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Imajuku 8 NTT 10 December 4, 2014 12 Routing and Wavelength Assignment Information Model for Wavelength 13 Switched Optical Networks 15 draft-ietf-ccamp-rwa-info-24.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).....................................5 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........................13 81 5.3.3. Acceptable Client Signal List.......................13 82 5.3.4. Processing Capability List..........................13 83 6. Link Information (General)....................................14 84 6.1. Administrative Group.....................................14 85 6.2. Interface Switching Capability Descriptor................15 86 6.3. Link Protection Type (for this link).....................15 87 6.4. Shared Risk Link Group Information.......................15 88 6.5. Traffic Engineering Metric...............................15 89 6.6. Port Label Restrictions..................................15 90 6.6.1. Port-Wavelength Exclusivity Example.................18 91 7. Dynamic Components of the Information Model...................19 92 7.1. Dynamic Link Information (General).......................20 93 7.2. Dynamic Node Information (WSON Specific).................20 94 8. Security Considerations.......................................20 95 9. IANA Considerations...........................................21 96 10. Acknowledgments..............................................21 97 11. References...................................................22 98 11.1. Normative References....................................22 99 11.2. Informative References..................................23 100 12. Contributors.................................................24 101 Authors' Addresses...............................................25 102 Intellectual Property Statement..................................25 103 Disclaimer of Validity...........................................26 105 1. Introduction 107 The purpose of the WSONs information model described in this 108 document is to facilitate constrained lightpath computation and as 109 such is not a general purpose network management information model. 110 This constraint is frequently referred to as the "wavelength 111 continuity" constraint, and the corresponding constrained lightpath 112 computation is known as the routing and wavelength assignment (RWA) 113 problem. Hence the information model must provide sufficient 114 topology and wavelength restriction and availability information to 115 support this computation. More details on the RWA process and WSON 116 subsystems and their properties can be found in [RFC6163]. The model 117 defined here includes constraints between WSON signal attributes and 118 network 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 Reconfigurable Optical Add/Drop Multiplexer 131 (ROADM), RWA, Wavelength Conversion, Wavelength Division 132 Multiplexing (WDM) and WSON. 134 3. Routing and Wavelength Assignment Information Model 136 The WSON RWA information model in this document comprises four 137 categories of information. The categories are independent of whether 138 the information comes from a switching subsystem or from a line 139 subsystem -- a switching subsystem refers to WSON nodes such as 140 ROADM or Optical Add/Drop Multiplexer (OADM), and a line subsystem 141 refers to devices such as WDM or Optical Amplifier. The categories 142 are these: 144 o Node Information 146 o Link Information 148 o Dynamic Node Information 150 o Dynamic Link Information 152 Note that this is roughly the categorization used in [G.7715] 153 section 7. 155 In the following, where applicable, the reduced Backus-Naur form 156 (RBNF) syntax of [RBNF] is used to aid in defining the RWA 157 information model. 159 3.1. Dynamic and Relatively Static Information 161 All the RWA information of concern in a WSON network is subject to 162 change over time. Equipment can be upgraded; links may be placed in 163 or out of service and the like. However, from the point of view of 164 RWA computations there is a difference between information that can 165 change with each successive connection establishment in the network 166 and that information that is relatively static and independent of 167 connection establishment. A key example of the former is link 168 wavelength usage since this can change with connection 169 setup/teardown and this information is a key input to the RWA 170 process. Examples of relatively static information are the 171 potential port connectivity of a WDM ROADM, and the channel spacing 172 on a WDM link. 174 This document separates, where possible, dynamic and static 175 information so that these can be kept separate in possible encodings 176 and hence allowing for separate updates of these two types of 177 information thereby reducing processing and traffic load caused by 178 the timely distribution of the more dynamic RWA WSON information. 180 4. Node Information (General) 182 The node information described here contains the relatively static 183 information related to a WSON node. This includes connectivity 184 constraints amongst ports and wavelengths since WSON switches can 185 exhibit asymmetric switching properties. Additional information 186 could include properties of wavelength converters in the node if any 187 are present. In [Switch] it was shown that the wavelength 188 connectivity constraints for a large class of practical WSON devices 189 can be modeled via switched and fixed connectivity matrices along 190 with corresponding switched and fixed port constraints. These 191 connectivity matrices are included with the node information while 192 the switched and fixed port wavelength constraints are included with 193 the link information. 195 Formally, 197 ::= [...] 199 Where the Node_ID would be an appropriate identifier for the node 200 within the WSON RWA context. 202 Note that multiple connectivity matrices are allowed and hence can 203 fully support the most general cases enumerated in [Switch]. 205 4.1. Connectivity Matrix 207 The connectivity matrix (ConnectivityMatrix) represents either the 208 potential connectivity matrix for asymmetric switches (e.g. ROADMs 209 and such) or fixed connectivity for an asymmetric device such as a 210 multiplexer. Note that this matrix does not represent any particular 211 internal blocking behavior but indicates which input ports and 212 wavelengths could possibly be connected to a particular output port. 213 Representing internal state dependent blocking for a switch or ROADM 214 is beyond the scope of this document and due to its highly 215 implementation dependent nature would most likely not be subject to 216 standardization in the future. The connectivity matrix is a 217 conceptual M by N matrix representing the potential switched or 218 fixed connectivity, where M represents the number of input ports and 219 N the number of output ports. This is a "conceptual" matrix since 220 the matrix tends to exhibit structure that allows for very compact 221 representations that are useful for both transmission and path 222 computation. 224 Note that the connectivity matrix information element can be useful 225 in any technology context where asymmetric switches are utilized. 227 ::= 229 231 233 Where 235 is a unique identifier for the matrix. 237 can be either 0 or 1 depending upon whether the 238 connectivity is either fixed or switched. 240 represents the fixed or switched connectivity in that 241 Matrix(i, j) = 0 or 1 depending on whether input port i can connect 242 to output port j for one or more wavelengths. 244 5. Node Information (WSON specific) 246 As discussed in [RFC6163] a WSON node may contain electro-optical 247 subsystems such as regenerators, wavelength converters or entire 248 switching subsystems. The model present here can be used in 249 characterizing the accessibility and availability of limited 250 resources such as regenerators or wavelength converters as well as 251 WSON signal attribute constraints of electro-optical subsystems. As 252 such this information element is fairly specific to WSON 253 technologies. 255 A WSON node may include regenerators or wavelength converters 256 arranged in a shared pool. As discussed in [RFC6163] this can 257 include OEO based WDM switches as well. There are a number of 258 different approaches used in the design of WDM switches containing 259 regenerator or converter pools. However, from the point of view of 260 path computation the following need to be known: 262 1. The nodes that support regeneration or wavelength conversion. 264 2. The accessibility and availability of a wavelength converter to 265 convert from a given input wavelength on a particular input port 266 to a desired output wavelength on a particular output port. 268 3. Limitations on the types of signals that can be converted and the 269 conversions that can be performed. 271 Since resources tend to be packaged together in blocks of similar 272 devices, e.g., on line cards or other types of modules, the 273 fundamental unit of identifiable resource in this document is the 274 "resource block". A resource block may contain one or more 275 resources. A resource is the smallest identifiable unit of 276 processing allocation. One can group together resources into blocks 277 if they have similar characteristics relevant to the optical system 278 being modeled, e.g., processing properties, accessibility, etc. 280 This leads to the following formal high level model: 282 ::= 284 [...] 286 [] 288 Where 290 ::= ... 292 [...] 294 [...] 296 [] 298 First the accessibility of resource blocks is addressed then their 299 properties are discussed. 301 5.1. Resource Accessibility/Availability 303 A similar technique as used to model ROADMs and optical switches can 304 be used to model regenerator/converter accessibility. This technique 305 was generally discussed in [RFC6163] and consisted of a matrix to 306 indicate possible connectivity along with wavelength constraints for 307 links/ports. Since regenerators or wavelength converters may be 308 considered a scarce resource it is desirable that the model include, 309 if desired, the usage state (availability) of individual 310 regenerators or converters in the pool. Models that incorporate more 311 state to further reveal blocking conditions on input or output to 312 particular converters are for further study and not included here. 314 The three stage model is shown schematically in Figure 1 and Figure 315 2. The difference between the two figures is that Figure 1 assumes 316 that each signal that can get to a resource block may do so, while 317 in Figure 2 the access to sets of resource blocks is via a shared 318 fiber which imposes its own wavelength collision constraint. The 319 representation of Figure 1 can have more than one input to each 320 resource block since each input represents a single wavelength 321 signal, while in Figure 2 shows a single multiplexed WDM input or 322 output, e.g., a fiber, to/from each set of block. 324 This model assumes N input ports (fibers), P resource blocks 325 containing one or more identical resources (e.g. wavelength 326 converters), and M output ports (fibers). Since not all input ports 327 can necessarily reach each resource block, the model starts with a 328 resource pool input matrix RI(i,p) = {0,1} whether input port i can 329 potentially reach resource block p. 331 Since not all wavelengths can necessarily reach all the resources or 332 the resources may have limited input wavelength range the model has 333 a set of relatively static input port constraints for each resource. 334 In addition, if the access to a set of resource blocks is via a 335 shared fiber (Figure 2) this would impose a dynamic wavelength 336 availability constraint on that shared fiber. The resource block 337 input port constraint is modeled via a static wavelength set 338 mechanism and the case of shared access to a set of blocks is 339 modeled via a dynamic wavelength set mechanism. 341 Next a state vector RA(j) = {0,...,k} is used to track the number of 342 resources in resource block j in use. This is the only state kept in 343 the resource pool model. This state is not necessary for modeling 344 "fixed" transponder system or full OEO switches with WDM interfaces, 345 i.e., systems where there is no sharing. 347 After that, a set of static resource output wavelength constraints 348 and possibly dynamic shared output fiber constraints maybe used. The 349 static constraints indicate what wavelengths a particular resource 350 block can generate or are restricted to generating e.g., a fixed 351 regenerator would be limited to a single lambda. The dynamic 352 constraints would be used in the case where a single shared fiber is 353 used to output the resource block (Figure 2). 355 Finally, to complete the model, a resource pool output matrix 356 RE(p,k) = {0,1} depending on whether the output from resource block 357 p can reach output port k, may be used. 359 I1 +-------------+ +-------------+ O1 360 ----->| | +--------+ | |-----> 361 I2 | +------+ Rb #1 +-------+ | O2 362 ----->| | +--------+ | |-----> 363 | | | | 364 | Resource | +--------+ | Resource | 365 | Pool +------+ +-------+ Pool | 366 | | + Rb #2 + | | 367 | Input +------+ +-------| Output | 368 | Connection | +--------+ | Connection | 369 | Matrix | . | Matrix | 370 | | . | | 371 | | . | | 372 IN | | +--------+ | | OM 373 ----->| +------+ Rb #P +-------+ |-----> 374 | | +--------+ | | 375 +-------------+ ^ ^ +-------------+ 376 | | 377 | | 378 | | 379 | | 381 Input wavelength Output wavelength 382 constraints for constraints for 383 each resource each resource 385 Note: Rb is a Resource Block. 387 Figure 1 Schematic diagram of resource pool model. 389 I1 +-------------+ +-------------+ O1 390 ----->| | +--------+ | |-----> 391 I2 | +======+ Rb #1 +-+ | | O2 392 ----->| | +--------+ | | |-----> 393 | | |=====| | 394 | Resource | +--------+ | | Resource | 395 | Pool | +-+ Rb #2 +-+ | Pool | 396 | | | +--------+ | | 397 | Input |====| | Output | 398 | Connection | | +--------+ | Connection | 399 | Matrix | +-| Rb #3 |=======| Matrix | 400 | | +--------+ | | 401 | | . | | 402 | | . | | 403 | | . | | 404 IN | | +--------+ | | OM 405 ----->| +======+ Rb #P +=======+ |-----> 406 | | +--------+ | | 407 +-------------+ ^ ^ +-------------+ 408 | | 409 | | 410 | | 411 Single (shared) fibers for block input and output 413 Input wavelength Output wavelength 414 availability for availability for 415 each block input fiber each block output fiber 417 Note: Rb is a Resource Block. 419 Figure 2 Schematic diagram of resource pool model with shared block 420 accessibility. 422 Formally the model can be specified as: 424 ::= 426 428 ::= 430 432 ::= [] 434 [] 436 ::= 438 440 [] 442 [] 444 Note that except for all the other components of 445 are relatively static. Also the 446 and are only used 447 in the cases of shared input or output access to the particular 448 block. See the resource block information in the next section to see 449 how this is specified. 451 5.2. Resource Signal Constraints and Processing Capabilities 453 The wavelength conversion abilities of a resource (e.g. regenerator, 454 wavelength converter) were modeled in the 455 previously discussed. As discussed in [RFC6163] the constraints on 456 an electro-optical resource can be modeled in terms of input 457 constraints, processing capabilities, and output constraints: 459 ::= 461 [] 463 [] 465 [] 467 Where is a list of resource block identifiers 468 with the same characteristics. If this set is missing the 469 constraints are applied to the entire network element. 471 The are signal compatibility based constraints 472 and/or shared access constraint indication. The details of these 473 constraints are defined in section 5.3. 475 ::= 477 [] 479 [] 481 The are important operations that the 482 resource (or network element) can perform on the signal. The details 483 of these capabilities are defined in section 5.3. 485 ::= [] 487 [] 489 [] 491 [] 493 The are either restrictions on the properties of 494 the signal leaving the block, options concerning the signal 495 properties when leaving the resource or shared fiber output 496 constraint indication. 498 := 500 [] 502 [] 504 5.3. Compatibility and Capability Details 506 5.3.1. Shared Input or Output Indication 508 As discussed in the previous section and shown in Figure 2 the input 509 or output access to a resource block may be via a shared fiber. The 510 and elements are indicators for this 511 condition with respect to the block being described. 513 5.3.2. Optical Interface Class List 515 ::= ... 517 The Optical Interface Class is a unique number that identifies 518 all information related to optical characteristics of a physical 519 interface. The class may include other optical parameters 520 related to other interface properties. A class always includes 521 signal compatibility information. 523 The content of each class is out of the scope of this document 524 and can be defined by other entities (e.g. ITU, optical 525 equipment vendors, etc.). 527 Since even current implementation of physical interfaces may 528 support different optical characteristics, a single interface may 529 support multiple interface classes. Which optical interface 530 class is used among all the ones available for an interface is 531 out of the scope of this document but is an output of the RWA 532 process. 534 5.3.3. Acceptable Client Signal List 536 The list is simply: 538 ::=[]... 540 Where the Generalized Protocol Identifiers (G-PID) object 541 represents one of the IETF standardized G-PID values as defined 542 in [RFC3471] and [RFC4328]. 544 5.3.4. Processing Capability List 546 The ProcessingCapabilities were defined in Section 5.2. 548 The processing capability list sub-TLV is a list of processing 549 functions that the WSON network element (NE) can perform on the 550 signal including: 552 1. Number of Resources within the block 554 2. Regeneration capability 556 3. Fault and performance monitoring 558 4. Vendor Specific capability 560 Note that the code points for Fault and performance monitoring and 561 vendor specific capability are subject to further study. 563 6. Link Information (General) 565 MPLS-TE routing protocol extensions for OSPF and IS-IS [RFC3630], 566 [RFC5305] along with GMPLS routing protocol extensions for OSPF and 567 IS-IS [RFC4203, RFC5307] provide the bulk of the relatively static 568 link information needed by the RWA process. However, WSON networks 569 bring in additional link related constraints. These stem from WDM 570 line system characterization, laser transmitter tuning restrictions, 571 and switching subsystem port wavelength constraints, e.g., colored 572 ROADM drop ports. 574 In the following summarize both information from existing GMPLS 575 route protocols and new information that maybe needed by the RWA 576 process. 578 ::= 580 [] 582 [] 584 [] 586 [...] 588 [] 590 [...] 592 Note that these additional link characteristics only applies to line 593 side ports of WDM system or add/drop ports pertaining to Resource 594 Pool (e.g., Regenerator or Wavelength Converter Pool). The 595 advertisement of input/output tributary ports is not intended here. 597 6.1. Administrative Group 599 Administrative Group: Defined in [RFC3630] and extended for MPLS-TE 600 [RFC7308]. Each set bit corresponds to one administrative group 601 assigned to the interface. A link may belong to multiple groups. 602 This is a configured quantity and can be used to influence routing 603 decisions. 605 6.2. Interface Switching Capability Descriptor 607 InterfaceSwCapDesc: Defined in [RFC4202], lets us know the different 608 switching capabilities on this GMPLS interface. In both [RFC4203] 609 and [RFC5307] this information gets combined with the maximum LSP 610 bandwidth that can be used on this link at eight different priority 611 levels. 613 6.3. Link Protection Type (for this link) 615 Protection: Defined in [RFC4202] and implemented in [RFC4203, 616 RFC5307]. Used to indicate what protection, if any, is guarding this 617 link. 619 6.4. Shared Risk Link Group Information 621 SRLG: Defined in [RFC4202] and implemented in [RFC4203, RFC5307]. 622 This allows for the grouping of links into shared risk groups, i.e., 623 those links that are likely, for some reason, to fail at the same 624 time. 626 6.5. Traffic Engineering Metric 628 TrafficEngineeringMetric: Defined in [RFC3630] and [RFC5305]. This 629 allows for the identification of a data channel link metric value 630 for traffic engineering that is separate from the metric used for 631 path cost computation of the control plane. 633 Note that multiple "link metric values" could find use in optical 634 networks, however it would be more useful to the RWA process to 635 assign these specific meanings such as link mile metric, or 636 probability of failure metric, etc... 638 6.6. Port Label Restrictions 640 Port label restrictions could be applied generally to any label 641 types in GMPLS by adding new kinds of restrictions. Wavelength is a 642 type of label. 644 Port label (wavelength) restrictions (PortLabelRestriction) model 645 the label (wavelength) restrictions that the link and various 646 optical devices such as OXCs, ROADMs, and waveband multiplexers may 647 impose on a port. These restrictions tell us what wavelength may or 648 may not be used on a link and are relatively static. This plays an 649 important role in fully characterizing a WSON switching device 650 [Switch]. Port wavelength restrictions are specified relative to the 651 port in general or to a specific connectivity matrix (section 4.1. 652 Reference [Switch] gives an example where both switch and fixed 653 connectivity matrices are used and both types of constraints occur 654 on the same port. 656 ::= 658 660 662 ::= 664 | 666 | 668