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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Qilei Wang 3 Internet-Draft Xihua Fu 4 Intended status: Standards Track ZTE Corporation 5 Expires: August 29, 2013 Feb 25, 2013 7 OSPF extensions for support spectrum sub-band allocation 8 draft-wang-ccamp-flexigrid-wavelength-range-ospf-02.txt 10 Abstract 12 This document addresses the requirements and routing protocol 13 extension of spectrum sub-band allocation in order to help reduce 14 non-linear effect and raise spectrum utilization rate in the scenario 15 of indiscriminately positioning of various channels with different 16 bit rates. 18 Status of this Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at http://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on August 29, 2013. 35 Copyright Notice 37 Copyright (c) 2013 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (http://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 53 2. Conventions used in this document . . . . . . . . . . . . . . 4 54 3. Overview of the Solution . . . . . . . . . . . . . . . . . . . 5 55 4. Extension of routing protocol . . . . . . . . . . . . . . . . 6 56 4.1. Relationship with WSON . . . . . . . . . . . . . . . . . . 6 57 4.2. Extensions of OSPF Protocol to Support Spectrum Group 58 Allocation . . . . . . . . . . . . . . . . . . . . . . . . 7 59 4.2.1. Spectrum sub-band Allocation by Bitrates . . . . . . . 7 60 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 61 6. IANA considerations . . . . . . . . . . . . . . . . . . . . . 9 62 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 63 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 64 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 65 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 67 1. Introduction 69 In current DWDM systems, completely freedom and indiscriminate 70 positioning of various channels with different bit rates is likely to 71 lead to dramatically impaired system performance due to XPM (Cross- 72 phased Modulation) effect and low spectrum utilization rate. 74 Cross phase modulation (XPM) is known as the phenomenon that 75 variations of intensity of one optical signal can change the 76 refractive index of the fiber, and modulate the phase of the other 77 optical signals co-propagating in the same fiber. 79 When DWDM was first introduced, the typical wavelength date rate was 80 2.5Gb/s. 10Gb/s wavelength was enabled because of the development of 81 higher performance optical modulators. However, the same simple 82 modulation format was used at both 2.5Gb/s and 10Gb/s. The 83 modulation technique is Intensity Modulation with Direct Detection 84 (IM-DD). Barrier appeared if we want a wavelength to transport data 85 with 40 Gb/s bitrate or more.After years of development, coherent 86 technology is introduced to broken the limit for 40Gb/s and soon for 87 100Gb/s transmission. 89 Intensity modulation direct detection (IM-DD) systems are less 90 sensitive to the variation of phase of the signal and is going to 91 bring the variation of the intensity, then the changes of refractive 92 index of the fiber. Just the reverse, optical coherent systems is a 93 phase sensitive system. The modulated phase due to XPM has 94 significant influence on the system performance.This is due to the 95 fact that the phase modulation due to XPM can be transformed into 96 intensity modulation through the chromatic dispersion of the fiber 97 and will result in the distortion of signal.For example, if we mix 98 10Gbit/s NRZ modulated channels with 100Gbit/s xPSK modulated 99 channels indiscriminately, XPM would have a detrimental effect on the 100 100Gbit/s signal if this are caused by 10Gbit/s signal; Complex 101 modulation formats (e.g., 16QAM) would be used to modulate signal 102 beyond 100Gbit/s (e.g., 400Gbit/s, 1Tbit/s), while QAM modulation 103 format experiences both intensity and phase modulation, a QAM signal 104 may affect another QAM signal due to XPM effect. 106 In current DWDM system with different bit rates, general advice is to 107 group the channels with the same bit rates into the same spectrum 108 sub-band to avoid the detrimental XPM effect. 110 Except the advantage described above, grouping of channels with the 111 same bitrates will help reduce fragment in flexible grid network. 112 Two kinds of DWDM application is described in the newest version of 113 [G.694.1], one is fixed grid, and the other is flexible grid. Fixed 114 grid is the traditional DWDM application with fixed channel slot 115 width (e.g., 50GHz) which has been deployed in large scale in the 116 network and flexible grid is a new kind of DWDM application with 117 different channel slot widths which can be used to transport large 118 bandwidth data. The flexible grid technology is also a DWDM 119 application which is different from fixed grid application. Flexible 120 grid is a kind of new DWDM application with different channel slot 121 width (e.g., 50GHz, 87.5GHz etc). Signals with different bit rates 122 may occupy different slot widths and use different modulation format. 123 Grouping of signals with the same bit rates into the same spectrum 124 may also be a better choice than completely freedom positioning. 126 Frequently setup and release of flexible grid optical channels which 127 occupy different slot widths would result in the spectrum fragments 128 that can't be used anymore, and this will cause the decline of 129 spectrum utilization rate. Global Concurrent Optimization (GCO), 130 which combines with the implementation of the stateful PCE, can be 131 used for defragmentation and raise spectrum utilization rate. But 132 it's complicated to apply the GCO in current network, because this 133 will involve a large scale of resources and computation. Another 134 method that can be used is to group the channels with the same bit 135 rates into the same spectrum sub-band and this is also a feasible 136 solution to help raise spectrum utilization rate. 138 According to the previous description, grouping of channels with the 139 same bit rates maybe a good choice to reduce the XPM effect and raise 140 spectrum utilization rate, especially in network with different slot 141 widths. So in order to take the grouping into consideration during 142 the path computation, a sub-band spectrum of the available spectrum 143 SHOULD be allocated in advance and this spectrum allocation 144 information SHOULD be known by path computation element when compute 145 the path. This document mainly addresses the routing protocol 146 extension to support the advertisement of the spectrum allocation 147 information. Policy may be used by operator when split spectrum 148 supported on a link into several sub-bands. One spectrum sub-band 149 can only be used for path (optical channel) setup with specific 150 attributes, for example, with specific bitrates and/or modulation 151 format. 153 2. Conventions used in this document 155 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 156 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 157 document are to be interpreted as described in [RFC2119]. 159 3. Overview of the Solution 161 In current DWDM system with different bit rates, general advice is to 162 group the channels with the same bit rates and modulation format into 163 the same spectrum sub-band to avoid the detrimental XPM effect. As 164 signals of the same bitrates usually use the same modulation format 165 on a specific link, this document mainly pays attention to grouping 166 of channels with the same bitrates. Figure 1 shows an example, in 167 which part of the spectrum frequency slots (i.e., the left sub-band) 168 are allocated to 10 Gbit/s channels while another part of the 169 frequency slots (i.e., the right sub-band) are allocated to 100 170 Gbit/s channels. Currently an NRZ modulation format is employed for 171 10 Gbit/s channels, while 40 Gbit/s and/or 100 Gbit/s channels are 172 mostly phase-modulated (e.g. xPSK) signals. As noted above it is 173 common practice to keep an appropriate guard band between channels 174 with different bit rates and/or modulation format to minimize 175 nonlinear effects induced signal degradations and to group channels 176 with the same bit rate and modulation format. 178 10G OCh 50GHz 10G OCh 50GHz 179 +---+---+---+---+---+ +---+---+---+---+---+ 180 | | | | | | guard band | | | | | | 181 __|___|___|___|___|___|____________|___|___|___|___|___|____ 182 193.025 197.025 183 193.075 196.975 185 Figure 1: Group of Channels 187 [Notes: According to the simulation results about grouped spectrum 188 allocation and ungrouped spectrum allocation for 100Gbit/s and 189 400Gbit/s transmissions are carried. A grouped spectrum allocation 190 only resulted in a small improvement (about 0.2 and 0.5 dB) compared 191 to ungrouped spectrum allocation for 100G and 400G data transmissions 192 respectively. The penalty induced by mixed QPSK and 16QAM signals 193 seems to be much smaller than in a QPSK and NRZ hybrid system. This 194 may be explained by the similar spectrum of the QPSK and 16QAM 195 formats for the same baud rate. These results seem to indicate that 196 systems operated with only phase modulated signals may show 197 significantly lower impairments compared to systems operated with a 198 mix of NRZ and phase modulated signals.] 200 [Note: we are not sure if grouping of channels with the same bit rate 201 is needed in future. According to the discussion in ITU-T, a part of 202 the experts express that: we should use grouping of channels with the 203 same bit rate in the short term, however, in the long term, it may be 204 forced to use indiscriminate positioning of the spectrum.] 206 Some other advantages are also brought if operator split available 207 spectrum into several sub-bands and one spectrum sub-band can only be 208 used for optical channel setup with the same bit rate. A spectrum 209 sub-band which can only be used for optical channel setup with the 210 same bit rate will help reduce fragments. Channels in the same 211 spectrum group sub-band with the same bitrates looks almost like 212 fixed grid technology with the same slot width, and they won't 213 generate fragments in the process of path setup and release. It may 214 also be convenient for operator to manage the network if the operator 215 groups the optical channel with the same bit rate. 217 When control plane uses path computation element to setup an end-to- 218 end path through the DWDM network, spectrum available information and 219 restriction information (e.g., spectrum partition information) should 220 be taken into consideration in order to compute a suitable end-to-end 221 path. The spectrum sub-band information needs to be advertised by 222 routing protocol in order to help the path computation. Section 4 223 describes the extension of OSPF routing protocol to advertise these 224 spectrum sub-band information in order to help path computation. 226 4. Extension of routing protocol 228 4.1. Relationship with WSON 230 WSON related work can be re-used in this document to advertise the 231 spectrum group information. This Section addresses the routing 232 extension work of the features which is describe in the previous 233 section base on the current WSON work in IETF CCAMP Group. In the 234 document [draft-ietf-ccamp-general-constraint-encode], a new link 235 sub-TLV called Port Label Restrictions sub-TLV is defined. 236 Descriptions about Port Label Restrictions sub-TLV in the draft 237 [draft-ietf-ccamp-gmpls-general-constraints-ospf-te] are introduced 238 here: "Port label restrictions describe the label restrictions that 239 the network element (node) and link may impose on a port. These 240 restrictions represent what labels may or may not be used on a link 241 and are intended to be relatively static. More dynamic information 242 is contained in the information on available labels. Port label 243 restrictions are specified relative to the port in general or to a 244 specific connectivity matrix for increased modeling flexibility" and 245 "For example, Port Label Restrictions describes the wavelength 246 restrictions that the link and various optical devices such as OXCs, 247 ROADMs, and waveband multiplexers may impose on a port in WSON". 249 According to the previous description, the restrictions information 250 carried in the port label restriction sub-TLV are used to represent 251 what wavelength/spectrum may or may not be used on a link and are 252 relatively static. The spectrum group allocation information 253 described in this document can be regarded as label restrictions 254 which are imposed by network element (node) on a port, and the 255 network element include various optical devices such as OXCs, ROADMs 256 and waveband multiplexers and so on. These spectrum sub-bands 257 restrictions represent the spectrum allocation information and a 258 spectrum sub-band can only be used for channels setup with specific 259 bitrates and/or modulation format. This restriction is relative 260 static and can be carried in Port Label Restrictions sub-TLV. 262 4.2. Extensions of OSPF Protocol to Support Spectrum Group Allocation 264 Spectrum sub-band allocation information should be known by path 265 computation element if operators want to compute an end-to-end 266 optical channel path. As described in the previous section, Port 267 Label Restrictions sub-TLV can be used to carry this spectrum sub- 268 band allocation restriction information. Figure 1 is the format of 269 Port Label Restrictions sub-TLV which is described in 270 [draft-ietf-ccamp-general-constraint-encode] and definition of the 271 parameters included in this sub-TLV can be found in this document. 273 0 1 2 3 274 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 1 275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 276 | MatrixID |RestrictionType| Reserved/Parameter | 277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 278 | | 279 : Additional Restriction Parameters per RestrictionType : 280 | | 281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 283 Figure 2: Port Label Restrictions sub-TLV 285 4.2.1. Spectrum sub-band Allocation by Bitrates 287 As described in section 3, channels on a single fiber with the same 288 bitrates usually use the same modulation format, especially when the 289 equipments come from one vendor. So here operator can split spectrum 290 into several spectrum sub-bands by bitrates. In this section, OSPF 291 protocol is extended to cover the spectrum sub-bands allocation 292 information by bitrates. 294 The spectrum sub-bands allocation information by bitrates is needed 295 in the process of path computation if an end-to-end path needs to be 296 computed by path computation element and this information SHOULD be 297 advertised by routing protocols. Figure 3 gives a new kinds of Port 298 Label Restrictions sub-TLV which mainly extent the Additional 299 Restriction Parameters field to cover the spectrum sub-bands 300 allocation information. The parameters in the Additional Restriction 301 Parameters field include Bit Rate which indicates the bitrates of the 302 specific spectrum sub-bands and spectrum boundaries information of 303 the sub-band. 305 0 1 2 3 306 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 1 307 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 308 | MatrixID |RestrictionType| Reserved | 309 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 310 | Bit Rate | 311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 312 : Spectrum Sub-band Range : 313 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 315 Figure 3 317 Definition of MatrixID and RestrictionType field can be found in the 318 document [draft-ietf-ccamp-general-constraint-encode]. Value of 319 RestrictionType needs to be assigned by IANA. 321 [Note: As several routing documents exist in the CCAMP and the 322 label_set object encoding is not determined, this document use 323 "spectrum sub-band range" to represent spectrum allocation 324 information temporarily.] 326 "Bit Rate" field indicates the bitrates of the specific spectrum sub- 327 band. 329 In some situation, modulation format information may also be needed 330 to help allocation wavelength range, as signals with the same 331 bitrates on a single fiber can use different modulation format. In 332 this case, modulation formats information is needed to be carried in 333 Port Label Restrictions sub-TLV. Wavelength that is supported by 334 subsystems can be partitioned to service traditional fixed grid 335 technology. 337 5. Security Considerations 339 TBD 341 6. IANA considerations 343 TBD. 345 7. References 347 7.1. Normative References 349 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 350 Requirement Levels", BCP 14, RFC 2119, March 1997. 352 [RFC6163] Lee, Y., Bernstein, G., and W. Imajuku, "Framework for 353 GMPLS and Path Computation Element (PCE) Control of 354 Wavelength Switched Optical Networks (WSONs)", RFC 6163, 355 April 2011. 357 7.2. Informative References 359 [Cross Phase Modulation] 360 International Journal of Electronics and Computer Science 361 Engineering, "Effect on WDM due to Cross Phase 362 Modulation". 364 [G.694.1 v1] 365 International Telecommunications Union, "Draft revised 366 G.694.1 version 1.3". 368 [WD6-12] International Telecommunications Union, "Discussion on 369 progressing Q.6/15's work on DWDM applications using 370 flexible grid". 372 [flexible-grid-ospf-ext] 373 Fatai Zhang, Xiaobing Zi, Ramon Casellas, O. Gonzalez de 374 Dios, and D. Ceccarelli, "GMPLS OSPF-TE Extensions in 375 support of Flexible-Grid in DWDM Networks", 376 draft-zhang-ccamp-flexible-grid-ospf-ext-00.txt . 378 [flexigrid-lambda-label] 379 D. King, A. Farrel, Y. Li, F. Zhang, and R. Casellas, 380 "Generalized Labels for the Flexi-Grid in Lambda-Switch- 381 Capable (LSC) Label Switching Routers", 382 draft-farrkingel-ccamp-flexigrid-lambda-label-01.txt . 384 [super-channel-label] 385 Iftekhar Hussain, Abinder Dhillon, Zhong Pan, Marco Sosa 386 and Bert Basch, Steve Liu, Andrew G. Malis, "Generalized 387 Label for Super-Channel Assignment on Flexible Grid", 388 draft-hussain-ccamp-super-channel-label-02.txt . 390 Authors' Addresses 392 Qilei Wang 393 ZTE Corporation 395 Email: wang.qilei@zte.com.cn 397 Xihua Fu 398 ZTE Corporation 399 ZTE Plaza, No.10, Tangyan South Road, Gaoxin District 400 Xi'an 210012 401 P.R.China 403 Email: fu.xihua@zte.com.cn