Link Management Protocol Extensions for Grid Property Negotiation
draft-li-ccamp-grid-property-lmp-00

Network Working Group                                              Y. Li
Internet-Draft                                                       ZTE
Intended status: Standards Track                        January 21, 2012
Expires: July 24, 2012

   Link Management Protocol Extensions for Grid Property Negotiation
                  draft-li-ccamp-grid-property-lmp-00

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.

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   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
   3.  Problem statement  . . . . . . . . . . . . . . . . . . . . . .  3
     3.1.  Flexi-fixed Grid Nodes Interworking  . . . . . . . . . . .  3
     3.2.  Flexible Grid Capability Negotiation . . . . . . . . . . .  4
   4.  LMP extensions . . . . . . . . . . . . . . . . . . . . . . . .  5
     4.1.  Grid Property Subobject  . . . . . . . . . . . . . . . . .  5
   5.  Messages Exchange Procedure  . . . . . . . . . . . . . . . . .  7
     5.1.  Flexi-fixed Grid Nodes Messages Exchange . . . . . . . . .  7
     5.2.  Flexible Nodes Messages Exchange . . . . . . . . . . . . .  8
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     8.1.  Normative references . . . . . . . . . . . . . . . . . . .  9
     8.2.  Informative References . . . . . . . . . . . . . . . . . .  9
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10

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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.  Flexible grid network is
   composed of arbitrarily assigned spectral slots.  That is the
   adjacent channel spacing and spectral bandwidth per wavelength are
   variable.  Mixed bitrate transmission systems can allocate their
   channels with different spectral bandwidths so that they can be
   optimized for the bandwidth requirements of the particular bitrate
   and modulation scheme of the individual channels.  This technique is
   regarded to be a promising way to improve the network utilization
   efficiency and fundamentally reduce the cost of the core network.

   While during the practical deployment procedure, the fixed grid
   optical nodes will be replaced by the flexible nodes gradually.  This
   will lead to the problem of interworking between fixed grid DWDM and
   flexible grid DWDM nodes.  Besides, even two flexible grid optical
   nodes may have different grid properties, leading to link property
   conflict.  Therefore, 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 .

2.  Terminology

   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].

3.  Problem statement

3.1.  Flexi-fixed Grid Nodes Interworking

        +---+         +---+         +---+         +---+        +---+
        | A |---------| B |=========| C |=========| D +--------+ E |
        +---+         +---+         +---+         +---+        +---+

                                 figure 1

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      ^               ^               ^               ^               ^
      |               |               |               |               |
    __|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_|_
  n= -16 -14 -12 -10 -8  -6  -4  -2   0   2   4   6   8   10  12  14  16
                 Central frequency granularity=6.25 GHz (Node B,D)

      ^               ^               ^               ^               ^
      |               |               |               |               |
      |<----50GHz---->|<----50GHz---->|<----50GHz---->|<----50GHz---->|
    __|_______________|_______________|_______________|_______________|_

                   Fixed channel spacing of 50 GHz (Node C)

                                 figure 2

   Figure 1 shows an example of interworking between flexible and fixed
   grid nodes.  Node A, B, D, E support flexible grid.  All these nodes
   can support frequency slots with central frequency granularity of
   6.25 GHz and slotwidth granularity of 12.5 GHz.  At the same time,
   the channel spacing and slotwidth can be configured to integral
   multiple of 6.25 GHz and 12.5 GHz respectively.  As shown in figure
   2, they are backward compatible to the fixed grid situation (flexible
   frequency slot with channel spacing of 8*6.25 and slotwidth of 4*12.5
   GHz is equivalent to fixed-grid DWDM channel 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.

3.2.  Flexible Grid Capability Negotiation

                           +---+            +---+
                           | 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

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   Although the updated version of ITU-T [G.694.1] has defined the
   flexible grid with a nominal central frequency granularity of 6.25
   GHz and a slotwidth granularity of 12.5 GHz.  However, devices or
   applications that make use of the flexible grid may not have to be
   capable of supporting every possible slotwidth or position.  In other
   words, applications may be defined where different grid granularity
   can be supported.  For example, an application could be defined where
   the nominal central frequency granularity is 12.5 GHz and that only
   requires slotwidths as a multiple of 25 GHz.  Therefore the link
   between the two grid granularity nodes must be set to align with the
   larger one.  Besides, different nodes may have different slotwidth
   tuning ranges.  For example, in figure 3, node F can only support
   slotwidth 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
   slotwidth tuning range between F and G sholud be chosen as an
   intersection from 25 GHz to 100 GHz.

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.  LinkSummary message contains negotiable and non-
   negotiable DATA_LINK objects to carry a series of variable-length
   data items called subobjects to illustrate the detailed link
   properties.  The subobjects are defined in Section 12.12.1 in
   [RFC4204].

   To slove the problems stated in section 3, this draft extends the LMP
   by introducing a new DATA_LINK subobject called "Grid property" to
   support 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    |Grid |  C.S. |  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

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   CWDM [G.694.2].  Value defined in
   [I-D.farrkingel-ccamp-flexigrid-lambda-label] identifies flexible
   DWDM.

   +---------------+-------+
   | Grid          | Value |
   +---------------+-------+
   | Reserved      |   0   |
   +---------------+-------+
   | ITU-T DWDM    |   1   |
   +---------------+-------+
   | ITU-T CWDM    |   2   |
   +---------------+-------+
   | Flexible DWDM |   3   |
   +---------------+-------+
   | Future use    |  4-7  |
   +---------------+-------+

   C.S.:

   With respect to the fixed grid node/interface, the C.S. value is used
   to represent the channel spacing, as the spacing between adjacent
   channels is constant.  While, for flexible grid node/interface, this
   field should be used to represent the central frequency granularity.

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

   Min & Max:

   The slotwidth tuning range.  For example, with regarding to a node
   with central frequency granularity of 6.25 (slotwidth granularity of
   12.5 GHz) and slotwidth tuning range from 25 GHz to 100 GHz, the

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   values of Min and Max should be 2 and 8 respectively.  For fixed grid
   nodes, these two fields is meaningless and should be set to zeros.

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.  The LMP meessages start running from
   node B to node C.

   o  After inspecting its own node/interface property, node B will send
      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, C.S. value in the grid property
      subobject are set to be 3 and 5 respectively.  The slotwidth
      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 has received the LinkSummary message from B, it will
      analyze the Grid, C.S., Min and Max values in the grid property
      subobject.  But node C can only support fixed grid DWDM and
      recognize that flexible grid property is not acceptable for the
      link.  However, the receiving N bit in the DATA_LINK object is
      set, indicating that the Grid property of B is negotiable.  Then,
      node C will respond B a linkSummaryNack containing a new
      Error_code object and state that the property need 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 slotwidth of node B can be configured
      to be any integral multiples of 6.25 GHz and 12.5 GHz
      respectively, node B can be compatible to support the fixed DWDM
      values.  Then, node B will resend the LinkSummary message carrying
      the grid property subobject with values of Grid=2 and C.S.=2.
   o  Once receiving the LinkSummary message from node B, node C will
      reply with a LinkSummaryACK message.  After all these are done,
      the link between node B and C is brought up with a fixed channel
      spacing of 50 GHz.

   The above mentioned grid property correlation scenario starts sending
   message from flexible grid node to fixed grid node.  While for
   message from fixed grid node to flexible grid node, the procedure is
   as follows:

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   o  After inspecting its own interface property, Node C will send 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 slotwidth of node B can be configured
      to be any integral multiples of 6.25 GHz and 12.5 GHz
      respectively, node B can be compatible to support the fixed DWDM
      parameters.  Then, node B will make appropriate configuration and
      reply node C the LinkSummaryACK message.
   o  After all these are done, 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, the model
   shown in figure 3 is reused.  The procedure of grid property
   correlation (negotiating the grid granularity and slotwidth 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
      slotwidth 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 be compatible to support the lager
      granularity.  And the suggested slotwidth tuning range is
      acceptable for node F. Then, node F will resend the LinkSummary
      message carrying the grid subobject with values of Grid=3, C.S.=4,
      Min=1 and Max=4.
   o  Once receiving the LinkSummary message from node F, node G will
      reply with a LinkSummaryACK message.  After all these are done,
      the link between node F and G is brought up supporting central
      frequency granularity of 6.25 GHz and slotwidth tuning range from
      25 GHz to 100 GHz.

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

6.  IANA Considerations

   TBD

7.  Security 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.

8.2.  Informative References

   [I-D.farrkingel-ccamp-flexigrid-lambda-label]
              King, D., Farrel, A., Li, Y., Fei, Z., and R. Casellas,
              "Generalized Labels for the Flexi-Grid in Lambda-Switch-
              Capable (LSC) Label Switching Routers",
              draft-farrkingel-ccamp-flexigrid-lambda-label-01 (work in
              progress), October 2011.

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Author's Address

   Yao Li
   ZTE

   Email: li.yao3@zte.com.cn

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