LSR R. Chen
Internet-Draft D. Zhao
Intended status: Standards Track ZTE Corporation
Expires: 1 January 2024 P. Psenak
K. Talaulikar
Cisco Systems
30 June 2023
Prefix Flag Extension for OSPFv2 and OSPFv3
draft-chen-lsr-prefix-extended-flags-00
Abstract
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 PrefixOptions 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.
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and may be updated, replaced, or obsoleted by other documents at any
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This Internet-Draft will expire on 1 January 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/
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Please review these documents carefully, as they describe your rights
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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 . . . . . . . . . . 5
6.2.1. OSPFv3 Prefix Extended Flags Field . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. Normative 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 PrefixOptions 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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Attributes(Variable) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Figure 1
where:
Type: TBA.
Length: Variable, dependent on the included attributes.
Attributes: 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 assigned. Unassigned bits MUST be
set to zero on transmission and MUST be ignored 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.
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.
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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
------ ---------------------------------- --------------
TBA OSPFv2 Prefix attributes Sub-TLV This document
Figure 2
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.
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 Extended LSA Sub-TLV Registry
This document requests allocation for OSPFv3 Extended LSA Sub-TLV
Registry:
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Value Description Reference
------ ---------------------------------- --------------
TBA OSPFv3 Prefix attributes Sub-TLV This document
Figure 3
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.
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.
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. Normative References
[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>.
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[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
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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