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PCE WG                                                       Quan. Xiong
Internet-Draft                                               Fangwei. Hu
Intended status: Standards Track                               Ran. Chen
Expires: April 25, 2019                                  ZTE Corporation
                                                        October 22, 2018


                    PCE Multi-layer LSP Association
             draft-xiong-pce-multilayer-lsp-association-02

Abstract

   The Path Computation Element Communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients (PCCs) requests.
   [I-D.ietf-pce-association-group] proposed an association mechanism
   for a set of LSPs.

   This document proposes a set of extensions to PCEP to associate a
   grouping of multi-layer LSPs.  The extensions define a mechanism to
   create associations between upper-layer LSP and related lower-layer
   LSPs.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 25, 2019.

Copyright Notice

   Copyright (c) 2018 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
   (https://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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   include Simplified BSD License text as described in Section 4.e of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Requirements Language . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Operation Overview  . . . . . . . . . . . . . . . . . . .   4
   4.  Extensions to the PCEP  . . . . . . . . . . . . . . . . . . .   5
     4.1.  Association Type and Group  . . . . . . . . . . . . . . .   5
     4.2.  MULTI-LAYER-ASSOCIATION TLV . . . . . . . . . . . . . . .   5
   5.  PCEP Procedure  . . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Multi-Layer LSPs Associations Creation  . . . . . . . . .   6
     5.2.  Bandwidth Adjustment  . . . . . . . . . . . . . . . . . .   6
     5.3.  TE Links Optimization . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Association Object Type . . . . . . . . . . . . . . . . .   7
     7.2.  LAYER-ASSOCIATION TLV . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Informative References  . . . . . . . . . . . . . . . . .   8
     9.2.  Normative References  . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [RFC5440] describes the Path Computation Element Protocol (PCEP)
   which is used between a Path Computation Element (PCE) and a Path
   Computation Client (PCC) (or other PCE) to enable computation of
   Multi-protocol Label Switching (MPLS) for Traffic Engineering Label
   Switched Path (TE LSP).  [I-D.ietf-pce-association-group] proposed an
   association mechanism to create a grouping of LSPs in the context of
   a PCE.

   This document proposes a set of extensions to PCEP to associate a
   grouping of multi-layer LSPs.  The extensions define a mechanism to
   create associations between upper-layer LSP and related lower-layer
   LSPs.





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2.  Requirements Language

   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].

2.1.  Terminology

   The terminology is defined as [RFC5440]
   ,[I-D.ietf-pce-stateful-pce-app] and
   [I-D.ietf-pce-association-group].

3.  Overview

3.1.  Motivation

   In GMPLS/MPLS networks, service provider network is divided into
   several service layers according to the requirements and customer
   network is the upper layer with the lower layers as the Forwarding
   Adjacency LSP (FA-LSP) as shown in Figure 1.  The service connection
   is established with the set up of multi-layer LSPs.


                    Initiate & Update LSP and related lower LSPs
                                       |
                                       |
                                       V
                                   +---+--+
                    +--------------+ PCE  +---------------+
                    |              +---+--+               |
                    |                  |                  |
                    |                  |                  |
                    |                  |                  |
                +---+--+           +---+--+           +---+--+
                | PCC1 +-----------+ PCC2 +-----------+ PCC3 +
                +------+   LSP1->  +------+  LSP2->   +------+
                    |                                     |
                    |<------          LSP3          ----->|

                     Figure 1 Usecase for multi-layer LSPs

   As discussed in [I-D.ietf-pce-stateful-pce-app] , it consists of a
   set of one or more TE LSPs in the lower layer which provides TE links
   to the upper layer in Multi-Layer Networks (MLN).  The requirement is
   to control of the multi-layer LSPs and related TE links.  The
   establishment or teardown of a lower layer LSP needs to take into
   consideration the state of existing LSPs or new LSP request in the
   upper layer.



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   As discussed in [I-D.ietf-pce-stateful-pce] , the stateful PCE MAY
   determine to optimize the link and path based on the lower layer of
   the LSP and its upper TE Link, and in the case of the failure of the
   lower level LSP, it MAY update the upper network LSP path according
   to the existing resources and the status of the LSP.

   The stateful PCE provides the ability to update the LSP, in the
   process of bandwidth adjustment, it MAY be necessary to adjust the
   bandwidth of related lower layer LSPs, which provide the TE link for
   the upper layer LSP.  The association of multi-layer LSPs can reduce
   the repeated operations and optimize the information interaction
   between PCC and PCE.

   In overlayer multi-domain scenario, the lower-layer LSPs in each
   domain may be initiated by respective domain's PCE and stitched
   together to an association group with an end-to-end LSP as its upper-
   layer LSP.

   In these cases, it is necessary to add multi-layer LSPs to an
   association group.

3.2.  Operation Overview

   [I-D.ietf-pce-association-group] introduces a generic mechanism to
   create a grouping of LSPs.  This grouping can then be used to define
   associations between sets of LSPs or between a set of LSPs and a set
   of attributes.

   In order to solve the problem of multi-layer LSP control in PCE
   network, this document proposes the association if the multi-layer
   LSPs.  The upper LSP is associated with its related lower LSPs by
   adding them to a multi-layer association group.

   One new optional Association Object type is defined carried in the
   Association object defined in [I-D.ietf-pce-association-group].  This
   document proposes a new association type called "Layer Association
   Type" and related TLV called "LAYER-ASSOCIATION TLV".

   As defined in [I-D.ietf-pce-association-group], multi-layer LSPs
   associations could be created dynamically or configured by the
   operator when operator-configured association is needed.

   The handling and policy of multi-layer LSPs Association is similar to
   the generic association and some processing rules as shown in session
   4.2.






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4.  Extensions to the PCEP

4.1.  Association Type and Group

   [I-D.ietf-pce-association-group] introduces the ASSOCIATION object
   and this document proposes a new Association type for multi-layer
   LSPs association to associate multi-layer LSPs into one group for
   further operation.  An association ID will be used to identify the
   group and a new Association Type is defined in this document, based
   on the generic Association object :

   Association type = TBD1 ("Multi-Layer Association Type") for Multi-
   Layer Association Group (MLAG)

   MLAG may carry optional TLVs including but not limited to :

   MULTI-LAYER-ASSOCIATION-TLV: Used to identify the upper-layer LSP and
   lower-layer LSP in multi-layer information, described in Section 4.2.

   As [I-D.ietf-pce-association-group] specified, the capability
   advertisement of the association types supported by a PCEP speaker is
   performed by defining a ASSOC-Type-List TLV to be carried within an
   OPEN object.  The association type which defined in this document
   should be added in the list and be advertised between the PCEP
   speakers before the multi-layer association.

   This Association-Type is operator-configured and created by the
   operator manually on the PCEP peers.  The LSP belonging to this
   associations is conveyed via PCEP messages to the PCEP peer.
   Operator-configured Association Range SHOULD NOT be set for this
   association-type, and MUST be ignored, so that the full range of
   association identifier can be utilized.

4.2.  MULTI-LAYER-ASSOCIATION TLV

   This document proposes LAYER-ASSOCIATION TLV for the association of
   multi-layer LSPs.  The TLV is optional.  The format of the new
   Association TLV is shown in Figure 4:


       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 = TBD         |           Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 Layer Association Flags                   |H|L|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Figure 4: The LAYER-ASSOCIATION TLV format



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   The type of the TLV is [TBD] which indicates the LAYER ASSOCIATION
   TLV.  The fields in the format are:

   Length:16bits,the length of the TLV.

   Layer Association Flags-H:1bit, indicates LSP of the upper layer when
   it is set.

   Layer Association Flags-L:1bit, indicates LSP of the lower layer when
   it is set.

5.  PCEP Procedure

   Once a group of multilayer LSPs is created, the upper layer LSP is
   associated with its related lower layer LSPs.  Association objects
   can be carried in PCReq, PCRpt, PCUpd, or PCInit messages.

5.1.  Multi-Layer LSPs Associations Creation

   As defined in [I-D.ietf-pce-association-group], association groups
   can be created by both PCC and PCE.

   In stateless PCE, the association object with "Layer Association
   type" is carried in PCReq message from PCC to PCE, indicating that
   the LSP joins one existing multi-layer LSPs association group or
   create a new one.  If the LSP is belong to upper layer then set the
   "H" bit in "LAYER-ASSOCIATION TLV", otherwise set the "L" bit when it
   is lower layer LSP.

   In stateful PCE, PCE MAY create a new association group or associate
   a LSP to an existing association group carried in PCInit message
   after the LSP delegation from PCC to the PCE as discussed in
   [I-D.ietf-pce-pce-initiated-lsp].  In state synchronization process
   between PCC and PCE, PCC also need to report the existing multi-layer
   LSPs association groups to PCE.  If the association group changes,
   PCC needs to report the relevant group changes to PCE through the
   PCRpt message.

5.2.  Bandwidth Adjustment

   The stateful PCE provides the ability to update the LSP, in the
   process of bandwidth adjustment, for example, enlarge the bandwidth
   of the upper layer LSP, it MUST be necessary to adjust the bandwidth
   of related lower layer LSPs, which provide the TE link for it.

   Once the multi-layer LSPs associated in a group, the PCE MAY send the
   PCUpd message to the PCC with the association object to adjust the
   upper layer LSP.  Once receiving the request, PCC will search the



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   relevant lower layer LSPs and adjust their bandwidth before the
   adjustment of the upper layer LSP.

5.3.  TE Links Optimization

   The stateful PCE MAY determine to optimize the link and path based on
   the lower layer of the LSP and its upper TE Link, and in the case of
   the failure of the lower level LSP, it MAY update the upper network
   LSP path and re-optimize resource usage across multi-layers.

   When removing the upper layer LSP, PCC or PCE MAY release each of
   lower layer LSPs which associated in a group and re-use the resources
   for other upper layer LSP according to the existing resources and the
   status of the LSP.

6.  Security Considerations

   TBD

7.  IANA Considerations

7.1.  Association Object Type

   This document defines a new association type in Association object
   which originally defined in [I-D.ietf-pce-association-group].  IANA
   is requested to make allocations from the registry, as follows:

          +--------+-------------------------+------------------+
          | Value  |           Name          |    Reference     |
          +--------+-------------------------+------------------+
          |  TBD   |  Layer Association Type | [this document]  |
          +--------+-------------------------+------------------+

                                  Table 1

7.2.  LAYER-ASSOCIATION TLV

   This document defines the following TLV in Association object which
   originally defined in [I-D.ietf-pce-association-group].  IANA is
   requested to make allocations from the registry, as follows:

           +--------+-----------------------+------------------+
           | Value  |          Name         |    Reference     |
           +--------+-----------------------+------------------+
           |  TBD   | LAYER-ASSOCIATION TLV | [this document]  |
           +--------+-----------------------+------------------+

                                  Table 2



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8.  Acknowledgements

   TBD.

9.  References

9.1.  Informative References

   [I-D.ietf-pce-stateful-pce-app]
              Zhang, X. and I. Minei, "Applicability of a Stateful Path
              Computation Element (PCE)", draft-ietf-pce-stateful-pce-
              app-08 (work in progress), October 2016.

9.2.  Normative References

   [I-D.ietf-pce-association-group]
              Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
              Dhody, D., and Y. Tanaka, "PCEP Extensions for
              Establishing Relationships Between Sets of LSPs", draft-
              ietf-pce-association-group-06 (work in progress), June
              2018.

   [I-D.ietf-pce-pce-initiated-lsp]
              Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
              Extensions for PCE-initiated LSP Setup in a Stateful PCE
              Model", draft-ietf-pce-pce-initiated-lsp-11 (work in
              progress), October 2017.

   [I-D.ietf-pce-stateful-pce]
              Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
              Extensions for Stateful PCE", draft-ietf-pce-stateful-
              pce-21 (work in progress), June 2017.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

Authors' Addresses







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   Quan Xiong
   ZTE Corporation
   No.6 Huashi Park Rd
   Wuhan, Hubei  430223
   China

   Phone: +86 27 83531060
   Email: xiong.quan@zte.com.cn


   Fangwei Hu
   ZTE Corporation
   No.889 Bibo Rd
   Shanghai  201203
   China

   Phone: +86 21 68896273
   Email: hu.fangwei@zte.com.cn


   Ran Chen
   ZTE Corporation
   No.50 Software Avenue,Yuhuatai District
   Nanjing, Jiangsu Province  210012
   China

   Phone: +86 025 88014636
   Email: chen.ran@zte.com.cn























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