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'G.694.2' == Outdated reference: A later version (-07) exists of draft-ietf-ccamp-flexi-grid-fwk-02 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 5 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group X. Fu, Ed. 3 Internet-Draft ZTE 4 Intended status: Standards Track G. Zhang, Ed. 5 Expires: September 10, 2015 CAICT 6 Y. Li 7 Nanjing University 8 R. Casellas 9 CTTC 10 Y. Wang 11 CAICT 12 March 9, 2015 14 Link Management Protocol Extensions for Grid Property Negotiation 15 draft-ietf-ccamp-grid-property-lmp-01 17 Abstract 19 ITU-T [G.694.1] introduces the flexible-grid DWDM technique, which 20 provides a new tool that operators can implement to provide a higher 21 degree of network optimization than is possible with fixed-grid 22 systems. This document describes the extensions to the Link 23 Management Protocol (LMP) to negotiate link grid property between the 24 adjacent DWDM nodes before the link is brought up. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at http://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on September 10, 2015. 43 Copyright Notice 45 Copyright (c) 2015 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (http://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 1.1. Conventions Used in This Document . . . . . . . . . . . . 3 62 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 3. Requirements for Grid Property Negotiation . . . . . . . . . 3 64 3.1. Flexi-fixed Grid Nodes Interworking . . . . . . . . . . . 3 65 3.2. Flexible-Grid Capability Negotiation . . . . . . . . . . 4 66 3.3. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 5 67 4. LMP extensions . . . . . . . . . . . . . . . . . . . . . . . 5 68 4.1. Grid Property Subobject . . . . . . . . . . . . . . . . . 5 69 5. Messages Exchange Procedure . . . . . . . . . . . . . . . . . 7 70 5.1. Flexi-fixed Grid Nodes Messages Exchange . . . . . . . . 7 71 5.2. Flexible Nodes Messages Exchange . . . . . . . . . . . . 8 72 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 73 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 74 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 75 9. Contributing Authors . . . . . . . . . . . . . . . . . . . . 9 76 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 77 10.1. Normative References . . . . . . . . . . . . . . . . . . 10 78 10.2. Informative References . . . . . . . . . . . . . . . . . 10 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 81 1. Introduction 83 ITU-T [G.694.1] introduces the flexible-grid DWDM technique, which 84 provides a new tool that operators can implement to provide a higher 85 degree of network optimization than is possible with fixed-grid 86 systems. A flexible-grid network supports allocating a variable- 87 sized spectral slot to a channel. Flexible-grid DWDM transmission 88 systems can allocate their channels with different spectral 89 bandwidths/slot widths so that they can be optimized for the 90 bandwidth requirements of the particular bit rate and modulation 91 scheme of the individual channels. This technique is regarded to be 92 a promising way to improve the spectrum utilization efficiency and 93 can be used in the beyond 100Gbit/s transport systems. 95 Fixed-grid DWDM system is regarded as a special case of Flexi-grid 96 DWDM. It is expected that fixed-grid optical nodes will be gradually 97 replaced by flexible nodes and interworking between fixed-grid DWDM 98 and flexible-grid DWDM nodes will be needed as the network evolves. 99 Additionally, even two flexible-grid optical nodes may have different 100 grid properties based on the filtering component characteristics, 101 thus need to negotiate on the specific parameters to be used during 102 neighbor discovery process [FLEX-FWK]. This document describes the 103 extensions to the Link Management Protocol (LMP) to negotiate a link 104 grid property between two adjacent nodes before the link is brought 105 up. 107 1.1. Conventions Used in This Document 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 111 document are to be interpreted as described in [RFC2119]. 113 2. Terminology 115 For the flexible-grid DWDM, the spectral resource is called frequency 116 slot which is represented by the central frequency and the slot 117 width. The definition of nominal central frequency, nominal central 118 frequency granularity, slot width and slot width granularity can be 119 referred to [FLEX-FWK]. 121 In this contribution, some other definitions are listed below: 123 Tuning range: It describes the supported spectrum slot range of the 124 switching nodes or interfaces. It is represented by the supported 125 minimal slot width and the maximum slot width. 127 Channel spacing: It is used in traditional fixed-grid network to 128 identify spectrum spacing between two adjacent channels. 130 3. Requirements for Grid Property Negotiation 132 3.1. Flexi-fixed Grid Nodes Interworking 134 Figure 1 shows an example of interworking between flexible and fixed- 135 grid nodes. Node A, B, D and E support flexible-grid. All these 136 nodes can support frequency slots with a central frequency 137 granularity of 6.25 GHz and slot width granularity of 12.5 GHz. 138 Given the flexibility in flexible-grid nodes, it is possible to 139 configure the nodes in such a way that the central frequencies and 140 slot width parameters are backwards compatible with the fixed DWDM 141 grids (adjacent flexible frequency slots with channel spacing of 142 8*6.25 and slot width of 4*12.5 GHz is equivalent to fixed DWDM grids 143 with channel spacing of 50 GHz). 145 As node C can only support the fixed-grid DWDM property with channel 146 spacing of 50 GHz, to establish a LSP through node B, C, D, the links 147 between B to C and C to D must set to align with the fixed-grid 148 values. This link grid property must be negotiated before 149 establishing the LSP. 151 +---+ +---+ +---+ +---+ +---+ 152 | A |---------| B |=========| C |=========| D +--------+ E | 153 +---+ +---+ +---+ +---+ +---+ 155 Figure 1: An example of interworking between flexible and fixed-grid 156 nodes 158 ^ ^ ^ ^ 159 ------->|<----50GHz---->|<----50GHz---->|<----50GHz---->|<------ 160 ..... | | | | ..... 161 +-------+-------+-------+-------+-------+--------+------+-------+- 162 n=-2 -1 0 1 2 163 Fixed channel spacing of 50 GHz (Node C) 164 ^ ^ ^ ^ 165 | | | | 166 --------+---------------+---------------+---------------+--------- 167 ..... | n=-8, m=4 | n=0, m=4 | n=8, m=4 | ..... 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- 169 n=-16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 170 |_| 171 Flexi-grid (Nodes B,D) 6.25 GHz 172 Central frequency granularity=6.25 GHz 173 Slot width granularity=12.5 GHz 175 Figure 2: Representation of fixed channel spacing and flexi-grid 176 spectrum slot 178 3.2. Flexible-Grid Capability Negotiation 180 The updated version of ITU-T [G.694.1] has defined the flexible-grid 181 with a central frequency granularity of 6.25 GHz and a slot width 182 granularity of 12.5 GHz. However, devices or applications that make 183 use of the flexible-grid may not be able to support every possible 184 slot width or position. In other words, applications may be defined 185 where only a subset of the possible slot widths and positions are 186 required to be supported. Taking node G in figure 3 as an example, 187 an application could be defined where the nominal central frequency 188 granularity is 12.5 GHz (by only requiring values of n that are even) 189 requiring slot widths being multiple of 25 GHz (by only requiring 190 values of m that are even). Therefore the link between two optical 191 node F and G with different grid granularity must be configured to 192 align with the larger of both granularities. Besides, different 193 nodes may have different slot width tuning ranges. For example, in 194 figure 3, node F can only support slot width with tuning change from 195 12.5 to 100 GHz, while node G supports tuning range from 25 GHz to 196 200 GHz. The link property of slot width tuning range for the link 197 between F and G should be chosen as the range intersection, resulting 198 in a range from 25 GHz to 100 GHz. 200 +---+ +---+ 201 | F +------------| G | 202 +---+ +---+ 203 +------------------+-------------+-----------+ 204 | Unit (GHz) | Node F | Node G | 205 +------------------+-------------+-----------+ 206 | Grid granularity | 6.25 (12.5) | 12.5 (25) | 207 +------------------+-------------+-----------+ 208 | Tuning range | [12.5, 100] | [25, 200] | 209 +------------------+-------------+-----------+ 211 Figure 3: An example of flexible-grid capability negotiation 213 3.3. Summary 215 In summary, in a DWDM Link between two nodes, the following 216 properties should be negotiated: 218 o Grid capability: flexible grid or fixed grid DWDM. 220 o Nominal central frequency granularity: a multiplier of 6.25 GHz. 222 o Slot width granularity: a multiplier of 12.5 GHz. 224 o Slot width tuning range: two multipliers of 12.5GHz, each indicate 225 the minimal and maximal slot width supported by a port respectively. 227 4. LMP extensions 229 4.1. Grid Property Subobject 231 According to [RFC4204], the LinkSummary message is used to verify the 232 consistency of the link property on both sides of the link before it 233 is brought up. The LinkSummary message contains negotiable and non- 234 negotiable DATA_LINK objects, carrying a series of variable-length 235 data items called subobjects, which illustrate the detailed link 236 properties. The subobjects are defined in Section 12.12.1 in 237 [RFC4204]. 239 To meet the requirements stated in section 3, this draft extends the 240 LMP protocol by introducing a new DATA_LINK subobject called "Grid 241 property", allowing the grid property correlation between adjacent 242 nodes. The encoding format of this new subobject is as follows: 244 0 1 2 3 245 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 1 246 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 247 | Type | Length | Grid | C.F.G | S.W.G | 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 | Min Width | Reserved | Max Width | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 Figure 4 254 Type=TBD, Grid property type. 256 Grid: 4 bits 258 The value is used to represent which grid the node/interface 259 supports. Values defined in [RFC6205] identify DWDM [G.694.1] and 260 CWDM [G.694.2]. The value defined in [draft-ietf-ccamp-flexigrid- 261 lambda-label] identifies flexible DWDM. 263 +---------------+-------+ 264 | Grid | Value | 265 +---------------+-------+ 266 | Reserved | 0 | 267 +---------------+-------+ 268 | ITU-T DWDM | 1 | 269 +---------------+-------+ 270 | ITU-T CWDM | 2 | 271 +---------------+-------+ 272 | ITU-T Flex | 3 | 273 +---------------+-------+ 274 | Future use | 4-16 | 275 +---------------+-------+ 277 C.F.G (central frequency granularity): 279 It is a positive integer. Its value indicates the multiple of 6.25 280 GHz in terms of central frequency granularity. 282 S.W.G (Slot Width Granularity): 284 It is a positive integer value which indicates the slot width 285 granularity which is the multiple of 12.5 GHz. 287 Min Width and Max Width: 289 Min Width and Max Width are positive integers. Their value indicate 290 the multiple of 12.5 GHz in terms of the slot width tuning range the 291 interface supports. For example, for slot width tuning range from 25 292 GHz to 100 GHz (with regard to a node with slot width granularity of 293 12.5 GHz), the values of Min Width and Max Width should be 2 and 8 294 respectively. For fixed-grid nodes, these two fields are meaningless 295 and should be set to zero. 297 5. Messages Exchange Procedure 299 5.1. Flexi-fixed Grid Nodes Messages Exchange 301 To demonstrate the procedure of grid property correlation, the model 302 shown in Figure 1 is reused. Node B starts sending messages. 304 o After inspecting its own node/interface property, node B sends node 305 C a LinkSummary message including the MESSAGE ID, TE_LINK ID and 306 DATA_LINK objects. The setting and negotiating of MESSAGE ID and 307 TE_link ID can be referenced to [RFC4204]. As node B supports 308 flexible-grid property, the Grid and C.F.G values in the grid 309 property subobject are set to be 3 (i.e., ITU-T Flex) and 1 310 (i.e.,1*6.25GHz) respectively. The slot width tuning range is from 311 12.5 GHz to 200 GHz (i.e., Min Width=1, Max Width=16). Meanwhile, 312 the N bit of the DATA_LINK object is set to 1, indicating that the 313 property is negotiable. 315 o When node C receives the LinkSummary message from B, it checks the 316 Grid, C.F.G, Min and Max values in the grid property subobject. Node 317 C can only support fixed-grid DWDM and realizes that the flexible- 318 grid property is not acceptable for the link. Since the receiving N 319 bit in the DATA_LINK object is set, indicating that the Grid property 320 of B is negotiable, node C responds to B with a LinkSummaryNack 321 containing a new Error_code object and state that the property needs 322 further negotiation. Meanwhile, an accepted grid property subobject 323 (Grid=2, C.F.G=4, fixed DWDM with channel spacing of 50 GHz) is 324 carried in LinkSummaryNack message. At this moment, the N bit in the 325 DATA_LINK object is set to 0, indicating that the grid property 326 subobject is non-negotiable. 328 o As the channel spacing and slot width of node B can be configured 329 to be any integral multiples of 6.25 GHz and 12.5 GHz respectively, 330 node B supports the fixed DWDM values announced by node C. 331 Consequently, node B will resend the LinkSummary message carrying the 332 grid property subobject with values of Grid=2 and C.F.G=4. 334 o Once received the LinkSummary message from node B, node C replies 335 with a LinkSummaryACK message. After the message exchange, the link 336 between node B and C is brought up with a fixed channel spacing of 50 337 GHz. 339 In the above mentioned grid property correlation scenario, the node 340 supporting a flexible-grid is the one that starts sending LMP 341 messages. The procedure where the initiator is the fixed-grid node 342 is as follows: 344 o After inspecting its own interface property, Node C sends B a 345 LinkSummary message containing a grid property subobject with Grid=2, 346 C.F.G=4. The N bit in the DATA_LINK object is set to 0, indicating 347 that it is non-negotiable. 349 o As the channel spacing and slot width of node B can be configured 350 to be any integral multiples of 6.25 GHz and 12.5 GHz respectively, 351 node B is able to support the fixed DWDM parameters. Then, node B 352 will make appropriate configuration and reply node C the 353 LinkSummaryACK message 355 o After the message exchange, the link between node B and C is 356 brought up with a fixed channel spacing of 50 GHz. 358 5.2. Flexible Nodes Messages Exchange 360 To demonstrate the procedure of grid property correlation between to 361 flexi-grid capable nodes, the model shown in figure 3 is reused. The 362 procedure of grid property correlation (negotiating the grid 363 granularity and slot width tuning range) is similar to the scenarios 364 mentioned above. 366 o The Grid, C.F.G, Min and Max values in the grid property subobject 367 sent from node F to G are set to be 3,1,1,8 respectively. Meanwhile, 368 the N bit of the DATA_LINK object is set to 1, indicating that the 369 grid property is negotiable. 371 o When node G has received the LinkSummary message from F, it will 372 analyze the Grid, C.F.G, Min and Max values in the Grid property 373 subobject. But node G can only support grid granularity of 12.5 GHz 374 and a slotwdith tuning range from 25 GHz to 200 GHz. Considering the 375 property of node F, node G then will respond F a LinkSummaryNack 376 containing a new Error_code object and state that the property need 377 further negotiation. Meanwhile, an accepted grid property subobject 378 (Grid=3, C.F.G=2, Min=2, Max=8, the slot width tuning range is set to 379 the intersection of Node F and G) is carried in LinkSummaryNack 380 message. Meanwhile, the N bit in the DATA_LINK object is set to 1, 381 indicating that the grid property subobject is non-negotiable. 383 o As the channel spacing and slot width of node F can be configured 384 to be any integral multiples of 6.25 GHz and 12.5 GHz respectively, 385 node F can support the lager granularity. The suggested slot width 386 tuning range is acceptable for node F. In consequence, node F will 387 resend the LinkSummary message carrying the grid subobject with 388 values of Grid=3, C.F.G=2, Min=2 and Max=8. 390 o Once received the LinkSummary message from node F, node G replies 391 with a LinkSummaryACK message. After the message exchange, the link 392 between node F and G is brought up supporting central frequency 393 granularity of 12.5 GHz and slot width tuning range from 25 GHz to 394 100 GHz. 396 From the perspective of the control plane, once the links have been 397 brought up, wavelength constraint information can be advertised and 398 the wavelength label can be assigned hop-by-hop when establishing a 399 LSP based on the link grid property. 401 6. IANA Considerations 403 This draft introduces the following new assignments: 405 LMP Sub-Object Class names: 407 o under DATA_LINK Class name (as defined in [RFC4204]) 409 - Grid property type (sub-object Type = TBD.) 411 7. Acknowledgments 413 This work was supported in part by the China NSFC Project 61201260. 415 8. Security Considerations 417 LMP message security uses IPsec, as described in [RFC4204]. This 418 document only defines new LMP objects that are carried in existing 419 LMP messages. As such, this document introduces no other new 420 security considerations not covered in [RFC4204]. 422 9. Contributing Authors 424 Wenjuan He 425 ZTE 426 he.wenjuan1@zte.com.cn 428 10. References 430 10.1. Normative References 432 [G.694.1] International Telecomunications Union, "Spectral grids for 433 WDM applications: DWDM frequency grid", Recommendation 434 G.694.1 , June 2002. 436 [G.694.2] International Telecomunications Union, "Spectral grids for 437 WDM applications: CWDM wavelength grid", Recommendation 438 G.694.2 , December 2003. 440 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 441 Requirement Levels", BCP 14, RFC 2119, March 1997. 443 [RFC4204] Lang, J., "Link Management Protocol (LMP)", RFC 4204, 444 October 2005. 446 [RFC6205] Otani, T. and D. Li, "Generalized Labels for Lambda- 447 Switch-Capable (LSC) Label Switching Routers", RFC 6205, 448 March 2011. 450 10.2. Informative References 452 [FLEX-FWK] 453 Dios, O., Casellas, R., Zhang, F., Fu, X., Ceccarelli, D., 454 and I. Hussain, , "Framework for GMPLS based control of 455 Flexi-grid DWDM networks", draft-ietf-ccamp-flexi-grid- 456 fwk-02 , August 2014. 458 [draft-ietf-ccamp-flexigrid-lambda-label] 459 Farrel, A., King, D., Li, Y., Zhang, F., , "Generalized 460 Labels for the Flexi-Grid in Lambda-Switch-Capable (LSC) 461 Label Switching Routers", draft-ietf-ccamp-flexigrid- 462 lambda-label-03 , January 2015. 464 Authors' Addresses 466 Xihua Fu (editor) 467 ZTE 469 Email: fu.xihua@zte.com.cn 471 Guoying Zhang (editor) 472 CAICT 474 Email: zhangguoying@catr.cn 475 Yao Li 476 Nanjing University 478 Email: wsliguotou@hotmail.com 480 Ramon Casellas 481 CTTC 483 Email: ramon.casellas@cttc.es 485 Yu Wang 486 CAICT 488 Email: wangyu@catr.cn