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Versions: 00

Network Working Group                                        B. Decraene
Internet-Draft                                                    Orange
Intended status: Standards Track                                S. Hegde
Expires: October 8, 2021                           Juniper Networks Inc.
                                                           April 6, 2021


                             LAG indication
                  draft-decraene-lsr-lag-indication-00

Abstract

   This document defines a new link flag to advertise that a layer-three
   link is composed of multiple layer-two sub-links, such as when this
   link is a Link Aggregation Group (LAG).  This allows a large single
   flow (an elephant flow) to be aware that the link capacity will be
   lower than expected as this single flow is not load-balanced across
   the multiple layer-two sub-links.  A path computation logic may use
   that information to route that elephant flow along a different path.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on October 8, 2021.

Copyright Notice

   Copyright (c) 2021 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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   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
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Protocol extensions . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  IS-IS extension . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  OSPF extension  . . . . . . . . . . . . . . . . . . . . .   3
   3.  Operational considerations  . . . . . . . . . . . . . . . . .   3
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     4.2.  OSPF  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Appendix A.  Changes / Author Notes . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   An IP link may be composed a multiple layer two sub-links not visible
   to the IGP routing topology.  When traffic crossing that IP link is
   load-balanced on a per flow basis, a large elephant flow will only
   benefit from the capacity of a single sub-link.  This is an issue for
   the routing logic which only see the aggregated bandwidth of the IP
   link, and hence may incorrectly route a large flow over a link which
   is incapable of transporting that flow.

   This document defines a new link flag to signal that an IP link is a
   Link Aggregate Group composed of multiple layer two sub-links.  This
   flag may be automatically be set by routing nodes connected to such
   links, without requiring manual tagging by the network operator.  A
   path computation logic such as a PCE or a CSPF computation on the
   ingress, may use that information to avoid such links for elephant
   flows.

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 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
   appear in all capitals, as shown here.



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2.  Protocol extensions

2.1.  IS-IS extension

   To advertise that a layer-three link is composed of multiple layer-
   two sub-components this document defines a new bit in the IS-IS link-
   attribute sub-TLV RFC 5029 [RFC5029].

   L2 LAG (Link Aggregation Group) TBD1.  When set, this layer-three
   link is composed of multiple layer-two sub-components performing per
   flow load balancing.

2.2.  OSPF extension

   To advertise that a layer-three link is composed of multiple layer-
   two sub-components this document defines a new bit in the OSPF Link
   Attributes Bits TLV [I-D.ietf-lsr-dynamic-flooding].

   L2 LAG (Link Aggregation Group) TBD2.  When set, this layer-three
   link is composed of multiple layer-two sub-components performing per
   flow load balancing.

3.  Operational considerations

   A node supporting this extension SHOULD automatically advertise the
   L2 LAG flag for IP links composed of multiple layer-two sub-
   components.  Configuration knob MAY be provided to override this
   default.

   In order to handle nodes not supporting this extension, network
   operator may need to use an admin group (color) [RFC5305] [RFC7308]
   in order to flag those links on legacy nodes.

4.  IANA Considerations

4.1.  IS-IS

   IANA is requested to allocate one bit value from the registry: link-
   attribute bit values for sub-TLV 19 of TLV 22 (Extended IS
   reachability TLV).

                   Value   Name
                   ----    --------------------------------
                   TBD1    L2 LAG (Link Aggregation Group)

                                 Figure 1





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4.2.  OSPF

   IANA is requested to allocate one bit number from the registry: OSPF
   Link Attributes Sub-TLV Bit Values.

                Bit Number   Description
                ----------   --------------------------------
                TBD2         L2 LAG (Link Aggregation Group)

                                 Figure 2

5.  Security Considerations

   This extension advertises additional information and capabilities
   about a link.

   An attacker having access to this information would gain knowledge
   that this link has sub components and that sending a large amount of
   traffic via a single flow (hence not a DOS) is more likely to
   overload that sub-component.  On the other hand, this overloading
   would be limited to this specific sub-component and hence not affect
   other sub-component.

   An attacker been capable of adding this information may gain ability
   to change the routing of some flow crossing the links, typically
   large elephant flows specifically configured to avoid such link.

   An attacker been capable of removing this information may gain the
   ability to change the routing and direct a large elephant flow on
   this link, which would overload a sub component of this link and
   likely create packet drop for this specific flow.

   However, in those two cases, the attacker would equally have the
   capability to change other routing information such as the link
   metric, link usability and any link characteristics.  Hence this new
   information does not add new security considerations.  Besides, as
   with others TLV advertisements, the use of a cryptographic
   authentication as defined in [RFC5304] or [RFC5310] allows the
   authentication of the peer and the integrity of the message and
   remove the ability for an attacker to modify such information.

   .

6.  Acknowledgments

   TBD.





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7.  References

7.1.  Normative References

   [I-D.ietf-lsr-dynamic-flooding]
              Li, T., Psenak, P., Ginsberg, L., Chen, H., Przygienda,
              T., Cooper, D., Jalil, L., Dontula, S., and G. Mishra,
              "Dynamic Flooding on Dense Graphs", draft-ietf-lsr-
              dynamic-flooding-08 (work in progress), December 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>.

   [RFC5029]  Vasseur, JP. and S. Previdi, "Definition of an IS-IS Link
              Attribute Sub-TLV", RFC 5029, DOI 10.17487/RFC5029,
              September 2007, <https://www.rfc-editor.org/info/rfc5029>.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October
              2008, <https://www.rfc-editor.org/info/rfc5304>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310, February
              2009, <https://www.rfc-editor.org/info/rfc5310>.

   [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>.

7.2.  Informative References

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC7308]  Osborne, E., "Extended Administrative Groups in MPLS
              Traffic Engineering (MPLS-TE)", RFC 7308,
              DOI 10.17487/RFC7308, July 2014,
              <https://www.rfc-editor.org/info/rfc7308>.

Appendix A.  Changes / Author Notes

   [RFC Editor: Please remove this section before publication]

   00: Initial version.



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Authors' Addresses

   Bruno Decraene
   Orange

   Email: bruno.decraene@orange.com


   Shraddha Hegde
   Juniper Networks Inc.
   Exora Business Park
   Bangalore, KA  560103
   India

   Email: shraddha@juniper.net




































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