LSR R. Chen Internet-Draft D. Zhao Intended status: Standards Track ZTE Corporation Expires: 19 April 2024 P. Psenak K. Talaulikar Cisco Systems 17 October 2023 Prefix Flag Extension for OSPFv2 and OSPFv3 draft-chen-lsr-prefix-extended-flags-01 Abstract Within OSPF, each prefix is advertised along with an 8-bit field of capabilities, by using the Prefix Options (OSPFv3) and the flag flield in the OSPFv2 Extended Prefix TLV (OSPFv2). However, for OSPFv3, all the bits of the Prefix Options have already been assigned, and for OSPFv2, there are not many undefined bits left in the OSPFv2 Extended Prefix TLV. This document solves the problem of insufficient existing flags, and defines the variable length Prefix attributes Sub-TLV for OSPFv2 and OSPFv3 for the extended flag fields. 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 19 April 2024. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. Chen, et al. Expires 19 April 2024 [Page 1] Internet-Draft Anycast Property advertisement October 2023 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Variable length Prefix attributes Sub-TLV . . . . . . . . . . 3 3. Processing . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Backward Compatibility . . . . . . . . . . . . . . . . . . . 5 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6.1. OSPFv2 Extended Prefix Sub-TLV Registry . . . . . . . . . 5 6.1.1. OSPFv2 Prefix Extended Flags Field . . . . . . . . . 5 6.2. OSPFv3 Extended LSA Sub-TLV Registry . . . . . . . . . . 6 6.2.1. OSPFv3 Prefix Extended Flags Field . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. Informative References . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction Within OSPF, each prefix is advertised along with an 8-bit field of capabilities,by using the Prefix Options[RFC5340] and the flag flield in the OSPFv2 Extended Prefix TLV [RFC7684]. However, for OSPFv3, all the bits of the Prefix Options have already been assigned, and for OSPFv2, there are not many undefined bits left in the OSPFv2 Extended Prefix TLV. As defined in [RFC5340], the length of the Flag field is 8 bits, and all of the bits have already been defined as shown in Table 1. This document extends the Flag field for future use by defining a new variable length Prefix attributes Sub-TLV for an extended Flag. Chen, et al. Expires 19 April 2024 [Page 2] Internet-Draft Anycast Property advertisement October 2023 +=======+===================+=======================================+ | Value | Description | Reference | +=======+===================+=======================================+ | 0x80 | AC-bit | [I-D.ietf-lsr-ospfv3-srv6-extensions] | +-------+-------------------+---------------------------------------+ | 0x01 | NU-bit | [RFC5340] | +-------+-------------------+---------------------------------------+ | 0x02 | LA-bit | [RFC5340] | +-------+-------------------+---------------------------------------+ | 0x04 | Deprecated | [RFC5340] | +-------+-------------------+---------------------------------------+ | 0x08 | P-bit | [RFC5340] | +-------+-------------------+---------------------------------------+ | 0x10 | DN-bit | [RFC5340] | +-------+-------------------+---------------------------------------+ | 0x20 | N-bit | [RFC8362] | +-------+-------------------+---------------------------------------+ | 0x40 | E-Flag (ELC | [RFC9089] | | | Flag) | | +-------+-------------------+---------------------------------------+ Table 1: OSPFv3 Prefix Options (8 bits) 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. Variable length Prefix attributes Sub-TLV This document creates a new variable length Prefix attributes Sub-TLV for OSPFv2 and OSPFv3. This Sub-TLV specifies a variable flag fields to advertise additional attributes associated with the prefix. The format of each 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Prefix Attribute Flags(Variable) // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Chen, et al. Expires 19 April 2024 [Page 3] Internet-Draft Anycast Property advertisement October 2023 where: Type: TBD. Length: Variable, dependent on the included Prefix Attribute Flags. It MUST be a multiple of 4 octets. Prefix Attribute Flags: Variable. The extended flag fields. This contains an array of units of 32-bit flags numbered from the most significant as bit zero. Currently, For ospfv3, two new bits (U-Flag and UP-Flag) are defined as described in [I-D.ietf-lsr-igp-ureach-prefix-announce]. For ospfv2, no bits are defined. Unassigned bits MUST be set to zero on transmission and MUST be ignored on receipt. Bits that are NOT transmitted MUST be treated as if they are set to 0 on receipt. In the case of OSPFv2,the Prefix attributes Sub-TLVs is a sub-TLV of the OSPFv2 Extended Prefix TLV as defined in [RFC7684]. In the case of OSPFv3, the Prefix attributes Sub-TLVs is a sub-TLV of the following OSPFv3 TLVs as defined in [RFC8362]: * Intra-Area Prefix TLV * Inter-Area Prefix TLV * External Prefix TLV 3. Processing The Extended Flags field is an array of units of 32 flags that are allocated starting from the most significant bit. The bits of the Extended Flags field will be assigned by future documents. This document does not define any flags. Flags that an implementation is not supporting MUST be set to zero on transmission. Implementations that do not understand any particular flag MUST ignore the flag. Note that devices MUST handle varying lengths of the Prefix attributes Sub-TLV. If a device receives the Prefix attributes Sub-TLV of a length more than it currently supports or understands, it MUST ignore the bits beyond that length. Chen, et al. Expires 19 April 2024 [Page 4] Internet-Draft Anycast Property advertisement October 2023 If a device receives the Prefix attributes Sub-TLV of a length less than the one supported by the implementation, it MUST act as if the bits beyond the length were not set. 4. Backward Compatibility The Prefix attributes Sub-TLV defined in this document does not introduce any backward compatibility issues. An implementation that does not understand or support the Prefix attributes Sub-TLV MUST ignore the TLV. Further, any additional bits in the OSPFv2/OSPFv3 Prefix attributes Sub-TLV that are not understood by an implementation MUST be ignored. 5. Acknowledgements TBD. 6. IANA Considerations This document requests allocation for the following registry. 6.1. OSPFv2 Extended Prefix Sub-TLV Registry This document requests allocation for OSPFv2 Extended Prefix Sub-TLV Registry: Value Description Reference ------ ---------------------------------- -------------- TBD OSPFv2 Prefix attributes Sub-TLV This document 6.1.1. OSPFv2 Prefix Extended Flags Field This document adds "OSPFv2 Prefix Extended TLV Flag Field" registry in the "OSPFv2 Prefix attributes Sub-TLV" registry to manage the Prefix Extended Flags field of the OSPFv2 Extended Prefix Sub-TLV. Each bit should be tracked with the following qualities: * Bit number (counting from bit 0 as the most significant bit) * Description * Reference No values are currently defined. Bits 0-31 are initially marked as "Unassigned". Bits with a higher ordinal than 31 will be added to the registry in future documents if necessary. Chen, et al. Expires 19 April 2024 [Page 5] Internet-Draft Anycast Property advertisement October 2023 6.2. OSPFv3 Extended LSA Sub-TLV Registry This document requests allocation for OSPFv3 Extended LSA Sub-TLV Registry: Value Description Reference ------ ---------------------------------- -------------- TBD OSPFv3 Prefix attributes Sub-TLV This document 6.2.1. OSPFv3 Prefix Extended Flags Field This document adds "OSPFv3 Prefix Extended TLV Flag Field" registry in the "OSPFv3 Prefix attributes Sub-TLV" registry to manage the Prefix Extended Flags field of the OSPFv3 Extended Prefix Sub-TLV. Each bit should be tracked with the following qualities: * Bit number (counting from bit 0 as the most significant bit) * Description * Reference Bits 0-31 are initially marked as "Unassigned". Bits with a higher ordinal than 31 will be added to the registry in future documents if necessary. 7. Security Considerations Procedures and protocol extensions defined in this document do not affect the OSPFv2 , OSPFv3 security model. See the "Security Considerations"section of [RFC7684] for a discussion of OSPFv2 security, the "Security Considerations"section of [RFC8362] for a discussion of OSPFv3 security. 8. Informative References [I-D.ietf-lsr-igp-ureach-prefix-announce] Psenak, P., Filsfils, C., Litkowski, S., Voyer, D., Dhamija, A., Hegde, S., Van de Velde, G., and G. S. Mishra, "IGP Unreachable Prefix Announcement", Work in Progress, Internet-Draft, draft-ietf-lsr-igp-ureach- prefix-announce-00, 11 September 2023, . Chen, et al. Expires 19 April 2024 [Page 6] Internet-Draft Anycast Property advertisement October 2023 [I-D.ietf-lsr-ospfv3-srv6-extensions] Li, Z., Hu, Z., Talaulikar, K., and P. Psenak, "OSPFv3 Extensions for SRv6", Work in Progress, Internet-Draft, draft-ietf-lsr-ospfv3-srv6-extensions-15, 21 June 2023, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008, . [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, . [RFC9089] Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S., and M. Bocci, "Signaling Entropy Label Capability and Entropy Readable Label Depth Using OSPF", RFC 9089, DOI 10.17487/RFC9089, August 2021, . Authors' Addresses Ran Chen ZTE Corporation Nanjing China Email: chen.ran@zte.com.cn Chen, et al. Expires 19 April 2024 [Page 7] Internet-Draft Anycast Property advertisement October 2023 Detao Zhao ZTE Corporation Nanjing China Email: zhao.detao@zte.com.cn Peter Psenak Cisco Systems Slovakia Email: ppsenak@cisco.com Ketan Talaulikar Cisco Systems India Email: ketant.ietf@gmail.com Chen, et al. Expires 19 April 2024 [Page 8]