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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Possible downref: Non-RFC (?) normative reference: ref. 'G.694.1' -- Obsolete informational reference (is this intentional?): RFC 6982 (Obsoleted by RFC 7942) Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Farrel 3 Internet Draft D. King 4 Updates: 3471, 6205 (if approved) Old Dog Consulting 5 Intended Status: Standards Track Y. Li 6 Expires: 21 May 2014 Nanjing University 7 F. Zhang 8 Huawei Technologies 10 21 November 2014 12 Generalized Labels for the Flexi-Grid in 13 Lambda Switch Capable (LSC) Label Switching Routers 15 draft-ietf-ccamp-flexigrid-lambda-label-02.txt 17 Abstract 19 GMPLS supports the description of optical switching by identifying 20 entries in fixed lists of switchable wavelengths (called grids) 21 through the encoding of lambda labels. Work within the ITU-T Study 22 Group 15 has defined a finer granularity grid, and the facility to 23 flexibly select different widths of spectrum from the grid. This 24 document defines a new GMPLS lambda label format to support this 25 flexi-grid. 27 This document updates RFC 3471 and RFC 6205 by introducing a new 28 label format. 30 Status of this Memo 32 This Internet-Draft is submitted to IETF in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF), its areas, and its working groups. Note that other 37 groups may also distribute working documents as Internet-Drafts. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 The list of current Internet-Drafts can be accessed at 45 http://www.ietf.org/ietf/1id-abstracts.txt 47 The list of Internet-Draft Shadow Directories can be accessed at 48 http://www.ietf.org/shadow.html 50 Copyright Notice 52 Copyright (c) 2014 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 68 1.1. Conventions Used in This Document . . . . . . . . . . . . . 3 69 2. Overview of Flexi-Grid . . . . . . . . . . . . . . . . . . . . 3 70 2.1. Composite Labels . . . . . . . . . . . . . . . . . . . . . . 4 71 3. Fixed Grid Lambda Label Encoding . . . . . . . . . . . . . . . 4 72 4. Flexi-Grid Label Format and Values . . . . . . . . . . . . . . 5 73 4.1 Flexi-Grid Label Encoding . . . . . . . . . . . . . . . . . . 5 74 4.2. Considerations of Bandwidth . . . . . . . . . . . . . . . . 6 75 4.3. Composite Labels . . . . . . . . . . . . . . . . . . . . . . 7 76 5. Manageability Considerations . . . . . . . . . . . . . . . . . 8 77 6. Implementation Status . . . . . . . . . . . . . . . . . . . . 9 78 6.1. Centre Tecnologic de Telecomunicacions de Catalunya (CTTC) . 9 79 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 80 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 81 8.1. Grid Subregistry . . . . . . . . . . . . . . . . . . . . . . 10 82 8.2. DWDM Channel Spacing Subregistry . . . . . . . . . . . . . . 11 83 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 84 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 85 10.1. Normative References . . . . . . . . . . . . . . . . . . . 11 86 10.2. Informative References . . . . . . . . . . . . . . . . . . 12 87 Appendix A. Flexi-Grid Example . . . . . . . . . . . . . . . . . 13 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 89 Contributors' Addresses . . . . . . . . . . . . . . . . . . . . . 14 91 1. Introduction 93 As described in [RFC3945], GMPLS extends MPLS from supporting only 94 Packet Switching Capable (PSC) interfaces and switching, to also 95 support four new classes of interfaces and switching that include 96 Lambda Switch Capable (LSC). 98 A functional description of the extensions to MPLS signaling needed 99 to support this new class of interface and switching is provided in 100 [RFC3471]. 102 Section 3.2.1.1 of [RFC3471] states that wavelength labels "only have 103 significance between two neighbors": global wavelength semantics are 104 not considered. [RFC6205] defines a standard lambda label format 105 that has a global semantic and which is compliant with both the Dense 106 Wavelength Division Multiplexing (DWDM) grid [G.694.1] and the Coarse 107 Wavelength Division Multiplexing (CWDM) grid [G.694.2]. The terms 108 DWDM and CWDM are defined in [G.671]. 110 A flexible grid network selects its data channels as arbitrarily 111 assigned pieces of the spectrum. Mixed bitrate transmission systems 112 can allocate their channels with different spectral bandwidths so 113 that the channels can be optimized for the bandwidth requirements of 114 the particular bit rate and modulation scheme of the individual 115 channels. This technique is regarded as a promising way to improve 116 the network utilization efficiency and fundamentally reduce the cost 117 of the core network. 119 The "flexi-grid" has been developed within the ITU-T Study Group 15 120 to allow selection and switching of pieces of the optical spectrum 121 chosen flexibly from a fine granularity grid of wavelengths with 122 variable spectral bandwidth [G.694.1]. This document updates the 123 definition of GMPLS lambda labels provided in [RFC6205] to support 124 the flexi-grid. 126 This document relies on [G.694.1] for the definition of the optical 127 data plane and does not make any updates to the work of the ITU-T in 128 that regard. 130 1.1. Conventions Used in This Document 132 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 133 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 134 document are to be interpreted as described in [RFC2119]. 136 2. Overview of Flexi-Grid 138 [G.694.1] defines DWDM fixed grids. The latest version of that 139 document extends the DWDM fixed grids to add support for flexible 140 grids. The basis of the work is to allow a data channel to be formed 141 from an abstract grid anchored at 193.1 THz and selected on a channel 142 spacing of 6.25 GHz with a variable slot width measured in units of 143 12.5 GHz. Individual allocations may be made on this basis from 144 anywhere in the spectrum, subject to allocations not overlapping. 146 [G.694.1] provides clear guidance on the support of flexible grid by 147 implementations in Section 2 of Appendix I: 149 The flexible DWDM grid defined in clause 7 has a nominal central 150 frequency granularity of 6.25 GHz and a slot width granularity of 151 12.5 GHz. However, devices or applications that make use of the 152 flexible grid may not have to be capable of supporting every 153 possible slot width or position. In other words, applications may 154 be defined where only a subset of the possible slot widths and 155 positions are required to be supported. 157 For example, an application could be defined where the nominal 158 central frequency granularity is 12.5 GHz (by only requiring 159 values of n that are even) and that only requires slot widths as a 160 multiple of 25 GHz (by only requiring values of m that are even). 162 Some additional background on the use of GMPLS for flexible grids 163 can be found in [FLEXFWRK]. 165 2.1. Composite Labels 167 It is possible to construct an end-to-end connection as a composite 168 of more than one flexi-grid slot. The mechanism used in GMPLS is 169 similar to that used to support inverse multiplexing familiar in 170 time-division multiplexing (TDM) and optical transport networks 171 (OTN). The slots in the set could potentially be contiguous or non- 172 contiguous (only as allowed by the definitions of the data plane) and 173 could be signaled as a single LSP or constructed from a group of 174 LSPs. For more details, refer to Section 4.3. 176 How the signal is carried across such groups of channels is out of 177 scope for this document. 179 3. Fixed Grid Lambda Label Encoding 181 [RFC6205] defines an encoding for a global semantic for a DWDM label 182 based on four fields: 184 - Grid: used to select which grid the lambda is selected from. 185 Values defined in [RFC6205] identify DWDM [G.694.1] and CWDM 186 [G.694.2]. 188 - C.S. (Channel Spacing): used to indicate the channel spacing. 189 [RFC6205] defines values to represent spacing of 100, 50, 25 and 190 12.5 GHz. 192 - Identifier: a local-scoped integer used to distinguish different 193 lasers (in one node) when they can transmit the same frequency 194 lambda. 196 - n: a two's-complement integer to take a positive, negative, or zero 197 value. This value is used to compute the frequency as defined in 198 [RFC6205] and based on [G.694.1]. The use of n is repeated here 199 for ease of reading the rest of this document: in case of 200 discrepancy, the definition in [RFC6205] is normative. 202 Frequency (THz) = 193.1 THz + n * frequency granularity (THz) 204 where the nominal central frequency granularity for the flexible 205 grid is 0.00625 THz 207 4. Flexi-Grid Label Format and Values 209 4.1 Flexi-Grid Label Encoding 211 This document defines a generalized label encoding for use in flexi- 212 grid systems. As with the other GMPLS lambda label formats defined 213 in [RFC3471] and [RFC6205], the use of this label format is known a 214 priori. That is, since the interpretation of all lambda labels is 215 determined hop-by-hop, the use of this label format requires that all 216 nodes on the path expect to use this label format. 218 For convenience, however, the label format is modeled on the fixed 219 grid label defined in [RFC6205] and briefly described in Section 3. 221 Figure 1 shows the format of the Flexi-Grid Label. It is a 64 bit 222 label. 224 0 1 2 3 225 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 227 |Grid | C.S. | Identifier | n | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 | m | Reserved | 230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 232 Figure 1 : The Flexi-Grid Label Encoding 234 This document defines a new Grid value to supplement those in 235 [RFC6205]: 237 +----------+---------+ 238 | Grid | Value | 239 +----------+---------+ 240 |ITU-T Flex| 3 | 241 +----------+---------+ 243 Within the fixed grid network, the C.S. value is used to represent 244 the channel spacing, as the spacing between adjacent channels is 245 constant. For the flexible grid situation, this field is used to 246 represent the nominal central frequency granularity. 248 This document defines a new C.S. value to supplement those in 249 [RFC6205]: 251 +----------+---------+ 252 | C.S(GHz) | Value | 253 +----------+---------+ 254 | 6.25 | 5 | 255 +----------+---------+ 257 The meaning of the Identifier field is maintained from [RFC6205] (see 258 also Section 3). 260 The meaning of n is maintained from [RFC6205] (see also Section 3). 262 The m field is used to identify the slot width according to the 263 formula given in [G.694.1] as follows. It is a 16 bit integer value 264 encoded in lne format. 266 Slot Width (GHz) = 12.5 GHz * m 268 The Reserved field MUST be set to zero on transmission and SHOULD be 269 ignored on receipt. 271 An implementation that wishes to use the flexi-grid label encoding 272 MUST follow the procedures of [RFC3473] and of [RFC3471] as updated 273 by [RFC6205]. It MUST set Grid to 3 and C.S. to 5. It MUST set 274 Identifier to indicate the local identifier of the laser in use as 275 described in [RFC6205]. It MUST also set n according to the formula 276 in Section 3 (inherited unchanged from [RFC6205]). Finally, the 277 implementation MUST set m as described in the formula stated above. 279 4.2. Considerations of Bandwidth 281 There is some overlap between the concepts of bandwidth and label in 282 many GMPLS-based systems where a label indicates a physical switching 283 resource. This overlap is increased in a flexi-grid system where a 284 label value indicates the slot width and so affects the bandwidth 285 supported by an LSP. Thus the 'm' parameter is both a property of 286 the label (i.e., it helps define exactly what is switched) and of the 287 bandwidth. 289 In GMPLS signaling [RFC3473], bandwidth is requested in the TSpec 290 object and confirmed in the Flowspec object. The 'm' parameter that 291 is a parameter of the GMPLS flexi-grid label as described above, is 292 also a parameter of the flexi-grid TSpec and Flowspec as described in 293 [FLEXRSVP]. 295 4.3. Composite Labels 297 The creation of a composite of multiple channels to support inverse 298 multiplexing is already supported in GMPLS for TDM and OTN [RFC4606], 299 [RFC6344], [RFC7139]. The mechanism used for flexigrid is similar. 301 To signal an LSP that uses multiple flexi-grid slots a "compound 302 label" is constructed. That is, the LABEL object is constructed from 303 a concatenation of the 64-bit Flexi-Grid Labels shown in Figure 1. 304 The number of elements in the label can be determined from the length 305 of the LABEL object. The resulting LABEL object is shown in Figure 306 2 including the object header that is not normally shown in 307 diagrammatic representations of RSVP-TE objects. Note that r is the 308 count of component labels, and this is backward compatible with the 309 label shown in Figure 1 where the value of r is 1. 311 The order of component labels MUST be presented in increasing order 312 of the value n. Implementations MUST NOT infer anything about the 313 encoding of a signal into the set of slots represented by a compound 314 label from the label itself. Information about the encoding MAY be 315 handled in other fields in signaling messages or through an out of 316 band system, but such considerations are out of the scope of this 317 document. 319 0 1 2 3 320 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 | Object Length (4 + 8r) | Class-Num (16)| C-Type (2) | 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 |Grid | C.S. | Identifier | n | 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | m | Reserved | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 ~ ~ 329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 330 |Grid | C.S. | Identifier | n | 331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 332 | m | Reserved | 333 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 335 Figure 2 : A Compound Label for Virtual Concatenation 337 Note that specific rules must be applied as follows: 339 - Grid MUST show "ITU-T Flex" value 3 in each component label. 340 - C.S. MUST have the same value in each component label. 341 - Identifier in each component label may identify different physical 342 equipment. 343 - Values of n and m in each component label define the slots that 344 are concatenated. 346 At the time of writing [G.694.1] only supports only groupings of 347 adjacent slots (i.e., without intervening unused slots that could be 348 used for other purposes) of identical width (same value of m), and 349 the component slots must be in increasing order of frequency (i.e., 350 increasing order of the value n). The mechanism defined here MUST 351 NOT be used for other forms of grouping unless and until those forms 352 are defined and documented in Recommendations published by the ITU-T. 354 Note further that while the mechanism described here naturally means 355 that all component channels are corouted, a composite channel can 356 also be achieved by constructing individual LSPs from single flexi- 357 grid slots and managing those LSPs as a group. A mechanism for 358 achieving this for TDM is described in [RFC6344], but is out of scope 359 for discussion in this document because the labels used are normal, 360 single slot labels and require no additional definitions. 362 5. Manageability Considerations 364 This document introduces no new elements for management. That is, 365 labels can continue to be used in the same way by the GMPLS protocols 366 and where those labels were treated as opaque quantities with local 367 or global significance, no change is needed to the management 368 systems. 370 However, this document introduces some changes to the nature of a 371 label that may require changes to management systems. Firstly, 372 systems that handle lambda labels as 32 bit quantities need to be 373 updated to process the 64 bit labels described in this document even 374 if the labels are treated as opaque quantities. Furthermore, 375 although management systems that can handle lambda labels as defined 376 in [RFC6205] can continue to process the fields defined in RFC 6205 377 as before, they have to handle new legal values of some of those 378 fields (Grid = 3 and C.S. = 5), and they have to be aware of the new 379 'm' field. 381 6. Implementation Status 383 [RFC Editor Note: Please remove this entire seciton prior to publication 384 as an RFC.] 386 This section records the status of known implementations of the 387 protocol defined by this specification at the time of posting of this 388 Internet-Draft, and is based on a proposal described in RFC 6982 389 [RFC6982]. The description of implementations in this section is 390 intended to assist the IETF in its decision processes in progressing 391 drafts to RFCs. Please note that the listing of any individual 392 implementation here does not imply endorsement by the IETF. 393 Furthermore, no effort has been spent to verify the information 394 presented here that was supplied by IETF contributors. This is not 395 intended as, and must not be construed to be, a catalog of available 396 implementations or their features. Readers are advised to note that 397 other implementations may exist. 399 According to RFC 6982, "this will allow reviewers and working groups 400 to assign due consideration to documents that have the benefit of 401 running code, which may serve as evidence of valuable experimentation 402 and feedback that have made the implemented protocols more mature. 403 It is up to the individual working groups to use this information as 404 they see fit." 406 6.1. Centre Tecnologic de Telecomunicacions de Catalunya (CTTC) 408 Organization Responsible for the Implementation: 409 Centre Tecnologic de Telecomunicacions de Catalunya (CTTC) 410 Optical Networks and Systems Department 412 Implementation Name and Details: 413 ADRENALINE testbed 414 http://networks.cttc.es/experimental-testbeds/ 416 Brief Description: 417 Experimental testbed implementation of GMPLS/PCE control plane. 419 Level of Maturity: 420 Implemented as extensions to a mature GMLPS/PCE control plane. 421 It is limited to research / prototyping stages but it has been 422 used successfully for more than the last five years. 424 Coverage: 425 Support for the 64 bit label as described version 07 of this 426 document. 427 This affects mainly the implementation of RSVP-TE and PCEP 428 protocols: 430 - Generalized Label Support 431 - Suggested Label Support 432 - Upstream Label Support 433 - ERO Label Subobjects and Explicit Label Control 434 It is expected that this implementation will evolve to follow the 435 evolution of this document. 437 Licensing: 438 Proprietary 440 Implementation Experience: 441 Implementation of this document reports no issues. 442 General implementation experience has been reported in a number of 443 journal papers. Contact Ramon Casellas for more information or see 444 http://networks.cttc.es/publications/? 445 search=GMPLS&research_area=optical-networks-systems 447 Contact Information: 448 Ramon Casellas: ramon.casellas@cttc.es 450 Interoperability: 451 No report. 453 7. Security Considerations 455 [RFC6205] notes that the definition of a new label encoding does not 456 introduce any new security considerations to [RFC3471] and [RFC3473]. 457 That statement applies equally to this document. 459 For a general discussion on MPLS and GMPLS-related security issues, 460 see the MPLS/GMPLS security framework [RFC5920]. 462 8. IANA Considerations 464 IANA maintains the "Generalized Multi-Protocol Label Switching 465 (GMPLS) Signaling Parameters" registry that contains several 466 subregistries. 468 8.1. Grid Subregistry 470 IANA is requested to allocate a new entry in this subregistry as 471 follows: 473 Value Grid Reference 474 ----- ------------------------- ---------- 475 3 ITU-T Flex [This.I-D] 477 8.2. DWDM Channel Spacing Subregistry 479 IANA is requested to allocate a new entry in this subregistry as 480 follows: 482 Value Channel Spacing (GHz) Reference 483 ----- ------------------------- ---------- 484 5 6.25 [This.I-D] 486 9. Acknowledgments 488 This work was supported in part by the FP-7 IDEALIST project under 489 grant agreement number 317999. 491 Very many thanks to Lou Berger for discussions of labels of more than 492 32 bits. Many thanks to Sergio Belotti and Pietro Vittorio Grandi 493 for their support of this work. Thanks to Gabriele Galimberti for 494 discussion of the size of the "m" field, and to Iftekhar Hussain for 495 discussion of composite labels. 497 Special thanks to the Vancouver 2012 Pool Party for discussions and 498 rough consensus: Dieter Beller, Ramon Casellas, Daniele Ceccarelli, 499 Oscar Gonzalez de Dios, Iftekhar Hussain, Cyril Margaria, Lyndon Ong, 500 and Fatai Zhang. 502 The authors would like to thank Ben Niven-Jenkins for inspiring the 503 choice of filename for this document. 505 10. References 507 10.1. Normative References 509 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 510 Requirement Levels", BCP 14, RFC 2119, March 1997. 512 [RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label 513 Switching (GMPLS) Signaling Functional Description", RFC 514 3471, January 2003. 516 [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label 517 Switching (GMPLS) Signaling Resource ReserVation Protocol- 518 Traffic Engineering (RSVP-TE) Extensions", RFC 3473, 519 January 2003. 521 [RFC6205] Otani, T., and Li, D., "Generalized Labels for Lambda- 522 Switch-Capable (LSC) Label Switching Routers", RFC 6205, 523 October 2011. 525 [G.694.1] ITU-T Recommendation G.694.1 (revision 2), "Spectral grids 526 for WDM applications: DWDM frequency grid", February 2012. 528 10.2. Informative References 530 [RFC3945] Mannie, E., Ed., "Generalized Multi-Protocol Label 531 Switching (GMPLS) Architecture", RFC 3945, October 2004. 533 [RFC4606] Mannie, E., and Papadimitriou, D., "Generalized Multi- 534 Protocol Label Switching (GMPLS) Extensions for 535 Synchronous Optical Network (SONET) and Synchronous 536 Digital Hierarchy (SDH) Control", RFC 4606, August 2006. 538 [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS 539 Networks", RFC 5920, July 2010. 541 [RFC6344] Bernstein, G., Caviglia, D., Rabbat, R., and van Helvoort, 542 H., "Operating Virtual Concatenation (VCAT) and the Link 543 Capacity Adjustment Scheme (LCAS) with Generalized Multi- 544 Protocol Label Switching (GMPLS)", RFC 6344, August 2011. 546 [RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 547 Code: The Implementation Status Section", RFC 6982, July 548 2013. 549 [RFC Editor Note: This reference can be removed when Section 6 is 550 removed] 552 [RFC7139] Zhang, F., Zhang, G., Belotti, S., Ceccarelli, D., and 553 Pithewan, K., "GMPLS Signaling Extensions for Control of 554 Evolving G.709 Optical Transport Networks", RFC 7139, 555 March 2014. 557 [G.671] ITU-T Recommendation G.671, "Transmission characteristics 558 of optical components and subsystems", 2009. 560 [G.694.2] ITU-T Recommendation G.694.2, "Spectral grids for WDM 561 applications: CWDM wavelength grid", December 2003. 563 [FLEXFWRK] O. Gonzalez de Dios, et al., "Framework and Requirements 564 for GMPLS based control of Flexi-grid DWDM networks", 565 draft-ogrcetal-ccamp-flexi-grid-fwk, work in progress. 567 [FLEXRSVP] Zhang, F., Gonzalez de Dios, O., and D. Ceccarelli, 568 "RSVP-TE Signaling Extensions in support of Flexible 569 Grid", draft-zhang-ccamp-flexible-grid-rsvp-te-ext, work 570 in progress. 572 Appendix A. Flexi-Grid Example 574 Consider a fragment of an optical LSP between node A and node B using 575 the flexible grid. Suppose that the LSP on this hop is formed: 576 - using the ITU-T Flexi-Grid 577 - the nominal central frequency of the slot 193.05 THz 578 - the nominal central frequency granularity is 6.25 GHz 579 - the slot width is 50 GHz. 581 In this case the label representing the switchable quantity that is 582 the flexi-grid quantity is encoded as described in Section 4.1 with 583 the following parameter settings. The label can be used in signaling 584 or in management protocols to describe the LSP. 586 Grid = 3 : ITU-T Flexi-Grid 588 C.S. = 5 : 6.25 GHz nominal central frequency granularity 590 Identifier = local value indicating the laser in use 592 n = -8 : 594 Frequency (THz) = 193.1 THz + n * frequency granularity (THz) 596 193.05 (THz) = 193.1 (THz) + n * 0.00625 (THz) 598 n = (193.05-193.1)/0.00625 = -8 600 m = 4 : 602 Slot Width (GHz) = 12.5 GHz * m 604 50 (GHz) = 12.5 (GHz) * m 606 m = 50 / 12.5 = 4 608 Authors' Addresses 610 Adrian Farrel 611 Old Dog Consulting 612 EMail: adrian@olddog.co.uk 614 Daniel King 615 Old Dog Consulting 616 EMail: daniel@olddog.co.uk 618 Yao Li 619 Nanjing University 620 EMail: wsliguotou@hotmail.com 622 Fatai Zhang 623 Huawei Technologies 624 EMail: zhangfatai@huawei.com 626 Contributors' Addresses 628 Zhang Fei 629 Huawei Technologies 630 EMail: zhangfei7@huawei.com 632 Ramon Casellas 633 CTTC 634 EMail: ramon.casellas@cttc.es