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L P. Shaofu
Internet-Draft C. Ran
Intended status: Informational ZTE Corporation
Expires: October 1, 2020 G. Mirsky
ZTE Corp.
March 30, 2020
IGP Flexible Algorithm with L2bundles
draft-peng-lsr-flex-algo-l2bundles-01
Abstract
IGP Flex Algorithm proposes a solution that allows IGPs themselves to
compute constraint based paths over the network, and it also
specifies a way of using Segment Routing (SR) Prefix-SIDs and SRv6
locators to steer packets along the constraint-based paths. This
document describes how to create Flex-algo plane with L2bundles
scenario.
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
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and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 1, 2020.
Copyright Notice
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include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Color set on L2 Bundle Member . . . . . . . . . . . . . . . . 3
4. Flex-algo plane with L2 link resource . . . . . . . . . . . . 3
4.1. Best-effort . . . . . . . . . . . . . . . . . . . . . . . 3
4.2. Traffic Engineering . . . . . . . . . . . . . . . . . . . 4
5. IGP L2 Bundle Member EAG advertisement . . . . . . . . . . . 4
5.1. ISIS L2 Bundle Member EAG advertisement . . . . . . . . . 4
5.2. OSPF L2 Bundle Member EAG advertisement . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
IGP Flex Algorithm [I-D.ietf-lsr-flex-algo] proposes a solution that
allows IGPs themselves to compute constraint based paths over the
network, and it also specifies a way of using Segment Routing (SR)
Prefix-SIDs and SRv6 locators to steer packets along the constraint-
based paths. It specifies a set of extensions to ISIS, OSPFv2 and
OSPFv3 that enable a router to send TLVs that identify (a)
calculation-type, (b) specify a metric-type, and (c )describe a set
of constraints on the topology, that are to be used to compute the
best paths along the constrained topology. A given combination of
calculation-type, metric-type, and constraints is known as an FAD
(Flexible Algorithm Definition).
[RFC8668] and [I-D.ketant-lsr-ospf-l2bundles] introduces the ability
for IS-IS and OSPF respectively to advertise the link attributes of
Layer 2 (L2) Bundle Members. Especially, the link attribute
"Administrative Group" and "Extended Administrative Group" could be
individual to each L2 Bundle Member for purpose of Flex-algo plane
construction, where multiple Flex-algo planes share the same Layer 3
parent interface and each Flex-algo plane has dedicated L2 Bundle
Member.
This document describes how to create Flex-algo plane with L2bundles
scenario.
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2. 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.
3. Color set on L2 Bundle Member
Traffic Engineering affinity (also termed as Color) is often to be
set on the Layer 3 interface and be flooded by IGP-TE. However, when
the Layer 3 interface is a Layer 2 interface bundle, operators can
config individual color for each L2 Bundle Member. So that IGP link-
state database will contain the TE affinity attribute of L2 Bundle
Member, as well as Layer 3 parrent interface.
Note that Layer 3 interface can join to IGP instance explicitly, but
L2 Bundle Member not.
The TE affinity of the Layer 3 parrent interface can be a combined
value of all L2 Bundle Members. For example, if the Layer 3 parrent
interface contains three L2 Bundle Members, each with color "RED",
"GREEN", "BLUE" respectively, the Layer 3 parrent interface will have
color "RED|GREEN|BLUE".
4. Flex-algo plane with L2 link resource
4.1. Best-effort
[I-D.ietf-lsr-flex-algo] defines the color-based link resource
selection rules in FAD to construct the expected Flex-algo plane.
Each node in the Flex-algo plane will establish the SPT with self as
root node, to maintain the best path to other nodes and get the FIB
entry based on that. The root node need check the outgoing Layer 2
interface bundle interface, to see which L2 Bundle Member does
exactly belong to the Flex-algo plane. The forwarding information of
the FIB entry with outgoing Layer 2 interface bundle interface will
exactly select the L2 Bundle Member that belongs to the Flex-algo
plane to forward packets.
For example, three Flex-algo plane share the same Layer 3 parrent
interface including three L2 Bundle Members each with color "RED",
"GREEN", "BLUE" respectively, and each Flex-algo plane with link
selection rule "Include-Any RED", "Include-Any GREEN", "Include-Any
BLUE" respectively, Flex-algo SHOULD not simply select the Layer 3
parrent interface to all Flex-algo plane, but need continue to select
individual L2 Bundle Member to the specific Flex-algo plane. As a
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reslut, the FIB entry within Flex-algo RED plane will exactly choose
the L2 Bundle Members with color "RED" to forward packets, the FIB
entry within Flex-algo GREEN plane will exactly choose the L2 Bundle
Members with color "GREEN" to forward packets, and the FIB entry
within Flex-algo BLUE plane will exactly choose the L2 Bundle Members
with color "BLUE" to forward packets.
4.2. Traffic Engineering
A segment list contains SIDs advertised specifically for the given
algorithm is possible, such as an inter-domain path contains multiple
Flex-algo planes, a TI-LFA backup path within the Flex-algo plane, or
an optimized TE path avoiding congested link within the Flex-algo
plane. In these cases, an Adjacency segment could be used to steer
the packets along the expected L2 Bundle Member that belongs to the
specific Flex-algo plane.
[RFC8668] and [I-D.ketant-lsr-ospf-l2bundles] have defined Adjacency-
SID for each L2 Bundle Member, that can be used to isolate flows
among multiple Flex-algo planes, when these Flex-algo planes share
the same Layer 3 parrent interface. A specific Adjacency-SID for a
specific L2 Bundle Member will steer the packets to that member.
5. IGP L2 Bundle Member EAG advertisement
5.1. ISIS L2 Bundle Member EAG advertisement
[RFC8668] defined TLV-25 for ISIS to advertise the link attributes of
L2 Bundle Members, and mentioned that the traditional "Administrative
group (color) Sub-TLV" and "Extended Administrative Group Sub-TLV"
may appear in TLV-25 and MAY be shared by multiple L2 Bundle Members.
If we want to advertise unique EAG values for each bundle member, we
can use multiple L2 Bundle Attribute Descriptors with each specify a
single bundle member.
5.2. OSPF L2 Bundle Member EAG advertisement
[I-D.ketant-lsr-ospf-l2bundles] defined "L2 Bundle Member Attributes
sub-TLV" for OSPF/OSPFv3 to advertise the link attributes of L2
Bundle Members, and mentioned that the traditional "Administrative
group (color) Sub-TLV" and "Extended Administrative Group Sub-TLV"
are applicable in "L2 Bundle Member Attributes sub-TLV". Because
there is "L2 Bundle Member Attributes sub-TLV" per L2 Bundle Member,
it is also sufficient to construct Flex-algo plane to select L2 link
resource.
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6. IANA Considerations
This document need not define new sub-TLV to IGP for Flex-algo
combined with l2bundles.
7. Security Considerations
There are no new security issues introduced by the extensions in this
document.
8. Acknowledgements
TBD
9. Normative References
[I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
algo-06 (work in progress), February 2020.
[I-D.ketant-lsr-ospf-l2bundles]
Talaulikar, K. and P. Psenak, "Advertising L2 Bundle
Member Link Attributes in OSPF", draft-ketant-lsr-ospf-
l2bundles-01 (work in progress), 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>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
[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>.
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[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>.
[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>.
[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
Peng Shaofu
ZTE Corporation
No.68 Zijinghua Road, Yuhuatai District
Nanjing
China
Email: peng.shaofu@zte.com.cn
Chen Ran
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China
Email: chen.ran@zte.com.cn
Greg Mirsky
ZTE Corp.
Email: gregimirsky@gmail.com
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