Internet DRAFT - draft-ietf-ospf-lls-interface-id
draft-ietf-ospf-lls-interface-id
Open Shortest Path First IGP P. Psenak, Ed.
Internet-Draft K. Talaulikar
Intended status: Standards Track Cisco Systems, Inc.
Expires: May 8, 2019 W. Henderickx
Nokia
P. Pillay-Esnault
Huawei
November 4, 2018
OSPF LLS Extensions for Local Interface ID Advertisement
draft-ietf-ospf-lls-interface-id-09
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 assigned Interface ID on the remote side of the
adjacency (Remote Interface ID).
This draft describes the extensions to OSPF link-local signalling
(LLS) 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 May 8, 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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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Interface ID Exchange using TE Opaque LSA . . . . . . . . 3
2. Interface ID Exchange using OSPF LLS . . . . . . . . . . . . 3
2.1. Local Interface Identifier TLV . . . . . . . . . . . . . 4
3. Backward Compatibility with RFC 4203 . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Every OSPF interface is assigned an Interface ID, which uniquely
identifies the interface on the router. [RFC2328] uses this
Interface ID in the Router-LSA Link Data for unnumbered links and
uses the value of the MIB-II IfIndex [RFC2863]. [RFC4203] refers to
these Interface IDs as the Link Local/Remote Identifiers and defines
a way to advertise and use them for Generalized Multi-Protocol Label
Switching (GMPLS) purposes. [RFC7684] defines a way to advertise
Local/Remote Interface IDs in the OSPFv2 Extended Link LSA.
There is a known OSPFv2 protocol problem in verifying the bi-
directional connectivity with parallel unnumbered links. If there
are two parallel unnumbered links between a pair of routers and each
link is only advertised from single direction, such two
unidirectional parallel links could be considered as a valid single
bidirectional link during the OSPF route computation on some other
router. If each link is advertised with both its Local and Remote
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Interface IDs, the advertisement of each link from both sides of
adjacency can be verified by cross-checking the Local and Remote
Interface IDs of both advertisements.
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 (LLS)
[RFC5613] to advertise the Local Interface Identifier.
1.1. 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 the 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 mentioned
lack of a valid 2-way connectivity check for parallel point-to-
point links between OSPF routers.
2. 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 and Database Description (DD)
packets.
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2.1. 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:
Type: TBD
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.
3. Backward Compatibility with RFC 4203
If the Local Interface ID signaling via Link Local TE Opaque LSA is
supported in addition to the new LLS mechanism, implementations which
support Local Interface ID signalling using LLS MUST prefer the Local
Interface ID value received through LLS over the value received
through the 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 MUST 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.
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4. 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 value is allocated:
o TBD - Local Interface Identifier TLV
5. 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
the OSPFv2 Extended Link LSA [RFC7684] 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.
Receiving a malformed LLS Interface Identifier TLV MUST NOT result in
a hard router or OSPF process failure. The reception of malformed
LLS TLVs or Sub-TLVs SHOULD be logged but such logging MUST be rate-
limited to prevent Denial-of-Service (DoS) attacks.
The interface ID is assigned by the advertising OSPF router as a
locally unique identifier and need not be unique in any broader
context; it is not expected to contain any information about the
device owner or traffic transiting the device, so there are no
privacy oncerns associated with its advertisement.
6. Acknowledgments
Thanks to Tony Przygienda for his extensive review and useful
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>.
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[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>.
[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>.
7.2. 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>.
Authors' Addresses
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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
Belgium
Email: wim.henderickx@nokia.com
Padma Pillay-Esnault
Huawei
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: padma@huawei.com
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