Internet DRAFT - draft-chen-lsr-prefix-extended-flags
draft-chen-lsr-prefix-extended-flags
LSR R. Chen
Internet-Draft D. Zhao
Intended status: Standards Track ZTE Corporation
Expires: 8 May 2024 P. Psenak
K. Talaulikar
Cisco Systems
5 November 2023
Prefix Flag Extension for OSPFv2 and OSPFv3
draft-chen-lsr-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 attributes 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.
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This Internet-Draft will expire on 8 May 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Variable length Prefix attributes Sub-TLVs . . . . . . . . . 4
2.1. OSPFv2 Prefix Attributes Sub-TLV . . . . . . . . . . . . 4
2.2. OSPFv3 Prefix Attributes Sub-TLV . . . . . . . . . . . . 5
3. Processing . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Backward Compatibility . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. OSPFv2 Prefix Attributes Sub-TLV Registry . . . . . . . . 6
6.1.1. OSPFv2 Prefix Extended Flags Field Registry . . . . . 7
6.2. OSPFv3 Prefix Attributes Sub-TLV Registry . . . . . . . . 7
6.2.1. OSPFv3 Prefix Extended Flags Field Registry . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . 8
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 only two 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] |
+-------+-------------+-------------------------------------------+
| TBD | AC | [I-D.chen-lsr-anycast-flag] |
+-------+-------------+-------------------------------------------+
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 | [RFC9089] |
| | Flag) | |
+-------+-------------------+---------------------------------------+
| 0x80 | AC-bit | [I-D.ietf-lsr-ospfv3-srv6-extensions] |
+-------+-------------------+---------------------------------------+
Table 2: OSPFv3 Prefix Options (8 bits)
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This document solves the problem of insufficient existing flags, and
defines the variable length Prefix attributes Sub-TLVs for OSPFv2 and
OSPFv3 respectively for the extended flag fields.
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-TLVs
This document creates the variable length Prefix attributes 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 Attributes Sub-TLV
The format of OSPFv2 Prefix Attributes 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.
Unassigned bits MUST be set to zero on transmission and MUST be
ignored on receipt.
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Bits that are NOT transmitted MUST be treated as if they are set to 0
on receipt.
OSPFv2 Prefix Attributes Sub-TLV is a sub-TLV of the OSPFv2 Extended
Prefix TLV as defined in [RFC7684].
2.2. OSPFv3 Prefix Attributes Sub-TLV
The format of OSPFv3 Prefix Attributes 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, two new bits (U-Flag and UP-Flag) are defined as described
in [I-D.ietf-lsr-igp-ureach-prefix-announce].
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 Attributes 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
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.
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 Prefix Attributes Sub-TLV Registry
This document requests the allocation of "OSPFv2 Prefix Attributes"
in the "OSPFv2 Extended Prefix TLV Sub-TLVs" registry:
Value Description Reference
------ ---------------------------------- --------------
TBD1 OSPFv2 Prefix Attributes This document
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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 Attributes 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 Attributes Sub-TLV Registry
This document requests the allocation of "OSPFv3 Prefix Attributes"
in the "OSPFv3 Extended-LSA Sub-TLVs" registry:
Value Description Reference
------ ---------------------------------- --------------
TBD2 OSPFv3 Prefix Attributes This document
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.
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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>.
[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
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[I-D.chen-lsr-anycast-flag]
Chen, R., Zhao, D., Psenak, P., and K. Talaulikar,
"Updates to Anycast Property advertisement for OSPFv2",
Work in Progress, Internet-Draft, draft-chen-lsr-anycast-
flag-04, 23 July 2023,
<https://datatracker.ietf.org/doc/html/draft-chen-lsr-
anycast-flag-04>.
[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-
01, 22 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-lsr-igp-
ureach-prefix-announce-01>.
[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>.
[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
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
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