Network Working Group                                       Fatai Zhang
Internet-Draft                                               Xian Zhang
Intended status: Standards Track                                 Huawei
                                                          Adrian Farrel
                                                     Old Dog Consulting
                                                 Oscar Gonzalez de Dios
                                                          D. Ceccarelli
Expires: May 12, 2014                                 November 12, 2013

        RSVP-TE Signaling Extensions in support of Flexible Grid



   This memo describes the extensions to RSVP-TE signaling to support
   Label Switched Paths in a GMPLS-controlled network that includes
   devices using the new flexible optical grid.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   This Internet-Draft will expire on May 12, 2014.

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Table of Contents

   1. Introduction ................................................ 2
   2. Terminology ................................................. 3
      2.1. Conventions used in this document .......................3
   3. Requirements for Flexible Grid Signaling .....................3
      3.1. Slot Width ............................................. 4
      3.2. Frequency Slot ......................................... 4
   4. Protocol Extensions ......................................... 5
      4.1. Traffic Parameters...................................... 5
         4.1.1. Applicability to Fixed Grid Networks ...............6
      4.2. Generalized Label....................................... 6
      4.3. Signaling Procedures.................................... 6
   5. IANA Considerations ......................................... 7
      5.1. RSVP Objects Class Types................................ 7
   6. Manageability Considerations................................. 7
   7. Security Considerations...................................... 7
   8. References .................................................. 8
      8.1. Normative References.................................... 8
      8.2. Informative References.................................. 8
   9. Contributors' Address........................................ 8
   10. Authors' Addresses ..........................................9

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 use different central frequencies and occupy
   a fixed bandwidth of frequency.

   Fixed grid channel spacing is selected from 12.5 GHz, 25 GHz, 50 GHz,
   100 GHz and integer multiples of 100 GHz. But [G.694.1] also defines
   "flexible grids", 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 introduced to define a flexible grid.

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

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   [RFC6163] provides a framework for GMPLS and Path Computation
   Element (PCE) control of Wavelength Switched Optical Networks
   (WSONs), and [WSON-SIG] describes the requirements and protocol
   extensions for signaling to set up Label Switched Paths (LSPs) in

   This document describes the additional requirements and protocol
   extensions for signaling to set up LSPs in networks that support the

2. Terminology

   For terminology related to flexi-grid, please refer to [FLEX-FWK]
   and [G.694.1].

2.1. Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC-2119 [RFC2119].

3. Requirements for Flexible Grid Signaling

   The architecture for establishing LSPs in a flexi-grid network is
   described in [FLEX-FWK].

   A optical spectrum LSP occupies a specific frequency slot, i.e. a
   range of frequencies. The process of computing a route and the
   allocation of a frequency slot is referred to as RSA (Routing and
   Spectrum Assignment). [FLEX-FWK] describes three types of
   architecture approaches to RSA: combined RSA, separated RSA and
   distributed SA. The first two approaches are referred to as
   "centralized SA", because both routing and spectrum (frequency slot)
   assignment are performed by centralized entity before the signaling

   In the case of centralized SA, the assigned frequency slot is
   specified in the Path message during LSP setup. In the case of
   distributed SA, the 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 [FLEX-FWK].

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   The remainder of this section states the additional requirements for
   signaling in a flexi-grid network.

3.1. Slot Width

   The slot width is an end-to-end parameter representing how much
   frequency resource is requested for a flexi-grid LSP. It is
   equivalent of optical bandwidth, although the amount of bandwidth
   associated with a slot width will depend on the encoding.

   Different LSPs may request different amounts of frequency resource
   in flexible grid networks, so the slot width needs to be carried in
   the signaling message during LSP establishment. This enables the
   nodes along the LSP to know how much frequency resource has been
   requested (in a Path message) and has been allocated (by a Resv
   message) for the LSP.

3.2. Frequency Slot

   The frequency slot information identifies which part of the
   frequency spectrum is allocated on each link for a flexi-LSP.

   This information is required in Resv message to indicate, hop-by-hop,
   the central frequency of the allocated resource. In combination with
   the slot width indicated in a Resv message (see Section 3.1) the
   central frequency carried in a Resv message identifies the resources
   reserved for the LSP (known as the frequency slot).

   The frequency slot can be represented by the two parameters as

      Frequency slot = [(central frequency) - (slot width)/2] ~
                       [(central frequency) + (slot width)/2]

   As is common with other resource identifiers (i.e., labels) in GMPLS
   signaling, it must be possible for the head-end LSP to suggest or
   require the central frequency to be used for the LSP. Furthermore,
   for bidirectional LSPs, the Path message must be able to specify the
   central frequency to be used for reverse direction traffic.

   As described in [G.694.1], the allowed frequency slots for the
   flexible DWDM grid have a nominal central frequency (in THz) defined

   193.1 + n * 0.00625

   where n is zero or a positive or negative integer.

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   The slot width (in GHz) is defined as:

   12.5 * m

   where m is a positive integer.

   It is possible that implementing a subset of the possible slot
   widths and central frequencies are supported. For example, an
   implementation could built where the nominal central frequency
   granularity is 12.5 GHz (by only requiring values of n that are even)
   and that only supports slot widths as a multiple of 25 GHz (by only
   allowing values of m that are even).

   Further details can be found in [FLEX-FWK].

4. Protocol Extensions

   This section defines the extensions to RSVP-TE signaling for GMPLS
   [RFC3473] to support flexible grid networks.

4.1. Traffic Parameters

   In RSVP-TE, the SENDER_TSPEC object in the Path message indicates
   the requested resource reservation. The FLOWSPEC object in the Resv
   message indicates the actual resource reservation.

   As described in Section 3.1, the slot width represents how much
   frequency resource is requested for a flexi-grid LSP. That is, it
   describes the end-to-end traffic profile of the LSP. Therefore, the
   traffic parameters for a flexi-grid LSP encode the slot width.

   This document defines new C-Types for the SENDER_TSPEC and FLOWSPEC
   objects to carry Spectrum Switched Optical Network (SSON) traffic

   SSON SENDER_TSPEC: Class = 12, C-Type = TBD1.

   SSON FLOWSPEC: Class = 9, C-Type = TBD2.

   The SSON traffic parameters carried in both objects have the same
   format as shown in Figure 1.

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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
   |     m         |                      Reserved                 |

                   Figure 1: The SSON Traffic Parameters

   m (8 bits): the slot width is specified by m*12.5 GHz.

   The Reserved bits MUST be set to zero and ignored upon receipt.

4.1.1. Applicability to Fixed Grid Networks

   Note that the slot width (i.e., traffic parameters) of a fixed grid
   defined in [G.694.1] can also be specified by using the SSON traffic
   parameters. The fixed grid channel spacings (12.5 GHz, 25 GHz, 50
   GHz, 100 GHz and integer multiples of 100 GHz) are also the multiple
   of 12.5 GHz, so the m parameter can be used to represent these slot

   Therefore, it is possible to consider using the new traffic
   parameter object types in common signaling messages for flexi-grid
   and legacy DWDM networks.

4.2. Generalized Label

   In the case of a flexible grid network, the labels that have been
   requested or allocated as signaled in the RSVP-TE objects are
   encoded as described in [FLEX-LBL]. This new label encoding can
   appear in any RSVP-TE object or sub-object that can carry a label.

   As noted in Section 4.2 of [FLEX-LBL], the m parameter forms part of
   the label as well as part of the traffic parameters.

4.3. Signaling Procedures

   There are no differences between the signaling procedure described
   for LSP control in [FLEX-FWK] and those required for use in a fixed-
   grid network [WSON-SIG]. Obviously, the TSpec, FlowSpec and label
   formats described in Section 3 are used. The signaling procedures
   for distributed SA and centralized SA can be applied.

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5. IANA Considerations

5.1. RSVP Objects Class Types

   This document introduces two new Class Types for existing RSVP
   objects. IANA is requested to make allocations from the "Resource
   ReSerVation Protocol (RSVP) Parameters" registry using the "Class
   Names, Class Numbers, and Class Types" sub-registry.

       Class Number  Class Name                            Reference
       ------------  -----------------------               ---------
       9             FLOWSPEC                              [RFC2205]

                     Class Type (C-Type):

                     (TBD2) SSON FLOWSPEC                   [This.I-D]

       Class Number  Class Name                            Reference
       ------------  -----------------------               ---------
       12            SENDER_TSPEC                          [RFC2205]

                     Class Type (C-Type):

                     (TBD1) SSON SENDER_TSPEC               [This.I-D]

   IANA is requested to assign the same value for TBD1 and TBD2, and a
   value of 8 is suggested.

6. Manageability Considerations

   This document makes minor modifications to GMPLS signaling, but does
   not change the manageability considerations for such networks.
   Clearly, protocol analysis tools and other diagnostic aids
   (including logging systems and MIB modules) will need to be enhanced
   to support the new traffic parameters and label formats.

7. Acknowledgments

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

8. Security Considerations

   This document introduces no new security considerations to [RFC3473].

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9. References

9.1. Normative References

   [RFC2119] S. Bradner, "Key words for use in RFCs to indicate
             requirements levels", RFC 2119, March 1997.

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

   [G.694.1] ITU-T Recommendation G.694.1 (revision 2), "Spectral grids
             for WDM applications: DWDM frequency grid", February 2012.

   [FLEX-LBL]King, D., Farrel, A. and Y. Li, "Generalized Labels for
             the Flexi-Grid in Lambda Switched Capable (LSC) Label
             Switching Routers", draft-farrkingel-ccamp-flexigrid-
             lambda-label, work in progress.

9.2. Informative References

   [RFC2205] Braden, R., Zhang L., Berson, S., Herzog, S. and S. Jamin,
             "Resource ReServation Protocol (RSVP) - Version 1,
             Functional Specification', RFC2205, September 1997.

   [RFC6163] Y. Lee, G. Bernstein and W. Imajuku, "Framework for GMPLS
             and Path Computation Element (PCE) Control of Wavelength
             Switched Optical Networks (WSONs)", RFC 6163, April 2011.

   [FLEX-FWK] Gonzalez de Dios, O,, Casellas R., Zhang, F., Fu, X.,
             Ceccarelli, D., and I. Hussain, "Framework and
             Requirements for GMPLS based control of Flexi-grid DWDM
             networks', draft-ogrcetal-cammp-flexi-grid-fwk, work in

   [WSON-SIG] G. Bernstein, Sugang Xu, Y. Lee, G. Martinelli and
             Hiroaki Harai, "Signaling Extensions for Wavelength
             Switched Optical Networks", draft-ietf-ccamp-wson-
             signaling, work in progress.

10. Contributors' Address

   Ramon Casellas
   Av. Carl Friedrich Gauss n7
   Castelldefels, Barcelona 08860

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   Felipe Jimenez Arribas
   Telefonica Investigacion y Desarrollo
   Emilio Vargas 6
   Madrid,   28045

   Yi Lin
   Huawei Technologies Co., Ltd.
   F3-5-B R&D Center, Huawei Base,
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28972914

11. Authors' Addresses

   Fatai Zhang
   Huawei Technologies

   Xian Zhang
   Huawei Technologies

   Adrian Farrel
   Old Dog Consulting

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

   Phone: +34 913374013

   Daniele Ceccarelli
   Via A. Negrone 1/A

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   Genova - Sestri Ponente

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