--- 1/draft-ietf-lsr-ospf-prefix-originator-06.txt 2020-10-20 04:14:48.742469223 -0700 +++ 2/draft-ietf-lsr-ospf-prefix-originator-07.txt 2020-10-20 04:14:48.778470136 -0700 @@ -1,24 +1,24 @@ LSR Working Group A. Wang Internet-Draft China Telecom Intended status: Standards Track A. Lindem -Expires: January 1, 2021 Cisco Systems +Expires: April 23, 2021 Cisco Systems J. Dong Huawei Technologies P. Psenak K. Talaulikar Cisco Systems - June 30, 2020 + October 20, 2020 OSPF Prefix Originator Extensions - draft-ietf-lsr-ospf-prefix-originator-06 + draft-ietf-lsr-ospf-prefix-originator-07 Abstract This document defines OSPF extensions to include information associated with the node originating a prefix along with the prefix advertisement. Status of This Memo This Internet-Draft is submitted in full conformance with the @@ -27,21 +27,21 @@ 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 1, 2021. + This Internet-Draft will expire on April 23, 2021. Copyright Notice Copyright (c) 2020 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 @@ -49,33 +49,30 @@ to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 3 - 2.1. Prefix Source Router-ID Sub-TLV . . . . . . . . . . . . . 4 + 2.1. Prefix Source Router-ID Sub-TLV . . . . . . . . . . . . . 3 2.2. Prefix Originator Sub-TLV . . . . . . . . . . . . . . . . 4 3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 - 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 + 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 7.1. Normative References . . . . . . . . . . . . . . . . . . 7 7.2. Informative References . . . . . . . . . . . . . . . . . 8 - Appendix A. Inter-Area Topology Retrieval Process . . . . . . . 9 - Appendix B. Special Considerations on Inter-Area Topology - Retrieval . . . . . . . . . . . . . . . . . . . . . 10 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction Prefix attributes are advertised in OSPFv2 [RFC2328] using the Extended Prefix Opaque Link State Advertisement (LSA) [RFC7684] and in OSPFv3 [RFC5340] using the various Extended Prefix LSA types [RFC8362]. The identification of the originating router for a prefix in OSPF varies by the type of the prefix and is currently not always @@ -112,25 +109,20 @@ This document proposes extensions to the OSPF protocol for inclusion of information associated with the router originating the prefix along with the prefix advertisement. These extensions do not change the core OSPF route computation functionality. They provide useful information for topology analysis and traffic engineering, especially on a controller when this information is advertised as an attribute of the prefixes via mechanisms such as Border Gateway Protocol Link- State (BGP-LS) [RFC7752]. - Applications related to use of the prefix originating node - information for topology reconstruction process on a controller and - the associated limitations are described in Appendix A and - Appendix B. - 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. Protocol Extensions @@ -185,21 +177,21 @@ TLV, Inter-Area-Prefix TLV, and External-Prefix TLV [RFC8362] when originating either an IPv4 [RFC5838] or an IPv6 prefix advertisement. The Prefix Originator Sub-TLV has the following format: 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Router Address (4 or 16 octects) | + | Router Address (4 or 16 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Prefix Originator Sub-TLV Format Where: o Type: TBD1 for OSPFv2 and TBD2 for OSPFv3 o Length: 4 or 16 @@ -207,45 +199,46 @@ router that originated the IPv4 or IPv6 prefix advertisement. Such an address would be semantically equivalent to what may be advertised in the OSPFv2 Router Address TLV [RFC3630] or in the OSPFv3 Router IPv6 Address TLV [RFC5329]. A prefix advertisement MAY include more than one Prefix Originator sub-TLV, one corresponding to each of the Equal-Cost Multi-Path (ECMP) nodes that originated the given prefix. A received Prefix Originator Sub-TLV that has an invalid length (not - 4 or 16) or a Reachable Address containing an invalid IPv4 or IPv6 + 4 or 16) or a Router Address containing an invalid IPv4 or IPv6 address (dependent on address family of the associated prefix) MUST be considered invalid and ignored. Additionally, reception of such Sub-TLV SHOULD be logged as an error (subject to rate-limiting). [RFC7794] provides similar functionality for the Intermediate System to Intermediate System (IS-IS) protocol. 3. Elements of Procedure This section describes the procedure for advertisement of the Prefix Source Router-ID and Prefix Originator Sub-TLVs along with the prefix advertisement. The OSPF Router ID of the Prefix Source Router-ID is set to the OSPF Router ID of the node originating the prefix in the OSPF domain. If the originating node is advertising an OSPFv2 Router Address TLV [RFC3630] or an OSPFv3 Router IPv6 Address TLV [RFC5329], then that value is set in the Router Address field of the Prefix Originator - Sub-TLV. When the orignating node is not advertising such an + Sub-TLV. When the originating node is not advertising such an address, implementations MAY support mechanisms to determine a - reachable address belonging to the originating node to set in the - Router Address field. Such mechanisms are outside the scope of this - document. + reachable address (e.g., advertised with the N-flag set [RFC7684] or + N-bit set [RFC8362] and either matching the OSPF Router ID or the + highest IP address) belonging to the originating node to set in the + Router Address field. Implementations MAY support the selection of specific prefixes for which the originating node information needs to be included with their prefix advertisements. When an ABR generates inter-area prefix advertisements into its non- backbone areas corresponding to an inter-area prefix advertisement from the backbone area, the only way to determine the originating node information is based on the Prefix Source Router-ID and Prefix Originator Sub-TLVs present in the inter-area prefix advertisement @@ -309,22 +302,22 @@ | 27 | Prefix Source Router-ID Sub-TLV | early allocation done | | TBD2 | Prefix Originator Sub-TLV | pending | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Code Points in OSPFv3 Extended-LSA Sub-TLVs 6. Acknowledgement Many thanks to Les Ginsberg for his suggestions on this draft. Also thanks to Jeff Tantsura, Rob Shakir, Gunter Van De Velde, Goethals - Dirk, Smita Selot, Shaofu Peng, and John E Drake for their valuable - comments. + Dirk, Smita Selot, Shaofu Peng, John E Drake and Baalajee S for their + review and valuable comments. 7. References 7.1. 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, . @@ -375,101 +368,22 @@ R. Aggarwal, "Support of Address Families in OSPFv3", RFC 5838, DOI 10.17487/RFC5838, April 2010, . [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, . -Appendix A. Inter-Area Topology Retrieval Process - - When an IP SDN Controller receives BGP-LS [RFC7752] information, it - should compare the prefix Network Layer Reachability Information - (NLRI) that is included in the BGP-LS NLRI. When it encounters the - same prefix but with different source router ID, it should extract - the corresponding area-ID, rebuild the link between these two source - routers in the non-backbone area. Below is one example that based on - the Figure 5 which illustrates a topology where OSPF is running in - multiple areas. - - +-----------------+ - |IP SDN Controller| - +--------+--------+ - | - | BGP-LS - | - +---------------------+------+--------+-----+--------------+ - | +--+ +--+ ++-+ ++-+ +-++ + -+ +--+| - | |S1+--------+S2+---+R1+---|R0+----+R2+---+T1+--------+T2|| - | +-++ N1 +-++ ++-+ +--+ +-++ ++++ N2 +-++| - | | | | | || | | - | | | | | || | | - | +-++ +-++ ++-+ +-++ ++++ +-++| - | |S4+--------+S3+---+R3+-----------+R4+---+T3+--------+T4|| - | +--+ +--+ ++-+ +-++ ++-+ +--+| - | | | | - | | | | - | Area 1 | Area 0 | Area 2 | - +---------------------+---------------+--------------------+ - - Figure 5: OSPF Inter-Area Prefix Originator Scenario - - R0-R4 are routers in the backbone area, S1-S4 are internal routers in - area 1, and T1-T4 are internal routers in area 2. R1 and R3 are ABRs - between area 0 and area 1. R2 and R4 are ABRs between area 0 and - area 2. N1 is the network between router S1 and S2 and N2 is the - network between router T1 and T2. Ls1 is the loopback address of - Node S1 and Lt1 is the loopback address of Node T1. - - Assuming we want to rebuild the connection between router S1 and - router S2 located in area 1: - - a. Normally, router S1 will advertise prefix N1 within its router- - LSA. - - b. When this router-LSA reaches the ABR router R1, it will convert - it into summary-LSA, add the Source Router-ID Sub-TLV and the - Prefix Originator Sub-TLV, as described in Section 3. - - c. R1 then floods this extension summary-LSA to R0, which is using - the BGP-LS protocol with IP SDN Controller. The controller then - knows the prefix for N1 is from S1. - - d. Router S2 will perform a similar process, and the controller will - also learn that prefix N1 is also from S2. - - e. Then it can reconstruct the link between S1 and S2, using the - prefix N1. The topology within Area 1 can then be reconstructed - accordingly. - - Iterating the above process continuously, the IP SDN controller can - retrieve a detailed topology that spans multiple areas. - -Appendix B. Special Considerations on Inter-Area Topology Retrieval - - The above topology retrieval process can be applied in the case where - each point-to-point or multi-access link connecting routers is - assigned a unique prefix. However, there are some situations where - this heuristic cannot be applied. Specifically, the cases where the - link is unnumbered or the prefix corresponding to the link is an - anycast prefix. - - The Appendix A heuristic to rebuild the topology can normally be used - if all links are numbered. For anycast prefixes, if it corresponds - to the loopback interface and has a host prefix length, i.e., 32 for - IPv4 prefixes and 128 for IPv6 prefixes, Appendix A can also applied - since these anycast prefixes are not required to reconstruct the - topology. - Authors' Addresses + Aijun Wang China Telecom Beiqijia Town, Changping District Beijing 102209 China Email: wangaj3@chinatelecom.cn Acee Lindem Cisco Systems