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PCEP Extension for Distribution of Link-State and TE Information for Optical Networks
draft-lee-pce-pcep-ls-optical-11

Document Type Active Internet-Draft (individual)
Authors Young Lee , Haomian Zheng , Daniele Ceccarelli , Wei Wang , Peter Choongul Park , Bin-Yeong Yoon
Last updated 2022-03-07
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draft-lee-pce-pcep-ls-optical-11
PCE Working Group                                            Young Lee 
Internet Draft                                                 Samsung 
Intended Status: Experimental                            Haomian Zheng 
Expires: September 2022                                         Huawei 
                                                    Daniele Ceccarelli 
                                                              Ericsson 
                                                              Wei Wang 
                                    Beijing Univ. of Posts and Telecom 
                                                            Peter Park 
                                                                    KT 
                                                        Bin Young Yoon 
                                                                  ETRI 
                                                                      
                                                         March 7, 2022 
                                   
 
                                      
    PCEP Extension for Distribution of Link-State and TE Information for 
                             Optical Networks 

                                      
                     draft-lee-pce-pcep-ls-optical-11 

Abstract 

   In order to compute and provide optimal paths, Path Computation 
   Elements (PCEs) require an accurate and timely Traffic Engineering 
   Database (TED). Traditionally this Link State and TE information has 
   been obtained from a link state routing protocol (supporting traffic 
   engineering extensions).  

   An existing experimental document extends the Path Computation 
   Element Communication Protocol (PCEP) with Link-State and Traffic 
   Engineering (TE) Information.  This document provides further 
   experimental extensions to collect Link-State and TE information for 
   optical networks. 

 

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 
   other groups may also distribute working documents as Internet-
   Drafts. 
 
 
 
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   This Internet-Draft will expire on September 7, 2022. 

Copyright Notice 

   Copyright (c) 2022 IETF Trust and the persons identified as the 
   document authors. All rights reserved. 

   This document is subject to BCP 78 and the IETF Trust's Legal 
   Provisions Relating to IETF Documents 
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   publication of this document.  Please review these documents 
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   document must 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 ................................................ 3 
      1.1. Requirements Language .................................. 3 
   2. Applicability ............................................... 3 
   3. Requirements for PCEP Extension ............................. 4 
      3.1. Reachable Source-Destination ........................... 5 
      3.2. Optical Latency......................................... 5 
   4. PCEP-LS Extensions for Optical Networks ..................... 6 
      4.1. Node Attributes TLV .................................... 6 
      4.2. Link Attributes TLV .................................... 6 
      4.3. PCEP-LS for Optical Network Extension .................. 7 
   5. Security Considerations ..................................... 8 
   6. IANA Considerations ......................................... 8 
      6.1. PCEP-LS Sub-TLV Type Indicators ........................ 8 
   7. References .................................................. 9 
      7.1. Normative References ................................... 9 
      7.2. Informative References ................................. 9 
 
 
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   Appendix A. Contributor's Address  ............................ 11 
   Authors' Addresses ............................................ 11 
    
1. Introduction 

   [PCEP-LS] describes an experimental mechanism by which Link State 
   (LS) and Traffic Engineering (TE) information can be collected from 
   packet networks and shared through the Path Computation Element 
   Communication Protocol (PCEP) with a Path Computation Element (PCE).  
   This approach is called PCEP-LS and uses a new PCEP message format. 

   Problems in the optical networks, such as Optical Transport Networks 
   (OTN), is becoming worse due to the growth of the network 
   scalability. Such growths are also challenging the requirement of 
   memory/storage on each equipment. The introduction of a PCEP-based 
   LS helps solving the problem, with equally capability and 
   functionalities.  

   This document describes an experimental extension to PCEP-LS for use 
   in optical networks, and explains how encodings defined in [PCEP-LS] 
   can be used in the optical network contexts.  

1.1. Requirements Language 

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 
   "OPTIONAL" in this document are to be interpreted as described in 
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all 
   capitals, as shown here. 

    

2. Applicability  

   There are three main applicabilities of the mechanism described in 
   this document: 

       - Case 1: There is IGP running in optical network but there is a 
         need to collect LS and TE resource information at a PCE from 
         individual or specific optical nodes more frequently of more 
         rapidly than the IGP allows. 
          
            o A PCE may receive full information or an incremental 
              update (as opposed to the entire TE information of the 
              node/link). 
                
          
 
 
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       - Case 2: There is no IGP running in the optical network and 
         there is a need to collect link-state and TE resource 
         information from the optical nodes for use by the PCE.  
          
      
       - Case 3: There is a need to share abstract optical link-state 
         and TE information from child PCE to a parent PCE in a 
         hierarchical PCE (H-PCE) system per [RFC6805] and [RFC8751]. 
         Alternatively, this requirement may exist between a Physical 
         Network Controller (PNC) and a Multi-Domain Service 
         Coordinator (MDSC) in the Abstraction and Control of TE 
         Networks (ACTN) architecture [RFC8453].  
      
         Note: The applicability for Case 3 may arise as a consequence 
         of Case 1 and Case 2. When TE information changes occur in the 
         optical network, this may also affect abstracted TE 
         information and thus needs to be updated to the parent 
         PCE/MSDC from each child PCE/PNC.  
      
          

3. Requirements for PCEP Extension 

 
   The key requirements associated with link-state and TE information 
   distribution are identified for PCEP and listed in Section 4 of 
   [PCEP-LS]. These new functions introduced to PCEP to support 
   distribution of link-state (and TE) information are described in 
   Section 5 of [PCEP-LS]. Details of PCEP messages and related 
   Objects/TLVs are specified in Sections 8 and 9 of [PCEP-LS]. The key 
   requirements and new functions specified in [PCEP-LS] are equally 
   applicable to optical networks.  

   Besides the generic requirements specified in [PCEP-LS], optical 
   specific features also need to be considered. As a connection-based 
   network, there are specific parameters such as reachability table, 
   optical latency, wavelength consistency, and some other parameters 
   that need to be included during the topology collection. Without 
   these restrictions, the path computation may be inaccurate or 
   infeasible for deployment, therefore these information MUST be 
   included in the PCEP.  

   The procedure for using the optical parameters is described in 
   following sections.  

 
 
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       3.1. Reachable Source-Destination  

   The reachable source-destination node pair indicates that there are 
   some OCh paths between two nodes.  The reachability is restricted by 
   impairment, wavelength consistency and so on. This information is 
   necessary at the PCE to ensure that the path computed between source 
   node and destination node is feasible. In this scenario, the PCE is 
   responsible for computing how many OCh paths are available to set up 
   connections between source and destination node.  Moreover, if a set 
   of optical wavelengths is indicated in the path computation request, 
   the PCE also determines whether a wavelength from the set of 
   preselected optical wavelengths is available for the source-
   destination pair connection. 

   To enable the PCE to complete the above functions, the reachable 
   relationship and OMS link information need to be reported to the 
   PCE.  Once the PCE detects that any wavelength is available, the 
   corresponding OMS link is marked as a candidate link in the optical 
   network, which can then be used for path computation in the future.  

   Moreover, in a hierarchical PCE architecture, the information above 
   needs to be reported from child PCE to parent PCE, which acts as a 
   service coordinator.  

       3.2. Optical Latency  

   It is the usual case that the PCC indicates the latency when 
   requesting the path computation. In optical networks the latency is 
   a very sensitive parameter and there is stricter requirement on 
   latency. Given the number of OCh paths between source-destination 
   nodes, the PCE also need to determine how many OCh path satisfy the 
   indicated latency threshold.  

   There is usually an algorithm running on the PCE to guarantee the 
   performance of the computed path. During the computation, the delay 
   factor may be converted into a kind of link weight. After the 
   algorithm provides the candidate paths between the source and 
   destination nodes, the PCE selects the best path by computing the 
   total path propagation delay.  

   Optical PCEs contain optimization algorithms, e.g., shortest path 
   algorithm, to select the best-performing path.  

 
 
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4. PCEP-LS Extensions for Optical Networks 

   This section provides the additional PCEP-LS extensions necessary to 
   support optical networks. All Objects/TLVs defined in [PCEP-LS] are 
   applicable to optical networks.  

       4.1. Node Attributes TLV 

   The Node-Attributed TLV is defined in Section 9.3.9.1 of [PCEP-LS]. 
   This TLV is applicable for LS Node Object-Type as defined in [PCEP-
   LS].  

   This TLV contains a number of Sub-TLVs.  [PCEP-LS] defines that any 
   Node-Attribute defined for BGP-LS [BGP-LS] can be used as a Sub-TLV 
   of the PCEP Node-Attribute TLV.  BGP-LS does not support optical 
   networks, so the Node-Attribute Sub-TLVs shown below are defined in 
   this document for use in PCEP-LS for optical networks. 

   TBD1 The Connectivity Matrix Sub-TLV is used as defined in  
         [RFC7579]. 
    
   TBD2 The Resource Block Information Sub-TLV is used as defined in 
         [RFC7688]. 
    
   TBD3 The Resource Block Accessibility Sub-TLV is used as defined in 
         [RFC7688]. 
    
   TBD4 The Resource Block Wavelength Constraint Sub-TLV is used as 
         defined in [RFC7688]. 
    
   TBD5 The Resource Block Pool State Sub-TLV is used as defined in 
         [RFC7688]. 
    
   TBD6 The Resource Block Shared Access Wavelength Availability  
         Sub-TLV is used as defined in [RFC7688]. 
    
       4.2. Link Attributes TLV 

   The Link-Attributes TLV is defined in Section 9.3.9.2 of [PCEP-LS]. 
   This TLV is applicable for the LS Link Object-Type as defined in 
   [PCEP-LS]. 

   This TLV contains a number of Sub-TLVs.  [PCEP-LS] defines that any 
   Node-Attribute defined for BGP-LS [BGP-LS] can be used as a Sub-TLV 
   of the PCEP Link-Attribute TLV.  BGP-LS does not support optical 
   networks, so the Link-Attribute Sub-TLVs shown below are defined in 
   this document for use in PCEP-LS for optical networks. 
 
 
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   TBD7 The ISCD Sub-TLV is used to describe the Interface Switching 
         Capability Descriptor as defined in [RFC4203]. 

   TBD8 The OTN-TDM SCSI Sub-TLV is used to describe the Optical 
         Transport Network Time Division Multiplexing Switching 
         Capability Specific Information as defined in [RFC4203] and  
         [RFC7138]. 

   TBD9 The WSON-LSC SCSI Sub-TLV is used to describe the Wavelength 
         Switched Optical Network Lambda Switch Capable Switching 
         Capability Specific Information as defined in [RFC4203] and 
         [RFC7688]. 
    
   TBD10 The Flexi-grid SCSI Sub-TLV is used to describe the Flexi-grid 
         Switching Capability Specific Information as defined in 
         [RFC8363]. 

   TBD11 The Port Label Restriction Sub-TLV is used as defined in  
         [RFC7579], [RFC7580], and [RFC8363]. 

       4.3. PCEP-LS for Optical Network Extension 

   This section provides additional PCEP-LS extension necessary to 
   support the optical network parameters discussed in Sections 3.1 and 
   3.2.  

   Collection of link state and TE information is necessary before the 
   path computation processing can be done.  The procedure can be 
   divided into: 1) link state collection by receiving the 
   corresponding topology information in periodically; 2) path 
   computation on the PCE, triggered by receiving a path computation 
   request message from a PCC, and completed by transmitting a path 
   computation reply with the path computation result, per [RFC4655].  

   For OTN networks, maximum bandwidth available may be per ODU 0/1/2/3 
   switching level or aggregated across all ODU switching levels (i.e., 
   ODUj/k). 

   For Wavelength Switched Optical Networks (WSON) , Routing and 
   Wavelength Assignment (RWA) information collected from Network 
   Elements (Nes) would be utilized to compute light paths. The list of 
   information collected can be found in [RFC7688]. More specifically, 
   the maximum bandwidth available may be per lambda/frequency level 
 
 
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   (OCh) or aggregated across all lambda/frequency levels. Per OCh 
   level abstraction gives more detailed data to the P-PCE at the 
   expense of more information processing. Either the OCh-level or the 
   aggregated level abstraction in the RWA constraint (i.e., wavelength 
   continuity) needs to be taken into account by the PCE during path 
   computation. Resource Block Accessibility (i.e., wavelength 
   conversion information) in [RFC7688] needs to be taken into account 
   in order to guarantee the reliability of optical path computation. 

5. Security Considerations 

   This document extends PCEP for LS (and TE) distribution  in optical 
   networks by including a set of Sub-TLVs to be carried in existing 
   TLVs of existing messages.  Procedures and protocol extensions 
   defined in this document do not affect the overall PCEP security 
   model (see [RFC5440] and [RFC8253]). The PCE implementation SHOULD 
   provide mechanisms to prevent strains created by network flaps and 
   amount of LS (and TE) information as defined in [PCEP-LS].  Thus, 
   any mechanism used for securing the transmission of other PCEP 
   message SHOULD be applied here as well.  As a general precaution, it 
   is RECOMMENDED that these PCEP extensions only be activated on 
   authenticated and encrypted sessions belonging to the same 
   administrative authority. 
    
6. IANA Considerations 

   This document requests IANA actions to allocate code points for the 
   protocol elements defined in this document. 
    
       6.1. PCEP-LS Sub-TLV Type Indicators 

   PCEP-LS] requests IANA to create a registry of "PCEP-LS Sub-TLV Type 
   Indicators".  IANA is requested to make the following allocations 
   from this registry using the range 1 to 255. 

 
   +-----------+-------------------------------------------------- 
   |  Sub-TLV  | Meaning           
   +-----------+-------------------------------------------------- 
   |    TBD1   | Connectivity Matrix 
   |    TBD2   | Resource Block Information 
   |    TBD3   | Resource Block Accessibility 
   |    TBD4   | Resource Block Wavelength Constraint 
   |    TBD5   | Resource Block Pool State 
   |    TBD6   | Resource Block Shared Access Wavelength Available 
   |    TBD7   | ISCD 
   |    TBD8   | OTN-TDM SCSI 
 
 
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   |    TBD9   | WSON-LSC SCSI 
   |    TBD10  | Flexi-grid SCSI 
   |    TBD11  | Port Label Restriction 
    
    

7. References 

       7.1. Normative References 

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

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic 
             Engineering", RFC 5305, October 2008.  

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 
             Element (PCE) Communication Protocol (PCEP)", RFC 5440, 
             March 2009.   

   [RFC7688] Lee, Y., Ed., and G. Bernstein, Ed., "GMPLS OSPF            
             Enhancement for Signal and Network Element Compatibility           
             for Wavelength Switched Optical Networks", RFC 7688, 
             November 2015. 

   [RFC8174] B. Leiba, "Ambiguity of Uppercase vs Lowercase in RFC 2119         
             Key Words", RFC 8174, May 2017.     

       7.2. Informative References 

   [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering 
             (TE) Extensions to OSPF Version 2", RFC 3630, September 
             2003. 

   [RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in 
             Support of Generalized Multi-Protocol Label Switching 
             (GMPLS)", RFC 4203, October 2005. 

   [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 
             Element (PCE)-Based Architecture", RFC 4655, August 2006. 

   [RFC5307] Kompella, K., Ed., and Y. Rekhter, Ed., "IS-IS Extensions          
             in Support of Generalized Multi-Protocol Label Switching           
             (GMPLS)", RFC 5307, October 2008. 

 
 
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   [RFC7752] Gredler, H., Medved, J., Previdi, S., Farrel, A., and 
             S.Ray, "North-Bound Distribution of Link-State and TE 
             information using BGP", RFC 7752, March 2016. 

   [S-PCE-GMPLS] X. Zhang, et. al, "Path Computation Element (PCE) 
             Protocol Extensions for Stateful PCE Usage in GMPLS-
             controlled Networks", draft-ietf-pce-pcep-stateful-pce-
             gmpls, work in progress. 

   [RFC7399] A. Farrel and D. king, "Unanswered Questions in the Path 
             Computation Element Architecture", RFC 7399, October 2015.  

   [RFC8453] D.Ceccarelli, and Y. Lee (Editors), "Framework for 
             Abstraction and Control of TE Networks", RFC453, August, 
             2018. 

   [RFC6805] A. Farrel and D. King, "The Application of the Path 
             Computation Element Architecture to the Determination of a 
             Sequence of Domains in MPLS and GMPLS", RFC 6805, November 
             2012. 

   [PCEP-LS] D. Dhody, Y. Lee and D. Ceccarelli "PCEP Extension for 
             Distribution of Link-State and TE Information.", draft-
             dhodylee-pce-pcep-ls, work in progress, July, 2020 

   [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP 
             Extensions for Stateful PCE", RFC8231, September 2017. 

   [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., Dhody, D., 
             "PCEPS: Usage of TLS to Provide a Secure Transport for the 
             Path Computation Element Communication Protocol (PCEP)", 
             RFC8253, October 2017.  

   [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP 
             Extensions for PCE-initiated LSP Setup in a Stateful PCE 
             Model", RFC8281, December 2017. 

   [RFC8751] D. Dhody, Y. Lee and D. Ceccarelli, "Hierarchical Stateful 
             Path Computation Element (PCE)", RFC8751, March 2020.  

   [RFC8363] X. Zhang, H. Zheng, R. Casellas, O. Gonzalez de Dios, D. 
             Ceccarelli, "GMPLS OSPF Extensions in support of Flexi-
             grid DWDM networks", RFC8363, May 2018. 

 
 
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Appendix A. Contributor's Address 

   Dhruv Dhody 
   Huawei Technologies 
   Divyashree Techno Park, Whitefield 
   Bangalore, Karnataka 560066 
   India 
   Email: dhruv.ietf@gmail.com 
 

Authors' Addresses 

    
   Young Lee 
   Samsung  
   Email: younglee.tx@gmail.com  
    
   Haomian Zheng  
   Huawei Technologies Co., Ltd.  
   Email: zhenghaomian@huawei.com 
    
 
   Daniele Ceccarelli 
   Ericsson 
   Torshamnsgatan,48 
   Stockholm 
   Sweden 
   EMail: daniele.ceccarelli@ericsson.com 
 
   Wei Wang 
   Beijing University of Posts and Telecom 
   No. 10, Xitucheng Rd. Haidian District, Beijing 100876, China 
   Email: weiw@bupt.edu.cn 
    
    Peter Park 
  KT 
  Email: peter.park@kt.com  
 
   Bin Yeong Yoon 
   ETRI 
   Email: byyun@etri.re.kr 
 
 
 
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