Internet DRAFT - draft-ppsenak-ospf-lls-interface-id
draft-ppsenak-ospf-lls-interface-id
Open Shortest Path First IGP P. Psenak, Ed.
Internet-Draft K. Talaulikar
Intended status: Standards Track Cisco Systems, Inc.
Expires: November 24, 2017 W. Henderickx
Nokia
P. Pillay-Esnault
Huawei
May 23, 2017
OSPF LLS Extensions for Local Interface ID Advertisement
draft-ppsenak-ospf-lls-interface-id-01
Abstract
This draft describes the extensions to OSPF link-local signaling to
advertise Local Interface Identifier.
Requirements Language
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 2119 [RFC2119].
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
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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 November 24, 2017.
Copyright Notice
Copyright (c) 2017 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Interface ID Exchange using TE Opaque LSA . . . . . . . . . . 2
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 . . . . . . . . . . . . . . . . . . . . . . . . 4
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
9. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction
Every 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 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 signaling (LLS)
[RFC5613] to advertise the Local Interface Identifier.
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
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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. Implementation 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 Remote Interface Identifier is
known at the time the link is advertised.
TE Opaque LSA is defined for MPLS Traffic Engineering, but the
knowledge of the Remote Interface Identifier is useful for other
cases where MPLS TE is not used. One example is the lack of valid
2-way connectivity check for remote parallel point-to-point links
in OSPF. In such case, TE Opaque LSAs are not exchanged solely
for 2-way connectivity correctness.
3. Interface ID Exchange using OSPF LLS
To address the problems described earlier and to allow the Interface
Identifiers exchange to be part of the neighbor discovery process, we
propose to extend OSPF link-local signaling to advertise the Local
Interface Identifier in OSPF Hello packets.
3.1. Local Interface Identifier TLV
The Local Interface Identifier TLV is a new 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, suggested value 18
Length: 4 octet
Local Interface Identifier: The value of the local Interface
Identifier.
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Local Interface Identifier TLV MUST be present in all Hello packets
on all link types, except packets that are sent to the remote end of
the virtual-link.
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 the Link Local TE Opaque LSAs.
Implementations which also support the Local Interface ID signalling
via Link Local TE Opaque LSA MAY continue to do so to ensure backward
compatibility and 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.
5. IANA Considerations
This specification updates Link Local Signalling TLV Identifiers
registry.
Following values is allocated:
o 18 - Local Interface Identifier TLV
6. Security Considerations
Implementations must assure that malformed LLS TLV and Sub-TLV
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. Normative References
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<http://www.rfc-editor.org/info/rfc2328>.
[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
<http://www.rfc-editor.org/info/rfc2863>.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<http://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,
<http://www.rfc-editor.org/info/rfc4203>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<http://www.rfc-editor.org/info/rfc5340>.
[RFC5613] Zinin, A., Roy, A., Nguyen, L., Friedman, B., and D.
Yeung, "OSPF Link-Local Signaling", RFC 5613,
DOI 10.17487/RFC5613, August 2009,
<http://www.rfc-editor.org/info/rfc5613>.
Authors' Addresses
Peter Psenak (editor)
Cisco Systems, Inc.
Apollo Business Center
Mlynske nivy 43
Bratislava 821 09
Slovakia
Email: ppsenak@cisco.com
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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
Padma Pillay-Esnault
Huawei
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: padma@huawei.com
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