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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group G. Bernstein 2 Internet Draft Grotto Networking 3 Y. Lee 4 D. Li 5 Huawei 6 G. Martinelli 7 Cisco 8 Intended status: Informational May 5, 2009 9 Expires: November 2009 11 A Framework for the Control of Wavelength Switched Optical Networks 12 (WSON) with Impairments 13 draft-bernstein-ccamp-wson-impairments-05.txt 15 Status of this Memo 17 This Internet-Draft is submitted to IETF in full conformance with the 18 provisions of BCP 78 and BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF), its areas, and its working groups. Note that 22 other groups may also distribute working documents as Internet- 23 Drafts. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 The list of current Internet-Drafts can be accessed at 31 http://www.ietf.org/ietf/1id-abstracts.txt 33 The list of Internet-Draft Shadow Directories can be accessed at 34 http://www.ietf.org/shadow.html 36 This Internet-Draft will expire on October 5, 2009. 38 Copyright Notice 40 Copyright (c) 2009 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents in effect on the date of 45 publication of this document (http://trustee.ietf.org/license-info). 46 Please review these documents carefully, as they describe your rights 47 and restrictions with respect to this document. 49 Abstract 51 The operation of optical networks requires information on the 52 physical characterization of optical network elements, subsystems, 53 devices, and cabling. These physical characteristics may be important 54 to consider when using a GMPLS control plane to support path setup 55 and maintenance. This document discusses how the definition and 56 characterization of optical fiber, devices, subsystems, and network 57 elements contained in various ITU-T recommendations can be combined 58 with GMPLS control plane protocols and mechanisms to support 59 Impairment Aware Routing and Wavelength Assignment (IA-RWA) in 60 optical networks. 62 Table of Contents 64 1. Introduction...................................................3 65 2. Motivation.....................................................4 66 3. Impairment Aware Optical Path Computation......................5 67 3.1. Optical Network Requirements and Constraints..............5 68 3.1.1. Categories of Impairment Aware Computation...........5 69 3.1.2. Impairment Computation and Information Sharing 70 Constraints.................................................6 71 3.1.3. Impairment Estimation Functional Blocks..............8 72 3.2. IA-RWA Computing and Control Plane Architectures..........9 73 3.2.1. Combined Routing, WA, and IV........................10 74 3.2.2. Separate Routing, WA, or IV.........................10 75 3.2.3. Distributed WA and/or IV............................11 76 3.3. Mapping Network Requirements to Architectures............11 77 4. Protocol Implications.........................................14 78 4.1. Information Model for Impairments........................14 79 4.1.1. Properties of an Impairment Information Model.......15 80 4.2. Routing..................................................16 81 4.3. Signaling................................................16 82 4.4. PCE......................................................17 83 4.4.1. Combined IV & RWA...................................17 84 4.4.2. IV-Candidates + RWA.................................17 85 4.4.3. Approximate IA-RWA + Separate Detailed IV...........19 86 5. Security Considerations.......................................21 87 6. IANA Considerations...........................................21 88 7. Acknowledgments...............................................21 89 APPENDIX A: Overview of Optical Layer ITU-T Recommendations......22 90 A.1. Fiber and Cables.........................................22 91 A.2. Devices..................................................23 92 A.2.1. Optical Amplifiers..................................23 93 A.2.2. Dispersion Compensation.............................24 94 A.2.3. Optical Transmitters................................25 95 A.2.4. Optical Receivers...................................25 96 A.3. Components and Subsystems................................26 97 A.4. Network Elements.........................................27 98 8. References....................................................29 99 8.1. Normative References.....................................29 100 8.2. Informative References...................................31 101 Author's Addresses...............................................31 102 Intellectual Property Statement..................................33 103 Disclaimer of Validity...........................................33 105 1. Introduction 107 As an optical signal progresses along its path it may be altered by 108 the various physical processes in the optical fibers and devices it 109 encounters. When such alterations result in signal degradation, we 110 usually refer to these processes as "impairments". An overview of 111 some critical optical impairments and their routing (path selection) 112 implications can be found in [RFC4054]. Roughly speaking, optical 113 impairments accumulate along the path (without 3R regeneration) 114 traversed by the signal. They are influenced by the type of fiber 115 used, the types and placement of various optical devices and the 116 presence of other optical signals that may share a fiber segment 117 along the signal's path. The degradation of the optical signals due 118 to impairments can result in unacceptable bit error rates or even a 119 complete failure to demodulate and/or detect the received signal. 120 Therefore, path selection in any WSON requires consideration of 121 optical impairments so that the signal will be propagated from the 122 network ingress point to the egress point with an acceptable signal 123 quality. 125 Some optical subnetworks are designed such that over any path the 126 degradation to an optical signal due to impairments never exceeds 127 prescribed bounds. This may be due to the limited geographic extent 128 of the network, the network topology, and/or the quality of the 129 fiber and devices employed. In such networks the path selection 130 problem reduces to determining a continuous wavelength from source 131 to destination (the Routing and Wavelength Assignment problem). 132 These networks are discussed in [WSON-Frame]. In other optical 133 networks, impairments are important and the path selection process 134 must be impairment-aware. 136 Although [RFC4054] describes a number of key optical impairments, a 137 more complete description of optical impairments and processes can be 138 found in the ITU-T Recommendations. Appendix A of this document 139 provides an overview of the extensive ITU-T documentation in this 140 area. 142 The benefits of operating networks using the Generalized 143 Multiprotocol Label Switching (GMPLS) control plane is described in 144 [RFC3945]. The advantages of using a path computation element (PCE) 145 to perform complex path computations are discussed in [RFC4655]. 147 Based on the existing ITU-T standards covering optical 148 characteristics (impairments) and the knowledge of how the impact of 149 impairments may be estimated along a path, this document provides a 150 framework for impairment aware path computation and establishment 151 utilizing GMPLS protocols and the PCE architecture. As in the 152 impairment free case covered in [WSON-Frame], a number of different 153 control plane architectural options are described. 155 2. Motivation 157 There are deployment scenarios for WSON networks where not all 158 possible paths will yield suitable signal quality. There are 159 multiple reasons behind this choice; here below is a non-exhaustive 160 list of examples: 162 o WSON is evolving using multi-degree optical cross connects in a 163 way that network topologies are changing from rings (and 164 interconnected rings) to a full mesh. Adding network equipment 165 such as amplifiers or regenerators, to make all paths feasible, 166 leads to an over-provisioned network. Indeed, even with over 167 provisioning, the network could still have some infeasible paths. 169 o Within a given network, the optical physical interface may change 170 over the network life, e.g., the optical interfaces might be 171 upgraded to higher bit-rates. Such changes could result in paths 172 being unsuitable for the optical signal. Although the same 173 considerations may apply to other network equipment upgrades, the 174 optical physical interfaces are a typical case because they are 175 typically provisioned at various stages of the network's life span 176 as needed by traffic demands. 178 o There are cases where a network is upgraded by adding new optical 179 cross connects to increase network flexibility. In such cases 180 existing paths will have their feasibility modified while new 181 paths will need to have their feasibility assessed. 183 Not having an impairment aware control plane for such networks will 184 require a more complex network design phase that has to also take 185 into account evolving network status in term of equipments and 186 traffic. Moreover, network operations such as path establishment, 187 will require significant pre-design via non-control plane processes 188 resulting in significantly slower network provisioning. 190 3. Impairment Aware Optical Path Computation 192 The basic criteria for path selection is whether one can successfully 193 transmit the signal from a transmitter to a receiver within a 194 prescribed error tolerance, usually specified as a maximum 195 permissible bit error ratio (BER). This generally depends on the 196 nature of the signal transmitted between the sender and receiver and 197 the nature of the communications channel between the sender and 198 receiver. The optical path utilized (along with the wavelength) 199 determines the communications channel. 201 The optical impairments incurred by the signal along the fiber and at 202 each optical network element along the path determine whether the BER 203 performance or any other measure of signal quality can be met for a 204 signal on a particular end-to-end path. 206 3.1. Optical Network Requirements and Constraints 208 This section examines the various optical network requirements and 209 constraints that an impairment aware optical control plane may have 210 to operate under. These requirements and constraints motivate the IA- 211 RWA architectural alternatives to be presented in the following 212 section. We can break the different optical networks contexts up 213 along two main criteria: (a) the accuracy required in the estimation 214 of impairment effects, and (b) the constraints on the impairment 215 estimation computation and/or sharing of impairment information. 217 3.1.1. Categories of Impairment Aware Computation 219 A. No concern for impairments or Wavelength Continuity Constraints 221 This situation is covered by existing GMPLS with local wavelength 222 (label) assignment. 224 B. No concern for impairments but Wavelength Continuity Constraints 226 This situation is applicable to networks designed such that every 227 possible path is valid for the signal types permitted on the network. 228 In this case impairments are only taken into account during network 229 design and after that, for example during optical path computation, 230 they can be ignored. This is the case discussed in [WSON-Frame] where 231 impairments may be ignored by the control plane. 233 C. Approximated Impairment Estimation 235 This situation is applicable to networks in which impairment effects 236 need to be considered but there is sufficient margin such that they 237 can be estimated via approximation techniques such as link budgets 238 and dispersion[G.680],[G.sup39]. The viability of optical paths for a 239 particular class of signals can be estimated using well defined 240 approximation techniques [G.680], [G.sup39]. Also, adding or removing 241 an optical signal on the path will not render any of the existing 242 signals in the network as non-viable. For example, one form of non- 243 viability is the occurrence of transients in existing links of 244 sufficient magnitude to impact the BER of those existing signals. 246 Much work at ITU-T has gone into developing impairment models at this 247 and more detailed levels. Impairment characterization of network 248 elements could then may be used to calculate which paths are 249 conformant with a specified BER for a particular signal type. In such 250 a case, we can combine the impairment aware (IA) path computation 251 with the RWA process to permit more optimal IA-RWA computations. 252 Note, the IA path computation may also take place in a separate 253 entity, i.e., a PCE. 255 D. Detailed Impairment Computation 257 This situation is applicable to networks in which impairment effects 258 must be more accurately computed. For these networks, a full 259 computation and evaluation of the impact to any existing paths needs 260 to be performed prior to the addition of a new path. This scenario is 261 outside the scope of this document. 263 3.1.2. Impairment Computation and Information Sharing Constraints 265 In GMPLS, information used for path computation is standardized for 266 distribution amongst the elements participating in the control plane 267 and any appropriately equipped PCE can perform path computation. For 268 optical systems this may not be possible. This is typically due to 269 only portions of an optical system being subject to standardization. 270 In ITU-T recommendations [G.698.1] and [G.698.2] which specify single 271 channel interfaces to multi-channel DWDM systems only the single 272 channel interfaces (transmit and receive) are specified while the 273 multi-channel links are not standardized. These DWDM links are 274 referred to as "black links" since their details are not generally 275 available. Note however the overall impact of a black link at the 276 single channel interface points typically can be characterized 277 [G.698.1] and [G.698.2]. 279 Typically a vendor might use proprietary impairment models for DWDM 280 spans and to estimate the validity of optical paths. For example, 281 models of optical nonlinearities are not currently standardized. 282 Vendors may also choose not to publish impairment details for links 283 or a set of network elements in order not to divulge their optical 284 system designs. 286 In general, the impairment estimation/validation of an optical path 287 for optical networks with "black links" (path) could not be performed 288 by a general purpose impairment aware (IA) computation entity since 289 it would not have access to or understand the "black link" impairment 290 parameters. However, impairment estimation (optical path validation) 291 but could be performed by a vendor specific impairment aware 292 computation entity. Such a vendor specific IA computation, could 293 utilize standardized impairment information imported from other 294 network elements in these proprietary computations. In section 3.2. 296 In the following we will use the term "black links" to describe these 297 computation and information sharing constraints in optical networks. 298 From the control plane perspective we have the following options: 300 A. The vendor in control of the "black links" can furnish a list of 301 all viable paths between all viable node pairs to a computational 302 entity. This information would be particularly useful as an input 303 to RWA optimization to be performed by another computation entity. 304 The difficulty here is for larger networks such a list of paths 305 along with any wavelength constraints could get unmanageably 306 large. 308 B. The vendor in control of the "black links" could furnish a PCE 309 like entity that would furnish a list of viable paths/wavelengths 310 between two requested nodes. This is useful as an input to RWA 311 optimizations and can reduce the scaling issue previously 312 mentioned. Such a PCE like entity would not need to perform a full 313 RWA computation, i.e., it would not need to take into account 314 current wavelength availability on links. Such an approach may 315 require PCEP extensions for both the request and response 316 information. 318 C. The vendor in control of the "black links" can furnish a PCE that 319 performs full IA-RWA services. The difficulty is this requires the 320 one vendor to also become the sole source of all RWA optimization 321 algorithms and such. 323 In all the above cases it would be the responsibility of the vendor 324 in control of the "black links" to import the shared impairment 325 information from the other NEs via the control plane or other means 326 as necessary. 328 3.1.3. Impairment Estimation Functional Blocks 330 The Impairment Estimation process can be modeled by the following 331 functional blocks. These blocks are independent of any Control Plane 332 architecture, that is, they can be implemented by the same or by 333 different control plane functional blocks. 335 +-----------------+ 336 +------------+ +-----------+ | +------------+ | 337 | | | | | | | | 338 | Optical | | Optical | | | Optical | | 339 | Interface |------->| Path |--->| | Channel | | 340 | (Transmit/ | | | | | Estimation | | 341 | Receive) | | | | | | | 342 +------------+ +-----------+ | +------------+ | 343 | || | 344 | || | 345 | Estimation | 346 | || | 347 | \/ | 348 | +------------+ | 349 | | BER / | | 350 | | Q Factor | | 351 | +------------+ | 352 +-----------------+ 354 Starting from functional block on the left the Optical Interface 355 represents where the optical signal is transmitted or received and 356 defines the properties at the end points path. For WSON even the case 357 with no IA has to consider a minimum set of interface 358 characteristics. As an example, the document [G.698.1] reports the 359 full set of those parameters for certain interfaces. In this function 360 only a significant subset of those parameters would be considered. In 361 addition transmit and receive interface might consider a different 362 subset of properties. 364 The block "Optical Path" represents all kinds of impairments 365 affecting a wavelength as it traverses the networks through links and 366 nodes. In the case where the control plane has no IA this block will 367 not be present. Otherwise, this function must be implemented in some 368 way via the control plane. Options for this will be given in the next 369 section on control plane architectural alternatives. 371 The last block implements the decision function for path feasibility. 372 Depending on the IA level of approximation this function can be more 373 or less complex. For example in case of no IA only the signal class 374 compatibility will be verified. 376 3.2. IA-RWA Computing and Control Plane Architectures 378 From a control plane point of view optical impairments are additional 379 constraints to the impairment-free RWA process described in [WSON- 380 Frame]. In impairment aware routing and wavelength assignment (IA- 381 RWA), there are conceptually three general classes of processes to be 382 considered: Routing (R), Wavelength Assignment (WA), and Impairment 383 Validation (estimation) (IV). 385 Impairment validation may come in many forms, and maybe invoked at 386 different levels of detail in the IA-RWA process. From a process 387 point of view we will consider the following three forms of 388 impairment validation: 390 o IV-Candidates 392 In this case an Impairment Validation (IV) process furnishes a set of 393 paths between two nodes along with any wavelength restrictions such 394 that the paths are valid with respect to optical impairments. These 395 paths and wavelengths may not be actually available in the network 396 due to its current usage state. This set of paths would be returned 397 in response to a request for a set of at most K valid paths between 398 two specified nodes. Note that such a process never directly 399 discloses optical impairment information. 401 o IV-Detailed Verification 403 In this case an IV process is given a particular path and wavelength 404 through an optical network and is asked to verify whether the overall 405 quality objectives for the signal over this path can be met. Note 406 that such a process never directly discloses optical impairment 407 information. 409 o IV-Distributed 411 In this distributed IV process impairment approximate degradation 412 measures such as OSNR, dispersion, DGD, etc. are accumulated along 413 the path via a signaling like protocol. When the accumulated measures 414 reach the destination node a decision on the impairment validity of 415 the path can be made. Note that such a process would entail revealing 416 an individual network element's impairment information. 418 The following subsections present three major classes of IA-RWA path 419 computation architectures and their respective advantages and 420 disadvantages. 422 3.2.1. Combined Routing, WA, and IV 424 From the point of view of optimality, the "best" IA-RWA solutions can 425 be achieved if the path computation entity (PCE) can 426 conceptually/algorithmically combine the processes of routing, 427 wavelength assignment and impairment validation. 429 Such a combination can take place if the PCE is given: (a) the 430 impairment-free WSON network information as discussed in [WSON-Frame] 431 and (b) impairment information to validate potential paths. 433 3.2.2. Separate Routing, WA, or IV 435 Separating the processes of routing, WA and/or IV can reduce the need 436 for sharing of different types of information used in path 437 computation. This was discussed for routing separate from WA in 438 [WSON-Frame]. In addition, as will be discussed in the section on 439 network contexts some impairment information may not be shared and 440 this may lead to the need to separate IV from RWA. In addition, as 441 also discussed in the section on network contexts, if IV needs to be 442 done at a high level of precision it may be advantageous to offload 443 this computation to a specialized server. 445 The following conceptual architectures belong in this general 446 category: 448 o R+WA+IV -- separate routing, wavelength assignment, and impairment 449 validation. 451 o R + (WA & IV) -- routing separate from a combined wavelength 452 assignment and impairment validation process. Note that impairment 453 validation is typically wavelength dependent hence combining WA 454 with IV can lead to efficiencies. 456 o (RWA)+IV - combined routing and wavelength assignment with a 457 separate impairment validation process. 459 Note that the IV process may come before or after the RWA processes. 460 If RWA comes first then IV is just rendering a yes/no decision on the 461 selected path and wavelength. If IV comes first it would need to 462 furnish a list of possible (valid with respect to impairments) routes 463 and wavelengths to the RWA processes. 465 3.2.3. Distributed WA and/or IV 467 In the non-impairment RWA situation [WSON-Frame] it was shown that a 468 distributed wavelength assignment (WA) process carried out via 469 signaling can eliminate the need to distribute wavelength 470 availability information via an IGP. A similar approach can allow for 471 the distributed computation of impairment effects and avoid the need 472 to distribute impairment characteristics of network elements and 473 links via route protocols or by other means. An example of such an 474 approach is given in [Martinelli] and utilizes enhancements to RSVP 475 signaling to carry accumulated impairment related information. 477 A distributed impairment validation for a prescribed network path 478 requires that the effects of impairments can be calculated by 479 approximate models with cumulative quality measures such as those in 480 [G.680]. 482 For such a system to be interoperable the various impairment measures 483 to be accumulated would need to be agreed upon. Section 9 of [G.680] 484 can be useful in deriving such cumulative measures but doesn't 485 explicitly state how a distributed computation would take place. For 486 example in the computation of the optical signal to noise ratio along 487 a path (see equation 9-3 of [G.680]) one could accumulate the linear 488 sum terms and convert to the optical signal to noise ratio (OSNR) in 489 (dBs) at the destination or one could convert in and out of the OSNR 490 in (dBs) at each intermediate point along the path. 492 If distributed WA is being done at the same time as distributed IV 493 then we may need to accumulate impairment related information for all 494 wavelengths that could be used. This is somewhat winnowed down as 495 potential wavelengths are discovered to be in use, but could be a 496 significant burden for lightly loaded high channel count networks. 498 3.3. Mapping Network Requirements to Architectures 500 In Figure 1 we show process flows for three main architectural 501 alternatives to IA-RWA when approximate impairment validation 502 suffices. In Figure 2 we show process flows for two main 503 architectural alternatives when detailed impairment verification is 504 required. 506 +-----------------------------------+ 507 | +--+ +-------+ +--+ | 508 | |IV| |Routing| |WA| | 509 | +--+ +-------+ +--+ | 510 | | 511 | Combined Processes | 512 +-----------------------------------+ 513 (a) 515 +--------------+ +----------------------+ 516 | +----------+ | | +-------+ +--+ | 517 | | IV | | | |Routing| |WA| | 518 | |candidates| |----->| +-------+ +--+ | 519 | +----------+ | | Combined Processes | 520 +--------------+ +----------------------+ 521 (b) 523 +-----------+ +----------------------+ 524 | +-------+ | | +--+ +--+ | 525 | |Routing| |------->| |WA| |IV| | 526 | +-------+ | | +--+ +--+ | 527 +-----------+ | Distributed Processes| 528 +----------------------+ 529 (c) 530 Figure 1 Process flows for the three main approximate impairment 531 architectural alternatives. 533 The advantages, requirements and suitability of these options are as 534 follows: 536 o Combined IV & RWA process 538 This alternative combines RWA and IV within a single computation 539 entity enabling highest potential optimality and efficiency in IA- 540 RWA. This alternative requires that the computational entity knows 541 impairment information as well as non-impairment RWA information. 542 This alternative can be used with "black links", but would then need 543 to be provided by the vendor controlling the "black links". 545 o IV-Candidates + RWA process 547 This alternative allows separation of impairment information into two 548 computational entities while still maintaining a high degree of 549 potential optimality and efficiency in IA-RWA. The candidates IV 550 process needs to know impairment information from all optical network 551 elements, while the RWA process needs to know non-impairment RWA 552 information from the network elements. This alternative can be used 553 with "black links", but the vendor in control of the "black links" 554 would need to provide the functionality of the IV-candidates process. 555 Note that this is still very useful since the algorithmic areas of IV 556 and RWA are very different and prone to specialization. 558 o Routing + Distributed WA and IV 560 In this alternative a signaling protocol is extended and leveraged in 561 the wavelength assignment and impairment validation processes. 562 Although this doesn't enable as high a potential degree of optimality 563 of optimality as (a) or (b), it does not require distribution of 564 either link wavelength usage or link/node impairment information. 565 Note that this is most likely not suitable for "black links". 567 +-----------------------------------+ +------------+ 568 | +-----------+ +-------+ +--+ | | +--------+ | 569 | | IV | |Routing| |WA| | | | IV | | 570 | |approximate| +-------+ +--+ |---->| |Detailed| | 571 | +-----------+ | | +--------+ | 572 | Combined Processes | | | 573 +-----------------------------------+ +------------+ 574 (a) 576 +--------------+ +----------------------+ +------------+ 577 | +----------+ | | +-------+ +--+ | | +--------+ | 578 | | IV | | | |Routing| |WA| |---->| | IV | | 579 | |candidates| |----->| +-------+ +--+ | | |Detailed| | 580 | +----------+ | | Combined Processes | | +--------+ | 581 +--------------+ +----------------------+ | | 582 (b) +------------+ 583 Figure 2 Process flows for the two main detailed impairment 584 validation architectural options. 586 The advantages, requirements and suitability of these detailed 587 validation options are as follows: 589 o Combined approximate IV & RWA + Detailed-IV 591 This alternative combines RWA and approximate IV within a single 592 computation entity enabling highest potential optimality and 593 efficiency in IA-RWA; then has a separate entity performing detailed 594 impairment validation. In the case of "black links" the vendor 595 controlling the "black links" would need to provide all 596 functionality. 598 o Candidates-IV + RWA + Detailed-IV 600 This alternative allows separation of approximate impairment 601 information into a computational entity while still maintaining a 602 high degree of potential optimality and efficiency in IA-RWA; then a 603 separate computation entity performs detailed impairment validation. 604 Note that detailed impairment estimation is not standardized. 606 4. Protocol Implications 608 The previous IA-RWA architectural alternatives and process flows make 609 differing demands on a GMPLS/PCE based control plane. In this section 610 we discuss the use of (a) an impairment information model, (b) PCE as 611 computational entity assuming the various process roles and 612 consequences for PCEP, (c)any needed extensions to signaling, and (d) 613 extensions to routing. The impacts to the control plane for IA-RWA 614 are summarized in Figure 3. 616 +-------------------+----+----+----------+--------+ 617 | IA-RWA Option |PCE |Sig |Info Model| Routing| 618 +-------------------+----+----+----------+--------+ 619 | Combined |Yes | No | Yes | Yes | 620 | IV & RWA | | | | | 621 +-------------------+----+----+----------+--------+- 622 | IV-Candidates |Yes | No | Yes | Yes | 623 | + RWA | | | | | 624 +-------------------+----+----+----------+--------+ 625 | Routing + |No | Yes| Yes | No | 626 |Distributed IV, RWA| | | | | 627 +-------------------+----+----+----------+--------+ 628 | Detailed IV |Yes | No | Yes | Yes | 629 +-------------------+----+----+----------+--------+ 630 Figure 3 IA-RWA architectural options and control plane impacts. 632 4.1. Information Model for Impairments 634 As previously discussed all IA-RWA scenarios to a greater or lesser 635 extent rely on a common impairment information model. A number of 636 ITU-T recommendations cover detailed as well as approximate 637 impairment characteristics of fibers and a variety of devices and 638 subsystems. A well integrated impairment model for optical network 639 elements is given in [G.680] and is used to form the basis for an 640 optical impairment model in a companion document [Imp-Info]. 642 It should be noted that the current version of [G.680] is limited to 643 the networks composed of a single WDM line system vendor combined 644 with OADMs and/or PXCs from potentially multiple other vendors, this 645 is known as situation 1 and is shown in Figure 1-1 of [G.680]. It is 646 planed in the future that [G.680] will include networks incorporating 647 line systems from multiple vendors as well as OADMs and/or PXCs from 648 potentially multiple other vendors, this is known as situation 2 and 649 is shown in Figure 1-2 of [G.680]. 651 The case of distributed impairment validation actually requires a bit 652 more than an impairment information model. In particular, it needs a 653 common impairment "computation" model. In the distributed IV case one 654 needs to standardize the accumulated impairment measures that will be 655 conveyed and updated at each node. Section 9 of [G.680] provides 656 guidance in this area with specific formulas given for OSNR, residual 657 dispersion, polarization mode dispersion/polarization dependent loss, 658 effects of channel uniformity, etc... However, specifics of what 659 intermediate results are kept and in what form would need to be 660 standardized. 662 4.1.1. Properties of an Impairment Information Model 664 In term of information model there are a set of property that needs 665 to be defined for each optical parameters that need to be in some way 666 considered within an impairment aware control plane. 668 The properties will help to determine how the control plane can deal 669 with it depending also on the above control plane architectural 670 options. In some case properties value will help to indentify the 671 level of approximation supported by the IV process. 673 o Time Dependency. This will identify how the impairment may vary 674 along the time. There could be cases where there's no time 675 dependency, while in other cases there is need of an impairment 676 re-evaluation after a certain time. In some cases a level of 677 approximation will consider an impairment that has time dependency 678 as constant. 680 o Wavelength Dependency. This property will identify if an 681 impairment value can be considered as constant over all the 682 wavelength spectrum of interest or if it has different values. 683 Also in this case a detailed impairment evaluation might lead to 684 consider the exact value while an approximation IV might take a 685 constant value for all wavelengths. 687 o Linearity. As impairments are representation of physical effects 688 there are some that have a linear behavior while other are non 689 linear. Linear impairments are in general easy to consider while a 690 non linear will require the knowledge of the full path to be 691 evaluated. An approximation level could only consider linear 692 effects or approximate non-linear impairments in linear ones. 694 o Multi-Channel. There are cases where an impairments take different 695 values depending on the aside wavelengths already in place. In 696 this case a dependency among different LSP is introduced. An 697 approximation level can neglect or not the effects on neighbor 698 LSPs. 700 o Value range. An impairment that has to be considered by a 701 computational element will needs a representation in bits. So 702 depending on the impairments different types can be considered 703 form integer to real numbers as well as a fixed set of values. 704 This information is important in term of protocol definition and 705 level of approximation introduced by the number representation. 707 4.2. Routing 709 Different approaches to path/wavelength impairment validation gives 710 rise to different demands placed on GMPLS routing protocols. In the 711 case where approximate impairment information is used to validate 712 paths GMPLS routing may be used to distribute the impairment 713 characteristics of the network elements and links based on the 714 impairment information model previously discussed. In the case of 715 distributed-IV no new demands would be placed on the routing 716 protocol. 718 4.3. Signaling 720 The largest impacts on signaling occur in the cases where distributed 721 impairment validation is performed. In this we need to accumulate 722 impairment information as previously discussed. In addition, since 723 the characteristics of the signal itself, such as modulation type, 724 can play a major role in the tolerance of impairments, this type of 725 information will need to be implicitly or explicitly signaled so that 726 an impairment validation decision can be made at the destination 727 node. 729 It remains for further study if it may be beneficial to include 730 additional information to a connection request such as desired egress 731 signal quality (defined in some appropriate sense) in non-distributed 732 IV scenarios. 734 4.4. PCE 736 In section 3.3. we gave a number of computation architectural 737 alternatives that could be used to meet the various requirements and 738 constraints of section 3.1. Here we look at how these alternatives 739 could be implemented via either a single PCE or a set of two or more 740 cooperating PCEs, and the impacts on the PCEP protocol. 742 4.4.1. Combined IV & RWA 744 In this situation, shown in Figure 1(a), a single PCE performs all 745 the computations needed for IA-RWA. 747 o TE Database Requirements 749 WSON Topology and switching capabilities, WSON WDM link wavelength 750 utilization, and WSON impairment information 752 o PCC to PCE Request Information 754 Signal characteristics/type, required quality, source node, 755 destination node 757 o PCE to PCC Reply Information 759 If the computations completed successfully then the PCE returns 760 the path and its assigned wavelength. If the computations could 761 not complete successfully it would be potentially useful to know 762 the reason why. At a very crude level we'd like to know if this 763 was due to lack of wavelength availability or impairment 764 considerations or a bit of both. The information to be conveyed is 765 for further study. 767 4.4.2. IV-Candidates + RWA 769 In this situation, shown in Figure 1(b), we have two separate 770 processes involved in the IA-RWA computation. This requires at least 771 two cooperating PCEs: one for the Candidates-IV process and another 772 for the RWA process. In addition, the overall process needs to be 773 coordinated. This could be done with yet another PCE or we can add 774 this functionality to one of previously defined PCEs. We choose this 775 later option and require the RWA PCE to also act as the overall 776 process coordinator. The roles, responsibilities and information 777 requirements for these two PCEs are given below. 779 RWA and Coordinator PCE (RWA-Coord-PCE): 781 Responsible for interacting with PCC and for utilizing Candidates-PCE 782 as needed during RWA computations. In particular it needs to know to 783 use the Candidates-PCE to obtain potential set of routes and 784 wavelengths. 786 o TE Database Requirements 788 WSON Topology and switching capabilities and WSON WDM link 789 wavelength utilization (no impairment information). 791 o PCC to RWA-PCE request: same as in the combined case. 793 o RWA-PCE to PCC reply: same as in the combined case. 795 o RWA-PCE to IV-Candidates-PCE request 797 The RWA-PCE asks for a set of at most K routes along with 798 acceptable wavelengths between nodes specified in the original PCC 799 request. 801 o IV-Candidates-PCE reply to RWA-PCE 803 The Candidates-PCE returns a set of at most K routes along with 804 acceptable wavelengths between nodes specified in the RWA-PCE 805 request. 807 IV-Candidates-PCE: 809 The IV-Candidates-PCE is responsible for impairment aware path 810 computation. It needs not take into account current link 811 wavelength utilization, but this is not prohibited. The 812 Candidates-PCE is only required to interact with the RWA-PCE as 813 indicated above and not the PCC. 815 o TE Database Requirements 817 WSON Topology and switching capabilities and WSON impairment 818 information (no information link wavelength utilization required). 820 In Figure 4 we show a sequence diagram for the interactions between 821 the PCC, RWA-PCE and IV-Candidates-PCE. 823 +---+ +-------------+ +-----------------+ 824 |PCC| |RWA-Coord-PCE| |IV-Candidates-PCE| 825 +-+-+ +------+------+ +---------+-------+ 826 ...___ (a) | | 827 | ````---...____ | | 828 | ```-->| | 829 | | | 830 | |--..___ (b) | 831 | | ```---...___ | 832 | | ```---->| 833 | | | 834 | | | 835 | | (c) ___...| 836 | | ___....---'''' | 837 | |<--'''' | 838 | | | 839 | | | 840 | (d) ___...| | 841 | ___....---''' | | 842 |<--''' | | 843 | | | 844 | | | 846 Figure 4 Sequence diagram for the interactions between PCC, RWA- 847 Coordinating-PCE and the IV-Candidates-PCE. 849 In step (a) the PCC requests a path meeting specified quality 850 constraints between two nodes (A and Z) for a given signal 851 represented either by a specific type or a general class with 852 associated parameters. In step (b) the RWA-Coordinating-PCE requests 853 up to K candidate paths between nodes A and Z and associated 854 acceptable wavelengths. In step (c) The IV-Candidates-PCE returns 855 this list to the RWA-Coordinating PCE which then uses this set of 856 paths and wavelengths as input (e.g. a constraint) to its RWA 857 computation. In step (d) the RWA-Coordinating-PCE returns the overall 858 IA-RWA computation results to the PCC. 860 4.4.3. Approximate IA-RWA + Separate Detailed IV 862 In Figure 2 we showed two cases where a separate detailed impairment 863 validation process could be utilized. We can place the detailed 864 validation process into a separate PCE. Assuming that a different PCE 865 assumes a coordinating role and interacts with the PCC we can keep 866 the interactions with this separate IV-Detailed-PCE very simple. 868 IV-Detailed-PCE: 870 o TE Database Requirements 872 The IV-Detailed-PCE will need optical impairment information, WSON 873 topology, and possibly WDM link wavelength usage information. This 874 document puts no restrictions on the type of information that may 875 be used in these computations. 877 o Coordinating-PCE to IV-Detailed-PCE request 879 The coordinating-PCE will furnish signal characteristics, quality 880 requirements, path and wavelength to the IV-Detailed-PCE. 882 o IV-Detailed-PCE to Coordinating-PCE reply 884 The reply is essential an yes/no decision as to whether the 885 requirements could actually be met. In the case where the 886 impairment validation fails it would be helpful to convey 887 information related to cause or quantify the failure, e.g., so a 888 judgment can be made whether to try a different signal or adjust 889 signal parameters. 891 In Figure 5 we show a sequence diagram for the interactions for the 892 process shown in Figure 2(b). This involves interactions between the 893 PCC, RWA-PCE (acting as coordinator), IV-Candidates-PCE and the IV- 894 Detailed-PCE. 896 In step (a) the PCC requests a path meeting specified quality 897 constraints between two nodes (A and Z) for a given signal 898 represented either by a specific type or a general class with 899 associated parameters. In step (b) the RWA-Coordinating-PCE requests 900 up to K candidate paths between nodes A and Z and associated 901 acceptable wavelengths. In step (c) The IV-Candidates-PCE returns 902 this list to the RWA-Coordinating PCE which then uses this set of 903 paths and wavelengths as input (e.g. a constraint) to its RWA 904 computation. In step (d) the RWA-Coordinating-PCE request a detailed 905 verification of the path and wavelength that it has computed. In step 906 (e) the IV-Detailed-PCE returns the results of the validation to the 907 RWA-Coordinating-PCE. Finally in step (f)IA-RWA-Coordinating PCE 908 returns the final results (either a path and wavelength or cause for 909 the failure to compute a path and wavelength) to the PCC. 911 +----------+ +--------------+ +------------+ 912 +---+ |RWA-Coord | |IV-Candidates | |IV-Detailed | 913 |PCC| | PCE | | PCE | | PCE | 914 +-+-+ +----+-----+ +------+-------+ +-----+------+ 915 |.._ (a) | | | 916 | ``--.__ | | | 917 | `-->| | | 918 | | (b) | | 919 | |--....____ | | 920 | | ````---.>| | 921 | | | | 922 | | (c) __..-| | 923 | | __..---'' | | 924 | |<--'' | | 925 | | | 926 | |...._____ (d) | 927 | | `````-----....._____ | 928 | | `````----->| 929 | | | 930 | | (e) _____.....+ 931 | | _____.....-----''''' | 932 | |<----''''' | 933 | (f) __.| | 934 | __.--'' | 935 |<-'' | 936 | | 937 Figure 5 Sequence diagram for the interactions between PCC, RWA- 938 Coordinating-PCE, IV-Candidates-PCE and IV-Detailed-PCE. 940 5. Security Considerations 942 This document discusses a number of control plane architectures that 943 incorporate knowledge of impairments in optical networks. If such 944 architecture is put into use within a network it will by its nature 945 contain details of the physical characteristics of an optical 946 network. Such information would need to be protected from intentional 947 or unintentional disclosure. 949 6. IANA Considerations 951 This draft does not currently require any consideration from IANA. 953 7. Acknowledgments 955 This document was prepared using 2-Word-v2.0.template.dot. 957 APPENDIX A: Overview of Optical Layer ITU-T Recommendations 959 For optical fiber, devices, subsystems and network elements the ITU-T 960 has a variety of recommendations that include definitions, 961 characterization parameters and test methods. In the following we 962 take a bottom up survey to emphasize the breadth and depth of the 963 existing recommendations. We focus on digital communications over 964 single mode optical fiber. 966 A.1. Fiber and Cables 968 Fibers and cables form a key component of what from the control plane 969 perspective could be termed an optical link. Due to the wide range of 970 uses of optical networks a fairly wide range of fiber types are used 971 in practice. The ITU-T has three main recommendations covering the 972 definition of attributes and test methods for single mode fiber: 974 o Definitions and test methods for linear, deterministic attributes 975 of single-mode fibre and cable [G.650.1] 977 o Definitions and test methods for statistical and non-linear 978 related attributes of single-mode fibre and cable [G.650.2] 980 o Test methods for installed single-mode fibre cable sections 981 [G.650.3] 983 General Definitions[G.650.1]: Mechanical Characteristics (numerous), 984 Mode field characteristics(mode field, mode field diameter, mode 985 field centre, mode field concentricity error, mode field non- 986 circularity), Glass geometry characteristics, Chromatic dispersion 987 definitions (chromatic dispersion, group delay, chromatic dispersion 988 coefficient, chromatic dispersion slope, zero-dispersion wavelength, 989 zero-dispersion slope), cut-off wavelength, attenuation. Definition 990 of equations and fitting coefficients for chromatic dispersion (Annex 991 A). [G.650.2] polarization mode dispersion (PMD) - phenomenon of PMD, 992 principal states of polarization (PSP), differential group delay 993 (DGD), PMD value, PMD coefficient, random mode coupling, negligible 994 mode coupling, mathematical definitions in terms of Stokes or Jones 995 vectors. Nonlinear attributes: Effective area, correction factor k, 996 non-linear coefficient (refractive index dependent on intensity), 997 Stimulated Billouin scattering. 999 Tests defined [G.650.1]: Mode field diameter, cladding diameter, core 1000 concentricity error, cut-off wavelength, attenuation, chromatic 1001 dispersion. [G.650.2]: test methods for polarization mode dispersion. 1002 [G.650.3] Test methods for characteristics of fibre cable sections 1003 following installation: attenuation, splice loss, splice location, 1004 fibre uniformity and length of cable sections (these are OTDR based), 1005 PMD, Chromatic dispersion. 1007 With these definitions a variety of single mode fiber types are 1008 defined as shown in the table below: 1010 ITU-T Standard | Common Name 1011 ------------------------------------------------------------ 1012 G.652 [G.652] | Standard SMF | 1013 G.653 [G.653] | Dispersion shifted SMF | 1014 G.654 [G.654] | Cut-off shifted SMF | 1015 G.655 [G.655] | Non-zero dispersion shifted SMF | 1016 G.656 [G.656] | Wideband non-zero dispersion shifted SMF | 1017 ------------------------------------------------------------ 1019 A.2. Devices 1021 A.2.1. Optical Amplifiers 1023 Optical amplifiers greatly extend the transmission distance of 1024 optical signals in both single channel and multi channel (WDM) 1025 subsystems. The ITU-T has the following recommendations: 1027 o Definition and test methods for the relevant generic parameters of 1028 optical amplifier devices and subsystems [G.661] 1030 o Generic characteristics of optical amplifier devices and 1031 subsystems [G.662] 1033 o Application related aspects of optical amplifier devices and 1034 subsystems [G.663] 1036 o Generic characteristics of Raman amplifiers and Raman amplified 1037 subsystems [G.665] 1039 Reference [G.661] starts with general classifications of optical 1040 amplifiers based on technology and usage, and include a near 1041 exhaustive list of over 60 definitions for optical amplifier device 1042 attributes and parameters. In references [G.662] and [G.665] we have 1043 characterization of specific devices, e.g., semiconductor optical 1044 amplifier, used in a particular setting, e.g., line amplifier. For 1045 example reference[G.662] gives the following minimum list of relevant 1046 parameters for the specification of an optical amplifier device used 1047 as line amplifier in a multichannel application: 1049 a) Channel allocation. 1051 b) Total input power range. 1053 c) Channel input power range. 1055 d) Channel output power range. 1057 e) Channel signal-spontaneous noise figure. 1059 f) Input reflectance. 1061 g) Output reflectance. 1063 h) Maximum reflectance tolerable at input. 1065 i) Maximum reflectance tolerable at output. 1067 j) Maximum total output power. 1069 k) Channel addition/removal (steady-state) gain response. 1071 l) Channel addition/removal (transient) gain response. 1073 m) Channel gain. 1075 n) Multichannel gain variation (inter-channel gain difference). 1077 o) Multichannel gain-change difference (inter-channel gain-change 1078 difference). 1080 p) Multichannel gain tilt (inter-channel gain-change ratio). 1082 q) Polarization Mode Dispersion (PMD). 1084 A.2.2. Dispersion Compensation 1086 In optical systems two forms of dispersion are commonly encountered 1087 [RFC4054] chromatic dispersion and polarization mode dispersion 1088 (PMD). There are a number of techniques and devices used for 1089 compensating for these effects. The following ITU-T recommendations 1090 characterize such devices: 1092 o Characteristics of PMD compensators and PMD compensating receivers 1093 [G.666] 1095 o Characteristics of Adaptive Chromatic Dispersion Compensators 1096 [G.667] 1098 The above furnish definitions as well as parameters and 1099 characteristics. For example in [G.667] adaptive chromatic dispersion 1100 compensators are classified as being receiver, transmitter or line 1101 based, while in [G.666] PMD compensators are only defined for line 1102 and receiver configurations. Parameters that are common to both PMD 1103 and chromatic dispersion compensators include: line fiber type, 1104 maximum and minimum input power, maximum and minimum bit rate, and 1105 modulation type. In addition there are a great many parameters that 1106 apply to each type of device and configuration. 1108 A.2.3. Optical Transmitters 1110 The definitions of the characteristics of optical transmitters can be 1111 found in references [G.957], [G.691], [G.692] and [G.959.1]. In 1112 addition references [G.957], [G.691], and [G.959.1] define specific 1113 parameter values or parameter ranges for these characteristics for 1114 interfaces for use in particular situations. 1116 We generally have the following types of parameters 1118 Wavelength related: Central frequency, Channel spacing, Central 1119 frequency deviation[G.692]. 1121 Spectral characteristics of the transmitter: Nominal source type 1122 (LED, MLM lasers, SLM lasers) [G.957], Maximum spectral width, Chirp 1123 parameter, Side mode suppression ratio, Maximum spectral power 1124 density [G.691]. 1126 Power related: Mean launched power, Extinction ration, Eye pattern 1127 mask [G.691], Maximum and minimum mean channel output power 1128 [G.959.1]. 1130 A.2.4. Optical Receivers 1132 References [G.959.1], [G.691], [G.692] and [G.957], define optical 1133 receiver characteristics and [G.959.1], [G.691] and [G.957]give 1134 specific values of these parameters for particular interface types 1135 and network contexts. 1137 The receiver parameters include: 1139 Receiver sensitivity: minimum value of average received power to 1140 achieve a 1x10-10 BER [G.957] or 1x10-12 BER [G.691]. See [G.957] and 1141 [G.691] for assumptions on signal condition. 1143 Receiver overload: Receiver overload is the maximum acceptable value 1144 of the received average power for a 1x10.10 BER [G.957] or a 1x10-12 1145 BER [G.691]. 1147 Receiver reflectance: "Reflections from the receiver back to the 1148 cable plant are specified by the maximum permissible reflectance of 1149 the receiver measured at reference point R." 1151 Optical path power penalty: "The receiver is required to tolerate an 1152 optical path penalty not exceeding X dB to account for total 1153 degradations due to reflections, intersymbol interference, mode 1154 partition noise, and laser chirp." 1156 When dealing with multi-channel systems or systems with optical 1157 amplifiers we may also need: 1159 Optical signal-to-noise ratio: "The minimum value of optical SNR 1160 required to obtain a 1x10-12 BER."[G.692] 1162 Receiver wavelength range: "The receiver wavelength range is defined 1163 as the acceptable range of wavelengths at point Rn. This range must 1164 be wide enough to cover the entire range of central frequencies over 1165 the OA passband." [G.692] 1167 Minimum equivalent sensitivity: "This is the minimum sensitivity that 1168 would be required of a receiver placed at MPI-RM in multichannel 1169 applications to achieve the specified maximum BER of the application 1170 code if all except one of the channels were to be removed (with an 1171 ideal loss-less filter) at point MPI-RM." [G.959.1] 1173 A.3. Components and Subsystems 1175 Reference [G.671] "Transmission characteristics of optical components 1176 and subsystems" covers the following components: 1178 o optical add drop multiplexer (OADM) subsystem; 1180 o asymmetric branching component; 1182 o optical attenuator; 1184 o optical branching component (wavelength non-selective); 1186 o optical connector; 1188 o dynamic channel equalizer (DCE); 1189 o optical filter; 1191 o optical isolator; 1193 o passive dispersion compensator; 1195 o optical splice; 1197 o optical switch; 1199 o optical termination; 1201 o tuneable filter; 1203 o optical wavelength multiplexer (MUX)/demultiplexer (DMUX); 1205 - coarse WDM device; 1207 - dense WDM device; 1209 - wide WDM device. 1211 Reference [G.671] then specifies applicable parameters for these 1212 components. For example an OADM subsystem will have parameters such 1213 as: insertion loss (input to output, input to drop, add to output), 1214 number of add, drop and through channels, polarization dependent 1215 loss, adjacent channel isolation, allowable input power, polarization 1216 mode dispersion, etc... 1218 A.4. Network Elements 1220 The previously cited ITU-T recommendations provide a plethora of 1221 definitions and characterizations of optical fiber, devices, 1222 components and subsystems. Reference [G.Sup39] "Optical system design 1223 and engineering considerations" provides useful guidance on the use 1224 of such parameters. 1226 In many situations the previous models while good don't encompass the 1227 higher level network structures that one typically deals with in the 1228 control plane, i.e, "links" and "nodes". In addition such models 1229 include the full range of network applications from planning, 1230 installation, and possibly day to day network operations, while with 1231 the control plane we are generally concerned with a subset of the 1232 later. In particular for many control plane applications we are 1233 interested in formulating the total degradation to an optical signal 1234 as it travels through multiple optical subsystems, devices and fiber 1235 segments. 1237 In reference [G.680] "Physical transfer functions of optical networks 1238 elements", a degradation function is currently defined for the 1239 following optical network elements: (a) DWDM Line segment, (b) 1240 Optical Add/Drop Multiplexers (OADM), and (c) Photonic cross-connect 1241 (PXC). The scope of [G.680] is currently for optical networks 1242 consisting of one vendors DWDM line systems along with another 1243 vendors OADMs or PXCs. 1245 The DWDM line system of [G.680] consists of the optical fiber, line 1246 amplifiers and any embedded dispersion compensators. Similarly the 1247 OADM/PXC network element may consist of the basic OADM component and 1248 optionally included optical amplifiers. The parameters for these 1249 optical network elements (ONE) are given under the following 1250 circumstances: 1252 o General ONE without optical amplifiers 1254 o General ONE with optical amplifiers 1256 o OADM without optical amplifiers 1258 o OADM with optical amplifiers 1260 o Reconfigurable OADM (ROADM) without optical amplifiers 1262 o ROADM with optical amplifiers 1264 o PXC without optical amplifiers 1266 o PXC with optical amplifiers 1268 8. References 1270 8.1. Normative References 1272 [G.650.1] ITU-T Recommendation G.650.1, Definitions and test methods 1273 for linear, deterministic attributes of single-mode fibre 1274 and cable, June 2004. 1276 [650.2] ITU-T Recommendation G.650.2, Definitions and test methods 1277 for statistical and non-linear related attributes of 1278 single-mode fibre and cable, July 2007. 1280 [650.3] ITU-T Recommendation G.650.3 1282 [G.652] ITU-T Recommendation G.652, Characteristics of a single-mode 1283 optical fibre and cable, June 2005. 1285 [G.653] ITU-T Recommendation G.653, Characteristics of a dispersion- 1286 shifted single-mode optical fibre and cable, December 2006. 1288 [G.654] ITU-T Recommendation G.654, Characteristics of a cut-off 1289 shifted single-mode optical fibre and cable, December 2006. 1291 [G.655] ITU-T Recommendation G.655, Characteristics of a non-zero 1292 dispersion-shifted single-mode optical fibre and cable, 1293 March 2006. 1295 [G.656] ITU-T Recommendation G.656, Characteristics of a fibre and 1296 cable with non-zero dispersion for wideband optical 1297 transport, December 2006. 1299 [G.661] ITU-T Recommendation G.661, Definition and test methods for 1300 the relevant generic parameters of optical amplifier 1301 devices and subsystems, March 2006. 1303 [G.662] ITU-T Recommendation G.662, Generic characteristics of 1304 optical amplifier devices and subsystems, July 2005. 1306 [G.671] ITU-T Recommendation G.671, Transmission characteristics of 1307 optical components and subsystems, January 2005. 1309 [G.680] ITU-T Recommendation G.680, Physical transfer functions of 1310 optical network elements, July 2007. 1312 [G.691] ITU-T Recommendation G.691, Optical interfaces for 1313 multichannel systems with optical amplifiers, November 1314 1998. 1316 [G.692] ITU-T Recommendation G.692, Optical interfaces for single 1317 channel STM-64 and other SDH systems with optical 1318 amplifiers, March 2006. 1320 [G.872] ITU-T Recommendation G.872, Architecture of optical 1321 transport networks, November 2001. 1323 [G.957] ITU-T Recommendation G.957, Optical interfaces for 1324 equipments and systems relating to the synchronous digital 1325 hierarchy, March 2006. 1327 [G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network 1328 Physical Layer Interfaces, March 2006. 1330 [G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM 1331 applications: DWDM frequency grid, June 2002. 1333 [G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM 1334 applications: CWDM wavelength grid, December 2003. 1336 [G.698.1] ITU-T Recommendation G.698.1, Multichannel DWDM 1337 applications with Single-Channel optical interface, 1338 December 2006. 1340 [G.698.2] ITU-T Recommendation G.698.2, Amplified multichannel DWDM 1341 applications with Single-Channel optical interface, July 1342 2007. 1344 [G.Sup39] ITU-T Series G Supplement 39, Optical system design and 1345 engineering considerations, February 2006. 1347 [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label 1348 Switching (GMPLS) Architecture", RFC 3945, October 2004. 1350 [RFC4054] Strand, J., Ed., and A. Chiu, Ed., "Impairments and Other 1351 Constraints on Optical Layer Routing", RFC 4054, May 2005. 1353 [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation 1354 Element (PCE)-Based Architecture", RFC 4655, August 2006. 1356 [WSON-Frame] G. Bernstein, Y. Lee, W. Imajuku, "Framework for GMPLS 1357 and PCE Control of Wavelength Switched Optical Networks", 1358 work in progress: draft-ietf-ccamp-wavelength-switched- 1359 framework-01.txt, November 2008. 1361 8.2. Informative References 1363 [Imp-Info] G. Bernstein, Y. Lee, D. Li, "A Framework for the Control 1364 and Measurement of Wavelength Switched Optical Networks 1365 (WSON) with Impairments", work in progress: draft- 1366 bernstein-wson-impairment-info-01.txt, March 2009. 1368 [Martinelli] G. Martinelli (ed.) and A. Zanardi (ed.), "GMPLS 1369 Signaling Extensions for Optical Impairment Aware Lightpath 1370 Setup", Work in Progress: draft-martinelli-ccamp-optical- 1371 imp-signaling-01.txt, February 2008. 1373 Author's Addresses 1375 Greg M. Bernstein (ed.) 1376 Grotto Networking 1377 Fremont California, USA 1379 Phone: (510) 573-2237 1380 Email: gregb@grotto-networking.com 1382 Young Lee (ed.) 1383 Huawei Technologies 1384 1700 Alma Drive, Suite 100 1385 Plano, TX 75075 1386 USA 1388 Phone: (972) 509-5599 (x2240) 1389 Email: ylee@huawei.com 1391 Dan Li 1392 Huawei Technologies Co., Ltd. 1393 F3-5-B R&D Center, Huawei Base, 1394 Bantian, Longgang District 1395 Shenzhen 518129 P.R.China 1397 Phone: +86-755-28973237 1398 Email: danli@huawei.com 1399 Giovanni Martinelli 1400 Cisco 1401 Via Philips 12 1402 20052 Monza, Italy 1404 Phone: +39 039 2092044 1405 Email: giomarti@cisco.com 1407 Contributor's Addresses 1409 Ming Chen 1410 Huawei Technologies Co., Ltd. 1411 F3-5-B R&D Center, Huawei Base, 1412 Bantian, Longgang District 1413 Shenzhen 518129 P.R.China 1415 Phone: +86-755-28973237 1416 Email: mchen@huawei.com 1418 Rebecca Han 1419 Huawei Technologies Co., Ltd. 1420 F3-5-B R&D Center, Huawei Base, 1421 Bantian, Longgang District 1422 Shenzhen 518129 P.R.China 1424 Phone: +86-755-28973237 1425 Email: hanjianrui@huawei.com 1427 Gabriele Galimberti 1428 Cisco 1429 Via Philips 12, 1430 20052 Monza, Italy 1432 Phone: +39 039 2091462 1433 Email: ggalimbe@cisco.com 1435 Alberto Tanzi 1436 Cisco 1437 Via Philips 12, 1438 20052 Monza, Italy 1440 Phone: +39 039 2091469 1441 Email: altanzi@cisco.com 1443 Intellectual Property Statement 1445 The IETF Trust takes no position regarding the validity or scope of 1446 any Intellectual Property Rights or other rights that might be 1447 claimed to pertain to the implementation or use of the technology 1448 described in any IETF Document or the extent to which any license 1449 under such rights might or might not be available; nor does it 1450 represent that it has made any independent effort to identify any 1451 such rights. 1453 Copies of Intellectual Property disclosures made to the IETF 1454 Secretariat and any assurances of licenses to be made available, or 1455 the result of an attempt made to obtain a general license or 1456 permission for the use of such proprietary rights by implementers or 1457 users of this specification can be obtained from the IETF on-line IPR 1458 repository at http://www.ietf.org/ipr 1460 The IETF invites any interested party to bring to its attention any 1461 copyrights, patents or patent applications, or other proprietary 1462 rights that may cover technology that may be required to implement 1463 any standard or specification contained in an IETF Document. Please 1464 address the information to the IETF at ietf-ipr@ietf.org. 1466 Disclaimer of Validity 1468 All IETF Documents and the information contained therein are provided 1469 on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE 1470 REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE 1471 IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL 1472 WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY 1473 WARRANTY THAT THE USE OF THE INFORMATION THEREIN WILL NOT INFRINGE 1474 ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS 1475 FOR A PARTICULAR PURPOSE. 1477 Acknowledgment 1479 We thank Chen Ming of DICONNET Project who provided valuable 1480 information relevant to this document. 1482 We'd also like to thank Deborah Brungard for editorial and technical 1483 assistance.