PCE Working Group H. Li Internet-Draft A. Wang Intended status: Standards Track China Telecom Expires: January 13, 2022 H. Chen Futurewei R. Chen ZTE Corporation July 12, 2021 PCE based BIER Procedures and Protocol Extensions draft-li-pce-based-bier-01 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 January 13, 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 Li, et al. Expires January 13, 2022 [Page 1] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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 Advertisemnt . . . . . . . . . . . . . . . . . . . 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 7.2. Multicast Receiver Information Object . . . . . . . . . . 10 7.3. Forwarding Indication Object . . . . . . . . . . . . . . 11 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 . . . . . . . 14 8.3. BitString management . . . . . . . . . . . . . . . . . . 15 8.4. Receiver information synchronization . . . . . . . . . . 15 9. Deployment Considerations . . . . . . . . . . . . . . . . . . 15 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 11.1. BIER-MULTICAST-CAPABILITY . . . . . . . . . . . . . . . 16 11.2. PCEP-ERROR Object . . . . . . . . . . . . . . . . . . . 16 11.3. New Objects . . . . . . . . . . . . . . . . . . . . . . 16 12. Contributor . . . . . . . . . . . . . . . . . . . . . . . . . 16 13. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 16 14. Normative References . . . . . . . . . . . . . . . . . . . . 16 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 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. Li, et al. Expires January 13, 2022 [Page 2] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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 spceifies 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 o MRI: Multicast Receiver Information o MSR: Multicast Source Registration Li, et al. Expires January 13, 2022 [Page 3] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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. Li, et al. Expires January 13, 2022 [Page 4] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 +------------------+ + 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 receving multicast packets. 5. Capability Advertisemnt During the PCEP initialization phase, PCEP speakers advertise stateful capability via the STATEFUL-PCE-CAPABILITY TLV in the OPEN Li, et al. Expires January 13, 2022 [Page 5] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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: Li, et al. Expires January 13, 2022 [Page 6] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 ::= Where: ::= [] ::= [] [] [] [] Where: 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: Li, et al. Expires January 13, 2022 [Page 7] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 ::= Where: ::= [] ::= [] [] [] Where: 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 Objcet should be carried within a PCRpt message sent by PCC to PCE for registration. The MSR Objcet 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 objcet body is: Li, et al. Expires January 13, 2022 [Page 8] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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 | BFR-ID | BSL | |R|A| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RD | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address Type |Auxliary Length| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Multicast Source Address ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Auxliary Data ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: MSR Object Body Format 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. 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. RD(Route Distinguisher, 8 bytes): indicates the VPN which the receiver used. Address Type(8 bits): indicates the type of the source address. Address Type = 1: IPv4 address. Address Type = 2: IPv6 address. Auxliary Length(8 bits): indicates the length of Auxliary Data. Multicast Source Address(Variable length): contains IPv4 or IPv6 address of the multicast source requested. Li, et al. Expires January 13, 2022 [Page 9] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 Auxliary Data(Variable length): contains functional data such as authentication information. Reserved: This field MUST be set to zero on transmission and MUST be ignored on receipt. 7.2. Multicast Receiver Information Object The MRI object is optional and specifies receivers' information for matching the multicast registration information. The MRI Objcet should be carried within a PCRpt message sent by PCC to PCE in muticast joining or leaving. MRI Object-Class is TBD4. MRI Object-Type is 1. The format of the MRI objcet 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Subdomain-id | BFR-ID | BSL | |S| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RD | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address Type | Label Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Multicast Source Address ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Multicast Group Address ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Forwarding Label ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: MRI Object Body Format 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. 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. Li, et al. Expires January 13, 2022 [Page 10] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 RD(Route Distinguisher, 8 bytes): indicates the VPN which the receiver used. Address Type(8 bits): indicates the type of the source and group addresses. Address Type = 1: IPv4 address. Address Type = 2: IPv6 address. Label Length(8 bits): indicates the length of Label. Multicast Source Address(Variable length): contains IPv4 or IPv6 address of the multicast source requested. Multicast Group Address(Variable length): contains IPv4 or IPv6 address of the multicast group requested. Forwarding Label(Variable Length): contains MPLS label with 32 bit or IPv6 Segment Identifier with 128 bit. Reserved: This field MUST be set to zero on transmission and MUST be ignored on receipt. 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 Objcet should be carried within a PCUpd message sent by PCE to PCC in muticast scenarios. FI Object-Class is TBD5. FI Object-Type is 1. The format of the FI objcet body is: Li, et al. Expires January 13, 2022 [Page 11] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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 |F| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RD | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address Type | Label Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Multicast Source Address ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Multicast Group Address ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Forwarding Label ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (first 32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | . | | . | | . | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitString (last 32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: 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. 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. RD(Route Distinguisher, 8 bytes): indicates the VPN which the receiver used. Address Type(8 bits): indicates the type of the source and group addresses. Address Type = 1: IPv4 address. Address Type = 2: IPv6 address. Label Length(8 bits): indicates the length of Label. Li, et al. Expires January 13, 2022 [Page 12] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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. Forwarding Label(Variable Length): contains MPLS label with 32 bit or IPv6 Segment Identifier with 128 bit. BitString(Variable length): indicates the path of multicast data packets forwarding for headend. Reserved: This field MUST be set to zero on transmission and MUST be ignored on receipt. 7.4. Multicast Receiver Status Object The MRS object is optional and used to inform PCE of the number of receivers. The MRS Objcet 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 TBD6. MRS Object-Type is 1. The format of the MRS objcet 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Subdomain-id | SI | BSL | Address Type | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Number of Receivers | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Multicast Source Address ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Multicast Group Address ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: MRS 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. Li, et al. Expires January 13, 2022 [Page 13] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 Address Type(8 bits): indicates the type of the source and group addresses. Address Type = 1: IPv4 address. Address Type = 2: IPv6 address. Number of Receivers(32 bits): indicates the number of receivers for a particular (S,G) tuple. 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. 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 auxliary 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 auxliary 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. 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. Li, et al. Expires January 13, 2022 [Page 14] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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 carring 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. 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 Li, et al. Expires January 13, 2022 [Page 15] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 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 TBD4 Multicast Receiver Information This document TBD5 Forwarding Indication This document TBD6 Multicast Receiver Status 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, . Li, et al. Expires January 13, 2022 [Page 16] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 [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, . [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, August 2006, . [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, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [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, . [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, . [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, . [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, . Li, et al. Expires January 13, 2022 [Page 17] Internet-DraPCE based BIER Procedures and Protocol Extensions July 2021 [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, . 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 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 Li, et al. Expires January 13, 2022 [Page 18]