Internet DRAFT - draft-acee-lsr-ospf-admin-tags
draft-acee-lsr-ospf-admin-tags
Network Working Group A. Lindem, Ed.
Internet-Draft P. Psenak
Intended status: Standards Track Cisco Systems
Expires: March 27, 2021 September 23, 2020
Extensions to OSPF for Advertising Prefix Administrative Tags
draft-acee-lsr-ospf-admin-tags-07
Abstract
It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be
able to associate tags with prefixes. Previously, OSPFv2 and OSPFv3
were relegated to a single tag for AS External and Not-So-Stubby-Area
(NSSA) prefixes. With the flexible encodings provided by OSPFv2
Prefix/Link Attribute Advertisement and OSPFv3 Extended LSAs,
multiple administrative tags may advertised for all types of
prefixes. These administrative tags can be used for many
applications including route redistribution policy, selective prefix
prioritization, selective IP Fast-ReRoute (IPFRR) prefix protection,
and many others.
The ISIS protocol supports a similar mechanism that is described in
RFC 5130.
Status of This Memo
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This Internet-Draft will expire on March 27, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. 32-Bit Administrative Tag Sub-TLV . . . . . . . . . . . . . . 3
3. Administrative Tag Applicability . . . . . . . . . . . . . . 4
4. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 5
4.1. Equal-Cost Multipath Applicability . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Appendix A. 64-Bit Administrative Tag Sub-TLV . . . . . . . . . 8
Appendix B. Link Administrative Tags . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
It is useful for routers in an OSPFv2 [RFC2328] or OSPFv3 [RFC5340]
routing domain to be able to associate tags with prefixes.
Previously, OSPFv3 and OSPFv3 were relegated to a single tag for AS
External and Not-So-Stubby-Area (NSSA) prefixes. With the flexible
encodings provided by OSPFv2 Prefix/Link Attribute Advertisement
([RFC7684]) and OSPFv3 Extended LSA ([RFC8362]), multiple
administrative tags may be advertised for all types of prefixes.
These administrative tags can be used many applications including
(but not limited to):
1. Controlling which routes are redistributed into other protocols
for readvertisement.
2. Prioritizing selected prefixes for faster convergence and
installation in the forwarding plane.
3. Identifying selected prefixes for Loop-Free Alternative (LFA)
protection.
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Throughout this document, OSPF is used when the text applies to both
OSPFv2 and OSPFv3. OSPFv2 or OSPFv3 is used when the text is
specific to one version of the OSPF protocol.
The ISIS protocol supports a similar mechanism that is described in
RFC 5130 [RFC5130].
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. 32-Bit Administrative Tag Sub-TLV
This document creates a new Administrative Tag Sub-TLV for OSPFv2 and
OSPFv3. This Sub-TLV specifies one or more 32-bit unsigned integers
that may be associated with an OSPF advertised prefix. The precise
usage of these tags is beyond the scope of this document.
The format of this Sub-TLV is the same as the format used by the
Traffic Engineering Extensions to OSPF [RFC3630]. The LSA payload
consists of one or more nested Type/Length/Value (TLV) triplets. 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TLV Format
The Length field defines the length of the value portion in octets
(thus a TLV with no value portion would have a length of 0). The TLV
is padded to 4-octet alignment; padding is not included in the length
field (so a 3-octet value would have a length of 3, but the total
size of the TLV would be 8 octets).
The format of the 32-bit Administrative Tag TLV is as follows:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First 32-bit Administrative Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o |
o
| o |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last 32-bit Administrative Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type A 16-bit field set to TBD. The value MAY be different
depending upon the IANA registry from which it is
allocated.
Length A 16-bit field that indicates the length of the value
portion in octets and will be a multiple of 4 octets
dependent on the number of administrative tags
advertised. If the sub-TLV is specified, at least one
administrative tag must be advertised.
Value A variable length list of one or more administrative
tags.
32-bit Administrative Tag Sub-TLV
This sub-TLV will carry one or more 32-bit unsigned integer values
that will be used as administrative tags.
3. Administrative Tag Applicability
The administrative tag TLV specified herein will be valid as a sub-
TLV of the following TLVs specified in [RFC7684]:
1. Extended Prefix TLV advertised in the OSPFv2 Extended Prefix LSA
The administrative tag TLV specified herein will be valid as a sub-
TLV of the following TLVs specified in [RFC8362]:
1. Inter-Area-Prefix TLV advertised in the E-Inter-Area-Prefix-LSA
2. Intra-Area-Prefix TLV advertised in the E-Link-LSA and the E-
Intra-Area-Prefix-LSA
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3. External-Prefix TLV advertised in the E-AS-External-LSA and the
E-NSSA-LSA
4. Protocol Operation
An OSPF router supporting this specification MUST propagate
administrative tags when acting as an Area Border Router and
originating summary advertisements into other areas. Similarly, an
OSPF router supporting this specification and acting as an ABR for a
Not-So-Stubby Area (NSSA) MUST propagate tags when translating NSSA
routes to AS External advertisements [RFC3101]. The number of tags
supported MAY limit the number of tags that are propagated. When
propagating multiple tags, the order of the the tags must be
preserved.
For configured area ranges, NSSA ranges, and configurated
summarization of redistributed routes, tags from component routes
SHOULD NOT be propagated to the summary. Implementations SHOULD
provide a mechanism to configure tags for area ranges, NSSA ranges,
and redistributed route summaries.
An OSPF router supporting this specification MUST be able to
advertise and interpret one 32-bit tag for prefixes. An OSPF router
supporting this specification MAY be able to advertise and propagate
multiple 32-bit tags. The maximum tags that an implementation
supports is a local matter depending upon supported applications
using the prefix or link tags.
When a single tag is advertised for AS External or NSSA LSA prefix,
the existing tag in OSPFv2 and OSPFv3 AS-External-LSA and NSSA-LSA
encodings SHOULD be utilized. This will facilitate backward
compatibilty with implementations that do not support this
specification.
4.1. Equal-Cost Multipath Applicability
When multiple LSAs contribute to an OSPF route, it is possible that
these LSAs will all have different tags. In this situation, the OSPF
router MUST associate the tags from one of the LSAs contributing a
path and, if the implementation supports multiple tags, MAY associate
tags for multiple contributing LSAs up to the maximum number of tags
supported.
5. Security Considerations
This document describes a generic mechanism for advertising
administrative tags for OSPF prefixes. The administrative tags are
generally less critical than the topology information currently
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advertised by the base OSPF protocol. The security considerations
for the generic mechanism are dependent on the future application
and, as such, should be described as additional capabilities are
proposed for advertisement. Security considerations for the base
OSPF protocol are covered in [RFC2328] and [RFC5340].
6. IANA Considerations
The following values should be allocated from the OSPF Extended
Prefix TLV Sub-TLV Registry [RFC7684]:
o TBD - 32-bit Administrative Tag TLV
The following values should be allocated from the OSPFv3 Extended-LSA
Sub-TLV Registry [RFC8362]:
o TBD - 32-bit Administrative Tag TLV
7. Acknowledgments
The authors of RFC 5130 are acknowledged since this document draws
upon both the ISIS specification and deployment experience.
Thanks to Donnie Savage for his comments and questions.
The RFC text was produced using Marshall Rose's xml2rfc tool.
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>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.
[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>.
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[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>.
8.2. Informative References
[I-D.ietf-ospf-te-link-attr-reuse]
Psenak, P., Ginsberg, L., Henderickx, W., Tantsura, J.,
and J. Drake, "OSPF Application-Specific Link Attributes",
draft-ietf-ospf-te-link-attr-reuse-16 (work in progress),
June 2020.
[RFC3101] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, DOI 10.17487/RFC3101, January 2003,
<https://www.rfc-editor.org/info/rfc3101>.
[RFC5130] Previdi, S., Shand, M., Ed., and C. Martin, "A Policy
Control Mechanism in IS-IS Using Administrative Tags",
RFC 5130, DOI 10.17487/RFC5130, February 2008,
<https://www.rfc-editor.org/info/rfc5130>.
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Appendix A. 64-Bit Administrative Tag Sub-TLV
The definition of the 64-bit tag was considered but discard given
that there is no strong requirement or use case. The specification
is included here for information.
This sub-TLV will carry one or more 64-bit unsigned integer values
that will be used as administrative tags.
The format of the 64-bit Administrative Tag TLV is as follows:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First 64-bit Administrative Tag |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| O |
o
| o |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Last 64-bit Administrative Tag |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type A 16-bit field set to TBD. The value MAY be different
depending upon the registry from which it is allocated.
Length A 16-bit field that indicates the length of the value
portion in octets and will be a multiple of 8 octets
dependent on the number of administrative tags
advertised. If the sub-TLV is specified, at least one
administrative tag must be advertised.
Value A variable length list of one or more 64-bit
administrative tags.
64-bit Administrative Tag TLV
Appendix B. Link Administrative Tags
The advertisement of administrative tags corresponding to links has
been removed from the document. The specification of advertising
link administrative groups as specified in
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[I-D.ietf-ospf-te-link-attr-reuse] advertising administrative tags
for links.
Authors' Addresses
Acee Lindem (editor)
Cisco Systems
301 Midenhall Way
Cary, NC 27513
USA
EMail: acee@cisco.com
Peter Psenak
Cisco Systems
Apollo Business Center
Mlynske nivy 43
Bratislava, 821 09
Slovakia
EMail: ppsenak@cisco.com
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