path: root/doc/rfc/rfc8363.txt

Internet Engineering Task Force (IETF)                          X. Zhang
Request for Comments: 8363                                      H. Zheng
Category: Standards Track                                         Huawei
ISSN: 2070-1721                                              R. Casellas
                                                                    CTTC
                                                     O. Gonzalez de Dios
                                                              Telefonica
                                                           D. Ceccarelli
                                                                Ericsson
                                                                May 2018


           GMPLS OSPF-TE Extensions in Support of Flexi-Grid
         Dense Wavelength Division Multiplexing (DWDM) Networks

Abstract

   The International Telecommunication Union Telecommunication
   standardization sector (ITU-T) has extended its Recommendations
   G.694.1 and G.872 to include a new Dense Wavelength Division
   Multiplexing (DWDM) grid by defining channel spacings, a set of
   nominal central frequencies, and the concept of the "frequency slot".
   Corresponding techniques for data-plane connections are known as
   "flexi-grid".

   Based on the characteristics of flexi-grid defined in G.694.1 and in
   RFCs 7698 and 7699, this document describes the Open Shortest Path
   First - Traffic Engineering (OSPF-TE) extensions in support of GMPLS
   control of networks that include devices that use the new flexible
   optical grid.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8363.







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Copyright Notice

   Copyright (c) 2018 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
   (https://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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Conventions Used in This Document . . . . . . . . . . . .   4
   3.  Requirements for Flexi-Grid Routing . . . . . . . . . . . . .   4
     3.1.  Available Frequency Ranges  . . . . . . . . . . . . . . .   4
     3.2.  Application Compliance Considerations . . . . . . . . . .   5
     3.3.  Comparison with Fixed-Grid DWDM Links . . . . . . . . . .   6
   4.  Extensions  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Interface Switching Capability Descriptor (ISCD)
           Extensions for Flexi-Grid . . . . . . . . . . . . . . . .   7
       4.1.1.  Switching Capability Specific Information (SCSI)  . .   8
       4.1.2.  An SCSI Example . . . . . . . . . . . . . . . . . . .  10
     4.2.  Extensions to the Port Label Restrictions Field . . . . .  11
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  13
     5.1.  New ISCD Switching Type . . . . . . . . . . . . . . . . .  13
     5.2.  New SCSI Type . . . . . . . . . . . . . . . . . . . . . .  13
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  14
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  15
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  16
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17











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1.  Introduction

   [G.694.1] defines the Dense Wavelength Division Multiplexing (DWDM)
   frequency grids for Wavelength Division Multiplexing (WDM)
   applications.  A frequency grid is a reference set of frequencies
   used to denote allowed nominal central frequencies that may be used
   for defining applications.  The channel spacing is the frequency
   spacing between two allowed nominal central frequencies.  All of the
   wavelengths on a fiber should use different central frequencies and
   occupy a fixed bandwidth of frequency.

   Fixed-grid channel spacing ranges from one of 12.5 GHz, 25 GHz, 50
   GHz, or 100 GHz to integer multiples of 100 GHz.  But [G.694.1] also
   defines a "flexible grid", also known as "flexi-grid".  The terms
   "frequency slot" (i.e., the frequency range allocated to a specific
   channel and unavailable to other channels within a flexible grid) and
   "slot width" (i.e., the full width of a frequency slot in a flexible
   grid) are used to define a flexible grid.

   [RFC7698] defines a framework and the associated control-plane
   requirements for the GMPLS-based control of flexi-grid DWDM networks.

   [RFC6163] provides a framework for GMPLS and Path Computation Element
   (PCE) control of Wavelength Switched Optical Networks (WSONs).
   [RFC7688] defines the requirements and OSPF-TE extensions in support
   of GMPLS control of a WSON.

   [RFC7792] describes requirements and protocol extensions for
   signaling to set up Label Switched Paths (LSPs) in networks that
   support the flexi-grid.  This document complements [RFC7792] by
   describing the requirement and extensions for OSPF-TE routing in a
   flexi-grid network.

   This document complements the efforts to provide extensions to the
   OSPF-TE protocol so as to support GMPLS control of flexi-grid
   networks.

2.  Terminology

   For terminology related to flexi-grid, please consult [RFC7698] and
   [G.694.1].










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2.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  Requirements for Flexi-Grid Routing

   The architecture for establishing LSPs in a Spectrum Switched Optical
   Network (SSON) is described in [RFC7698].

   A flexi-grid LSP occupies one or multiple specific frequency slots.
   The process of computing a route and the allocation of a frequency
   slot is referred to as "RSA" (Routing and Spectrum Assignment).
   [RFC7698] describes three types of architectural approaches to RSA:
   combined RSA, separated RSA, and routing and distributed SA.  The
   first two approaches could be called "centralized SA" because the
   spectrum (frequency slot) assignment is performed by a single entity
   before the signaling procedure.

   In the case of centralized SA, the assigned frequency slot is
   specified in the RSVP-TE Path message during the signaling process.
   In the case of routing and distributed SA, only the requested slot
   width of the flexi-grid LSP is specified in the Path message,
   allowing the involved network elements to select the frequency slot
   to be used.

   If the capability of switching or converting the whole optical
   spectrum allocated to an optical spectrum LSP is not available at
   nodes along the path of the LSP, the LSP is subject to the Optical
   "Spectrum Continuity Constraint", as described in [RFC7698].

   The remainder of this section states the additional extensions on the
   routing protocols in a flexi-grid network.

3.1.  Available Frequency Ranges

   In the case of flexi-grids, the central frequency steps from 193.1
   THz with 6.25 GHz granularity.  The calculation method of central
   frequency and the frequency slot width of a frequency slot are
   defined in [G.694.1], i.e., by using nominal central frequency n and
   the slot width m.







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   On a DWDM link, the allocated or in-use frequency slots do not
   overlap with each other.  However, the border frequencies of two
   frequency slots may be the same frequency, i.e., the upper bound of a
   frequency slot and the lower bound of the directly adjacent frequency
   slot are the same.

                         Frequency Slot 1   Frequency Slot 2
                           +-----------+-----------------------+
                           |           |                       |
      -9 -8 -7 -6 -5 -4 -3 -2 -1 0  1  2  3  4  5  6  7  8  9 10  11
   ...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--...
                           ------------ ------------------------
                                 ^                 ^
                    Central F = 193.1 THz   Central F = 193.1375 THz
                     Slot width = 25 GHz    Slot width = 50 GHz

                  Figure 1: Two Frequency Slots on a Link

   Figure 1 shows two adjacent frequency slots on a link.  The highest
   frequency of frequency slot 1 denoted by n=2 is the lowest frequency
   of slot 2.  In this example, it means that the frequency range from
   n=-2 to n=10 is unavailable to other flexi-grid LSPs.  Available
   central frequencies are advertised for m=1, which means that for an
   available central frequency n, the frequency slot from central
   frequency n-1 to central frequency n+1 is available.

   Hence, in order to clearly show which frequency slots are available
   and can be used for LSP establishment and which frequency slots are
   unavailable, the availability of frequency slots is advertised by the
   routing protocol for the flexi-grid DWDM links.  A set of non-
   overlapping available frequency ranges is disseminated in order to
   allow efficient resource management of flexi-grid DWDM links and RSA
   procedures, which are described in Section 4.8 of [RFC7698].

3.2.  Application Compliance Considerations

   As described in [G.694.1], devices or applications that make use of
   the flexi-grid may not be capable of supporting every possible slot
   width or position (i.e., central frequency).  In other words,
   applications or implementations 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 the same application only requires slot
   widths as a multiple of 25 GHz (by only requiring values of m that
   are even).




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   Hence, in order to support all possible applications and
   implementations, the following information SHOULD be advertised for a
   flexi-grid DWDM link:

   o  Channel Spacing (C.S.): as defined in [RFC7699] for flexi-grid, is
      set to 5 to denote 6.25 GHz.

   o  Central frequency granularity: a multiplier of C.S.

   o  Slot width granularity: a multiplier of 2*C.S.

   o  Slot width range: two multipliers of the slot width granularity,
      each indicating the minimal and maximal slot width supported by a
      port, respectively.

   The combination of slot width range and slot width granularity can be
   used to determine the slot widths set supported by a port.

3.3.  Comparison with Fixed-Grid DWDM Links

   In the case of fixed-grid DWDM links, each wavelength has a
   predefined central frequency.  Each wavelength maps to a predefined
   central frequency, and the usable frequency range is implicit by the
   channel spacing.  All the wavelengths on a DWDM link can be
   identified with an identifier that mainly conveys its central
   frequency as the label defined in [RFC6205]; the status of the
   wavelengths (available or not) can be advertised through a routing
   protocol.

   Figure 2 shows a link that supports a fixed-grid with 50 GHz channel
   spacing.  The central frequencies of the wavelengths are predefined
   by values of "n", and each wavelength occupies a fixed 50 GHz
   frequency range as described in [G.694.1].

        W(-2)  |    W(-1)  |    W(0)   |    W(1)   |     W(2)  |
   ...---------+-----------+-----------+-----------+-----------+----...
         |   50 GHz  |  50 GHz   |  50 GHz   |   50 GHz  |

       n=-2        n=-1        n=0         n=1         n=2
   ...---+-----------+-----------+-----------+-----------+----------...
                                 ^
                    Central F = 193.1 THz

                Figure 2: A Link Supports Fixed Wavelengths
                        with 50 GHz Channel Spacing






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   Unlike the fixed-grid DWDM links, on a flexi-grid DWDM link, the slot
   width of the frequency slot is flexible, as described in Section 3.1.
   That is, the value of m in the following formula from [G.694.1] is
   uncertain before a frequency slot is actually allocated for a flexi-
   grid LSP.

                Slot Width (in GHz) = 12.5GHz * m

   For this reason, the available frequency slots (or ranges) are
   advertised for a flexi-grid DWDM link instead of the specific
   "wavelength" points that are sufficient for a fixed-grid link.
   Moreover, this advertisement is represented by the combination of
   central frequency granularity and slot width granularity.

4.  Extensions

   The network-connectivity topology constructed by the links and/or
   nodes and node capabilities are the same as for WSON, as described in
   [RFC7698], and they can be advertised by the GMPLS routing protocols
   using Opaque Link State Advertisements (LSAs) [RFC3630] in the case
   of OSPF-TE [RFC4203] (refer to Section 6.2 of [RFC6163]).  In the
   flexi-grid case, the available frequency ranges, instead of the
   specific "wavelengths", are advertised for the link.  This section
   defines the GMPLS OSPF-TE extensions in support of advertising the
   available frequency ranges for flexi-grid DWDM links.

4.1.  Interface Switching Capability Descriptor (ISCD) Extensions for
      Flexi-Grid

   This section defines a new value for the Switching Capability field
   of the ISCD with a value of 152 and type name Flexi-Grid-LSC.

            Value              Name
            -----              --------------
            152                Flexi-Grid-LSC

   Switching Capability and Encoding values MUST be used as follows:

            Switching Capability = Flexi-Grid-LSC

            Encoding Type = lambda (as defined in [RFC3471])

   When the Switching Capability and Encoding fields are set to values
   as stated above, the ISCD is interpreted as in [RFC4203] with the
   optional inclusion of one or more Switching Capability Specific
   Information (SCSI) sub-TLVs.





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   As the "Max LSP Bandwidth at priority x" (x from 0 to 7) fields in
   the generic part of the ISCD [RFC4203] are not meaningful for flexi-
   grid DWDM links, the values of these fields MUST be set to zero and
   MUST be ignored.  The SCSI as defined below provides the
   corresponding information for flexi-grid DWDM links.

4.1.1.  Switching Capability Specific Information (SCSI)

   [RFC8258] defines a Generalized SCSI for the ISCD.  This document
   defines the Frequency Availability Bitmap as a new type of the
   Generalized SCSI TLV.  The technology-specific part of the flexi-grid
   ISCD includes the available frequency-spectrum resource as well as
   the information regarding max slot widths per priority.  The format
   of this flexi-grid SCSI, the Frequency Availability Bitmap sub-TLV,
   is depicted in the following figure:

     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  = 11           |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Priority    |                   Reserved                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~ Max Slot Width at Priority k  |   Unreserved Padding          ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | C.S.  |       Starting n              | No. of Effective Bits |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |       Bitmap                  ...                             ~
    ~      ...                              |  padding bits         ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type (16 bits): The type of this sub-TLV (11).

   Length (16 bits): The length of the value field of this sub-TLV in
   octets.

   Priority (8 bits): A bitmap used to indicate which priorities are
   being advertised.  The bitmap is in ascending order, with the
   leftmost bit representing priority level 0 (i.e., the highest) and
   the rightmost bit representing priority level 7 (i.e., the lowest).
   A bit is set (1) corresponding to each priority represented in the
   sub-TLV and clear (0) for each priority not represented in the sub-
   TLV.  At least one priority level MUST be advertised.  If only one
   priority level is advertised, it MUST be at priority level 0.

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




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   Max Slot Width at Priority k (16 bits): This field indicates maximal
   frequency slot width supported at a particular priority level, up to
   8.  This field is set to max frequency slot width supported in the
   unit of 2*C.S., for a particular priority level.  One field MUST be
   present for each bit set in the Priority field, and each present
   field is ordered to match the Priority field.  Fields MUST be present
   for priority levels that are indicated in the Priority field.

   Unreserved Padding (16 bits): The Padding field is used to ensure the
   32-bit alignment of Max Slot Width at Priority k.  When k is an odd
   number, the Unreserved Padding field MUST be included.  When k is an
   even number, the Unreserved Padding field MUST be omitted.  This
   field MUST be set to 0 and MUST be ignored on receipt.

   C.S. (4 bits): As defined in [RFC7699]; it is currently set to 5.

   Starting n (16 bits): As defined in [RFC7699].  This value denotes
   the starting point of the nominal central frequency of the frequency
   availability bitmap sub-TLV.

   No. of Effective Bits (12 bits): Indicates the number of effective
   bits in the Bitmap field.

   Bitmap (variable): Indicates whether or not a basic frequency slot,
   characterized by a nominal central frequency and a fixed m value of
   1, is available for flexi-grid LSP setup.  The first nominal central
   frequency is the value of starting n; subsequent nominal central
   frequencies are implied by the position in the bitmap.  Note that
   setting to 1 indicates that the corresponding central frequency is
   available for a flexi-grid LSP with m=1 and setting to 0 indicates
   the corresponding central frequency is unavailable.  Note that a
   centralized SA process will need to extend this to high values of m
   by checking a sufficiently large number of consecutive basic
   frequency slots that are available.

   padding bits (variable): Padded after the Bitmap to make it a
   multiple of four bytes, if necessary.  Padding bits MUST be set to 0
   and MUST be ignored on receipt.

   An example is provided in Section 4.1.2.











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4.1.2.  An SCSI Example

   Figure 3 shows an example of the available frequency spectrum
   resource of a flexi-grid DWDM link.

      -9 -8 -7 -6 -5 -4 -3 -2 -1 0  1  2  3  4  5  6  7  8  9 10  11
   ...+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--...
                           |--Available Frequency Range--|

                  Figure 3: Flexi-Grid DWDM Link Example

   The symbol "+" represents the allowed nominal central frequency.  The
   symbol "--" represents a central frequency granularity of 6.25 GHz,
   which is currently standardized in [G.694.1].  The number on the top
   of the line represents the "n" in the frequency calculation formula
   (193.1 + n * 0.00625).  The nominal central frequency is 193.1 THz
   when n equals zero.

   In this example, it is assumed that the lowest nominal central
   frequency supported is n=-9 and the highest is n=11.  Note they
   cannot be used as a nominal central frequency for setting up an LSP,
   but merely as the way to express the supported frequency range.
   Using the encoding defined in Section 4.1.1, the relevant fields to
   express the frequency resource availability can be filled as below:

     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  = 11           |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Priority    |                   Reserved                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~ Max Slot Width at Priority k  |   Unreserved Padding          ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   5   |       Starting n (-9)         | No. of Effec. Bits(21)|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0|0|0|0|0|0|0|0|1|1|1|1|1|1|1|1|1|0|0|0|0|  padding bits (0s)  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   In the above example, the starting n is selected to be the lowest
   nominal central frequency, i.e., -9.  It is observed from the bitmap
   that n=-1 to 7 can be used to set up LSPs.  Note other starting n
   values can be chosen to represent the bitmap; for example, the first
   available nominal central frequency (a.k.a., the first available
   basic frequency slot) can be chosen, and the SCSI will be expressed
   as the following:





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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  = 11           |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Priority    |                   Reserved                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~ Max Slot Width at Priority k  |   Unreserved Padding          ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   5   |       Starting n (-1)         | No. of Effec. Bits(9)|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |1|1|1|1|1|1|1|1|1|            padding bits (0s)                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   This encoding denotes that, other than the advertised available
   nominal central frequencies, the other nominal central frequencies
   within the whole frequency range supported by the link are not
   available for flexi-grid LSP setup.

   If an LSP with slot width m equal to 1 is set up using this link, say
   using n=-1, then the SCSI information is updated to be the following:

     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  = 11           |           Length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Priority    |                   Reserved                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    ~ Max Slot Width at Priority k  |   Unreserved Padding          ~
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   5   |       Starting n (-1)         | No. of Effec. Bits(9)|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0|0|1|1|1|1|1|1|1|            padding bits (0s)                |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.2.  Extensions to the Port Label Restrictions Field

   As described in Section 3.2, a port that supports flexi-grid may
   support only a restricted subset of the full flexible grid.  The Port
   Label Restrictions field is defined in [RFC7579].  It can be used to
   describe the label restrictions on a port and is carried in the top-
   level Link TLV as specified in [RFC7580].  A new restriction type,
   the flexi-grid Restriction Type, is defined here to specify the
   restrictions on a port to support flexi-grid.






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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    | MatrixID      | RstType = 5   | Switching Cap |   Encoding    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  C.S. |     C.F.G     |    S.W.G      |     Reserved          |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      Min Slot Width           |        Reserved               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   MatrixID (8 bits): As defined in [RFC7579].

   RstType (Restriction Type, 8 bits): Takes the value of 5 to indicate
   the restrictions on a port to support flexi-grid.

   Switching Cap (Switching Capability, 8 bits): As defined in
   [RFC7579], MUST be consistent with the one specified in ISCD as
   described in Section 4.1.

   Encoding (8 bits): As defined in [RFC7579], MUST be consistent with
   the one specified in ISCD as described in Section 4.1.

   C.S. (4 bits): As defined in [RFC7699].  For flexi-grid, it is 5 to
   denote 6.25 GHz.

   C.F.G (Central Frequency Granularity, 8 bits): A positive integer.
   Its value indicates the multiple of C.S., in terms of central
   frequency granularity.

   S.W.G (Slot Width Granularity, 8 bits): A positive integer.  Its
   value indicates the multiple of 2*C.S., in terms of slot width
   granularity.

   Min Slot Width (16 bits): A positive integer.  Its value indicates
   the multiple of 2*C.S. (in GHz), in terms of the supported minimal
   slot width.

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











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5.  IANA Considerations

5.1.  New ISCD Switching Type

   IANA has made the following assignment in the "Switching Types" sub-
   registry of the "Generalized Multi-Protocol Label Switching (GMPLS)
   Signaling Parameters" registry located at
   <https://www.iana.org/assignments/gmpls-sig-parameters>:

         Value      Name                Reference
         -------    ----------------    ----------
         152        Flexi-Grid-LSC      RFC 8363

5.2.  New SCSI Type

   This document defines a new generalized SCSI sub-TLV that is carried
   in the Interface Switching Capability Descriptors [RFC4203] when the
   Switching Type is set to Flexi-Grid-LSC.

   IANA has made the following assignment in the "Generalized SCSI
   (Switching Capability Specific Information) TLV Types" sub-registry
   [RFC8258] of the "Generalized Multi-Protocol Label Switching (GMPLS)
   Signaling Parameters" registry located at
   <https://www.iana.org/assignments/gmpls-sig-parameters>:

   Value  SCSI-TLV                        Switching Type   Reference
   -----  -----------------------------   --------------   ---------
    11    Frequency Availability Bitmap   152              RFC 8363

6.  Security Considerations

   This document extends [RFC4203] and [RFC7580] to carry flexi-grid-
   specific information in OSPF Opaque LSAs.  This document does not
   introduce any further security issues other than those discussed in
   [RFC3630] and [RFC4203].  To be more specific, the security
   mechanisms described in [RFC2328], which apply to Opaque LSAs carried
   in OSPF, still apply.  An analysis of the OSPF security is provided
   in [RFC6863] and applies to the extensions to OSPF in this document
   as well.












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7.  References

7.1.  Normative References

   [G.694.1]  International Telecommunication Union, "Spectral grids for
              WDM applications: DWDM frequency grid", ITU-T
              Recommendation G.694.1, February 2012,
              <https://www.itu.int/rec/T-REC-G.694.1/en>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC3471]  Berger, L., Ed., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Functional Description",
              RFC 3471, DOI 10.17487/RFC3471, January 2003,
              <https://www.rfc-editor.org/info/rfc3471>.

   [RFC4203]  Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
              <https://www.rfc-editor.org/info/rfc4203>.

   [RFC6205]  Otani, T., Ed. and D. Li, Ed., "Generalized Labels for
              Lambda-Switch-Capable (LSC) Label Switching Routers",
              RFC 6205, DOI 10.17487/RFC6205, March 2011,
              <https://www.rfc-editor.org/info/rfc6205>.

   [RFC7579]  Bernstein, G., Ed., Lee, Y., Ed., Li, D., Imajuku, W., and
              J. Han, "General Network Element Constraint Encoding for
              GMPLS-Controlled Networks", RFC 7579,
              DOI 10.17487/RFC7579, June 2015,
              <https://www.rfc-editor.org/info/rfc7579>.

   [RFC7580]  Zhang, F., Lee, Y., Han, J., Bernstein, G., and Y. Xu,
              "OSPF-TE Extensions for General Network Element
              Constraints", RFC 7580, DOI 10.17487/RFC7580, June 2015,
              <https://www.rfc-editor.org/info/rfc7580>.

   [RFC7699]  Farrel, A., King, D., Li, Y., and F. Zhang, "Generalized
              Labels for the Flexi-Grid in Lambda Switch Capable (LSC)
              Label Switching Routers", RFC 7699, DOI 10.17487/RFC7699,
              November 2015, <https://www.rfc-editor.org/info/rfc7699>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.



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   [RFC8258]  Ceccarelli, D. and L. Berger, "Generalized SCSI: A Generic
              Structure for Interface Switching Capability Descriptor
              (ISCD) Switching Capability Specific Information (SCSI)",
              RFC 8258, DOI 10.17487/RFC8258, October 2017,
              <https://www.rfc-editor.org/info/rfc8258>.

7.2.  Informative References

   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328,
              DOI 10.17487/RFC2328, April 1998,
              <https://www.rfc-editor.org/info/rfc2328>.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

   [RFC6163]  Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku,
              "Framework for GMPLS and Path Computation Element (PCE)
              Control of Wavelength Switched Optical Networks (WSONs)",
              RFC 6163, DOI 10.17487/RFC6163, April 2011,
              <https://www.rfc-editor.org/info/rfc6163>.

   [RFC6863]  Hartman, S. and D. Zhang, "Analysis of OSPF Security
              According to the Keying and Authentication for Routing
              Protocols (KARP) Design Guide", RFC 6863,
              DOI 10.17487/RFC6863, March 2013,
              <https://www.rfc-editor.org/info/rfc6863>.

   [RFC7688]  Lee, Y., Ed. and G. Bernstein, Ed., "GMPLS OSPF
              Enhancement for Signal and Network Element Compatibility
              for Wavelength Switched Optical Networks", RFC 7688,
              DOI 10.17487/RFC7688, November 2015,
              <https://www.rfc-editor.org/info/rfc7688>.

   [RFC7698]  Gonzalez de Dios, O., Ed., Casellas, R., Ed., Zhang, F.,
              Fu, X., Ceccarelli, D., and I. Hussain, "Framework and
              Requirements for GMPLS-Based Control of Flexi-Grid Dense
              Wavelength Division Multiplexing (DWDM) Networks",
              RFC 7698, DOI 10.17487/RFC7698, November 2015,
              <https://www.rfc-editor.org/info/rfc7698>.

   [RFC7792]  Zhang, F., Zhang, X., Farrel, A., Gonzalez de Dios, O.,
              and D. Ceccarelli, "RSVP-TE Signaling Extensions in
              Support of Flexi-Grid Dense Wavelength Division
              Multiplexing (DWDM) Networks", RFC 7792,
              DOI 10.17487/RFC7792, March 2016,
              <https://www.rfc-editor.org/info/rfc7792>.



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Acknowledgments

   This work was supported in part by the FP-7 IDEALIST project under
   grant agreement number 317999.

   This work was supported in part by NSFC Project 61201260.

Contributors

   Adrian Farrel
   Juniper Networks

   Email: afarrel@juniper.net


   Fatai Zhang
   Huawei Technologies

   Email: zhangfatai@huawei.com


   Lei Wang
   Beijing University of Posts and Telecommunications

   Email: wang.lei@bupt.edu.cn


   Guoying Zhang
   China Academy of Information and Communication Technology

   Email: zhangguoying@ritt.cn




















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Authors' Addresses

   Xian Zhang
   Huawei Technologies

   Email: zhang.xian@huawei.com


   Haomian Zheng
   Huawei Technologies

   Email: zhenghaomian@huawei.com


   Ramon Casellas, Ph.D.
   CTTC
   Spain

   Phone: +34 936452916
   Email: ramon.casellas@cttc.es


   Oscar Gonzalez de Dios
   Telefonica Investigacion y Desarrollo
   Emilio Vargas 6
   Madrid, 28045
   Spain

   Phone: +34 913374013
   Email: oscar.gonzalezdedios@telefonica.com


   Daniele Ceccarelli
   Ericsson
   Via A. Negrone 1/A
   Genova - Sestri Ponente
   Italy

   Email: daniele.ceccarelli@ericsson.com












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