Open Shortest Path First IGP P. Psenak, Ed.
Internet-Draft K. Talaulikar
Intended status: Standards Track Cisco Systems, Inc.
Expires: January 19, 2019 W. Henderickx
Nokia
P. Pillay-Esnault
Huawei
July 18, 2018
OSPF LLS Extensions for Local Interface ID Advertisement
draft-ietf-ospf-lls-interface-id-05
Abstract
Every OSPF interface is assigned an identifier, Interface ID, which
uniquely identifies the interface on the router. In some cases it is
useful to know the Interface ID assigned by the adjacent router on
its side of the adjacency (Remote Interface ID).
This draft describes the extensions to OSPF link-local signalling to
advertise the Local Interface Identifier.
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
BCP14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
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 January 19, 2019.
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Copyright Notice
Copyright (c) 2018 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Interface ID Exchange using TE Opaque LSA . . . . . . . . . . 3
3. Interface ID Exchange using OSPF LLS . . . . . . . . . . . . 3
3.1. Local Interface Identifier TLV . . . . . . . . . . . . . 3
4. Backward Compatibility with RFC 4203 . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Every OSPF interface is assigned an Interface ID, which uniquely
identifies the interface on the router. For example, some
implementations MAY be able to use the MIB-II IfIndex [RFC2863] as
the Interface ID.
Local/Remote Interface Identifiers MAY be flooded by OSPF [RFC2328]
as defined in [RFC4203]. From the perspective of the advertising
router, the Local Interface Identifier is a known value, however the
Remote Interface Identifier needs to be learnt before it can be
advertised. [RFC4203] suggests to use TE Link Local LSA [RFC3630] to
communicate the Local Interface Identifier to neighbors on the link.
Though such mechanism works, it has some drawbacks.
This draft proposes an extension to OSPF link-local signalling
[RFC5613] to advertise the Local Interface Identifier.
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2. Interface ID Exchange using TE Opaque LSA
Usage of the Link Local TE Opaque LSA to propagate the Local
Interface Identifier to the neighbors on the link is described in
[RFC4203]. This mechanism has following problems:
LSAs can only be flooded over an existing adjacency that is in
Exchange state or greater. The adjacency state machine progresses
independently on each side of the adjacency and, as such, may
reach the Full state on one side before the TE Link Opaque LSA
arrives. The consequence is that link can be initially advertised
without the Remote Interface Identifier. Later, when the TE Link
Opaque LSA arrives, the link must be advertised again, this time
with the valid Remote Interface Identifier. Implementations may
choose to wait before advertising the link, but there is no
guarantee that the neighbor will ever advertise the TE Link Opaque
LSA with the Interface Identifier. In summary, the existing
mechanism does not guarantee that the Remote Interface Identifier
is known at the time the link is advertised.
The TE Opaque LSA is defined for MPLS Traffic Engineering, but the
knowledge of the Remote Interface Identifier is useful also for
cases where MPLS TE is not used. One example is the lack of a
valid 2-way connectivity check for parallel point-to-point links
between OSPF routers.
3. Interface ID Exchange using OSPF LLS
To address the problems described earlier and to allow the Interface
Identifier exchange to be part of the neighbor discovery process, we
propose to extend OSPF link-local signalling to advertise the Local
Interface Identifier in OSPF Hello packets.
3.1. Local Interface Identifier TLV
The Local Interface Identifier TLV is a LLS TLV. It has 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
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Type: 18
Length: 4 octets
Local Interface Identifier: The value of the local Interface
Identifier.
Local Interface Identifier TLV signalling using LLS is applicable to
all OSPF interface types other than virtual links.
4. Backward Compatibility with RFC 4203
Implementations which support Local Interface ID signalling using LLS
MUST prefer the Local Interface ID value received through LLS over
the value received through Link Local TE Opaque LSA if both are
received from the same OSPF router.
Implementations which support Local Interface ID signalling via Link
Local TE Opaque LSA MAY continue to do so to ensure backward
compatibility. If they also support Local Interface ID signalling
using LLS as described herein, they SHOULD signal the same Local
Interface ID via both mechanisms.
During the rare conditions, when the Local Interface ID changes, a
timing interval may exist, where the received values of the Local
Interface ID advertised through LLS and Link Local TE Opaque LSA may
differ. Such situation is temporary and received values via both
mechanisms should become equal as soon as the next Hello and/or Link
Local TE Opaque LSA is re-generated by the originator.
5. IANA Considerations
This specification allocates a single code point from the "Open
Shortest Path First (OSPF) Link Local Signalling (LLS) - Type/Length/
Value Identifiers (TLV)" registry.
Following values is allocated:
o 18 - Local Interface Identifier TLV
6. Security Considerations
The security considerations for "OSPF Link-Local Signaling" [RFC5613]
also apply to the Local Interface Identifier TLV described herein.
The current usage of a neighbor's Local Interface Identifier is to
disambiguate parallel links between OSPF routers. Hence,
modification of the advertised Local Interface Identifier TLV may
result in the wrong neighbor interface identifier being advertised in
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the OSPFv2 Extended Link LSA [RFC8379] and could prevent the link
from being used. If authentication is being used in the OSPF routing
domain [RFC5709], then the Cryptographic Authentication TLV [RFC5613]
SHOULD also be used to protect that contents of the Link-Local
Signaling (LLS) block.
Implementations must assure that malformed LLS TLVs and Sub-TLVs
permutations do not result in errors which cause hard OSPF failures.
7. Contributors
8. Acknowledgements
Thanks to Tony Przygienda for his extensive review and useful
comments.
9. References
9.1. 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>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<https://www.rfc-editor.org/info/rfc4203>.
[RFC5613] Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D.
Yeung, "OSPF Link-Local Signaling", RFC 5613,
DOI 10.17487/RFC5613, August 2009,
<https://www.rfc-editor.org/info/rfc5613>.
[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>.
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9.2. Informative References
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
<https://www.rfc-editor.org/info/rfc2863>.
[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, DOI 10.17487/RFC5709, October
2009, <https://www.rfc-editor.org/info/rfc5709>.
[RFC8379] Hegde, S., Sarkar, P., Gredler, H., Nanduri, M., and L.
Jalil, "OSPF Graceful Link Shutdown", RFC 8379,
DOI 10.17487/RFC8379, May 2018,
<https://www.rfc-editor.org/info/rfc8379>.
Authors' Addresses
Peter Psenak (editor)
Cisco Systems, Inc.
Apollo Business Center
Mlynske nivy 43
Bratislava 821 09
Slovakia
Email: ppsenak@cisco.com
Ketan Jivan Talaulikar
Cisco Systems, Inc.
S.No. 154/6, Phase I, Hinjawadi
PUNE, MAHARASHTRA 411 057
India
Email: ketant@cisco.com
Wim Henderickx
Nokia
Copernicuslaan 50
Antwerp 2018
BE
Email: wim.henderickx@nokia.com
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Padma Pillay-Esnault
Huawei
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: padma@huawei.com
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