OSPF Working Group                                                 X. Xu
Internet-Draft                                               Alibaba Inc
Intended status: Standards Track                                 S. Kini
Expires: April 27, October 19, 2020
                                                               P. Psenak
                                                             C. Filsfils
                                                            S. Litkowski
                                                     Cisco Systems, Inc.
                                                                M. Bocci
                                                                   Nokia
                                                        October 25, 2019
                                                          April 17, 2020

  Signaling Entropy Label Capability and Entropy Readable Label-stack Label Depth
                               Using OSPF
                      draft-ietf-ospf-mpls-elc-12
                      draft-ietf-ospf-mpls-elc-13

Abstract

   Multiprotocol Label Switching (MPLS) has defined a mechanism to load-
   balance traffic flows using Entropy Labels (EL).  An ingress Label
   Switching Router (LSR) cannot insert ELs for packets going into a
   given tunnel Label Switched Path (LSP) unless an egress LSR has indicated
   via signaling that it has the capability to process ELs, referred to
   as the Entropy Label Capability (ELC), on that tunnel.  In addition,
   it would be useful for ingress LSRs to know each LSR's capability of for
   reading the maximum label stack depth and performing EL-based load-balancing, load-
   balancing, referred to as Entropy Readable Label Depth (ERLD).  This
   document defines a mechanism to signal these two capabilities using OSPF and OSPFv3.
   These mechanism is particularly useful in the environment where
   Segment Routing (SR) is used, where label advertisements are done via
   protocols like OSPF
   OSPFv2 and OSPFv3.

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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   This Internet-Draft will expire on April 27, October 19, 2020.

Copyright Notice

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   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Advertising ELC Using OSPF  . . . . . . . . . . . . . . . . .   3
     3.1.  Advertising ELC Using OSPFv2  . . . . . . . . . . . . . .   4   3
     3.2.  Advertising ELC Using OSPFv3  . . . . . . . . . . . . . .   4
   4.  Advertising ERLD Using OSPF . . . . . . . . . . . . . . . . .   4
   5.  Signaling ELC and ERLD in BGP-LS  . . . . . . . . . . . . . .   4
   6.  Acknowledgements  .  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  IANA  Security Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations  Contributors  . . . . . . . . . . . . . . . . . . . .   5
   9.  Contributors . . . .   5
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . .   5 . .   6
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   6
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [RFC6790] describes a method to load-balance Multiprotocol Label
   Switching (MPLS) traffic flows using Entropy Labels (EL).  It also
   introduces the concept of Entropy Label Capability (ELC) and defines
   the signaling of this capability via MPLS signaling protocols.
   Recently, mechanisms have been defined to signal labels via link-
   state Interior Gateway Protocols (IGP) such as OSPF
   [I-D.ietf-ospf-segment-routing-extensions].  In such scenarios, the
   signaling mechanisms defined in [RFC6790] are inadequate. OSPFv2 [RFC8665] and
   OSPFv3 [RFC8666].  This draft defines a mechanism to signal the ELC
   using OSPF.  This mechanism is
   useful when the label advertisement is also done via OSPF. OSPFv2 and OSPFv3.

   In addition, in the cases where stacked LSPs are used for whatever
   reasons (e.g., SR-MPLS [I-D.ietf-spring-segment-routing-mpls]), [RFC8660], it would be
   useful for ingress LSRs to know each intermediate LSR's capability of
   reading the maximum label stack depth and performing EL-based load-balancing. load-
   balancing.  This capability, referred to as Entropy Readable Label
   Depth (ERLD) as defined in
   [I-D.ietf-mpls-spring-entropy-label] [RFC8662] may be used by ingress LSRs to
   determine the position of the EL label in the stack, and whether it's
   necessary to insert multiple ELs at different positions in the label
   stack.

2.  Terminology

   This document memo makes use of the terms defined in [RFC6790], [RFC7770] and [I-D.ietf-mpls-spring-entropy-label]. [RFC8662].

   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] BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The key word OSPF is used throughout the document to refer to both
   OSPFv2 and OSPFv3.

3.  Advertising ELC Using OSPF

   Even though ELC is a property of the node, in some cases it is
   advantageous to associate and advertise the ELC with the a prefix.  In
   multi-area networks, routers may not know the identity of the prefix
   originator in a remote area, or may not know the capabilities of such
   originator.  Similarly, in a multi domain network, the identity of
   the prefix originator and its capabilities may not be known to the
   ingress LSR.

   If a router has multiple line cards, interfaces, the router MUST NOT announce ELC
   unless all of its line-cards interfaces are capable of processing ELs.

   If the router supports ELs on all of its line cards, interfaces, it SHOULD
   advertise the ELC with every local host prefix it advertises in OSPF.

   When an OSPF Area Border Router (ABR) advertises the prefix to the distributes information between
   connected area based on the intra-area or inter-area prefix that is
   reachable in some other area, areas it MUST preserve the ELC signalling for
   such prefix. setting.

   When an OSPF Autonomous System Boundary Router (ASBR) redistributes
   the a
   prefix from another instance of the OSPF or from some other protocol,
   it SHOULD preserve the ELC signaling for the prefix.  The exact
   mechanism used to exchange ELC between protocol instances on the ASBR
   is outside of the scope of this document and is
   implementation specific. document.

3.1.  Advertising ELC Using OSPFv2

   [RFC7684] defines the OSPFv2 Extended Prefix TLV to advertise
   additional attributes associated with a prefix.  The OSPFv2 Extended
   Prefix TLV includes a one octet Flags field.  A new flag in the Flags
   field is used to signal the ELC for the prefix:

      0x20 - E-Flag (ELC Flag): Set by the advertising router to
      indicate that the prefix originator is capable of processing ELs.

3.2.  Advertising ELC Using OSPFv3

   [RFC5340] defines the OSPFv3 PrefixOptions that are advertised along field to indicate
   capabilities associated with the a prefix.  A new bit in the OSPFV3 OSPFv3
   PrefixOptions is used to signal the ELC for the prefix:

      0x04 - E-Flag (ELC Flag): Set by the advertising router to
      indicate that the prefix originator is capable of processing ELs.

4.  Advertising ERLD Using OSPF

   A new MSD (Maximum SID Depth) type of the Node MSD sub-TLV [RFC8476],
   called

   The ERLD is defined to advertise the ERLD of advertised in a given router.  The
   scope of the advertisement depends on Node MSD sub-TLV [RFC8476] using the application.

   Assignment of a MSD-Type for ERLD is
   ERLD-MSD type defined in [I-D.ietf-isis-mpls-elc].

   If a router has multiple line-cards interfaces with different capabilities for of
   reading the maximum label stack depth, the router MUST advertise the
   smallest one.

   The absence of ERLD-MSD advertisements indicates only that the
   advertising node does not support advertisement of this capability.

   When the ERLD MSD-Type is received in the OSPFv2 or OSPFv3 Link MSD
   Sub-TLV, it MUST be ignored.

   The considerations for advertising the ERLD are specified in
   [RFC8662].

5.  Signaling ELC and ERLD in BGP-LS

   The OSPF extensions defined in this document can be advertised via
   BGP-LS [RFC7752] using existing BGP-LS TLVs.

   The ELC Flag included in the OSPFv2 Extended Prefix TLV and the
   OSPFv3 PrefixOptions, as defined in Section 3, is advertised using the Prefix Attribute Flags TLV (TLV 1170) of the BGP-LS IPv4/IPv6
   Prefix NLRI Attribute as defined
   in section 2.3.2 of [I-D.ietf-idr-bgp-ls-segment-routing-ext].

   The ERLD MSD-type introduced for OSPF in Section 4 ERLD-MSD is advertised using the Node MSD TLV (TLV 266) of the BGP-LS Node NLRI Attribute as defined in section 3 of
   [I-D.ietf-idr-bgp-ls-segment-routing-msd].

6.  Acknowledgements

   The authors would like to thank Yimin Shen, George Swallow, Acee
   Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura , Bruno
   Decraene and Carlos Pignataro for their valuable comments.

7.  IANA Considerations

   This document requests

   Early allocation has been done by IANA to allocate one flag from for this document as follows:

      - Flag 0x20 in the OSPFv2 Extended Prefix TLV Flags registry:

      0x20 - registry has
      been assigned to the E-Flag (ELC Flag)

   This document requests Flag).  IANA is asked to allocate one flag from update
      the OSPFv3 registry to reflect the name used in this document: E-Flag
      (ELC Flag).

      - Bit 0x04 in the "OSPFv3 Prefix Options registry:

      0x04 - (8 bits)" registry has
      been assigned to the E-Flag (ELC Flag)

8. Flag).  IANA is asked to update
      the registry to reflect the name used in this document: E-Flag
      (ELC Flag).

7.  Security Considerations

   The

   This document specifies the ability to advertise additional node
   capabilities using OSPF and BGP-LS.  As such, the security
   considerations as described in [RFC7770] [RFC5340], [RFC7770], [RFC7752],
   [RFC7684], [RFC8476], [RFC8662],
   [I-D.ietf-idr-bgp-ls-segment-routing-ext] and
   [I-D.ietf-mpls-spring-entropy-label]
   [I-D.ietf-idr-bgp-ls-segment-routing-msd] are applicable to this
   document.

   Incorrectly setting the E flag (ELC capable) (during during origination,
   inter-area advertisement propagation or redistribution)
   redistribution may lead to black-holing of the traffic on the egress
   node.

   Incorrectly setting of the ERLD value may lead to poor load-balancing or no load-
   balancing of the traffic.

9.

8.  Contributors

   The following people contributed to the content of this document and
   should be considered as co-authors:

      Gunter Van de Velde (editor)
      Nokia
      Antwerp
      BE

      Email: gunter.van_de_velde@nokia.com

      Wim Henderickx
      Nokia
      Belgium

      Email: wim.henderickx@nokia.com

      Keyur Patel
      Arrcus
      USA

      Email: keyur@arrcus.com

9.  Acknowledgements

   The authors would like to thank Yimin Shen, George Swallow, Acee
   Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura , Bruno
   Decraene and Carlos Pignataro for their valuable comments.

10.  References

10.1.  Normative References

   [BCP14]    , <https://tools.ietf.org/html/bcp14>.

   [I-D.ietf-idr-bgp-ls-segment-routing-ext]
              Previdi, S., Talaulikar, K., Filsfils, C., Gredler, H.,
              and M. Chen, "BGP Link-State extensions for Segment
              Routing", draft-ietf-idr-bgp-ls-segment-routing-ext-16
              (work in progress), June 2019.

   [I-D.ietf-idr-bgp-ls-segment-routing-msd]
              Tantsura, J., Chunduri, U., Talaulikar, K., Mirsky, G.,
              and N. Triantafillis, "Signaling MSD (Maximum SID Depth)
              using Border Gateway Protocol Link-State", draft-ietf-idr-
              bgp-ls-segment-routing-msd-09 - Link State", draft-ietf-
              idr-bgp-ls-segment-routing-msd-16 (work in progress), October
              2019.
              March 2020.

   [I-D.ietf-isis-mpls-elc]
              Xu, X., Kini, S., Psenak, P., Filsfils, C., Litkowski, S.,
              and M. Bocci, "Signaling Entropy Label Capability and
              Entropy Readable Label Depth Using IS-IS", draft-ietf-
              isis-mpls-elc-10
              isis-mpls-elc-11 (work in progress), October 2019.

   [I-D.ietf-mpls-spring-entropy-label]
              Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
              Shakir, R., and J. Tantsura, "Entropy label for SPRING
              tunnels", draft-ietf-mpls-spring-entropy-label-12 (work in
              progress), July 2018.

   [I-D.ietf-spring-segment-routing-mpls]
              Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-22
              (work in progress), May 2019. March 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>.

   [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>.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, DOI 10.17487/RFC6790, November 2012,
              <https://www.rfc-editor.org/info/rfc6790>.

   [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>.

   [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>.

   [RFC7770]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
              February 2016, <https://www.rfc-editor.org/info/rfc7770>.

   [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>.

   [RFC8476]  Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
              "Signaling Maximum SID Depth (MSD) Using OSPF", RFC 8476,
              DOI 10.17487/RFC8476, December 2018,
              <https://www.rfc-editor.org/info/rfc8476>.

   [RFC8662]  Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
              Shakir, R., and J. Tantsura, "Entropy Label for Source
              Packet Routing in Networking (SPRING) Tunnels", RFC 8662,
              DOI 10.17487/RFC8662, December 2019,
              <https://www.rfc-editor.org/info/rfc8662>.

10.2.  Informative References

   [I-D.ietf-ospf-segment-routing-extensions]

   [RFC8660]  Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing with the MPLS Data Plane", RFC 8660,
              DOI 10.17487/RFC8660, December 2019,
              <https://www.rfc-editor.org/info/rfc8660>.

   [RFC8665]  Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
              H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", draft-ietf-ospf-segment-
              routing-extensions-27 (work in progress), RFC 8665,
              DOI 10.17487/RFC8665, December 2019,
              <https://www.rfc-editor.org/info/rfc8665>.

   [RFC8666]  Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions
              for Segment Routing", RFC 8666, DOI 10.17487/RFC8666,
              December 2018. 2019, <https://www.rfc-editor.org/info/rfc8666>.

Authors' Addresses

   Xiaohu Xu
   Alibaba Inc

   Email: xiaohu.xxh@alibaba-inc.com

   Sriganesh Kini

   Email: sriganeshkini@gmail.com

   Peter Psenak
   Cisco Systems, Inc.
   Eurovea Centre, Central 3
   Pribinova Street 10
   Bratislava  81109
   Slovakia

   Email: ppsenak@cisco.com
   Clarence Filsfils
   Cisco Systems, Inc.
   Brussels
   Belgium

   Email: cfilsfil@cisco.com

   Stephane Litkowski
   Cisco Systems, Inc.
   La Rigourdiere
   Cesson Sevigne
   France

   Email: slitkows@cisco.com

   Matthew Bocci
   Nokia
   Shoppenhangers Road
   Maidenhead, Berks
   UK

   Email: matthew.bocci@nokia.com