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PCE based BIER Procedures and Protocol Extensions
draft-li-pce-based-bier-02

Document Type Replaced Internet-Draft (individual)
Authors Huanan Li , Aijun Wang , Huaimo Chen , Ran Chen
Last updated 2021-10-18 (Latest revision 2021-07-11)
Replaces draft-li-pce-pcep-extension-multicast-management
Replaced by draft-li-pce-multicast
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draft-li-pce-based-bier-02
PCE Working Group                                                  H. Li
Internet-Draft                                                   A. Wang
Intended status: Standards Track                           China Telecom
Expires: April 22, 2022                                          H. Chen
                                                               Futurewei
                                                                 R. Chen
                                                         ZTE Corporation
                                                        October 19, 2021

           PCE based BIER Procedures and Protocol Extensions
                       draft-li-pce-based-bier-02

Abstract

   This document describes extensions to Path Computation Element (PCE)
   communication Protocol (PCEP) for supporting the PCE based Bit Index
   Explicit Replication (BIER) deployment.

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 April 22, 2022.

Copyright Notice

   Copyright (c) 2021 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
   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

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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Overview of PCE based BIER solution . . . . . . . . . . . . .   4
     4.1.  Example of PCE based BIER Topology  . . . . . . . . . . .   4
     4.2.  Basic Procedures  . . . . . . . . . . . . . . . . . . . .   5
   5.  Capability Advertisement  . . . . . . . . . . . . . . . . . .   5
   6.  PCEP message  . . . . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  PCRpt message . . . . . . . . . . . . . . . . . . . . . .   6
     6.2.  PCUpd message . . . . . . . . . . . . . . . . . . . . . .   7
   7.  Object formats  . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Multicast Source Registration Object  . . . . . . . . . .   8
       7.1.1.  Multicast Source Address TLV  . . . . . . . . . . . .   9
       7.1.2.  BIER Information TLV  . . . . . . . . . . . . . . . .  10
       7.1.3.  VPN Information TLV . . . . . . . . . . . . . . . . .  10
     7.2.  Multicast Receiver Information Object . . . . . . . . . .  11
       7.2.1.  Multicast Group Address TLV . . . . . . . . . . . . .  12
     7.3.  Forwarding Indication Object  . . . . . . . . . . . . . .  12
     7.4.  Multicast Receiver Status Object  . . . . . . . . . . . .  13
   8.  Procedures  . . . . . . . . . . . . . . . . . . . . . . . . .  14
     8.1.  Multicast source registration and revocation  . . . . . .  14
     8.2.  Joining and leaving of multicast receivers  . . . . . . .  15
     8.3.  BitString management  . . . . . . . . . . . . . . . . . .  15
     8.4.  Receiver information synchronization  . . . . . . . . . .  15
   9.  Deployment Considerations . . . . . . . . . . . . . . . . . .  16
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  16
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     11.1.  BIER-MULTICAST-CAPABILITY  . . . . . . . . . . . . . . .  16
     11.2.  PCEP-ERROR Object  . . . . . . . . . . . . . . . . . . .  16
     11.3.  New Objects  . . . . . . . . . . . . . . . . . . . . . .  16
     11.4.  New TLVs . . . . . . . . . . . . . . . . . . . . . . . .  16
   12. Contributor . . . . . . . . . . . . . . . . . . . . . . . . .  17
   13. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  17
   14. Normative References  . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   [RFC8279] defines a Bit Index Explicit Replication (BIER)
   architecture where all intended multicast receivers are encoded as a
   bitmask in the multicast packet header within different
   encapsulations such as described in [RFC8296] . A router that
   receives such a packet will forward the packet based on the bit

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   position in the packet header towards the receiver(s) following a
   precomputed tree for each of the bits in the packet.  Each receiver
   is represented by a unique bit in the bitmask.

   Currently, multicast management information is mainly signaled by PIM
   [RFC2362] or BGP [RFC6514], which have some limitations in the
   deployment and process.

   [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.

   This document specifies PCEP protocol extensions to optimize the
   implementation of multicast source registration or revocation,
   receiver automatic discovery, and forwarding control of multicast
   data by using PCEP messages to transmit multicast management
   signaling, combining with the forwarding characteristics of BIER.

2.  Conventions used in this document

   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.

3.  Terminology

   The following terms are used in this document:

   o  BFR-id: BFR Identifier.  It is a number in the range [1,65535]

   o  BGP: Border Gateway Protocol

   o  BIER: Bit Index Explicit Replication

   o  BIFT: Bit Index Forwarding Table

   o  FI: Forwarding indication

   o  IGMP: Internet Group Management Protocol

   o  IGP: Interior Gateway Protocols

   o  MLD: Multicast Listener Discover

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   o  MRI: Multicast Receiver Information

   o  MSR: Multicast Source Registration

   o  PCC: Path Computation Client

   o  PCE: Path Computation Element

   o  PCEP: PCE communication Protocol

   o  PIM: Protocol Independent Multicast

4.  Overview of PCE based BIER solution

   PCE based BIER includes multicast source registration information
   management, multicast receiver information management and multicast
   data forwarding control.

   Multicast source registration information includes registration and
   processing of multicast source information.

   Multicast receiver information includes requesting multicast group,
   multicast source and BitPosition information of receiver-side PCC.

   Multicast data forwarding control includes BitString processing and
   data forwarding.

   PCRpt message and PCUpd message, described in [RFC8231], are used in
   the PCE based BIER processing.

   This document specifies PCEP protocol extensions for multicast group
   management, including Multicast Source Registration (MSR) object,
   Multicast Receiver Information (MRI) object, Forwarding Indication
   (FI) object and Multicast Receiver Status(MRS) object.

4.1.  Example of PCE based BIER Topology

   An example of PCE based BIER topology for a BIER domain with a
   controller as PCE is shown in Figure 1.  In this domain, node R1 and
   R7 are Bit-Forwarding Ingress Router (BFIR) and Bit-Forwarding Egress
   Router (BFER), respectively.

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                           +------------------+
                           +    Controller    +
               +-----------+       PCE        +---------+
               |           +--------^---------+         |
               |                                        |
               |                                        |
             S1|S2/S5          +--------+               |S4
               |    -----------+   R3   +-----------    |
               |   /           +--------+           \   |
               |  /                                  \  |
 +------+    +--+ S6       +--+          +--+        +--+ S3  +--------+
 |Source|----|R1+----------+R5+----------+R6+--------+R7|-----|Receiver|
 +------+    +--+          +--+          +--+        +--+     +--------+
               |                                        |
               |           +--+          +--+           |
               +-----------+R2+----------+R4+-----------+
                           +--+          +--+
     Figure 1: Example of PCE based BIER Topology(controller as PCE)

4.2.  Basic Procedures

   Step 1(S1): R1 sends multicast source information and authentication
   information to the controller about multicast information
   registration via PCRpt message.

   Step 2(S2): The controller sends PCUpd message to R1, carrying
   authentication result.

   Step 3(S3): Receivers send IGMP or MLD messages to R7 requesting to
   join or leave a multicast group.

   Step 4(S4): R7 converts the IGMP or MLD messages into PCRpt message
   and sends it to the controller.

   Step 5(S5): If the multicast group and multicast source information
   requested by the receiver has registered, the controller will send
   PCUpd message to R1 to start or stop forwarding, carrying BitString.

   Step 6(S6): If R1 is ready to start forwarding, it will encapsulate
   BIER header and forward them based on BIFT and BitString when
   receiving multicast packets.

5.  Capability Advertisement

   During the PCEP initialization phase, PCEP speakers advertise
   stateful capability via the STATEFUL-PCE-CAPABILITY TLV in the OPEN

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   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:

   B (BIER-MULTICAST-CAPABILITY, 1 bit): If set to 1 by a PCEP speaker,
   it indicates that the PCEP speaker supports the capability of these
   new flag as specified in this document.

   If a PCEP speaker receivers PECP message with the newly defined
   object, but without the B 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(BIER-MULTICAST-CAPABILITY bit is not
      set).

   o  Terminate the PCEP session.

6.  PCEP message

6.1.  PCRpt message

   MSR objectSection 7.1 should be included in the PCRpt message when
   PCC registers multicast source information with PCE.

   MRI objectSection 7.2 should be included in the PCRpt message when
   PCC sends multcast join messages to PCE.

   MRS objectSection 7.4 should be included in the PCRpt message when
   PCC inform PCE of the number of receivers.

   The definition of the PCRpt message from [RFC8231] is extended to
   optionally include MSR object, MRI object and MRS object after the
   path object.  The encoding from [RFC8231] 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>]
                            [<MRS>]

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

6.2.  PCUpd message

   MSR objectSection 7.1 should be included in the PCUpd message when
   PCE responds to the registration request.

   FI objectSection 7.3 should be included in the PCUpd message when PCE
   sends the BitString to PCC to indicate the path of multicast data
   packets forwarding for PCC.

   MRS objectSection 7.4 should be included in the PCUpd message when
   PCE inform PCC of the number of receivers.

   The definition of the PCUpd message from [RFC8231] is extended to
   optionally include MSR object, FI object and MRS object after the
   path object.  The encoding from [RFC8231] 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>]
                            [<FI>]
                            [<MRS>]

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

7.  Object formats

7.1.  Multicast Source Registration Object

   The MSR object is optional and specifies multicast source information
   in multicast registration information management.  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                         |B|R|A|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Auxliary Length        |            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        Auxiliary Data                         ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        Optional TLVs                          ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                  Figure 2: MSR Object Body Format

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   B(BIER multicast flag, 1 bit): The R flag set to 1 indicates that
   multicast protocol is BIER.  The R flag set to 0 indicates that
   multicast protocol is not BIER.

   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 register.

   A (Authentication flag, 1 bit): The A flag set to 1 indicates success
   of registration.  The A flag set to 0 indicates failure of
   registration or cancellation of registration.  R and A cannot both be
   set to 0 or 1 in PCRpt message.

   Auxiliary Length(8 bits): indicates the length of Auxiliary Data.

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

   MSR object could include three types of TLVs, namely Multicast Source
   Address TLV, BIER Information TLV, VPN Information TLV, as defined
   follows:

7.1.1.  Multicast Source Address TLV

   The format of the Multicast Source 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                   ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
            Figure 3: Multicast Source Address TLV Format

   Type(16 bits): TBD4 is to be assigned by IANA.

   Length: Variable.

   Prefix Length(16 bits): indicates the length of multicast source
   address.

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

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7.1.2.  BIER Information TLV

   BIER Information TLV is used to report router location information in
   the BIER domain.  When the multicast flag in MSR, MRI, FI objects is
   set, BIER Information TLV should be included.  The format of the BIER
   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 = TBD5          |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Subdomain-id  |            BFR-ID             |  BSL  |  Res  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 4: BIER Information TLV Format

   Type(16 bits): TBD5 is to be assigned by IANA.

   Length: Variable.

   Subdomain-id(8 bits): Unique value identifying the BIER subdomain.

   BFR-ID (16 bits): 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.

7.1.3.  VPN Information TLV

   VPN Information TLV is used to report VPN information about multicast
   sources and receivers.  When the multicast flag in MSR, MRI, FI
   objects is set, VPN Information TLV should be included.  The format
   of the VPN Information TLV 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Type = TBD6          |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               RD                              |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          Label Length         |            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        Forwarding Label                       ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
               Figure 5: VPN Information TLV Format

   Type(16 bits): TBD6 is to be assigned by IANA.

   Length: Variable.

   RD(Route Distinguisher, 8 bytes): indicates the VPN which the
   receiver used.

   Label Length(16 bits): indicates the length of forwarding label Data,
   the length should be 0 ,32 bits or 128 bits.

   Forwarding Label(Variable Length): contains MPLS label with 32 bit or
   IPv6 Segment Identifier with 128 bits.

7.2.  Multicast Receiver Information Object

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

   MRI Object-Class is TBD7.  MRI Object-Type is 1.

   The format of the MRI 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          |B|S|            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        Optional TLVs                          ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                  Figure 6: MRI Object Body Format

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   B(BIER multicast flag, 1 bit): The R flag set to 1 indicates that
   multicast protocol is BIER.  The R flag set to 0 indicates that
   multicast protocol is not BIER.

   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 could include four types of TLVs, namely Multicast Source
   Address TLVSection 7.1.1, BIER INFO TLVSection 7.1.2, VPN Information
   TLVSection 7.1.3 and Multicast Group Address TLV.  Multicast Group
   Address TLV is defined as follows:

7.2.1.  Multicast Group Address TLV

   The format of the Multicast Group 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 = TBD8          |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |         Prefix Length         |            Reserved           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                    Multicast Group Address                    ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           Figure 7: Multicast Group Address TLV Format

   Type(16 bits): TBD8 is to be assigned by IANA.

   Length: Variable.

   Prefix Length(16 bits): indicates the length of multicast group
   address.

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

7.3.  Forwarding Indication Object

   The FI object is optional and used to indicate to the headend how to
   forward multicast data packets in the form of BitString.  The FI
   object should be carried within a PCUpd message sent by PCE to PCC in
   multicast scenarios.

   FI Object-Class is TBD9.  FI Object-Type is 1.

   The format of the FI 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  Subdomain-id |       SI      |  BSL  |       Reserved    |B|F|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   BitString (first 32 bits)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                               .                               |
   |                               .                               |
   |                               .                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   BitString  (last 32 bits)                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        Optional TLVs                          ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   Figure 8: FI Object Body Format

   Subdomain-id(8 bits): Unique value identifying the BIER subdomain.

   SI (Set Identifier, 8 bits): encoding the Set Identifier used in the
   encapsulation for this BIER subdomain for this BitString length..

   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.

   B(BIER multicast flag, 1 bit): The R flag set to 1 indicates that
   multicast protocol is BIER.  The R flag set to 0 indicates that
   multicast protocol is not BIER.

   F(Forwarding flag, 1 bit): The F flag set to 1 indicates that the
   router may start forwarding multicast packets.  The F flag set to 0
   indicates that the router should stop forwarding multicast packets.

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

   FI object should include three types of TLVs, namely Multicast Source
   Address TLVSection 7.1.1, VPN Information TLVSection 7.1.3 and
   Multicast Group Address TLVSection 7.2.1.

7.4.  Multicast Receiver Status 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.

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   MRS Object-Class is TBD10.  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           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Number of Receivers                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        Optional TLVs                          ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                 Figure 9: MRS Object Body Format

   Number Length(16 bits): indicates the length of receiver number.

   Number of Receivers(32 bits): indicates the number of receivers for a
   particular (S,G) tuple.

   MRS object should include two types of TLVs, namely Multicast Source
   Address TLVSection 7.1.1 and Multicast Group Address
   TLVSection 7.2.1.

8.  Procedures

8.1.  Multicast source registration and revocation

   For PCC-Registered multicast source, an ingress node sends a PCRpt
   message with MSR object to a stateful PCE, where R flag is set and A
   flag is not set.  The registered authentication information can be
   passed through auxiliary data in MSR object.

   Upon receiving the registration via PCRpt message, the stateful PCE
   MUST match local authentication rules based on the multicast
   information and auxiliary data in PCRpt message.  If authenticated
   successfully, the PCE stores the multicast registration information
   into the database.  In response, PCE MUST send a PCUpd message with
   MSR object to ingress node, where R flag is set.  A flag is set only
   if authentication is successful.

   For PCC-revoked multicast source registration, an ingress node sends
   a PCRpt message with MSR object to a stateful PCE, where R flag is
   not set and A flag is set.

   Upon receiving the revocation via PCRpt message, in response, PCE
   MUST send a PCUpd message with MSR object to ingress node, where
   neither R nor A is set.

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8.2.  Joining and leaving of multicast receivers

   When an egress node receives an IGMP or MLD message from a multicast
   receiver to join, the egress node should send a PCRpt message with
   MRI object to the PCE if no other receiver has sent the same request
   to it before.

   If it is not the first time the PCE has received the same PCRpt
   message for join from the same egress node, this message should be
   ignored.

   When an egress node receives an IGMP or MLD message from a multicast
   receiver to leave, the egress node should send a PCRpt message with
   MRI object and MRS object to the PCE if there are no other members in
   the requested multicast group.  In MRS object, the number of
   receivers is zero.

8.3.  BitString management

   Upon receiving the join or leave request via PCRpt message, PCE needs
   to combine the BFR-id and SI of the egress node carried in PCRpt
   message with the BFR-id and SI of the ingress node and existed
   BitStrings in the database to create or update BitString.  If there
   are members in the multicast group, the PCE should send a PCUpd
   message with FI object carrying the latest BitString to the ingress
   node, where F flag is set.

   When receving multicast packets, the ingress node encapsulates BIER
   header and forwards them based on BIFT and BitString.  Encapsulation
   of Forwarding Label is not in the scope of this document.

   If there is no member in the multicast group, the PCE should send a
   PCUpd message with FI object to the ingress node, where F flag is not
   set.

8.4.  Receiver information synchronization

   Upon receiving multicast packets from a particular multicast group,
   egress node will synchronize the number of receivers in this
   multicast group with the PCE via PCRpt message with MRS object
   periodically.

   After sending a PCUpd message with FI object to an ingress node for a
   particular multicast group, the PCE will synchronize the total number
   of receivers in this multicast group with the ingress node via PCUpd
   message with MRS object periodically.

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   If there is no member in the multicast group, the synchronization of
   receiver number information ends.

9.  Deployment Considerations

10.  Security Considerations

11.  IANA Considerations

11.1.  BIER-MULTICAST-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         BIER-MULTICAST-CAPABILITY      This document

11.2.  PCEP-ERROR Object

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

    Error-Type               Description               Reference
   ------------   -----------------------------   ---------------
        10               Error-value = TBD2        This document
                          B bit is not set

11.3.  New Objects

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

Object-Class Value              Description                  Reference
-------------------    ------------------------------    ---------------
       TBD3            Multicast Receiver Information     This document
       TBD7            Multicast Receiver Information     This document
       TBD9                 Forwarding Indication         This document
       TBD10               Multicast Receiver Status       This document

11.4.  New TLVs

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

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       Type                    Description                  Reference
-------------------    ------------------------------    ---------------
       TBD4              Multicast Source Address         This document
       TBD5              Multicast Group Address          This document
       TBD6               BIER Information TLV            This document
       TBD8                  VPN Information              This document

12.  Contributor

13.  Acknowledgement

14.  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>.

   [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>.

   [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>.

   [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>.

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   [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>.

   [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>.

Authors' Addresses

   Huanan Li
   China Telecom
   Beiqijia Town, Changping District
   Beijing, Beijing  102209
   China

   Email: lihn6@foxmail.com

   Aijun Wang
   China Telecom
   Beiqijia Town, Changping District
   Beijing, Beijing  102209
   China

   Email: wangaj3@chinatelecom.cn

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   Huaimo Chen
   Futurewei
   Boston
   USA

   Email: Huaimo.chen@futurewei.com

   Ran Chen
   ZTE Corporation
   50 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   Email: chen.ran@zte.com.cn

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