PCE R. Chen Internet-Draft B. Xu Intended status: Standards Track ch. Zhu Expires: 9 January 2025 ZTE Corporation H. Chen Futurewei A. Wang China Telecom 8 July 2024 PCEP Procedures and Protocol Extensions for Using PCE as a Central Controller (PCECC) of BIER-TE draft-chen-pce-controller-bier-te-06 Abstract This draft specify extensions to PCEP protocol when a PCE-based controller is responsible for allocates the BIER-TE information(BIER subdomain-id, adjacencies BitPosition(s), and Adjacency Types etc), then PCC generate a "Bit Index Forwarding Table"(BIFT). 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 9 January 2025. Copyright Notice Copyright (c) 2024 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 Chen, et al. Expires 9 January 2025 [Page 1] Internet-Draft PCECC BIER-TE July 2024 and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. PCECC BIER Requirements . . . . . . . . . . . . . . . . . . . 3 3. Procedures for Using the PCE as the Central Controller (PCECC) in BIER-TE . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. PCECC Capability Advertisement . . . . . . . . . . . . . 4 3.2. New BIER Path Setup . . . . . . . . . . . . . . . . . . . 4 3.3. PCECC BIER-TE information allocation and Generation of BFIT . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.4. Redundant PCEs . . . . . . . . . . . . . . . . . . . . . 5 3.5. Re Delegation and Cleanup . . . . . . . . . . . . . . . . 5 3.6. Synchronization of BIER-TE information Allocations . . . 5 4. PCEP extension . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 5 4.1.1. PCECC Capability sub-TLV . . . . . . . . . . . . . . 5 4.2. PATH-SETUP-TYPE TLV . . . . . . . . . . . . . . . . . . . 6 4.3. CCI object . . . . . . . . . . . . . . . . . . . . . . . 6 4.3.1. BIER Encapsulation Sub TLV . . . . . . . . . . . . . 7 4.3.2. Address TLVs . . . . . . . . . . . . . . . . . . . . 7 4.3.3. ROUTE-DISTINGUISHER TLV . . . . . . . . . . . . . . . 7 4.4. FEC Object . . . . . . . . . . . . . . . . . . . . . . . 8 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 8. Normative References . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction [RFC8283]introduces the architecture for PCE as a central controller as an extension of the architecture described in[RFC4655] and assumes the continued use of PCEP as the protocol used between PCE and PCC. [RFC8283]further examines the motivations and applicability for PCEP as a Southbound Interface (SBI), and introduces the implications for the protocol. [RFC9050]specify the procedures and PCEP protocol extensions for using the PCE as the central controller for static LSPs, where LSPs can be provisioned as explicit label instructions at each hop on the end-to-end path. Each router along the path must be told what label- forwarding instructions to program and what resources to reserve. Chen, et al. Expires 9 January 2025 [Page 2] Internet-Draft PCECC BIER-TE July 2024 The PCE-based controller keeps a view of the network and determines the paths of the end-to-end LSPs, and the controller uses PCEP to communicate with each router along the path of the end-to-end LSP. Tree Engineering for Bit Index Explicit Replication" (BIER-TE) shares architecture and packet formats with BIER as described in [RFC8279]. BIER-TE forwards and replicates packets based on a BitString in the packet header, but every BitPosition of the BitString of a BIER-TE packet indicates one or more adjacencies as described in [RFC9262]. This draft specify extensions to PCEP protocol when a PCE-based controller is responsible for allocates the BIER-TE information(BIER subdomain-id, adjacencies BitPosition(s), and Adjacency Types etc), then PCC generate a "Bit Index Forwarding Table"(BIFT). 1.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. PCECC BIER Requirements Following key requirements for PCECC-BIER should be considered when`designing the PCECC based solution: * PCEP speaker supporting this draft needs to have the capability to advertise its PCECC BIER-TE capability to its peers. * PCEP speaker not supporting this draft needs to be able to reject PCECC BIER-TE related message with a reason code that indicates no support for PCECC. * PCEP procedures needs to provide a means to update (or cleanup) the BIER-TE related informations (BIER subdomain-id, adjacencies BitPosition(s), and Adjacency Types etc) to the PCC. * PCEP procedures needs to provide a means to update (or cleanup) the BIER-TE "Bit Index Forwarding Table" (BIFT) to the PCC. * PCEP procedures needs to provide a means to synchronize the BIER- TE related informations(BIER subdomain-id, adjacencies BitPosition(s), and Adjacency Types etc) between PCE to PCC in the PCEP messages. Chen, et al. Expires 9 January 2025 [Page 3] Internet-Draft PCECC BIER-TE July 2024 3. Procedures for Using the PCE as the Central Controller (PCECC) in BIER-TE Active stateful PCE is described in [RFC8231]. PCE as a central controller (PCECC) reuses existing Active stateful PCE mechanism as much as possible to control the LSP. This document uses the same PCEP messages and its extensions which are described in [RFC9050] for PCECC BIER-TE as well. PCEP messages PCRpt, PCInitiate, PCUpd are also used to send LSP Reports, LSP setup and LSP update respectively. The extended PCInitiate message described in [RFC9050] is used to download or cleanup central controller's instructions (CCIs) (BIER-TE related informations and "Bit Index Forwarding Table" (BIFT) in scope of this document). The extended PCRpt message described in [RFC9050] is also used to report the CCIs (BIER-TE related informations) from PCC to PCE. [RFC9050] specify an object called CCI for the encoding of central controller's instructions. This document extends the CCI by defining another object-type for BIER-TE. 3.1. PCECC Capability Advertisement During PCEP Initialization Phase, PCEP Speakers (PCE or PCC) advertise their support of PCECC extensions. A PCEP Speaker includes the "PCECC Capability" sub-TLV, described in [RFC9050]. This document adds T-bit in PCECC-CAPABILITY sub-TLV for BIER-TE. 3.2. New BIER Path Setup The PCEP messages pertaining to PCECC BIER-TE MUST include PATH- SETUP-TYPE TLV [RFC8408] with PST=TBD in the SRP object to clearly identify the PCECC BIER-TE is intended. 3.3. PCECC BIER-TE information allocation and Generation of BFIT Each node (PCC) is allocated a node BIER-TE information by the PCECC. The BIER-TE information mainly includes BIER subdomain-id, adjacencies BitPosition(s), and Adjacency Types etc. In scenarios where the IGP protocol is not used/available, Each node (PCC) is allocated its own and neighbor BIER-TE informations by the PCECC, then PCC generates a BIFT based on the informations it receives. The BIFT mainly includes BFR ID, F-BM and BFR nexthop. Chen, et al. Expires 9 January 2025 [Page 4] Internet-Draft PCECC BIER-TE July 2024 3.4. Redundant PCEs [I-D.ietf-pce-state-sync] describes synchronization mechanism between the stateful PCEs. The BIER-TE informations allocated by a PCE MUST also be synchronized among PCEs for PCECC BIER-TE state synchronization. 3.5. Re Delegation and Cleanup [RFC9050] describes the action needed for CCIs for the Basic PCECC LSP on this terminated session.Similarly actions should be applied for the BIER-TE information as well. 3.6. Synchronization of BIER-TE information Allocations [RFC9050] describes the synchronization of Central Controller's Instructions (CCI) via LSP state synchronization as described in [RFC8231] and [RFC8232].Same procedures should be applied for BIER-TE information and "Bit Index Forwarding Table" (BIFT) allocations as well. 4. PCEP extension 4.1. The OPEN Object 4.1.1. PCECC Capability sub-TLV [RFC9050] defined the PCECC-CAPABILITY TLV. A new T-bit is defined in PCECC-CAPABILITY sub-TLV for PCECC BIER-TE: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=TBD | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags |T|I|S| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: T (PCECC BIER-TE CAPABILITY - 1 bit): If set to 1 by a PCEP speaker, it indicates that the PCEP speaker is capable for PCECC BIER-TE capability and PCE would allocate BIER-TE information on this session. Chen, et al. Expires 9 January 2025 [Page 5] Internet-Draft PCECC BIER-TE July 2024 4.2. PATH-SETUP-TYPE TLV The PATH-SETUP-TYPE TLV is defined in [RFC8408]. PST = TBD is used when Path is setup via PCECC BIER-TE mode.On a PCRpt/PCUpd/PCInitiate message, the PST=TBD indicates that this path was setup via a PCECC BIER-TE based mechanism where either the BIER-TE informations and BIER-TE "Bit Index Forwarding Table" (BIFT) were allocated/instructed by PCE via PCECC mechanism. 4.3. CCI object The Central Control Instructions (CCI) Object is used by the PCE to specify the forwarding instructions is defined in [RFC9050]. This document defines another object-type for BIER-TE purpose. CCI Object-Type is TBD for BIER-TE as below 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CC-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | subdomain-ID | BSL | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SI |adj-t| BitPosition | Reserved| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLV // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: The field CC-ID is as described in [RFC9050]. BIER subdomain-ID: Unique value identifying the BIER subdomain. (as defined in [RFC8401]. BSL: A 1 octet field encodes the length in bits of the BitString as per [RFC8296], the maximum length of the BitString is 5,it indicates the length of BitString is 1024.It is used to refer to the number of bits in the BitString. SI: Set Identifier (Section 1 of [RFC8279] used in the encapsulation for this BIER subdomain for this BitString length, 1 octet. BitPositions: BitPositions indicate adjacencies,16bit. Chen, et al. Expires 9 January 2025 [Page 6] Internet-Draft PCECC BIER-TE July 2024 The "Reserved" (1 octets) fields are currently unused, and MUST be set to zero on transmission and ignored on reception. Adjacency Types:There are three types in this document. * 0b000:Forward Connected. * 0b001:Forward Routed. * 0b010: Local Decap. * ECMP will discuss in next version. Optional TLV: There are three optional TLV are defined/reused in this draft. 4.3.1. BIER Encapsulation Sub TLV BIER Encapsulation Sub-TLV defined in [I-D.chen-pce-pcep-extension-pce-controller-bier] are used to associate BIER Encapsulation information, so we Reuse BIER Encapsulation Sub-TLV to carry the BIER-TE Encapsulation informations. 4.3.2. Address TLVs When the adjacency type is 0b000:Forward Connected, the BFR address information (BFR out-interface and nexthop informations) should be carried in the CCI Object. Address TLVs described in [RFC9050] are used to associate the next- hop information, so we Reuse ADDRESS TLV to carry the BFR out- interface and nexthop informations. 4.3.3. ROUTE-DISTINGUISHER TLV When the adjacency type is 0b001: Forward Routed, a VRF and the next- hop informations should be carried in the CCI Object, so we reuse the ROUTE-DISTINGUISHER TLV defined in [RFC9168] and Address TLVs defined in [RFC9050] to carry the next hop is associated with a specific VPN identified by the RD. When the adjacency type is 0b010: Local Decap, only a VRF should be carried in the CCI Object. Reuse the ROUTE-DISTINGUISHER TLV which is defined in [RFC9168] carries an RD value, used to identify a VRF. Chen, et al. Expires 9 January 2025 [Page 7] Internet-Draft PCECC BIER-TE July 2024 4.4. FEC Object BIER-TE information is always associated with adjacency, so we reuse FEC Object 1'IPv4 Node ID' and FEC Object-Type 2 'IPv6 Node ID' defined in [RFC8664] to clearly identify the adjacency for which a SI: BitPosition is being allocated. 5. Acknowledgements We would like to thank Dhruv Dhody for their useful comments and suggestions. 6. IANA Considerations TBD. 7. Security Considerations The PCECC extension are based on the existing PCEP messages and thus the security considerations described in The PCECC extension are based on the existing PCEP messages and thus the security considerations described in [RFC5440] ,[RFC8231] ,[RFC8281], and [RFC9050] apply to this draft. 8. Normative References [I-D.chen-pce-pcep-extension-pce-controller-bier] Chen, R., Zhu, C., Xu, B., Chen, H., and A. Wang, "PCEP Procedures and Protocol Extensions for Using PCE as a Central Controller (PCECC) of BIER", Work in Progress, Internet-Draft, draft-chen-pce-pcep-extension-pce- controller-bier-06, 8 July 2024, . [I-D.ietf-pce-state-sync] Litkowski, S., Sivabalan, S., Li, C., and H. Zheng, "Inter Stateful Path Computation Element (PCE) Communication Procedures.", Work in Progress, Internet-Draft, draft- ietf-pce-state-sync-07, 17 March 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Chen, et al. Expires 9 January 2025 [Page 8] Internet-Draft PCECC BIER-TE July 2024 [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, August 2006, . [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009, . [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, . [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An Architecture for Use of PCE and the PCE Communication Protocol (PCEP) in a Network with Central Control", RFC 8283, DOI 10.17487/RFC8283, December 2017, . Chen, et al. Expires 9 January 2025 [Page 9] Internet-Draft PCECC BIER-TE July 2024 [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, . [RFC8401] Ginsberg, L., Ed., Przygienda, T., Aldrin, S., and Z. Zhang, "Bit Index Explicit Replication (BIER) Support via IS-IS", RFC 8401, DOI 10.17487/RFC8401, June 2018, . [RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J. Hardwick, "Conveying Path Setup Type in PCE Communication Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408, July 2018, . [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., and J. Hardwick, "Path Computation Element Communication Protocol (PCEP) Extensions for Segment Routing", RFC 8664, DOI 10.17487/RFC8664, December 2019, . [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, . [RFC9168] Dhody, D., Farrel, A., and Z. Li, "Path Computation Element Communication Protocol (PCEP) Extension for Flow Specification", RFC 9168, DOI 10.17487/RFC9168, January 2022, . [RFC9262] Eckert, T., Ed., Menth, M., and G. Cauchie, "Tree Engineering for Bit Index Explicit Replication (BIER-TE)", RFC 9262, DOI 10.17487/RFC9262, October 2022, . Authors' Addresses Ran Chen ZTE Corporation Nanjing China Email: chen.ran@zte.com.cn Chen, et al. Expires 9 January 2025 [Page 10] Internet-Draft PCECC BIER-TE July 2024 BenChong Xu ZTE Corporation Nanjing China Email: xu.benchong@zte.com.cn Chun Zhu ZTE Corporation Nanjing China Email: zhu.chun@zte.com.cn Huaimo Chen Futurewei Nanjing, United States of America Email: Huaimo.chen@futurewei.com Aijun Wang China Telecom Nanjing China Email: wangaj3@chinatelecom.cn Chen, et al. Expires 9 January 2025 [Page 11]