Network Working Group A. Lindem, Ed.
Internet-Draft P. Psenak
Intended status: Standards Track Cisco Systems
Expires: March 6, 2015 September 2, 2014
Extensions to OSPF for Advertising Prefix/Link Administrative Tags
draft-acee-ospf-admin-tags-00.txt
Abstract
It is useful for routers in an OSPFv2 or OSPFv3 routing domain to be
able to associate tags with prefixes and links. 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
and links. 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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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3
1.2. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 3
2. Administrative Tag Sub-TLVs . . . . . . . . . . . . . . . . . 4
2.1. 32-Bit Administrative Tag Sub-TLV . . . . . . . . . . . . 4
2.2. 64-Bit Administrative Tag Sub-TLV . . . . . . . . . . . . 5
3. Administrative Tag Applicability . . . . . . . . . . . . . . . 7
4. Protocol Operation . . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
7.1. Normative References . . . . . . . . . . . . . . . . . . . 11
7.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
It is useful for routers in an OSPFv2 [OSPF] or OSPFv3 [OSPF] routing
domain to be able to associate tags with prefixes and links.
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
([OSPFV2-PREFIX-LINK]) and OSPFv3 Extended LSA
([OSPFV3-EXTENDED-LSA]), multiple administrative tags may be
advertised for all types of prefixes and links. 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 place.
3. Identifying selected prefixes for Loop-Free Alternative (LFA)
protection.
The ISIS protocol supports a similar mechanism that is described in
RFC 5130 [ISIS-ADMIN-TAGS].
1.1. Requirements notation
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-KEYWORDS].
1.2. Acknowledgments
The authors of RFC 5130 are acknowledged since this document draws
upon both the ISIS specification and deployment experience.
The RFC text was produced using Marshall Rose's xml2rfc tool.
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2. Administrative Tag Sub-TLVs
This document creates two new Administrative Tag sub-TLVs for OSPFv2
and two for OSPFv3. These TLVs specify one or more 32-bit or 64-bit
unsigned integers that may be associated with an OSPF advertised
prefix or OSPF Link. The precise usage of these tags is beyond the
scope of this document.
The format of these TLVs is the same as the format used by the
Traffic Engineering Extensions to OSPF [TE]. 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).
2.1. 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.
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 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 TLV
2.2. 64-Bit Administrative Tag Sub-TLV
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:
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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 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
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3. Administrative Tag Applicability
The administrative tag TLVs specified herein will be valid as sub-
TLVs of the following TLVs specified in [OSPFV2-PREFIX-LINK]:
1. Extended Prefix TLV advertised in the OSPFv2 Extended Prefix LSA
2. Extended Link TLV advertised in the OSPFv2 Extended Prefix LSA
The administrative tag TLVs specified herein will be valid as sub-
TLVs of the following TLVs specified in [OSPFV3-EXTENDED-LSA]:
1. Router-Link TLV advertised in the E-Router-LSA
2. Inter-Area-Prefix TLV advertised in the E-Inter-Area-Prefix-LSA
3. Intra-Area-Prefix TLV advertised in the E-Link-LSA and the
E-Intra-Area-LSA
4. External-Prefix TLV advertised in the E-AS-External-LSA and the
E-NSSA-LSA
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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 [NSSA]. The number of tags
supported MAY limit the number of tags that are propagated.
An OSPF router supporting this specification MUST be able to
advertise and interpret one 32-bit tag for prefixes and links. An
OSPF router supporting this specification SHOULD be able to advertise
and interpret one 64-bit tag for prefixes and links. An OSPF router
supporting this specification MAY be able to advertise and propagate
multiple 32-bit and 64-bit tags. The maximum tags that an
implementation supports is a local matter depending upon supported
tag applications.
When a single tag is advertised for AS External or NSSA LSA prefix,
the existing tag encoding SHOULD be utilized.
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5. Security Considerations
This document describes both a generic mechanism for advertising
administrative tags for OSPF prefixes and links. The administrative
tags are generally less critical than the topology information
currently 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 [OSPF] and [OSPFV3].
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6. IANA Considerations
The following values should be allocated from the OSPF Extended
Prefix TLV Sub-TLV Registry [OSPFV2-PREFIX-LINK]:
o TBD - 32-bit Administrative Tag TLV
o TBD - 64-bit Administrative Tag TLV
The following values should be allocated from the OSPF Extended Link
TLV Sub-TLV Registry [OSPFV2-PREFIX-LINK]:
o TBD - 32-bit Administrative Tag TLV
o TBD - 64-bit Administrative Tag TLV
The following values should be allocated from the OSPFv3 Extended-LSA
Sub-TLV Registry [OSPFV3-EXTENDED-LSA]:
o TBD - 32-bit Administrative Tag TLV
o TBD - 64-bit Administrative Tag TLV
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7. References
7.1. Normative References
[OSPF] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[OSPFV2-PREFIX-LINK]
Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", draft-ietf-ospf-prefix-link-attr-00.txt
(work in progress).
[OSPFV3] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
[OSPFV3-EXTENDED-LSA]
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
LSA Extendibility",
draft-ietf-ospf-ospfv3-lsa-extend-02.txt (work in
progress).
[RFC-KEYWORDS]
Bradner, S., "Key words for use in RFC's to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[TE] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
Extensions to OSPF", RFC 3630, September 2003.
7.2. Informative References
[ISIS-ADMIN-TAGS]
Previdi, S., Shand, M., and C. Martin, "A Policy Control
Mechanism in IS-IS Using Administrative Tags", RFC 5130,
February 2008.
[NSSA] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, January 2003.
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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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