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L                                                              P. Shaofu
Internet-Draft                                                    C. Ran
Intended status: Standards Track                         ZTE Corporation
Expires: July 2, 2020                                          G. Mirsky
                                                               ZTE Corp.
                                                       December 30, 2019


                 IGP Flexible Algorithm with L2bundles
                 draft-peng-lsr-flex-algo-l2bundles-00

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.

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   This Internet-Draft will expire on July 2, 2020.

Copyright Notice

   Copyright (c) 2019 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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   (https://trustee.ietf.org/license-info) in effect on the date of
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   to this document.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   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 Extensions . . . . . . . . . . . . .   4
     5.1.  ISIS L2 Bundle Member EAG Extension . . . . . . . . . . .   4
     5.2.  OSPF L2 Bundle Member EAG Extension . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     6.1.  ISIS IANA Considerations  . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

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 Extensions

5.1.  ISIS L2 Bundle Member EAG Extension

   [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.
   For individual EAG attributes of L2 Bundle Member purpose, this
   document defines a new "ISIS L2 Bundle Member EAG sub-TLV".  It has
   the following format:

















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       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     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Extended Admin Group of L2 Bundle Member 1           |
      +-                                                             -+
      |                            ...                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Extended Admin Group of L2 Bundle Member 2           |
      +-                                                             -+
      |                            ...                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         ... ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          Extended Admin Group of L2 Bundle Member N           |
      +-                                                             -+
      |                            ...                                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


            Figure 1: ISIS L2 Bundle Member EAG sub-TLV format

   where:

   Type: TBD1.

   Length: 4 octets, it give the total length of EAG information of all
   members.

   Extended Admin Group of L2 Bundle Member: for each L2 Bundle Member
   there is an EAG value.  Note that "L2 Bundle Member Attributes sub-
   TLV" explicitly give how many L2 Bundle Members there are and list
   each L2 Bundle Member Identifier in order, thus in "ISIS L2 Bundle
   Member EAG sub-TLV" there MUST be an EAG value for each L2 Bundle
   Member in the same order.

   "ISIS L2 Bundle Member EAG sub-TLV" MAY NOT appear more then once in
   TLV-25.  If it appears more then once, the first one is valid.

5.2.  OSPF L2 Bundle Member EAG Extension

   [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,



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   it is sufficient to construct Flex-algo plane to select L2 link
   resource.

6.  IANA Considerations

6.1.  ISIS IANA Considerations

   This document adds the following new sub-TLV to the ISIS TLV-25
   registry.

   Type: TBD1

   Description: ISIS L2 Bundle Member Extended Administrative Group

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-05 (work in progress), November 2019.

   [I-D.ketant-lsr-ospf-l2bundles]
              Talaulikar, K. and P. Psenak, "Advertising L2 Bundle
              Member Link Attributes in OSPF", draft-ketant-lsr-ospf-
              l2bundles-00 (work in progress), July 2019.

   [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>.







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   [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>.

   [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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