Generalized Labels for the Flexi-Grid in Lambda-Switch-Capable (LSC) Label Switching Routers
draft-farrkingel-ccamp-flexigrid-lambda-label-02

Network Working Group                                      D. King (Ed.)
Internet Draft                                           A. Farrel (Ed.)
Updates: 3471, 6205 (if approved)                     Old Dog Consulting
Category: Standards Track                                    Y. Li (Ed.)
Expires: 11 Spetember 2012                                      F. Zhang
                                                                     ZTE
                                                             R. Casellas
                                                                    CTTC
                                                           11 March 2012

                Generalized Labels for the Flexi-Grid in
          Lambda-Switch-Capable (LSC) Label Switching Routers

          draft-farrkingel-ccamp-flexigrid-lambda-label-02.txt

Abstract

   A new flexible wavelength grid ("flexi-grid") is being developed
   within the ITU-T Study Group 15 to allow selection and switching of
   individual lambdas chosen flexibly from a detailed, fine granularity
   grid of available wavelengths.  This document updates the definition
   of GMPLS lambda labels to support the flexi-grid.

   This document updates RFC 3471 and updates RFC 6205.

Status of this Memo

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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

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   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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

1.  Introduction

   As described in [RFC3945], GMPLS extends MPLS from supporting only
   Packet Switching Capable (PSC) interfaces and switching to also
   support four new classes of interfaces and switching that include
   Lambda Switch Capable (LSC).

   A functional description of the extensions to MPLS signaling needed
   to support this new class of interface and switching is provided in
   [RFC3471].

   [RFC3471] states that wavelength labels "only have significance
   between two neighbors" (Section 3.2.1.1); global wavelength semantics
   are not considered.  [RFC6205] defines a standard lambda label format
   which is compliant with both the Dense Wavelength Division
   Multiplexing (DWDM) grid [G.694.1] and the Coarse Wavelength Division
   Multiplexing (CWDM) grid [G.694.2]. The terms DWDM and CWDM are
   defined in [G.671].

   A flexible grid network selects its data channels as arbitrarily
   assigned spectral slices.  Mixed bitrate transmission systems can
   allocate their channels with different spectral bandwidths so that
   the channels can be optimized for the bandwidth requirements of the
   particular bit rate and modulation scheme of the individual channels.
   This technique is regarded as a promising way to improve the network
   utilization efficiency and fundamentally reduce the cost of the core
   network.

   The "flexi-grid" is being developed within the ITU-T Study Group 15
   to allow selection and switching of individual lambdas chosen
   flexibly from a detailed, fine granularity grid of wavelengths with
   arbitrary spectral bandwidth [G.FLEXIGRID].  This document updates
   the definition of GMPLS lambda labels provided in [RFC6205] to
   support the flexi-grid.

   This document will not be put forward for publication as an RFC
   before the ITU-T have completed technical development of
   [G.FLEXIGRID], and the encoding specified in this document will also
   be communicated to the ITU-T for comment before publication as an
   RFC.

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1.1.  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].

2.  Overview of Flexi-Grid

   [G.FLEXIGRID] extends DWDM fixed grids as defined in [G.694.1] to
   add support for flexible grids. The basis of the work is to allow
   a data channel to be formed from an abstract grid anchored at
   193.1 THz and selected on a channel spacing of 6.25 GHz with a
   variable slot width measured in units of 12.5 GHz. Individual
   allocations may be made on this basis from anywhere in the spectrum,
   subject to allocations not overlapping.

   [G.FLEXIGRID] provides clear guidance on the support of flexible grid
   by implementations in Section 2 of Appendix I:

      However, devices or applications that make use of the flexible
      grid may not have to be capable of supporting every possible slot
      width or position. In other words, applications may be defined
      where only a subset of the possible slot widths and positions are
      required to be supported.

      For example, an application could be defined where the nominal
      central frequency granularity is 12.5 GHz (by only requiring
      values of n that are even) and that only requires slot widths as a
      multiple of 25 GHz (by only requiring values of m that are even).

3.  Fixed Grid Lambda Label Encoding

   [RFC6205] defines an encoding for a global semantic for a DWDM label
   based on four fields:

   - Grid: used to select which grid the lambda is selected from.
     Values defined in [RFC6205] identify DWDM [G.694.1] and CWDM
     [G.694.2].

   - C.S. (Channel Spacing): used to indicate the channel spacing.
     [RFC6205] defines values to represent spacing of 100, 50, 25 and
     12.5 GHz.

   - Identifier: a local-scoped integer used to distinguish different
     lasers (in one node) when they can transmit the same frequency
     lambda.

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   - n: a two's-complement integer to take either a positive, negative,
     or zero value.  This value is used to compute the frequency as
     defined in [RFC6205] and based on [G.694.1].  The use of n is
     repeated here for ease of reading.

        Frequency (THz) = 193.1 THz + n * channel spacing (THz)

4.  Flexi-Label Format and Values

4.1 Flexi-Label Encoding

   This document defines a new generalized label encoding for use in
   flexi-grid systems. As with all other GMPLS lambda labels, the use of
   this label is known a priori. That is, since the interpretation of
   all lambda labels is determined hop-by-hop, the use of this label
   requires that all nodes on the path expect to use this label.

   For convenience, however, the label is modeled on the fixed grid
   label defined in [RFC6205] and briefly described in Section 3.

   Figure 1 shows the format of the Flexi-Label. It is a 64 bit label.

   [Editors' note: We considered the possibility of having a 40 bit
   label with no reserved bits, or a 48 bit label with 8 reserved bits.
   This would be somewhat more efficient for objects that carry multiple
   labels encoded as a sequence. However, since most uses of the label
   are in objects where the label is padded to a 32 bit boundary, there
   seemed little benefit.]

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Grid | C.S.  |    Identifier   |              n                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       m       |                  Reserved                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

        Figure 1 : The Flexi-Label Encoding

   This document defines a new Grid value to supplement those in
   [RFC6205]:

    +----------+---------+
    |   Grid   |  Value  |
    +----------+---------+
    |ITU-T Flex|    3    |
    +----------+---------+

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   Within the fixed grid network, the C.S. value is used to represent
   the channel spacing, as the spacing between adjacent channels is
   constant. While, for flexible grid situation, this field should be
   used to represent the channel spacing granularity/or central
   frequency granularity.

   This document defines a new C.S. value to supplement those in
   [RFC6205]:

    +----------+---------+
    | C.S(GHz) |  Value  |
    +----------+---------+
    |     6.25 |    5    |
    +----------+---------+

   The meaning of the Identifier field is maintained from [RFC6205] (see
   also Section 3).

   The meaning of n is maintained from [RFC6205] (see also Section 3).

   The m field is used to identify the slot width according to the
   formula given in [G.FLEXIGRID] as follows:

         Slot Width (GHz) = 12.5 GHz * m

   The practical range of values for m is from 1 to 8 for slot widths
   ranging from 12.5 GHz to 100 GHz. Wider slot widths may be considered
   with larger values of m.

   The Reserved field MUST be set to zero on transmission and SHOULD be
   ignored on receipt.

   An implementation that wishes to use the flexi-grid MUST follow the
   procedures of [RFC3473] and of [RFC3471] as updated by [RFC6205]. It
   MUST set Grid to 3 and C.S. to 5. It MUST set Identifier to indicate
   the local identifier of the laser in use as described in [RFC6205].
   It MUST also set n according to the formula in Section 3 (inherited
   unchanged from [RFC6205]).  Finally,the implementation MUST set m as
   described in the formula stated above.

5.  Manageability Considerations

   This document introduces no new elements for management. That is,
   labels will continue to be used in the same way by the GMPLS
   protocols and lambda labels have the same fields as previously
   defined so any management tools defined to handle [RFC6205] labels
   will be able to handle labels as specified in this document. However,
   it is obvious that the management tools will have to interpret the

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   new values and meanings of label fields as defined in this document,
   and management tools that may have been (unwisely) coded to expect
   all lambda labels to be 32 bits, will need to be updated to handle
   these 64 bit labels.

6.  Security Considerations

   [RFC6205] notes that the definition of a new label encoding does not
   introduces any new security considerations to [RFC3471] and
   [RFC3473]. That statement applies equally to this document.

   For a general discussion on MPLS and GMPLS-related security issues,
   see the MPLS/GMPLS security framework [RFC5920].

7.  IANA Considerations

   IANA maintains the "Generalized Multi-Protocol Label Switching
   (GMPLS) Signaling Parameters" registry that contains several
   subregistries.

7.1.  Grid Subregistry

   IANA is requested to allocate a new entry in this subregistry as
   follows:

   Value   Grid                         Reference
   -----   -------------------------    ----------
     3     ITU-T Flex                   [This.I-D]

7.2.  DWDM Channel Spacing Subregistry

   IANA is requested to allocate a new entry in this subregistry as
   follows:

   Value   Channel Spacing (GHz)        Reference
   -----   -------------------------    ----------
     5     6.25                         [This.I-D]

8.  Acknowledgments

   Very many thanks to Lou Berger for discussions of labels of more than
   32 bits.

   Many thanks to Sergio Belotti, Pietro Vittorio Grandi and Fatai Zhang
   for their support of this work.

   The authors would like to thank Ben Niven-Jenkins for inspiring the
   choice of filename for this document.

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9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3471]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Functional Description", RFC
              3471, January 2003.

   [RFC3473]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Resource ReserVation Protocol-
              Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
              January 2003.

   [RFC6205]  Otani, T., and Li, D., "Generalized Labels for Lambda-
              Switch-Capable (LSC) Label Switching Routers", RFC 6205,
              March 2011.

   [G.FLEXIGRID] Preliminary Draft revised G.694.1 (revision 2) version
              6. Unpublished ITU-T Study Group 15, Question 6, December
              2011.

9.2.  Informative References

   [RFC3945]  Mannie, E., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Architecture", RFC 3945, October 2004.

   [G.671]    ITU-T Recommendation G.671, "Transmission characteristics
              of optical components and subsystems", 2009.

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

   [G.694.2]  ITU-T Recommendation G.694.2, "Spectral grids for WDM
              applications: CWDM wavelength grid", December 2003.

   [RFC5920]  Fang, L., Ed., "Security Framework for MPLS and GMPLS
              Networks", RFC 5920, July 2010.

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Appendix A.  Flexi-Grid Example

   Considering the network displayed in Figure 2 (reproduced from
   [RFC6205]) it is possible to show an example of LSP setup using the
   lambda labels. The figure shows Reconfigurable Optical Add/Drop
   Multiplexers (ROADMs) and Wavelength Cross-Connects (WXCs) that
   operate at the wavelength switching level as well as PXCs

                                  |
      Domain A (or Vendor A)      |      Domain B (or Vendor B)
                                  |
     Node-1            Node-2     |         Node-6            Node-7
   +--------+        +--------+   |      +-------+ +-+     +-+ +-------+
   | ROADM  |        | ROADM  +---|------+  PXC  +-+D|     |D+-+  PXC  |
   | or WXC +========+ or WXC +---|------+       +-+W+=====+W+-+       |
   | (LSC)  |        | (LSC)  +---|------+ (LSC) +-+D|     |D+-+ (LSC) |
   +--------+        +--------+   |      |       +-|M|     |M+-+       |
       ||                ||       |      +++++++++ +-+     +-+ +++++++++
       ||     Node-3     ||       |       |||||||               |||||||
       ||   +--------+   ||       |      +++++++++             +++++++++
       ||===|  WXC   +===||       |      | DWDM  |             | DWDM  |
            | (LSC)  |            |      +--++---+             +--++---+
       ||===+        +===||       |         ||                    ||
       ||   +--------+   ||       |      +--++---+             +--++---+
       ||                ||       |      | DWDM  |             | DWDM  |
   +--------+        +--------+   |      +++++++++             +++++++++
   | ROADM  |        | ROADM  |   |       |||||||               |||||||
   | or WXC +========+ or WXC +=+ |  +-+ +++++++++ +-+     +-+ +++++++++
   | (LSC)  |        | (LSC)  | | |  |D|-|  PXC  +-+D|     |D+-+  PXC  |
   +--------+        +--------+ +=|==+W|-|       +-+W+=====+W+-+       |
     Node-4            Node-5     |  |D|-| (LSC) +-+D|     |D+-+ (LSC) |
                                  |  |M|-|       +-+M|     |M+-+       |
                                  |  +-+ +-------+ +-+     +-+ +-------+
                                  |        Node-8             Node-9

                      Figure 2 : Example Network

   Node 1 receives the request for establishing an LSP from itself to
   Node 9.  The ITU-T grid to be used is the Flexi-Grid, the channel
   spacing is 6.25 GHz, and the wavelength to be used is 193.05 THz.
   The cslot width to be used is 50 GHz.  Node 1 signals the LSP using a
   Path message including a wavelength label structured 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |Grid |  C.S. |   Identifier    |              n                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       m       |                  Reserved                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

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   Where:

     Grid = 3 : ITU-T Flexi-Grid

     C.S. = 5 : 6.25 GHz channel spacing

     Identifier = local value indicating the laser in use

     n = 24 :

          Frequency (THz) = 193.1 THz + n * channel spacing (THz)

          193.05 (THz) = 193.1 (THz) + n* 0.00625 (THz)

          n = (193.05-193.1)/0.00625 = -8

     m = 4 :

          Slot Width (GHz) = 12.5 GHz * m

          50 (GHz) = 12.5 (GHz) * m

          m = 50 / 12.5 = 4

Authors' Addresses

   Adrian Farrel
   Old Dog Consulting
   EMail: adrian@olddog.co.uk

   Daniel King (Editor)
   Old Dog Consulting
   EMail: daniel@olddog.co.uk

   Yao Li (Editor)
   ZTE
   EMail: li.yao3@zte.com.cn

   Zhang Fei
   ZTE
   EMail: zhang.fei3@zte.com.cn

   Ramon Casellas
   CTTC
   EMail: ramon.casellas@cttc.es

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