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Network Working Group                                        J. Snijders
Internet-Draft                                        Atrato IP Networks
Intended status: Informational                            August 7, 2013
Expires: February 8, 2014


      The "import-via" and "export-via" attributes in RPSL Policy
                             Specifications
                       draft-snijders-rpsl-via-01

Abstract

   This document defines two attributes in the aut-num Class which can
   be used in RPSL policy specifications to publish desired routing
   policy regarding non-adjacent networks.

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 February 8, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Notational Conventions  . . . . . . . . . . . . . . . . . . . . 3
   3.  Background  . . . . . . . . . . . . . . . . . . . . . . . . . . 3
   4.  Import and Export Via Syntax and Semantics  . . . . . . . . . . 4
   5.  Example Usage . . . . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 6
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 6
   Appendix A.  Grammar Rules  . . . . . . . . . . . . . . . . . . . . 7
   Appendix B.  Document Change Log  . . . . . . . . . . . . . . . . . 7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 7



































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1.  Introduction

   The Routing Policy Specification Language [RFC4012] allows operators
   to specify routing policies regarding directly adjacent networks
   through various import and export attributes.  These attributes only
   apply to directly adjacent networks.

   This document proposes to extend RPSL according to the following
   goals and requirements:

   o  Provide a way to describe what an adjacent network could use as
      routing policy towards its adjacent networks.

   o  The extension should be backward compatible with minimal impact on
      existing tools and processes, following Section 10.2 of [RFC2622].

   The addition of the 'via-import' and 'via-export' attributes in the
   aut-num Class will especially help participants of Multi-Lateral
   Peering services to inform the intermediate autonomous system what
   routing policy should be applied towards other participants.


2.  Notational Conventions

   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
   [RFC2119].


3.  Background

   The via keyword specifically benefits operators whom were assigned a
   32 bit AS Number and transit providers when participating in Multi-
   Lateral Peering Agreements facilitated by a Route Server.

   Often Route Server operators overload BGP Communities [RFC1997]) to
   facilitate signalling of desired routing policy between the
   participants and the Route Server.  Because BGP Communities have a
   length of 32 bit, it is not possible to signal a 32 bit AS Number
   coupled with an action.  In practise this means Route Server
   participants whom use a 32 bit AS Number cannot specifically be
   included or excluded during path distribution calculations on the
   Route Server unless a mapping system is applied.

   Transit providers often uphold a routing policy which intents that
   the transit provider does not want to exchange paths with its
   downstream customers through Route Servers.  The via keyword allows



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   transit providers to participate in Multi-Lateral Peering services
   while instructing Route Server operators through a simple routing
   policy specification that paths should not be distributed to
   downstream customers and reducing the likelyhood of Path Hiding on
   the Route Server.


4.  Import and Export Via Syntax and Semantics

   The two attributes can be used within the aut-num class.

      import-via:

      export-via:

   The syntax for these attributes is as follows:

   Attribute  Value                                         Type
   import-via [protocol <protocol-1>] [into <protocol-2>]   optional,
              [afi <afi-list>]                              multi-valued
              <mp-peering-1>
              from <mp-peering-2> [action <action-1>; ... <action-N>;]
              . . .
              &#65533;mp-peering-3>
              from <mp-peering-M> [action <action-1>; ... <action-N>;]
              accept <mp-filter> [;]

   export-via [protocol <protocol-1>] [into <protocol-2>]   optional,
              [afi <afi-list>]                              multi-valued
              <mp-peering-1>
              to <mp-peering-2> [action <action-1>; ... <action-N>;]
              . . .
              <mp-peering-3>
              to <mp-peering-M> [action <action-1>; ... <action-N>;]
              announce <mp-filter> [;]


                                 Figure 1

   The import-via and export-via attributes are optional, and should be
   ignored by implementations which do not support interpretation of
   those attributes.  The syntax closely mimicks the mp-import and mp-
   export attributes described in Section 2.5 of [RFC4012], with the
   exception that before the "from" and "to" keywords an &klt;mp-
   peering> is defined to indicate the common AS between two non-
   adjacent networks.

   In the above example <peering-1> and <peering-3> are directly



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   adjacent networks, for instance a Multi-Lateral Peering service.
   <peering-2> is a non-adjacent network.


5.  Example Usage

   Putting it all together:

      aut-num: AS5580
      import-via: AS6777
                   from AS15562
                   action pref = 2;
                   accept AS-SNIJDERS
      export-via: AS6777
                   to AS15562 action community.={5580:40};
                   announce AS-ATRATO
      import-via: AS5580:AS-ROUTESERVERS
                   from AS5580:AS-CUSTOMERS
                   accept NOT ANY
      export-via: AS5580:AS-ROUTESERVERS
                   to AS5580:AS-CUSTOMERS announce NOT ANY
      import-via: AS6777
                   from AS4247483647
                   accept AS4247483647
      export-via: AS6777
                   to AS4247483647 action community.={5580:40};
                   announce AS-ATRATO

                                 Figure 2

   In the above examples AS5580 and AS15562 are Route Server
   participants.  AS4247483647 is a participant whom has been assigned a
   32 bit AS Number.  AS6777 functions as a Route Server
   [I-D.ietf-idr-ix-bgp-route-server] and AS-SET AS5580:AS-ROUTESERVERS
   contains a list of Route Server AS Numbers.  AS-SET AS5580:AS-
   CUSTOMERS contains a list of downstream transit customers from
   AS5580.

   The intention of the above policy would be to enable the exchange of
   NLRI's through AS6777 with two parties: AS15562 and AS4247483647, yet
   prevent the Route Server from distributing NLRI's announced by AS5580
   towards customers of said network.  Publishing the policy that AS5580
   will not accept customer routes through the Route Server can help
   counteract the "path hiding" phenomenon as described in Section 2.3.1
   of [I-D.ietf-idr-ix-bgp-route-server], as the Route Server now is
   informed which NLRI's should not be considered in the best path
   selection process.




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6.  Security Considerations

   There are no security considerations for this specification.


7.  IANA Considerations

   This document has no IANA actions.


8.  Acknowledgments

   The authors would like to thank Remko van Mook for confirming that
   'via' is a better keyword than 'through' or 'thru', Nick Hilliard for
   his unparalleled support and Jeffrey Haas for providing historic
   perspective.


9.  References

9.1.  Normative References

   [RFC1997]  Chandrasekeran, R., Traina, P., and T. Li, "BGP
              Communities Attribute", RFC 1997, August 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2622]  Alaettinoglu, C., Villamizar, C., Gerich, E., Kessens, D.,
              Meyer, D., Bates, T., Karrenberg, D., and M. Terpstra,
              "Routing Policy Specification Language (RPSL)", RFC 2622,
              June 1999.

   [RFC4012]  Blunk, L., Damas, J., Parent, F., and A. Robachevsky,
              "Routing Policy Specification Language next generation
              (RPSLng)", RFC 4012, March 2005.

9.2.  Informative References

   [I-D.ietf-idr-ix-bgp-route-server]
              Jasinska, E., Hilliard, N., Raszuk, R., and N. Bakker,
              "Internet Exchange Route Server",
              draft-ietf-idr-ix-bgp-route-server-02 (work in progress),
              February 2013.







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Appendix A.  Grammar Rules

   HERE BE DRAGONS


Appendix B.  Document Change Log

   (RFC Editor - this Appendix can be removed upon publication as RFC)

   1.  Initial document.

   2.  Changes to draft-snijders-rpsl-via-01.txt

       A.  Moved from adding a new RPSL keyword to a new RPSL attribute
           to improve backwards compatibility.


Author's Address

   Job Snijders
   Atrato IP Networks
   Tupolevlaan 103a
   Schiphol-Rijk  1119 PA
   NL

   Email: job.snijders@atrato.com

























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