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Network Working Group                                        J. Snijders
Internet-Draft                                         Hibernia Networks
Intended status: Informational                            March 10, 2014
Expires: September 11, 2014


      The "import-via" and "export-via" attributes in RPSL Policy
                             Specifications
                       draft-snijders-rpsl-via-03

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.

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   This Internet-Draft will expire on September 11, 2014.

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   described in the Simplified BSD License.




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Table of Contents

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

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 for network (A) to describe what an adjacent network
      (B) could use as routing policy towards its adjacent networks (C,
      D, E .. N).

   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 "import-via" and "export-via" 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].





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3.  Background

   The via keyword specifically benefits operators who 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 signaling 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 who 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 have a routing policy which states that the
   transit provider does not want to exchange paths with its downstream
   customers through Route Servers via public Internet Exchanges.  The
   import-via and export-via attributes allow 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 likelihood 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:


















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

5.  Example Usage

   Putting it all together:















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      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 who 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.

6.  Ambiguity Resolution

   The same peering can be covered by more than one "via" policy
   attribute or by a combination of multi-protocol policy attributes, or
   multi-protocol policy attributes (when specifying IPv4 unicast
   policy) and the previously defined IPv4 unicast policy attributes.
   In these cases, implementations should follow the specification-order
   rule as defined in Section 6.4 of RFC 2622 [1].  Operators should



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   take note that in order to break ambiguity, the action corresponding
   to the first peering specification is used.

   Consider the following example regarding ambiguity resolution.

    aut-num: AS5580
    export:     to AS6777 195.69.144.255 announce AS5580
    export-via: AS6777 195.69.144.255 to AS-AMS-IX-RS announce AS-ATRATO

                                 Figure 3

   As both policy specifications cover the same peering with AS6777,
   specification-order rule is used and Route Server AS6777
   195.69.144.255 should only accept AS5580, instead of AS-ATRATO, even
   though the export-via specification is more specific.  If the
   intended policy was to announce all routes which can be resolved
   through AS-ATRATO on this particular peering, the operator should
   have specified:

    aut-num: AS5580
    export-via: AS6777 195.69.144.255 to AS-AMS-IX-RS announce AS-ATRATO
    export:     to AS6777 195.69.144.255 announce AS5580

                                 Figure 4

7.  Security Considerations

   There are no security considerations for this specification.

8.  IANA Considerations

   This document has no IANA actions.

9.  Acknowledgments

   The author 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, Jeffrey Haas for providing historic
   perspective, David Croft and Martin Pels for nitpicking.

10.  References

10.1.  Normative References

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





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   [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.

10.2.  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.

Appendix A.  Grammar Rules

   Note that only 'via' specific grammar rules have been listed.
   Currently two routing registry whois daemons have support for the
   'via' attributes: IRRd 3.0.7 and RIPE Whois Server 1.71.


   %type <string> line_autnum
   %type <string> attr_autnum
   %type <string> attr_import_via
   %type <string> attr_export_via

   %token T_IV_KEY //*** import-via: ***
   %token T_EV_KEY //*** export-via: ***
   %token T_AFI T_PROTOCOL T_WORD T_INTO T_EXCEPT T_REFINE
   %token T_ACCEPT T_ANNOUNCE T_TO T_FROM T_PRNGNAME

   line_autnum: attr_autnum
       | attr_import_via
       | attr_export_via

   attr_import_via: T_IV_KEY attr_import_syntax

   attr_import_syntax: opt_protocol_from opt_protocol_into import_simple
       | opt_protocol_from opt_protocol_into afi_import_exp

   attr_export_via: T_EV_KEY attr_export_syntax

   attr_export_syntax: opt_protocol_from opt_protocol_into export_simple



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       | opt_protocol_from opt_protocol_into afi_export_exp

   opt_afi_specification:
       | T_AFI afi_list

   afi_list: afi_token
       | afi_list ',' afi_token

   afi_token: afi_name

   opt_protocol_from:
       | T_PROTOCOL T_WORD

   opt_protocol_into:
       | T_INTO T_WORD

   import_simple: opt_afi_specification import_factor

   export_simple: opt_afi_specification export_factor

   afi_import_exp: opt_afi_specification import_exp

   afi_export_exp: opt_afi_specification export_exp

   import_exp: import_term
       | import_term T_EXCEPT afi_import_exp
       | import_term T_REFINE afi_import_exp

   import_factor_list: import_factor ';'
       | import_factor_list import_factor ';'

   import_term: import_factor ';'
       | '{' import_factor_list '}'

   export_exp: export_term
       | export_term T_EXCEPT afi_export_exp
       | export_term T_REFINE afi_export_exp

   export_factor_list: export_factor ';'
       | export_factor_list export_factor ';'

   export_term: export_factor ';'
       | '{' export_factor_list '}'

   import_factor: import_peering_action_list T_ACCEPT filter

   export_factor: export_peering_action_list T_ANNOUNCE filter




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   peering: as_expression opt_router_expression \
               opt_router_expression_with_at
       | T_PRNGNAME

   // Below are two grammar rules that actually differ
   // from mp-import: + mp-export:

   import_peering_action_list: peering T_FROM peering opt_action
       | import_peering_action_list peering T_FROM peering opt_action

   export_peering_action_list: peering T_TO peering opt_action
       | export_peering_action_list peering T_TO peering opt_action


                                 Figure 5

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.

   3.  Changes to draft-snijders-rpsl-via-02.txt

       A.  Added grammar appendix.

       B.  Added section about Ambiguity Resolution.

   4.  Changes to draft-snijders-rpsl-via-03.txt

       A.  Updated current IRR implementations.

Author's Address

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

   Email: job.snijders@hibernianetworks.com





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