[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits] [IPR]
Versions: (draft-wang-lsr-ospf-prefix-originator-ext)
00 01 02 03 04 05 06 07
LSR Working Group A. Wang
Internet-Draft China Telecom
Intended status: Standards Track A. Lindem
Expires: April 23, 2021 Cisco Systems
J. Dong
Huawei Technologies
P. Psenak
K. Talaulikar
Cisco Systems
October 20, 2020
OSPF Prefix Originator Extensions
draft-ietf-lsr-ospf-prefix-originator-07
Abstract
This document defines OSPF extensions to include information
associated with the node originating a prefix along with the prefix
advertisement.
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
working documents as Internet-Drafts. The list of current Internet-
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 April 23, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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
Wang, et al. Expires April 23, 2021 [Page 1]
Internet-Draft OSPF Prefix Originator Extensions October 2020
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 3
2.1. Prefix Source Router-ID Sub-TLV . . . . . . . . . . . . . 3
2.2. Prefix Originator Sub-TLV . . . . . . . . . . . . . . . . 4
3. Elements of Procedure . . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Prefix attributes are advertised in OSPFv2 [RFC2328] using the
Extended Prefix Opaque Link State Advertisement (LSA) [RFC7684] and
in OSPFv3 [RFC5340] using the various Extended Prefix LSA types
[RFC8362].
The identification of the originating router for a prefix in OSPF
varies by the type of the prefix and is currently not always
possible. For intra-area prefixes, the originating router is
identified by the advertising Router ID field of the area-scoped LSA
used for those prefix advertisements. However, for the inter-area
prefixes advertised by the Area Border Router (ABR), the advertising
Router ID field of their area-scoped LSAs is set to the ABR itself
and the information about the router originating the prefix
advertisement is lost in this process of prefix propagation across
areas. For Autonomous System (AS) external prefixes, the originating
router may be considered as the Autonomous System Border Router
(ASBR) and is identified by the advertising Router ID field of the
AS-scoped LSA used. However, the actual originating router for the
prefix may be a remote router outside the OSPF domain. Similarly,
when an ABR performs translation of Not-So-Stubby Area (NSSA)
[RFC3101] LSAs to AS-external LSAs, the information associated with
the NSSA ASBR (or the router outside the OSPF domain) is not conveyed
across the OSPF domain.
Wang, et al. Expires April 23, 2021 [Page 2]
Internet-Draft OSPF Prefix Originator Extensions October 2020
While typically the originator of information in OSPF is identified
by its OSPF Router ID, it does not necessarily represent a reachable
address for the router. The IPv4/IPv6 Router Address as defined in
[RFC3630] and [RFC5329] for OSPFv2 and OSPFv3 respectively provide an
address to reach that router.
The primary use case for the extensions proposed in this document is
to be able to identify the originator of the prefix in the network.
In cases where multiple prefixes are advertised by a given router, it
is also useful to be able to associate all these prefixes with a
single router even when prefixes are advertised outside of the area
in which they originated. It also helps to determine when the same
prefix is being originated by multiple routers across areas.
This document proposes extensions to the OSPF protocol for inclusion
of information associated with the router originating the prefix
along with the prefix advertisement. These extensions do not change
the core OSPF route computation functionality. They provide useful
information for topology analysis and traffic engineering, especially
on a controller when this information is advertised as an attribute
of the prefixes via mechanisms such as Border Gateway Protocol Link-
State (BGP-LS) [RFC7752].
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. Protocol Extensions
This document defines the Prefix Source Router-ID and the Prefix
Originator Sub-TLVs for inclusion of the Router ID and a reachable
address information for the router originating the prefix as a prefix
attribute.
2.1. Prefix Source Router-ID Sub-TLV
For OSPFv2, the Prefix Source Router-ID Sub-TLV is an optional Sub-
TLV of the OSPFv2 Extended Prefix TLV [RFC7684]. For OSPFv3, the
Prefix Source Router-ID Sub-TLV is an optional Sub-TLV of the Intra-
Area-Prefix TLV, Inter-Area-Prefix TLV, and External-Prefix TLV
[RFC8362] when originating either an IPv4 [RFC5838] or an IPv6 prefix
advertisement.
The Prefix Source Router-ID Sub-TLV has the following format:
Wang, et al. Expires April 23, 2021 [Page 3]
Internet-Draft OSPF Prefix Originator Extensions October 2020
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OSPF Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Prefix Source Router-ID Sub-TLV Format
Where:
o Type: 4 for OSPFv2 and 27 for OSPFv3
o Length: 4
o OSPF Router ID : the OSPF Router ID of the OSPF router that
originated the prefix advertisement in the OSPF domain.
A prefix advertisement MAY include more than one Prefix Source
Router-ID sub-TLV, one corresponding to each of the Equal-Cost Multi-
Path (ECMP) nodes that originated the given prefix.
A received Prefix Source Router-ID Sub-TLV with OSPF Router ID set to
0 MUST be considered invalid and ignored. Additionally, reception of
such Sub-TLV SHOULD be logged as an error (subject to rate-limiting).
2.2. Prefix Originator Sub-TLV
For OSPFv2, the Prefix Originator Sub-TLV is an optional Sub-TLV of
the OSPFv2 Extended Prefix TLV [RFC7684]. For OSPFv3, the Prefix
Originator Sub-TLV is an optional Sub-TLV of the Intra-Area-Prefix
TLV, Inter-Area-Prefix TLV, and External-Prefix TLV [RFC8362] when
originating either an IPv4 [RFC5838] or an IPv6 prefix advertisement.
The Prefix Originator Sub-TLV has the following format:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Prefix Originator Sub-TLV Format
Where:
Wang, et al. Expires April 23, 2021 [Page 4]
Internet-Draft OSPF Prefix Originator Extensions October 2020
o Type: TBD1 for OSPFv2 and TBD2 for OSPFv3
o Length: 4 or 16
o Router Address: A reachable IPv4 or IPv6 router address for the
router that originated the IPv4 or IPv6 prefix advertisement.
Such an address would be semantically equivalent to what may be
advertised in the OSPFv2 Router Address TLV [RFC3630] or in the
OSPFv3 Router IPv6 Address TLV [RFC5329].
A prefix advertisement MAY include more than one Prefix Originator
sub-TLV, one corresponding to each of the Equal-Cost Multi-Path
(ECMP) nodes that originated the given prefix.
A received Prefix Originator Sub-TLV that has an invalid length (not
4 or 16) or a Router Address containing an invalid IPv4 or IPv6
address (dependent on address family of the associated prefix) MUST
be considered invalid and ignored. Additionally, reception of such
Sub-TLV SHOULD be logged as an error (subject to rate-limiting).
[RFC7794] provides similar functionality for the Intermediate System
to Intermediate System (IS-IS) protocol.
3. Elements of Procedure
This section describes the procedure for advertisement of the Prefix
Source Router-ID and Prefix Originator Sub-TLVs along with the prefix
advertisement.
The OSPF Router ID of the Prefix Source Router-ID is set to the OSPF
Router ID of the node originating the prefix in the OSPF domain.
If the originating node is advertising an OSPFv2 Router Address TLV
[RFC3630] or an OSPFv3 Router IPv6 Address TLV [RFC5329], then that
value is set in the Router Address field of the Prefix Originator
Sub-TLV. When the originating node is not advertising such an
address, implementations MAY support mechanisms to determine a
reachable address (e.g., advertised with the N-flag set [RFC7684] or
N-bit set [RFC8362] and either matching the OSPF Router ID or the
highest IP address) belonging to the originating node to set in the
Router Address field.
Implementations MAY support the selection of specific prefixes for
which the originating node information needs to be included with
their prefix advertisements.
When an ABR generates inter-area prefix advertisements into its non-
backbone areas corresponding to an inter-area prefix advertisement
Wang, et al. Expires April 23, 2021 [Page 5]
Internet-Draft OSPF Prefix Originator Extensions October 2020
from the backbone area, the only way to determine the originating
node information is based on the Prefix Source Router-ID and Prefix
Originator Sub-TLVs present in the inter-area prefix advertisement
originated into the backbone area by an ABR for another non-backbone
area. The ABR performs its prefix calculation to determine the set
of nodes that contribute to the best prefix reachability. It MUST
use the prefix originator information only from this set of nodes.
The ABR MUST NOT include the Prefix Source Router-ID or the Prefix
Originator Sub-TLVs when it is unable to determine the information of
the best originating node.
Implementations MAY provide control on ABRs to selectively disable
the propagation of the originating node information across area
boundaries.
Implementations MAY support the propagation of the originating node
information along with a redistributed prefix into the OSPF domain
from another routing domain. The details of such mechanisms are
outside the scope of this document. Such implementations MAY also
provide control on whether the Router Address in the Prefix
Originator Sub-TLV is set as the ABSR node address or as the address
of the actual node outside the OSPF domain that owns the prefix.
When translating the NSSA prefix advertisements [RFC3101] to the AS
external prefix advertisements, the NSSA ABR, follows the same
procedures as an ABR generating inter-area prefix advertisements for
the propagation of the originating node information.
4. Security Considerations
Since this document extends the OSPFv2 Extended Prefix LSA, the
security considerations for [RFC7684] are applicable. Similarly,
since this document extends the OSPFv3 E-Intra-Area-Prefix-LSA, E-
Inter-Area-Prefix-LSA, E-AS-External LSA and E-NSSA-LSA, the security
considerations for [RFC8362] are applicable.
5. IANA Considerations
This document requests IANA for the allocation of the codepoint from
the "OSPFv2 Extended Prefix TLV Sub-TLVs" registry under the "Open
Shortest Path First v2 (OSPFv2) Parameters" registry.
Wang, et al. Expires April 23, 2021 [Page 6]
Internet-Draft OSPF Prefix Originator Extensions October 2020
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Description | IANA Allocation |
| Point | | Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 4 | Prefix Source Router-ID Sub-TLV | early allocation done |
| TBD1 | Prefix Originator Sub-TLV | pending |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Code Points in OSPFv2 Extended Prefix TLV Sub-TLVs
This document requests IANA for the allocation of the codepoint from
the "OSPFv3 Extended Prefix TLV Sub-TLVs" registry under the "Open
Shortest Path First v3 (OSPFv3) Parameters" registry.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Code | Description | IANA Allocation |
| Point | | Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 27 | Prefix Source Router-ID Sub-TLV | early allocation done |
| TBD2 | Prefix Originator Sub-TLV | pending |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Code Points in OSPFv3 Extended-LSA Sub-TLVs
6. Acknowledgement
Many thanks to Les Ginsberg for his suggestions on this draft. Also
thanks to Jeff Tantsura, Rob Shakir, Gunter Van De Velde, Goethals
Dirk, Smita Selot, Shaofu Peng, John E Drake and Baalajee S for their
review and valuable comments.
7. References
7.1. 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>.
Wang, et al. Expires April 23, 2021 [Page 7]
Internet-Draft OSPF Prefix Originator Extensions October 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>.
[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>.
[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <https://www.rfc-editor.org/info/rfc7794>.
[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>.
7.2. Informative References
[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>.
[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
"Traffic Engineering Extensions to OSPF Version 3",
RFC 5329, DOI 10.17487/RFC5329, September 2008,
<https://www.rfc-editor.org/info/rfc5329>.
[RFC5838] Lindem, A., Ed., Mirtorabi, S., Roy, A., Barnes, M., and
R. Aggarwal, "Support of Address Families in OSPFv3",
RFC 5838, DOI 10.17487/RFC5838, April 2010,
<https://www.rfc-editor.org/info/rfc5838>.
Wang, et al. Expires April 23, 2021 [Page 8]
Internet-Draft OSPF Prefix Originator Extensions October 2020
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
Authors' Addresses
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing 102209
China
Email: wangaj3@chinatelecom.cn
Acee Lindem
Cisco Systems
301 Midenhall Way
Cary, NC 27513
USA
Email: acee@cisco.com
Jie Dong
Huawei Technologies
Beijing
China
Email: jie.dong@huawei.com
Peter Psenak
Cisco Systems
Pribinova Street 10
Bratislava, Eurovea Centre, Central 3 81109
Slovakia
Email: ppsenak@cisco.com
Ketan Talaulikar
Cisco Systems
India
Email: ketant@cisco.com
Wang, et al. Expires April 23, 2021 [Page 9]
Html markup produced by rfcmarkup 1.129d, available from
https://tools.ietf.org/tools/rfcmarkup/