PCE Working Group H. Chen Internet-Draft Futurewei Intended status: Standards Track M. Toy Expires: 16 July 2023 Verizon X. Liu IBM Corporation L. Liu Fujitsu Z. Li China Mobile 12 January 2023 PCEP Link State Abstraction draft-chen-pce-h-connect-access-12 Abstract This document presents extensions to the Path Computation Element Communication Protocol (PCEP) for a child PCE to abstract its domain information to its parent for supporting a hierarchical PCE system. 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 16 July 2023. Copyright Notice Copyright (c) 2023 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 16 July 2023 [Page 1] Internet-Draft H-Connect-Access January 2023 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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Conventions Used in This Document . . . . . . . . . . . . . . 3 4. Connections and Accesses . . . . . . . . . . . . . . . . . . 3 4.1. Information on Inter-domain Link . . . . . . . . . . . . 4 4.2. Information on ABR . . . . . . . . . . . . . . . . . . . 5 4.3. Information on Access Point . . . . . . . . . . . . . . . 5 5. Extensions to PCEP . . . . . . . . . . . . . . . . . . . . . 5 5.1. Messages for Abstract Information . . . . . . . . . . . . 6 5.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 6 5.2.1. Child Procedures . . . . . . . . . . . . . . . . . . 6 5.2.2. Parent Procedures . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 10 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 9.1. Normative References . . . . . . . . . . . . . . . . . . 11 9.2. Informative References . . . . . . . . . . . . . . . . . 11 Appendix A. Message Encoding . . . . . . . . . . . . . . . . . . 12 A.1. Extension to Existing Message . . . . . . . . . . . . . . 12 A.1.1. TLVs . . . . . . . . . . . . . . . . . . . . . . . . 12 A.1.2. Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 13 A.2. New Message . . . . . . . . . . . . . . . . . . . . . . . 14 A.2.1. CONNECTION and ACCESS Object . . . . . . . . . . . . 15 Authors’ Addresses . . . . . . . . . . . . . . . . . . . . . . . 16 1. Introduction A hierarchical PCE architecture is described in RFC 6805, in which a parent PCE maintains an abstract domain topology, which contains its child domains (seen as vertices in the topology) and the connections among them. For a domain for which a child PCE is responsible, connections attached to the domain may comprise inter-domain links and Area Border Routers (ABRs). For a parent PCE to have the abstract domain topology, each of its child PCEs needs to advertise its connections to the parent PCE. Chen, et al. Expires 16 July 2023 [Page 2] Internet-Draft H-Connect-Access January 2023 In addition to the connections attached to the domain, there may be some access points in the domain, which are the addresses in the domain to be accessible outside of the domain. For example, an address of a server in the domain that provides a number of services to users outside of the domain is an access point. This document presents extensions to the Path Computation Element Communication Protocol (PCEP) for a child PCE to advertise the information about its connections and access points to its parent PCE and for the parent PCE to build and maintain the abstract domain topology based on the information. The extensions may reduce configurations, thus simplify operations on a PCE system. A child PCE is simply called a child and a parent PCE is called a parent in the following sections. 2. Terminology ABR: Area Border Router. Router used to connect two IGP areas (Areas in OSPF or levels in IS-IS). ASBR: Autonomous System (AS) Border Router. Router used to connect together ASes via inter-AS links. TED: Traffic Engineering Database. This document uses terminology defined in [RFC5440]. 3. Conventions Used in This Document 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]. 4. Connections and Accesses A connection is an inter-domain link between two domains in general. An ABR is also a connection, which connects two special domains called areas in a same Autonomous System (AS). An access point in a domain is an address in the domain to be accessible to the outside of the domain. An access point is simply called an access. Chen, et al. Expires 16 July 2023 [Page 3] Internet-Draft H-Connect-Access January 2023 4.1. Information on Inter-domain Link An inter-domain link connects two domains in two different ASes. Since there is no IGP running over an inter-domain link, we may not obtain the information about the link generated by an IGP. We may suppose that IP addresses are configured on inter-domain links. For a point-to-point (P2P) link connecting two ABSRs A and B in two different domains, from A’s point of view, the following information about the link may be obtained: 1) Link Type: P2P 2) Local IP address 3) Remote IP address 4) Traffic engineering metric 5) Maximum bandwidth 6) Maximum reservable bandwidth 7) Unreserved bandwidth 8) Administrative group 9) SRLG We will have a link ID if it is configured; otherwise no link ID (i.e., the Router ID of the neighbor) may be obtained since no IGP adjacency over the link is formed. For a broadcast link connecting multiple ASBRs in a number of domains, on each of the ASBRs X, the same information about the link as above may be obtained except for the followings: a) Link Type: Multi-access, b) Local IP address with mask length, and c) No Remote IP address. In other words, the information about the broadcast link obtained by ASBR X comprises a), b), 4) to 9), but does not include any remote IP address or link ID. We will have a link ID if it is configured; otherwise no link ID (i.e., the interface address of the designated router for the link) may be obtained since no IGP selects it. A parent constructs an abstract AS domain topology after receiving the information about each of the inter-domain links described above from its children. Chen, et al. Expires 16 July 2023 [Page 4] Internet-Draft H-Connect-Access January 2023 RFC 5392 and RFC 5316 describe the distributions of inter-domain links in OSPF and IS-IS respectively. For each inter-domain link, its neighboring AS number and neighboring ASBR Identity (TE Router ID) need to be configured in IGP (OSPF or IS-IS). In addition, an IGP adjacency between a network node running IGP and a PCE running IGP as a component needs to be configured and fully established if we want the PCE to obtain the inter-domain link information from IGP. These configurations and IGP adjacency establishment are not needed if the extensions in this draft are used. RFC 7752 (BGP-LS) describes the distributions of TE link state information including inter-domain link state. A BGP peer between a network node running BGP and a PCE running BGP as a component needs to be configured and the peer relation must be established before the PCE can obtain the inter-domain link information from BGP. However, some networks may not run BGP. 4.2. Information on ABR For an AS running IGP and containing multiple areas, an ABR connects two or more areas. For each area connected to the ABR, the PCE as a child responsible for the area sends its parent the information about the ABR, which indicates the identifier (ID) of the ABR. A parent has the information about each of its children, which includes the domain such as the area for which the child is responsible. The parent knows all the areas to which each ABR connects after receiving the information on the ABR from each of its children. 4.3. Information on Access Point For an IP address in a domain to be accessible outside of the domain, the PCE as a child responsible for the domain sends its parent the information about the address. The parent has all the access points (i.e., IP addresses) to be accessible outside of all its children’ domains after receiving the information on the access points from each of its children. 5. Extensions to PCEP This section focuses on procedures for abstracting domain information after briefing messages containing the abstract information. Chen, et al. Expires 16 July 2023 [Page 5]