PCE Q. Xiong Internet-Draft S. Peng Intended status: Standards Track ZTE Corporation Expires: 27 August 2025 V. Beeram T. Saad Juniper Networks M. Koldychev Cisco Systems 23 February 2025 Path Computation Element Communication Protocol (PCEP) Extensions for Topology Filter draft-xpbs-pce-topology-filter-03 Abstract This document proposes a set of extensions for Path Computation Element Communication Protocol (PCEP) to support the topology filter during path computation. 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 27 August 2025. Copyright Notice Copyright (c) 2025 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 Xiong, et al. Expires 27 August 2025 [Page 1] Internet-Draft PCEP Extensions for Topology Filter February 2025 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Topology Filter with PCE . . . . . . . . . . . . . . . . . . 3 3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. TOPOLOGY-FILTER Object . . . . . . . . . . . . . . . . . 4 3.1.1. IGP Domain Identifier TLV . . . . . . . . . . . . . . 4 3.1.2. TE Topology Identifier TLV . . . . . . . . . . . . . 5 3.1.3. Filtering Rules TLV . . . . . . . . . . . . . . . . . 6 3.1.3.1. Link ID sub-TLV . . . . . . . . . . . . . . . . . 7 3.1.3.2. Admin Group sub-TLV . . . . . . . . . . . . . . . 8 3.1.3.3. Source Protocol sub-TLV . . . . . . . . . . . . . 8 3.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 9 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 4.1. TOPOLOGY-FILTER Object . . . . . . . . . . . . . . . . . 9 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 7.1. Normative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction [RFC5440] describes the Path Computation Element Computation Protocol (PCEP) which is used between a Path Computation Element (PCE) and a Path Computation Client (PCC) (or other PCE) to enable computation of Multi-protocol Label Switching (MPLS) for Traffic Engineering Label Switched Path (TE LSP). PCEP Extensions for the Stateful PCE Model [RFC8231] describes a set of extensions to PCEP to enable active control of MPLS-TE and Generalized MPLS (GMPLS) tunnels. As depicted in [RFC4655], a PCE MUST be able to compute the path of a TE LSP by operating on the TED and considering bandwidth and other constraints applicable to the TE LSP service request. A PCE always perform path computation based on the network topology information collected through BGP-LS [RFC9552]. BGP-LS can get multiple link-state data from multiple IGP instance, or multiple virtual topologies from a single IGP instance. In some cases, as per [I-D.ietf-teas-yang-topology-filter], a path may be computed within a network topology such as a specified topology, a topology associated with a specific IGP domain, a topology learnt from a specific TE information source, a topology defined by the application of one or Xiong, et al. Expires 27 August 2025 [Page 2] Internet-Draft PCEP Extensions for Topology Filter February 2025 more topology filters, a topology associated with an Network Resource Partition (NRP) and so on. The PCE MUST take the topology related constraints into consideration during the path computation. As defined in [I-D.ietf-teas-yang-topology-filter], a topology filter is a data construct that is used to filter network topologies. This document proposes a set of extensions for PCEP to support the topology filter during path computation. 1.1. Terminology The terminology is defined as [RFC5440], [RFC9552] and [RFC8795]. 1.2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 2. Topology Filter with PCE As defined in [I-D.ietf-teas-yang-topology-filter], a topology filter specifies the topology reference or a set of filtering rules. The topology filters carry a list of topology filters and a topology filter-set constitutes a list of topology filter references. The topology reference indicates a predefined TE topology or a specific IGP domain. A TE topology can be identified from a global scope such as a provider ID, a client ID or a topology ID. And a specific IGP domain can be identified by protocol ID, instance ID, division ID, algo ID and MT ID. The PCE should consider these identifiers as topology constraints during path computation. The filtering rules specify a set of constraints on the topology including include-any, include-all and exclude. A set of attributes that can be used as rules to filter the topology such as link affinity, link name, node prefix, AS number and TE information source. The filtering rules of these attributes can be used to compute path at PCE. 3. PCEP Extensions Xiong, et al. Expires 27 August 2025 [Page 3] Internet-Draft PCEP Extensions for Topology Filter February 2025 3.1. TOPOLOGY-FILTER Object This document defines a new TOPOLOGY-FILTER object to carry the topology filter. The TOPOLOGY-FILTER object is optional and specifies the specific topology to be taken into account by the PCE during path computation. The TOPOLOGY-FILTER object can be carried within a PCReq message, or a PCRep message in case of unsuccessful path computation. TOPOLOGY-FILTER Object-Class is TBD1. TOPOLOGY-FILTER Object-Type is TBD2. The format of the TOPOLOGY-FILTER 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: TOPOLOGY-FILTER Body Object Format Reserved (24 bits): This field MUST be set to zero on transmission and MUST be ignored on receipt. Flags (8 bits): No flags are currently defined. Unassigned flags MUST be set to zero on transmission and MUST be ignored on receipt. The format of optional TLVs is defined in [RFC5440] and may be used to carry topology filter information as defined in section. 3.1.1. IGP Domain Identifier TLV As defined in [RFC9552], the IGP domain has a unique IGP representation by using the combination of OSPF Area-ID, Router-ID, Protocol-ID, Multi-Topology Identifier (MT-ID), and BGP-LS Instance- ID. This document defines a new IGP Domain Identifier TLV for topology filter to identify a IGP domain within a referenced topology. The IGP Domain Identifier TLV is optional and the format is as following shown: Xiong, et al. Expires 27 August 2025 [Page 4] Internet-Draft PCEP Extensions for Topology Filter February 2025 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=TBD3 | Length=24 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol-ID | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Instance-ID | | (64 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OSPF Area-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm-ID | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Multi-Topology-ID | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: IGP Domain Identifier TLV The code point for the TLV type is TBD3. The TLV length is 24 octets. Protocol-ID (8 bits): defined in [RFC9552] section 5.2. Instance-ID (64 bits): defined in [RFC9552] section 5.2. OSPF Area-ID (32 bits): defined in [RFC9552] section 5.2.1.4. Algorithm-ID (8 bits): defined in [I-D.ietf-pce-sid-algo] section 3.4. Multi-Topology-ID (16 bits): defined in [RFC9552] section 5.2.2.1. Reserved: This fields MUST be set to zero on transmission and MUST be ignored on receipt. 3.1.2. TE Topology Identifier TLV This document defines a new TE Topology Identifier TLV for topology filter to identify a predefined TE topology within a referenced topology. The TE Topology Identifier TLV is optional and the format is as following shown: Xiong, et al. Expires 27 August 2025 [Page 5] Internet-Draft PCEP Extensions for Topology Filter February 2025 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=12 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Provider ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Client ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Topology ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: TE Topology Identifier TLV The code point for the TLV type is TBD4. The TLV length is 12 octets. Provider ID (32 bits): defined in [RFC8776]. Client ID (32 bits): defined in [RFC8776]. Topology ID (32 bits): defined in [RFC8776]. 3.1.3. Filtering Rules TLV This document defines a new Filtering Rules TLV for topology filter to carry a set of constrains on the topology by include-any, include- all and exclude. The Filtering Rules TLV is optional and the format is as following shown : Xiong, et al. Expires 27 August 2025 [Page 6] Internet-Draft PCEP Extensions for Topology Filter February 2025 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Include-any | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Include-all | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Exclude | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional sub-TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Filtering Rules TLV The code point for the TLV type is TBD5. The TLV length is variable. The sub-TLVs carry the attributes that can be used as rules to filter the topology. 3.1.3.1. Link ID sub-TLV The Link ID is used to identify the link that is used during the path calculation. The Link ID sub-TLV is defined: 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 | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Link ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Link ID sub-TLV The code point for the TLV type is TBD6. The TLV length is 6 octets. Link ID (32bits ): defined in IS-IS [RFC5307] and OSPF [RFC3630]. Xiong, et al. Expires 27 August 2025 [Page 7] Internet-Draft PCEP Extensions for Topology Filter February 2025 3.1.3.2. Admin Group sub-TLV The Admin Group is used to include the links that is used during the path calculation. 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=TBD7 | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extended Admin Group | +- -+ | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Admin Group sub-TLV The code point for the sub-TLV type is TBD7. The length is variable. Extended Administrative Group: Extended Administrative Group as defined in [RFC7308]. 3.1.3.3. Source Protocol sub-TLV The format of the Source Protocol sub-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 | Reserved | Protocol-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Instance-ID | | (64 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: Source Protocol sub-TLV The code point for the TLV type is TBD8. The TLV length is 10 octets. Protocol-ID (8 bits): defined in [RFC9552] section 5.2. Instance-ID (64 bits): defined in [RFC9552] section 5.2. Xiong, et al. Expires 27 August 2025 [Page 8] Internet-Draft PCEP Extensions for Topology Filter February 2025 3.2. Procedures A PCC MAY insert a TOPOLOGY-FILTER object in PCReq message to indicate the specific topology that MUST be considered by the PCE during path computation. The PCE will compute the path with the constrains with the filtering rules and reply the result to the PCC with a PCRep message. The PCE could perform path computation based on the topology identified by the topology filter rules that can be applied on either the native topology or a user specified topology. The absence of the IGP Domain Identifier TLV and TE Topology Identifier TLV indicate that the PCE should compute within a native topology and only Filtering Rules TLV is applied as the filtering rules. 4. IANA Considerations 4.1. TOPOLOGY-FILTER Object IANA is requested to make allocations for Topology Filter Object from the registry, as follows: TOPOLOGY-FILTER Object-Class is TBD1. TOPOLOGY-FILTER Object-Type is TBD2. The TLVs for Topology Filter Object is as follows: +======+============================+=================+ | Type | TLV | Reference | +======+============================+=================+ | TBD3 | IGP Domain Identifier TLV | [this document] | +------+----------------------------+-----------------+ | TBD4 | TE Topology Identifier TLV | [this document] | +------+----------------------------+-----------------+ | TBD5 | Filtering Rules TLV | [this document] | +------+----------------------------+-----------------+ Table 1: TLVs for Topology Filter Object IANA is requested to make allocations for sub-TLVs from the registry, as follows: Xiong, et al. Expires 27 August 2025 [Page 9] Internet-Draft PCEP Extensions for Topology Filter February 2025 +======+==================================+=================+ | Type | sub-TLVs for Filtering Rules TLV | Reference | +======+==================================+=================+ | TBD6 | Link ID sub-TLV | [this document] | +------+----------------------------------+-----------------+ | TBD7 | Admin Group sub-TLV | [this document] | +------+----------------------------------+-----------------+ | TBD8 | Source Protocol sub-TLV | [this document] | +------+----------------------------------+-----------------+ Table 2: Sub-TLVs 5. Acknowledgements TBA 6. Security Considerations TBA 7. References 7.1. Normative References [I-D.ietf-pce-sid-algo] Sidor, S., Rose, Z., Peng, S., Peng, S., and A. Stone, "Carrying SR-Algorithm in Path Computation Element Communication Protocol (PCEP).", Work in Progress, Internet-Draft, draft-ietf-pce-sid-algo-17, 13 January 2025, . [I-D.ietf-teas-yang-topology-filter] Beeram, V. P., Saad, T., Gandhi, R., and X. Liu, "YANG Data Model for Topology Filter", Work in Progress, Internet-Draft, draft-ietf-teas-yang-topology-filter-00, 11 October 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, . Xiong, et al. Expires 27 August 2025 [Page 10] Internet-Draft PCEP Extensions for Topology Filter February 2025 [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, August 2006, . [RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P. Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF", RFC 4915, DOI 10.17487/RFC4915, June 2007, . [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, . [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, . [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009, . [RFC5521] Oki, E., Takeda, T., and A. Farrel, "Extensions to the Path Computation Element Communication Protocol (PCEP) for Route Exclusions", RFC 5521, DOI 10.17487/RFC5521, April 2009, . [RFC6549] Lindem, A., Roy, A., and S. Mirtorabi, "OSPFv2 Multi- Instance Extensions", RFC 6549, DOI 10.17487/RFC6549, March 2012, . [RFC7308] Osborne, E., "Extended Administrative Groups in MPLS Traffic Engineering (MPLS-TE)", RFC 7308, DOI 10.17487/RFC7308, July 2014, . [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and S. Ray, "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP", RFC 7752, DOI 10.17487/RFC7752, March 2016, . Xiong, et al. Expires 27 August 2025 [Page 11] Internet-Draft PCEP Extensions for Topology Filter February 2025 [RFC8202] Ginsberg, L., Previdi, S., and W. Henderickx, "IS-IS Multi-Instance", RFC 8202, DOI 10.17487/RFC8202, June 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, . [RFC8776] Saad, T., Gandhi, R., Liu, X., Beeram, V., and I. Bryskin, "Common YANG Data Types for Traffic Engineering", RFC 8776, DOI 10.17487/RFC8776, June 2020, . [RFC8795] Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and O. Gonzalez de Dios, "YANG Data Model for Traffic Engineering (TE) Topologies", RFC 8795, DOI 10.17487/RFC8795, August 2020, . [RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and Traffic Engineering Information Using BGP", RFC 9552, DOI 10.17487/RFC9552, December 2023, . Authors' Addresses Quan Xiong ZTE Corporation China Email: xiong.quan@zte.com.cn Shaofu Peng ZTE Corporation No.50 Software Avenue Nanjing Jiangsu, 210012 China Email: peng.shaofu@zte.com.cn Vishnu Pavan Beeram Juniper Networks Email: vbeeram@juniper.net Xiong, et al. Expires 27 August 2025 [Page 12] Internet-Draft PCEP Extensions for Topology Filter February 2025 Tarek Saad Juniper Networks Email: tsaad@juniper.net Mike Koldychev Cisco Systems Canada Email: mkoldych@cisco.com Xiong, et al. Expires 27 August 2025 [Page 13]