Network Working Group J. Zhang Internet-Draft YL. Zhao Intended status: Informational ZY. Yu Expires: October 27, 2012 BUPT XF. Lin DJ. Wang XH. Fu ZTE Corporation April 25, 2012 OSPF-TE Protocol Extension for Constraint-aware RSA in Flexi-Grid Networks draft-zhangj-ccamp-flexi-grid-ospf-te-ext-01 Abstract ITU-T Study Group 15 has introduced a new flexible grids technology of DWDM network which is an effective solution to improve the efficiency of spectrum resource utilization. This memo extends the OSPF-TE protocol to support constraint-aware routing and spectrum assignment (RSA) in flexi-grid networks. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on October 27, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of Zhang, et al. Expires October 27, 2012 [Page 1] Internet-Draft Routing extension for C-RSA April 2012 publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 3. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Motivation for Routing Protocol Extension . . . . . . . . . . 4 4.1. Constraints Considerations for RSA . . . . . . . . . . . . 4 4.2. Consecutive Spectrum Slots Information . . . . . . . . . . 5 4.3. Spectrum Compactness . . . . . . . . . . . . . . . . . . . 5 4.4. Variable Guard Band Information . . . . . . . . . . . . . 6 5. OSPF-TE Protocol Extension . . . . . . . . . . . . . . . . . . 6 5.1. Consecutive Spectrum Slots Weight Sub-TLV . . . . . . . . 6 5.2. Spectrum Compactne Sub-TLV . . . . . . . . . . . . . . . . 7 6. Super-Channel Label Encoding Format with GB . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Zhang, et al. Expires October 27, 2012 [Page 2] Internet-Draft Routing extension for C-RSA April 2012 1. Introduction To enable the dynamic and effective allocation of spectrum resource based on the demand of the client LSP's requests, the latest revision of ITU-T Recommendation [G.694.1] has introduced a flexible grid technique in DWDM optical networks. The flexible grid has a finer granularity (i.e. according to the definition of flexible grid in [G.694.1], the data channel can be selected on a channel spacing of 6.25 GHz with a variable slot width measured in units of 12.5 GHz) for the spectrum slot. In the dynamic flexi-grid networks, except for selecting an appropriate route for the client LSP, the appropriate width of spectrum slot is also needed to choose and assigned to the client LSP. The spectrum bandwidth assigned to the client LSP is made up of an appropriate number of consecutive spectrum slots from end-to-end, which is determined by the used modulation format, according to the client LSPs data rate requests and physical constraints of the selected path. Compared with ITU-T fix-grid optical network some extra constraints need to be considered when running the routing and spectrum resource assignment (RSA) in flexi-grid networks. In this memo two of those constraints (other constraints are left for future considered) that are necessary for RSA are discussed in detail in flexi-grid networks, and Spectrum Compactness is introduced .and then the extension of OSPF-TE protocol for these constraints related to RSA in flexi-grid networks is described and also the the value of super-channel bitmap member. 2. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Terminologies CSSW: Consecutive spectrum slots weight GB: Guard band RSA: Routing and spectrum assignment WSON: Wavelength switched optical networks Zhang, et al. Expires October 27, 2012 [Page 3] Internet-Draft Routing extension for C-RSA April 2012 4. Motivation for Routing Protocol Extension In this section we introduce the RSA constraints and the motivation of routing protocol extension for of flexi-grid networks 4.1. Constraints Considerations for RSA When processing RSA in flexi-grid networks, the constraints information (such as the information of spectrum bandwidth in a network link and so on.) are necessary for computing and selecting an appropriate backup route and a certain number of consecutive spectrum slots for the client LSPs effectively. Some of the necessary constraints are listed as follows: o Spectral consecutiveness constraint o Variable guard band constraint o Spectral continuity constraint o Impairments constraint o Other constraints All the constraints can generate important impacts for the performance of the client LSPs, even for the entire network. The first two constraints are mainly talked about in this memeo. Just like the wavelength continuity constraint in WSON, the spectral continuity constraint means allocation of the same spectrum slots on each link along a path because not all of the nodes in optical networks have the ability of wavelength conversion. The degradation of the optical signals due to impairments that accumulate along the path (without 3R regeneration), can result in unacceptable bit error rates or even a complete failure to demodulate and/or detect the received signal[draft-ietf-ccamp-wson-impairments-07]. So it is necessary to consider about the impairments constraint within flexi-grid networks. The impairments constraint in flexi-grid networks will be studied in future in this memo. Also, there may be some other constraints for RSA, other than the four kinds above, such as the modulation levels constraint, which are left for future researching. Zhang, et al. Expires October 27, 2012 [Page 4] Internet-Draft Routing extension for C-RSA April 2012 4.2. Consecutive Spectrum Slots Information The spectral consecutiveness constraint is that the allocated spectrum slots must be chosen from consecutive spectrum slots in the spectrum space on each link of flexi-grid networks. Compared with the technology of WSON, the number of spectrum slots in flexi-grid networks will be much larger than the number of wavelength in WSON. After a long running time, the situation of available spectrum slots will be much complex, especially the situation of the available consecutive spectrum slots. After selecting a route, the appropriate consecutive spectrum slots need to be assigned for the client LSP. When we choose one of the backup routes for the client LSP without considering the situation about the available consecutive spectrum slots information, the route may have no enough consecutive spectrum slots which means that the selected route have no available resource for the LSP's request, and then the client LSP will be rejected or trigger another path computation process which will increase the blocking rate of the network or increase network resources consumed by communication and computing of new route. When computing a route with the knowledge of the consecutive spectrum slots information of the network link (for example, the number of ten available consecutive spectrum slots in a network link, or the number of twenty available consecutive spectrum slots in a network link.), it will be very useful to select a better route which has higher probability of enough available consecutive spectrum slots for the client LSP. And this will improve the success rate of setting up new client LSPs. 4.3. Spectrum Compactness With a new client LSP arriving, a path connection needs to be establish and proper consecutive of spectral resource needs to be assigned to this LSP. With the LSP ending, the path connection is released, and the spectral resource could be assigned for new LSP. In a dynamic traffic scenario, this setup and tear down process leads to fragmentation of spectrum resources Note that the probability of using these pieces of fragmentations is very low since they are not consecutive. If united together, e.g. one block, they could be used for new LSP. This process is named defragmentation, which aim to improve the utilization of spectrum resource. In order to make the defragmentation more effective, the occupation of spectrum in a link or in the network is needed to be better known, Spectrum Compactness is proposed[OFC2012 JTh2A.35]. Zhang, et al. Expires October 27, 2012 [Page 5] Internet-Draft Routing extension for C-RSA April 2012 4.4. Variable Guard Band Information Some spectrum slots need to be reserved as Guard Band(GB) between two adjacent client LSPs to avoid bad impact of non-linear impairments and other network elements. Since the granularity of the flexi-grid networks will be very small, the spectrum interval, i.e., GB need to be considered more carefully to avoid poor quality impact of the adjacent client LSPs. Which means with the changing of network environment and the operating of the network, the bandwidth of the GB also need to change. In flexi-grid networks, with the increasing of the total transportation power and the smaller of the channel space, the channel crosstalk that results from non-linear effects will become the important factor that affects the performance of the network. The impact between two adjacency client LSPs may be changing based on the change of crosstalk and other changes of network. With the changing of those parameters, the interferences between two adjacency client LSPs may be increasing, if the Guard Band is fixed, the quality of the adjacent client LSPs and also the network's will be decreased. If the GB can be varied based on the network environment changing, then the bad impact can be avoided. 5. OSPF-TE Protocol Extension In this section, we define the enhancements to the Traffic Engineering (TE) properties of flexi-grid networks' TE links that can be announced in OSPF-TE LSAs. The TE LSA, which is an opaque 10 LSA with area flooding scope [RFC3630], has only one top-level and has one or more nested sub-TLVs for extensibility. [RFC3630] also defines two top Type/Length/Value (TLV) triplet to support traffic engineering of OSPF, i.e. (1) Router Address TLV and (2) Link TLV. In this memo, we enhance the sub-TLVs for the Link TLV in support of flexi-grid networks. Specifically, we add the following sub-TLVs to the Link TLV: o Consecutive spectrum slots weight sub-TLV o Spectrum Compactne sub-TLV 5.1. Consecutive Spectrum Slots Weight Sub-TLV In distribution networks, we propose the CSSW as a sub-TLV of OSPF-TE Link TLV which represents the situation of the available consecutive spectrum slots in a link of the flexi-grid networks for example the percentage of the total bandwidth of the number of five consecutive Zhang, et al. Expires October 27, 2012 [Page 6] Internet-Draft Routing extension for C-RSA April 2012 spectrum slots, the percentage of the total bandwidth of the number of ten consecutive spectrum slots ... ). With knowing the weight of available consecutive spectrum slots in a link, the spectrum resource assignment in the flexi-grid networks can be working more efficiently in a distributed network. slot num 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 slot status||||||||| |||| | | ||||||| | | | | | | | | | | The figure above shows a link's spectrum status.Assume there are 20 slots on a link, and slot 0, slot 1, slot 2, slot 4, slot 8 and slot 9 are occpuded by three requests. The number of five consecutive spectrum slots is 6, they are (11~15), (12~16), (13~17), (14~18), (15~19). The number of ten consecutive spectrum slots is 1, and it is from slot 10 to slot 10,i.e., (10~19). The number of Spectrum Joint is 10. The format of the CSSW sub-TLV is as follows: 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = TBD | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | method| Reserve | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value : Consecutive Spectrum Slots Weight | // // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: TBD. The Type of CSSW sub-TLV is left for future to define. Length: Variable. The length of CSSW sub-TLV is based on its define of the value which is variable based on different implementation ways. method: the method to describe the status of consecutive spectrum. Value: Based on the description method of the status of consecutive spectrum. The content of the CSSW sub-TLV is left for future researching. 5.2. Spectrum Compactne Sub-TLV The Spectrum Compactne sub-TLV based Defragmentation scheme which indicates the occupation of spectrum in a link or in the network. Zhang, et al. Expires October 27, 2012 [Page 7] Internet-Draft Routing extension for C-RSA April 2012 The format of the GB sub-TLV is as follows: 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Method| Value: Spectrum Compactne | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: TBD. The Type of Spectrum Compactne sub-TLV is left for future to define. Length: TBD. The length of Spectrum Compactne sub-TLV is based on the define of the value of it. Method: Represents different evaluation methods of Spectrum Compactne. Value: Based on the method of Spectrum Compactne evaluation. The different evaluation methods of Spectrum Compactne are left for future researching. 6. Super-Channel Label Encoding Format with GB As discussed in [draft-hussain-ccamp-super-channel-label-03], the Super-Channel is proposed to support flexi-grid networks. In this memo, we extend the Super-Channel Label Encoding Format by considering the Guard Band information. Zhang, et al. Expires October 27, 2012 [Page 8] Internet-Draft Routing extension for C-RSA April 2012 0 1 2 3 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Super-Channel Id (16-bit) |Grid | S.S. | Reserved (9-bit)| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | n_start of Grid (16-bit) |Num of Slices in Grid (16-bit) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Bitmap Word #1(first set of 32 slices from the left most edge) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Bitmap Word #2 (next set of 32 contiguous slice numbers) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Bitmap Word #N(last set of 32 contiguous slice numbers) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The above figure shows an encoding Format of Super-Channel Label, all the fine-detail information can be accessed in [draft-hussain-ccamp-super-channel-label-03], but to consider about the Guard Band information, the meaning of the bitmap value is changed: 0 -- reprents that slice reservation is not required 1 -- reprents that slice reservation is required 2 -- reprents that slice is required by Guard Band 7. Security Considerations TBD. 8. Acknowledgments TBD. 9. References 9.1. Normative References [OFC2012JTh2A.35] Yu, X., Zhang, J., Zhao, Y., Peng, T., Bai, Y., Wang, D., and X. Lin, "Spectrum Compactness based Defragmentation in Flexible Bandwidth Optical Networks", RFC 3630, September 2003. [RFC2119] Bradner, S., "Key words for use in RFC's to Indicate Zhang, et al. Expires October 27, 2012 [Page 9] Internet-Draft Routing extension for C-RSA April 2012 Requirement Levels", RFC 2119, March 1997. [RFC2328] Moy, J., "OSPF Version 2", RFC 2328, April 1998. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. 9.2. Informative References [draft-hussain-ccamp-super-channel-label-03] Hussain, I., Dhillon, A., Pan, Z., Sosa, M., Basch, B., Liu, S., and A. G. Malis, "Generalized Label for Super- Channel Assignment on Flexible Grid", March 2012. [draft-ietf-ccamp-wson-impairments-07] Lee, Y., Bernstein, G., Li, D., and G. Martinelli, "A Framework for the Control of Wavelength Switched Optical Networks (WSON) with Impairments", July 2011. Authors' Addresses Jie Zhang BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8613911060930 Email: lgr24@bupt.edu.cn URI: http://www.bupt.edu.cn/ Yongli Zhao BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8613811761857 Email: yonglizhao@bupt.edu.cn URI: http://www.bupt.edu.cn/ Zhang, et al. Expires October 27, 2012 [Page 10] Internet-Draft Routing extension for C-RSA April 2012 Ziyan Yu BUPT No.10,Xitucheng Road,Haidian District Beijing 100876 P.R.China Phone: +8615116984347 Email: yzhziyan@gmail.com URI: http://www.bupt.edu.cn/ Xuefeng Lin ZTE Corporation No.16,Huayuan Road,Haidian District Beijing 100191 P.R.China Phone: +8615901011821 Email: lin.xuefeng@zte.com.cn URI: http://www.zte.com.cn/ Dajiang Wang ZTE Corporation No.16,Huayuan Road,Haidian District Beijing 100191 P.R.China Phone: +8613811795408 Email: wang.dajiang@zte.com.cn URI: http://www.zte.com.cn/ Xihua Fu ZTE Corporation West District,ZTE Plaza,No.10,Tangyan South Road,Gaoxin District Xi'an 710065 P.R.China Phone: +8613798412242 Email: fu.xihua@zte.com.cn URI: http://www.zte.com.cn/ Zhang, et al. Expires October 27, 2012 [Page 11]