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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group Y. Lee (ed.) 2 Internet Draft Huawei 3 Intended status: Informational G. Bernstein (ed.) 4 Expires: August 2009 Grotto Networking 5 Wataru Imajuku 6 NTT 8 February 9, 2009 10 Framework for GMPLS and PCE Control of Wavelength Switched Optical 11 Networks (WSON) 12 draft-ietf-ccamp-rwa-wson-framework-01.txt 14 Status of this Memo 16 This Internet-Draft is submitted to IETF in full conformance with the 17 provisions of BCP 78 and BCP 79. 19 Internet-Drafts are working documents of the Internet Engineering 20 Task Force (IETF), its areas, and its working groups. Note that 21 other groups may also distribute working documents as Internet- 22 Drafts. 24 Internet-Drafts are draft documents valid for a maximum of six months 25 and may be updated, replaced, or obsoleted by other documents at any 26 time. It is inappropriate to use Internet-Drafts as reference 27 material or to cite them other than as "work in progress." 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html 35 This Internet-Draft will expire on August 9, 2009. 37 Copyright Notice 39 Copyright (c) 2009 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. 49 Abstract 51 This memo provides a framework for applying Generalized Multi- 52 Protocol Label Switching (GMPLS) and the Path Computation Element 53 (PCE) architecture to the control of wavelength switched optical 54 networks (WSON). In particular we provide control plane models for 55 key wavelength switched optical network subsystems and processes. The 56 subsystems include wavelength division multiplexed links, tunable 57 laser transmitters, reconfigurable optical add/drop multiplexers 58 (ROADM) and wavelength converters. 60 Lightpath provisioning, in general, requires the routing and 61 wavelength assignment (RWA) process. This process is reviewed and the 62 information requirements, both static and dynamic for this process 63 are presented, along with alternative implementation scenarios that 64 could be realized via GMPLS/PCE and/or extended GMPLS/PCE protocols. 65 This memo does NOT address optical impairments in any depth and 66 focuses on topological elements and path selection constraints that 67 are common across different WSON environments. It is expected that a 68 variety of different techniques will be applied to optical 69 impairments depending on the type of WSON, such as access, metro or 70 long haul. 72 Table of Contents 74 1. Introduction...................................................4 75 1.1. Revision History..........................................5 76 1.1.1. Changes from 00......................................5 77 2. Terminology....................................................5 78 3. Wavelength Switched Optical Networks...........................5 79 3.1. WDM and CWDM Links........................................6 80 3.2. Optical Transmitters......................................8 81 3.2.1. Lasers...............................................8 82 3.2.2. Spectral Characteristics & Modulation Type...........9 83 3.2.3. Signal Rates and Error Correction...................10 84 3.3. ROADMs, OXCs, Splitters, Combiners and FOADMs............10 85 3.3.1. Reconfigurable Add/Drop Multiplexers and OXCs.......10 86 3.3.2. Splitters...........................................12 87 3.3.3. Combiners...........................................13 88 3.3.4. Fixed Optical Add/Drop Multiplexers.................13 89 3.4. Wavelength Converters....................................14 90 3.4.1. Wavelength Converter Pool Modeling..................16 91 4. Routing and Wavelength Assignment and the Control Plane.......19 92 4.1. Architectural Approaches to RWA..........................20 93 4.1.1. Combined RWA (R&WA).................................21 94 4.1.2. Separated R and WA (R+WA)...........................21 95 4.1.3. Routing and Distributed WA (R+DWA)..................22 96 4.2. Conveying information needed by RWA......................22 97 4.3. Lightpath Temporal Characteristics.......................23 98 5. Modeling Examples and Control Plane Use Cases.................24 99 5.1. Network Modeling for GMPLS/PCE Control...................24 100 5.1.1. Describing the WSON nodes...........................25 101 5.1.2. Describing the links................................27 102 5.2. RWA Path Computation and Establishment...................28 103 5.3. Resource Optimization....................................29 104 5.4. Support for Rerouting....................................30 105 6. GMPLS & PCE Implications......................................30 106 6.1. Implications for GMPLS signaling.........................30 107 6.1.1. Identifying Wavelengths and Signals.................31 108 6.1.2. Combined RWA/Separate Routing WA support............31 109 6.1.3. Distributed Wavelength Assignment: Unidirectional, No 110 Converters.................................................31 111 6.1.4. Distributed Wavelength Assignment: Unidirectional, 112 Limited Converters.........................................32 113 6.1.5. Distributed Wavelength Assignment: Bidirectional, No 114 Converters.................................................33 115 6.2. Implications for GMPLS Routing...........................33 116 6.2.1. Need for Wavelength-Specific Maximum Bandwidth 117 Information................................................34 118 6.2.2. Need for Wavelength-Specific Availability Information34 119 6.2.3. Relationship to Link Bundling and Layering..........35 120 6.2.4. WSON Routing Information Summary....................35 121 6.3. Optical Path Computation and Implications for PCE........36 122 6.3.1. Lightpath Constraints and Characteristics...........36 123 6.3.2. Computation Architecture Implications...............37 124 6.3.3. Discovery of RWA Capable PCEs.......................37 125 6.4. Scaling Implications.....................................38 126 6.4.1. Routing.............................................38 127 6.4.2. Signaling...........................................38 128 6.4.3. Path computation....................................38 129 6.5. Summary of Impacts by RWA Architecture...................39 130 7. Security Considerations.......................................40 131 8. IANA Considerations...........................................40 132 9. Acknowledgments...............................................40 133 10. References...................................................41 134 10.1. Normative References....................................41 135 10.2. Informative References..................................42 136 11. Contributors.................................................45 137 Author's Addresses...............................................45 138 Intellectual Property Statement..................................46 139 Disclaimer of Validity...........................................46 141 1. Introduction 143 From its beginning Generalized Multi-Protocol Label Switching (GMPLS) 144 was intended to control wavelength switched optical networks (WSON) 145 with the GMPLS architecture document [RFC3945] explicitly mentioning 146 both wavelength and waveband switching and equating wavelengths 147 (lambdas) with GMPLS labels. In addition a discussion of optical 148 impairments and other constraints on optical routing can be found in 149 [RFC4054]. However, optical technologies have advanced in ways that 150 make them significantly different from other circuit switched 151 technologies such as Time Division Multiplexing (TDM). Service 152 providers have already deployed many of these new optical 153 technologies such as ROADMs and tunable lasers and desire the same 154 automation and restoration capabilities that GMPLS has provided to 155 TDM and packet switched networks. Another important application of an 156 automated control plane such as GMPLS is the possibility to improve, 157 via recovery schemes, the availability of the network. One of the 158 key points of GMPLS based recovery schemes is the capability to 159 survive multiple failures while legacy protection mechanism such as 160 1+1 path protection can survive from a single failure. Moreover this 161 improved availability can be obtained using less network resources. 163 This document will focus on the unique properties of links, switches 164 and path selection constraints that occur in WSONs. Different WSONs 165 such as access, metro and long haul may apply different techniques 166 for dealing with optical impairments hence this document will NOT 167 address optical impairments in any depth, but instead focus on 168 properties that are common across a variety of WSONs. 170 This memo provides a framework for applying GMPLS and the Path 171 Computation Element (PCE) architecture to the control of WSONs. In 172 particular we provide control plane models for key wavelength 173 switched optical network subsystems and processes. The subsystems 174 include wavelength division multiplexed links, tunable laser 175 transmitters, reconfigurable optical add/drop multiplexers (ROADM) 176 and wavelength converters. 178 Lightpath provisioning, in general, requires the routing and 179 wavelength assignment (RWA) process. This process is reviewed and the 180 information requirements, both static and dynamic for this process 181 are presented, along with alternative implementation architectures 182 that could be realized via various combinations of extended GMPLS and 183 PCE protocols. 185 1.1. Revision History 187 1.1.1. Changes from 00 189 o Added new first level section on modeling examples and control 190 plane use cases. 192 o Added new third level section on wavelength converter pool 193 modeling 195 o Editorial clean up of English and updated references. 197 2. Terminology 199 CWDM: Coarse Wavelength Division Multiplexing. 201 DWDM: Dense Wavelength Division Multiplexing. 203 FOADM: Fixed Optical Add/Drop Multiplexer. 205 OXC: Optical cross connect. A symmetric optical switching element in 206 which a signal on any ingress port can reach any egress port. 208 ROADM: Reconfigurable Optical Add/Drop Multiplexer. An asymmetric 209 wavelength selective switching element featuring ingress and egress 210 line side ports as well as add/drop side ports. 212 RWA: Routing and Wavelength Assignment. 214 Wavelength Conversion/Converters: The process of converting an 215 information bearing optical signal centered at a given wavelength to 216 one with "equivalent" content centered at a different wavelength. 217 Wavelength conversion can be implemented via an optical-electronic- 218 optical (OEO) process or via a strictly optical process. 220 WDM: Wavelength Division Multiplexing. 222 Wavelength Switched Optical Networks (WSON): WDM based optical 223 networks in which switching is performed selectively based on the 224 center wavelength of an optical signal. 226 3. Wavelength Switched Optical Networks 228 WSONs come in a variety of shapes and sizes from continent spanning 229 long haul networks, to metropolitan networks, to residential access 230 networks. In all these cases we are concerned with those properties 231 that constrain the choice of wavelengths that can be used, i.e., 232 restrict the wavelength label set, impact the path selection process, 233 and limit the topological connectivity. In the following we examine 234 and model some major subsystems of a WSON with an emphasis on those 235 aspects that are of relevance to the control plane. In particular we 236 look at WDM links, Optical Transmitters, ROADMs, and Wavelength 237 Converters. 239 3.1. WDM and CWDM Links 241 WDM and CWDM links run over optical fibers, and optical fibers come 242 in a wide range of types that tend to be optimized for various 243 applications from access networks, metro, long haul, and submarine 244 links to name a few. ITU-T and IEC standards exist for various types 245 of fibers. For the purposes here we are concerned only with single 246 mode fibers (SMF). The following SMF fiber types are typically 247 encountered in optical networks: 249 ITU-T Standard | Common Name 250 ------------------------------------------------------------ 251 G.652 [G.652] | Standard SMF | 252 G.653 [G.653] | Dispersion shifted SMF | 253 G.654 [G.654] | Cut-off shifted SMF | 254 G.655 [G.655] | Non-zero dispersion shifted SMF | 255 G.656 [G.656] | Wideband non-zero dispersion shifted SMF | 256 ------------------------------------------------------------ 257 These fiber types are differentiated by their optical impairment 258 characteristics such as attenuation, chromatic dispersion, 259 polarization mode dispersion, four wave mixing, etc. Since these 260 effects can be dependent upon wavelength, channel spacing and input 261 power level, the net effect for our modeling purposes here is to 262 restrict the range of wavelengths that can be used. 264 Typically WDM links operate in one or more of the approximately 265 defined optical bands [G.Sup39]: 267 Band Range (nm) Common Name Raw Bandwidth (THz) 268 O-band 1260-1360 Original 17.5 269 E-band 1360-1460 Extended 15.1 270 S-band 1460-1530 Short 9.4 271 C-band 1530-1565 Conventional 4.4 272 L-band 1565-1625 Long 7.1 273 U-band 1625-1675 Ultra-long 5.5 275 Not all of a band may be usable, for example in many fibers that 276 support E-band there is significant attenuation due to a water 277 absorption peak at 1383nm. Hence we can have a discontinuous 278 acceptable wavelength range for a particular link. Also some systems 279 will utilize more than one band. This is particularly true for coarse 280 WDM (CWDM) systems. 282 [Editor's note: the previous text is primarily tutorial in nature and 283 maybe deleted or moved to an appendix in a future draft] 285 Current technology breaks up the bandwidth capacity of fibers into 286 distinct channels based on either wavelength or frequency. There are 287 two standards covering wavelengths and channel spacing. ITU-T 288 recommendation [G.694.1] describes a DWDM grid defined in terms of 289 frequency grids of 12.5GHz, 25GHz, 50GHz, 100GHz, and other multiples 290 of 100GHz around a 193.1THz center frequency. At the narrowest 291 channel spacing this provides less than 4800 channels across the O 292 through U bands. ITU-T recommendation [G.694.2] describes a CWDM grid 293 defined in terms of wavelength increments of 20nm running from 1271nm 294 to 1611nm for 18 or so channels. The number of channels is 295 significantly smaller than the 32 bit GMPLS label space allocated to 296 lambda switching. A label representation for these ITU-T grids is 297 given in [Otani] and allows a common vocabulary to be used in 298 signaling lightpaths. Further, these ITU-T grid based labels can and 299 also be used to describe WDM links, ROADM ports, and wavelength 300 converters for the purposes path selection. 302 With a tremendous existing base of fiber many WDM links are designed 303 to take advantage of particular fiber characteristics or to try to 304 avoid undesirable properties. For example dispersion shifted SMF 305 [G.653] was originally designed for good long distance performance in 306 single channel systems, however putting WDM over this type of fiber 307 requires much system engineering and a fairly limited range of 308 wavelengths. Hence for our basic, impairment unaware, modeling of a 309 WDM link we will need the following information: 311 o Wavelength range(s): Given a mapping between labels and the ITU-T 312 grids each range could be expressed in terms of a doublet 313 (lambda1, lambda2) or (freq1, freq1) where the lambdas or 314 frequencies can be represented by 32 bit integers. 316 o Channel spacing: currently there are about five channel spacings 317 used in DWDM systems 12.5GHz to 200GHz and one defined CWDM 318 spacing. 320 For a particular link this information is relatively static, i.e., 321 changes to these properties generally require hardware upgrades. Such 322 information could be used locally during wavelength assignment via 323 signaling, similar to label restrictions in MPLS or used by a PCE in 324 solving the combined routing and wavelength assignment problem. 326 3.2. Optical Transmitters 328 3.2.1. Lasers 330 WDM optical systems make use of laser transmitters utilizing 331 different wavelengths (frequencies). Some laser transmitters were and 332 are manufactured for a specific wavelength of operation, that is, the 333 manufactured frequency cannot be changed. First introduced to reduce 334 inventory costs, tunable optical laser transmitters are becoming 335 widely deployed in some systems [Coldren04], [Buus06]. This allows 336 flexibility in the wavelength used for optical transmission and aids 337 in the control of path selection. 339 Fundamental modeling parameters from the control plane perspective 340 optical transmitters are: 342 o Tunable: Is this transmitter tunable or fixed. 344 o Tuning range: This is the frequency or wavelength range over which 345 the laser can be tuned. With the fixed mapping of labels to 346 lambdas of [Otani] this can be expressed as a doublet (lambda1, 347 lambda2) or (freq1, freq2) where lambda1 and lambda2 or freq1 and 348 freq2 are the labels representing the lower and upper bounds in 349 wavelength or frequency. 351 o Tuning time: Tuning times highly depend on the technology used. 352 Thermal drift based tuning may take seconds to stabilize, whilst 353 electronic tuning might provide sub-ms tuning times. Depending on 354 the application this might be critical. For example, thermal drift 355 might not be applicable for fast protection applications. 357 o Spectral Characteristics and stability: The spectral shape of the 358 laser's emissions and its frequency stability put limits on 359 various properties of the overall WDM system. One relatively easy 360 to characterize constraint is the finest channel spacing on which 361 the transmitter can be used. 363 Note that ITU-T recommendations specify many other aspects of a 364 laser's such as spectral characteristics and stability. Many of these 365 parameters are used in the design of WDM subsystems consisting of 366 transmitters, WDM links and receivers however they do not furnish 367 additional information that will influence label switched path (LSP) 368 provisioning in a properly designed system. 370 Also note that lasers transmitters as a component can degrade and 371 fail over time. This presents the possibility of the failure of a LSP 372 (lightpath) without either a node or link failure. Hence, additional 373 mechanisms may be necessary to detect and differentiate this failure 374 from the others, e.g., one doesn't not want to initiate mesh 375 restoration if the source transmitter has failed, since the laser 376 transmitter will still be failed on the alternate optical path. 378 3.2.2. Spectral Characteristics & Modulation Type 380 Contrary to some marketing claims optical systems are not truly 381 "transparent" to the content of the signals that they carry. Each 382 lightpath will have spectral characteristics based on its content, 383 and the spacing of wavelengths in a WDM link will ultimately put 384 constraints on that spectrum. 386 For analog signals such as used in closed access television (CATV) or 387 "radio over fiber" links spectral characteristics are given in terms 388 of various bandwidth measures. However digital signals consist of our 389 main focus here and in the ITU-T G series optical specifications. In 390 this case the spectral characteristics can be more accurately 391 inferred from the modulation format and the bit rate. 393 Although Non-Return to Zero (NRZ) is currently the dominant form of 394 optical modulation, new modulation formats are being researched 395 [Winzer06] and deployed. With a choice in modulation formats we no 396 longer have a one to one relationship between digital bandwidth in 397 bytes or bits per second and the amount of optical spectrum (optical 398 bandwidth) consumed. To simplify the specification of optical signals 399 the ITU-T, in recommendation G.959.1, combined a rate bound and 400 modulation format designator [G.959.1]. For example, two of the 401 signal classes defined in [G.959.1] are: 403 Optical tributary signal class NRZ 1.25G: 405 "Applies to continuous digital signals with non-return to zero line 406 coding, from nominally 622 Mbit/s to nominally 1.25 Gbit/s. Optical 407 tributary signal class NRZ 1.25G includes a signal with STM-4 bit 408 rate according to ITU-T Rec. G.707/Y.1322." Note that Gigabit 409 Ethernet falls into this signaling class as well. 411 Optical tributary signal class RZ 40G: 413 "Applies to continuous digital signals with return to zero line 414 coding, from nominally 9.9 Gbit/s to nominally 43.02 Gbit/s. 415 Optical tributary signal class RZ 40G includes a signal with STM- 416 256 bit rate according to ITU-T Rec. G.707/Y.1322 and OTU3 bit rate 417 according to ITU-T Rec. G.709/Y.1331." 419 From a modeling perspective we have: 421 o Analog signals: bandwidth parameters, e.g., 3dB parameters and 422 similar. 424 o Digital signals: there are predefined modulation bit rate classes 425 that we can encode. 427 This information can be important in constraining route selection, 428 for example some signals may not be compatible with some links or 429 wavelength converters. In addition it lets the endpoints understand 430 if it can process the signal. 432 3.2.3. Signal Rates and Error Correction 434 Although, the spectral characteristics of a signal determine its 435 basic compatibility with a WDM system, more information is generally 436 needed for various processing activities such as regeneration and 437 reception. Many digital signals such as Ethernet, G.709, and SDH have 438 well defined encoding which includes forward error correction (FEC). 439 However many subsystem vendors offer additional FEC options for a 440 given signal type. The use of different FECs can lead to different 441 overall signal rates. If the FEC and rate used is not compatible 442 between the sender and receiver the signal can not be correctly 443 processed. Note that the rates of "standard" signals may be extended 444 to accommodate different payloads. For example there are 445 transmitters capable of directly mapping 10GE LAN-PHY traffic into 446 G.709 ODU2 frame with slightly higher clock rate [G.Sup43]. 448 3.3. ROADMs, OXCs, Splitters, Combiners and FOADMs 450 Definitions of various optical devices and their parameters can be 451 found in [G.671], we only look at a subset of these and their non- 452 impairment related properties. 454 3.3.1. Reconfigurable Add/Drop Multiplexers and OXCs 456 Reconfigurable add/drop optical multiplexers (ROADM) have matured and 457 are available in different forms and technologies [Basch06]. This is 458 a key technology that allows wavelength based optical switching. A 459 classic degree-2 ROADM is shown in Figure 1. 461 Line side ingress +---------------------+ Line side egress 462 --->| |---> 463 | | 464 | ROADM | 465 | | 466 | | 467 +---------------------+ 468 | | | | o o o o 469 | | | | | | | | 470 O O O O | | | | 471 Tributary Side: Drop (egress) Add (ingress) 473 Figure 1 Degree-2 ROADM 475 The key feature across all ROADM types is their highly asymmetric 476 switching capability. In the ROADM of Figure 1, the "add" ingress 477 ports can only egress on the line side egress port and not on any of 478 the "drop" egress ports. The degree of a ROADM or switch is given by 479 the number of line side ports (ingress and egress) and does not 480 include the number of "add" or "drop" ports. Sometimes the "add" 481 "drop" ports are also called tributary ports. As the degree of the 482 ROADM increases beyond two it can have properties of both a switch 483 (OXC) and a multiplexer and hence we must know the switched 484 connectivity offered by such a network element to effectively utilize 485 it. A straight forward way to do this is via a "switched 486 connectivity" matrix A where Amn = 0 or 1, depending upon whether a 487 wavelength on ingress port m can be connected to egress port n 488 [Imajuku]. For the ROADM of Figure 1 the switched connectivity matrix 489 can be expressed as 491 Ingress Egress Port 492 Port #1 #2 #3 #4 #5 493 -------------- 494 #1: 1 1 1 1 1 495 #2 1 0 0 0 0 496 A = #3 1 0 0 0 0 497 #4 1 0 0 0 0 498 #5 1 0 0 0 0 500 Where ingress ports 2-5 are add ports, egress ports 2-5 are drop 501 ports and ingress port #1 and egress port #1 are the line side (WDM) 502 ports. 504 For ROADMs this matrix will be very sparse, and for OXCs the 505 complement of the matrix will be very sparse, compact encodings and 506 usage including high degree ROADMs/OXCs are given in [WSON-Encode]. 508 Additional constraints may also apply to the various ports in a 509 ROADM/OXC. In the literature of optical switches and ROADMs the 510 following restrictions/terms are used: 512 Colored port: An ingress or more typically an egress (drop) port 513 restricted to a single channel of fixed wavelength. 515 Colorless port: An ingress or more typically an egress (drop) port 516 restricted to a single channel of arbitrary wavelength. 518 In general a port on a ROADM could have any of the following 519 wavelength restrictions: 521 o Multiple wavelengths, full range port 523 o Single wavelength, full range port 525 o Single wavelength, fixed lambda port 527 o Multiple wavelengths, reduced range port (for example wave band 528 switching) 530 To model these restrictions we need two pieces of information for 531 each port: (a) number of wavelengths, (b) wavelength range and 532 spacing. Note that this information is relatively static. More 533 complicated wavelength constraints are modeled in [WSON-Info]. 535 3.3.2. Splitters 537 An optical splitter consists of a single ingress port and two or more 538 egress ports. The ingress optical signaled is essentially copied 539 (with loss) to all egress ports. 541 Using the modeling notions of section 3.3.1. the ingress and egress 542 ports of a splitter would have the same wavelength restrictions. In 543 addition we can describe a splitter by a connectivity matrix Amn as 544 follows: 546 Ingress Egress Port 547 Port #1 #2 #3 ... #N 548 ----------------- 549 A = #1 1 1 1 ... 1 551 The difference from a simple ROADM is that this is not a switched 552 connectivity matrix but the fixed connectivity matrix of the device. 554 3.3.3. Combiners 556 A optical combiner is somewhat the dual of a splitter in that it has 557 a single multi-wavelength egress port and multiple ingress ports. 558 The contents of all the ingress ports are copied and combined to the 559 single egress port. The various ports may have different wavelength 560 restrictions. It is generally the responsibility of those using the 561 combiner to assure that wavelength collision does not occur on the 562 egress port. The fixed connectivity matrix Amn for a combiner would 563 look like: 565 Ingress Egress Port 566 Port #1 567 --- 568 #1: 1 569 #2 1 570 A = #3 1 571 ... 1 572 #N 1 574 3.3.4. Fixed Optical Add/Drop Multiplexers 576 A fixed optical add/drop multiplexer can alter the course of an 577 ingress wavelength in a preset way. In particular a particular 578 wavelength (or waveband) from a line side ingress port would be 579 dropped to a particular "tributary" egress port. Depending on the 580 device's fixed configuration that same wavelength may or may not be 581 "continued" to the line side egress port ("drop and continue" 582 operation). Further there may exist tributary ingress ports ("add" 583 ports) whose signals are combined with each other and "continued" 584 line side signals. 586 In general to represent the routing properties of an FOADM we need a 587 fixed connectivity matrix Amn as previously discussed and we need the 588 precise wavelength restrictions for all ingress and egress ports. 589 From the wavelength restrictions on the tributary egress ports (drop 590 ports) we can see what wavelengths have been dropped. From the 591 wavelength restrictions on the tributary ingress (add) ports we can 592 see which wavelengths have been added to the line side egress port. 593 Finally from the added wavelength information and the line side 594 egress wavelength restrictions we can infer which wavelengths have 595 been continued. 597 To summarize, the modeling methodology introduced in section 3.3.1. 598 consisting of a connectivity matrix and port wavelength restrictions 599 can be used to describe a large set of fixed optical devices such as 600 combiners, splitters and FOADMs. Hybrid devices consisting of both 601 switched and fixed parts are modeled in [WSON-Info]. 603 3.4. Wavelength Converters 605 Wavelength converters take an ingress optical signal at one 606 wavelength and emit an equivalent content optical signal at another 607 wavelength on egress. There are currently two approaches to building 608 wavelength converters. One approach is based on optical to electrical 609 to optical (OEO) conversion with tunable lasers on egress. This 610 approach can be dependent upon the signal rate and format, i.e., this 611 is basically an electrical regenerator combined with a tunable laser. 612 The other approach performs the wavelength conversion, optically via 613 non-linear optical effects, similar in spirit to the familiar 614 frequency mixing used in radio frequency systems, but significantly 615 harder to implement. Such processes/effects may place limits on the 616 range of achievable conversion. These may depend on the wavelength of 617 the input signal and the properties of the converter as opposed to 618 only the properties of the converter in the OEO case. Different WSON 619 system designs may choose to utilize this component to varying 620 degrees or not at all. 622 Current or envisioned contexts for wavelength converters are: 624 1. Wavelength conversion associated with OEO switches and tunable 625 laser transmitters. In this case there are plenty of converters to 626 go around since we can think of each tunable output laser 627 transmitter on an OEO switch as a potential wavelength converter. 629 2. Wavelength conversion associated with ROADMs/OXCs. In this case we 630 may have a limited amount of conversion available. Conversion could 631 be either all optical or via an OEO method. 633 3. Wavelength conversion associated with fixed devices such as FOADMs. 634 In this case we may have a limited amount of conversion. Also in 635 this case the conversion may be used as part of light path routing. 637 Based on the above contexts a tentative modeling approach for 638 wavelength converters could be as follows: 640 1. Wavelength converters can always be modeled as associated with 641 network elements. This includes fixed wavelength routing elements. 643 2. A network element may have full wavelength conversion capability, 644 i.e., any ingress port and wavelength, or a limited number of 645 wavelengths and ports. On a box with a limited number of 646 converters there also may exist restrictions on which ports can 647 reach the converters. Hence regardless of where the converters 648 actually are we can associate them with ingress ports. 650 3. Wavelength converters have range restrictions that are either 651 independent or dependent upon the ingress wavelength. [TBD: for 652 those that depend on ingress wavelength can we have a standard 653 formula? Also note that this type of converter introduces 654 additional optical impairments.] 656 4. Wavelength converters that are O-E-O based will have a restriction 657 based on the modulation format and transmission speed. 659 Note that since O-E-O wavelength converters also serve as 660 regenerators we can include regenerators in our model of wavelength 661 converters. O-E-O Regenerators come in three general types known as 662 1R, 2R, and 3R regenerators. 1R regenerators re-amplify the signal to 663 combat attenuation, 2R regenerators reshape as well as amplify the 664 signal, 3R regenerators amplify, reshape and retime the signal. As we 665 go from 1R to 3R regenerators the signal is ''cleaned up'' better but 666 at the same time the regeneration process becomes more dependent on 667 the signal characteristics such as format and rate. 669 In WSONs where wavelength converters are sparse we may actually see a 670 light path appear to loop or ''backtrack'' upon itself in order to 671 reach a wavelength converter prior to continuing on to its 672 destination. The lambda used on the "detour" out to the wavelength 673 converter would be different from that coming back from the "detour" 674 to the wavelength converter. 676 A model for an individual O-E-O wavelength converter would consist 677 of: 679 o Input lambda or frequency range 681 o Output lambda or frequency range 683 o Equivalent regeneration level (1R, 2R, 3R) 685 o Signal restrictions if a 2R or 3R regeneration: formats and rates 687 [FFS: Model for an all optical wavelength converter] 688 3.4.1. Wavelength Converter Pool Modeling 690 A WSON node may include multiple wavelength converters. These are 691 usually arranged into some type of pool to promote resource sharing. 692 There are a number of different approaches used in the design of 693 switches with converter pools. However, from the point of view of 694 path computation we need to know the following: 696 1. The nodes that support wavelength conversion. 698 2. The accessibility and availability of a wavelength converter to 699 convert from a given ingress wavelength on a particular ingress 700 port to a desired egress wavelength on a particular egress port. 702 3. Limitations on the types of signals that can be converted and the 703 conversions that can be performed. 705 To model point 2 above we can use a similar technique as used to 706 model ROADMs and optical switches, i.e., a matrices to indicate 707 possible connectivity along with wavelength constraints for 708 links/ports. Since wavelength converters are considered a scarce 709 resource we will also want our model to include as a minimum the 710 usage state of individual wavelength converters in the pool. Models 711 that incorporate more state to further reveal blocking conditions on 712 ingress or egress to particular converters are for further study. 714 We utilize a three stage model as shown schematically in Figure 2. In 715 this model we assume N ingress ports (fibers), P wavelength 716 converters, and M egress ports (fibers). Since not all ingress ports 717 can necessarily reach the converter pool, the model starts with a 718 wavelength pool ingress matrix WI(i,p) = {0,1} whether ingress port i 719 can reach potentially reach wavelength converter p. 721 Since not all wavelength can necessarily reach all the converters or 722 the converters may have limited input wavelength range we have a set 723 of ingress port constraints for each wavelength converter. Currently 724 we assume that a wavelength converter can only take a single 725 wavelength on input. We can model each wavelength converter ingress 726 port constraint via a wavelength set mechanism. 728 Next we have a state vector WC(j) = {0,1} dependent upon whether 729 wavelength converter j in the pool is in use. This is the only state 730 kept in the converter pool model. This state is not necessary for 731 modeling "fixed" transponder system, i.e., systems where there is no 732 sharing. In addition, this state information may be encoded in a 733 much more compact form depending on the overall connectivity 734 structure [WC-Pool]. 736 After that, we have a set of wavelength converter egress wavelength 737 constraints. These constraints indicate what wavelengths a particular 738 wavelength converter can generate or are restricted to generating due 739 to internal switch structure. 741 Finally, we have a wavelength pool egress matrix WE(p,k) = {0,1} 742 depending on whether the output from wavelength converter p can reach 743 egress port k. Examples of this method being used to model wavelength 744 converter pools for several switch architectures from the literature 745 are given in reference [WC-Pool]. 747 I1 +-------------+ +-------------+ E1 748 ----->| | +--------+ | |-----> 749 I2 | +------+ WC #1 +-------+ | E2 750 ----->| | +--------+ | |-----> 751 | Wavelength | | Wavelength | 752 | Converter | +--------+ | Converter | 753 | Pool +------+ WC #2 +-------+ Pool | 754 | | +--------+ | | 755 | Ingress | | Egress | 756 | Connection | . | Connection | 757 | Matrix | . | Matrix | 758 | | . | | 759 | | | | 760 IN | | +--------+ | | EM 761 ----->| +------+ WC #P +-------+ |-----> 762 | | +--------+ | | 763 +-------------+ ^ ^ +-------------+ 764 | | 765 | | 766 | | 767 | | 769 Ingress wavelength Egress wavelength 770 constraints for constraints for 771 each converter each converter 773 Figure 2 Schematic diagram of wavelength converter pool model. 775 Example: Shared Per Node 777 In Figure 3 below we show a simple optical switch in a four 778 wavelength DWDM system sharing wavelength converters in a general 779 "per node" fashion. 781 ___________ +------+ 782 | |--------------------------->| | 783 | |--------------------------->| C | 784 /| | |--------------------------->| o | E1 785 I1 /D+--->| |--------------------------->| m | 786 + e+--->| | | b |====> 787 ====>| M| | Optical | +-----------+ +----+ | i | 788 + u+--->| Switch | | WC Pool | |O S|-->| n | 789 \x+--->| | | +-----+ | |p w|-->| e | 790 \| | +----+->|WC #1|--+->|t i| | r | 791 | | | +-----+ | |i t| +------+ 792 | | | | |c c| +------+ 793 /| | | | +-----+ | |a h|-->| | 794 I2 /D+--->| +----+->|WC #2|--+->|l |-->| C | E2 795 + e+--->| | | +-----+ | | | | o | 796 ====>| M| | | +-----------+ +----+ | m |====> 797 + u+--->| | | b | 798 \x+--->| |--------------------------->| i | 799 \| | |--------------------------->| n | 800 | |--------------------------->| e | 801 |___________|--------------------------->| r | 802 +------+ 804 Figure 3 An optical switch featuring a shared per node wavelength 805 converter pool architecture. 807 In this case the ingress and egress pool matrices are simply: 809 +-----+ +-----+ 810 | 1 1 | | 1 1 | 811 WI =| |, WE =| | 812 | 1 1 | | 1 1 | 813 +-----+ +-----+ 815 Example: Shared Per Link 817 In Figure 4 we show a different wavelength pool architecture know as 818 "shared per fiber". In this case the ingress and egress pool matrices 819 are simply: 821 +-----+ +-----+ 822 | 1 0 | | 1 0 | 823 WI =| |, WE =| | 824 | 0 1 | | 0 1 | 825 +-----+ +-----+ 827 ___________ +------+ 828 | |--------------------------->| | 829 | |--------------------------->| C | 830 /| | |--------------------------->| o | E1 831 I1 /D+--->| |--------------------------->| m | 832 + e+--->| | | b |====> 833 ====>| M| | Optical | +-----------+ | i | 834 + u+--->| Switch | | WC Pool | | n | 835 \x+--->| | | +-----+ | | e | 836 \| | +----+->|WC #1|--+---------->| r | 837 | | | +-----+ | +------+ 838 | | | | +------+ 839 /| | | | +-----+ | | | 840 I2 /D+--->| +----+->|WC #2|--+---------->| C | E2 841 + e+--->| | | +-----+ | | o | 842 ====>| M| | | +-----------+ | m |====> 843 + u+--->| | | b | 844 \x+--->| |--------------------------->| i | 845 \| | |--------------------------->| n | 846 | |--------------------------->| e | 847 |___________|--------------------------->| r | 848 +------+ 849 Figure 4 An optical switch featuring a shared per fiber wavelength 850 converter pool architecture. 852 4. Routing and Wavelength Assignment and the Control Plane 854 In wavelength switched optical networks consisting of tunable lasers 855 and wavelength selective switches with wavelength converters on every 856 interface, path selection is similar to the MPLS and TDM circuit 857 switched cases in that the labels, in this case wavelengths 858 (lambdas), have only local significance. That is, a wavelength- 859 convertible network with full wavelength-conversion capability at 860 each node is equivalent to a circuit-switched TDM network with full 861 time slot interchange capability; thus, the routing problem needs to 862 be addressed only at the level of the traffic engineered (TE) link 863 choice, and wavelength assignment can be resolved locally by the 864 switches on a hop-by-hop basis. 866 However, in the limiting case of an optical network with no 867 wavelength converters, a light path (optical channel - OCh -) needs a 868 route from source to destination and must pick a single wavelength 869 that can be used along that path without "colliding" with the 870 wavelength used by any other light path that may share an optical 871 fiber. This is sometimes referred to as a "wavelength continuity 872 constraint". To ease up on this constraint while keeping network 873 costs in check a limited number of wavelength converters maybe 874 introduce at key points in the network [Chu03]. 876 In the general case of limited or no wavelength converters this 877 computation is known as the Routing and Wavelength Assignment (RWA) 878 problem [HZang00]. The "hardness" of this problem is well documented. 879 There, however, exist a number of reasonable approximate methods for 880 its solution [HZang00]. 882 The inputs to the basic RWA problem are the requested light paths 883 source and destination, the networks topology, the locations and 884 capabilities of any wavelength converters, and the wavelengths 885 available on each optical link. The output from an algorithm solving 886 the RWA problem is an explicit route through ROADMs, a wavelength for 887 the optical transmitter, and a set of locations (generally associated 888 with ROADMs or switches) where wavelength conversion is to occur and 889 the new wavelength to be used on each component link after that point 890 in the route. 892 It is to be noted that choice of specific RWA algorithm is out of the 893 scope for this document. However there are a number of different 894 approaches to dealing with the RWA algorithm that can affect the 895 division of effort between signaling, routing and PCE. 897 4.1. Architectural Approaches to RWA 899 Two general computational approaches are taken to solving the RWA 900 problem. Some algorithms utilize a two step procedure of path 901 selection followed by wavelength assignment, and others solve the 902 problem in a combined fashion. 904 In the following, three different ways of performing RWA in 905 conjunction with the control plane are considered. The choice of one 906 of these architectural approaches over another generally impacts the 907 demands placed on the various control plane protocols. 909 4.1.1. Combined RWA (R&WA) 911 In this case, a unique entity is in charge of performing routing and 912 wavelength assignment. This choice assumes that computational entity 913 has sufficient WSON network link/nodal information and topology to be 914 able to compute RWA. This solution relies on a sufficient knowledge 915 of network topology, of available network resources and of network 916 nodes capabilities. This knowledge has to be accessible to the entity 917 performing the routing and wavelength assignment. 919 This solution is compatible with most known RWA algorithms, and in 920 particular those concerned with network optimization. On the other 921 hand, this solution requires up-to-date and detailed network 922 information dissemination. 924 Such a computational entity could reside in two different logical 925 places: 927 o In a separate Path Computation Element (PCE) which hence owns the 928 complete and updated knowledge of network state and provides path 929 computation services to node. 931 o In the Ingress node, in that case all nodes have the R&WA 932 functionality; the knowledge of the network state is obtained by a 933 periodic flooding of information provided by the other nodes. 935 4.1.2. Separated R and WA (R+WA) 937 In this case a first entity performs routing, while a second performs 938 wavelength assignment. The first entity furnishes one or more paths 939 to the second entity that will perform wavelength assignment and 940 possibly final path selection. 942 As the entities computing the path and the wavelength assignment are 943 separated, this constrains the class of RWA algorithms that may be 944 implemented. Although it may seem that algorithms optimizing a joint 945 usage of the physical and spectral paths are excluded from this 946 solution, many practical optimization algorithms only consider a 947 limited set of possible paths, e.g., as computed via a k-shortest 948 path algorithm [Ozdaglar03]. Hence although there is no guarantee 949 that the selected final route and wavelength offers the optimal 950 solution by allowing multiple routes to pass to the wavelength 951 selection process reasonable optimization can be performed. 953 The entity performing the routing assignment needs the topology 954 information of the network, whereas the entity performing the 955 wavelength assignment needs information on the network's available 956 resources and on network node capabilities. 958 4.1.3. Routing and Distributed WA (R+DWA) 960 In this case a first entity performs routing, while wavelength 961 assignment is performed on a hop-by-hop manner along the previously 962 computed route. This mechanism relies on updating of a list of 963 potential wavelengths used to ensure conformance with the wavelength 964 continuity constraint. 966 As currently specified, the GMPLS protocol suite signaling protocol 967 can accommodate such an approach. Per [RFC3471], the Label Set 968 selection works according to an AND scheme. Each hop restricts the 969 Label Set sent to the next hop from the one received from the 970 previous hop by performing an AND operation between the wavelength 971 referred by the labels the message includes with the one available on 972 the ongoing interface. The constraint to perform this AND operation 973 is up to the node local policy (even if one expects a consistent 974 policy configuration throughout a given transparency domain). When 975 wavelength conversion is performed at an intermediate node, a new 976 Label Set is generated. The egress nodes selects one label in the 977 Label Set received at the node, which is also up to the node local 978 policy. 980 Depending on these policies a spectral assignment may not be found or 981 one consuming too many conversion resources relative to what a 982 dedicated wavelength assignment policy would have achieved. Hence, 983 this approach may generate higher blocking probabilities in a heavily 984 loaded network. 986 On the one hand, this solution may be empowered with some signaling 987 extensions to ease its functioning and possibly enhance its 988 performances relatively to blocking. Note that this approach requires 989 less information dissemination than the others. 991 The first entity may be a PCE or the ingress node of the LSP. This 992 solution is applicable inside networks where resource optimization is 993 not as critical. 995 4.2. Conveying information needed by RWA 997 The previous sections have characterized WSONs and lightpath 998 requests. In particular, high level models of the information used by 999 the RWA process were presented. We can view this information as 1000 either static, changing with hardware changes (including possibly 1001 failures), or dynamic, those that can change with subsequent 1002 lightpath provisioning. The timeliness in which an entity involved in 1003 the RWA process is notified of such changes is fairly situational. 1005 For example, for network restoration purposes, learning of a hardware 1006 failure or of new hardware coming online to provide restoration 1007 capability can be critical. 1008 Currently there are various methods for communicating RWA relevant 1009 information, these include, but are not limited to: 1011 o Existing control plane protocols such as GMPLS routing and 1012 signaling. Note that routing protocols can be used to convey both 1013 static and dynamic information. Static information currently 1014 conveyed includes items like router options and such. 1016 o Management protocols such as NetConf, SNMPv3, CLI, CORBA, or 1017 others. 1019 o Directory services and accompanying protocols. These are good for 1020 the dissemination of relatively static information. Not intended 1021 for dynamic information. 1023 o Other techniques for dynamic information: messaging straight from 1024 NEs to PCE to avoid flooding. This would be useful if the number 1025 of PCEs is significantly less than number of WSON NEs. Or other 1026 ways to limit flooding to "interested" NEs. 1028 Mechanisms to improve scaling of dynamic information: 1030 o Tailor message content to WSON. For example the use of wavelength 1031 ranges, or wavelength occupation bit maps. 1033 Utilize incremental updates if feasible. 1035 4.3. Lightpath Temporal Characteristics 1037 The temporal characteristics of a light path connection can affect 1038 the choice of solution to the RWA process. For our purposes here we 1039 look at the timeliness of connection establishment/teardown, and the 1040 duration of the connection. 1042 Connection Establishment/Teardown Timeliness can be thought of in 1043 approximately three time frames: 1045 1. Time Critical: For example those lightpath establishments used for 1046 restoration of service or other high priority real time service 1047 requests. 1049 2. Soft time bounds: This is a more typical new connection request. 1050 While expected to be responsive, there should be more time to take 1051 into account network optimization. 1053 3. Scheduled or Advanced reservations. Here lightpath connections are 1054 requested significantly ahead of their intended "in service" time. 1055 There is the potential for significant network optimization if 1056 multiple lightpaths can be computed concurrently to achieve network 1057 optimization objectives. 1059 Lightpath connection duration has typically been thought of as 1060 approximately three time frames: 1062 1. Dynamic: those lightpaths with relatively short duration (holding 1063 times). 1065 2. Pseudo-static: lightpaths with moderately long durations. 1067 3. Static: lightpaths with long durations. 1069 Different types of RWA algorithms have been developed for dealing 1070 with dynamic versus pseudo-static conditions. These can address 1071 service provider's needs for: (a) network optimization, (b) 1072 restoration, and (c) highly dynamic lightpath provisioning. 1074 Hence we can model timescale related lightpath requirements via the 1075 following notions: 1077 o Batch or Sequential light path connection requests 1079 o Timeliness of Connection establishment 1081 o Duration of lightpath connection 1083 5. Modeling Examples and Control Plane Use Cases 1085 This section provides examples of the fixed and switch optical node 1086 and wavelength constraint models of section 3. and WSON control plane 1087 use cases related to path computation, establishment, rerouting, and 1088 optimization. 1090 5.1. Network Modeling for GMPLS/PCE Control 1092 Consider a network containing three routers (R1 through R3), eight 1093 WSON nodes (N1 through N8) and 18 links (L1 through L18) and one OEO 1094 converter (O1) in a topology shown below. 1096 +--+ +--+ +--+ +--------+ 1097 +-L3-+N2+-L5-+ +--------L12--+N6+--L15--+ N8 +-- 1098 | +--+ |N4+-L8---+ +--+ ++--+---++ 1099 | | +-L9--+| | | | 1100 +--+ +-+-+ ++-+ || | L17 L18 1101 | ++-L1--+ | | ++++ +----L16---+ | | 1102 |R1| | N1| L7 |R2| | | | 1103 | ++-L2--+ | | ++-+ | ++---++ 1104 +--+ +-+-+ | | | + R3 | 1105 | +--+ ++-+ | | +-----+ 1106 +-L4-+N3+-L6-+N5+-L10-+ ++----+ 1107 +--+ | +--------L11--+ N7 +---- 1108 +--+ ++---++ 1109 | | 1110 L13 L14 1111 | | 1112 ++-+ | 1113 |O1+-+ 1114 +--+ 1115 5.1.1. Describing the WSON nodes 1117 The eight WSON nodes in this example have the following properties: 1119 o Nodes N1, N2, N3 have fixed OADMs (FOADMs) installed and can 1120 therefore only access a static and pre-defined set of wavelengths 1122 o All other nodes contain ROADMs and can therefore access all 1123 wavelengths. 1125 o Nodes N4, N5, N7 and N8 are multi-degree nodes, allowing any 1126 wavelength to be optically switched between any of the links. Note 1127 however, that this does not automatically apply to wavelengths 1128 that are being added or dropped at the particular node. 1130 o Node N4 is an exception to that: This node can switch any 1131 wavelength from its add/drop ports to any of its outgoing links 1132 (L5, L7 and L12 in this case) 1134 o The links from the routers are always only able to carry one 1135 wavelength with the exception of links L8 and L9 which are capable 1136 to add/drop any wavelength. 1138 o Node N7 contains an OEO transponder (O1) connected to the node via 1139 links L13 and L14. That transponder operates in 3R mode and does 1140 not change the wavelength of the signal. Assume that it can 1141 regenerate any of the client signals, however only for a specific 1142 wavelength. 1144 Given the above restrictions, the node information for the eight 1145 nodes can be expressed as follows: (where ID == identifier, SCM == 1146 switched connectivity matrix, and FCM == fixed connectivity matrix). 1148 +ID+SCM +FCM + 1149 | | |L1 |L2 |L3 |L4 | | |L1 |L2 |L3 |L4 | | 1150 | |L1 |0 |0 |0 |0 | |L1 |0 |0 |1 |0 | | 1151 |N1|L2 |0 |0 |0 |0 | |L2 |0 |0 |0 |1 | | 1152 | |L3 |0 |0 |0 |0 | |L3 |1 |0 |0 |1 | | 1153 | |L4 |0 |0 |0 |0 | |L4 |0 |1 |1 |0 | | 1154 +--+---+---+---+---+---+---+---+---+---+---+---+---+ 1155 | | |L3 |L5 | | | | |L3 |L5 | | | | 1156 |N2|L3 |0 |0 | | | |L3 |0 |1 | | | | 1157 | |L5 |0 |0 | | | |L5 |1 |0 | | | | 1158 +--+---+---+---+---+---+---+---+---+---+---+---+---+ 1159 | | |L4 |L6 | | | | |L4 |L6 | | | | 1160 |N3|L4 |0 |0 | | | |L4 |0 |1 | | | | 1161 | |L6 |0 |0 | | | |L6 |1 |0 | | | | 1162 +--+---+---+---+---+---+---+---+---+---+---+---+---+ 1163 | | |L5 |L7 |L8 |L9 |L12| |L5 |L7 |L8 |L9 |L12| 1164 | |L5 |0 |1 |1 |1 |1 |L5 |0 |0 |0 |0 |0 | 1165 |N4|L7 |1 |0 |1 |1 |1 |L7 |0 |0 |0 |0 |0 | 1166 | |L8 |1 |1 |0 |1 |1 |L8 |0 |0 |0 |0 |0 | 1167 | |L9 |1 |1 |1 |0 |1 |L9 |0 |0 |0 |0 |0 | 1168 | |L12|1 |1 |1 |1 |0 |L12|0 |0 |0 |0 |0 | 1169 +--+---+---+---+---+---+---+---+---+---+---+---+---+ 1170 | | |L6 |L7 |L10|L11| | |L6 |L7 |L10|L11| | 1171 | |L6 |0 |1 |0 |1 | |L6 |0 |0 |1 |0 | | 1172 |N5|L7 |1 |0 |0 |1 | |L7 |0 |0 |0 |0 | | 1173 | |L10|0 |0 |0 |0 | |L10|1 |0 |0 |0 | | 1174 | |L11|1 |1 |0 |0 | |L11|0 |0 |0 |0 | | 1175 +--+---+---+---+---+---+---+---+---+---+---+---+---+ 1176 | | |L12|L15| | | | |L12|L15| | | | 1177 |N6|L12|0 |1 | | | |L12|0 |0 | | | | 1178 | |L15|1 |0 | | | |L15|0 |0 | | | | 1179 +--+---+---+---+---+---+---+---+---+---+---+---+---+ 1180 | | |L11|L13|L14|L16| | |L11|L13|L14|L16| | 1181 | |L11|0 |1 |0 |1 | |L11|0 |0 |0 |0 | | 1182 |N7|L13|1 |0 |0 |0 | |L13|0 |0 |1 |0 | | 1183 | |L14|0 |0 |0 |1 | |L14|0 |1 |0 |0 | | 1184 | |L16|1 |0 |1 |0 | |L16|0 |0 |1 |0 | | 1185 +--+---+---+---+---+---+---+---+---+---+---+---+---+ 1186 | | |L15|L16|L17|L18| | |L15|L16|L17|L18| | 1187 | |L15|0 |1 |0 |0 | |L15|0 |0 |0 |1 | | 1188 |N8|L16|1 |0 |0 |0 | |L16|0 |0 |1 |0 | | 1189 | |L17|0 |0 |0 |0 | |L17|0 |1 |0 |0 | | 1190 | |L18|0 |0 |0 |0 | |L18|1 |0 |1 |0 | | 1191 +--+---+---+---+---+---+---+---+---+---+---+---+---+ 1193 5.1.2. Describing the links 1195 For the following discussion some simplifying assumptions are made: 1197 o It is assumed that the WSON node support a total of four 1198 wavelengths designated WL1 through WL4. 1200 o It is assumed that the impairment feasibility of a path or path 1201 segment is independent from the wavelength chosen. 1203 For the discussion of the RWA operation to build LSPs between two 1204 routers, the wavelength constraints on the links between the routers 1205 and the WSON nodes as well as the connectivity matrix of these links 1206 needs to be specified: 1208 +Link+WLs supported +Possible egress links+ 1209 | L1 | WL1 | L3 | 1210 +----+-----------------+---------------------+ 1211 | L2 | WL2 | L4 | 1212 +----+-----------------+---------------------+ 1213 | L8 | WL1 WL2 WL3 WL4 | L5 L7 L12 | 1214 +----+-----------------+---------------------+ 1215 | L9 | WL1 WL2 WL3 WL4 | L5 L7 L12 | 1216 +----+-----------------+---------------------+ 1217 | L10| WL2 | L6 | 1218 +----+-----------------+---------------------+ 1219 | L13| WL1 WL2 WL3 WL4 | L11 L14 | 1220 +----+-----------------+---------------------+ 1221 | L14| WL1 WL2 WL3 WL4 | L13 L16 | 1222 +----+-----------------+---------------------+ 1223 | L17| WL2 | L16 | 1224 +----+-----------------+---------------------+ 1225 | L18| WL1 | L15 | 1226 +----+-----------------+---------------------+ 1228 Note that the possible egress links for the links connecting to the 1229 routers is inferred from the Switched Connectivity Matrix and the 1230 Fixed Connectivity Matrix of the Nodes N1 through N8 and is show here 1231 for convenience, i.e., this information does not need to be repeated. 1233 5.2. RWA Path Computation and Establishment 1235 The calculation of optical impairment feasible routes is outside the 1236 scope of this framework document. In general impairment feasible 1237 routes serve as an input to the RWA algorithm. 1239 For the example use case shown here, assume the following feasible 1240 routes: 1242 +Endpoint 1+Endpoint 2+Feasible Route + 1243 | R1 | R2 | L1 L3 L5 L8 | 1244 | R1 | R2 | L1 L3 L5 L9 | 1245 | R1 | R2 | L2 L4 L6 L7 L8 | 1246 | R1 | R2 | L2 L4 L6 L7 L9 | 1247 | R1 | R2 | L2 L4 L6 L10 | 1248 | R1 | R3 | L1 L3 L5 L12 L15 L18 | 1249 | R1 | N7 | L2 L4 L6 L11 | 1250 | N7 | R3 | L16 L17 | 1251 | N7 | R2 | L16 L15 L12 L9 | 1252 | R2 | R3 | L8 L12 L15 L18 | 1253 | R2 | R3 | L8 L7 L11 L16 L17 | 1254 | R2 | R3 | L9 L12 L15 L18 | 1255 | R2 | R3 | L9 L7 L11 L16 L17 | 1257 Given a request to establish a LSP between R1 and R2 the RWA 1258 algorithm finds the following possible solutions: 1260 +WL + Path + 1261 | WL1| L1 L3 L5 L8 | 1262 | WL1| L1 L3 L5 L9 | 1263 | WL2| L2 L4 L6 L7 L8| 1264 | WL2| L2 L4 L6 L7 L9| 1265 | WL2| L2 L4 L6 L10 | 1267 Assume now that the RWA chooses WL1 and the Path L1 L3 L5 L8 for the 1268 requested LSP. 1270 Next, another LSP is signaled from R1 to R2. Given the established 1271 LSP using WL1, the following table shows the available paths: 1273 +WL + Path + 1274 | WL2| L2 L4 L6 L7 L9| 1275 | WL2| L2 L4 L6 L10 | 1277 Assume now that the RWA chooses WL2 and the path L2 L4 L6 L7 L9 for 1278 the establishment of the new LSP. 1280 Faced with another LSP request -this time from R2 to R3 - can not be 1281 fulfilled since the only four possible paths (starting at L8 and L9) 1282 are already in use. 1284 5.3. Resource Optimization 1286 The preceding example gives rise to another use case: The 1287 optimization of network resources. Optimization can be achieved on a 1288 number of layers (e.g. through electrical or optical multiplexing of 1289 client signals) or by re-optimizing the solutions found by the RWA 1290 algorithm. 1292 Given the above example again, assume that the RWA algorithm should 1293 find a path between R2 and R3. The only possible path to reach R3 1294 from R2 needs to use L9. L9 however is blocked by one of the LSPs 1295 from R1. 1297 5.4. Support for Rerouting 1299 It is also envisioned that the extensions to GMPLS and PCE support 1300 rerouting of wavelengths in case of failures. 1302 Assume for this discussion that the only two LSPs in use in the 1303 system are: 1305 LSP1: WL1 L1 L3 L5 L8 1307 LSP2: WL2 L2 L4 L6 L7 L9 1309 Assume furthermore that the link L5 fails. The RWA can now find the 1310 following alternate path and and establish that path: 1312 R1 -> N7 -> R2 1314 Level 3 regeneration will take place at N7, so that the complete path 1315 looks like this: 1317 R1 -> L2 L4 L6 L11 L13 -> O1 -> L14 L16 L15 L12 L9 -> R2 1319 6. GMPLS & PCE Implications 1321 The presence and amount of wavelength conversion available at a 1322 wavelength switching interface has an impact on the information that 1323 needs to be transferred by the control plane (GMPLS) and the PCE 1324 architecture. Current GMPLS and PCE standards can address the full 1325 wavelength conversion case so the following will only address the 1326 limited and no wavelength conversion cases. 1328 6.1. Implications for GMPLS signaling 1330 Basic support for WSON signaling already exists in GMPLS with the 1331 lambda (value 9) LSP encoding type [RFC3471], or for G.709 compatible 1332 optical channels, the LSP encoding type (value = 13) "G.709 Optical 1333 Channel" from [RFC4328]. However a number of practical issues arise 1334 in the identification of wavelengths and signals, and distributed 1335 wavelength assignment processes which are discussed below. 1337 6.1.1. Identifying Wavelengths and Signals 1339 As previously stated a global fixed mapping between wavelengths and 1340 labels simplifies the characterization of WDM links and WSON devices. 1341 Furthermore such a mapping as described in [Otani] eases 1342 communication between PCE and WSON PCCs. 1344 An alternative to a global network map of labels to wavelengths would 1345 be to use LMP to assign the map for each link then convey that 1346 information to any path computation entities, e.g., label switch 1347 routers or stand alone PCEs. The local label map approach will 1348 require the label-set contents in the RSVP-TE Path message to be 1349 translated every time the map changes between an incoming link and 1350 the outgoing link. 1352 In the future, it maybe worthwhile to define traffic parameters for 1353 lambda LSPs that include a signal type field that includes modulation 1354 format/rate information. This is similar to what was done in 1355 reference [RFC4606] for SONET/SDH signal types. 1357 6.1.2. Combined RWA/Separate Routing WA support 1359 In either the combined RWA or separate routing WA cases, the node 1360 initiating the signaling will have a route from the source to 1361 destination along with the wavelengths (generalized labels) to be 1362 used along portions of the path. Current GMPLS signaling supports an 1363 explicit route object (ERO) and within an ERO an ERO Label subobject 1364 can be use to indicate the wavelength to be used at a particular 1365 node. In case the local label map approach is used the label sub- 1366 object entry in the ERO has to be translated appropriately. 1368 6.1.3. Distributed Wavelength Assignment: Unidirectional, No 1369 Converters 1371 GMPLS signaling for a uni-directional lightpath LSP allows for the 1372 use of a label set object in the RSVP-TE path message. The processing 1373 of the label set object to take the intersection of available lambdas 1374 along a path can be performed resulting in the set of available 1375 lambda being known to the destination that can then use a wavelength 1376 selection algorithm to choose a lambda. For example, the following is 1377 a non-exhaustive subset of wavelength assignment (WA) approaches 1378 discussed in [HZang00]: 1380 1. Random: Looks at all available wavelengths for the light path then 1381 chooses from those available at random. 1383 2. First Fit: Wavelengths are ordered, first available (on all links) 1384 is chosen. 1386 3. Most Used: Out of the wavelengths available on the path attempts 1387 to select most use wavelength in network. 1389 4. Least Loaded: For multi-fiber networks. Chooses the wavelength j 1390 that maximizes minimum of the difference between the number of 1391 fibers on link l and the number of fibers on link l with 1392 wavelength j occupied. 1394 As can be seen from the above short list, wavelength assignment 1395 methods have differing information or processing requirements. The 1396 information requirements of these methods are as follows: 1398 1. Random: nothing more than the available wavelength set. 1400 2. First Fit: nothing more than the available wavelength set. 1402 3. Most Used: the available wavelength set and information on global 1403 wavelength use in the network. 1405 4. Least Loaded: the available wavelength set and information 1406 concerning the wavelength dependent loading for each link (this 1407 applies to multi-fiber links). This could be obtained via global 1408 information or via supplemental information passed via the 1409 signaling protocol. 1411 In case (3) above the global information needed by the wavelength 1412 assignment could be derived from suitably enhanced GMPLS routing. 1413 Note however this information need not be accurate enough for 1414 combined RWA computation. Currently, GMPLS signaling does not provide 1415 a way to indicate that a particular wavelength assignment algorithm 1416 should be used. 1418 6.1.4. Distributed Wavelength Assignment: Unidirectional, Limited 1419 Converters 1421 The previous outlined the case with no wavelength converters. In the 1422 case of wavelength converters, nodes with wavelength converters would 1423 need to make the decision as to whether to perform conversion. One 1424 indicator for this would be that the set of available wavelengths 1425 which is obtained via the intersection of the incoming label set and 1426 the egress links available wavelengths is either null or deemed too 1427 small to permit successful completion. 1429 At this point the node would need to remember that it will apply 1430 wavelength conversion and will be responsible for assigning the 1431 wavelength on the previous lambda-contiguous segment when the RSVP-TE 1432 RESV message passes by. The node will pass on an enlarged label set 1433 reflecting only the limitations of the wavelength converter and the 1434 egress link. The record route option in RVSP-TE signaling can be used 1435 to show where wavelength conversion has taken place. 1437 6.1.5. Distributed Wavelength Assignment: Bidirectional, No 1438 Converters 1440 There are potential issues in the case of a bi-directional lightpath 1441 which requires the use of the same lambda in both directions. We can 1442 try to use the above procedure to determine the available 1443 bidirectional lambda set if we use the interpretation that the 1444 available label set is available in both directions. However, a 1445 problem, arises in that bidirectional LSPs setup, according to 1446 [RFC3471] section 4.1, is indicated by the presence of an upstream 1447 label in the path message. 1449 However, until the intersection of the available label sets is 1450 obtained, e.g., at the destination node and the wavelength assignment 1451 algorithm has been run the upstream label information will not be 1452 available. Hence currently distributed wavelength assignment with 1453 bidirectional lightpaths is not supported. 1455 6.2. Implications for GMPLS Routing 1457 GMPLS routing [RFC4202] currently defines an interface capability 1458 descriptor for "lambda switch capable" (LSC) which we can use to 1459 describe the interfaces on a ROADM or other type of wavelength 1460 selective switch. In addition to the topology information typically 1461 conveyed via an IGP, we would need to convey the following subsystem 1462 properties to minimally characterize a WSON: 1464 1. WDM Link properties (allowed wavelengths). 1466 2. Laser Transmitters (wavelength range). 1468 3. ROADM/FOADM properties (connectivity matrix, port wavelength 1469 restrictions). 1471 4. Wavelength Converter properties (per network element, may change if 1472 a common limited shared pool is used). 1474 In most cases we should be able to combine items (1) and (2) into the 1475 information in item (3). Except for the number of wavelength 1476 converters that are available in a shared pool, and the previous 1477 information is fairly static. In the next two sections we discuss 1478 dynamic available link bandwidth information. 1480 6.2.1. Need for Wavelength-Specific Maximum Bandwidth Information 1482 Difficulties are encountered when trying to use the bandwidth 1483 accounting methods of [RFC4202] and [RFC3630] to describe the 1484 availability of wavelengths on a WDM link. The current RFCs give 1485 three link resource measures: Maximum Bandwidth, Maximum Reservable 1486 Bandwidth, and Unreserved Bandwidth. Although these can be used to 1487 describe a WDM span they do not provide the fundamental information 1488 needed for RWA. We are not given the maximum bandwidth per wavelength 1489 for the span. If we did then we could use the aforementioned measures 1490 to tell us the maximum wavelength count and the number of available 1491 wavelengths. 1493 For example, suppose we have a 32 channel WDM span, and that the 1494 system in general supports ITU-T NRZ signals up to NRZ 10Gbps. 1495 Further suppose that the first 20 channels are carrying 1Gbps 1496 Ethernet, then the maximum bandwidth would be 320Gbps and the maximum 1497 reservable bandwidth would be 120Gbps (12 wavelengths). 1498 Alternatively, consider the case where the first 8 channels are 1499 carrying 2.5Gbps SDH STM-16 channels, then the maximum bandwidth 1500 would still be 320Gbps and the maximum reservable bandwidth would be 1501 240Gbps (24 wavelengths). 1503 Such information would be useful in the routing with distributed WA 1504 approach of section 4.1.3. 1506 6.2.2. Need for Wavelength-Specific Availability Information 1508 Even if we know the number of available wavelengths on a link, we 1509 actually need to know which specific wavelengths are available and 1510 which are occupied if we are going to run a combined RWA process or 1511 separate WA process as discussed in sections 4.1.1. 4.1.2. This is 1512 currently not possible with GMPLS routing extensions. 1514 In the routing extensions for GMPLS [RFC4202], requirements for 1515 layer-specific TE attributes are discussed. The RWA problem for 1516 optical networks without wavelength converters imposes an additional 1517 requirement for the lambda (or optical channel) layer: that of 1518 knowing which specific wavelengths are in use. Note that current 1519 dense WDM (DWDM) systems range from 16 channels to 128 channels with 1520 advanced laboratory systems with as many as 300 channels. Given these 1521 channel limitations and if we take the approach of a global 1522 wavelength to label mapping or furnishing the local mappings to the 1523 PCEs then representing the use of wavelengths via a simple bit-map is 1524 feasible. 1526 6.2.3. Relationship to Link Bundling and Layering 1528 When dealing with static DWDM systems, particularly from a SONET/SDH 1529 or G.709 digital wrapper layer, each lambda looks like a separate 1530 link. Typically a bunch of unnumbered links, as supported in GMPLS 1531 routing extensions [RFC4202], would be used to describe a static DWDM 1532 system. In addition these links can be bundled into a TE link 1533 ([RFC4202], [RFC4201]) for more efficient dissemination of resource 1534 information. However, in the case discussed here we want to control a 1535 dynamic WDM layer and must deal with wavelengths as labels and not 1536 just as links or component links from the perspective of an upper 1537 (client) layer. In addition, a typical point to point optical cable 1538 contains many optical fibers and hence it may be desirable to bundle 1539 these separate fibers into a TE link. Note that in the no wavelength 1540 conversion or limited wavelength conversion situations that we will 1541 need information on wavelength usage on the individual component 1542 links. 1544 6.2.4. WSON Routing Information Summary 1546 The following table summarizes the WSON information that could be 1547 conveyed via GMPLS routing and attempts to classify that information 1548 as to its static or dynamic nature and whether that information would 1549 tend to be associated with either a link or a node. 1551 Information Static/Dynamic Node/Link 1552 ------------------------------------------------------------------ 1553 Connectivity matrix Static Node 1554 Per port wavelength restrictions Static Node(1) 1555 WDM link (fiber) lambda ranges Static Link 1556 WDM link channel spacing Static Link 1557 Laser Transmitter range Static Link(2) 1558 Wavelength conversion capabilities Static(3) Node 1559 Maximum bandwidth per Wavelength Static Link 1560 Wavelength Availability Dynamic(4) Link 1562 Notes: 1564 1. These are the per port wavelength restrictions of an optical 1565 device such as a ROADM and are independent of any optical 1566 constraints imposed by a fiber link. 1568 2. This could also be viewed as a node capability. 1570 3. This could be dynamic in the case of a limited pool of converters 1571 where the number available can change with connection 1572 establishment. Note we may want to include regeneration 1573 capabilities here since OEO converters are also regenerators. 1575 4. Not necessarily needed in the case of distributed wavelength 1576 assignment via signaling. 1578 While the full complement of the information from the previous table 1579 is needed in the Combined RWA and the separate Routing and WA 1580 architectures, in the case of Routing + distribute WA via signaling 1581 we only need the following information: 1583 Information Static/Dynamic Node/Link 1584 ------------------------------------------------------------------ 1585 Connectivity matrix Static Node 1586 Wavelength conversion capabilities Static(3) Node 1588 Information models and compact encodings for this information is 1589 provided in [WSON-Info]. 1591 6.3. Optical Path Computation and Implications for PCE 1593 As previously noted the RWA problem can be computationally intensive 1594 [HZang00]. Such computationally intensive path computations and 1595 optimizations were part of the impetus for the PCE (path computation 1596 element) architecture. 1598 As the PCEP defines the procedures necessary to support both 1599 sequential [PCEP] and global concurrent path computations [PCE-GCO], 1600 PCE is well positioned to support WSON-enabled RWA computation with 1601 some protocol enhancement. 1603 Implications for PCE generally fall into two main categories: (a) 1604 lightpath constraints and characteristics, (b) computation 1605 architectures. 1607 6.3.1. Lightpath Constraints and Characteristics 1609 For the varying degrees of optimization that may be encountered in a 1610 network the following models of bulk and sequential lightpath 1611 requests are encountered: 1613 o Batch optimization, multiple lightpaths requested at one time. 1615 o Lightpath(s) and backup lightpath(s) requested at one time. 1617 o Single lightpath requested at a time. 1619 PCEP and PCE-GCO can be readily enhanced to support all of the 1620 potential models of RWA computation. 1622 Lightpath constraints include: 1624 o Bidirectional Assignment of wavelengths 1626 o Possible simultaneous assignment of wavelength to primary and 1627 backup paths. 1629 o Tuning range constraint on optical transmitter. 1631 Lightpath characteristics can include: 1633 o Duration information (how long this connection may last) 1635 o Timeliness/Urgency information (how quickly is this connection 1636 needed) 1638 6.3.2. Computation Architecture Implications 1640 When a PCE performs a combined RWA computation per section 4.1.1. it 1641 requires accurate an up to date wavelength utilization on all links 1642 in the network. 1644 When a PCE is used to perform wavelength assignment (WA) in the 1645 separate routing WA architecture then the entity requesting WA needs 1646 to furnish the pre-selected route to the PCE as well as any of the 1647 lightpath constraints/characteristics previously mentioned. This 1648 architecture also requires the PCE performing WA to have accurate and 1649 up to date network wavelength utilization information. 1651 When a PCE is used to perform routing in a routing with distribute WA 1652 architecture, then the PCE does not necessarily need the most up to 1653 date network wavelength utilization information, however timely 1654 information can contributed to reducing failed signaling attempts 1655 related to blocking. 1657 6.3.3. Discovery of RWA Capable PCEs 1659 The algorithms and network information needed for solving the RWA are 1660 somewhat specialized and computationally intensive hence not all PCEs 1661 within a domain would necessarily need or want this capability. 1662 Hence, it would be useful via the mechanisms being established for 1663 PCE discovery [RFC5088] to indicate that a PCE has the ability to 1664 deal with the RWA problem. Reference [RFC5088] indicates that a sub- 1665 TLV could be allocated for this purpose. 1667 Recent progress on objective functions in PCE [PCE-OF] would allow 1668 the operators to flexibly request differing objective functions per 1669 their need and applications. For instance, this would allow the 1670 operator to choose an objective function that minimizes the total 1671 network cost associated with setting up a set of paths concurrently. 1672 This would also allow operators to choose an objective function that 1673 results in a most evenly distributed link utilization. 1675 This implies that PCEP would easily accommodate wavelength selection 1676 algorithm in its objective function to be able to optimize the path 1677 computation from the perspective of wavelength assignment if chosen 1678 by the operators. 1680 6.4. Scaling Implications 1682 This section provides a summary of the scaling issue for WSON 1683 routing, signaling and path computation introduced by the concepts 1684 discussed in this document. 1686 6.4.1. Routing 1688 In large WSONs label availability and cross connect capability 1689 information being advertised may generate a significant amount of 1690 routing information. 1692 6.4.2. Signaling 1694 When dealing with a large number of simultaneous end-to-end 1695 wavelength service requests and service deletions the network may 1696 have to process a significant number of forward and backward service 1697 messages. Also, similar situation possibly happens in the case of 1698 link or node failure, if the WSON support dynamic restoration 1699 capability. 1701 6.4.3. Path computation 1703 If a PCE is handling path computation requests for end-to-end 1704 wavelength services within the WSON, then the complexity of the 1705 network and number of service path computation requests being sent to 1706 the PCE may have an impact on the PCEs ability to process requests in 1707 a timely manner. 1709 6.5. Summary of Impacts by RWA Architecture 1711 The following table summarizes for each RWA strategy the list of 1712 mandatory ("M") and optional ("O") control plane features according 1713 to GMPLS architectural blocks: 1715 o Information required by the path computation entity, 1717 o LSP request parameters used in either PCC to PCE situations or in 1718 signaling, 1720 o RSVP-TE LSP signaling parameters used in LSP establishment. 1722 The table shows which enhancements are common to all architectures 1723 (R&WA, R+WA, R+DWA), which apply only to R&WA and R+WA (R+&WA), and 1724 which apply only to R+DWA. 1726 +-------------------------------------+-----+-------+-------+-------+ 1727 | | |Common | R+&WA | R+DWA | 1728 | Feature | ref +---+---+---+---+---+---+ 1729 | | | M | O | M | O | M | O | 1730 +-------------------------------------+-----+---+---+---+---+---+---+ 1731 | Generalized Label for Wavelength |5.1.1| x | | | | | | 1732 +-------------------------------------+-----+---+---+---+---+---+---+ 1733 | Flooding of information for the | | | | | | | | 1734 | routing phase | | | | | | | | 1735 | Node features | 3.3 | | | | | | | 1736 | Node type | | | x | | | | | 1737 | spectral X-connect constraint | | | | x | | | | 1738 | port X-connect constraint | | | | x | | | | 1739 | Transponders availability | | | x | | | | | 1740 | Transponders features | 3.2 | | x | | | | | 1741 | Converter availability | | | | x | | | | 1742 | Converter features | 3.4 | | | x | | | x | 1743 | TE-parameters of WDM links | 3.1 | x | | | | | | 1744 | Total Number of wavelength | | x | | | | | | 1745 | Number of wavelengths available | | x | | | | | | 1746 | Grid spacing | | x | | | | | | 1747 | Wavelength availability on links | 5.2 | | | x | | | | 1748 +-------------------------------------+-----+---+---+---+---+---+---+ 1749 | LSP request parameters | | | | | | | | 1750 | Signal features | 5.1 | | x | | | x | | 1751 | Modulation format | | | x | | | x | | 1752 | Modulation parameters | | | x | | | x | | 1753 | Specification of RWA method | 5.1 | | x | | | x | | 1754 | LSP time features | 4.3 | | x | | | | | 1755 +-------------------------------------+-----+---+---+---+---+---+---+ 1756 | Enriching signaling messages | | | | | | | | 1757 | Signal features | 5.1 | | | | | x | | 1758 +-------------------------------------+-----+---+---+---+---+---+---+ 1760 7. Security Considerations 1762 This document has no requirement for a change to the security models 1763 within GMPLS and associated protocols. That is the OSPF-TE, RSVP-TE, 1764 and PCEP security models could be operated unchanged. 1766 However satisfying the requirements for RWA using the existing 1767 protocols may significantly affect the loading of those protocols. 1768 This makes the operation of the network more vulnerable to denial of 1769 service attacks. Therefore additional care maybe required to ensure 1770 that the protocols are secure in the WSON environment. 1772 Furthermore the additional information distributed in order to 1773 address the RWA problem represents a disclosure of network 1774 capabilities that an operator may wish to keep private. Consideration 1775 should be given to securing this information. 1777 8. IANA Considerations 1779 This document makes no request for IANA actions. 1781 9. Acknowledgments 1783 The authors would like to thank Adrian Farrel for many helpful 1784 comments that greatly improved the contents of this draft. 1786 This document was prepared using 2-Word-v2.0.template.dot. 1788 10. References 1790 10.1. Normative References 1792 [RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching 1793 (GMPLS) Signaling Functional Description", RFC 3471, 1794 January 2003. 1796 [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 1797 (TE) Extensions to OSPF Version 2", RFC 3630, September 1798 2003. 1800 [RFC3945] Mannie, E., "Generalized Multi-Protocol Label Switching 1801 (GMPLS) Architecture", RFC 3945, October 2004. 1803 [RFC4201] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in 1804 MPLS Traffic Engineering (TE)", RFC 4201, October 2005. 1806 [RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in Support 1807 of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 1808 4202, October 2005. 1810 [RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label 1811 Switching (GMPLS) Signaling Extensions for G.709 Optical 1812 Transport Networks Control", RFC 4328, January 2006. 1814 [G.694.1] ITU-T Recommendation G.694.1, "Spectral grids for WDM 1815 applications: DWDM frequency grid", June, 2002. 1817 [RFC5088] J.L. Le Roux, J.P. Vasseur, Yuichi Ikejiri, and Raymond 1818 Zhang, "OSPF protocol extensions for Path Computation 1819 Element (PCE) Discovery", January 2008. 1821 [PCE-GCO] Y. Lee, J.L. Le Roux, D. King, and E. Oki, "Path 1822 Computation Element Communication Protocol (PCECP) 1823 Requirements and Protocol Extensions In Support of Global 1824 Concurrent Optimization", work in progress, draft-ietf-pce- 1825 global-concurrent-optimization-08.txt, January 2009. 1827 [PCEP] J.P. Vasseur and J.L. Le Roux (Editors), "Path Computation 1828 Element (PCE) Communication Protocol (PCEP)", work in 1829 progress, draft-ietf-pce-pcep-19.txt, November 2008. 1831 [PCE-OF] J.L. Le Roux, J.P. Vasseur, and Y. Lee, "Encoding of 1832 Objective Functions in Path Computation Element (PCE) 1833 communication and discovery protocols", work in progress, 1834 draft-ietf-pce-of-06.txt, December 2008. 1836 [WSON-Encode] G. Bernstein, Y. Lee, D. Li, and W. Imajuku, "Routing 1837 and Wavelength Assignment Information Encoding for 1838 Wavelength Switched Optical Networks", draft-bernstein- 1839 ccamp-wson-encode-01.txt, November 2008. 1841 [WSON-Info] G. Bernstein, Y. Lee, D. Li, W. Imajuku," Routing and 1842 Wavelength Assignment Information for Wavelength Switched 1843 Optical Networks", draft-bernstein-ccamp-wson-info-03.txt, 1844 July, 2008. 1846 10.2. Informative References 1848 [HZang00] H. Zang, J. Jue and B. Mukherjeee, "A review of routing and 1849 wavelength assignment approaches for wavelength-routed 1850 optical WDM networks", Optical Networks Magazine, January 1851 2000. 1853 [Coldren04] Larry A. Coldren, G. A. Fish, Y. Akulova, J. S. 1854 Barton, L. Johansson and C. W. Coldren, "Tunable 1855 Seiconductor Lasers: A Tutorial", Journal of Lightwave 1856 Technology, vol. 22, no. 1, pp. 193-202, January 2004. 1858 [Chu03] Xiaowen Chu, Bo Li and Chlamtac I, "Wavelength converter 1859 placement under different RWA algorithms in wavelength- 1860 routed all-optical networks", IEEE Transactions on 1861 Communications, vol. 51, no. 4, pp. 607-617, April 2003. 1863 [Buus06] Jens Buus EJM, "Tunable Lasers in Optical Networks", 1864 Journal of Lightware Technology, vol. 24, no. 1, pp. 5-11, 1865 January 2006. 1867 [Basch06] E. Bert Bash, Roman Egorov, Steven Gringeri and Stuart 1868 Elby, "Architectural Tradeoffs for Reconfigurable Dense 1869 Wavelength-Division Multiplexing Systems", IEEE Journal of 1870 Selected Topics in Quantum Electronics, vol. 12, no. 4, pp. 1871 615-626, July/August 2006. 1873 [Otani] T. Otani, H. Guo, K. Miyazaki, D. Caviglia, "Generalized 1874 Labels of Lambda-Switching Capable Label Switching Routers 1875 (LSR)", work in progress: draft-otani-ccamp-gmpls-lambda- 1876 labels-02.txt, November 2007. 1878 [Winzer06] Peter J. Winzer and Rene-Jean Essiambre, "Advanced 1879 Optical Modulation Formats", Proceedings of the IEEE, vol. 1880 94, no. 5, pp. 952-985, May 2006. 1882 [G.652] ITU-T Recommendation G.652, Characteristics of a single-mode 1883 optical fibre and cable, June 2005. 1885 [G.653] ITU-T Recommendation G.653, Characteristics of a dispersion- 1886 shifted single-mode optical fibre and cable, December 2006. 1888 [G.654] ITU-T Recommendation G.654, Characteristics of a cut-off 1889 shifted single-mode optical fibre and cable, December 2006. 1891 [G.655] ITU-T Recommendation G.655, Characteristics of a non-zero 1892 dispersion-shifted single-mode optical fibre and cable, 1893 March 2006. 1895 [G.656] ITU-T Recommendation G.656, Characteristics of a fibre and 1896 cable with non-zero dispersion for wideband optical 1897 transport, December 2006. 1899 [G.671] ITU-T Recommendation G.671, Transmission characteristics of 1900 optical components and subsystems, January 2005. 1902 [G.872] ITU-T Recommendation G.872, Architecture of optical 1903 transport networks, November 2001. 1905 [G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network 1906 Physical Layer Interfaces, March 2006. 1908 [G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM 1909 applications: DWDM frequency grid, June 2002. 1911 [G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM 1912 applications: CWDM wavelength grid, December 2003. 1914 [G.Sup39] ITU-T Series G Supplement 39, Optical system design and 1915 engineering considerations, February 2006. 1917 [G.Sup43] ITU-T Series G Supplement 43, Transport of IEEE 10G base-R 1918 in optical transport networks (OTN), November 2006. 1920 [Imajuku] W. Imajuku, Y. Sone, I. Nishioka, S. Seno, "Routing 1921 Extensions to Support Network Elements with Switching 1922 Constraint", work in progress: draft-imajuku-ccamp-rtg- 1923 switching-constraint-02.txt, July 2007. 1925 [Ozdaglar03] Asuman E. Ozdaglar and Dimitri P. Bertsekas, ''Routing 1926 and wavelength assignment in optical networks,'' IEEE/ACM 1927 Transactions on Networking, vol. 11, 2003, pp. 259 -272. 1929 [RFC4054] Strand, J. and A. Chiu, "Impairments and Other Constraints 1930 on Optical Layer Routing", RFC 4054, May 2005. 1932 [RFC4606] Mannie, E. and D. Papadimitriou, "Generalized Multi- 1933 Protocol Label Switching (GMPLS) Extensions for Synchronous 1934 Optical Network (SONET) and Synchronous Digital Hierarchy 1935 (SDH) Control", RFC 4606, August 2006. 1937 [WC-Pool] G. Bernstein, Y. Lee, "Modeling WDM Switching Systems 1938 including Wavelength Converters" to appear www.grotto- 1939 networking.com, 2008. 1941 11. Contributors 1943 Snigdho Bardalai 1944 Fujitsu 1945 Email: Snigdho.Bardalai@us.fujitsu.com 1947 Diego Caviglia 1948 Ericsson 1949 Via A. Negrone 1/A 16153 1950 Genoa Italy 1952 Phone: +39 010 600 3736 1953 Email: diego.caviglia@(marconi.com, ericsson.com) 1955 Daniel King 1956 Aria Networks 1957 Email: daniel.king@aria-networks.com 1959 Itaru Nishioka 1960 NEC Corp. 1961 1753 Simonumabe, Nakahara-ku, Kawasaki, Kanagawa 211-8666 1962 Japan 1963 Phone: +81 44 396 3287 1964 Email: i-nishioka@cb.jp.nec.com 1966 Lyndon Ong 1967 Ciena 1968 Email: Lyong@Ciena.com 1970 Pierre Peloso 1971 Alcatel-Lucent 1972 Route de Villejust - - 91620 Nozay - France 1973 Email: pierre.peloso@alcatel-lucent.fr 1975 Jonathan Sadler 1976 Tellabs 1977 Email: Jonathan.Sadler@tellabs.com 1979 Dirk Schroetter 1980 Cisco 1981 Email: dschroet@cisco.com 1983 Author's Addresses 1985 Greg M. Bernstein (ed.) 1986 Grotto Networking 1987 Fremont California, USA 1988 Phone: (510) 573-2237 1989 Email: gregb@grotto-networking.com 1991 Young Lee (ed.) 1992 Huawei Technologies 1993 1700 Alma Drive, Suite 100 1994 Plano, TX 75075 1995 USA 1997 Phone: (972) 509-5599 (x2240) 1998 Email: ylee@huawei.com 2000 Wataru Imajuku 2001 NTT Network Innovation Labs 2002 1-1 Hikari-no-oka, Yokosuka, Kanagawa 2003 Japan 2005 Phone: +81-(46) 859-4315 2006 Email: imajuku.wataru@lab.ntt.co.jp 2008 Intellectual Property Statement 2010 The IETF Trust takes no position regarding the validity or scope of 2011 any Intellectual Property Rights or other rights that might be 2012 claimed to pertain to the implementation or use of the technology 2013 described in any IETF Document or the extent to which any license 2014 under such rights might or might not be available; nor does it 2015 represent that it has made any independent effort to identify any 2016 such rights. 2018 Copies of Intellectual Property disclosures made to the IETF 2019 Secretariat and any assurances of licenses to be made available, or 2020 the result of an attempt made to obtain a general license or 2021 permission for the use of such proprietary rights by implementers or 2022 users of this specification can be obtained from the IETF on-line IPR 2023 repository at http://www.ietf.org/ipr 2025 The IETF invites any interested party to bring to its attention any 2026 copyrights, patents or patent applications, or other proprietary 2027 rights that may cover technology that may be required to implement 2028 any standard or specification contained in an IETF Document. 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