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Versions: (draft-li-ccamp-grid-property-lmp) 00 01 02 03 04

Network Working Group                                       Q. Wang, Ed.
Internet-Draft                                                       ZTE
Intended status: Standards Track                           G. Zhang, Ed.
Expires: March 26, 2017                                            CAICT
                                                                   Y. Li
                                                      Nanjing University
                                                             R. Casellas
                                                                    CTTC
                                                                 Y. Wang
                                                                   CAICT
                                                      September 22, 2016


   Link Management Protocol Extensions for Grid Property Negotiation
                 draft-ietf-ccamp-grid-property-lmp-04

Abstract

   ITU-T [G.694.1] introduces 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.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 26, 2017.

Copyright Notice

   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   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
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Requirements for Grid Property Negotiation  . . . . . . . . .   3
     3.1.  Flexi-fixed Grid Nodes Interworking . . . . . . . . . . .   3
     3.2.  Flexible-Grid Capability Negotiation  . . . . . . . . . .   4
     3.3.  Summary . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Application of Grid Property Negotiation  . . . . . . . . . .   5
   5.  LMP extensions  . . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Grid Property Subobject . . . . . . . . . . . . . . . . .   6
   6.  Messages Exchange Procedure . . . . . . . . . . . . . . . . .   7
     6.1.  Flexi-fixed Grid Nodes Messages Exchange  . . . . . . . .   7
     6.2.  Flexible Nodes Messages Exchange  . . . . . . . . . . . .   9
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  10
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   10. Contributing Authors  . . . . . . . . . . . . . . . . . . . .  10
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     11.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   ITU-T [G.694.1] introduces 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 100Gbit/s transport systems.




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   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 [RFC7698].  This document describes the
   extensions to the Link Management Protocol (LMP) to negotiate a link
   grid property between two adjacent 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 [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 definition of nominal central frequency, nominal central
   frequency granularity, slot width and slot width granularity can be
   referred to [RFC7698].

   In this contribution, some definitions are listed below except those
   defined in [RFC7698]:

   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



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   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: Interworking between flexible and fixed-grid nodes

             ^               ^               ^               ^
     ------->|<----50GHz---->|<----50GHz---->|<----50GHz---->|<------
       ..... |               |               |               | .....
     +-------+-------+-------+-------+-------+--------+------+-------+-
  n=-2              -1               0                1              2
                       Fixed channel spacing of 50 GHz (Node C)
             ^               ^               ^               ^
             |               |               |               |
     --------+---------------+---------------+---------------+---------
       ..... |  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: Fixed grid 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 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.  Taking node G in figure 3 as an 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)
   requiring slot widths being multiple of 25 GHz (the values of m
   SHOULD be even).  Therefore the link between two optical node F and G
   with different grid granularity must be configured to align with the



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   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: Flexible-grid capability negotiation

   Note: we should avoid the use of LMP in the case that a DWDM or Flex
   port is connected to a CWDM port, for this it is likely to cause the
   upgrade of hardware and LMP can not work in a "plug-and-play" way.

3.3.  Summary

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

   o Grid capability: flexible grid or fixed grid DWDM.

   o Nominal 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.

   And for ports on a link that do not have any grid properties in
   common, the link and its properties SHOULD not be advertised.

4.  Application of Grid Property Negotiation

   As described in [RFC7698], the control plane MAY include support for
   neighbor discovery such that a flexi-grid network can be constructed
   in a "plug-and-play" manner.  The control plane SHOULD allow the
   nodes at opposite ends of a link to correlate the properties that



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   they will apply to the link.  Such a correlation SHOULD include at
   least the identities of the nodes and the identities that they apply
   to the link.  As described in this draft, for ports on a link that do
   not have any grid properties in common, the link and its properties
   SHOULD not be advertised to the PCE or other nodes in the same
   domain.  Especially in the scenario of inter-domain, LMP can not be
   replaced by some other protocol.  For example, if Path Computation
   Element (PCE) or a serial of PCEs coordinate to compute an end-to-end
   path which crosses more than one domain, it should take the inter-
   domain grid properties into consideration.  Given the OSPF can not
   advertise the attributes of the border device on the other side, the
   inter-domain attributes must be negotiated in advance, otherwise the
   end-to-end path may not be set up successfully.

5.  LMP extensions

5.1.  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 13.12.1 in
   [RFC4204].

   To meet the requirements 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    | Grid  | C.F.G |     S.W.G     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Min Width   |    Reserved   |           Max Width           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 4

   Type=TBD, Grid property type.

   Grid: 4 bits

   The value is used to represent which grid the node/interface
   supports.  Values defined in RFC 6205 [RFC6205] identify DWDM




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   [G.694.1] and CWDM [G.694.2].  The value defined in [RFC7699]
   identifies flexible DWDM.

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

   C.F.G (central frequency granularity):

   It is a positive integer.  Its value indicates the multiple of 6.25
   GHz in terms of central frequency granularity.

   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 Width and Max Width:

   Min Width and Max Width are positive integers.  Their value indicate
   the multiple of 12.5 GHz in terms of the slot width tuning range the
   interface supports.  For example, for slot width 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 Width and Max Width should be 2 and 8
   respectively.  For fixed-grid nodes, these two fields are meaningless
   and should be set to zero.

6.  Messages Exchange Procedure

6.1.  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



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   flexible-grid property, the Grid and C.F.G values in the grid
   property subobject are set to be 3 (i.e., ITU-T Flex) and 1
   (i.e.,1*6.25GHz) respectively.  The slot width tuning range is from
   12.5 GHz to 200 GHz (i.e., Min Width=1, Max Width=16).  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.F.G, 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 of the
   interface connected to node B needs further negotiation.  Meanwhile,
   an accepted grid property subobject (Grid=2, C.F.G=4, 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 the corresponding
   interface 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.F.G=4.

   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
   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.F.G=4.  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




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

6.2.  Flexible Nodes Messages Exchange

   To demonstrate the procedure of grid property correlation between two
   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.F.G, Min and Max values in the grid property subobject
   sent from node F to G are set to be 3,1,1,8 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.F.G, Min and Max values in the Grid property
   subobject.  But the corresponding interface of node G can only
   support grid granularity of 12.5 GHz and a slotwdith tuning range
   from 25 GHz to 200 GHz.  Considering the interface property of node
   F, node G will first match these property with its corresponding
   interface, and then judge the mismatch of the property of the link
   between node F and G, then 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.F.G=2, Min=2, Max=8, 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 the corresponding
   interface 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.F.G=2, Min=2 and
   Max=8.

   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




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   the wavelength label can be assigned hop-by-hop when establishing a
   LSP based on the link grid property.

7.  IANA Considerations

   This draft introduces the following new assignments:

   LMP Sub-Object Class names:

   o under DATA_LINK Class name (as defined in [RFC4204])

   - Grid property type (sub-object Type = TBD.)

8.  Acknowledgments

   This work was supported in part by the China NSFC Project 61201260.

9.  Security Considerations

   LMP message security uses IPsec, as described in [RFC4204].  This
   document only defines new LMP objects that are carried in existing
   LMP messages.  As such, this document introduces no other new
   security considerations not covered in [RFC4204].

10.  Contributing Authors

      Wenjuan He
      ZTE
      he.wenjuan1@zte.com.cn


11.  References

11.1.  Normative References

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

   [G.694.2]  International Telecomunications 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,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.




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   [RFC4204]  Lang, J., Ed., "Link Management Protocol (LMP)", RFC 4204,
              DOI 10.17487/RFC4204, October 2005,
              <http://www.rfc-editor.org/info/rfc4204>.

   [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,
              <http://www.rfc-editor.org/info/rfc6205>.

11.2.  Informative References

   [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,
              <http://www.rfc-editor.org/info/rfc7698>.

   [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, <http://www.rfc-editor.org/info/rfc7699>.

Authors' Addresses

   Qilei Wang (editor)
   ZTE

   Email: wang.qilei@zte.com.cn


   Guoying Zhang (editor)
   CAICT

   Email: zhangguoying@catr.cn


   Yao Li
   Nanjing University

   Email: wsliguotou@hotmail.com


   Ramon Casellas
   CTTC

   Email: ramon.casellas@cttc.es




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   Yu Wang
   CAICT

   Email: wangyu@catr.cn















































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