviour but indicates which input ports and 384 wavelengths could possibly be connected to a particular output port. 386 ::= 388 According to [RFC7579], this definition is further detailed as: 390 ::= 391 (( ) ...) 393 This second formula highlights how the ConnectivityMatrix is built by 394 pairs of LinkSet objects identifying the internal connectivity 395 capability due to internal optical node constraint(s). It's 396 essentially binary information and tell if a wavelength or a set of 397 wavelengths can go from an input port to an output port. 399 As an additional note, ConnectivityMatrix belongs to node 400 information, is uniquely identified by advertising node and is a 401 static information. Dynamic information related to the actual state 402 of connections is available through specific extension to link 403 information. 405 The [RFC7446] introduces the concept of ResourceBlockInfo and 406 ResourcePool for the WSON nodes. The resource block is a collection 407 of resources behaving in the same way and having similar 408 characteristics. The ResourceBlockInfo is defined as follow: 410 ::= [] 411 [] [] 413 The usage of resource block and resource pool is an efficient way to 414 model constrains within a WSON node. 416 5. Optical Impairment Information Model 418 The idea behind this document is to put optical impairment parameters 419 into categories and extend the information model already defined for 420 impairment-free WSONs. The three categories are: 422 o Node Information. The concept of connectivity matrix is reused 423 and extended to introduce an impairment matrix, which represents 424 the impairments suffered on the internal path between two ports. 425 In addition, the concept of Resource Block is also reused and 426 extended to provide an efficient representation of per-port 427 impairment. 429 o Link Information representing impairment information related to a 430 specific link or hop. 432 o Path Information representing the impairment information related 433 to the whole path. 435 All the above three categories will make use of a generic container, 436 the Impairment Vector, to transport optical impairment information. 438 This information model however will allow however to add additional 439 parameters beyond the one defined by [ITU.G680] in order to support 440 additional computational models. This mechanism could eventually 441 applicable to both linear and non-linear parameters. 443 This information model makes the assumption that the each optical 444 node in the network is able to provide the control plane protocols 445 with its own parameter values. However, no assumption is made on how 446 the optical nodes get those value information (e.g., internally 447 computed, provisioned by a network management system, etc.). To this 448 extent, the information model intentionally ignores all internal 449 detailed parameters that are used by the formulas of the Optical 450 Computational Model (i.e., "transfer function") and simply provides 451 the object containers to carry results of the formulas. 453 5.1. The Optical Impairment Vector 455 Optical Impairment Vector (OIV) is defined as a list of optical 456 parameters to be associated to a WSON node or a WSON link. It is 457 defined as: 459 ::= ([] ) ... 461 The optional LabelSet object enables wavelength dependency property 462 as per Table 1. LabelSet has its definition in [RFC7579]. 464 OPTICAL_PARAM. This object represents an optical parameter. The 465 Impairment vector can contain a set of parameters as identified by 466 [ITU.G697] since those parameters match the terms of the linear 467 impairments computational models provided by [ITU.G680]. This 468 information model does not speculate about the set of parameters 469 (since defined elsewhere, e.g. ITU-T), however it does not preclude 470 extensions by adding new parameters. 472 5.2. Node Information 474 5.2.1. Impairment Matrix 476 Impairment matrix describes a list of the optical parameters that 477 applies to a network element as a whole or ingress/egress port pairs 478 of a network element. Wavelength dependency property of optical 479 parameters is also considered. 481 ImpairmentMatrix ::= 482 (( ) ...) 484 Where: 486 MatrixID. This ID is a unique identifier for the matrix. It 487 shall be unique in scope among connectivity matrices defined in 488 [RFC7446] and impairment matrices defined here. 490 ConnType. This number identifies the type of matrix and it shall 491 be unique in scope with other values defined by impairment-free 492 WSON documents. 494 LinkSet. Same object definition and usage as [RFC7579]. The 495 pairs of LinkSet identify one or more internal node constrain. 497 OIV. The Optical Impairment Vector defined above. 499 The model can be represented as a multidimensional matrix shown in 500 the following picture 502 _________________________________________ 503 / / / / / /| 504 / / / / / / | 505 /________/_______/_______/_______/_______/ | 506 / / / / / /| /| 507 / / / / / / | | 508 /________/_______/_______/_______/_______/ | /| 509 / / / / / /| /| | 510 / / / / / / | | /| 511 /________/_______/_______/_______/_______/ | /| | 512 / / / / / /| /| | /| 513 / / / / / / | | /| | 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | /| | / PDL 515 | - | | | | | /| | /|/ 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | /| / 517 | | - | | | | /| | / PND 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | /|/ 519 | | | - | | | /| / 520 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | / Chr.Disp. 521 | | | | - | | /|/ 522 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ / 523 | | | | | - | / OSNR 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 525 527 The connectivity matrix from [RFC7579] is only a two dimensional 528 matrix, containing only binary information, through the LinkSet 529 pairs. In this model, a third dimension is added by generalizing the 530 binary information through the Optical Impairment Vector associated 531 with each LinkSet pair. Optical parameters in the picture are 532 reported just as an example: proper list and encoding shall be 533 defined by other documents. 535 This representation shows the most general case however, the total 536 amount of information transported by control plane protocols can be 537 greatly reduced by proper encoding when the same set of values apply 538 to all LinkSet pairs. 540 5.2.2. Impairment Resource Block Information 542 This information model reuses the definition of Resource Block 543 Information adding the associated impairment vector. 545 ResourceBlockInfo ::= [] 546 [] [] [] 548 The object ResourceBlockInfo is than used as specified within 549 [RFC7446]. 551 5.3. Link Information 553 For the list of optical parameters associated to the link, the same 554 approach used for the node-specific impairment information can be 555 applied. The link-specific impairment information is extended from 556 [RFC7446] as the following: 558 ::= 559 [] [] 561 DynamicLinkInfo is already defined in [RFC7446] while OIV is the 562 Optical Impairment Vector is defined in the previous section. 564 5.4. Path Information 566 There are cases where the optical impairments can only be described 567 as a constrains on the overall end to end path. In such case, the 568 optical impairment and/or parameter, cannot be derived (using a 569 simple function) from the set of node / link contributions. 571 An equivalent case is the option reported by [RFC6566] on IV- 572 Candidate paths where, the control plane knows a list of optically 573 feasible paths so a new path setup can be selected among that list. 574 Independent from the protocols and functions combination (i.e. RWA 575 vs. Routing vs. PCE), the IV-Candidates imply a path property stating 576 that a path is optically feasible. 578 The concept of Optical Impairment Vector (OIV) might be used or 579 extended to report optical impairment information at path level 580 however this is case is letf for future studies. 582 6. Encoding Considerations 584 Details about encoding will be defined in a separate document 585 [I-D.martinelli-ccamp-wson-iv-encode] however worth remembering that, 586 within [ITU.G697] Appending V, ITU already provides a guideline for 587 encoding some optical parameters. 589 In particular [ITU.G697] indicates that each parameter shall be 590 represented by a 32 bit floating point number. 592 Values for optical parameters are provided by optical node and it 593 could provide by direct measurement or from some internal computation 594 starting from indirect measurement. In such cases, it could be 595 useful to understand the variance associated with the value of the 596 optical parameter hence, the encoding shall provide the possibility 597 to include a variance as well. 599 This kind of information will enable IA-RWA process to make some 600 additional considerations on wavelength feasibility. [RFC6566] 601 Section 4.1.3 reports some considerations regarding this degree of 602 confidence during the impairment validation process. 604 7. Control Plane Architectures 606 This section briefly describes how the definitions contained in this 607 information model will match the architectural options described by 608 [RFC6566]. This section does not suggest suggested any specific 609 protocol option. 611 The assumption is that WSON GMPLS extensions are available and 612 operational. To such extent, the WSON-RWA will provide the following 613 information through its path computation (and RWA process): 615 o The wavelengths connectivity, considering also the connectivity 616 constraints limited by reconfigurable optics, and wavelengths 617 availability. 619 o The interface compatibility at the physical level. 621 o The Optical-Elettro-Optical (OEO) availability within the network 622 (and related physical interface compatibility). As already stated 623 by the framework this information it's very important for 624 impairment validation: 626 A. If the IV functions fail (path optically infeasible), the path 627 computation function may use an available OEO point to find a 628 feasible path. In normally operated networks OEO are mainly 629 uses to support optically unfeasible path than mere wavelength 630 conversion. 632 B. The OEO points reset the optical impairment information since 633 a new light is generated. 635 7.1. IV-Centralized 637 Centralized IV process is performed by a single entity (e.g. a PCE or 638 other external entities). Given sufficient impairment information, 639 it can either be used to provide a list of paths between two nodes, 640 which are valid in terms of optical impairments. Alternatively, it 641 can help validate whether a particular selected path and wavelength 642 is feasible or not. 644 Centralized IV functions requires exchange of impairment information 645 to the entity performing the IV process from network nodes. This 646 information exchange may requires implementation of this information 647 model within an exsting protocol (i.e. routing procol vs PCEP vs BGP- 648 LS vs others). 650 7.2. IV-Distributed 652 Assuming the information model is implemented through a routing 653 protocol, every node in the WSON network shall be able to perform an 654 RWA-IV function. 656 The signalling phase may provide additional checking as others 657 traffic engineering parameters. 659 8. Acknowledgements 661 Authors would like to acknoledge Greg Bernstein and Moustafa Kattan 662 as authors of a previous similar draft whose content partially 663 converged here. 665 Authors would like to thank ITU SG15/Q6 and in particular Peter 666 Stassar and Pete Anslow for providing useful information and text to 667 CCAMP through join meetings and liaisons. 669 9. Contributing Authors 671 This document was the collective work of several authors. The text 672 and content of this document was contributed by the editors and the 673 co-authors listed below: 675 Xian Zhang 676 Huawei Technologies 677 F3-5-B R&D Center, Huawei Base 678 Bantian, Longgang District 679 Shenzen 518129 680 P.R. China 682 Phone: +86 755 28972913 683 Email: zhang.xian@huawei.com 685 Domenico Siracusa 686 CREATE-NET 687 via alla Cascata 56/D, Povo 688 Trento 38123 689 Italy 691 Email: domenico.siracusa@create-net.org 693 Andrea Zanardi 694 CREATE-NET 695 via alla Cascata 56/D, Povo 696 Trento 38123 697 Italy 699 Email: andrea.zanardi@create-net.org 701 Federico Pederzolli 702 CREATE-NET 703 via alla Cascata 56/D, Povo 704 Trento 38123 705 Italy 707 Email: federico.perderzolli@create-net.org 709 10. IANA Considerations 711 This document does not contain any IANA requirement. 713 11. Security Considerations 715 This document defines an information model for impairments in optical 716 networks. If such a model is put into use within a network it will 717 by its nature contain details of the physical characteristics of an 718 optical network. Such information would need to be protected from 719 intentional or unintentional disclosure. 721 12. References 723 12.1. Normative References 725 [ITU.G650.1] 726 International Telecommunications Union, "Transmission 727 media and optical systems characteristics - Optical fibre 728 cable", ITU-T Recommendation G.650.1, July 2010. 730 [ITU.G650.2] 731 International Telecommunications Union, "Definitions and 732 test methods for statistical and non-linear related 733 attributes of single-mode fibre and cable", 734 ITU-T Recommendation G.650.2, August 2015. 736 [ITU.G671] 737 International Telecommunications Union, "Transmission 738 characteristics of optical components and subsystems", 739 ITU-T Recommendation G.671, February 2012. 741 [ITU.G680] 742 International Telecommunications Union, "Physical transfer 743 functions of optical network elements", 744 ITU-T Recommendation G.680, July 2007. 746 [ITU.G697] 747 International Telecommunications Union, "Optical 748 monitoring for dense wavelength division multiplexing 749 systems", ITU-T Recommendation G.697, February 2012. 751 [ITU.GSUP39] 752 International Telecommunications Union, "Optical System 753 Design and Engineering Considerations", 754 ITU-T Recommendation G. Supplement 39, September 2012. 756 [ITU.GSUP47] 757 International Telecommunications Union, "General aspects 758 of optical fibres and cables", ITU-T Recommendation G. 759 Supplement 47, September 2012. 761 12.2. Informative References 763 [I-D.martinelli-ccamp-wson-iv-encode] 764 Martinelli, G., Zhang, X., Galimberti, G., Lee, Y., and F. 765 Zhang, "Information Encoding for WSON with Impairments 766 Validation", draft-martinelli-ccamp-wson-iv-encode-09 767 (work in progress), February 2018. 769 [LS78] International Telecommunications Union SG15/Q6, "LS/s on 770 CCAMP Liaison to ITU-T SG15 Q6 and Q12 on WSON", 771 LS https://datatracker.ietf.org/liaison/1288/, October 772 2013. 774 [RFC6163] Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku, 775 "Framework for GMPLS and Path Computation Element (PCE) 776 Control of Wavelength Switched Optical Networks (WSONs)", 777 RFC 6163, DOI 10.17487/RFC6163, April 2011, 778 . 780 [RFC6566] Lee, Y., Ed., Bernstein, G., Ed., Li, D., and G. 781 Martinelli, "A Framework for the Control of Wavelength 782 Switched Optical Networks (WSONs) with Impairments", 783 RFC 6566, DOI 10.17487/RFC6566, March 2012, 784 . 786 [RFC7446] Lee, Y., Ed., Bernstein, G., Ed., Li, D., and W. Imajuku, 787 "Routing and Wavelength Assignment Information Model for 788 Wavelength Switched Optical Networks", RFC 7446, 789 DOI 10.17487/RFC7446, February 2015, 790 . 792 [RFC7579] Bernstein, G., Ed., Lee, Y., Ed., Li, D., Imajuku, W., and 793 J. Han, "General Network Element Constraint Encoding for 794 GMPLS-Controlled Networks", RFC 7579, 795 DOI 10.17487/RFC7579, June 2015, 796 . 798 Appendix A. FAQ 800 A.1. Why the Application Code does not suffice for Optical Impairment 801 Validation? 803 Application Codes are encoded within GMPLS WSON protocol through the 804 Optical Interface Class as defined in [RFC7446]. 806 The purpose of the Application Code in RWA is simply to assess the 807 interface compatibility: same Application Code means that two 808 interfaces can have an LSP connecting the two. 810 Application Codes contain other information useful for IV process 811 (e.g., see the list of parameters) so they are required however 812 Computational Models requires more parameteres to assess the path 813 feasibility. 815 A.2. Are DWDM network multivendor? 817 According to [ITU.G680] "Situation 1" the DWDM line segments are 818 single are single vendor but an LSP can make use of different data 819 planes entities from different vendors. For example: DWDM interfaces 820 (represented in the control plane through the Optical Interface 821 Class) from a vendor and network elements described by Stutation 1 822 from another vendor. 824 Authors' Addresses 826 Giovanni Martinelli (editor) 827 Cisco 828 via Santa Maria Molgora, 48/C 829 Vimercate, MB 20871 830 Italy 832 Phone: +39 039 2092044 833 Email: giomarti@cisco.com 835 Haomian Zhang (editor) 836 Huawei Technologies 837 F3 R&D Center, Huawei Base 838 Bantian, Longgang District 839 Shenzen 518129 840 P.R. China 842 Phone: +86 755 28972465 843 Email: zhenghaomian@huawei.com 845 Gabriele M. Galimberti 846 Cisco 847 Via Santa Maria Molgora, 48/C 848 Vimercate, MB 20871 849 Italy 851 Phone: +39 039 2091462 852 Email: ggalimbe@cisco.com 853 Young Lee 854 Huawei Technologies 855 1700 Alma Drive, Suite 100 856 Plano, TX 75075 857 U.S.A 859 Email: ylee@huawei.com 861 Fatai Zhang 862 Huawei Technologies 863 F3-5-B R&D Center, Huawei Base 864 Bantian, Longgang District 865 Shenzen 518129 866 P.R. China 868 Email: zhang.fatai@huawei.com