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Versions: 00 01 02 03 draft-ietf-ccamp-grid-property-lmp

Network Working Group                                           CCAMP
Internet Draft                                                     Y.Li
Intended status: Informational                                      ZTE
Expires: August 2014                                           G. Zhang
                                                                   CATR
                                                                   X.Fu
                                                                    ZTE
                                                            R. Casellas
                                                                   CTTC
                                                                Y Wang
                                                                   CATR
                                                      February 14, 2014


     Link Management Protocol Extensions for Grid Property Negotiation
                  draft-li-ccamp-grid-property-lmp-03.txt


Status of this Memo

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents



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Abstract

The recent updated version of ITU-T [G.694.1] has introduced the
flexible-grid DWDM technique, which provides a new tool that operators
can implement to provide a higher degree of network optimization than
is possible with fixed-grid systems.  This document describes the
extensions to the Link Management Protocol (LMP) to negotiate link grid
property between the adjacent DWDM nodes before the link is brought up.



Table of Contents

   1. Introduction ................................................ 3
      1.1. Conventions Used in This Document ....................... 3
   2. Terminology ................................................. 3
   3. Requirements for Grid Property Negotiation ................... 4
      3.1. Flexi-fixed Grid Nodes Interworking ..................... 4
      3.2. Flexible-Grid Capability Negotiation .................... 5
      3.3. Summary ................................................ 5
   4. LMP extensions .............................................. 6
      4.1. Grid Property Subobject................................. 6
   5. Messages Exchange Procedure.................................. 8
      5.1. Flexi-fixed Grid Nodes Messages Exchange ................ 8
      5.2. Flexible Nodes Messages Exchange ........................ 9
   6. Security Considerations..................................... 10
   7. IANA Considerations ........................................ 10
   8. References ................................................. 10
      8.1. Normative references................................... 10
      8.2. Informative References................................. 11
   9. Authors' Address ........................................... 11
   10. Contributors' Address...................................... 12




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1. Introduction

   The recent updated version of ITU-T [G.694.1] has introduced the
   flexible-grid DWDM technique, which provides a new tool that
   operators can implement to provide a higher degree of network
   optimization than is possible with fixed-grid systems. A flexible-
   grid network supports allocating a variable-sized spectral slot to a
   channel. Flexible-grid DWDM transmission systems can allocate their
   channels with different spectral bandwidths/slot widths so that they
   can be optimized for the bandwidth requirements of the particular
   bit rate and modulation scheme of the individual channels. This
   technique is regarded to be a promising way to improve the spectrum
   utilization efficiency and can be used in the beyond 100Gb/s
   transport systems.

   Fixed-grid DWDM system is regarded as a special case of Flexi-grid
   DWDM. It is expected that fixed-grid optical nodes will be gradually
   replaced by flexible nodes and interworking between fixed-grid DWDM
   and flexible-grid DWDM nodes will be needed as the network evolves.
   Additionally, even two flexible-grid optical nodes may have
   different grid properties based on the filtering component
   characteristics, thus need to negotiate on the specific parameters
   to be used during neighbor discovery process [draft-ietf-ccamp-
   flexi-grid-fwk-00]. This document describes the extensions to the
   Link Management Protocol (LMP) to negotiate a link grid property
   between two adjacent Flexi-grid nodes before the link is brought up.

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 RFC 2119 [RFC2119].



2. Terminology

   For the flexible-grid DWDM, the spectral resource is called
   frequency slot which is represented by the central frequency and the
   slot width. The defined nominal central frequency and the slot width
   can be referred to [FLEX-FWK].


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   In this contribution, some other definitions are listed below:

   Central frequency granularity: It is the granularity of the allowed
   central frequencies and is set to the multiple of 6.25 GHz.

   Slot width granularity: It is the granularity of the allowed slot
   width, and is set to the multiple of 12.5 GHz.

   Tuning range: It describes the supported spectrum slot range of the
   switching nodes or interfaces. It is represented by the supported
   minimal slot width and the maximum slot width.

   Channel spacing: It is used in traditional fixed-grid network to
   identify spectrum spacing between two adjacent channels.

3. Requirements for Grid Property Negotiation

3.1. Flexi-fixed Grid Nodes Interworking

   Figure 1 shows an example of interworking between flexible and
   fixed-grid nodes. Node A, B, D and E support flexible-grid. All
   these nodes can support frequency slots with a central frequency
   granularity of 6.25 GHz and slot width granularity of 12.5 GHz.
   Given the flexibility in flexible-grid nodes, it is possible to
   configure the nodes in such a way that the central frequencies and
   slot width parameters are backwards compatible with the fixed DWDM
   grids (adjacent flexible frequency slots with channel spacing of
   8*6.25 and slot width of 4*12.5 GHz is equivalent to fixed DWDM
   grids with channel spacing of 50 GHz).

   As node C can only support the fixed-grid DWDM property with channel
   spacing of 50 GHz, to establish a LSP through node B, C, D, the
   links between B to C and C to D must set to align with the fixed-
   grid values. This link grid property must be negotiated before
   establishing the LSP.

       +---+         +---+         +---+         +---+        +---+
       | A |---------| B |=========| C |=========| D +--------+ E |
       +---+         +---+         +---+         +---+        +---+
                Figure 1 An example of interworking between
                       flexible and fixed-grid nodes

             ^               ^               ^               ^
    ------->|<----50GHz---->|<----50GHz---->|<----50GHz---->|<------
      ..... |               |               |               | .....
    +-------+-------+-------+-------+-------+--------+------+-------+-
   n=-2              -1               0                1              2
                      Fixed channel spacing of 50 GHz (Node C)
             ^               ^               ^               ^


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             |               |               |               |
     --------+---------------+---------------+---------------+---------
       ..... |  n=-8, m=4    |   n=0, m=4    |   n=8, m=4    | .....
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
   n=-16 -14 -12 -10 -8  -6  -4  -2   0   2   4   6   8   10  12  14  16
                                                                    |_|
                          Flexi-grid (Nodes B,D)               6.25 GHz
                   Central frequency granularity=6.25 GHz
                       Slot width granularity=12.5 GHz
              Figure 2 Representation of fixed channel spacing
                       and flexi-grid spectrum slot

3.2. Flexible-Grid Capability Negotiation

   The updated version of ITU-T [G.694.1] has defined the flexible-grid
   with a central frequency granularity of 6.25 GHz and a slot width
   granularity of 12.5 GHz. However, devices or applications that make
   use of the flexible-grid may not be able to support every possible
   slot width. In other words, applications may be defined where
   different grid granularity can be supported. Taking node G as an
   example, an application could be defined where the central frequency
   granularity is 12.5 GHz requiring slot widths being multiple of 25
   GHz. Therefore the link between two optical nodes with different
   grid granularity must be configured to align with the larger of both
   granularities. Besides, different nodes may have different slot
   width tuning ranges. For example, in figure 3, node F can only
   support slot width with tuning change from 12.5 to 100 GHz, while
   node G supports tuning range from 25 GHz to 200 GHz. The link
   property of slot width tuning range for the link between F and G
   should be chosen as the range intersection, resulting in a range
   from 25 GHz to 100 GHz.

                          +---+            +---+
                          | F +------------| G |
                          +---+            +---+
              +------------------+-------------+-----------+
              |    Unit (GHz)    |    Node F   |   Node G  |
              +------------------+-------------+-----------+
              | Grid granularity | 6.25 (12.5) | 12.5 (25) |
              +------------------+-------------+-----------+
              |   Tuning range   | [12.5, 100] | [25, 200] |
              +------------------+-------------+-----------+

        Figure 3 An example of flexible-grid capability negotiation

3.3. Summary

   In summary, in a DWDM Link between two nodes, the following
   properties can be negotiated:


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   o Grid capability: flexible grid or fixed grid DWDM.

   o Central frequency granularity: a multiplier of 6.25 GHz.

   o Slot width granularity: a multiplier of 12.5 GHz.

   o Slot width tuning range: two multipliers of 12.5GHz, each
      indicate the minimal and maximal slot width supported by a port
      respectively.



4. LMP extensions

4.1. Grid Property Subobject

   According to [RFC4204], the LinkSummary message is used to verify
   the consistency of the link property on both sides of the link
   before it is brought up. The LinkSummary message contains negotiable
   and non-negotiable DATA_LINK objects, carrying a series of variable-
   length data items called subobjects, which illustrate the detailed
   link properties. The subobjects are defined in Section 12.12.1 in
   [RFC4204].

   To solve the problems stated in section 3, this draft extends the
   LMP protocol by introducing a new DATA_LINK subobject called "Grid
   property", allowing the grid property correlation between adjacent
   nodes.  The encoding format of this new subobject 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    |            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Grid  | C.F.G |     S.W.G     |      Min      |      Max      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type=TBD, Grid property type.

   Grid:

   The value is used to represent which grid the node/interface
   supports. Values defined in [RFC6205] identify DWDM [G.694.1] and
   CWDM [G.694.2]. The value defined in [I-D.farrkingel-ccamp-
   flexigrid-lambda-label] identifies flexible DWDM.

      +---------------+-------+
      | Grid          | Value |


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      +---------------+-------+
      | Reserved      |   0   |
      +---------------+-------+
      | ITU-T DWDM    |   1   |
      +---------------+-------+
      | ITU-T CWDM    |   2   |
      +---------------+-------+
      | Flexible DWDM |   3   |
      +---------------+-------+
      | Future use    |  4-16 |
      +---------------+-------+


   C.F.G (central frequency granularity):

   For a fixed-grid node/interface, the C.F.G value is used to
   represent the channel spacing, as the spacing between adjacent
   channels is constant. For a flexible-grid node/interface, this field
   should be used to represent the central frequency granularity which
   is the multiple of 6.25 GHz.

      +------------+-------+
      | C.F.G (GHz) | Value |
      +------------+-------+
      | Reserved   |   0   |
      +------------+-------+
      | 100        |   1   |
      +------------+-------+
      | 50         |   2   |
      +------------+-------+
      | 25         |   3   |
      +------------+-------+
      | 12.5       |   4   |
      +------------+-------+
      | 6.25       |   5   |
      +------------+-------+
      | Future use |  6-15 |
      +------------+-------+


   S.W.G (Slot Width Granularity):

   It is a positive integer value which indicates the slot width
   granularity which is the multiple of 12.5 GHz.

   Min & Max:

   Min & Max indicate the slot width tuning range the interface
   supports (as defined in section 2). For example, for slot width


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   tuning range from 25 GHz to 100 GHz (with regard to a node with slot
   width granularity of 12.5 GHz), the values of Min and Max should be
   2 and 8 respectively. For fixed-grid nodes, these two fields are
   meaningless and should be set to zero.

5. Messages Exchange Procedure

5.1. Flexi-fixed Grid Nodes Messages Exchange

   To demonstrate the procedure of grid property correlation, the model
   shown in Figure 1 is reused. Node B starts sending messages.

   o After inspecting its own node/interface property, node B sends
      node C a LinkSummary message including the MESSAGE ID, TE_LINK ID
      and DATA_LINK objects.  The setting and negotiating of MESSAGE ID
      and TE_link ID can be referenced to [RFC4204].  As node B
      supports flexible-grid property, the Grid and C.S. values in the
      grid property subobject are set to be 3 and 5 respectively.  The
      slot width tuning range is from 12.5 GHz to 200 GHz.  Meanwhile,
      the N bit of the DATA_LINK object is set to 1, indicating that
      the property is negotiable.

   o When node C receives the LinkSummary message from B, it checks
      the Grid, C.S., Min and Max values in the grid property subobject.
      Node C can only support fixed-grid DWDM and realizes that the
      flexible-grid property is not acceptable for the link. Since the
      receiving N bit in the DATA_LINK object is set, indicating that
      the Grid property of B is negotiable, node C responds to B with a
      LinkSummaryNack containing a new Error_code object and state that
      the property needs further negotiation.  Meanwhile, an accepted
      grid property subobject (Grid=2, C.S.=2, fixed DWDM with channel
      spacing of 50 GHz) is carried in LinkSummaryNack message.  At
      this moment, the N bit in the DATA_LINK object is set to 0,
      indicating that the grid property subobject is non-negotiable.

   o As the channel spacing and slot width of node B can be configured
      to be any integral multiples of 6.25 GHz and 12.5 GHz
      respectively, node B supports the fixed DWDM values announced by
      node C. Consequently, node B will resend the LinkSummary message
      carrying the grid property subobject with values of Grid=2 and
      C.S.=2.

   o Once received the LinkSummary message from node B, node C replies
      with a LinkSummaryACK message.  After the message exchange, the
      link between node B and C is brought up with a fixed channel
      spacing of 50 GHz.

   In the above mentioned grid property correlation scenario, the node
   supporting a flexible-grid is the one that starts sending LMP


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   messages.  The procedure where the initiator is the fixed-grid node
   is as follows:

   o After inspecting its own interface property, Node C sends B a
      LinkSummary message containing a grid property subobject with
      Grid=2, C.S.=2.  The N bit in the DATA_LINK object is set to 0,
      indicating that it is non-negotiable.

   o As the channel spacing and slot width of node B can be configured
      to be any integral multiples of 6.25 GHz and 12.5 GHz
      respectively, node B is able to support the fixed DWDM parameters.
      Then, node B will make appropriate configuration and reply node C
      the LinkSummaryACK message.

   o After the message exchange, the link between node B and C is
      brought up with a fixed channel spacing of 50 GHz.

5.2. Flexible Nodes Messages Exchange

   To demonstrate the procedure of grid property correlation between to
   flexi-grid capable nodes, the model shown in figure 3 is reused. The
   procedure of grid property correlation (negotiating the grid
   granularity and slot width tuning range) is similar to the scenarios
   mentioned above.

   o The Grid, C.S., Min and Max values in the grid property subobject
      sent from node F to G are set to be 3,5,1,8 respectively.
      Meanwhile, the N bit of the DATA_LINK object is set to 1,
      indicating that the grid property is negotiable.

   o When node G has received the LinkSummary message from F, it will
      analyze the Grid, C.S., Min and Max values in the Grid property
      subobject. But node G can only support grid granularity of 12.5
      GHz and a slotwdith tuning range from 25 GHz to 200 GHz.
      Considering the property of node F, node G then will respond F a
      LinkSummaryNack containing a new Error_code object and state that
      the property need further negotiation.  Meanwhile, an accepted
      grid property subobject (Grid=3, C.S.=4, Min=1, Max=4, the slot
      width tuning range is set to the intersection of Node F and G) is
      carried in LinkSummaryNack message.  Meanwhile, the N bit in the
      DATA_LINK object is set to 1, indicating that the grid property
      subobject is non-negotiable.

   o As the channel spacing and slot width of node F can be configured
      to be any integral multiples of 6.25 GHz and 12.5 GHz
      respectively, node F can support the lager granularity. The
      suggested slot width tuning range is acceptable for node F. In
      consequence, node F will resend the LinkSummary message carrying
      the grid subobject with values of Grid=3, C.S.=4, Min=1 and Max=4.


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   o Once received the LinkSummary message from node F, node G replies
      with a LinkSummaryACK message.  After the message exchange, the
      link between node F and G is brought up supporting central
      frequency granularity of 12.5 GHz and slot width tuning range
      from 25 GHz to 100 GHz.

   From the perspective of the control plane, once the links have been
   brought up, wavelength constraint information can be advertised and
   the wavelength label can be assigned hop-by-hop when establishing a
   LSP based on the link grid property.



6. Security Considerations

   TBD.

7. IANA Considerations

   TBD.

8. References

8.1. Normative references

   [G.694.1] International Telecommunications Union, "Spectral grids
             for WDM applications: DWDM frequency grid", Recommendation
             G.694.1, June 2002.

   [G.694.2] International Telecommunications Union, "Spectral grids
             for WDM applications: CWDM wavelength grid",
             Recommendation G.694.2, December 2003.

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

   [RFC4204] Lang, J., "Link Management Protocol (LMP)", RFC 4204,
             October 2005.

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








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8.2. Informative References

   [I-D.farrkingel-ccamp-flexigrid-lambda-label]
             Farrel, A., King, D., Li, Y., Zhang, F.,
             "Generalized Labels for the Flexi-Grid in Lambda-Switch-
             Capable (LSC) Label Switching Routers", draft-farrkingel-
             ccamp-flexigrid-lambda-label-08 (work in progress),
             February 2014.

   [FLEX-FWK]
             Dios, O., Casellas, R., Zhang, F., Fu, X., Ceccarelli, D.,
             and I. Hussain, "Framework for GMPLS based control of
             Flexi-grid DWDM networks", draft-ietf-ccamp-flexi-grid-
             fwk-00 (work in progress), October 2013.



9. Authors' Address

      Yao Li (editor)

      ZTE

      Email: li.yao3@zte.com.cn



      Guoying Zhang (editor)

      China Academy of Telecom Research, MIIT

      Email: zhangguoying@catr.cn



      Xihua Fu (editor)

      ZTE

      Email: fu.xihua@zte.com.cn



      Ramon Casellas

      CTTC

      Email: ramon.casellas@cttc.es



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      Yu Wang

      China Academy of Telecom Research, MIIT

      Email: wangyu@catr.cn



10. Contributors' Address

      Wenjuan He (editor)

      ZTE

      Email: he.wenjuan1@zte.com.cn



































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