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Versions: (draft-snijders-grow-large-communities-usage) 00 01 02 03 04 05 06 07 RFC 8195

Global Routing Operations                                    J. Snijders
Internet-Draft                                                       NTT
Intended status: Informational                                M. Schmidt
Expires: June 10, 2017                                           i3D.net
                                                        December 7, 2016


                     Usage of Large BGP Communities
               draft-ietf-grow-large-communities-usage-01

Abstract

   Examples and inspiration for operators on how to use Large BGP
   Communities.

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 http://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 June 10, 2017.

Copyright Notice

   Copyright (c) 2016 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
   (http://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



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   to this document.  Code Components extracted from this document must
   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.  The Generic Design Pattern  . . . . . . . . . . . . . . . . .   3
     2.1.  Informational Communities . . . . . . . . . . . . . . . .   3
     2.2.  Action Communities  . . . . . . . . . . . . . . . . . . .   4
   3.  Examples of Informational Communities . . . . . . . . . . . .   4
     3.1.  Location  . . . . . . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  An ISO 3166-1 numeric function  . . . . . . . . . . .   4
       3.1.2.  An UNSD region function . . . . . . . . . . . . . . .   5
     3.2.  Relation  . . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  Combining Informational Communities . . . . . . . . . . .   6
   4.  Examples of Action Communities  . . . . . . . . . . . . . . .   6
     4.1.  Selective NO_EXPORT . . . . . . . . . . . . . . . . . . .   6
       4.1.1.  Peer ASN Based Selective NO_EXPORT  . . . . . . . . .   6
       4.1.2.  Location Based Selective NO_EXPORT  . . . . . . . . .   7
     4.2.  Selective AS_PATH Prepending  . . . . . . . . . . . . . .   7
       4.2.1.  Peer ASN Based Selective AS_PATH Prepending . . . . .   7
       4.2.2.  Location Based Selective AS_PATH Prepending . . . . .   8
     4.3.  Location based manipulation of LOCAL_PREF . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     8.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Large BGP Communities [I-D.ietf-idr-large-community] provide a
   mechanism to signal opaque information between Autonomous Systems.
   This document presents a set of examples on how Large BGP Communities
   could be implemented by an operator to achieve various goals.  This
   document draws from experience in Operational Communities such as
   NANOG [1] and NLNOG [2].

   The opaque nature of Large BGP Communities allows for rapid
   deployment of new features or changes to the product.  Operators are
   encouraged to publicly publish an up to date version of their routing
   policy in which they document what each Large BGP Community means.





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2.  The Generic Design Pattern

   Large BGP Communities are composed of a 4-octet Global Administrator
   field followed by two 4-octet Local Data fields.  The design pattern
   described in this document uses a "ASN:Function:Parameter"-approach
   to fill the three fields.

   In deployments of both BGP Communities [RFC1997] and Large BGP
   Communities, two categories of Communities are recognised:

   o  Informational Communities

   o  Action Communities

   For each context ideas are provided regarding the contents of each of
   the three fields in Large BGP Communities.

   Throughout the document a topology of four Autonomous Systems is used
   to illustrate the usage of Communities in the following
   configuration:

           AS 65551
               |
               ^
               |
           AS 64497
             /  \
            ^    \
           /      ^
      AS 64498     \
          |        |
          `<->- AS 64499

   AS 64497 obtains transit services from AS 65551.  AS 64497 provides
   transit services to both AS 64498 and AS 64499.  AS 64498 and AS
   64499 maintain a peering relation in which they only exchange their
   customer routes.

2.1.  Informational Communities

   Informational Communites serve as markers regarding the origin of the
   route announcement, the relation with the EBGP neighbor or for
   instance the intended propagation audience.  Informational
   Communities also assist in network operations such as debugging.

   The Global Administrator field is set to the ASN which is marking the
   routes with the Informational Communities.  As an example: on a route
   which AS 64497 announces to AS 64498, AS 64497 might add the Large



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   BGP Community 64497:100:31 to signal to AS 64498 that the route was
   learned in the Netherlands.

   In general the intended audience of Informational Communities are
   downstream networks, but any adjacent Autonomous System could benefit
   from receiving these communities.

2.2.  Action Communities

   Action Communities are attached to routes to request non-default
   behaviour in an adjacent Autonomous System.  For instance, Action
   Communities are used to change the route's propagation
   characteristics, the route's LOCAL_PREF value or the amount of
   AS_PATH prepends that should be added when exporting or importing a
   route.

   The Global Administrator field is set to the ASN which is expected to
   perform a non-default action upon receiving the route.  For instance,
   if AS 64499 would want to request AS 64497 to lower the
   LOCAL_PREFERENCE below the default, AS 64499 could tag the route with
   64497:20:50.

   In general the intended audience of Action Communities is an upstream
   provider.

3.  Examples of Informational Communities

3.1.  Location

   AS 64497 can inform its downstream networks about the geographical
   entity where AS 64497 learned a route by marking the route with Large
   BGP Communities following one or a combination of the following
   schemes.

3.1.1.  An ISO 3166-1 numeric function

   AS 64497 could assign a value of 1 to the first Local Data field to
   designate the function of the parameter in the second Local Data
   field as ISO-3166-1 numeric country identifiers.












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    +---------------------+-------------------------------------------+
    | Large BGP Community | Meaning                                   |
    +---------------------+-------------------------------------------+
    |     64497:1:528     | Route learned in Netherlands              |
    |     64497:1:392     | Route learned in Japan                    |
    |     64497:1:840     | Route learned in United States of America |
    +---------------------+-------------------------------------------+

     Example documentation for AS 64497 using Informational Communties
   describing the origin of routes using ISO 3166-1 numeric identifiers.

                     Table 1: Information: ISO 3166-1

3.1.2.  An UNSD region function

   AS 64497 could assign a value of 2 to the first Local Data field to
   designate the function of the parameter in the second Local Data
   field as an identifier for the macro geographical (continental)
   regions, geographical sub-regions, or selected economic and other
   groupings following a set of published identifiers by the United
   Nations Statistics Division [3].

          +---------------------+-------------------------------+
          | Large BGP Community | Meaning                       |
          +---------------------+-------------------------------+
          |      64497:2:2      | Route learned in Africa       |
          |      64497:2:9      | Route learned in Oceania      |
          |     64497:2:145     | Route learned in Western Asia |
          |     64497:2:150     | Route learned in Europe       |
          +---------------------+-------------------------------+

     Example documentation for AS 64497 using Informational Communties
   describing the origin of routes using numeric identifiers provided by
                        the UN Statistics Division.

                       Table 2: Information: Regions

3.2.  Relation

   AS 64497 could assign a value of 3 to the first Local Data field to
   designate that the second Local Data field contains an identifier
   showing the relation with the EBGP neighbor from whom the route was
   received.








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     +---------------------+-----------------------------------------+
     | Large BGP Community | Meaning                                 |
     +---------------------+-----------------------------------------+
     |      64497:3:1      | Route learned from a customer           |
     |      64497:3:2      | Route learned from a peering partner    |
     |      64497:3:3      | Route learned from an upstream provider |
     +---------------------+-----------------------------------------+

     Example documentation for AS 64497 using Informational Communties
       describing the relation with the ASN from which the route was
                                 received.

                      Table 3: Information: Relation

3.3.  Combining Informational Communities

   Multiple Informational Communities can be tagged on a route, for
   example: a route learned in the Netherlands from a customer can
   contain both 64497:1:528 and 64497:2:150 and 64497:3:1.

4.  Examples of Action Communities

4.1.  Selective NO_EXPORT

   As part of the commercial agreement between AS 64497 and AS 64498, AS
   64497 might offer AS 64498 certain BGP Traffic Engineering features
   such as selectively not export routes learned from 64498 to certain
   EBGP neighbors of AS 64497.

4.1.1.  Peer ASN Based Selective NO_EXPORT

   AS 64497 might assign function identifier 4 to allow preventing
   propagation of routes to the ASN listed in the second Local Data
   field.

         +---------------------+---------------------------------+
         | Large BGP Community | Meaning                         |
         +---------------------+---------------------------------+
         |     64497:4:2914    | Do not export route to AS 2914  |
         |     64497:4:7018    | Do not export route to AS 7018  |
         |    64497:4:65551    | Do not export route to AS 65551 |
         +---------------------+---------------------------------+

     Example documentation for AS 64497 offering Action Communties to
    limit propagation of routes based on the Peer ASN described in the
                               third field.

                    Table 4: Action: Peer ASN NO_EXPORT



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4.1.2.  Location Based Selective NO_EXPORT

   AS 64497 might assign function identifier 5 to allow its customers to
   request selectively not exporting routes on EBGP sessions within a
   certain geographical area.  This example follows the ISO 3166-1
   numeric encoding.

   +------------------+------------------------------------------------+
   |    Large BGP     | Meaning                                        |
   |    Community     |                                                |
   +------------------+------------------------------------------------+
   |   64497:5:528    | Do not export to EBGP neighbors in the         |
   |                  | Netherlands                                    |
   |   64497:5:392    | Do not export to EBGP neighbors in Japan       |
   |   64497:5:840    | Do not export to EBGP neighbors in United      |
   |                  | States of America                              |
   +------------------+------------------------------------------------+

     Example documentation for AS 64497 offering Action Communties to
     trigger NO_EXPORT on routes only when propagating the route to a
                       certain geographical region.

                   Table 5: Action: NO_EXPORT in Region

4.2.  Selective AS_PATH Prepending

   As part of the commercial agreement between AS 64497 and AS 64498, AS
   64497 might offer AS 64498 certain BGP Traffic Engineering features
   such as selectively prepending the AS_PATH with 64497's ASN to
   certain EBGP neighbors of AS 64497.

4.2.1.  Peer ASN Based Selective AS_PATH Prepending

   AS 64497 might assign function identifier 6 to allow prepending the
   AS_PATH on propagation of routes to the ASN listed in the second
   Local Data field.















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    +---------------------+------------------------------------------+
    | Large BGP Community | Meaning                                  |
    +---------------------+------------------------------------------+
    |     64497:6:2914    | Prepend 64497 once on export to AS 2914  |
    |     64497:6:7018    | Prepend 64497 once on export to AS 7018  |
    |    64497:6:65551    | Prepend 64497 once on export to AS 65551 |
    +---------------------+------------------------------------------+

     Example documentation for AS 64497 offering Action Communties to
   trigger prepending of the AS_PATH only when propagating the route to
                            a certain Peer ASN.

                   Table 6: Action: Prepend to Peer ASN

4.2.2.  Location Based Selective AS_PATH Prepending

   AS 64497 might assign function identifier 7 to allow prepending of
   the AS_PATH on propagation of routes to on any EBGP neighbor's
   interconnection in the geographical entity listed in the second Local
   Data field.  This example follows the ISO 3166-1 numeric regions
   codes in the Local Data 2 field.

   +------------------+------------------------------------------------+
   |    Large BGP     | Meaning                                        |
   |    Community     |                                                |
   +------------------+------------------------------------------------+
   |   64497:7:528    | Prepend once to EBGP neighbors in the          |
   |                  | Netherlands                                    |
   |   64497:7:392    | Prepend once to EBGP neighbors in Japan        |
   |   64497:7:840    | Prepend once to EBGP neighbors in United       |
   |                  | States of America                              |
   +------------------+------------------------------------------------+

     Example documentation for AS 64497 offering Action Communties to
   trigger prepending of the AS_PATH only when propagating the route to
                      a certain geographical region.

                    Table 7: Action: Prepend in Region

4.3.  Location based manipulation of LOCAL_PREF

   In some cases, it can be desirable for an autonomous system to allow
   adjacent Autonomous Systems to directly influence the degree of
   preference associated with a route, usually expressed within the
   LOCAL_PREF attribute.

   Furthermore, in the case of large networks spanning significant
   geography, it is often also useful to be able to extend this



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   capability and scope its effect to a geographic region.  This is a
   more powerful mechanism than AS_PATH prepending, but since degree of
   preference determines BGP route selection and thus onward
   advertisement, it can also be self-limiting in its scope.

   Since the LOCAL_PREF attribute which influences degree of preference
   is locally significant within each autonomous system, it is not
   usually practical or useful to compare LOCAL_PREF attribute values
   between autonomous systems.  Instead it can be useful to classify the
   major types of route likely to exist within an autonomous system's
   routing hierarchy and provide an ability to set one's route to that
   preference:

   o  A qualified customer route.  Usually the highest preference.

   o  A peer, or network-share, route.  A co-operating network provider
      engaged in a partnership for customer coverage ("peering").

   o  A last resort, or backup route.

   It is entirely possible that some providers may have more classes of
   route preference but it is possible to codify both the route
   preference class and the regional scope within the Local Data fields
   of the Large Community attribute.

   For example, AS64497 might establish the following function
   identifiers to set route preference class, which could allow pairing
   with a location or peer-based operand to determine scope.

       +----------+-----------------------------------------------+
       | Function | Preference Class                              |
       +----------+-----------------------------------------------+
       |    10    | Qualified customer route. Highest preference. |
       |    15    | Peering partner. Median preference.           |
       |    19    | Route of last resort. Lowest preference.      |
       +----------+-----------------------------------------------+

             Table 8: Action: Preference Function Identifiers

   Once established, these route preference setting functions can be
   linked with a scoping operand such as per-peer or per-location based
   identifiers in order to provide AS64497's customers with a
   comprehensive and rich toolset to influence route preference.








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   +--------------------+----------------------------------------------+
   |     Large BGP      | Meaning                                      |
   |     Community      |                                              |
   +--------------------+----------------------------------------------+
   |    64497:15:528    | Set as peer route in Netherlands             |
   |    64497:19:840    | Set as backup route in United States of      |
   |                    | America                                      |
   +--------------------+----------------------------------------------+

             Table 9: Action: Regional Preference Communities

   Since the degree of preference influences BGP best path selection
   (which in turn influences onward route propagation) Operators should
   take special care with a traffic engineering tool such as location
   based local preference influence (BGP Wedgies [RFC4264]).

5.  Security Considerations

   Network operators should note the recommendations in Section 11 of
   BGP Operations and Security [RFC7454].

6.  IANA Considerations

   None.

7.  Acknowledgements

   The authors would like to gratefully acknowledge the insightful
   comments, contributions, critique and support from John Heasley, Adam
   Chappell and Jonathan Stewart.

8.  References

8.1.  Normative References

   [I-D.ietf-idr-large-community]
              Heitz, J., Snijders, J., Patel, K., Bagdonas, I., and N.
              Hilliard, "BGP Large Communities", draft-ietf-idr-large-
              community-11 (work in progress), December 2016.

   [RFC1997]  Chandra, R., Traina, P., and T. Li, "BGP Communities
              Attribute", RFC 1997, DOI 10.17487/RFC1997, August 1996,
              <http://www.rfc-editor.org/info/rfc1997>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.



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   [RFC4264]  Griffin, T. and G. Huston, "BGP Wedgies", RFC 4264,
              DOI 10.17487/RFC4264, November 2005,
              <http://www.rfc-editor.org/info/rfc4264>.

   [RFC7454]  Durand, J., Pepelnjak, I., and G. Doering, "BGP Operations
              and Security", BCP 194, RFC 7454, DOI 10.17487/RFC7454,
              February 2015, <http://www.rfc-editor.org/info/rfc7454>.

8.2.  URIs

   [1] http://nanog.net

   [2] http://nlnog.net

   [3] http://unstats.un.org/unsd/methods/m49/m49regin.htm

Authors' Addresses

   Job Snijders
   NTT Communications
   Theodorus Majofskistraat 100
   Amsterdam  1065 SZ
   NL

   Email: job@ntt.net


   Martijn Schmidt
   i3D.net
   Rivium 1e Straat 1
   Capelle aan den IJssel  2909 LE
   NL

   Email: martijnschmidt@i3d.net

















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