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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' -- Possible downref: Non-RFC (?) normative reference: ref. 'G.694.2' ** Downref: Normative reference to an Informational RFC: RFC 6163 == Outdated reference: A later version (-20) exists of draft-ietf-ccamp-general-constraint-encode-05 == Outdated reference: A later version (-24) exists of draft-ietf-ccamp-rwa-info-11 == Outdated reference: A later version (-28) exists of draft-ietf-ccamp-rwa-wson-encode-11 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Y. Li 3 Internet-Draft F. Zhang 4 Intended status: Standards Track ZTE 5 Expires: January 5, 2012 R. Casellas 6 CTTC 7 July 4, 2011 9 Flexible Grid Label Format in Wavelength Switched Optical Network 10 draft-li-ccamp-flexible-grid-label-00 12 Abstract 14 Flexible grid is regarded as an efficient way to improve the network 15 capacity utilization. Mixed bit rate transmission systems can 16 allocate their channel with different spectral bandwidths so that 17 they can be optimized for the bandwidth requirements of the 18 particular bit rate and modulation scheme of the individual channels. 19 To support the flexible grid technique, this document extends the 20 wavelength label to accommodate this new specification. It is 21 demonstrated that the extended label format is compatible to the 22 rigid one and can be used in the routing and signaling procedure in 23 the Wavelength Switched Optical Network (WSON). 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on January 5, 2012. 42 Copyright Notice 44 Copyright (c) 2011 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 61 3. Label format . . . . . . . . . . . . . . . . . . . . . . . . . 4 62 3.1. Label values . . . . . . . . . . . . . . . . . . . . . . . 4 63 3.2. Flexible Label . . . . . . . . . . . . . . . . . . . . . . 5 64 4. Flexible label applications . . . . . . . . . . . . . . . . . 7 65 4.1. Application for Routing . . . . . . . . . . . . . . . . . 7 66 4.2. Applications for Signaling . . . . . . . . . . . . . . . . 8 67 4.3. Applications for PCE . . . . . . . . . . . . . . . . . . . 8 68 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 69 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 70 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 71 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 72 8.1. Normative references . . . . . . . . . . . . . . . . . . . 9 73 8.2. Informative References . . . . . . . . . . . . . . . . . . 9 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 76 1. Introduction 78 Dense Wavelength Division Multiplexing (DWDM) optical network is 79 widely deployed by telecom operators to carry their data service. 80 With the continuing exponential growth of internet traffic, more 81 efficient utilization of optical network bandwidth for extremely high 82 data rates is required. Although multi-level modulation formats and 83 advanced photonics techniques have enabled 100 G/s transmission 84 within a 50 GHz DWDM fixed gird (or channel spacing), much higher 85 speed traffic, such as 400 Gbit/s and 1 Tbit/s signals are not 86 expected to adapt such a narrow channel. So a wider fixed grid like 87 100 GHz spacing is required to enable these new transmission formats 88 without inter-channel crosstalk. However, the total available 89 spectrum resource of the specific band is limited (about 4.4 THz in C 90 band). If a wider grid is chosen, the fewer wavelengths can be 91 allocated to carry the data. Not to mention that some low bitrate 92 signals will occupy too much spectral bandwidth so that the total 93 utilization efficiency of the spectrum resource is relatively low. 95 The recent revision of ITU-T Recommendation [G.694.1] has decided to 96 introduce the flexible grid DWDM technique which provide a new tool 97 that operators can implement to provide a higher degree of network 98 optimization than fixed grid systems. Flexible grid network is 99 composed of arbitrarily assigned spectral slices. That means in such 100 networks the adjacent channel spacing and assigned spectral bandwidth 101 per wavelength are variable. Mixed bitrate transmission systems can 102 allocate their channel with different spectral bandwidths so that 103 they can be optimized for the bandwidth requirements of the 104 particular bit rate and modulation scheme of the individual channels. 105 This technique is regarded to be a promising way to improve the 106 network utilization efficiency and fundamentally reduce the cost of 107 the IP core network. 109 Based on the DWDM technique, Wavelength Switched Optical Network 110 (WSON) uses the control plane to dynamically provide Label Switched 111 Paths (LSPs) for the requested end to end connections. The label 112 switching is performed selectively on wavelength label representing 113 the center wavelength/frequency of the optical signal. To support 114 the flexible grid technique, this document extends the wavelength 115 label defined in [RFC6205] to accommodate the new specification. It 116 is proved that the extended label format is compatible to the rigid 117 one and can be used in the routing and signaling procedure in WSON 118 and generic GMPLS network. 120 2. Terminology 122 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 123 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 124 document are to be interpreted as described in RFC 2119 [RFC2119]. 126 3. Label format 128 3.1. Label values 130 The wavelength label format is defined in [RFC6205] and the 131 corresponding wavelength or frequency value is referred to ITU-T 132 Recommendations [G.694.1] and [G.694.2] for DWDM and CWDM grid 133 respectively. The ITU-T fixed grid is based on nominal center 134 frequency/wavelength. 136 For DWDM system, the nominal center frequency is calculated as: 138 Frequency (THz)=193.1 THz+n* channel spacing 140 In the context of rigid grid, the channel spacing of DWDM can support 141 12.5 GHz, 25 GHz, 50 GHz, or 100 GHz. However, once chosen, the 142 adjacent channel spacing of the wavelengths is fixed. As mentioned 143 in the section 1, 50 GHz channel spacing is most commonly used. 145 The recent revision of [G.694.1] has defined suggested values for the 146 flexible DWDM grid. The concept of "frequency slot" is introduced to 147 describe the frequency range allocated to a channel. A frequency 148 slot is defined by its nominal central frequency and its required 149 slot width values. 151 For the flexible DWDM grid, the allowed frequency slots have a 152 nominal central frequency (in THz) defined by: 154 Frequency (THz)=193.1 THz + n * 0.00625 156 and a slot width (the same meaning as the spectral bandwidth) defined 157 by: 159 12.5 GHz * m 161 where m is a positive integer. 163 The nominal center frequency representations of the fixed grid and 164 flexible grid types are similar except that the latter has a more 165 precise channel spacing granularity (6.25 GHz). Meanwhile the 166 adjacent channel spacing (the spacing of the adjacent nominal center 167 frequency) is implied to be (n1-n2) * 6.25 GHz, where n1 and n2 168 represent the n number defined above for the nominal center frequency 169 of the adjacent frequency slots respectively (n is an integer 170 including positive, negative integer and 0). The slot width assigned 171 to a frequency slot is arbitrary times of the slot width granularity. 172 It was agreed on flexible grids with a granularity of 6.25 GHz for 173 the central frequency and slot width of a multiple of 12.5 GHz. The 174 slot width granularity is twice the channel spacing granularity, so 175 that by carefully choosing n and m, the spectral resources can be 176 allocated without leaving any gaps between slots. Therefore, in 177 contrast to the rigid label, the new flexible label should have a 178 capability to indicating the slot width allocation. 180 Note that in this document, the concepts "slot width" and "frequency 181 slot" are similar to "spectral bandwidth" and "wavelength channel" 182 respectively. 184 3.2. Flexible Label 186 To accommodate the new feature mentioned above, the wavelength label 187 supporting flexible grid is illustrated as follows : 189 0 1 2 3 190 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 1 191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 192 |Grid | C.S. | Identifier | n | 193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 194 | Additional slot width parameters | 195 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 197 Additional slot width parameters: 199 0 1 2 3 200 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 1 201 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 202 | m | Reserved | 203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 205 Grid: 207 One new Grid type called "Flexible DWDM" is defined. 209 +---------------+-------+ 210 | Grid | Value | 211 +---------------+-------+ 212 | Reserved | 0 | 213 +---------------+-------+ 214 | ITU-T DWDM | 1 | 215 +---------------+-------+ 216 | ITU-T CWDM | 2 | 217 +---------------+-------+ 218 +---------------+-------+ 219 | Flexible DWDM | 3 | 220 +---------------+-------+ 221 | Future use | 4-7 | 222 +---------------+-------+ 224 C.S.: 226 For Grid=1 and 2, C.S. is referred to DWDM and CWDM channel spacing 227 [RFC6205], which indicates that the adjacent channel spacing is 228 constant. In this situation, the spectral bandwidth value allocated 229 to every single channel is equal to value of the channel spacing. 231 For Grid=3, C.S. is referred to channel spacing granularity, 232 accordingly the slot width granularity is twice of the C.S.. Minimum 233 channel spacing granularity of 6.25 GHz with a slot width granularity 234 of 12.5 GHz is supported. 236 +------------+-------+ 237 | C.S. (GHz) | Value | 238 +------------+-------+ 239 | Reserved | 0 | 240 +------------+-------+ 241 | 100 | 1 | 242 +------------+-------+ 243 | 50 | 2 | 244 +------------+-------+ 245 | 25 | 3 | 246 +------------+-------+ 247 | 12.5 | 4 | 248 +------------+-------+ 249 | 6.25 | 5 | 250 +------------+-------+ 251 | Future use | 6-15 | 252 +------------+-------+ 254 Identifier: 256 The identifier field in the flexible label format is left unmodified 257 compared with [RFC6205]. It is defined to distinguish which 258 transmitter is used to carry the lambda. This identifier only has a 259 local significance that should be indicated in the signaling message 260 for LSP establishment. For routing information flooding, this filed 261 is meaningless and should be ignored on receipt. 263 n: 265 This field is used to compute the nominal center frequency/wavelength 266 of the channel mentioned above. Together with the channel spacing 267 granularity (C.S.), the spacing of the adjacent channel is (n1-n2) * 268 6.25 GHz in flexible grid network (see definition of n1 and n2 in 269 section 3.1). 271 Additional slot width parameters. 273 The slot width parameters field is mandatory only when Grid is set to 274 3 for flexible grid condition. These 5 bits field are used to 275 represent how many slot width granularity the label has occupied. As 276 the granularity is defined to be twice of the channel spacing 277 granularity, so the slot width is calculated to be m * 2 * C.S.. 279 4. Flexible label applications 281 This section illustrated the routing, signaling, PCE application of 282 the extended flexible grid label. 284 4.1. Application for Routing 286 Flexible grid is regarded as an enabler for another kind of networks, 287 requiring network elements, or nodes, that go past beyond the 288 functional requirements of OXCs or ROADMs, in the sense that they do 289 switching based on a frequency range. This means that a new swithing 290 type called e.g. "Spectrum Selective Switching" in Interface 291 Switching Capability Descriptor (ISCD) SHOULD be defined. However 292 this is beyond the scope of this document and will be studied in the 293 routing draft. 295 In addition to the topology information, wavelength constraints 296 information like Port Label Restrictions, Shared Backup Labels, 297 Resource Pool Wavelength Constrains, Resource Block Available 298 Wavelengths detailed in [I-D.ietf-ccamp-rwa-info] should be flooded 299 in the network through routing protocol like OSPF-TE. All the 300 information is described by the label set object. The general label 301 set is described in [RFC3471] and specific wavelength label set in 302 [I-D.ietf-ccamp-general-constraint-encode] . There are 5 ways to 303 represent the wavelength label set 305 1. Inclusive list 306 2. Exclusive list 307 3. Inclusive range 308 4. Exclusive range 309 5. Bitmap set 311 For flexible grid optical network, the label set should be more 312 actually to represent the spectral resources constraints. For type 1 313 and 2, flexible label with different slot width is acceptable to put 314 into the list. For type 3 and 4, start label and end label with 315 minimal slot width (while it is not mandatory) is RECOMMENDED. For 316 type 5, the base label/frequency slot is REQUIRED to have a minimum 317 slot width (m=1). As there MAY exist some situations that the unused 318 bandwidth between two occupied bandwidth is odd times of the channel 319 spacing granularity (not integral times of the slot with 320 granularity), two bits are needed to represent a single slot. It can 321 be seen that these 5 types of representations can be easily inherited 322 by incorporating the new flexible label into the object. Note that 323 in the procedure of wavelength constraints flooding, any combination 324 of the 5 types of label sets is feasible. 326 4.2. Applications for Signaling 328 In flexibel grid network, flexible label representing frequency 329 "slots" or "ranges" rather than individual wavelengths is requested 330 to establish the LSP. The extensions to the Genralized Label Request 331 object and TSPEC object are needed, this will be studied in the 332 future. 334 To establish a label switched path, an available wavelength label 335 satisfying the wavelength continuity constraints is reserved with 336 signaling protocol like RSVP-TE. For the flexible grid DWDM network, 337 this procedure should be modified to assign available spectral 338 resources. In other words, the label is not only assigning the 339 nominal center frequency of wavelength but also the slot width for 340 the LSP. The slot width is definitely clarified through the field m 341 in the label. Nevertheless in the procedure, wavelength continuity 342 constraint is unchanged. 344 4.3. Applications for PCE 346 [RFC6163] describes a Path Computation Element (PCE) can be used to 347 performing routing and wavelength assignment in WSON. [RFC5440] 348 details the path computation element communication protocol messages 349 for this purpose. According to the modulation format, FEC type, 350 client 351 bitrates[I-D.ietf-ccamp-rwa-info][I-D.ietf-ccamp-rwa-wson-encode], 352 and physical impairment, the required frequency slot indicated by 353 flexible label should be calculated out by the PCE to carry the 354 client signal. 356 5. Acknowledgements 358 6. IANA Considerations 360 A future revision of this document will present requests to IANA for 361 codepoint allocation. 363 7. Security Considerations 365 8. References 367 8.1. Normative references 369 [G.694.1] International Telecommunications Union, "Spectral grids 370 for WDM applications: DWDM frequency grid", Recommendation 371 G.694.1, June 2002 . 373 [G.694.2] International Telecommunications Union, "Spectral grids 374 for WDM applications: CWDM wavelength grid", 375 Recommendation G.694.2, December 2003 . 377 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 378 Requirement Levels", BCP 14, RFC 2119, March 1997. 380 [RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching 381 (GMPLS) Signaling Functional Description", RFC 3471, 382 January 2003. 384 [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element 385 (PCE) Communication Protocol (PCEP)", RFC 5440, 386 March 2009. 388 [RFC6163] Lee, Y., Bernstein, G., and W. Imajuku, "Framework for 389 GMPLS and Path Computation Element (PCE) Control of 390 Wavelength Switched Optical Networks (WSONs)", RFC 6163, 391 April 2011. 393 [RFC6205] Otani, T. and D. Li, "Generalized Labels for Lambda- 394 Switch-Capable (LSC) Label Switching Routers", RFC 6205, 395 March 2011. 397 8.2. Informative References 399 [I-D.ietf-ccamp-general-constraint-encode] 400 Bernstein, G., Lee, Y., Li, D., and W. Imajuku, "General 401 Network Element Constraint Encoding for GMPLS Controlled 402 Networks", draft-ietf-ccamp-general-constraint-encode-05 403 (work in progress), May 2011. 405 [I-D.ietf-ccamp-rwa-info] 406 Bernstein, G., Lee, Y., Li, D., and W. Imajuku, "Routing 407 and Wavelength Assignment Information Model for Wavelength 408 Switched Optical Networks", draft-ietf-ccamp-rwa-info-11 409 (work in progress), March 2011. 411 [I-D.ietf-ccamp-rwa-wson-encode] 412 Bernstein, G., Lee, Y., Li, D., Imajuku, W., and J. Han, 413 "Routing and Wavelength Assignment Information Encoding 414 for Wavelength Switched Optical Networks", 415 draft-ietf-ccamp-rwa-wson-encode-11 (work in progress), 416 March 2011. 418 Authors' Addresses 420 Yao Li 421 ZTE 422 P.R.China 424 Phone: +86 025 52871109 425 Email: li.yao3@zte.com.cn 427 Zhang Fei 428 ZTE 429 P.R.China 431 Phone: +86 025 52871109 432 Email: zhang.fei3@zte.com.cn 434 Ramon Casellas 435 CTTC 436 Spain 438 Phone: +34 936452916 439 Email: ramon.casellas@cttc.es