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Versions: (draft-petrie-grow-mrt-add-paths) 00 01 02 03 RFC 8050

Global Routing Operations                                      C. Petrie
Internet-Draft                                                  RIPE NCC
Intended status: Standards Track                                 T. King
Expires: July 18, 2017                                            DE-CIX
                                                        January 14, 2017


 Multi-Threaded Routing Toolkit (MRT) Routing Information Export Format
                  with BGP Additional Paths Extensions
                    draft-ietf-grow-mrt-add-paths-03

Abstract

   This document updates the Multi-threaded Routing Toolkit (MRT) export
   format for Border Gateway Protocol (BGP) routing information by
   extending it to support the Advertisement of Multiple Paths in BGP
   extensions.

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 July 18, 2017.

Copyright Notice

   Copyright (c) 2017 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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   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Rationale . . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  MRT Subtypes for Types BGP4MP/BGP4MP_ET . . . . . . . . . . .   3
   4.  MRT Subtypes for Type TABLE_DUMP_V2 . . . . . . . . . . . . .   3
     4.1.  AFI/SAFI specific RIB Subtypes  . . . . . . . . . . . . .   3
     4.2.  RIB_GENERIC_ADDPATH Subtype . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
     5.1.  BGP4MP/BGP4MP_ET Subtype codes: . . . . . . . . . . . . .   4
     5.2.  TABLE_DUMP_V2 Subtype codes:  . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     7.2.  URIs  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   The MRT record format [RFC6396] was developed to provide researchers
   and engineers a means to encapsulate, export, and archive routing
   protocol transactions and routing information base snapshots.

   The Advertisement of Multiple Paths in BGP [RFC7911] defines a BGP
   extension to allow the advertisement of multiple paths for the same
   address prefix without the new paths implicitly replacing any
   previous ones.

   This document contains an optional extension to the MRT format
   [RFC6396] and introduces additional definitions of MRT subtype fields
   to permit representation of multiple path advertisements [RFC7911].

2.  Rationale

   MRT parsers are usually stateless.  In order to parse BGP messages
   which contain data structures that depend on the capabilities
   negotiated during the BGP session setup, the so-called MRT subtypes
   are utilized.  The Advertisement of Multiple Path [RFC7911] extension
   for BGP alters the encoding of the BGP NLRI format for withdraws and
   announcements.  Therefore new BGP4MP/BGP4MP_ET subtypes as defined in
   [RFC6396] are required to signal to a MRT parser how to parse the
   NLRI.

   In section 4.3 [RFC6396] of the MRT specification RIB subtypes are
   specified.  Prefix length and prefix fields are encoded in the same



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   manner as the BGP NLRI encoding.  In order to support path identifier
   information as defined in [RFC7911] new subtypes need to be added.

   The following two sections define the required subtypes.

3.  MRT Subtypes for Types BGP4MP/BGP4MP_ET

   This document defines the following new Subtypes:

   o  BGP4MP_MESSAGE_ADDPATH

   o  BGP4MP_MESSAGE_AS4_ADDPATH

   o  BGP4MP_MESSAGE_LOCAL_ADDPATH

   o  BGP4MP_MESSAGE_AS4_LOCAL_ADDPATH

   The fields of these message types are identical to the equivalent
   non-additional-path versions specified in section 4.4 [RFC6396].
   These enhancements continues to encapsulate the entire BGP message in
   the BGP message field.

4.  MRT Subtypes for Type TABLE_DUMP_V2

   This document defines the following new Subtypes:

   o  RIB_IPV4_UNICAST_ADDPATH

   o  RIB_IPV4_MULTICAST_ADDPATH

   o  RIB_IPV6_UNICAST_ADDPATH

   o  RIB_IPV6_MULTICAST_ADDPATH

   o  RIB_GENERIC_ADDPATH

   The fields of these message types are identical to the equivalent
   non-additional-path versions specified in section 4.3 [RFC6396].
   However, for the specific case of the 4 AFI/SAFI specific RIB
   subtypes, the existing RIB Entries field is re-defined as detailed in
   the sections below.

4.1.  AFI/SAFI specific RIB Subtypes

   In order to preserve the record compaction achieved by using the most
   common subtypes, and allowing multiple RIB Entries to be stored in a
   single TABLE_DUMP_V2 record, the existing RIB Entries field is




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   redefined for use within the new AFI/SAFI specific RIB Subtypes
   defined by this document as follows:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         Peer Index            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Originated Time                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Path Identifier                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      Attribute Length         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                    BGP Attributes... (variable)
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

       Figure 1: RIB Entries for AFI/SAFI-specific RIB Subtypes with
                         additional-paths support

   This adds a field to the RIB Entries record, to store the path
   identifier, when used with the RIB_IPV4_UNICAST_ADDPATH,
   RIB_IPV4_MULTICAST_ADDPATH, RIB_IPV6_UNICAST_ADDPATH and
   RIB_IPV6_MULTICAST_ADDPATH subtypes.

4.2.  RIB_GENERIC_ADDPATH Subtype

   The fields of this subtype are identical to the equivalent non-
   additional-path versions specified in section 4.3.3 [RFC6396].  These
   fields continue to encapsulate the raw and additional-path enabled
   AFI/SAFI/NLRI in the record, and the raw attributes in the RIB
   Entries.

   For clarity, the RIB Entries in this subtype are not redefined.

5.  IANA Considerations

   This document requests that IANA assign the following subtype codes
   to the MRT name space [1]:

5.1.  BGP4MP/BGP4MP_ET Subtype codes:

      BGP4MP_MESSAGE_ADDPATH = 8 (Section 3)

      BGP4MP_MESSAGE_AS4_ADDPATH = 9 (Section 3)

      BGP4MP_MESSAGE_LOCAL_ADDPATH = 10 (Section 3)




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      BGP4MP_MESSAGE_AS4_LOCAL_ADDPATH = 11 (Section 3)

   The values provided above are suggested as they are used in
   implementations.

5.2.  TABLE_DUMP_V2 Subtype codes:

      RIB_IPV4_UNICAST_ADDPATH = 8 (Section 4.1)

      RIB_IPV4_MULTICAST_ADDPATH = 9 (Section 4.1)

      RIB_IPV6_UNICAST_ADDPATH = 10 (Section 4.1)

      RIB_IPV6_MULTICAST_ADDPATH = 11 (Section 4.1)

      RIB_GENERIC_ADDPATH = 12 (Section 4.2)

   The values provided above are suggested as they are used in
   implementations.

6.  Security Considerations

   It is not believed that this document adds any additional security
   considerations.

   However, the security considerations of [RFC6396] are equally
   applicable to this document, and this document permits the export of
   more detailed routing data.

   An organization that uses the MRT format to store their BGP routing
   information should be aware that supporting these extensions permits
   more detailed network path information to be stored, and should
   consider the implications of this within their environment.

   An organization that peers with public BGP collectors, and enables
   the additional-paths capability on a peering session, should be aware
   that it is exporting not only its best paths, but potentially other
   paths within its networks.  The BGP peer should consider any and all
   implications of exposing this additional data.

7.  References

7.1.  Normative References

   [RFC6396]  Blunk, L., Karir, M., and C. Labovitz, "Multi-Threaded
              Routing Toolkit (MRT) Routing Information Export Format",
              RFC 6396, DOI 10.17487/RFC6396, October 2011,
              <http://www.rfc-editor.org/info/rfc6396>.



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   [RFC7911]  Walton, D., Retana, A., Chen, E., and J. Scudder,
              "Advertisement of Multiple Paths in BGP", RFC 7911,
              DOI 10.17487/RFC7911, July 2016,
              <http://www.rfc-editor.org/info/rfc7911>.

7.2.  URIs

   [1] https://www.iana.org/assignments/mrt/mrt.xhtml

Authors' Addresses

   Colin Petrie
   RIPE NCC
   Stationsplein 11
   Amsterdam  1012 AB
   NL

   Email: cpetrie@ripe.net


   Thomas King
   DE-CIX Management GmbH
   Lichtstrasse 43i
   Cologne  50825
   Germany

   Email: thomas.king@de-cix.net
























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