Internet DRAFT - draft-zhangj-ccamp-flexi-grid-ospf-te-ext

draft-zhangj-ccamp-flexi-grid-ospf-te-ext






Network Working Group                                           J. Zhang
Internet-Draft                                                  YL. Zhao
Intended status: Informational                                    ZY. Yu
Expires: April 21, 2013                                             BUPT
                                                                 XF. Lin
                                                                DJ. Wang
                                                                  XH. Fu
                                                         ZTE Corporation
                                                        October 18, 2012


   OSPF-TE Protocol Extension for Constraint-aware RSA in Flexi-Grid
                                Networks
              draft-zhangj-ccamp-flexi-grid-ospf-te-ext-02

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
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   This Internet-Draft will expire on April 21, 2013.

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



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
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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
     4.5.  Modulation level Information . . . . . . . . . . . . . . .  6
   5.  OSPF-TE Protocol Extension . . . . . . . . . . . . . . . . . .  6
     5.1.  Consecutive Spectrum Slots Weight Sub-TLV  . . . . . . . .  7
     5.2.  Spectrum Compactne Sub-TLV . . . . . . . . . . . . . . . .  8
   6.  Super-Channel Label Encoding Format with GB  . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 10
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10






















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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




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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.





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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].




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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.

4.5.  Modulation level Information

   Based on OFDM, diferent modulation formats could be selected based on
   the distance to serve different connections, since the physical
   impairments will have high probability to degrade the quality of
   connection requests with low-level modulation format such as OOK if
   the distance of the connection request is very long.

   Supposing there is a scenario, the number of a connection' hops is
   very huge, and in some of the connection' link, there is not enough
   spectrum resource to serve the connection if use low-level format.
   Bandwidth resizing method can be used to solve this scenario.
   Bandwidth resizing method is that changing the modulation format in
   the middle node of a connection since every network node in the
   flexible grids networks based on OFDM technology which has the
   ability of choosing different modulation formats, which means several
   different modulation formats could be choose in different links for a
   connection in the flexible grids networks.  So it requests that the
   modulation formats of every links of a connection should be
   advertised.


5.  OSPF-TE Protocol Extension

   In this section, we define the enhancements to the Traffic



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   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
   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:










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        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.

   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.




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   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.


             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.  |       MF      |R|
           +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           | 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

   MF: To show the Modulation Formates that the flexible grids networks
   support, we add an eight bit information of MF fields.

   R: Reserved(1-bit)




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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
              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.











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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/


   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/







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   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/































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