Internet DRAFT - draft-ietf-lsr-ospf-l2bundles
draft-ietf-lsr-ospf-l2bundles
Link State Routing K. Talaulikar, Ed.
Internet-Draft P. Psenak
Updates: 9085 (if approved) Cisco Systems
Intended status: Standards Track 7 October 2022
Expires: 10 April 2023
Advertising Layer 2 Bundle Member Link Attributes in OSPF
draft-ietf-lsr-ospf-l2bundles-10
Abstract
There are deployments where the Layer 3 (L3) interface on which OSPF
operates is a Layer 2 (L2) interface bundle. Existing OSPF
advertisements only support advertising link attributes of the Layer
3 interface. If entities external to OSPF wish to control traffic
flows on the individual physical links which comprise the Layer 2
interface bundle, link attribute information for the bundle members
is required.
This document defines the protocol extensions for OSPF to advertise
the link attributes of L2 bundle members. The document also
specifies the advertisment of these OSPF extensions via BGP Link
State protocol and thereby updates RFC9085.
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 10 April 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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 to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. L2 Bundle Member Attributes . . . . . . . . . . . . . . . . . 4
3. BGP-LS Advertisement . . . . . . . . . . . . . . . . . . . . 7
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Operational Considerations . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 9
8.2. Informational References . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
There are deployments where the Layer 3 interface on which an OSPF
adjacency is established is a Layer 2 interface bundle, for instance
a Link Aggregation Group (LAG) [IEEE802.1AX]. This reduces the
number of adjacencies that need to be maintained by the OSPF protocol
in cases where there are parallel links between the neighbors.
Entities external to OSPF such as Path Computation Elements (PCE)
[RFC4655] may wish to control traffic flows on individual Layer 2
member links of the underlying bundle (e.g., LAG) interface. To do
so, link attribute information for individual bundle members is
required. The protocol extensions defined in this document provide
the means to advertise this information.
This document defines sub-TLVs to advertise link attribute
information for each of the L2 bundle members which comprise the
Layer 3 interface on which OSPF operates. Similar capabilities were
introduced in IS-IS via [RFC8668].
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[RFC8665] and [RFC8666] introduced the adjacency segment identifier
(Adj-SID) link attribute for OSPFv2 and OSPFv3 respectively which can
be used as an instruction to forwarding to send traffic over a
specific link [RFC8402]. This document enables the advertisement of
the Adj-SIDs using the same Adjacency SID Sub-TLV at the granularity
level of each L2 bundle member link so that traffic may be steered
over that specific member link.
Note that the advertisements at the L2 bundle member link-level
defined in this document are intended to be provided to external (to
OSPF) entities and do not alter or change the OSPF route computation.
The following items are intentionally not defined and are outside the
scope of this document:
* What link attributes will be advertised. This is determined by
the needs of the external entities.
* A minimum or default set of link attributes.
* How these attributes are configured.
* How the advertisements are used.
* What impact the use of these advertisements may have on traffic
flow in the network.
* How the advertisements are passed to external entities.
The BGP Link State (BGP-LS) [RFC7752] was extended for the
advertisement of Layer 2 bundle members and their attributes by
[RFC9085] which covered only IS-IS. This document updates [RFC9085]
by specifying the advertisement from OSPF (refer Section 3).
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.
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2. L2 Bundle Member Attributes
A new L2 Bundle Member Attributes Sub-TLV is introduced to advertise
L2 bundle member attributes in both OSPFv2 and OSPFv3. In the case
of OSPFv2, this sub-TLV is an optional sub-TLV of the OSPFv2 Extended
Link TLV that is used to describe link attributes via the OSPFv2
Extended Link Opaque LSA [RFC7684]. In the case of OSPFv3, this sub-
TLV is an optional sub-TLV of the Router Link TLV of the OSPFv3 E-
Router-LSA [RFC8362].
When the OSPF adjacency is associated with an L2 bundle interface,
this sub-TLV is used to advertise the underlying L2 bundle member
links along with their respective link attributes. The inclusion of
this information implies that the identified link is a member of the
L2 bundle associated with an OSPF L3 link and that the member link is
operationally up. Therefore, advertisements of member links MUST NOT
be done when the member link becomes operationally down or it is no
longer a member of the identified L2 bundle.
The advertisement of the L2 Bundle Member Attributes Sub-TLV may be
asymmetric for an OSPF link depending on the underlying layer 2
connectivity i.e., advertised by the router on only one end.
The L2 Bundle Member Attributes 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| L2 Bundle Member Descriptor |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member Link Attribute sub-TLVs (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: L2 Bundle Member Attributes sub-TLV Format
Where:
Type: 24 for OSPFv2 and 29 for OSPFv3
Length: The total length (in octets) of the value portion of the
TLV including nested Sub-TLVs.
L2 Bundle Member Descriptor: A 4 octet Link Local Identifier as
described in [RFC4202] and used in [RFC8510] for the member link.
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Link attributes for L2 bundle member links are advertised as sub-TLVs
of the L2 Bundle Member Attribute Sub-TLV.
In the case of OSPFv2, the L2 Bundle Member Attributes Sub-TLV shares
the sub-TLV space of the Extended Link TLV and the sub-TLVs of the
Extended Link TLV MAY be used to describe the attributes of the
member link. Figure 2 below lists sub-TLVs and their applicability
for L2 bundle member links. The sub-TLVs that are not applicable
MUST NOT be used as sub-TLVs for the L2 Bundle Member Attributes Sub-
TLV. Specifications that introduce new sub-TLVs of the Extended Link
TLV MUST indicate their applicability for the L2 Bundle Member
Attributes Sub-TLV. Typically, attributes that have Layer 3
semantics would not be applicable while Layer 2 attributes would
apply. An implementation MUST ignore any sub-TLVs received that are
not applicable in the context of the L2 Bundle Member Attribute Sub-
TLV.
Y - applicable
N - not-applicable
1 SID/Label (N)
2 Adj-SID (Y)
3 LAN Adj-SID/Label (Y)
4 Network-to-Router Metric (N)
5 RTM Capability (N)
6 OSPFv2 Link MSD (N)
7 Graceful-Link-Shutdown (N)
8 Remote IPv4 Address (N)
9 Local/Remote Interface ID (N)
10 Application Specific Link Attributes (Y)
11 Shared Risk Link Group (Y)
12 Unidirectional Link Delay (Y)
13 Min/Max Unidirectional Link Delay (Y)
14 Unidirectional Delay Variation (Y)
15 Unidirectional Link Loss (Y)
16 Unidirectional Residual Bandwidth (Y)
17 Unidirectional Available Bandwidth (Y)
18 Unidirectional Utilized Bandwidth (Y)
19 Administrative Group (Y)
20 Extended Administrative Group (Y)
21 OSPFv2 Link Attributes Bits (N)
22 TE Metric (Y)
23 Maximum Link Bandwidth (Y)
24 L2 Bundle Member Attributes (N)
Figure 2: Applicability of OSPFv2 Link Attribute Sub-TLVs for L2
Bundle Members
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In the case of OSPFv3, the L2 Bundle Member Attributes Sub-TLV shares
the sub-TLV space of the Router Link TLV and the sub-TLVs of the
Router Link TLV MAY be used to describe the attributes of the member
link. Figure 3 below lists sub-TLVs that are applicable to the
Router Link TLV and their applicability for L2 bundle member links.
The sub-TLVs that are not applicable MUST NOT be used as sub-TLVs for
the L2 Bundle Member Attributes Sub-TLV. Specifications that
introduce new sub-TLVs of the Router Link TLV MUST indicate their
applicability for the L2 Bundle Member Attributes Sub-TLV. An
implementation MUST ignore any sub-TLVs received that are not
applicable in the context of the L2 Bundle Member Attribute Sub-TLV.
Y - applicable
N - not-applicable
X - not Router Link Sub-TLV
1 IPv6-Forwarding-Address (X)
2 IPv4-Forwarding-Address (X)
3 Route-Tag (X)
4 Prefix SID (X)
5 Adj-SID (Y)
6 LAN Adj-SID (Y)
7 SID/Label (N)
8 Graceful-Link-Shutdown (N)
9 OSPFv3 Link MSD (N)
10 OSPFv3 Link Attribute Bits (N)
11 Application Specific Link Attributes (Y)
12 Shared Risk Link Group (Y)
13 Unidirectional Link Delay (Y)
14 Min/Max Unidirectional Link Delay (Y)
15 Unidirectional Delay Variation (Y)
16 Unidirectional Link Loss (Y)
17 Unidirectional Residual Bandwidth (Y)
18 Unidirectional Available Bandwidth (Y)
19 Unidirectional Utilized Bandwidth (Y)
20 Administrative Group (Y)
21 Extended Administrative Group (Y)
22 Traffic Engineering Metric (Y)
23 Maximum Link Bandwidth (Y)
24 Local Interface IPv6 Address (N)
25 Remote Interface IPv6 Address (N)
26 Flex-Algorithm Prefix Metric (X)
27 Prefix Source OSPF Router-ID (X)
28 Prefix Source Router Address (X)
29 L2 Bundle Member Attributes (N)
30 SRv6 SID Structure (Y)
31 SRv6 End.X SID Structure (Y)
32 SRv6 End.X SID Structure (Y)
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Figure 3: Applicability of OSPFv3 Link Attribute Sub-TLVs for L2
Bundle Members
3. BGP-LS Advertisement
The BGP-LS extensions for the advertisment of Layer 2 bundle members
and their attributes was specified in [RFC9085]. Using the OSPF L2
Bundle Member Attributes sub-TLV defined in this document, the L2
bundle member information can now be advertised from OSPF into BGP-LS
on the same lines as discussed for IS-IS in section 2.2.3 of
[RFC9085].
4. IANA Considerations
IANA has allocated the following code point via early allocation in
the "OSPFv2 Extended Link TLV Sub-TLVs" registry under the "OSPFv2
Parameters" registry that needs to be made permanent:
Value: 24
Name: L2 Bundle Member Attributes
IANA has allocated the following code point via early allocation in
the "OSPFv3 Extended LSA Sub-TLVs" registry under the "OSPFv3
Parameters" registry that needs to be made permanent:
Value: 29
Name: L2 Bundle Member Attributes
IANA is requested to introduce a column "Applicability to L2 Bundle
Member sub-TLV" (abbreviated as L2BM) in the registry tables for the
"OSPFv2 Extended Link TLV Sub-TLVs" registry with the initial updates
(Y/N) against allocations as indicated in Figure 2. An explanatory
note is also to be added to this registry as follows:
The column for the Applicability to L2 Bundle Member sub-TLV (L2BM)
may be marked as follows:
Y - sub-TLV MAY appear in L2 Bundle Member sub-TLV
N - sub-TLV MUST NOT appear in L2 Bundle Member sub-TLV
Similarly, IANA is requested to introduce a column "Applicability to
L2 Bundle Member sub-TLV" (abbreviated as L2BM) in the registry
tables for the "OSPFv3 Extended LSA Sub-TLVs" registry with the
initial updates (Y/N/X) against allocations as indicated in Figure 3.
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The column for the Applicability to L2 Bundle Member sub-TLV (L2BM)
may be marked as follows:
Y - sub-TLV MAY appear in L2 Bundle Member sub-TLV
N - sub-TLV MUST NOT appear in L2 Bundle Member sub-TLV
X - sub-TLV is not a Router Link sub-TLV; it MUST NOT appear
in L2 Bundle Member sub-TLV
Further allocations from these two registries are required to
indicate the applicability of the introduced sub-TLV to the L2 Bundle
Member sub-TLV that would get updated in these registries.
5. Operational Considerations
Implementations MUST NOT enable the advertisement of Layer 2 bundle
member links and their attributes in OSPF LSAs by default and MUST
provide a configuration option to enable their advertisement on
specific links.
[I-D.ietf-ospf-yang] specifies the base OSPF YANG model. The
required configuration and operational elements for this feature are
expected to be introduce as augmentation to this base OSPF YANG
model.
6. Security Considerations
The OSPF protocol has supported the advertisement of link attribute
information, including link identifiers, for many years. The
advertisements defined in this document are identical to existing
advertisements defined in [RFC3630], [RFC4203], [RFC5329], [RFC7471],
[RFC8665], and [RFC8666] - but are associated with L2 links which are
part of a bundle interface on which the OSPF protocol operates.
Therefore, the security considerations of these documents are
applicable and there are no new security issues introduced by the
extensions in this document.
As always, if the protocol is used in an environment where
unauthorized access to the physical links on which OSPF packets are
sent occurs then attacks are possible. The use of authentication as
defined in [RFC5709], [RFC7474], [RFC4552], and [RFC7166] is
recommended for preventing such attacks.
7. Acknowledgements
This document leverages the similar work done for IS-IS and the
authors of this document would like to acknowledge the contributions
of the authors of [RFC8668].
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The authors would like to thank Anoop Ghanwani, Paul Kyzivat, Dan
Romascanu, and Russ Mundy for their review and feedback on this
document. The authors would also like to thank Acee Lindem for his
detailed shepherd review of this document. The authors would also
like to thank John Scudder for his AD review and the discussion
related to the applicability of TLVs/sub-TLVs to the L2 Bundle Member
TLV.
8. References
8.1. Normative References
[IEEE802.1AX]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks - Link Aggregation IEEE Std 802.1AX-2020
(Revision of IEEE Std 802.1AX-2014)", 30 January 2020.
[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>.
[RFC4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, DOI 10.17487/RFC4202, October 2005,
<https://www.rfc-editor.org/info/rfc4202>.
[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>.
[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>.
[RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", RFC 8665,
DOI 10.17487/RFC8665, December 2019,
<https://www.rfc-editor.org/info/rfc8665>.
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[RFC8666] Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions
for Segment Routing", RFC 8666, DOI 10.17487/RFC8666,
December 2019, <https://www.rfc-editor.org/info/rfc8666>.
[RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
H., and M. Chen, "Border Gateway Protocol - Link State
(BGP-LS) Extensions for Segment Routing", RFC 9085,
DOI 10.17487/RFC9085, August 2021,
<https://www.rfc-editor.org/info/rfc9085>.
8.2. Informational References
[I-D.ietf-ospf-yang]
Yeung, D., Qu, Y., Zhang, J., Chen, I., and A. Lindem,
"YANG Data Model for OSPF Protocol", Work in Progress,
Internet-Draft, draft-ietf-ospf-yang-29, 17 October 2019,
<https://www.ietf.org/archive/id/draft-ietf-ospf-yang-
29.txt>.
[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>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[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>.
[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>.
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[RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
Authentication Trailer for OSPFv3", RFC 7166,
DOI 10.17487/RFC7166, March 2014,
<https://www.rfc-editor.org/info/rfc7166>.
[RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
<https://www.rfc-editor.org/info/rfc7471>.
[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>.
[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>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8510] Psenak, P., Ed., Talaulikar, K., Henderickx, W., and P.
Pillay-Esnault, "OSPF Link-Local Signaling (LLS)
Extensions for Local Interface ID Advertisement",
RFC 8510, DOI 10.17487/RFC8510, January 2019,
<https://www.rfc-editor.org/info/rfc8510>.
[RFC8668] Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri,
M., and E. Aries, "Advertising Layer 2 Bundle Member Link
Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668,
December 2019, <https://www.rfc-editor.org/info/rfc8668>.
Authors' Addresses
Ketan Talaulikar (editor)
Cisco Systems
India
Email: ketant.ietf@gmail.com
Peter Psenak
Cisco Systems
Apollo Business Center
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Mlynske nivy 43
821 09 Bratislava
Slovakia
Email: ppsenak@cisco.com
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