LSR R. Chen Internet-Draft D. Zhao Intended status: Standards Track ZTE Corporation Expires: 12 April 2025 P. Psenak K. Talaulikar Cisco Systems L. Gong China mobile 9 October 2024 Prefix Flag Extension for OSPFv2 and OSPFv3 draft-ietf-lsr-ospf-prefix-extended-flags-03 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 Attribute Flags Sub-TLVs for OSPFv2 and OSPFv3 respectively 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 12 April 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Chen, et al. Expires 12 April 2025 [Page 1] Internet-Draft Prefix Flag Extension for OSPF October 2024 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 . . . . . . . . . . . . . . . . . . 4 2. Variable length Prefix Attribute Flags Sub-TLVs . . . . . . . 4 2.1. OSPFv2 Prefix Attribute Flags Sub-TLV . . . . . . . . . . 4 2.2. OSPFv3 Prefix Attribute Flags Sub-TLV . . . . . . . . . . 5 3. Processing . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Backward Compatibility . . . . . . . . . . . . . . . . . . . 6 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 6.1. OSPFv2 Prefix Attribute Flags Sub-TLV Registry . . . . . 7 6.1.1. OSPFv2 Prefix Extended Flags Field Registry . . . . . 7 6.2. OSPFv3 Prefix Attribute Flags Sub-TLV Registry . . . . . 7 6.2.1. OSPFv3 Prefix Extended Flags Field Registry . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 8.2. Informative References . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 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. For OSPFv2, as defined in [RFC7684], the length of the Flag field is 8 bits, and there are not many undefined bits left in the OSPFv2 Extended Prefix TLV that are undefined as shown in Table 1. Chen, et al. Expires 12 April 2025 [Page 2] Internet-Draft Prefix Flag Extension for OSPF October 2024 +=======+=============+===========================================+ | Value | Description | Reference | +=======+=============+===========================================+ | 0x80 | A | [RFC7684] | +-------+-------------+-------------------------------------------+ | 0x40 | N | [RFC7684] | +-------+-------------+-------------------------------------------+ | 0x20 | E-Flag(ELC | [RFC9089] | | | Flag) | | +-------+-------------+-------------------------------------------+ | TBD | U | [I-D.ietf-lsr-igp-ureach-prefix-announce] | +-------+-------------+-------------------------------------------+ | TBD | UP | [I-D.ietf-lsr-igp-ureach-prefix-announce] | +-------+-------------+-------------------------------------------+ Table 1: OSPFv2 Extended Prefix TLV Flags (8 bits) For OSPFv3, 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 2. +=======+===================+===========+ | Value | Description | Reference | +=======+===================+===========+ | 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 Flag) | [RFC9089] | +-------+-------------------+-----------+ | 0x80 | AC-bit | [RFC9513] | +-------+-------------------+-----------+ Table 2: OSPFv3 Prefix Options (8 bits) This document solves the problem of insufficient existing flags, and defines the variable length Prefix Attribute Flags Sub-TLVs for OSPFv2 and OSPFv3 respectively for the extended flag fields. Chen, et al. Expires 12 April 2025 [Page 3] Internet-Draft Prefix Flag Extension for OSPF October 2024 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 Attribute Flags Sub-TLVs This document creates the variable length Prefix Attribute Flags Sub- TLVs for OSPFv2 and OSPFv3 respectively. These Sub-TLVs specifie the variable flag fields to advertise additional attributes associated with the prefix. 2.1. OSPFv2 Prefix Attribute Flags Sub-TLV The format of OSPFv2 Prefix Attribute Flags 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Prefix Attribute Flags(Variable) // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Type: TBD1. 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, no bits are defined in this document. 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. Chen, et al. Expires 12 April 2025 [Page 4] Internet-Draft Prefix Flag Extension for OSPF October 2024 OSPFv2 Prefix Attribute Flags Sub-TLV is a sub-TLV of the OSPFv2 Extended Prefix TLV as defined in [RFC7684]. 2.2. OSPFv3 Prefix Attribute Flags Sub-TLV The format of OSPFv3 Prefix Attribute Flags 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Prefix Attribute Flags(Variable) // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Type: TBD2. 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, no bits are defined in this document. 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. OSPFv3 Prefix Attribute Flags Sub-TLV is a sub-TLV of the following OSPFv3 TLVs as defined in [RFC8362]: * Intra-Area-Prefix TLV * Inter-Area-Prefix TLV * External-Prefix TLV Chen, et al. Expires 12 April 2025 [Page 5] Internet-Draft Prefix Flag Extension for OSPF October 2024 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 Attribute Flags Sub-TLV. If a device receives the Prefix Attribute Flags Sub-TLV of a length more than it currently supports or understands, it MUST ignore the bits beyond that length. If a device receives the Prefix Attribute Flags 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. An OSPFv2 router receiving multiple OSPFv2 Prefix Attribute Flags Sub-TLVs in the same OSPFv2 Extended Prefix TLV MUST select the first advertisement of this sub-TLV and MUST ignore all remaining occurrences of this sub-TLV in the OSPFv2 Extended Prefix TLV. An OSPFv3 router receiving multiple OSPFv3 Prefix Attribute Flags Sub-TLVs in the the same parent TLV MUST select the first advertisement of this sub-TLV and MUST ignore all remaining occurrences of this sub-TLV in the parent TLV. 4. Backward Compatibility The Prefix Attribute Flags Sub-TLV defined in this document does not introduce any backward compatibility issues. An implementation that does not understand or support the Prefix Attribute Flags Sub-TLV MUST ignore the TLV. Further, any additional bits in the OSPFv2/OSPFv3 Prefix Attribute Flags Sub-TLV that are not understood by an implementation MUST be ignored. 5. Acknowledgements The authors thank Shraddha Hegde and Changwang Lin and many others for their suggestions and comments. Chen, et al. Expires 12 April 2025 [Page 6] Internet-Draft Prefix Flag Extension for OSPF October 2024 6. IANA Considerations This document requests allocation for the following registry. 6.1. OSPFv2 Prefix Attribute Flags Sub-TLV Registry This document requests the allocation of "OSPFv2 Prefix Attribute Flags" in the "OSPFv2 Extended Prefix TLV Sub-TLVs" registry: The following flag (TEMPORARY - registered 2024-04-05, expires 2025-04-05) has been allocated by IANA: Value Description Reference ------ ---------------------------------- -------------- 11 OSPFv2 Prefix Attribute Flags This document 6.1.1. OSPFv2 Prefix Extended Flags Field Registry This document requests an allocation of "OSPFv2 Prefix Extended Flag Field" Registry under "Open Shortest Path First v2 (OSPFv2) Parameters". The new registry defines the bits in the 32-bit Flags field in the OSPFv2 Prefix Attribute Flags Sub-TLV. New bits can be allocated via IETF Review or IESG Approval [RFC8126]. 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. 6.2. OSPFv3 Prefix Attribute Flags Sub-TLV Registry This document requests the allocation of "OSPFv3 Prefix Attribute Flags" in the "OSPFv3 Extended-LSA Sub-TLVs" registry: The following flag (TEMPORARY - registered 2024-04-05, expires 2025-04-05) has been allocated by IANA: Value Description Reference ------ ---------------------------------- -------------- 37 OSPFv3 Prefix Attribute Flags This document Chen, et al. Expires 12 April 2025 [Page 7] Internet-Draft Prefix Flag Extension for OSPF October 2024 6.2.1. OSPFv3 Prefix Extended Flags Field Registry This document requests an allocation of "OSPFv3 Prefix Extended Flag Field" registry under "Open Shortest Path First v3 (OSPFv3) Parameters". New bits can be allocated via IETF Review or IESG Approval [RFC8126]. 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. References 8.1. 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, . [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, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . Chen, et al. Expires 12 April 2025 [Page 8] Internet-Draft Prefix Flag Extension for OSPF October 2024 [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, . 8.2. Informative References [I-D.ietf-lsr-igp-ureach-prefix-announce] Psenak, P., Filsfils, C., Litkowski, S., Voyer, D., Dhamija, 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- 02, 22 April 2024, . [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, . [RFC9513] Li, Z., Hu, Z., Talaulikar, K., Ed., and P. Psenak, "OSPFv3 Extensions for Segment Routing over IPv6 (SRv6)", RFC 9513, DOI 10.17487/RFC9513, December 2023, . Authors' Addresses Ran Chen ZTE Corporation Nanjing China Email: chen.ran@zte.com.cn Detao Zhao ZTE Corporation Nanjing China Email: zhao.detao@zte.com.cn Chen, et al. Expires 12 April 2025 [Page 9] Internet-Draft Prefix Flag Extension for OSPF October 2024 Peter Psenak Cisco Systems Slovakia Email: ppsenak@cisco.com Ketan Talaulikar Cisco Systems India Email: ketant.ietf@gmail.com Liyan Gong China mobile China Email: gongliyan@chinamobile.com Chen, et al. Expires 12 April 2025 [Page 10]