RSVP-TE Signaling Extensions in support of Flexible Grid
draft-zhang-ccamp-flexible-grid-rsvp-te-ext-00

Network Working Group                                       Fatai Zhang 
Internet-Draft                                                   Huawei 
Intended status: Standards Track                 Oscar Gonzalez de Dios 
                                                             Telefonica 
                                                          D. Ceccarelli 
                                                               Ericsson 
Expires: April 16, 2012                                October 16, 2011 
                                      

                                    
        RSVP-TE Signaling Extensions in support of Flexible Grid  
                                      
             draft-zhang-ccamp-flexible-grid-rsvp-te-ext-00.txt 

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   This Internet-Draft will expire on April 16, 2012. 

    

   Abstract 

   This memo describes the signaling extensions of GMPLS control of 
   flexible grid network.  

 
 
 
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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]. 

Table of Contents 

    
   1. Introduction ................................................. 2 
   2. Requirements for Flexible Grid Signaling ..................... 3 
      2.1. Slot Width .............................................. 3 
      2.2. Frequency Slot .......................................... 3 
   3. Extensions ................................................... 4 
      3.1. WSON Traffic Parameters ................................. 5 
      3.2. Generalized Label ....................................... 5 
      3.3. Signaling Procedures .................................... 7 
         3.3.1. Distributed SA ..................................... 7 
         3.3.2. Centralized SA ..................................... 8 
   4. IANA Considerations .......................................... 8 
   5. Security Considerations ...................................... 8 
   6. References ................................................... 8 
   7. Authors' Addresses ........................................... 9 
    
    

1. Introduction 

   [G.694.1v1] defines the DWDM frequency grids for 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, i.e. the frequency spacing 
   between two allowed nominal central frequencies can be 12.5 GHz, 25 
   GHz, 50 GHz, 100 GHz and integer multiples of 100 GHz as defined in 
   [G.694.1v1]. All of the wavelengths on a fiber SHALL use different 
   central frequencies and occupy a fixed bandwidth of frequency.  

   [G.FLEXIGRID], an updated version of [G.694.1v1] will be consented 
   in December 2011 in support of flexible grids. 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 flexible grid. A channel is represented as 
   an LSC (Lambda Switching Capable) LSP in the control plane and 
   SHOULD occupy a frequency slot on each fiber it traverses. In the 
   case of flexible grid, the different LSC LSPs may have different 
   slot width on a fiber, i.e. the slot width is flexible on a fiber.  
 
 
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   [WSON-SIG] describes the requirements and extensions for WSON 
   signaling. It focuses on the fixed grids control. This document 
   describes the additional requirements and extensions for signaling 
   control brought by flexible grids.  

2. Requirements for Flexible Grid Signaling   

   An LSC LSP SHOULD occupy a frequency slot, i.e. a range of frequency. 
   The route computation and frequency slot assignment could be called 
   RSA (Routing and Spectrum Assignment).  

   [FLEXIGRID-REQ] describes three types of architecture approaches to 
   RSA, which are: combined RSA, separated RSA and distributed SA. In 
   the case of combined RSA and separated RSA, both the routing and the 
   spectrum (frequency slot) are provided by the RSA algorithm before 
   the signaling procedure. It could be called "centralized SA". In the 
   case of distributed SA, only the route is provided before the 
   signaling procedure and the spectrum assignment is done during the 
   signaling procedure.  

   In the case of centralized SA, the frequency slot SHOULD be 
   specified in the Path message. In the case of distributed SA, the 
   slot width of the LSC LSP SHOULD be specified in the Path message 
   for the purpose of frequency slot assignment.  

   Similar to fixed grid network, if there is no wavelength converter 
   in an optical network, there is "wavelength continuity constraint" 
   of a LSC LSP which is described as section 4 of [RFC 6163].  

2.1. Slot Width  

   The slot width is an end-to-end parameter representing how much 
   spectrum resource is requested for a LSC LSP. Since different LSPs 
   may request different amounts of spectrum portion in flexible grid 
   networks, the slot width SHOULD be carried in the signaling message, 
   so that all the nodes along the LSP can know how much spectrum 
   portion will be allocated for the LSP.  

2.2. Frequency Slot  

   The frequency slot information represents which part of the spectrum 
   portion is allocated on each link for an LSC LSP. This information 
   SHOULD be carried hop-by-hop in signaling message so that each node 
   can indicate its neighbor the resource reservation on the link 
   between them. 
 
 
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   The frequency slot can be represented by the two parameters: central 
   frequency and slot width, as follows:  

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

   Since the slot width information is carried in the signaling message 
   (as described in Section 2.1), also the central frequency parameter 
   SHOULD be carried in the signaling message for frequency slot 
   determination. 

   Figure 1 shows an example of two LSC LSPs traversing a link and 
   illustrates how to determine the frequency slot based on the central 
   frequency and slot width information.  

                         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 = 193.1THz    Central F = 193.14375 THz 
                     Slot width = 25 GHz    Slot width = 37.5 GHz 
    
                  Figure 1 - Two LSC LSPs traverse a Link  
                                      
   The two wavelengths shown in figure 1 have the following meaning:  

   LSC LSP 1: central frequency = 193.1 THz, slot width = 25 GHz. It 
   means the frequency slot [193.0875 THz, 193.1125 THz] is assigned to 
   this LSC LSP.  

   LSC LSP 2: central frequency = 193.14375 THz, slot width = 37.5 GHz. 
   It means the frequency slot [193.125 THz, 193.1625 THz] is assigned 
   to this LSC LSP.  

   Note that the frequency slots of two LSC LSPs on a fiber MUST NOT 
   overlap with each other.  

3. Extensions  

   This section defines the extensions of signaling for flexible grid.  

 
 
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3.1. WSON Traffic Parameters  

   As described in Section 2, the slot width represents how much 
   spectrum resource is requested for an LSC LSP, i.e., it describes 
   the end-to-end traffic profile of the LSP. Therefore, the slot width 
   SHOULD be regarded as a traffic parameter for an LSC LSP.  

   The WSON traffic parameters are organized 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  
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+  
   |     m         |                      Reserved                 | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
    

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

   Note that the slot width of fixed grid defined in [G.694.1v1] can be 
   also specified by m because the defined channel spacing (12.5 GHz, 
   25 GHz, 50 GHz, 100 GHz and integer multiples of 100 GHz) are also 
   the multiple of 12.5 GHz. Therefore, the traffic parameters are 
   general for WSON including both fixed grid and flexible grid. 

   The WSON traffic parameters SHOULD be carried in SENDER_TSPEC or 
   FLOWSPEC objects:  

   WSON SENDER_TSPEC: Class = 12, C-Type = to be assigned by IANA, 
   preferred 8.  

   WSON FLOWSPEC: Class = 9, C-Type = to be assigned by IANA, preferred 
   8.  

3.2. Generalized Label  

   In the case of flexible grid, the allowed central frequency is 
   calculated as follows:  

               Central Frequency = (193.1 + n * 0.00625) THz  

   Where n is a two's-complement integer (positive, negative, or 0).  

   The Label object is used to indicate the resource reserved on a link. 
   In Flexible Grid networks, it is used to indicate which frequency 
   slot is allocated on a link for the given LSC LSP.  

 
 
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   Since the frequency slot assigned to an LSC LSP can be determined by 
   the combination of [central frequency, slot width], while the slot 
   width of an LSC LSP is specified in the traffic parameters, the 
   Label object just needs to carry the assigned central frequency. 
   Therefore, the wavelength label format defined in [RFC6205] can be 
   reused to specify the central frequency of an LSC LSP, without any 
   change on the label format.  

    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 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
   |Grid | C.S.  |    Identifier   |                n              | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 
     
   The meaning of Grid, Identifier and n fields are not changed. The 
   usage of the label format is also not changed.  

   According to [G.FLEXIGRID], flexible grid still belongs to DWDM, so 
   there is no need to introduce a new type of Grid, i.e., Grid=1 (ITU-
   T DWDM) SHOULD be used for flexible grid.  

   In case of Grid=1 (ITU-T DWDM), a new value of C.S. is defined for 
   flexible 6.25 GHz grid. The C.S.(Channel Spacing) field is defined 
   as follows:  

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

 
 
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   The value for flexible 6.25 GHz is to be assigned by IANA, preferred 
   5.  

3.3. Signaling Procedures  

   This section describes the signaling procedures for distributed SA 
   and centralized SA (See [FLEXIGRID-REQ]).   

3.3.1. Distributed SA  

   In this case, only the route is provided by a PCE or ingress node 
   before the signaling procedure. The available central frequencies 
   will be collected hop by hop and the egress node SHOULD select a 
   proper central frequency for the LSP.  

   After the route is computed, the ingress node SHOULD find out the 
   available central frequencies for the LSP on the next link of the 
   route. If the frequency slot which is determined by a central 
   frequency and slot width of the LSC LSP (See section 2.2) does not 
   overlap with the existing LSC LSPs, the central frequency is 
   considered to be available for the requesting LSC LSP.  

   Then a Path message is sent to the next node on the route. The Path 
   message MUST contain a Flexible Grid SENDER_TSPEC object to specify 
   the slot width of the LSC LSP. A LABEL_SET object SHALL be added to 
   the Path message, which contains the available central frequencies 
   for the LSP on the next link.  

   When an intermediate node receives a Path message, it can get the 
   slot width from the Flexible Grid SENDER_TSPEC object. Then it 
   SHOULD find the available central frequencies for the LSP on the 
   next link of the route similar to the ingress node. The common part 
   of the two available central frequency sets, i.e. the set received 
   from the Path message and the set of the next link, SHALL be 
   selected as the new available central frequency set for the LSP. If 
   the new set is null, the Path message SHALL be rejected by a PathErr 
   message. Otherwise, the LABEL SET object in the Path message SHALL 
   be updated according to the new set and the Path message is 
   forwarded to the next node on the route.  

   When an egress node receives a Path message, it SHOULD select an 
   available central frequency from the LABEL SET object based on local 
   policy and determine the frequency slot based on the slot width and 
   the selected central frequency (See section 2.2). Then a Resv 
   message is responded so that the nodes along the LSP can establish 
   the optical cross-connect based on the frequency slot determined by 

 
 
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   the slot width in the traffic parameters and the central frequency 
   in the label.  

3.3.2. Centralized SA  

   In this case, both of the routing and frequency slot are provided by 
   PCE or ingress node. When signaling the LSP, the slot width is 
   carried in the traffic parameters, and the assigned central 
   frequency is carried in the Label ERO. When the nodes along the LSP 
   receive the Path message carrying these information, they can 
   determine the frequency slot by the slot width and the central 
   frequency and then establish the optical cross-connect based on the 
   central frequency. The procedures of ERO and Label ERO are the same 
   as described in [RFC3209] and [RFC3473]. 

4. IANA Considerations 

   TBD. 

5. Security Considerations 

   TBD. 

    
    
6. References 

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

   [G.694.1v1] ITU-T Recommendation G.694.1, Spectral grids for WDM 
             applications: DWDM frequency grid, June 2002. 

   [WSON-PCE] Y. Lee, G. Bernstein, Jonas Martensson, T. Takeda and T. 
             Tsuritani, "PCEP Requirements for WSON Routing and 
             Wavelength Assignment", draft-ietf-pce-wson-routing-
             wavelength-05, July 2011. 

   [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-02, September 2011.  

   [RFC3209] D. Awduche et al, "RSVP-TE: Extensions to RSVP for LSP 
             Tunnels", RFC3209, December 2001. 

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

   [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. 

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

   [FLEXIGRID-REQ] F.Zhang et al, "Requirements for GMPLS Control of 
             Flexible Grids",draft-zhang-ccamp-flexible-grid-
             requirements, in progress. 

   [G.FLEXIGRID] Draft revised G.694.1 version 1.3, Unpublished ITU-T           
             Study Group 15, Question 6. 

    

    

7. Authors' Addresses 

   Fatai Zhang
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28972912
   Email: zhangfatai@huawei.com

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

   Phone: +34 913374013
   Email: ogondio@tid.es

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   Felipe Jimenez Arribas
   Telefonica Investigacion y Desarrollo
   Emilio Vargas 6
   Madrid,   28045
   Spain
   Email: felipej@tid.es

   Daniele Ceccarelli
   Ericsson
   Via A. Negrone 1/A
   Genova - Sestri Ponente
   Italy
   Email: daniele.ceccarelli@ericsson.com

   Xiaobing Zi
   Huawei Technologies
   F3-5-B R&D Center, Huawei Base
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Phone: +86-755-28973229
   Email: zixiaobing@huawei.com

   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
   Email: yi.lin@huawei.com

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