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Multicast Tree Setup via PCEP
draft-li-pce-multicast-01

Document Type Active Internet-Draft (individual)
Authors Huanan Li , Aijun Wang , Zhaohui (Jeffrey) Zhang , Huaimo Chen , Ran Chen
Last updated 2022-03-20
Replaces draft-li-pce-based-bier
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draft-li-pce-multicast-01
pce                                                                H. Li
Internet-Draft                                                   A. Wang
Intended status: Standards Track                           China Telecom
Expires: September 21, 2022                                     Z. Zhang
                                                        Juniper Networks
                                                                 H. Chen
                                                               Futurewei
                                                                 R. Chen
                                                         ZTE Corporation
                                                          March 20, 2022

                     Multicast Tree Setup via PCEP
                       draft-li-pce-multicast-01

Abstract

   Multicast forwarding requires per-tree state on certain nodes.  Even
   with BIER, per-tree state is needed on ingress/egress BIER routers
   (though not needed on transit BIER routers).  This documents
   specifies PCEP protocol to collect tree information (e.g. root, leaf,
   constraints) to allow a PCE to calculate a tree, and the procedures
   to set up per-tree forwarding state on relevant nodes for various
   multicast trees and various replication technologies.

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
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   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 September 21, 2022.

Copyright Notice

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

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   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
   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
   2.  Overview  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Different Multicast Trees . . . . . . . . . . . . . . . .   4
       2.1.1.  IP Multicast  . . . . . . . . . . . . . . . . . . . .   4
       2.1.2.  mLDP/RSVP-TE P2MP Tunnels . . . . . . . . . . . . . .   4
       2.1.3.  SR-P2MP Tunnels . . . . . . . . . . . . . . . . . . .   5
     2.2.  Different Replication Technologies  . . . . . . . . . . .   5
     2.3.  Tree Information Discovery  . . . . . . . . . . . . . . .   6
       2.3.1.  Root node Discovery . . . . . . . . . . . . . . . . .   6
       2.3.2.  Leaf node Discovery . . . . . . . . . . . . . . . . .   7
     2.4.  Multicast Tree  . . . . . . . . . . . . . . . . . . . . .   7
       2.4.1.  Labeled Tree  . . . . . . . . . . . . . . . . . . . .   8
       2.4.2.  BIER Tree . . . . . . . . . . . . . . . . . . . . . .   8
     2.5.  Multicast Statistics  . . . . . . . . . . . . . . . . . .   8
   3.  PCEP Object Formats . . . . . . . . . . . . . . . . . . . . .   9
     3.1.  OPEN Object . . . . . . . . . . . . . . . . . . . . . . .   9
       3.1.1.  STATEFUL-PCE-CAPABILITY TLV . . . . . . . . . . . . .   9
       3.1.2.  PCECC Capability sub-TLV  . . . . . . . . . . . . . .  10
     3.2.  PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . .  10
     3.3.  Multicast Source Registration Object  . . . . . . . . . .  10
       3.3.1.  Multicast Address TLV . . . . . . . . . . . . . . . .  11
       3.3.2.  mLDP FEC TLV  . . . . . . . . . . . . . . . . . . . .  12
       3.3.3.  VPN Information TLV . . . . . . . . . . . . . . . . .  12
     3.4.  Multicast Receiver Information Object . . . . . . . . . .  12
       3.4.1.  BFR Information TLV . . . . . . . . . . . . . . . . .  13
     3.5.  CCI Object  . . . . . . . . . . . . . . . . . . . . . . .  14
       3.5.1.  Tree Label TLV  . . . . . . . . . . . . . . . . . . .  14
       3.5.2.  VPN Forwarding Identifier TLV . . . . . . . . . . . .  14
     3.6.  Tree Forwarding State Synchronization Object  . . . . . .  15
       3.6.1.  BIER Attribute TLV  . . . . . . . . . . . . . . . . .  15
     3.7.  Multicast Receiver Statistics Object  . . . . . . . . . .  16
   4.  Message Formats . . . . . . . . . . . . . . . . . . . . . . .  16
     4.1.  PCRpt message . . . . . . . . . . . . . . . . . . . . . .  16
     4.2.  PCInitiate message  . . . . . . . . . . . . . . . . . . .  17
     4.3.  PCUpd message . . . . . . . . . . . . . . . . . . . . . .  17
   5.  Example Workflow  . . . . . . . . . . . . . . . . . . . . . .  18

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     5.1.  Multicast Tree Discovery  . . . . . . . . . . . . . . . .  18
     5.2.  Multicast Tree Path Establishment and Update  . . . . . .  18
       5.2.1.  Labeled Tree  . . . . . . . . . . . . . . . . . . . .  19
       5.2.2.  BIER Tree . . . . . . . . . . . . . . . . . . . . . .  19
     5.3.  Multicast Statistics Synchronization  . . . . . . . . . .  21
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  22
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  22
     7.1.  MULTICAST-STATE-CAPABILITY  . . . . . . . . . . . . . . .  22
     7.2.  PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . .  22
     7.3.  New Objects . . . . . . . . . . . . . . . . . . . . . . .  22
     7.4.  New TLVs  . . . . . . . . . . . . . . . . . . . . . . . .  23
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  23
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  23
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  23
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  25
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  26

1.  Introduction

   Currently, multicast management information is mainly signaled by PIM
   [RFC2362], mLDP [RFC6388] or BGP [RFC6514].  The trees/tunnels are
   set up using the "receiver-initiated join" technique of PIM/mLDP, hop
   by hop from downstream routers towards the root.  The BGP messages
   are either sent hop by hop between downstream routers and their
   upstream neighbors, or can be reflected by Route Reflectors (RRs).
   The signaling is the interaction between routers and cannot be
   managed in a unified manner.

   As an alternative to each hop independently determining its upstream
   router and signaling upstream towards the root (following PIM/mLDP
   model), the entire tree can be calculated by a centralized
   controller, and the signaling can be entirely done from the
   controller.

   [RFC4655] defines a stateful PCE to be one in which the PCE maintains
   "strict synchronization between the PCE and not only the network
   states (in term of topology and resource information), but also the
   set of computed paths and reserved resources in use in the network."
   [RFC8231] specifies a set of extensions to PCEP to support state
   synchronization between PCCs and PCEs.

   The controller can serve as a PCE to centrally manage multicast trees
   and establish states on all tree nodes serving as PCC.  This document
   defines PCEP objects and TLVs to accomplish the multicast source
   registration/revocation, receiver discovery, multicast tree state
   update etc. functions.

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2.  Overview

2.1.  Different Multicast Trees

   This section discusses various multicast trees like IP, mLDP, SR-P2MP
   - each with its own tree identification.

2.1.1.  IP Multicast

   As stated in [RFC1112], an IP multicast packet's destination address
   is a Multicast Group Address and it follows either a source specific
   tree rooted at the First Hop Router (FHR) or a shared tree rooted at
   a Rendezvous Point (RP) [RFC7761].  Each tree is identified by a
   (source address, group address) pair, where the source address MAY be
   a wildcard in case of the shared tree.  This identification, which is
   often referred to as (s, g) or (*, g), is used in both forwarding
   plane as well as in control plane that sets up the tree, e.g., using
   Protocol Independ Multicast (PIM) [RFC7761] [RFC5015].

   Each node on the tree needs to have corresponding forwarding plane
   state used to forward corresponding traffic and control plane state
   that is used to set up a tree.  Depending on the number of (s, g)
   and/or (*, g) trees that a routing domain need to support, serious
   scaling/convergence problems MAY result.

2.1.2.  mLDP/RSVP-TE P2MP Tunnels

   Quite often, some different multicast trees are used for similar
   purposes and the tree structure are identical or very similar.  For
   example, in an IPTV application, many channels MAY need to be sent
   from the same headend router to the same set of edge routers close to
   receivers.

   In that case, a set of IP multicast trees can be transported over a
   fewer set of MPLS P2MP tunnels - either mLDP [RFC6388] or RSVP-TE
   P2MP [RFC4875] tunnels - across an MPLS domain.  Inside the MPLS
   domain, there is no IP multicast tree state but only fewer state for
   the P2MP tunnels.  Outside the MPLS domain, those IP multicast trees
   still have their per-tree state on each tree node.

   An mLDP tree is identified by an mLDP FEC in the control plane.  In
   the context of PCEP signaling, part of or an entire mLDP tunnel can
   be set up using PCEP from a PCE instead of using hop-by-hop mLDP
   signaling.  In this case the only relevance to mLDP is that mLDP FEC
   is used to identify the tunnel.

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   A RSVP-TE P2MP tree is identified by a RSVP Session object in the
   control plane.  While in theory it can also be set up via PCEP
   signaling from a PCE, it is outside the scope of this document.

   In the forwarding plane, there is no difference between an mLDP
   tunnel and a RSVP-TE P2MP tunnel.  A tree is identified by a label -
   incoming labeled traffic is replicated to a bunch of downstream nodes
   with a label that identifies the tree to the downstream nodes.

2.1.3.  SR-P2MP Tunnels

   Segment Routing (SR) [RFC8402] has two principles:

   1.  No per-flow/tunnel state inside an SR domain

   2.  Optional but perferred use of controllers

   When it comes to multicast, the only technologies that sticks to
   principle #1 is BIER [RFC8279], which does not use per-tree state for
   forwarding.

   SR-P2MP [I-D.ietf-pim-sr-p2mp-policy]
   [I-D.ietf-spring-sr-replication-segment] sticks to principle #2 only,
   in that PCEs are used to calculate a multicast tree subject to
   constraints and then direct signaling from PCEs are used to set up
   the tree instead of using mLDP/RSVP signaling, but per-tree state is
   still used.

   In the control plane, an SR-P2MP is identified by a (root-id, tree-
   id) tuple.  In an SR-MPLS forwarding plane, an SR-P2MP tunnel is not
   different from mLDP/RSVP-TE P2MP tunnel at all, though the tree-
   identifying label is called a tree sid.

   In an SRv6 forwarding plane, the tree sid is embedded as part of an
   IPv6 address.

2.2.  Different Replication Technologies

   For any kind of multicast trees mentioned above, on a particular tree
   node A, an incoming packet needs to replicated to a set of downstream
   nodes B/C/D/E.  Note that the upstream and downstream nodes MAY be
   directly connected or they can be reached via a set of P2P/MP2P
   tunnels, P2MP tunnels, or via BIER.  In the latter case, intermediate
   nodes do not maintain the per-tree state but they do need to maintain
   state for the transporting tunnels or BIER.

   Now on node A/B/C/D/E, per-tree replication state needs to be set up.
   In particular on A, depending on the method used to replicate to

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   B/C/D/E, (a combination of) the following replication branches are
   needed:

   o  A set of outgoing interfaces for native IP forwarding to directly
      connected nodes from the B/C/D/E set in case of IP multicast tree,
      and/or,

   o  A set of P2P/MP2P/P2MP tunnels to reach indirectly connected nodes
      from the B/C/D/E set, and/or,

   o  A BIER bitstring and relevant BIER information to reach some nodes
      from the B/C/D/E set

   In the latter two cases, the replication branches also need relevant
   information to identify to B/C/D/E which tree a packet is for (e.g.,
   a label for an mLDP or SR-P2MP tree).

2.3.  Tree Information Discovery

   When a PCE calculates a multicast tree, it needs to collect the tree
   information like root, leaves and calculation constraints.  This MAY
   be provided to the PCE via a southbound (wrt the PCE) interface from
   an orchestrator or via northbound PCEP signaling from some PCC nodes
   (e.g. the root and leaf nodes of the tree).  The PCE MAY also
   participate overlay signaling protocols to collect the information
   (e.g., [I-D.zzhang-mvpn-evpn-controller]).

   This document only covers the northbound PCEP signaling.  The two
   other methods mentioned above are out of scope of this document.

   Whether it is an IP Multicast or mLDP/SR-P2MP Tree, the root, leaves
   and calculation constraints are encoded the same way but associated
   with different tree identifications in the PCEP signaling.
   Specifically, the root and leaves are encoded as IP addresses.

   The leaf information can be encoded as a full set of leaves or as
   addition/removal delta.

2.3.1.  Root node Discovery

   When a multicast source accesses to a First Hop Router (FHR), the FHR
   originates a PCRpt message carrying the Multicast Source Registration
   (MSR) object defined in Section 3.3, which provides FHR information.
   FHR, as PCC, delegate the controller as PCE to calculate multicast
   tree.  In the sent PCRpt message, the D bit of LSP Object is set to
   1.

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2.3.2.  Leaf node Discovery

   For IP multicast, Last Hop Router (LHR) MAY convert the multicast
   source and group address carried in the IGMP Join/Leave messages sent
   by local hosts and VPN information corresponding to local hosts into
   PCRpt messages and report these information to the controller.
   Similar to IGMP messages, PIM messages from other domains can also be
   used as receiver information and be converted into PCRpt messages to
   be reported to the controller.

   For mLDP and SR-P2MP multicast, The corresponding tree identifiers
   can also be carried in PCRpt messages and reported to the controller.

   When the first receiver accesses a Last Hop Router (LHR) to join a
   multicast tree, or when the last receiver leaves the LHR, the LHR
   originates a PCRpt message carrying the Multicast Receiver
   Information (MRI) object defined in Section 3.4, which provides LHR
   information.

   If the receivers locate in different VPN domains, the VPN information
   associated with the multicast source and multicast destination should
   also be reported by the LHR and FHR.  The VPN information reported by
   LHRs SHOULD be consistent.

2.4.  Multicast Tree

   The multicast trees are established with the FHRs of the multicast
   source as the root of the multicast trees.  According to different
   multicast technologies, the types of multicast trees include labeled
   tree and BIER tree.  Different multicast trees correspond to
   different processing.  This section describes the state update of
   different multicast operations.

   No matter which forwarding technology is used, there is a case that
   local multicast receivers directly access to FHRs.  In this case,
   FHRs need to forward multicast data for local receivers in the way of
   native IP without other control information.

   In some scenarios, the egresses node needs a VPN forwarding
   identifier to determine which VRF to forward the packet to.  The
   allocation of VPN forwarding identifier is performed by controller.
   The scenario of egress assigning VPN tags has not been considered
   yet.  Controller sends the VPN forwarding identifier to ingress and
   instructs ingress to encapsulate it.  The VPN Forwarding Label may be
   MPLS label or SRv6 segment.

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2.4.1.  Labeled Tree

   For a Labeled multicast tree, whether the forwarding is based on
   native IP, mLDP or SR-P2MP tunnel, each node needs a tree label to
   identify a multicast tree.  There are three options for tree label
   assignment:

   o  From each router's SRLB that the controller learns

   o  From the common SRGB that the controller learns

   o  From the controller's local label space

   The detailed instruction is as per
   [I-D.ietf-bess-bgp-multicast-controller].  Section 3.5.1 defines two
   new TLVs to extend the CCI Object-Type support the tree label and VPN
   Label.

   The operations for initiating multicast tree LSPs and
   downloadinglabels are consistent with [I-D.ietf-pce-sr-p2mp-policy].

2.4.2.  BIER Tree

   Different from other forwarding technologies, BIER does not need the
   transit nodes to maintain the multicast state, and only needs to
   forward and encapsulate the packets according to the BitString and
   BIFT.  BIFT information can be learned by IGP.  For each node of a
   sub-domain, the BIFT can be configured locally or allocated by BGP
   controller or PCE.  Allocation by PCE is as per
   [I-D.chen-pce-pcep-extension-pce-controller-bier].

   After receiving the BFR information reported from LHRs, the
   controller combine BFR information of LHRs into a BitString to guide
   multicast data forwarding.

   The controller (PCE) sends the BitString to the FHR via PCInitiate or
   PCUpd message carrying Tree Forwarding State Synchronization (TFSS)
   object defined in Section 3.6 to inform the FHR to forward multicast
   data for a specific multicast tree according to the BitString, and
   the tree identifier is (*, g) or (s, g) tuple.  Controller also needs
   to inform FHR to encapsulate VPN forwarding identifier so that LHRs
   can forward multicast data to specific VRF accordingly.

2.5.  Multicast Statistics

   Multicast statistics are helpful for multicast service analysis and
   business development.  This section describes how to collect
   statistics about multicast users.

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   For each LHR, the statistics consist of two parts, one is the number
   of local users in the its managed domain, and the other is the number
   of other managed domains.  The sum of these two parts is the number
   of multicast data that the one LHR needs to duplicate.

   LHRs send this information to the controller via PCRpt message
   carrying Multicast Receiver Statistics (MRS) object.  LHRs need
   report this information to the controller periodically.  Once the
   statistics information of a LHR change, the LHR also needs reports to
   the controller.

   Controller collects the statistics reported by LHRs and MAY
   periodically informs the FHR of the statistics via PCRpt messages
   carrying MRS object so that the FHR can feed the statistics back to
   the multicast source.

3.  PCEP Object Formats

3.1.  OPEN Object

3.1.1.  STATEFUL-PCE-CAPABILITY TLV

   During the PCEP initialization phase, 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 [RFC8232] and [RFC8281].

   A new flag is added in this document, whose code point is TBD1:

   MULTICAST-STATE-CAPABILITY bit, if this bit is set to 1 by a PCEP
   speaker, it indicates that the PCEP speaker supports the capability
   of these new extensions as specified in this document.

   To support the multicast tree state management capabilities described
   in this document, both PCE and PCC need to set MULTICAST-STATE-
   CAPABILITY bit.  If a PCEP speaker receivers PECP message with the
   newly defined object, but without the MULTICAST-STATE-CAPABILITY bit
   set in STATEFUL-PCE-CAPABILITY TLV in the OPEN object, it MUST:

   o  Send a PCErr message with Error-Type=10(Reception of an invalid
      object) and Error-Value TBD2(MULTICAST-STATE-CAPABILITY bit is not
      set).

   o  Terminate the PCEP session.

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3.1.2.  PCECC Capability sub-TLV

   The PCECC-CAPABILITY sub-TLV is an optional TLV for use in the OPEN
   Object for PCECC capability advertisement in PATH-SETUP-TYPE-
   CAPABILITY TLV as specified in [RFC9050].

   [I-D.dhody-pce-pcep-extension-pce-controller-p2mp] adds a new flag (M
   Bit) in the PCECC-CAPABILITY sub-TLV to indicate the support for P2MP
   in PCECC, which is applicable for multicast tree described in this
   document as well.

3.2.  PATH-SETUP-TYPE TLV

   The PATH-SETUP-TYPE TLV is defined in [RFC8408]; [RFC9050] defines a
   PST value for PCECC as '2', which is applicable for multicast tree
   described in this document as well.

3.3.  Multicast Source Registration Object

   The MSR object is optional and SHOULD contain multicast source
   information and FHR information.  The MSR object SHOULD be carried
   within a PCRpt message sent by PCC to PCE for registration.  The MSR
   object SHOULD be carried within a PCUpd message sent by PCE to PCC in
   response to registration.

   MSR Object-Class is TBD3.  MSR Object-Type is 1.  The format of the
   MSR object body is:

        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                           |R|A|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        Auxiliary Length       |            Reserved           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                        Auxiliary Data                         ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                        Optional TLVs                          ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                      Figure 1: MSR Object Body Format

   R (Register flag, 1 bit): The R flag set to 1 indicates that the PCC
   is registering multicast information to the PCE.  The R flag set to 0
   indicates that the PCC revokes the registration.

   A (Authentication flag, 1 bit): The A flag set to 1 indicates success
   of registration.  The A flag set to 0 indicates failure of

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   registration or revocation of registration.  If there is no
   authentication information, A flag SHOULD also be set to 0.

   Auxiliary Length (1 Octet): indicates the length of Auxiliary Data.

   Auxiliary Data (Variable length): contains functional data such as
   authentication information.

   MSR object MAY include Multicast Address TLV, mLDP FEC TLV, P2MP SR
   Policy Association Group Policy Identifiers TLV, and VPN Information
   TLV.  P2MP SR Policy Association Group Policy Identifiers TLV are
   defined in [I-D.ietf-pce-sr-p2mp-policy].  MSR object carries
   different TLVs depending on the multicast tree.

3.3.1.  Multicast Address TLV

   In IP multicast scenarios, Multicast Address TLV SHOULD be included.

   The format of the Multicast Address TLV is:

        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 = TBD4          |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Prefix Length         |            Reserved           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                    Multicast Source Address                   ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                    Multicast Group Address                    ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 2: Multicast Address TLV Format

   Prefix Length (2 Octets): indicates the length of multicast
   addresses. the length MAY be 4 Octets, 8 Octets, 16 Octets, or 32
   Octets.  The multicast source address can be empty, but the multicast
   group address must be filled.  If both the multicast source address
   and multicast group address exist, they must be both IPv4 and IPv6
   addresses.

   Multicast Source Address (Variable length): contains IPv4 or IPv6
   address of the multicast source.

   Multicast Group Address (Variable length): contains IPv4 or IPv6
   address of the multicast group.

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3.3.2.  mLDP FEC TLV

   In mLDP multicast scenarios, Multicast Address TLV SHOULD be
   included.

   The format of the mLDP FEC TLV is:

        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 = TBD5          |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                           mLDP FEC                            ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          Figure 3: mLDP FEC TLV Format

   mLDP FEC (Variable length): carries mLDP FEC.

3.3.3.  VPN Information TLV

   VPN Information TLV is used to report VPN information about multicast
   sources and receivers.  The format of the VPN Information TLV is:

        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 = TBD6          |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         VPN Identifier                        |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 4: VPN Information TLV Format

   VPN Identifier (8 Octets): indicates the VPN which the receiver used.

3.4.  Multicast Receiver Information Object

   The MRI object is optional and SHOULD contain receivers' information
   for matching the multicast registration information.  The MRI object
   SHOULD be carried within a PCRpt message sent by PCC to PCE for
   multicast joining or leaving.

   MRI Object-Class is TBD7.  MRI Object-Type is 1.  The format of the
   MRI object body is:

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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Reserved           |            flags          |B|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                        Optional TLVs                          ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 5: MRI Object Body Format

   B(BIER multicast flag, 1 bit): The B flag set to 1 indicates that
   multicast protocol is BIER.  If the B flag set to 1, MRI object
   SHOULD include BFR information TLV defined in Section 3.4.1.

   S(Subscribe flag, 1 bit): The S flag set to 1 indicates that PCC
   delivers the message requesting to join PCE.  The S flag set to 0
   indicates that PCC delivers the message requesting to leave to PCE.

   MRI object MAY include Multicast Address TLV, mLDP FEC TLV, P2MP SR
   Policy Association Group Policy Identifiers TLV, VPN Information TLV,
   and BFR information TLV.

3.4.1.  BFR Information TLV

   BFR Information TLV is used to report router location information in
   the BIER domain.  The format of the BFR Information TLV is:

        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 = TBD8          |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Subdomain-Id  |            BFR-ID             |  BSL  |Padding|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                     Figure 6: BFR Information TLV Format

   Subdomain-Id (1 Octet): Unique value identifying the BIER subdomain.

   BFR-ID (2 Octets): Identification of BFR in a subdomain.

   BSL (BitString Length, 4 bits): encodes the length in bits of the
   BitString as per [RFC8296], the maximum length of the BitString is 7,
   it indicates the length of BitString is 4096.  It is used to refer to
   the number of bits in the BitString.

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3.5.  CCI Object

   The CCI object [RFC9050] is used by the PCE to specify the forwarding
   instructions to the PCC and MAY be carried within a PCInitiate or
   PCRpt message for control information download/report.

   The CCI Object Type 1 for MPLS Label is defined in [RFC9050], which
   is used for the P2MP LSPs as well.  For mLDP multicast trees, in
   addition to forwarding labels, corresponding tree labels or label
   stacks are required.  Therefore, a new TLV is needed to carry tree
   labels or label stacks.  In addition, in order to meet the needs of
   VPN scenarios, a new TLV with VPN forwarding Identifier is also
   defined.

3.5.1.  Tree Label TLV

   The format of Tree Label TLV is:

        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 = TBD9          |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                        Tree Label stack                       ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    Figure 7: Tree Label TLV Format

   Tree Label stack (Variable length): contains tree labels used to
   identify multicast trees.  There are three application scenarios, as
   per [I-D.ietf-bess-bgp-multicast-controller].

3.5.2.  VPN Forwarding Identifier TLV

   The format of VPN Forwarding Identifier TLV is:

        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 = TBD10         |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                   VPN Forwarding Identifier                   ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                Figure 8: VPN Forwarding Identifier TLV Format

   VPN Forwarding Identifier (Variable length): contains MPLS label or
   IPv6 Segment Identifier with 16 Octets.

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3.6.  Tree Forwarding State Synchronization Object

   The TFSS object is optional and SHOULD contain the forwarding state
   of control plane that the tree node needs to synchronize.  The TFSS
   object SHOULD be carried within a PCInitiate or PCUpd message sent by
   PCE to PCC, or a PCRpt message sent by PCC to PCE for response.

   TFSS Object-Class is TBD11.  TFSS Object-Type is 1.  The format of
   the TFSS object body is:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |            Reserved           |              flags          |F|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                        Optional TLVs                          ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 9: TFSS Object Body Format

   F (Forwarding flag, 1 bit): The F flag set to 1 indicates that the
   node MAY start forwarding multicast packets.  The F flag set to 0
   indicates that the node SHOULD stop forwarding multicast packets.

   TFSS object MAY include Multicast Address TLV, VPN Forwarding
   Identifier TLV, and BIER Attribute TLV.  When TT=1, BIER Attribute
   TLV SHOULD be included.

3.6.1.  BIER Attribute TLV

   BIER Attribute TLV is used to instruct the FHR to forward multicast
   packets to the users according to the BitString specified by the
   controller.  The format of BIER Attribute TLV is:

        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 = TBD12         |             Length            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Subdomain-id  |       SI      |  BSL  ~       BitString       ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                    Figure 10: BIER Attribute TLV Format

   Subdomain-id (1 Octet): Unique value identifying the BIER subdomain.

   SI (Set Identifier, 1 Octet): encoding the Set Identifier used in the
   encapsulation for this BIER subdomain for this BitString length.

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   BSL (BitString Length, 4 bits): encodes the length in bits of the
   BitString as per [RFC8296], the maximum length of the BitString is 7,
   it indicates the length of BitString is 4096.  It is used to refer to
   the number of bits in the BitString.

   BitString(Variable length): indicates the path of multicast data
   packets forwarding for headend.

3.7.  Multicast Receiver Statistics Object

   The MRS object is optional and used to inform PCE of the number of
   receivers.  The MRS object SHOULD be carried within a PCRpt or a
   PCUpd message for synchronize receiver information periodically, or
   PCRpt message for the leaving of receivers.

   MRS Object-Class is TBD13.  MRS Object-Type is 1.  The format of the
   MRS object body is:

       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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          Number Length        |            Reserved           |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Multicast Statistics                     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       ~                        Optional TLVs                          ~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                       Figure 11: MRS Object Body Format

   Number Length (2 Octets): indicates the length of receiver number.

   Multicast Statistics (4 Octets): indicates the statistics information
   for a particular multicast tree of a controller or a LHR.

   MRS object MAY include Multicast Address TLV, mLDP FEC TLV, P2MP SR
   Policy Association Group Policy Identifiers TLV.

4.  Message Formats

4.1.  PCRpt message

   The definition of the PCRpt message from [RFC8231] and [RFC9050] is
   extended to optionally include MSR object, MRI object, TFSS object,
   and MRS object after the path object.  The encoding will become:

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

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

         <state-report> ::= [<SRP>]
                            <LSP>
                            <path>
                            [<MSR>]
                            [<MRI>]
                            [<TFSS>]
                            [<MRS>]

       Where:
         <path> is as per [RFC8231] and the LSP and SRP object are
         also defined in [RFC8231].

4.2.  PCInitiate message

   The definition of the PCInitiate message from [RFC8281] is extended
   to optionally include TFSS object after the path object.  The
   encoding will become:

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

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

       <update-request> ::= <SRP>
                            <LSP>
                            [<TFSS>]

     Where:
       LSP and SRP object are defined in [RFC8231].

4.3.  PCUpd message

   The definition of the PCUpd message from [RFC8231] is extended to
   optionally include MSR object, TFSS object and MRS object after the
   path object.  The encoding will become:

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

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

       <update-request> ::= <SRP>
                            <LSP>
                            <path>
                            [<MSR>]
                            [<TFSS>]
                            [<MRS>]

     Where:
       <path> is as per [RFC8231] and the LSP and SRP object are
       also defined in [RFC8231].

5.  Example Workflow

5.1.  Multicast Tree Discovery

                 +-------+                       +-------+
                 |PCC    |                       |  PCE  |
                 |ingress|                       +-------+
           +-----|       |                           |
           |PCC  +-------+                           |
           |transit| |                               |
    +------|       | |                               |
    |PCC   +-------+ |                               |
    |egress |  |     |                               |
    +-------+  |     |                               |
        |      |     |-----PCRpt,PLSP-ID=1,D=1------>|Source Registration
        |      |     |       MSR Object(R=1)         |(Root Discovery)
        |      |     |                               |
        |      |     |<----PCUpd,PLSP-ID=1-----------|Source Registration
        |      |     |     MSR Object(R=1)           |Confirmation
        |      |     |                               |
        |------------------PCRpt,PLSP-ID=0---------->|Receiver Report
        |      |     |     MRI Object(S=1)           |(Leaf Discovery)
        |      |     |                               |
              Figure 11: Workflow of Multicast Tree Discovery

5.2.  Multicast Tree Path Establishment and Update

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5.2.1.  Labeled Tree

   The workflow of Labeled Tree are as per
   [I-D.ietf-pce-sr-p2mp-policy].

5.2.2.  BIER Tree

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                  +-------+                         +-------+
                  |PCC    |                         |  PCE  |
                  |ingress|                         +-------+
           +------|       |                             |
           |      +-------+                             |
           | transit| |                                 |
    +------|        | |                                 |
    |      +--------+ |                                 |
    |egress  |  |     |                                 |
    +--------+  |     |                                 |
        |<-------------------PCInitiate,PLSP-ID=1-------|Tree State
        |       |     |           TFSS Object           |Setup
        |       |     |     VPN Forwarding Identifier   |
        |       |     |                                 |
        |--------------------PCRpt,PLSP-ID=1----------->|Tree State
        |       |     |                                 |Confirmation
        |       |     |                                 |
        |       |     |<-----PCInitiate,PLSP-ID=1-------|Tree State
        |       |     |      TFSS Object (F=1,TT=1)     |Setup
        |       |     |     VPN Forwarding Identifier   |
        |       |     |                                 |
        |       |     |------PCRpt,PLSP-ID=1----------->|Tree State
        |       |     |                                 |Confirmation
        |       |     |                                 |
        |       |     |                                 |
        |       |     |                                 |
        |--------------------PCRpt,PLSP-ID=0----------->|Receiver Report
        |       |     |      MRI Object(S=1/S=0)        |(Leaf Discovery)
        |       |     |                                 |
        |<-------------------PCInitiate,PLSP-ID=1-------|Tree State
        |       |     |           TFSS Object           |Update
        |       |     |     VPN Forwarding Identifier   |
        |       |     |                                 |
        |--------------------PCRpt,PLSP-ID=1----------->|Tree State
        |       |     |                                 |Confirmation
        |       |     |                                 |
        |       |     |<-----PCUpd,PLSP-ID=1------------|Tree State
        |       |     |      TFSS Object (F=1,TT=1)     |Update
        |       |     |                                 |
        |       |     |------PCRpt,PLSP-ID=1----------->|Tree State
        |       |     |                                 |Confirmation
        |       |     |                                 |
                Figure 12: Workflow of BIER Tree Setup/Update

   In the previous multicast tree discovery process, ingress has
   delegated the PCE to calculate the multicast path.  Therefore, during
   the establishment of the multicast tree, PCE informs the ingress to
   forward multicast data for (S,G)/(*,G) via PCInitiate message

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   carrying TFSS object according to the delegation.  The PLSP-ID is the
   value specified by the ingress.  PCE also sends VPN forwarding
   identifier to ingress and egresses, so that multicast packets can be
   forwarded to specified VPN.

   Ingress then updates the tree state and responds to the PCE.  At this
   point, the BIER tree is formally established and the ingress starts
   forwarding for the multicast according to the BitString specified by
   PCE.

   If the topology of the BIER tree changes, the corresponding egresses
   will send PCRpt messages carring MRI object to PCE to inform PCE of
   their changes.  PCE needs to send VPN forwarding identifier to these
   egresses.

   The PCE updates the BitStrig based on changes of the egresses and
   informs the ingress to update.  State update process is similar to
   state setup process, except for the type of message sent by the PCE.

5.3.  Multicast Statistics Synchronization

                    +-------+                       +-------+
                    |PCC    |                       |  PCE  |
                    |ingress|                       +-------+
              +-----|       |                           |
              |PCC  +-------+                           |
              |transit| |                               |
       +------|       | |                               |
       |PCC   +-------+ |                               |
       |egress |  |     |                               |
       +-------+  |     |                               |
           |      |     |                               |
           |------------------PCRpt,PLSP-ID=0---------->| Statistics
           |      |     |        MRS Object             | Report
           |      |     |case1: Periodic Synchronization|
           |      |     | case2: Change Synchronization |
           |      |     |                               |
           |      |     |                               |
           |      |     |<----PCUpd,PLSP-ID=0-----------| Statistics
           |      |     |       MRS Object              | Feedback
           |      |     |   Periodic Synchronization    |
           |      |     |                               |
         Figure 13: Workflow of Multicast Statistics Synchronization

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6.  Security Considerations

   To be added.

7.  IANA Considerations

7.1.  MULTICAST-STATE-CAPABILITY

   IANA is requested to allocate a new code point within registry
   "STATEFUL-PCE-CAPABILITY TLV Flag Field" under "Path Computation
   Element Protocol (PCEP) Numbers" as follows:

           Value               Description               Reference
       ------------   -----------------------------   ---------------
           TBD1         MULTICAST-STATE-CAPABILITY      This document

7.2.  PCEP-ERROR Object

   IANA is requested to allocate code-points in the "PCEP-ERROR Object
   Error Types and Values" sub-registry for the following new error-type
   and error-value:

        Error-Type             Description               Reference
       ------------   -----------------------------   ---------------
            10              Error-value = TBD2         This document
                        MULTICAST-STATE-CAPABILITY
                                             bit is not set

7.3.  New Objects

   IANA is requested to allocate the following Object-Class Values in
   the "PCEP Objects" sub-registry under the "Path Computation Element
   Protocol (PCEP) Numbers" registry:

    Object-Class Value           Description                 Reference
    ------------------  -------------------------------   ---------------
           TBD3          Multicast Source Registration     This document
           TBD7          Multicast Receiver Information    This document
           TBD11    Tree Forwarding State Synchronization  This document
           TBD13         Multicast Receiver Statistics     This document

   IANA is requested to allocate the following Object-Type Value of CCI
   object in the "PCEP Objects" sub-registry under the "Path Computation
   Element Protocol (PCEP) Numbers" registry:

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7.4.  New TLVs

   IANA is requested to allocate the following TLVs:

           Type                  Description                 Reference
    ------------------  -------------------------------   ---------------
           TBD4            Multicast Source Address        This document
           TBD5                    mLDP FEC                This document
           TBD6                 VPN Information            This document
           TBD8                 BFR Information            This document
           TBD9                   Tree Label               This document
               TBD10         VPN Forwarding Identifier TLV     This document
           TBD12                BIER Attribute             This document

8.  Acknowledgements

   The author thanks ... for their review and comments.

9.  References

9.1.  Normative References

   [I-D.ietf-pce-sr-p2mp-policy]
              Bidgoli, H., Voyer, D., Rajarathinam, S., Hemmati, E.,
              Saad, T., and S. Sivabalan, "PCEP extensions for p2mp sr
              policy", draft-ietf-pce-sr-p2mp-policy-00 (work in
              progress), December 2021.

   [RFC1112]  Deering, S., "Host extensions for IP multicasting", STD 5,
              RFC 1112, DOI 10.17487/RFC1112, August 1989,
              <https://www.rfc-editor.org/info/rfc1112>.

   [RFC2362]  Estrin, D., Farinacci, D., Helmy, A., Thaler, D., Deering,
              S., Handley, M., Jacobson, V., Liu, C., Sharma, P., and L.
              Wei, "Protocol Independent Multicast-Sparse Mode (PIM-SM):
              Protocol Specification", RFC 2362, DOI 10.17487/RFC2362,
              June 1998, <https://www.rfc-editor.org/info/rfc2362>.

   [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>.

   [RFC5015]  Handley, M., Kouvelas, I., Speakman, T., and L. Vicisano,
              "Bidirectional Protocol Independent Multicast (BIDIR-
              PIM)", RFC 5015, DOI 10.17487/RFC5015, October 2007,
              <https://www.rfc-editor.org/info/rfc5015>.

   [RFC6388]  Wijnands, IJ., Ed., Minei, I., Ed., Kompella, K., and B.
              Thomas, "Label Distribution Protocol Extensions for Point-
              to-Multipoint and Multipoint-to-Multipoint Label Switched
              Paths", RFC 6388, DOI 10.17487/RFC6388, November 2011,
              <https://www.rfc-editor.org/info/rfc6388>.

   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
              <https://www.rfc-editor.org/info/rfc6514>.

   [RFC7761]  Fenner, B., Handley, M., Holbrook, H., Kouvelas, I.,
              Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent
              Multicast - Sparse Mode (PIM-SM): Protocol Specification
              (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March
              2016, <https://www.rfc-editor.org/info/rfc7761>.

   [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>.

   [RFC8279]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
              Explicit Replication (BIER)", RFC 8279,
              DOI 10.17487/RFC8279, November 2017,
              <https://www.rfc-editor.org/info/rfc8279>.

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   [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>.

   [RFC8296]  Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
              Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation
              for Bit Index Explicit Replication (BIER) in MPLS and Non-
              MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January
              2018, <https://www.rfc-editor.org/info/rfc8296>.

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

   [RFC9050]  Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "Path
              Computation Element Communication Protocol (PCEP)
              Procedures and Extensions for Using the PCE as a Central
              Controller (PCECC) of LSPs", RFC 9050,
              DOI 10.17487/RFC9050, July 2021,
              <https://www.rfc-editor.org/info/rfc9050>.

9.2.  Informative References

   [I-D.chen-pce-pcep-extension-pce-controller-bier]
              Chen, R., Xu, B., Chen, H., and A. Wang, "PCEP Procedures
              and Protocol Extensions for Using PCE as a Central
              Controller (PCECC) of BIER", draft-chen-pce-pcep-
              extension-pce-controller-bier-03 (work in progress), March
              2022.

   [I-D.dhody-pce-pcep-extension-pce-controller-p2mp]
              Li, Z., Peng, S., Geng, X., and M. S. Negi, "Path
              Computation Element Communication Protocol (PCEP)
              Procedures and Extensions for Using the PCE as a Central
              Controller (PCECC) of point-to-multipoint (P2MP) LSPs",
              draft-dhody-pce-pcep-extension-pce-controller-p2mp-08
              (work in progress), March 2022.

   [I-D.ietf-bess-bgp-multicast-controller]
              Zhang, Z., Raszuk, R., Pacella, D., and A. Gulko,
              "Controller Based BGP Multicast Signaling", draft-ietf-
              bess-bgp-multicast-controller-07 (work in progress), July
              2021.

Li, et al.             Expires September 21, 2022              [Page 25]
Internet-Draft        Multicast Tree Setup via PCEP           March 2022

   [I-D.ietf-pim-sr-p2mp-policy]
              (editor), D. V., Filsfils, C., Parekh, R., Bidgoli, H.,
              and Z. Zhang, "Segment Routing Point-to-Multipoint
              Policy", draft-ietf-pim-sr-p2mp-policy-04 (work in
              progress), March 2022.

   [I-D.ietf-spring-sr-replication-segment]
              (editor), D. V., Filsfils, C., Parekh, R., Bidgoli, H.,
              and Z. Zhang, "SR Replication Segment for Multi-point
              Service Delivery", draft-ietf-spring-sr-replication-
              segment-07 (work in progress), March 2022.

   [I-D.zzhang-mvpn-evpn-controller]
              Zhang, Z., Parekh, R., Zhang, Z., and H. Bidgoli, "MVPN
              and EVPN BUM Signaling with Controllers", draft-zzhang-
              mvpn-evpn-controller-01 (work in progress), October 2021.

Authors' Addresses

   Huanan Li
   China Telecom

   Email: lihn6@foxmail.com

   Aijun Wang
   China Telecom

   Email: wangaj3@chinatelecom.cn

   Zhaohui Zhang
   Juniper Networks

   Email: zzhang@juniper.net

   Huaimo Chen
   Futurewei

   Email: Huaimo.chen@futurewei.com

   Ran Chen
   ZTE Corporation

   Email: chen.ran@zte.com.cn

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