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BGP Link Bandwidth Extended Community
draft-ietf-idr-link-bandwidth-09

Document Type Active Internet-Draft (idr WG)
Authors Prodosh Mohapatra , Rex Fernando , Reshma Das , SATYA R MOHANTY , Mankamana Prasad Mishra , Rafal Jan Szarecki
Last updated 2024-09-17
Replaces draft-rfernando-idr-link-bandwidth
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draft-ietf-idr-link-bandwidth-09
Network Working Group                                       P. Mohapatra
Internet-Draft                                          Sproute Networks
Intended status: Standards Track                             R. Fernando
Expires: 20 March 2025                                     Cisco Systems
                                                             R. Das, Ed.
                                                  Juniper Networks, Inc.
                                                         S. Mohanty, Ed.
                                                                 Zscaler
                                                               M. Mishra
                                                           Cisco Systems
                                                           R.J. Szarecki
                                                              Google LLC
                                                       16 September 2024

                 BGP Link Bandwidth Extended Community
                    draft-ietf-idr-link-bandwidth-09

Abstract

   This document describes an application of BGP extended communities
   that allows a router to perform unequal cost load balancing.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

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 20 March 2025.

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Copyright Notice

   Copyright (c) 2024 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
   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
   2.  Link Bandwidth Extended Community . . . . . . . . . . . . . .   3
   3.  Protocol Procedures . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Sender (Originating Link Bandwidth Community) . . . . . .   4
     3.2.  Receiver (Receiving link bandwidth community) . . . . . .   4
     3.3.  Re-advertisement Procedures . . . . . . . . . . . . . . .   4
       3.3.1.  Re-advertisement with Next hop Self . . . . . . . . .   4
       3.3.2.  Re-advertisement with Next Hop Unchanged  . . . . . .   4
     3.4.  Link bandwidth community Arithmetic and BGP multipath . .   5
   4.  Error Handling  . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Document History  . . . . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Load balancing is a critical aspect of network design, enabling
   efficient utilization of available bandwidth and improving overall
   network performance.  Traditional equal-cost multi-path (ECMP)
   routing does not account for the varying capacities of different
   paths.  This document suggests that the external link bandwidth be
   carried in the network using one of two new extended communities
   [RFC4360] - the transitive and non-transitive link bandwidth extended
   community.  The Link Bandwidth Extended Community provides a
   mechanism for routers to advertise the bandwidth of their downstream
   path(s), facilitating maximum utilisation of network resources.

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2.  Link Bandwidth Extended Community

   The Link Bandwidth Extended Communities are defined as a BGP extended
   community that carries the bandwidth information of a router,
   represented by BGP Protocol Next Hop, connecting to remote network.
   This community can be used to inform other routers about the
   available bandwidth on trough a given route.

   The Link bandwidth extended communities can be either transitive or
   non-transitive.  Therefore the value of the high-order octet of the
   extended Type Field can be 0x00 or 0x40 respectively.  The value of
   the low-order octet of the extended type field for this communities
   is 0x04.  The value of the Global Administrator subfield in the Value
   Field SHOULD represent the Autonomous System of the router that
   attaches the Link Bandwidth Community, but in can be set to any
   2-byte value.  If four octet AS numbering scheme is used [RFC6793],
   AS_TRANS should be used in the Global Administrator subfield.  The
   bandwidth of the link is expressed as 4 octets in [IEEE.754-2019]
   floating point format, units being bytes (not bits!) per second.  It
   is carried in the Local Administrator subfield of the Value Field.

    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=0x00/0x40   | SubType= 0x04 |       AS Number          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                    Link Bandwidth Value                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

    Type:   1-octet field MUST be set to 0x00 or 0x40
            to indicate transitive/non-transitive.

    SubType: 1-octet field MUST be set to 0x04
             to indicate 'Link-Bandwidth'.

    Global Administrator sub-field:
             2-octet represent the Autonomous System.

    Local Administrator sub-field:
             Bandwidth value (bytes per sec) encoded as 4 octets
             in IEEE floating point format.

                Figure 1: Link Bandwidth Extended Community

3.  Protocol Procedures

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3.1.  Sender (Originating Link Bandwidth Community)

   An originator of the link bandwidth community SHOULD be able to
   originate either a transitive or a non-transitive link bandwidth
   extended community.  Implementation SHOULD provide configuration to
   set the transitivity type of the link bandwidth community, as well as
   Global Administrator filed value and bandwidth value in (Local
   Administrator filed), trough local policy.  No more than one link
   bandwidth extended community SHALL be attached to a route.

   An originator can attach link bandwidth community to BGP path in
   egress processing to adj-RIB-out only or in ingress processing in
   which case link bandwidth community is present in Local-RIB.

   Note: Implementation MAY provide configuration option (knob) to allow
   sending non-transitive link bandwidth extended community on external
   BGP sessions.

3.2.  Receiver (Receiving link bandwidth community)

   A BGP receiver MUST be able to process link bandwidth community of
   both transitive or non-transitive type.  The receiver MUST NOT flap
   or treat the route as malformed based on the transitivity of the link
   bandwidth community and/or BGP session type (internal vs.  external).

   Note: Implementation MAY provide configuration option (knob) to
   accept non-transitive link bandwidth extended community from external
   BGP sessions.

3.3.  Re-advertisement Procedures

3.3.1.  Re-advertisement with Next hop Self

   When a BGP speaker re-advertises a route with the Link Bandwidth
   Extended Community and sets the next hop to itself, it SHOULD follow
   the same procedures as outlined in Section 3.1.

   In the absence of any import or export policies that alter the Link
   Bandwidth Extended Community, any received Link Bandwidth extended
   community on the route will be re-advertised unchanged, in accordance
   with standard BGP procedures.

3.3.2.  Re-advertisement with Next Hop Unchanged

   A BGP speaker that receives a route with link bandwidth community,
   re-advertises or reflects the same without changing its next hop
   SHOULD NOT change the link bandwidth extended community in any way.

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3.4.  Link bandwidth community Arithmetic and BGP multipath

   In a BGP multipath ECMP environment, the value of the link bandwidth
   community that is sent or re-advertised may be calculated based on
   the link bandwidth communities of the routes contributing to
   multipath in the Local Routing Information Base (Local-RIB).  This
   topic is beyond the scope of this document.

4.  Error Handling

   If a receiver receives a route with more than one Link Bandwidth
   Extended Community, it SHOULD:

      Prefer the lowest value of the attached link bandwidth community
      (Irrespective of the transitivity)

      Prefer the transitive Link Bandwidth Extended Community when
      choosing between transitive and non-transitive types that have the
      same value

   Implementations MAY provide configuration options (knobs) to change
   the above preference.

5.  Document History

   The BGP Link Bandwidth Extended Community has evolved over several
   versions of the IETF draft.  In the earlier versions up to draft-
   ietf-idr-link-bandwidth-08, only the non-transitive version of the
   link bandwidth extended community was supported.  However, starting
   from draft-ietf-idr-link-bandwidth-09, both transitive and non-
   transitive versions of the link bandwidth extended community are
   supported.

   An old sender/receiver is a BGP speakers either use procedures upto
   draft (https://datatracker.ietf.org/doc/html/draft-ietf-idr-link-
   bandwidth-08) or any undocumented behavior for link bandwidth
   extended community.

   A new sender/receiver is a BGP speaker that implements procedures
   specified in this document.

   Receiving speaker needs to be upgraded to support the procedures
   defined in this document to provide full interop with both transitive
   and non-transitive versions of LBW.  In order to keep changes to
   procedures simple, it is not a goal to provide interop between old
   Receiver and new Sender.

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6.  IANA Considerations

   This document defines a specific application of the two-octet AS
   specific extended community.  IANA is requested to assign a sub- type
   value of 0x04 for the link bandwidth extended community.

       Name                                           Value
       ----                                           -----
       non-transitive Link Bandwidth Ext. Community  0x4004

       Name                                           Value
       ----                                           -----
       transitive Link Bandwidth Ext. Community       0x0004

7.  Security Considerations

   There are no additional security risks introduced by this design.

8.  Contributors

   Kaliraj Vairavakkalai
   Juniper Networks, Inc.
   1133 Innovation Way,
   Sunnyvale, CA 94089
   United States of America
   Email: kaliraj@juniper.net

   Natrajan Venkataraman
   Juniper Networks, Inc.
   1133 Innovation Way,
   Sunnyvale, CA 94089
   United States of America
   Email: natv@juniper.net

9.  Acknowledgments

   The authors would like to thank Yakov Rekhter, Srihari Sangli and Dan
   Tappan for proposing unequal cost load balancing as one possible
   application of the extended community attribute.

   The authors would like to thank Bruno Decraene, Robert Raszuk, Joel
   Halpern, Aleksi Suhonen, Randy Bush, Jeff Haas and John Scudder for
   their comments and contributions.

10.  Normative References

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   [IEEE.754-2019]
              IEEE, "IEEE Standard for Floating-Point Arithmetic", 22
              July 2019, <https://ieeexplore.ieee.org/document/8766229>.

   [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>.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, DOI 10.17487/RFC4360,
              February 2006, <https://www.rfc-editor.org/info/rfc4360>.

   [RFC6793]  Vohra, Q. and E. Chen, "BGP Support for Four-Octet
              Autonomous System (AS) Number Space", RFC 6793,
              DOI 10.17487/RFC6793, December 2012,
              <https://www.rfc-editor.org/info/rfc6793>.

Authors' Addresses

   Pradosh Mohapatra
   Sproute Networks
   Email: pradosh@sproute.com

   Rex Fernando
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA 95134
   United States of America
   Email: rex@cisco.com

   Reshma Das (editor)
   Juniper Networks, Inc.
   1133 Innovation Way,
   Sunnyvale, CA 94089
   United States of America
   Email: dreshma@juniper.net

   Satya Mohanty (editor)
   Zscaler
   120 Holger Way,
   San Jose, CA 95134
   United States of America
   Email: smohanty@zscaler.com

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   Mankamana Mishra
   Cisco Systems
   821 alder drive,
   Milpitas, CA 95035
   United States of America
   Email: mankamis@cisco.com

   Rafal Jan Szarecki
   Google LLC
   1160 N Mathilda Ave,,
   Sunnyvale, CA 94089
   United States of America
   Email: rszarecki@gmail.com

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