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
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   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.





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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 . . . . . . . . . . . . . . . . . .   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.












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   +=======+===================+=======================================+
   | 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)            //
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



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   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.



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   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.




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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,
              <https://datatracker.ietf.org/doc/html/draft-ietf-lsr-igp-
              ureach-prefix-announce-00>.






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   [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,
              <https://datatracker.ietf.org/doc/html/draft-ietf-lsr-
              ospfv3-srv6-extensions-15>.

   [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>.

   [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>.

   [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>.

Authors' Addresses

   Ran Chen
   ZTE Corporation
   Nanjing
   China
   Email: chen.ran@zte.com.cn








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   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


































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