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Versions: (draft-palle-pce-stateful-pce-p2mp) 00 01 02 03 04 05 06 07 08 09 10 11 12 13

PCE Working Group                                               U. Palle
Internet-Draft                                                  D. Dhody
Intended status: Standards Track                     Huawei Technologies
Expires: August 22, 2019                                       Y. Tanaka
                                                      NTT Communications
                                                               V. Beeram
                                                        Juniper Networks
                                                       February 18, 2019


  Path Computation Element (PCE) Protocol Extensions for Stateful PCE
 usage for Point-to-Multipoint Traffic Engineering Label Switched Paths
                  draft-ietf-pce-stateful-pce-p2mp-11

Abstract

   The Path Computation Element (PCE) has been identified as an
   appropriate technology for the determination of the paths of point-
   to-multipoint (P2MP) TE Label Switched Paths (LSPs).  This document
   provides extensions required for Path Computation Element
   Communication Protocol (PCEP) so as to enable the usage of a stateful
   PCE capability in supporting P2MP TE 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
   and may be updated, replaced, or obsoleted by other documents at any
   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 August 22, 2019.

Copyright Notice

   Copyright (c) 2019 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
   to this document.  Code Components extracted from this 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 . . . . . . . . . . . . . . . . . .   4
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Supporting P2MP TE LSPs for Stateful PCE  . . . . . . . . . .   4
     3.1.  Motivation  . . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Objectives  . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Functions to Support P2MP TE LSPs for Stateful PCEs . . . . .   5
   5.  Architectural Overview of Protocol Extensions . . . . . . . .   6
     5.1.  Extension of PCEP Messages  . . . . . . . . . . . . . . .   6
     5.2.  Capability Advertisement  . . . . . . . . . . . . . . . .   6
     5.3.  IGP Extensions for Stateful PCE P2MP Capabilities
           Advertisement . . . . . . . . . . . . . . . . . . . . . .   7
     5.4.  State Synchronization . . . . . . . . . . . . . . . . . .   8
     5.5.  LSP Delegation  . . . . . . . . . . . . . . . . . . . . .   8
     5.6.  LSP Operations  . . . . . . . . . . . . . . . . . . . . .   8
       5.6.1.  Passive Stateful PCE  . . . . . . . . . . . . . . . .   8
       5.6.2.  Active Stateful PCE . . . . . . . . . . . . . . . . .   9
       5.6.3.  PCE-Initiated LSP . . . . . . . . . . . . . . . . . .   9
         5.6.3.1.  P2MP TE LSPs Instantiation  . . . . . . . . . . .   9
         5.6.3.2.  P2MP TE LSPs Deletion . . . . . . . . . . . . . .   9
         5.6.3.3.  Adding and Pruning Leaves for the P2MP TE LSP . .  10
         5.6.3.4.  P2MP TE LSPs Delegation and Cleanup . . . . . . .  10
   6.  PCEP Message Extensions . . . . . . . . . . . . . . . . . . .  10
     6.1.  The PCRpt Message . . . . . . . . . . . . . . . . . . . .  10
     6.2.  The PCUpd Message . . . . . . . . . . . . . . . . . . . .  13
     6.3.  The PCReq Message . . . . . . . . . . . . . . . . . . . .  14
     6.4.  The PCRep Message . . . . . . . . . . . . . . . . . . . .  14
     6.5.  The PCInitiate message  . . . . . . . . . . . . . . . . .  15
     6.6.  Example . . . . . . . . . . . . . . . . . . . . . . . . .  16
       6.6.1.  P2MP TE LSPs Update Request . . . . . . . . . . . . .  17
       6.6.2.  P2MP TE LSP Report  . . . . . . . . . . . . . . . . .  17
       6.6.3.  P2MP TE LSPs Initiation Request . . . . . . . . . . .  18
   7.  PCEP Object Extensions  . . . . . . . . . . . . . . . . . . .  19
     7.1.  Extension of LSP Object . . . . . . . . . . . . . . . . .  19
     7.2.  P2MP-LSP-IDENTIFIERS TLV  . . . . . . . . . . . . . . . .  19
     7.3.  S2LS Object . . . . . . . . . . . . . . . . . . . . . . .  22
   8.  Message Fragmentation . . . . . . . . . . . . . . . . . . . .  23
     8.1.  Report Fragmentation Procedure  . . . . . . . . . . . . .  23
     8.2.  Update Fragmentation Procedure  . . . . . . . . . . . . .  23



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     8.3.  PCIntiate Fragmentation Procedure . . . . . . . . . . . .  24
   9.  Non-Support of P2MP TE LSPs for Stateful PCE  . . . . . . . .  24
   10. Manageability Considerations  . . . . . . . . . . . . . . . .  25
     10.1.  Control of Function and Policy . . . . . . . . . . . . .  25
     10.2.  Information and Data Models  . . . . . . . . . . . . . .  25
     10.3.  Liveness Detection and Monitoring  . . . . . . . . . . .  25
     10.4.  Verify Correct Operations  . . . . . . . . . . . . . . .  26
     10.5.  Requirements On Other Protocols  . . . . . . . . . . . .  26
     10.6.  Impact On Network Operations . . . . . . . . . . . . . .  26
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
     11.1.  PCE Capabilities in IGP Advertisements . . . . . . . . .  26
     11.2.  STATEFUL-PCE-CAPABILITY TLV  . . . . . . . . . . . . . .  26
     11.3.  LSP Object . . . . . . . . . . . . . . . . . . . . . . .  27
     11.4.  PCEP-Error Object  . . . . . . . . . . . . . . . . . . .  27
     11.5.  PCEP TLV Type Indicators . . . . . . . . . . . . . . . .  28
     11.6.  PCEP object  . . . . . . . . . . . . . . . . . . . . . .  29
     11.7.  S2LS object  . . . . . . . . . . . . . . . . . . . . . .  29
   12. Security Considerations . . . . . . . . . . . . . . . . . . .  30
   13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  30
   14. References  . . . . . . . . . . . . . . . . . . . . . . . . .  30
     14.1.  Normative References . . . . . . . . . . . . . . . . . .  30
     14.2.  Informative References . . . . . . . . . . . . . . . . .  31
   Appendix A.  Contributor Addresses  . . . . . . . . . . . . . . .  33
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  33

1.  Introduction

   As per [RFC4655], the Path Computation Element (PCE) is an entity
   that is capable of computing a network path or route based on a
   network graph and applying computational constraints.  A Path
   Computation Client (PCC) may make requests to a PCE for paths to be
   computed.

   [RFC4875] describes how to set up point-to-multipoint (P2MP) Traffic
   Engineering Label Switched Paths (TE LSPs) for use in Multiprotocol
   Label Switching (MPLS) and Generalized MPLS (GMPLS) networks.  The
   PCE has been identified as a suitable application for the computation
   of paths for P2MP TE LSPs ([RFC5671]).

   The PCEP is designed as a communication protocol between PCCs and
   PCEs for point-to-point (P2P) path computations and is defined in
   [RFC5440].  The extensions of PCEP to request path computation for
   P2MP TE LSPs are described in [RFC8306].

   Stateful PCEs are shown to be helpful in many application scenarios,
   in both MPLS and GMPLS networks, as illustrated in [RFC8051].  These
   scenarios apply equally to P2P and P2MP TE LSPs.  [RFC8231] provides
   the fundamental extensions to PCEP needed for stateful PCE to support



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   general functionality for P2P TE LSP.  [RFC8281] provides extensions
   to PCEP needed for stateful PCE-initiated P2P TE LSP.  This document
   complements that work by focusing on PCEP extensions that are
   necessary in order for the deployment of stateful PCEs to support
   P2MP TE LSPs.  This document describes the setup, maintenance, and
   teardown of PCE-initiated P2MP LSPs under the stateful PCE model.

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.  Terminology

   Terminology used in this document is same as terminology used in
   [RFC8231], [RFC8281], and [RFC8306].

3.  Supporting P2MP TE LSPs for Stateful PCE

3.1.  Motivation

   [RFC8051] presents several use cases, demonstrating scenarios that
   benefit from the deployment of a stateful PCE including optimization,
   recovery, etc., which are equally applicable to P2MP TE LSPs.
   [RFC8231] defines the extensions to PCEP for P2P TE LSPs.  This
   document complements the previous work by focusing on extensions that
   are necessary in order for the deployment of stateful PCEs to support
   P2MP TE LSPs.

   In addition to that, the stateful nature of a PCE simplifies the
   information conveyed in PCEP messages since it is possible to refer
   to the LSPs via a PCEP-specific LSP identifier (PLSP-ID) ([RFC8231]).
   For P2MP, where the size of message is much larger, this is an added
   advantage.  When using a stateless PCE, a request to modify an
   existing P2MP tree requires that all the leaves are presented in the
   PCEP messages along with all the path information.  But when using a
   stateful PCE, the PCEP messages can use a PLSP-ID to represent all
   information about the LSP that has previously been exchanged in PCEP
   messages, and it is only necessary to encode the modifications (such
   as new or removed leaf nodes).  The PLSP-ID provides an index into
   the LSP-DB at the PCE, and identifies the LSP at the PCC.

   In environments where the P2MP TE LSPs placement needs to change in
   response to application demands, it is useful to support dynamic
   creation and tear down of P2MP TE LSPs.  The ability for a PCE to



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   trigger the creation of P2MP TE LSPs on demand can be seamlessly
   integrated into a controller-based network architecture, where
   intelligence in the controller can determine when and where to set up
   paths.  Section 3 of [RFC8281] further describes the motivation
   behind the PCE-Initiation capability, which is equally applicable to
   P2MP TE LSPs.

3.2.  Objectives

   The objectives for the protocol extensions to support P2MP TE LSPs
   for stateful PCE are same as the objectives described in section 3.2
   of [RFC8231].

4.  Functions to Support P2MP TE LSPs for Stateful PCEs

   [RFC8231] specifies new functions to support a stateful PCE.  It also
   specifies that a function can be initiated either from a PCC towards
   a PCE (C-E) or from a PCE towards a PCC (E-C).

   This document extends these functions to support P2MP TE LSPs.

   Capability Advertisement (E-C,C-E):  both the PCC and the PCE must
      announce during PCEP session establishment that they support
      Stateful PCE extensions for P2MP using mechanisms defined in
      Section 5.2.

   LSP State Synchronization (C-E):  after the session between the PCC
      and a stateful PCE with P2MP capability is initialized, the PCE
      must learn the state of a PCC's P2MP TE LSPs before it can perform
      path computations or update LSP attributes in a PCC.

   LSP Update Request (E-C):  a stateful PCE with P2MP capability
      requests modification of attributes on a PCC's P2MP TE LSPs.

   LSP State Report (C-E):  a PCC sends an LSP state report to a PCE
      whenever the state of a P2MP TE LSP changes.

   LSP Control Delegation (C-E,E-C):  a PCC grants to a PCE the right to
      update LSP attributes on one or more P2MP TE LSPs; the PCE becomes
      the authoritative source of the LSP's attributes as long as the
      delegation is in effect (See Section 5.7 of [RFC8231]); the PCC
      may withdraw the delegation or the PCE may give up the delegation
      at any time.

   PCE-initiated LSP instantiation (E-C):  a PCE sends an LSP Initiate
      Message to a PCC to instantiate or delete a P2MP TE LSP [RFC8281].





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5.  Architectural Overview of Protocol Extensions

5.1.  Extension of PCEP Messages

   New PCEP messages are defined in [RFC8231] to support stateful PCE
   for P2P TE LSPs.  In this document these messages are extended to
   support P2MP TE LSPs.

   Path Computation State Report (PCRpt):  Each P2MP TE LSP State Report
      in a PCRpt message can contain actual P2MP TE LSP path attributes,
      LSP status, etc.  An LSP State Report carried in a PCRpt message
      is also used in delegation or revocation of control of a P2MP TE
      LSP to/from a PCE.  The extension of PCRpt message is described in
      Section 6.1.

   Path Computation Update Request (PCUpd):  Each P2MP TE LSP Update
      Request in a PCUpd message MUST contain all LSP parameters that a
      PCE wishes to set for a given P2MP TE LSP.  An LSP Update Request
      carried in a PCUpd message is also used to return LSP delegations
      if at any point PCE no longer desires control of a P2MP TE LSP.
      The PCUpd message is described in Section 6.2.

   A PCEP message is defined in [RFC8281] to support stateful PCE
   instantiation of P2P TE LSPs.  In this document this message is
   extended to support P2MP TE LSPs.

   Path Computation LSP Initiate Message (PCInitiate):  PCInitiate is a
      PCEP message sent by a PCE to a PCC to trigger P2MP TE LSPs
      instantiation or deletion.  The PCInitiate message is described in
      Section 6.5.

   The Path Computation Request (PCReq) and Path Computation Reply
   (PCRep) messages are also extended to support passive stateful PCE
   for P2P TE LSP in [RFC8231].  In this document these messages are
   extended to support P2MP TE LSPs as well.

5.2.  Capability Advertisement

   During PCEP Initialization Phase, as per Section 7.1.1 of [RFC8231],
   PCEP speakers advertise Stateful capability via the STATEFUL-PCE-
   CAPABILITY TLV in the OPEN object.  Various flags are defined for the
   STATEFUL-PCE-CAPABILITY TLV defined in [RFC8231] and updated in
   [RFC8281] and [RFC8232].

   Three new flags N (P2MP-CAPABILITY), M (P2MP-LSP-UPDATE-CAPABILITY),
   and P (P2MP-LSP-INSTANTIATION-CAPABILITY) are added in this document:





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   N (P2MP-CAPABILITY flag - 1 bit):  if set to 1 by a PCC, the N Flag
      indicates that the PCC is willing to send P2MP LSP State Reports
      whenever any parameters or operational status change of the P2MP
      LSP; if set to 1 by a PCE, the N Flag indicates that the PCE is
      interested in receiving LSP State Reports whenever there is any
      parameters or operational status change of the P2MP LSP.  The
      P2MP-CAPABILITY Flag MUST be advertised by both a PCC and a PCE
      for PCRpt messages P2MP extension to be allowed on a PCEP session.

   M (P2MP-LSP-UPDATE-CAPABILITY flag - 1 bit):  if set to 1 by a PCC,
      the M Flag indicates that the PCC allows modification of P2MP LSP
      parameters; if set to 1 by a PCE, the M Flag indicates that the
      PCE is capable of updating P2MP LSP parameters.  The P2MP-LSP-
      UPDATE-CAPABILITY Flag MUST be advertised by both a PCC and a PCE
      for PCUpd messages P2MP extension to be allowed on a PCEP session.

   P (P2MP-LSP-INSTANTIATION-CAPABILITY flag - 1 bit):  If set to 1 by a
      PCC, the P Flag indicates that the PCC allows instantiation of a
      P2MP LSP by a PCE.  If set to 1 by a PCE, the P flag indicates
      that the PCE supports P2MP LSP instantiation.  The P2MP-LSP-
      INSTANTIATION-CAPABILITY flag MUST be set by both PCC and PCE in
      order to support PCE-initiated P2MP LSP instantiation.

   A PCEP speaker should continue to advertise the basic P2MP capability
   via mechanisms as described in [RFC8306].

5.3.  IGP Extensions for Stateful PCE P2MP Capabilities Advertisement

   When PCC is a Label Switching Router (LSR), participating in the IGP
   (OSPF or IS-IS), and PCEs are either LSRs or servers also
   participating in the IGP, an effective mechanism for PCE discovery
   within an IGP routing domain consists of utilizing IGP
   advertisements.  Extensions for the advertisement of PCE Discovery
   Information are defined for OSPF and for IS-IS in [RFC5088] and
   [RFC5089] respectively.

   The PCE-CAP-FLAGS sub-TLV, defined in [RFC5089], is an optional sub-
   TLV used to advertise PCE capabilities.  It MAY be present within the
   PCE Discovery (PCED) TLV carried by OSPF or IS-IS.  [RFC5088] and
   [RFC5089] provide the description and processing rules for this sub-
   TLV when carried within OSPF and IS-IS, respectively.

   The format of the PCE-CAP-FLAGS sub-TLV is included below for easy
   reference:

   Type: 5

   Length: Multiple of 4.



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   Value: This contains an array of units of 32 bit flags with the most
   significant bit as 0.  Each bit represents one PCE capability.

   PCE capability bit flags are defined in [RFC5088].  This document
   defines new capability bits (early allocated by IANA) for the
   stateful PCE with P2MP as follows:

               Bit                  Capability
               13                   Active Stateful PCE with P2MP
               14                   Passive Stateful PCE with P2MP
               15                   PCE-Initiation with P2MP

   Note that while active, passive or initiation stateful PCE with P2MP
   capabilities may be advertised during discovery, PCEP Speakers that
   wish to use stateful PCEP MUST advertise stateful PCEP capabilities
   during PCEP session setup, as specified in the current document.  A
   PCC MAY initiate stateful PCEP P2MP capability advertisement at PCEP
   session setup even if it did not receive any IGP PCE capability
   advertisements.

5.4.  State Synchronization

   State Synchronization operations (described in Section 5.6 of
   [RFC8231]) are applicable for the P2MP TE LSPs as well.  The
   optimizations described in [RFC8232] can also be applied for P2MP TE
   LSPs.

5.5.  LSP Delegation

   LSP delegation operations (described in Section 5.7 of [RFC8231]) are
   applicable for P2MP TE LSPs as well.

5.6.  LSP Operations

5.6.1.  Passive Stateful PCE

   LSP operations for passive stateful PCE (described in Section 5.8.1
   of [RFC8231]) are applicable for P2MP TE LSPs as well.

   The PCReq and PCRep message format for P2MP TE LSPs is described in
   Section 3.4 and Section 3.5 of [RFC8306] respectively.

   The PCReq and PCRep message for P2MP TE LSPs are extended to support
   encoding of LSP object, so that it is possible to refer to an LSP
   with a unique identifier and simplify the PCEP message exchange.  For
   example, in case of modification of one leaf in a P2MP tree, there
   should be no need to carry the full P2MP tree in PCReq message.




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   The extension for the Request and Response message for passive
   stateful operations on P2MP TE LSPs are described in Section 6.3 and
   Section 6.4.  The extension for the Path Computation LSP State Report
   (PCRpt) message is described in Section 6.1.

5.6.2.  Active Stateful PCE

   LSP operations for active stateful PCE (described in Section 5.8.2 of
   [RFC8231]) are applicable for P2MP TE LSPs as well.

   The extension for the Path Computation LSP Update (PCUpd) message for
   active stateful operations on P2MP TE LSPs are described in
   Section 6.2.

5.6.3.  PCE-Initiated LSP

   As per section 5.1 of [RFC8281], the PCE sends a Path Computation LSP
   Initiate Request (PCInitiate) message to the PCC to suggest
   instantiation or deletion of a P2P TE LSP.  This document extends the
   PCInitiate message to support P2MP TE LSPs (see details in
   Section 6.5).

   The P2MP TE LSPs suggested instantiation and deletion operations are
   same as for P2P LSP as described in section 5.3 and 5.4 of [RFC8281].

5.6.3.1.  P2MP TE LSPs Instantiation

   The Instantiation operation of P2MP TE LSPs is same as defined in
   section 5.3 of [RFC8281] including handling of PLSP-ID, SYMBOLIC-
   PATH-NAME TLV etc.  Rules of processing and error codes remains
   unchanged.  The N (P2MP) flag (Section 7.1) MUST be set in LSP object
   in PCInitiate message by PCE to specify the instantiation is for P2MP
   TE LSPs.  Like the PLSP-ID as per [RFC8281], the P2MP-LSP-IDENTIFIERS
   TLV SHOULD NOT be included in the LSP object in PCIntiitate message
   (as it is generated by PCC and carried in PCRpt message instead) and
   MUST be ignored on receipt.

5.6.3.2.  P2MP TE LSPs Deletion

   The deletion operation of P2MP TE LSPs is same as defined in section
   5.4 of [RFC8281] by sending an LSP Initiate Message with an LSP
   object carrying the PLSP-ID of the LSP to be removed and an SRP
   object with the R flag set (LSP-REMOVE as per section 5.2 of
   [RFC8281]).  Rules of processing and error codes remains unchanged.







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5.6.3.3.  Adding and Pruning Leaves for the P2MP TE LSP

   Adding of new leaves and Pruning of old Leaves for the PCE initiated
   P2MP TE LSP MUST be carried in PCUpd message as per Section 6.2 for
   P2MP TE LSP extensions.  As defined in [RFC8306], leaf type = 1 for
   adding of new leaves, leaf type = 2 for pruning of old leaves of P2MP
   END-POINTS Object are used in PCUpd message.

   PCC MAY use the Incremental State Update mechanism as described in
   [RFC4875] to signal adding and pruning of leaves.

   Section 3.10 of [RFC8306] defines the error-handling procedures when
   adding new leaves to or removing old leaves from the existing P2MP
   tree for PCReq message.  The same error handling and error-codes are
   also applicable to the stateful PCE messages as described in this
   document.

5.6.3.4.  P2MP TE LSPs Delegation and Cleanup

   P2MP TE LSPs delegation and cleanup operations are same as defined in
   section 6 of [RFC8281].  Rules of processing and error codes remains
   unchanged.

6.  PCEP Message Extensions

   Message formats in this section, as those in [RFC8231], [RFC8281],
   and [RFC5440], are presented using Routing Backus-Naur Format (RBNF)
   as specified in [RFC5511].

6.1.  The PCRpt Message

   As per Section 6.1 of [RFC8231], PCRpt message is used to report the
   current state of a P2P TE LSP.  This document extends the PCRpt
   message in reporting the status of P2MP TE LSPs.

   The format of PCRpt message is as follows:















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   <PCRpt Message> ::= <Common Header>
                     <state-report-list>
   Where:

   <state-report-list> ::= <state-report>
                         [<state-report-list>]

   <state-report> ::= [<SRP>]
                       <LSP>
                       <end-point-intended-path-pair-list>
                       [<actual-attribute-list>
                       <end-point-actual-path-pair-list>]
                       [<intended-attribute-list>]

   Where:

   <end-point-intended-path-pair-list>::=
                      [<END-POINTS>]
                      [<S2LS>]
                      <intended-path>
                      [<end-point-intended-path-pair-list>]

   <end-point-actual-path-pair-list>::=
                      [<END-POINTS>]
                      [<S2LS>]
                      <actual-path>
                      [<end-point-actual-path-pair-list>]

   <intended-path> ::= (<ERO>|<SERO>)
              [<intended-path>]

   <actual-path> ::= (<RRO>|<SRRO>)
              [<actual-path>]

   <intended-attribute-list> is defined in [RFC5440] and
   extended by PCEP extensions.
   <actual-attribute-list> consists of the actual computed and
   signaled values of the <BANDWIDTH> and <metric-lists>
   objects defined in [RFC5440].


   The P2MP END-POINTS object defined in [RFC8306] is mandatory for
   specifying address of P2MP leaves grouped based on leaf types.

   o  New leaves to add (leaf type = 1)

   o  Old leaves to remove (leaf type = 2)




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   o  Old leaves whose path can be modified/reoptimized (leaf type = 3)

   o  Old leaves whose path must be left unchanged (leaf type = 4)

   When reporting the status of a P2MP TE LSP, the destinations MUST be
   grouped in END-POINTS object based on the operational status (O field
   in S2LS object) and leaf type (in END-POINTS).  This way, leaves of
   the same type that share the same operational status are grouped
   together.  For reporting the status of delegated P2MP TE LSPs leaf-
   type = 3 is used, whereas for non-delegated P2MP TE LSPs, leaf-type =
   4 is used.

   For a delegated P2MP TE LSP configuration changes are reported via
   PCRpt message.  For example, adding of new leaves END-POINTS (leaf-
   type = 1) is used where as removing of old leaves (leaf-type = 2) is
   used.

   Note that the compatibility with the [RFC8231] definition of <state-
   report> is preserved.  At least one instance of <END-POINTS> MUST be
   present in this message for P2MP LSP.

   Note that the ordering of <end-point-intended-path-pair-list>,
   <actual-attribute-list>, <end-point-actual-path-pair-list>, and
   <intended-attribute-list> is done to retain compatibility with state
   reports for the P2P LSPs as per [RFC8231].

   During state synchronization, the PCRpt message reports the status of
   the full P2MP tree.

   The S2LS object MUST be carried in PCRpt message along with END-
   POINTS object when N (P2MP) flag is set in LSP object for P2MP TE
   LSPs.  If the S2LS object is missing, the receiving PCE MUST send a
   PCErr message with Error-type=6 ("Mandatory Object missing") and
   Error-value=13 (early allocated by IANA) ("S2LS object missing").  If
   the END-POINTS object is missing, the receiving PCE MUST send a PCErr
   message with Error-type=6 ("Mandatory Object missing") and Error-
   value=3 ("END-POINTS object missing") (defined in [RFC5440].

   The S2LS object could be used in conjunction with the intended-path
   (ERO) as well as the actual-path (RRO); for the same leaf, the state
   encoded in the S2LS object associated with the actual-path MUST be
   used over the intended-path.

   If the E-bit (ERO-Compress bit) was set to 1 in the report, then the
   path will be formed by an ERO followed by a list of SEROs or RRO
   followed by a list of SRROs.





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6.2.  The PCUpd Message

   As per Section 6.2 of [RFC8231], PCUpd message is used to update P2P
   TE LSP attributes.  This document extends the PCUpd message in
   updating the attributes of a P2MP TE LSP.

   The format of a PCUpd message is as follows:


      <PCUpd Message> ::= <Common Header>
                          <update-request-list>

      Where:

      <update-request-list> ::= <update-request>
                                [<update-request-list>]

      <update-request> ::= <SRP>
                           <LSP>
                           <end-point-path-pair-list>
                           <attribute-list>

      Where:

      <end-point-path-pair-list>::=
                      [<END-POINTS>]
                      <intended-path>
                      [<end-point-path-pair-list>]

      <intended-path> ::= (<ERO>|<SERO>)
                 [<intended-path>]

      <attribute-list> is defined in [RFC5440] and
      extended by PCEP extensions.


   Note that the compatibility with the [RFC8231] definition of <update-
   request> is preserved.

   The PCC SHOULD use the make-before-break or sub-group-based
   procedures described in [RFC4875] based on a local policy decision.

   The END-POINTS object MUST be carried in PCUpd message when N flag is
   set in LSP object for a P2MP TE LSP.  If the END-POINTS object is
   missing, the receiving PCC MUST send a PCErr message with Error-
   type=6 ("Mandatory Object missing") and Error-value=3 ("END-POINTS
   object missing") (defined in [RFC5440]).




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6.3.  The PCReq Message

   As per Section 3.4 of [RFC8306], PCReq message is used for a P2MP
   Path Computation Request.  This document extends the PCReq message
   such that a PCC MAY include the LSP object in the PCReq message if
   the stateful PCE P2MP capability has been negotiated on a PCEP
   session between the PCC and a PCE.

   The format of PCReq message is as follows:


    <PCReq Message>::= <Common Header>
                       [<svec-list>]
                       <request-list>

   where:

   <svec-list>::= <SVEC>
                  [<OF>]
                  [<metric-list>]
                  [<svec-list>]

   <request-list>::=<request>[<request-list>]

   <request>::= <RP>
                <end-point-rro-pair-list>
                [<LSP>]
                [<OF>]
                [<LSPA>]
                [<BANDWIDTH>]
                [<metric-list>]
                [<IRO>|<BNC>]
                [<LOAD-BALANCING>]


   <end-point-rro-pair-list>::= <END-POINTS>
                                [<RRO-List>[<BANDWIDTH>]]
                                [<end-point-rro-pair-list>]

   <RRO-List>::=(<RRO>|<SRRO>)[<RRO-List>]
   <metric-list>::=<METRIC>[<metric-list>]


6.4.  The PCRep Message

   As per Section 3.5 of [RFC8306], PCRep message is used for a P2MP
   Path Computation Reply.  This document extends the PCRep message such
   that a PCE MAY include the LSP object in the PCRep message if the



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   stateful PCE P2MP capability has been negotiated on a PCEP session
   between the PCC and a PCE.

   The format of PCRep message is as follows:


   <PCRep Message>::= <Common Header>
                      <response-list>

   where:

   <response-list>::=<response>[<response-list>]

   <response>::=<RP>
                [<end-point-path-pair-list>]
                [<LSP>]
                [<NO-PATH>]
                [<UNREACH-DESTINATION>]
                [<attribute-list>]

   <end-point-path-pair-list>::= [<END-POINTS>]
                                 <path>
                                 [<end-point-path-pair-list>]

   <path> ::= (<ERO>|<SERO>) [<path>]

   <attribute-list>::=[<OF>]
                      [<LSPA>]
                      [<BANDWIDTH>]
                      [<metric-list>]
                      [<IRO>]


6.5.  The PCInitiate message

   As defined in section 5.1 of [RFC8281], PCE sends a PCInitiate
   message to a PCC to recommend instantiation of a P2P TE LSP, this
   document extends the format of PCInitiate message for the creation of
   P2MP TE LSPs but the creation and deletion operations of P2MP TE LSPs
   are same to the P2P TE LSPs.

   The format of PCInitiate message is as follows:









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   <PCInitiate Message> ::= <Common Header>
                            <PCE-initiated-lsp-list>
   Where:

   <PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>
                                [<PCE-initiated-lsp-list>]

   <PCE-initiated-lsp-request> ::=
   (<PCE-initiated-lsp-instantiation>|<PCE-initiated-lsp-deletion>)

   <PCE-initiated-lsp-instantiation> ::= <SRP>
                                         <LSP>
                                         <end-point-path-pair-list>
                                         [<attribute-list>]

   <PCE-initiated-lsp-deletion> ::= <SRP>
                                    <LSP>

   Where:

   <end-point-path-pair-list>::=
                      [<END-POINTS>]
                      <intended-path>
                      [<end-point-path-pair-list>]

   <intended-path> ::= (<ERO>|<SERO>)
              [<intended-path>]

   <attribute-list> is defined in [RFC5440] and extended
   by PCEP extensions.


   The PCInitiate message with an LSP object with N flag (P2MP) set is
   used to convey operation on a P2MP TE LSP.  The SRP object is used to
   correlate between initiation requests sent by the PCE and the error
   reports and state reports sent by the PCC as described in [RFC8231].

   The END-POINTS object MUST be carried in PCInitiate message when N
   flag is set in LSP object for a P2MP TE LSP.  If the END-POINTS
   object is missing, the receiving PCC MUST send a PCErr message with
   Error-type=6 ("Mandatory Object missing") and Error-value=3 ("END-
   POINTS object missing") (defined in [RFC5440].

6.6.  Example







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6.6.1.  P2MP TE LSPs Update Request

   An LSP Update Request message is sent by an active stateful PCE to
   update the P2MP TE LSPs parameters or attributes.  An example of a
   PCUpd message for P2MP TE LSPs is described below:


              Common Header
              SRP
              LSP with P2MP flag set
              END-POINTS for leaf type 3
                ERO list

   In this example, a stateful PCE requests an update of the path taken
   to some of the leaves in a P2MP tree.  The update request uses the
   END-POINT type 3 (modified/reoptimized).  The ERO list represents the
   source to leaves path after modification.  The update message does
   not need to encode the full P2MP tree in this case.

6.6.2.  P2MP TE LSP Report

   The LSP State Report message is sent by a PCC to report or delegate
   the P2MP TE LSPs.  An example of a PCRpt message for a delegated P2MP
   TE LSPs is described below to add new leaves to an existing P2MP TE
   LSP:


              Common Header
              LSP with P2MP flag set
              END-POINTS for leaf type 1
                S2LS (O=DOWN)
                ERO list (empty)

   An example of a PCRpt message for a P2MP TE LSP is described below to
   prune leaves from an existing P2MP TE LSP:


              Common Header
              LSP with P2MP flag set
              END-POINTS for leaf type 2
                S2LS (O=UP)
                ERO list (empty)

   An example of a PCRpt message for a delegated P2MP TE LSP is
   described below to report status of leaves in an existing P2MP TE
   LSP:





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              Common Header
              SRP
              LSP with P2MP flag set
              END-POINTS for leaf type 3
                S2LS (O=UP)
                RRO list
              END-POINTS for leaf type 3
                S2LS (O=DOWN)
                ERO list (empty)

   In this example, the PCRpt message is in response to a PCUpd message
   (with corresponding SRP) object indicating some leaves that are up
   (with the actual path) and some are down.

   An example of a PCRpt message for a non-delegated P2MP TE LSP is
   described below to report status of leaves:


              Common Header
              LSP with P2MP flag set
              END-POINTS for leaf type 4
                S2LS (O=ACTIVE)
                RRO list
              END-POINTS for leaf type 4
                S2LS (O=DOWN)
                ERO list (empty)

6.6.3.  P2MP TE LSPs Initiation Request

   An LSP Initiation Request message is sent by an stateful PCE to
   create a P2MP TE LSP.  An example of a PCInitiate message for a P2MP
   TE LSP is described below:


              Common Header
              SRP
              LSP with P2MP flag set
              END-POINTS for leaf type 1
                ERO list

   In this example, a stateful PCE request creation of a P2MP TE LSP.
   The initiation request uses the END-POINT type 1 (new leaves).  The
   ERO list represents the source to leaves path.  The initiate message
   encodes the full P2MP tree in this case.







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7.  PCEP Object Extensions

   The new PCEP TLVs defined in this document are in compliance with the
   PCEP TLV format defined in [RFC5440].

7.1.  Extension of LSP Object

   The LSP Object is defined in Section 7.3 of [RFC8231].  It specifies
   the PLSP-ID to uniquely identify an LSP that is constant for the life
   time of a PCEP session.  Similarly for a P2MP tunnel, the PLSP-ID
   identify a P2MP TE LSP uniquely.  This document adds the following
   flags to the LSP Object:

   N (P2MP flag - 1 bit):  If the N flag is set to 1, it indicates that
      the message is for a P2MP TE LSP.

   F (Fragmentation flag - 1 bit):  If the F flag is unset (0), it
      indicates that the LSP is not fragmented or it is the last piece
      of the fragmented LSP.  If the F flag is set to 1, it indicates
      that the LSP is fragmented and this is not the last piece of the
      fragmented LSP.  The receiver needs to wait for additional
      fragments until it receives an LSP with the same PLSP-ID and with
      the F-bit set to 0.  See Section 8 for further details.

   E (ERO-compression flag - 1 bit):  If the E flag is set to 1, it
      indicates the route is in compressed format (that is, Secondary
      Explicit Route Object (SERO) and Secondary Record Route Object
      (SRRO) objects [RFC8306] are in use).

   The flags defined in this section (N, F, E flags) are used in PCRpt,
   PCUpd, or PCInitiate message.  In case of PCReq and PCRep message,
   these flags have no meaning and thus MUST be ignored.  The
   corresponding flags in the RP (Request Parameters) object are used as
   described in [RFC8231].

7.2.  P2MP-LSP-IDENTIFIERS TLV

   If the N bit is set on a PCRpt but the P2MP-LSP-IDENTIFIER TLV is
   absent, the PCE MUST respond with a PCErr message carrying error-type
   6 ("mandatory object missing") and error-value 14 (early allocated by
   IANA) ("P2MP-LSP-IDENTIFIER TLV missing") and close the PCEP session.

   The P2MP-LSP-IDENTIFIERS TLV MAY be included in the LSP object in the
   PCUpd message for P2MP TE LSPs.  The special value of all zeros for
   this TLV is used to refer to all paths pertaining to a particular
   PLSP-ID.





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   There are two P2MP-LSP-IDENTIFIERS TLVs, one for IPv4 and one for
   IPv6.

   The format of the IPV4-P2MP-LSP-IDENTIFIERS TLV is shown in the
   Figure 6:

    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=32             |           Length=16           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   IPv4 Tunnel Sender Address                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             LSP ID            |           Tunnel ID           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Extended Tunnel ID                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             P2MP ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



              Figure 6: IPV4-P2MP-LSP-IDENTIFIERS TLV format

   The type (16-bits) of the TLV is 32 (early allocated by IANA).  The
   length (16-bits) has a fixed value of 16 octets.  The value contains
   the following fields:

   IPv4 Tunnel Sender Address:  contains the sender node's IPv4 address,
      as defined in [RFC3209], Section 4.6.2.1 for the LSP_TUNNEL_IPv4
      Sender Template Object.

   LSP ID:  contains the 16-bits 'LSP ID' identifier defined in
      [RFC3209], Section 4.6.2.1 for the LSP_TUNNEL_IPv4 Sender Template
      Object.

   Tunnel ID:  contains the 16-bits 'Tunnel ID' identifier defined in
      [RFC3209], Section 4.6.1.1 for the LSP_TUNNEL_IPv4 Session Object.

   Extended Tunnel ID:  contains the 32-bits 'Extended Tunnel ID'
      identifier defined in [RFC3209], Section 4.6.1.1 for the
      LSP_TUNNEL_IPv4 Session Object.

   P2MP ID:  contains the 32-bits 'P2MP ID' identifier defined in
      Section 19.1.1 of [RFC4875] for the P2MP LSP Tunnel IPv4 SESSION
      Object.





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   The format of the IPV6-P2MP-LSP-IDENTIFIERS TLV is shown in the
   Figure 7:


    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=33             |           Length=40           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                  IPv6 tunnel sender address                   |
   +                          (16 octets)                          +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             LSP ID            |           Tunnel ID           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +                                                               +
   |                       Extended Tunnel ID                      |
   +                          (16 octets)                          +
   |                                                               |
   +                                                               +
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             P2MP ID                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


              Figure 7: IPV6-P2MP-LSP-IDENTIFIERS TLV format

   The type (16-bits) of the TLV is 33 (early allocated by IANA).  The
   length (16-bits) has a fixed length of 40 octets.  The value contains
   the following fields:

   IPv6 Tunnel Sender Address:  contains the sender node's IPv6 address,
      as defined in [RFC3209], Section 4.6.2.2 for the LSP_TUNNEL_IPv6
      Sender Template Object.

   LSP ID:  contains the 16-bits 'LSP ID' identifier defined in
      [RFC3209], Section 4.6.2.2 for the LSP_TUNNEL_IPv6 Sender Template
      Object.

   Tunnel ID:  contains the 16-bits 'Tunnel ID' identifier defined in
      [RFC3209], Section 4.6.1.2 for the LSP_TUNNEL_IPv6 Session Object.




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   Extended Tunnel ID:  contains the 128-bits 'Extended Tunnel ID'
      identifier defined in [RFC3209], Section 4.6.1.2 for the
      LSP_TUNNEL_IPv6 Session Object.

   P2MP ID:  As defined above in IPV4-P2MP-LSP-IDENTIFIERS TLV.

   Tunnel ID remains constant over the life time of a tunnel.

7.3.  S2LS Object

   The S2LS (Source-to-Leaves) Object is used to report state of one or
   more destinations (leaves) encoded within the END-POINTS object for a
   P2MP TE LSP.  It MUST be carried in PCRpt message along with END-
   POINTS object when N flag is set in LSP object.

   S2LS Object-Class is 41 (Early allocated by IANA).

   S2LS Object-Types is 1.

   The format of the S2LS object is shown in the following figure:


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                             Flags                       |    O|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                      Optional TLVs                          //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                       Figure 8: S2LS object format

   Flags(32-bits):  the following flags are currently defined -

   O(Operational - 3 bits)  the O Field represents the operational
      status of the group of destinations.  The values are as per
      Operational field in LSP object defined in Section 7.3 of
      [RFC8231].

   Unassigned bits are reserved for future uses.  They MUST be set to 0
   on transmission and MUST be ignored on receipt.

   When N flag is set in LSP object then the O field in LSP object
   represents the operational status of the full P2MP TE LSP and the O
   field in S2LS object represents the operational status of a group of



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   destinations encoded within the END-POINTS object.  If there is a
   conflict between the O field in the LSP and the S2LS object (for
   example, O field in LSP corresponds to down whereas the O field in
   S2LS is up), the PCEP speaker MUST generate an error with error-type
   10 ("Reception of an invalid object") and error-value TBD1 (to be
   allocated by IANA) ("Mis-match of O field in S2LS and LSP object").

   Future documents might define optional TLVs that could be included in
   the S2LS Object.

8.  Message Fragmentation

   The total PCEP message length, including the common header, is
   (2^16)-1 bytes.  In certain scenarios the P2MP report and update
   request may not fit into a single PCEP message (e.g. initial report
   or update).  The F flag is used in the LSP object to signal that the
   initial report, update, or initiate message was too large to fit into
   a single message and will be fragmented into multiple messages.  In
   order to identify the single report or update each message will use
   the same PLSP-ID.  In order to identify that a series of PCInitiate
   messages represents a single Initiate, each message will use the same
   PLSP-ID (in this case 0) and SRP-ID-number.

   The fragmentation procedure described below for report or update
   message is similar to [RFC8306] which describes request and response
   message fragmentation.

8.1.  Report Fragmentation Procedure

   If the initial report is too large to fit into a single report
   message, the PCC will split the report over multiple messages.  Each
   message sent to the PCE, except the last one, will have the F flag
   set in the LSP object to signify that the report has been fragmented
   into multiple messages.  In order to identify that a series of report
   messages represents a single report, each message will use the same
   PLSP-ID.

   The Error-Type value 18 ("P2MP Fragmentation Error") is used to
   report any error associated with the fragmentation of a P2MP PCEP
   message.  A new error-value 2 (early allocated by IANA) indicates
   "Fragmented report failure" and is used if a PCE does not receive the
   last part of the fragmented message.

8.2.  Update Fragmentation Procedure

   Once the PCE computes and updates a path for some or all leaves in a
   P2MP TE LSP, an update message is sent to the PCC.  If the update is
   too large to fit into a single update message, the PCE will split the



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   update over multiple messages.  Each update message sent by the PCE,
   except the last one, will have the F flag set in the LSP object to
   signify that the update has been fragmented into multiple messages.
   In order to identify that a series of update messages represents a
   single update, each message will use the same PLSP-ID and SRP-ID-
   number.

   The Error-Type value 18 ("P2MP Fragmentation Error") is used to
   report any error associated with the fragmentation of a P2MP PCEP
   message.  A new error-value 3 (early allocated by IANA) indicates
   "Fragmented update failure" and is used if a PCC does not receive the
   last part of the fragmented message.

8.3.  PCIntiate Fragmentation Procedure

   Once the PCE initiates to set up a P2MP TE LSP, a PCInitiate message
   is sent to the PCC.  If the PCInitiate is too large to fit into a
   single PCInitiate message, the PCE will split the PCInitiate over
   multiple messages.  Each PCInitiate message sent by the PCE, except
   the last one, will have the F flag set in the LSP object to signify
   that the PCInitiate has been fragmented into multiple messages.  In
   order to identify that a series of PCInitiate messages represents a
   single Initiate, each message will use the same PLSP-ID (in this case
   0) and SRP-ID-number.

   The Error-Type value 18 ("P2MP Fragmentation Error") is used to
   report any error associated with the fragmentation of a P2MP PCEP
   message.  A new error-value 4 (early allocated by IANA) indicates
   "Fragmented instantiation failure" and is used if a PCC does not
   receive the last part of the fragmented message.

9.  Non-Support of P2MP TE LSPs for Stateful PCE

   The PCEP extensions described in this document for stateful PCEs with
   P2MP capability MUST NOT be used if PCE has not advertised its
   stateful capability with P2MP as per Section 5.2.  If the PCEP
   Speaker on the PCC supports the extensions of this draft (understands
   the P2MP flag in the LSP object) but did not advertise this
   capability, then upon receipt of PCUpd message from the PCE, it
   SHOULD generate a PCErr with error-type 19 ("Invalid Operation"),
   error-value 12 (early allocated by IANA) ("Attempted LSP Update
   Request for P2MP if active stateful PCE capability for P2MP was not
   advertised") and terminate the PCEP session.  If the PCEP Speaker on
   the PCE supports the extensions of this draft (understands the P2MP
   flag in the LSP object) but did not advertise this capability, then
   upon receipt of a PCRpt message from the PCC, it SHOULD generate a
   PCErr with error-type 19 ("Invalid Operation"), error-value 11 (early
   allocated by IANA) ("Attempted LSP State Report for P2MP if stateful



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   PCE capability for P2MP was not advertised") and it SHOULD terminate
   the PCEP session.

   If a Stateful PCE receives a P2MP TE LSP report message and the PCE
   does not understand the P2MP flag in the LSP object, and therefore
   the PCEP extensions described in this document, then the Stateful PCE
   would act as per [RFC8231].

   The PCEP extensions described in this document for PCC or PCE with
   instantiation capability for P2MP TE LSPs MUST NOT be used if PCC or
   PCE has not advertised its stateful capability with Instantiation and
   P2MP capability as per Section 5.2.  If the PCEP Speaker on the PCC
   supports the extensions of this draft (understands the P (P2MP-LSP-
   INSTANTIATION-CAPABILITY) flag) but did not advertise this
   capability, then upon receipt of PCInitiate message from the PCE, it
   SHOULD generate a PCErr with error-type 19 ("Invalid Operation"),
   error-value 13 (early allocated by IANA) ("Attempted LSP
   Instantiation Request for P2MP if stateful PCE instantiation
   capability for P2MP was not advertised") and terminate the PCEP
   session..

10.  Manageability Considerations

   All manageability requirements and considerations listed in
   [RFC5440], [RFC8306], [RFC8231], and [RFC8281] apply to PCEP
   extensions defined in this document.  In addition, requirements and
   considerations listed in this section apply.

10.1.  Control of Function and Policy

   A PCE or PCC implementation MUST allow configuring the stateful PCEP
   capability, the LSP Update capability, and the LSP Initiation
   capability for P2MP LSPs.

10.2.  Information and Data Models

   The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to
   include advertised P2MP stateful capabilities, P2MP synchronization
   status, and delegation status of P2MP LSP etc.  The statistics module
   should also count P2MP LSP related data.

10.3.  Liveness Detection and Monitoring

   Mechanisms defined in this document do not imply any new liveness
   detection and monitoring requirements in addition to those already
   listed in [RFC5440].





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10.4.  Verify Correct Operations

   Mechanisms defined in this document do not imply any new operation
   verification requirements in addition to those already listed in
   [RFC5440], [RFC8306], [RFC8231], and [RFC8281].

10.5.  Requirements On Other Protocols

   Mechanisms defined in this document do not imply any new requirements
   on other protocols.

10.6.  Impact On Network Operations

   Mechanisms defined in this document do not have any impact on network
   operations in addition to those already listed in [RFC5440],
   [RFC8306], [RFC8231], and [RFC8281].

   Stateful PCE feature for P2MP LSP would help with network operations.

11.  IANA Considerations

   This document requests IANA to confirm the early allocation of the
   code-points for the protocol elements defined in this document.

11.1.  PCE Capabilities in IGP Advertisements

   IANA is requested to confirm the early allocation for the new bits in
   the OSPF Parameters "PCE Capability Flags" registry, as follows:



                 Bit      Meaning               Reference
                 13       Active Stateful       [This.I-D]
                          PCE with P2MP
                 14       Passive Stateful      [This.I-D]
                          PCE with P2MP
                 15       Stateful PCE          [This.I-D]
                          Initiation with P2MP


11.2.  STATEFUL-PCE-CAPABILITY TLV

   The STATEFUL-PCE-CAPABILITY TLV is defined in [RFC8231] and the
   'STATEFUL-PCE-CAPABILITY TLV Flag Field' subregistry was created to
   manage the flags in the TLV.  IANA is requested to confirm the early
   allocation of the following code-points in the aforementioned
   registry.




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       Bit    Description           Reference

       25      P2MP-CAPABILITY      [This.I-D]
       24      P2MP-LSP-UPDATE-     [This.I-D]
               CAPABILITY
       23      P2MP-LSP-            [This.I-D]
               INSTANTIATION-
               CAPABILITY



11.3.  LSP Object

   The LSP object is defined in [RFC8231] and the 'LSP Object Flag
   Field' subregistry was created to manage the Flags field of the LSP
   object.

   IANA is requested to confirm the early allocation of the following
   code-points in the aforementioned registry.


       Bit    Description           Reference

       3       P2MP                 [This.I-D]
       2       Fragmentation        [This.I-D]



   Additionally, IANA is requested to allocate an additional code-point
   in this registry.


       Bit    Description           Reference

       TBD    ERO-compression       [This.I-D]



11.4.  PCEP-Error Object

   IANA is requested to confirm the early allocation of the new error
   values within the "PCEP-ERROR Object Error Types and Values" sub-
   registry of the PCEP Numbers registry, as follows:








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       Error-Type  Meaning
          6        Mandatory Object missing [RFC5440]
                     Error-value=13: S2LS object missing
                     Error-value=14: P2MP-LSP-IDENTIFIERS TLV missing
          18       P2MP Fragmentation Error [RFC8306]
                     Error-value= 2. Fragmented Report
                         failure
                     Error-value= 3. Fragmented Update
                         failure
                     Error-value= 4. Fragmented Instantiation
                         failure
          19       Invalid Operation [RFC8231]
                     Error-value= 11. Attempted LSP State Report
                         for P2MP if stateful PCE capability
                         for P2MP was not advertised
                     Error-value= 12. Attempted LSP Update Request
                         for P2MP if active stateful PCE capability
                         for P2MP was not advertised
                     Error-value= 13. Attempted LSP Instantiation
                         Request for P2MP if stateful PCE
                         instantiation capability for P2MP was not
                         advertised

       Reference for all new Error-Value above is [This.I-D].




   Additionally, IANA is requested to allocate an additional code-point
   in this registry.


       Error-Type  Meaning
          10       Reception of an invalid object [RFC5440]
                     Error-value=TBD1: Mis-match of O field in S2LS
                         and  LSP object

       Reference for all new Error-Value above is [This.I-D].




11.5.  PCEP TLV Type Indicators

   IANA is requested to confirm the early allocation of the following
   code-points in the existing "PCEP TLV Type Indicators" registry as
   follows:




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          Value     Meaning                           Reference
            32      P2MP-IPV4-LSP-IDENTIFIERS         [This.I-D]
            33      P2MP-IPV6-LSP-IDENTIFIERS         [This.I-D]



11.6.  PCEP object

   IANA is requested to confirm the early allocation for the new object-
   class values and object types within the "PCEP Objects" sub-registry
   of the PCEP Numbers registry, as follows.


       Object-Class Value  Name                               Reference

               41          S2LS                               [This.I-D]
                           Object-Type
                           0: Reserved
                           1: S2LS



11.7.  S2LS object

   This document requests that a new sub-registry, named "S2LS Object
   Flag Field", is created within the "Path Computation Element Protocol
   (PCEP) Numbers" registry to manage the 32-bits Flag field of the S2LS
   object.  New values are to be assigned by Standards Action [RFC8126].
   Each bit should be tracked with the following qualities:

   o  Bit number (counting from bit 0 as the most significant bit)

   o  Capability description

   o  Defining RFC

   The following values are defined in this document:


                    Bit     Description           Reference

                   29-31    Operational (3-bits)  [This.I-D]
                    0-28    Unassigned








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12.  Security Considerations

   The stateful operations on P2MP TE LSPs are more CPU-intensive and
   also utilize more bandwidth on wire (in comparison to P2P TE LSPs).
   If a rogue PCC were able to request unauthorized stateful PCE
   operations then it may be able to mount a DoS attack against a PCE,
   which would disrupt the network and deny service to other PCCs.
   Consequently, it is important that implementations conform to the
   relevant security requirements of [RFC5440], [RFC8306] and [RFC8231],
   and [RFC8281].  Securing the PCEP session using Transport Layer
   Security (TLS) [RFC8253], as per the recommendations and best current
   practices in [RFC7525], is RECOMMENDED.

13.  Acknowledgments

   Thanks to Quintin Zhao, Avantika and Venugopal Reddy for the review
   comments.

   Thanks to Adrian Farrel (and Jonathan Hardwick) for the review as
   document shepherds.

   Thanks to Andy Malis for the RTGDIR review.

14.  References

14.1.  Normative References

   [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>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <https://www.rfc-editor.org/info/rfc3209>.

   [RFC5088]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "OSPF Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5088, DOI 10.17487/RFC5088,
              January 2008, <https://www.rfc-editor.org/info/rfc5088>.

   [RFC5089]  Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
              Zhang, "IS-IS Protocol Extensions for Path Computation
              Element (PCE) Discovery", RFC 5089, DOI 10.17487/RFC5089,
              January 2008, <https://www.rfc-editor.org/info/rfc5089>.





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   [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>.

   [RFC5511]  Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
              Used to Form Encoding Rules in Various Routing Protocol
              Specifications", RFC 5511, DOI 10.17487/RFC5511, April
              2009, <https://www.rfc-editor.org/info/rfc5511>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [RFC8232]  Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X.,
              and D. Dhody, "Optimizations of Label Switched Path State
              Synchronization Procedures for a Stateful PCE", RFC 8232,
              DOI 10.17487/RFC8232, September 2017,
              <https://www.rfc-editor.org/info/rfc8232>.

   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

   [RFC8306]  Zhao, Q., Dhody, D., Ed., Palleti, R., and D. King,
              "Extensions to the Path Computation Element Communication
              Protocol (PCEP) for Point-to-Multipoint Traffic
              Engineering Label Switched Paths", RFC 8306,
              DOI 10.17487/RFC8306, November 2017,
              <https://www.rfc-editor.org/info/rfc8306>.

14.2.  Informative References

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.






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   [RFC4875]  Aggarwal, R., Ed., Papadimitriou, D., Ed., and S.
              Yasukawa, Ed., "Extensions to Resource Reservation
              Protocol - Traffic Engineering (RSVP-TE) for Point-to-
              Multipoint TE Label Switched Paths (LSPs)", RFC 4875,
              DOI 10.17487/RFC4875, May 2007,
              <https://www.rfc-editor.org/info/rfc4875>.

   [RFC5671]  Yasukawa, S. and A. Farrel, Ed., "Applicability of the
              Path Computation Element (PCE) to Point-to-Multipoint
              (P2MP) MPLS and GMPLS Traffic Engineering (TE)", RFC 5671,
              DOI 10.17487/RFC5671, October 2009,
              <https://www.rfc-editor.org/info/rfc5671>.

   [RFC7525]  Sheffer, Y., Holz, R., and P. Saint-Andre,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
              2015, <https://www.rfc-editor.org/info/rfc7525>.

   [RFC8051]  Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
              Stateful Path Computation Element (PCE)", RFC 8051,
              DOI 10.17487/RFC8051, January 2017,
              <https://www.rfc-editor.org/info/rfc8051>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,
              <https://www.rfc-editor.org/info/rfc8253>.

   [I-D.ietf-pce-pcep-yang]
              Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
              YANG Data Model for Path Computation Element
              Communications Protocol (PCEP)", draft-ietf-pce-pcep-
              yang-09 (work in progress), October 2018.











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Appendix A.  Contributor Addresses

   Yuji Kamite
   NTT Communications Corporation
   Granpark Tower
   3-4-1 Shibaura, Minato-ku
   Tokyo  108-8118
   Japan

   EMail: y.kamite@ntt.com

Authors' Addresses

   Udayasree Palle
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   EMail: udayasreereddy@gmail.com


   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka  560066
   India

   EMail: dhruv.ietf@gmail.com


   Yosuke Tanaka
   NTT Communications Corporation
   Granpark Tower
   3-4-1 Shibaura, Minato-ku
   Tokyo  108-8118
   Japan

   EMail: yosuke.tanaka@ntt.com


   Vishnu Pavan Beeram
   Juniper Networks

   EMail: vbeeram@juniper.net






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