A Framework for control of Flex Grid Networks
draft-syed-ccamp-flexgrid-framework-ext-00

Network Working Group
                                                        Sharfuddin Syed
                                                              Rajan Rao
                                                             Marco Sosa
                                                                Biao Lu
Internet Draft                                                 Infinera
Intended status: Standard Track                           March 5, 2012
Expires: Sept 04 2012

               A Framework for control of Flex Grid Networks
              draft-syed-ccamp-flexgrid-framework-ext-00.txt

Abstract

   This document provides a framework for applying GMPLS architecture
   and protocols to Flex Grid.

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Copyright Notice

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Table of Contents

   1. Introduction...................................................2
   2. Terminology....................................................3
   3. Acronyms.......................................................3
   4. Requirements and constraints...................................4
   5. Use cases......................................................6
   6. Protocol Implications..........................................9
   7. Security Considerations........................................9
   8. IANA Considerations............................................9
   9. References.....................................................9
      9.1. Normative References......................................9
      9.2. Informative References....................................9
   10. Acknowledgments ..............................................10

1. Introduction

   To enable scaling of existing transport systems to ultrahigh data
   rates of 1 Tbps and beyond, next generation systems providing super-
   channel switching capability are currently being developed. To allow
   efficient allocation of optical spectral bandwidth for such high bit
   rate systems, International Telecommunication Union
   Telecommunication Standardization Sector (ITU-T) is extending the
   G.694.1 grid standard (termed ''Fixed-Grid'') to include flexible grid
   (termed ''Flex-Grid'') support.

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2. Terminology

   A. Frequency Slot:
          The frequency range allocated to a slot [FLEX-GRID]
          It is a contiguous portion of the spectrum available for
          optical passband filter.
   B. Spectral Slice:
          Refers to a minimum granularity of a frequency slot (e.g.
          12.5GHz).
   C. Slot width:
          The full width of a frequency slot in a flexible grid[FLEX-
          GRID].
          The slot width is equal to number of spectral slices in the
          slot times the width of spectral slice.
   D. Super-channel:
          Super-channel is a collection of one or more frequency slots
          to be treated as unified entity for management and control
          plane (Ref to figure-1).
   E. Contiguous Spectrum Super-channel:
          Contiguous spectrum super-channel is a super-channel with a
          single frequency slot (Ref to figure-1).
   F.           Split-Spectrum super-channel:
          Split-Spectrum super-channel is a super-channel with multiple
          frequency slots.
          Each frequency slot will be allocated an independent passband
          filter, irrespective of whether frequency slots are adjacent
          or not.

    Figure 1 Super-Channel (Refer to pdf version [5] of this draft for figures)

3. Acronyms

   OCG: Optical Carrier Group

   SCH: Super Channel

   OCH: Optical Channel

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   OCC: Optical Channel Carrier

   OTUk: Optical channel Transport Unit level k

   ODUk: Optical channel Data Unit Level k

   ODUj: Optical channel Data Unit Level j

4. Requirements and constraints

   This section covers the high level requirements for the support of
   super-channels over Flex-Grid Infrastructure. Specifically, the
   scope of requirements and constraints listed in this section covers
   the functionality that shall be supported by the control plane sub-
   system. The Features are listed as list of Requirements Tagged as
   Rn, for better traceability and coverage in other related drafts
   and/or for references by other related standards across other
   standard bodies.

   R1: Flexible size of super-channel

   The protocol shall allow the super-channels on the Flex-Grid to be
   of different size/width. The number of slices and the granularity of
   each slice shall be flexible.

   R2: Flexible mapping of super-channel

   The super-channels shall be allowed to be mapped to any spectrum
   location in the ITU Grid.

   The frequency slots allocation of super-channels on the ITU-Grid
   shall confirm to [FLEX GRID]

   R3: Contiguous Spectrum and Split Spectrum super-channel

   The protocol shall allow the use of super-channels which can be
   contiguous or non-contiguous.

   Example: consider a system supporting 500GHz super-channel.

   In case of contiguous spectrum, the super-channel is allocated with
   40 slices of 12.5GHz granularity. This super-channel is placed
   directly on the Flex-Grid at any location.

   In case of split spectrum, the super-channel is divided into
   multiple members. Considering the same example scenario, the 500GHz

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   super-channel can be divided into 2 member split spectrum channels.
   Each member is allocated a different flexible location on the Flex-
   Grid. Each frequency slot can be 250GHz, 20x12.5GHz slices allocated
   for frequency slot.

   R4: Co-routing of split-spectrum super-channel

     The protocol shall support the co-routing of frequency slots
     within the split-spectrum super-channels.

     Please refer to the Figure 5 and Use Case 3, depicting the co-
     routing of split-spectrum super-channels.

   R5: Flexible Modulation Formats for different super-channels on the
   same Flex-Grid

   Each super-channel mapped on to the Flex-Grid system shall have the
   capability to carry mixed modulation signals.

   R6: Fixed vs Flexible Grid super-channel interworking

   The Control Plane protocol shall handle nodes which support flex-
   grid functionality in addition to nodes that only support fixed grid
   functionality.

   This requirement is to enable introduction of flex-grid systems into
   existing fixed-grid network. This can also be used to deploy flex-
   grid system in certain segments of the network. Please also refer
   use case section of this document.

   R7: Support for the CDC based super-channels over Flex-Grid

   The super-channel over the Flex-Grid control plane frame work shall
   support CDC (Connectionless, Directionless and Contentionless)
   architecture. Further, flexibility of control shall be provided,
   such that, depending on deployment scenarios and application, a sub-
   set of CDC features are used on a given network segment. Hence, each
   type of ROADMs shall be supported.

   R8: Directionless/Contentionless super-channels

   The protocol shall allow for routing the super-channels in different
   fiber directions/degrees, based on the following criteria:

   a) Based on spectral slices
   b) Based on fibers/nodes

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   The super-channels with the same frequency slot mapping are not
   allowed to be provisioned over a given fiber direction.

   Please refer to the Figure 5 and Use Case 3, depicting the handling
   of same super-channel at a CDC node.

   R9: Resizing of super-channel bandwidth

   Depending on the spectral bandwidth changes, the protocol shall
   allow super-channels resizing.

   R10: super-channel LSP restoration

   The system shall support the super-channel based LSP restoration
   feature where the restored path is computed dynamically. During the
   restoration process, it shall be possible for the system to pick
   different frequency slots of super-channel, keeping the number and
   size of slices the same. Further, options for LSP restoration with
   pre-computed path (with or without resource reservation) shall be
   supported. Revertive and Non-Revertive restoration options shall be
   provided.

   R11: Embedded Control Channel for super-channel routing and
   signaling

   The system shall continue to use the standard mechanism for ECC
   defined in [ref: OSC based control channel], for OAM features
   required to be supported between network elements deploying super-
   channel over Flex-Grid.

   R12: Management Plane and Control Plane feature interaction for
   super-channel

   The system shall keep track of important bandwidth related
   parameters for the Flex-Grid based system. Important parameters
   include (but not limited to):

   a) Available Spectral Slices
   b) Provisioned super-channels along with provisioned spectral-slices

5. Use cases

   The use cases described in this section are for information only.
   The OTN hierarchy described in this section is sure to be discussed
   in ITU SG-15 Q6 & Q14. Within the scope of this frame-work document,
   the main focus is super-channel entity. The remaining layers are
   described to illustrate the relationship with the digital layers.

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   With respect to the mapping hierarchy in the OTN layers, multiple
   OCHs are mapped to the SCH, and multiple OCCs (Optical Channel
   Carriers) are mapped to an OCH. This hierarchy is depicted in Figure
   2 below. Specifically, the following flexibility of number of
   instances that are mapped between the layers shall be supported.

   X number of OCC mapped to OCH

   Y number of OCH mapped to SCH

   Z number of SCH mapped to OCG

 Figure 2 Super-Channel mapping to OTN hierarchy ((Refer to pdf version [5] of this
                            draft for figures)

   Example Use Case 1: Super-Channel with multiple OCHs and multiple
   carriers per OCHs.

   The following Figure 3 gives an example use case where multiple OCH
   are carrier over a single SCH. Please note that this is an example
   use case only. In general, the system shall be capable of supporting
   flexible mapping where there is flexible number of carriers mapped
   into an OCH and a flexible number of OCHs mapped to a single Super-
   Channel.

         Figure 3 Super-Channel use case showing multiple OCH and multiple carriers
per OCH(Refer to pdf version [5] of this draft for figures)

   Example Use Case 2:

   The following Figure 4 shows the case where multiple OCHs are
   carried over separate super-channels. These separate super-channel
   use case is used to realize the split-spectrum super-channel
   implementations. Further, these split-spectrum based super-channels
   can be co-routed together or can be diversely routed in the network.

Figure 4: Split-Spectrum Super-Channel use case showing multiple OCH and multiple
carriers per OCH (Refer to pdf version [5] of this draft for figures)

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   Example Use Case 3: Network Level Use Case of super-channel

   A network level diagram to illustrate the use of CDC based super-
   channel (contiguous spectrum and split-spectrum) is shown in Figure
   5 below. In this scenario, N1 and N2 are digital/TDM nodes, where
   the client services originate. N2, N3, N4 and N5 are Optical/WDM
   nodes on which the super-channels are provisioned. Node N2 is CDC
   ROADM and Nodes N3, N4 and N5 are Colorless ROADMs only.

   Four super-channels are provisioned in this example network. Super-
   Channels S1 are contiguous spectrum super-channels, both using the
   same frequency slots, and are added/dropped at Node N2. The
   contention for the same super-channel (with exactly the same
   frequency slot mapping) is avoided by routing these super-channels
   in different degrees of the network. Alternatively, if these super-
   channels have to go through the same fiber path, then the frequency
   slots occupied on the Flex-Grid shall be different.

   Super-channels S2-1 and S2-2 illustrates the split-spectrum super-
   channel that is co-routed over the same fibers in the network.
   Super-channels S3-1 and S3-2 illustrates the split-spectrum super-
   channel that is diversely routed through Node N3 and Node N4.

    Figure 5: Super-Channel Network Level use case (Refer to pdf version [5] of this
                              draft for figures)

   Example Use Case 4: Fixed and Flexible Grid Interworking

    - In Figure 6:
         o The Nodes N2 and N3 are Flex-Grid and Fixed grid capable
           nodes
         o The Nodes N1 and N4 are fixed grid capable nodes.
    - Fixed and Flexible support on the same interface
         o In Figure 6, this is represented by Link L3
   - BW advertisement that include both fixed and flexible grid by Flex
     Grid capable nodes
   - Signaling support for both fixed and flex-grid.

 Figure 6: Use case for fixed and flex-grid interworking (Refer to pdf version [5] of
                          this draft for figures)

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6. Protocol Implications

   Support GMPLS Routing extensions to satisfy requirements in

   Section 3.0.

   Support GMPLS Signaling extensions to satisfy requirements in
   section 3.0.

7. Security Considerations

   <Add any security considerations>

8. IANA Considerations

   IANA needs to assign a new Grid field value to represent ITU-T Flex-
   Grid.

9. References

     9.1. Normative References

   [RFC 2119]  Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

     9.2. Informative References

   [1]   ITU-T Recommendation G.694.1, "Spectral grids for WDM
         applications: DWDM frequency grid", June 2002

   [2]   [FLEX-GRID] Unpublished ITU-T Study Group-15 doc: G.694.1
         [Rev-2, 12/2011]

   [3]   [RFC 6163] Framework for GMPLS and Path Computation Element
         (PCE) Control of Wavelength Switched Optical Networks (WSONs)

   [4]   draft-ietf-ccamp-rwa-info-13.txt: Routing and Wavelength
         Assignment Information Model for Wavelength Switched Optical
         Networks

   [5]   draft-syed-ccamp-flexgrid-framework-ext.pdf -                                                          - Full version of
         this draft which contains figures.

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10. Acknowledgments

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   Authors' Addresses

   Sharfuddin Syed
   Infinera
   140 Caspian Ct., Sunnyvale, CA 94089
   Email: ssyed@infinera.com

   Rajan Rao
   Infinera
   140 Caspian Ct., Sunnyvale, CA 94089
   Email: rrao@infinera.com

   Marco Sosa
   Infinera
   140 Caspian Ct., Sunnyvale, CA 94089
   Email: msosa@infinera.com

   Biao Lu
   Infinera
   140 Caspian Ct., Sunnyvale, CA 94089
   Email: blu@infinera.com

Contributor's List

   Radhakrishna Valiveti
   Email: rvaliveti@infinera.com

   Iftekhar Hussain
   Email: IHussain@infinera.com

   Abinder Dhillon
   Email: ADhillon@infinera.com

   Mike VanLeeuwen
   Email: MVanleeuwen@infinera.com

   Ping Pan
   Email: ppan@infinera.com

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