Network Working Group J. Zhang Internet-Draft YL. Zhao Intended status: Informational ZY. Yu Expires: April 26, 2012 BUPT October 24, 2011 OSPF-TE Protocol Extension for Constraint-aware RSA in Flexi-Grid Networks draft-zhangj-ccamp-flexi-grid-ospf-te-ext-00 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 April 26, 2012. Copyright Notice Copyright (c) 2011 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 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 Zhang, et al. Expires April 26, 2012 [Page 1] Internet-Draft Routing extension for C-RSA October 2011 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 in Flexi-Grid Networks . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.2. Consecutive Spectrum Slots Information . . . . . . . . . . 5 4.3. Variable Guard Band Information . . . . . . . . . . . . . . 5 5. OSPF-TE Protocol Extension . . . . . . . . . . . . . . . . . . 6 5.1. Consecutive Spectrum Slots Weight Sub-TLV . . . . . . . . . 6 5.2. Variable Guard Band Sub-TLV . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1. Normative References . . . . . . . . . . . . . . . . . . . 8 8.2. Informative References . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 Zhang, et al. Expires April 26, 2012 [Page 2] Internet-Draft Routing extension for C-RSA October 2011 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. The routing and spectrum assignment (RSA) of flexi-grid networks need to consider some constraints. In this memo two of those constraints (other constraints are left for future considered) that are necessary for RSA are discussed in detail, and then describes the OSPF-TE protocol extension for these constraints related to RSA in flexi-grid networks. 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 April 26, 2012 [Page 3] Internet-Draft Routing extension for C-RSA October 2011 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 in Flexi-Grid Networks 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 April 26, 2012 [Page 4] Internet-Draft Routing extension for C-RSA October 2011 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. 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 Zhang, et al. Expires April 26, 2012 [Page 5] Internet-Draft Routing extension for C-RSA October 2011 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 Variable Guard Band 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 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. The format of the CSSW sub-TLV is as follows: Zhang, et al. Expires April 26, 2012 [Page 6] Internet-Draft Routing extension for C-RSA October 2011 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | 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. Value: TBD The content of the CSSW sub-TLV is left for future researching. 5.2. Variable Guard Band Sub-TLV The Guard Band sub-TLV (which is also short for GB sub-TLV) describes the spectrum interval between two client LSPs to avoid crosstalk and other network elements(such as impairment elements) that can affect the transmission performance of each client LSP. 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 = TBD | Length = TBD | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value = Variable Guard Band | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: TBD. The Type of GB sub-TLV is left for future to define. Zhang, et al. Expires April 26, 2012 [Page 7] Internet-Draft Routing extension for C-RSA October 2011 Length: TBD. The length of CSSW sub-TLV is based on the define of the value of it. Value: TBD. The content of the CSSW sub-TLV and it is left for future researching. 6. Security Considerations TBD. 7. Acknowledgments TBD. 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFC's to Indicate 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. 8.2. Informative References [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. Zhang, et al. Expires April 26, 2012 [Page 8] Internet-Draft Routing extension for C-RSA October 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/ 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/ Zhang, et al. Expires April 26, 2012 [Page 9]