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Prefix Flag Extension for OSPFv2 and OSPFv3
draft-ietf-lsr-ospf-prefix-extended-flags-03

Document Type Active Internet-Draft (lsr WG)
Authors Ran Chen , Detao Zhao , Peter Psenak , Ketan Talaulikar , Liyan Gong
Last updated 2024-10-09
Replaces draft-chen-lsr-prefix-extended-flags
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draft-ietf-lsr-ospf-prefix-extended-flags-03
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.

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   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.

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    +=======+=============+===========================================+
    | 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.

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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.

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   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

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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.

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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

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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,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
              <https://www.rfc-editor.org/info/rfc5340>.

   [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, <https://www.rfc-editor.org/info/rfc7684>.

   [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,
              <https://www.rfc-editor.org/info/rfc8126>.

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   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [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, <https://www.rfc-editor.org/info/rfc8362>.

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, <https://datatracker.ietf.org/doc/html/
              draft-ietf-lsr-igp-ureach-prefix-announce-02>.

   [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,
              <https://www.rfc-editor.org/info/rfc9089>.

   [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,
              <https://www.rfc-editor.org/info/rfc9513>.

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

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   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

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