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Bernstein 4 Expires: August 2014 Grotto Networking 5 D. Li 6 Huawei 7 W. Imajuku 8 NTT 10 February 13, 2014 12 Routing and Wavelength Assignment Information Model for Wavelength 13 Switched Optical Networks 15 draft-ietf-ccamp-rwa-info-21.txt 17 Status of this Memo 19 This Internet-Draft is submitted to IETF in full conformance with 20 the provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF), its areas, and its working groups. Note that 24 other groups may also distribute working documents as Internet- 25 Drafts. 27 Internet-Drafts are draft documents valid for a maximum of six 28 months and may be updated, replaced, or obsoleted by other documents 29 at any time. 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Code Components extracted from this 51 document must include Simplified BSD License text as described in 52 Section 4.e of the Trust Legal Provisions and are provided without 53 warranty as described in the Simplified BSD License. 55 Abstract 57 This document provides a model of information needed by the routing 58 and wavelength assignment (RWA) process in wavelength switched 59 optical networks (WSONs). The purpose of the information described 60 in this model is to facilitate constrained lightpath computation in 61 WSONs. This model takes into account compatibility constraints 62 between WSON signal attributes and network elements but does not 63 include constraints due to optical impairments. Aspects of this 64 information that may be of use to other technologies utilizing a 65 GMPLS control plane are discussed. 67 Table of Contents 69 1. Introduction...................................................3 70 2. Terminology....................................................3 71 3. Routing and Wavelength Assignment Information Model............4 72 3.1. Dynamic and Relatively Static Information.................4 73 4. Node Information (General).....................................4 74 4.1. Connectivity Matrix.......................................5 75 5. Node Information (WSON specific)...............................6 76 5.1. Resource Accessibility/Availability.......................7 77 5.2. Resource Signal Constraints and Processing Capabilities..11 78 5.3. Compatibility and Capability Details.....................12 79 5.3.1. Shared Input or Output Indication...................12 80 5.3.2. Optical Interface Class List........................12 81 5.3.3. Acceptable Client Signal List.......................12 82 5.3.4. Processing Capability List..........................13 83 6. Link Information (General)....................................13 84 6.1. Administrative Group.....................................14 85 6.2. Interface Switching Capability Descriptor................14 86 6.3. Link Protection Type (for this link).....................14 87 6.4. Shared Risk Link Group Information.......................14 88 6.5. Traffic Engineering Metric...............................14 89 6.6. Port Label Restrictions..................................14 90 6.6.1. Port-Wavelength Exclusivity Example.................17 91 7. Dynamic Components of the Information Model...................18 92 7.1. Dynamic Link Information (General).......................19 93 7.2. Dynamic Node Information (WSON Specific).................19 94 8. Security Considerations.......................................19 95 9. IANA Considerations...........................................20 96 10. Acknowledgments..............................................20 97 11. References...................................................21 98 11.1. Normative References....................................21 99 11.2. Informative References..................................22 100 12. Contributors.................................................23 101 Author's Addresses...............................................24 102 Intellectual Property Statement..................................24 103 Disclaimer of Validity...........................................25 105 1. Introduction 107 The purpose of the following information model for WSONs is to 108 facilitate constrained lightpath computation and as such is not a 109 general purpose network management information model. This 110 constraint is frequently referred to as the "wavelength continuity" 111 constraint, and the corresponding constrained lightpath computation 112 is known as the routing and wavelength assignment (RWA) problem. 113 Hence the information model must provide sufficient topology and 114 wavelength restriction and availability information to support this 115 computation. More details on the RWA process and WSON subsystems and 116 their properties can be found in [RFC6163]. The model defined here 117 includes constraints between WSON signal attributes and network 118 elements, but does not include optical impairments. 120 In addition to presenting an information model suitable for path 121 computation in WSON, this document also highlights model aspects 122 that may have general applicability to other technologies utilizing 123 a GMPLS control plane. The portion of the information model 124 applicable to other technologies beyond WSON is referred to as 125 "general" to distinguish it from the "WSON-specific" portion that is 126 applicable only to WSON technology. 128 2. Terminology 130 Refer to [RFC6163] for ROADM, RWA, Wavelength Conversion, WDM and 131 WSON. 133 3. Routing and Wavelength Assignment Information Model 135 The following WSON RWA information model is grouped into four 136 categories regardless of whether they stem from a switching 137 subsystem or from a line subsystem: 139 o Node Information 141 o Link Information 143 o Dynamic Node Information 145 o Dynamic Link Information 147 Note that this is roughly the categorization used in [G.7715] 148 section 7. 150 In the following, where applicable, the reduced Backus-Naur form 151 (RBNF) syntax of [RBNF] is used to aid in defining the RWA 152 information model. 154 3.1. Dynamic and Relatively Static Information 156 All the RWA information of concern in a WSON network is subject to 157 change over time. Equipment can be upgraded; links may be placed in 158 or out of service and the like. However, from the point of view of 159 RWA computations there is a difference between information that can 160 change with each successive connection establishment in the network 161 and that information that is relatively static and independent of 162 connection establishment. A key example of the former is link 163 wavelength usage since this can change with connection 164 setup/teardown and this information is a key input to the RWA 165 process. Examples of relatively static information are the 166 potential port connectivity of a WDM ROADM, and the channel spacing 167 on a WDM link. 169 This document separates, where possible, dynamic and static 170 information so that these can be kept separate in possible encodings 171 and hence allowing for separate updates of these two types of 172 information thereby reducing processing and traffic load caused by 173 the timely distribution of the more dynamic RWA WSON information. 175 4. Node Information (General) 177 The node information described here contains the relatively static 178 information related to a WSON node. This includes connectivity 179 constraints amongst ports and wavelengths since WSON switches can 180 exhibit asymmetric switching properties. Additional information 181 could include properties of wavelength converters in the node if any 182 are present. In [Switch] it was shown that the wavelength 183 connectivity constraints for a large class of practical WSON devices 184 can be modeled via switched and fixed connectivity matrices along 185 with corresponding switched and fixed port constraints. These 186 connectivity matrices are included with the node information while 187 the switched and fixed port wavelength constraints are included with 188 the link information. 190 Formally, 192 ::= [...] 194 Where the Node_ID would be an appropriate identifier for the node 195 within the WSON RWA context. 197 Note that multiple connectivity matrices are allowed and hence can 198 fully support the most general cases enumerated in [Switch]. 200 4.1. Connectivity Matrix 202 The connectivity matrix (ConnectivityMatrix) represents either the 203 potential connectivity matrix for asymmetric switches (e.g. ROADMs 204 and such) or fixed connectivity for an asymmetric device such as a 205 multiplexer. Note that this matrix does not represent any particular 206 internal blocking behavior but indicates which input ports and 207 wavelengths could possibly be connected to a particular output port. 208 Representing internal state dependent blocking for a switch or ROADM 209 is beyond the scope of this document and due to its highly 210 implementation dependent nature would most likely not be subject to 211 standardization in the future. The connectivity matrix is a 212 conceptual M by N matrix representing the potential switched or 213 fixed connectivity, where M represents the number of input ports and 214 N the number of output ports. This is a "conceptual" matrix since 215 the matrix tends to exhibit structure that allows for very compact 216 representations that are useful for both transmission and path 217 computation. 219 Note that the connectivity matrix information element can be useful 220 in any technology context where asymmetric switches are utilized. 222 ::= 224 Where 225 is a unique identifier for the matrix. 227 can be either 0 or 1 depending upon whether the 228 connectivity is either fixed or switched. 230 represents the fixed or switched connectivity in that 231 Matrix(i, j) = 0 or 1 depending on whether input port i can connect 232 to output port j for one or more wavelengths. 234 5. Node Information (WSON specific) 236 As discussed in [RFC6163] a WSON node may contain electro-optical 237 subsystems such as regenerators, wavelength converters or entire 238 switching subsystems. The model present here can be used in 239 characterizing the accessibility and availability of limited 240 resources such as regenerators or wavelength converters as well as 241 WSON signal attribute constraints of electro-optical subsystems. As 242 such this information element is fairly specific to WSON 243 technologies. 245 A WSON node may include regenerators or wavelength converters 246 arranged in a shared pool. As discussed in [RFC6163] this can 247 include OEO based WDM switches as well. There are a number of 248 different approaches used in the design of WDM switches containing 249 regenerator or converter pools. However, from the point of view of 250 path computation the following need to be known: 252 1. The nodes that support regeneration or wavelength conversion. 254 2. The accessibility and availability of a wavelength converter to 255 convert from a given input wavelength on a particular input port 256 to a desired output wavelength on a particular output port. 258 3. Limitations on the types of signals that can be converted and the 259 conversions that can be performed. 261 Since resources tend to be packaged together in blocks of similar 262 devices, e.g., on line cards or other types of modules, the 263 fundamental unit of identifiable resource in this document is the 264 "resource block". A resource block may contain one or more 265 resources. A resource is the smallest identifiable unit of 266 processing allocation. One can group together resources into blocks 267 if they have similar characteristics relevant to the optical system 268 being modeled, e.g., processing properties, accessibility, etc. 270 This leads to the following formal high level model: 272 ::= [...] 273 [] 275 Where 277 ::= ... 278 [...] [...] 279 [] 281 First the accessibility of resource blocks is addressed then their 282 properties are discussed. 284 5.1. Resource Accessibility/Availability 286 A similar technique as used to model ROADMs and optical switches can 287 be used to model regenerator/converter accessibility. This technique 288 was generally discussed in [RFC6163] and consisted of a matrix to 289 indicate possible connectivity along with wavelength constraints for 290 links/ports. Since regenerators or wavelength converters may be 291 considered a scarce resource it is desirable that the model include, 292 if desired, the usage state (availability) of individual 293 regenerators or converters in the pool. Models that incorporate more 294 state to further reveal blocking conditions on input or output to 295 particular converters are for further study and not included here. 297 The three stage model is shown schematically in Figure 1 and Figure 298 2. The difference between the two figures is that Figure 1 assumes 299 that each signal that can get to a resource block may do so, while 300 in Figure 2 the access to sets of resource blocks is via a shared 301 fiber which imposes its own wavelength collision constraint. The 302 representation of Figure 1 can have more than one input to each 303 resource block since each input represents a single wavelength 304 signal, while in Figure 2 shows a single multiplexed WDM input or 305 output, e.g., a fiber, to/from each set of block. 307 This model assumes N input ports (fibers), P resource blocks 308 containing one or more identical resources (e.g. wavelength 309 converters), and M output ports (fibers). Since not all input ports 310 can necessarily reach each resource block, the model starts with a 311 resource pool input matrix RI(i,p) = {0,1} whether input port i can 312 reach potentially reach resource block p. 314 Since not all wavelengths can necessarily reach all the resources or 315 the resources may have limited input wavelength range the model has 316 a set of relatively static input port constraints for each resource. 317 In addition, if the access to a set of resource blocks is via a 318 shared fiber (Figure 2) this would impose a dynamic wavelength 319 availability constraint on that shared fiber. The resource block 320 input port constraint is modeled via a static wavelength set 321 mechanism and the case of shared access to a set of blocks is 322 modeled via a dynamic wavelength set mechanism. 324 Next a state vector RA(j) = {0,...,k} is used to track the number of 325 resources in resource block j in use. This is the only state kept in 326 the resource pool model. This state is not necessary for modeling 327 "fixed" transponder system or full OEO switches with WDM interfaces, 328 i.e., systems where there is no sharing. 330 After that, a set of static resource output wavelength constraints 331 and possibly dynamic shared output fiber constraints maybe used. The 332 static constraints indicate what wavelengths a particular resource 333 block can generate or are restricted to generating e.g., a fixed 334 regenerator would be limited to a single lambda. The dynamic 335 constraints would be used in the case where a single shared fiber is 336 used to output the resource block (Figure 2). 338 Finally, to complete the model, a resource pool output matrix 339 RE(p,k) = {0,1} depending on whether the output from resource block 340 p can reach output port k, may be used. 342 I1 +-------------+ +-------------+ O1 343 ----->| | +--------+ | |-----> 344 I2 | +------+ Rb #1 +-------+ | O2 345 ----->| | +--------+ | |-----> 346 | | | | 347 | Resource | +--------+ | Resource | 348 | Pool +------+ +-------+ Pool | 349 | | + Rb #2 + | | 350 | Input +------+ +-------| Output | 351 | Connection | +--------+ | Connection | 352 | Matrix | . | Matrix | 353 | | . | | 354 | | . | | 355 IN | | +--------+ | | OM 356 ----->| +------+ Rb #P +-------+ |-----> 357 | | +--------+ | | 358 +-------------+ ^ ^ +-------------+ 359 | | 360 | | 361 | | 362 | | 364 Input wavelength Output wavelength 365 constraints for constraints for 366 each resource each resource 368 Figure 1 Schematic diagram of resource pool model. 370 I1 +-------------+ +-------------+ O1 371 ----->| | +--------+ | |-----> 372 I2 | +======+ Rb #1 +-+ + | O2 373 ----->| | +--------+ | | |-----> 374 | | |=====| | 375 | Resource | +--------+ | | Resource | 376 | Pool | +-+ Rb #2 +-+ | Pool | 377 | | | +--------+ + | 378 | Input |====| | Output | 379 | Connection | | +--------+ | Connection | 380 | Matrix | +-| Rb #3 |=======| Matrix | 381 | | +--------+ | | 382 | | . | | 383 | | . | | 384 | | . | | 385 IN | | +--------+ | | OM 386 ----->| +======+ Rb #P +=======+ |-----> 387 | | +--------+ | | 388 +-------------+ ^ ^ +-------------+ 389 | | 390 | | 391 | | 392 Single (shared) fibers for block input and output 394 Input wavelength Output wavelength 395 availability for availability for 396 each block input fiber each block output fiber 398 Figure 2 Schematic diagram of resource pool model with shared block 399 accessibility. 401 Formally the model can be specified as: 403 405 ::= 406 408 ::= [] 409 [] 410 ::= 411 [] [] 413 Note that except for all the other components of 414 are relatively static. Also the 415 and are only used 416 in the cases of shared input or output access to the particular 417 block. See the resource block information in the next section to see 418 how this is specified. 420 5.2. Resource Signal Constraints and Processing Capabilities 422 The wavelength conversion abilities of a resource (e.g. regenerator, 423 wavelength converter) were modeled in the 424 previously discussed. As discussed in [RFC6163] the constraints on 425 an electro-optical resource can be modeled in terms of input 426 constraints, processing capabilities, and output constraints: 428 ::= [] 429 [] [] 431 Where is a list of resource block identifiers 432 with the same characteristics. If this set is missing the 433 constraints are applied to the entire network element. 435 The are signal compatibility based constraints 436 and/or shared access constraint indication. The details of these 437 constraints are defined in section 5.3. 439 ::= [] 440 [] 442 The are important operations that the 443 resource (or network element) can perform on the signal. The details 444 of these capabilities are defined in section 5.3. 446 ::= [] 447 [] [] [] 449 The are either restrictions on the properties of 450 the signal leaving the block, options concerning the signal 451 properties when leaving the resource or shared fiber output 452 constraint indication. 454 := 455 [][] 457 5.3. Compatibility and Capability Details 459 5.3.1. Shared Input or Output Indication 461 As discussed in the previous section and shown in Figure 2 the input 462 or output access to a resource block may be via a shared fiber. The 463 and elements are indicators for this 464 condition with respect to the block being described. 466 5.3.2. Optical Interface Class List 468 ::= ... 470 The Optical Interface Class is a unique number that identifies 471 all information related to optical characteristics of a physical 472 interface. The class may include other optical parameters 473 related to other interface properties. A class always includes 474 signal compatibility information. 476 The content of each class is out of the scope of this draft and 477 can be defined by other entities (e.g. ITU, optical equipment 478 vendors, etc.). 480 Since even current implementation of physical interfaces may 481 support different optical characteristics, a single interface may 482 support multiple interface classes. Which optical interface 483 class is used among all the ones available for an interface is 484 out of the scope of this draft but is an output of the RWA 485 process. 487 5.3.3. Acceptable Client Signal List 489 The list is simply: 491 < ClientSignalList>::=[]... 493 Where the Generalized Protocol Identifiers (G-PID) object 494 represents one of the IETF standardized G-PID values as defined 495 in [RFC3471] and [RFC4328]. 497 5.3.4. Processing Capability List 499 The ProcessingCapabilities were defined in Section 5.2. 501 The processing capability list sub-TLV is a list of processing 502 functions that the WSON network element (NE) can perform on the 503 signal including: 505 1. Number of Resources within the block 507 2. Regeneration capability 509 3. Fault and performance monitoring 511 4. Vendor Specific capability 513 Note that the code points for Fault and performance monitoring and 514 vendor specific capability are subject to further study. 516 6. Link Information (General) 518 MPLS-TE routing protocol extensions for OSPF and IS-IS [RFC3630], 519 [RFC5305] along with GMPLS routing protocol extensions for OSPF and 520 IS-IS [RFC4203, RFC5307] provide the bulk of the relatively static 521 link information needed by the RWA process. However, WSON networks 522 bring in additional link related constraints. These stem from WDM 523 line system characterization, laser transmitter tuning restrictions, 524 and switching subsystem port wavelength constraints, e.g., colored 525 ROADM drop ports. 527 In the following summarize both information from existing GMPLS 528 route protocols and new information that maybe needed by the RWA 529 process. 531 ::= [] 532 [] [] [...] 533 [] [...] 535 Note that these additional link characteristics only applies to line 536 side ports of WDM system or add/drop ports pertaining to Resource 537 Pool (e.g., Regenerator or Wavelength Converter Pool). The 538 advertisement of input/output tributary ports is not intended here. 540 6.1. Administrative Group 542 AdministrativeGroup: Defined in [RFC3630]. Each set bit corresponds 543 to one administrative group assigned to the interface. A link may 544 belong to multiple groups. This is a configured quantity and can be 545 used to influence routing decisions. 547 6.2. Interface Switching Capability Descriptor 549 InterfaceSwCapDesc: Defined in [RFC4202], lets us know the different 550 switching capabilities on this GMPLS interface. In both [RFC4203] 551 and [RFC5307] this information gets combined with the maximum LSP 552 bandwidth that can be used on this link at eight different priority 553 levels. 555 6.3. Link Protection Type (for this link) 557 Protection: Defined in [RFC4202] and implemented in [RFC4203, 558 RFC5307]. Used to indicate what protection, if any, is guarding this 559 link. 561 6.4. Shared Risk Link Group Information 563 SRLG: Defined in [RFC4202] and implemented in [RFC4203, RFC5307]. 564 This allows for the grouping of links into shared risk groups, i.e., 565 those links that are likely, for some reason, to fail at the same 566 time. 568 6.5. Traffic Engineering Metric 570 TrafficEngineeringMetric: Defined in [RFC3630]. This allows for the 571 identification of a data channel link metric value for traffic 572 engineering that is separate from the metric used for path cost 573 computation of the control plane. 575 Note that multiple "link metric values" could find use in optical 576 networks, however it would be more useful to the RWA process to 577 assign these specific meanings such as link mile metric, or 578 probability of failure metric, etc... 580 6.6. Port Label Restrictions 582 Port label restrictions could be applied generally to any label 583 types in GMPLS by adding new kinds of restrictions. Wavelength is a 584 type of label. 586 Port label (wavelength) restrictions (PortLabelRestriction) model 587 the label (wavelength) restrictions that the link and various 588 optical devices such as OXCs, ROADMs, and waveband multiplexers may 589 impose on a port. These restrictions tell us what wavelength may or 590 may not be used on a link and are relatively static. This plays an 591 important role in fully characterizing a WSON switching device 592 [Switch]. Port wavelength restrictions are specified relative to the 593 port in general or to a specific connectivity matrix (section 4.1. 594 Reference [Switch] gives an example where both switch and fixed 595 connectivity matrices are used and both types of constraints occur 596 on the same port. 598 ::= 599 601 ::= 602 | 603 | 604