Internet Engineering Task Force H. Chen Internet-Draft Futurewei Intended status: Standards Track 15 August 2022 Expires: 16 February 2023 OSPF Abnormal State Information draft-chen-ospf-abnormal-state-info-08 Abstract This document describes a couple of options for an OSPF router to advertise its abnormal state information in a routing domain. 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 February 2023. Copyright Notice Copyright (c) 2022 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 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. Chen Expires 16 February 2023 [Page 1] Internet-Draft OSPF Abnormal State August 2022 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Conventions Used in This Document . . . . . . . . . . . . . . 3 4. OSPF Router State Information LSA . . . . . . . . . . . . . . 3 4.1. OSPFv2 Router State Information (RSI) Opaque LSA . . . . 3 4.2. OSPFv3 Router State Information (RSI) Opaque LSA . . . . 4 4.3. OSPF Router State Information (RSI) TLV . . . . . . . . . 4 5. Attach RSI TLV to Router Inforamtion LSA . . . . . . . . . . 6 6. Notify Other Systems . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10.1. Normative References . . . . . . . . . . . . . . . . . . 6 10.2. Informative References . . . . . . . . . . . . . . . . . 7 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction There may be some states that are not normal in an OSPF router, which include the state that a link state advertisement (LSA) stays in a retransmission list on the router for more than a given time period such as more than hello dead interval, and may include the state that a database description (DD) packet does not get acknowledged for a given period of time. If a link state advertisement (LSA) with a topology change in a router can not get through over an OSPF interface for a given time period, some of the routers in the routing domain may have different view of the real network topology, thus routing loops may occur and some traffic may get dropped. It is useful for an OSPF router in a routing domain to advertise its abnormal state information to other routers, or notify some systems such as an event management or monitoring system for its abnormal state. This document describes a couple of options for an OSPF router to advertise its abnormal state information in a routing domain. 2. Terminology This document uses terminologies defined in RFC 4970, RFC 2328, and RFC 2740. Chen Expires 16 February 2023 [Page 2] Internet-Draft OSPF Abnormal State August 2022 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 RFC 2119. 4. OSPF Router State Information LSA OSPF routers MAY advertise their state information in a area-scoped or AS-scoped router state information LSA with a router state informatioin TLV. 4.1. OSPFv2 Router State Information (RSI) Opaque LSA OSPFv2 routers will advertise an area-scoped or AS-scoped Router State Information Opaque-LSA [RFC 2370], which has an Opaque type of 5 and Opaque ID of 0. The RSI LSA will be originated initially by an OSPF router when an OSPF instance is created and re-originated in every refresh interval (LSRefreshTime) with the current state information of the router. When the current state information changes, the RSI LSA will also be originated. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS age | Options | 10/11 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 5 | 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertising Router | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS sequence number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LS checksum | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | +- TLVs -+ | ... | Figure 1: OSPFv2 Router State Information Opaque LSA The format of the TLVs within the body of a RSI LSA is the same as the format used by the Traffic Engineering Extensions to OSPF [RFC 3630]. The LSA payload consists of one or more nested Type/Length/ Value (TLV) triplets. The format of each TLV is: Chen Expires 16 February 2023 [Page 3] Internet-Draft OSPF Abnormal State August 2022 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: TLV Format The Length field defines the length of the value portion in octets (thus a TLV with no value portion would have a length of 0). The TLV is padded to 4-octet alignment; padding is not included in the length field (so a 3-octet value would have a length of 3, but the total size of the TLV would be 8 octets). Nested TLVs are also 32-bit aligned. For example, a 1-byte value would have the length field set to 1, and 3 octets of padding would be added to the end of the value portion of the TLV. Unrecognized types are ignored. 4.2. OSPFv3 Router State Information (RSI) Opaque LSA TBD. 4.3. OSPF Router State Information (RSI) TLV A router advertising a RSI LSA MAY include the Router State Information TLV. If included, it MUST be the first TLV in the LSA. Additionally, the TLV MUST accurately reflect the OSPF router's state information in the scope advertised. The format of the Router State Information TLV is as follows: 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 (1) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | State Information sub-TLVs | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Router State Information TLV Type: A 2-octet field set to 1. Length: A 2-octet field that indicates the length of the value portion in octets and will be the total number of octets that state information sub-TLVs use. Chen Expires 16 February 2023 [Page 4] Internet-Draft OSPF Abnormal State August 2022 Value: A variable length sequence of router state information sub- TLVs. The format of the Router State Information LSA retranmission time sub-TLV is as follows: 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 (1) | Length (2) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Max LSA retransmission time | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Retranmission Time Sub-TLV Type: A 2-octet field set to 1. Length: A 2-octet field that indicates the length of the value portion in octets and will be 2. Value: A 2-octet field set to the current maximum time (in seconds) that an LSA stays in a retransmission list in a router. The format of the sub-TLV for the maximum time that a Database Description packet is not acknowledged is illustrated 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type (2) | Length (2) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Max time DD not acked | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Maximum DD Time Sub-TLV Type: A 2-octet field set to 2. Length: A 2-octet field that indicates the length of the value portion in octets and will be 2. Value: A 2-octet field set to the current maximum time (in seconds) for which a DD packet is not acknowledged in a router. Chen Expires 16 February 2023 [Page 5] Internet-Draft OSPF Abnormal State August 2022 5. Attach RSI TLV to Router Inforamtion LSA Instead of using a Router State Information LSA to advertise the abnormal state information for a router, we may use the existing Router Information LSA defined in RFC 4970 to advertise the state information through adding the Router State Information (RSI) TLV into the Router Inforamtion LSA. When a Router State Information (RSI) TLV is put into a Router Information LSA, the type of the TLV may be different from the one mentioned in the section above. 6. Notify Other Systems An OSPF router may also notify other systems such as an event management system about its abnormal state when the abnormal state occurs in the router. 7. Security Considerations The mechanism described in this document does not raise any new security issues for the OSPF protocols. 8. IANA Considerations tb 9. Acknowledgement The author would like to thank people for their valuable comments on this draft. 10. References 10.1. 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, . [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, DOI 10.17487/RFC2328, April 1998, . [RFC2370] Coltun, R., "The OSPF Opaque LSA Option", RFC 2370, DOI 10.17487/RFC2370, July 1998, . Chen Expires 16 February 2023 [Page 6] Internet-Draft OSPF Abnormal State August 2022 [RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC 2740, DOI 10.17487/RFC2740, December 1999, . [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, DOI 10.17487/RFC3630, September 2003, . [RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and S. Shaffer, "Extensions to OSPF for Advertising Optional Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July 2007, . 10.2. Informative References [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The OSPF Opaque LSA Option", RFC 5250, DOI 10.17487/RFC5250, July 2008, . Author's Address Huaimo Chen Futurewei Boston, MA, United States of America Email: Huaimo.chen@futurewei.com Chen Expires 16 February 2023 [Page 7]