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Network Working Group                                         C. Cardona
Internet-Draft                                                P. Lucente
Intended status: Standards Track                                     NTT
Expires: September 9, 2020                                   P. Francois
                                                               INSA-Lyon
                                                                   Y. Gu
                                                                  Huawei
                                                                 T. Graf
                                                                Swisscom
                                                          March 08, 2020


                   BMP Extension for Path Marking TLV
                draft-cppy-grow-bmp-path-marking-tlv-03

Abstract

   The BGP Monitoring Protocol (BMP) provides an interface for obtaining
   BGP Path information.  BGP Path Information is conveyed within BMP
   Route Monitoring (RM) messages.  This document proposes an extension
   to BMP to convey the status of a BGP path after being processed by
   the BGP best-path selection algorithm.  This extension makes use of
   the TLV mechanims described in draft-ietf-grow-bmp-tlv
   [I-D.ietf-grow-bmp-tlv] and draft-lucente-grow-bmp-tlv-ebit
   [I-D.lucente-grow-bmp-tlv-ebit].

Requirements Language

   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 BCP
   14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
   appear in all capitals, as shown here.

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."



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   This Internet-Draft will expire on September 9, 2020.

Copyright Notice

   Copyright (c) 2020 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 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.  Prefix Information TLV for the RM Message . . . . . . . . . .   3
   3.  Path Marking sub-TLV  . . . . . . . . . . . . . . . . . . . .   3
     3.1.  IANA-registered Path Markinig sub-TLV . . . . . . . . . .   4
     3.2.  Enterprise-specific Path Marking sub-TLV  . . . . . . . .   6
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   For a given prefix, multiple paths with different path status, e.g.,
   the "best-path", "back-up path" and so on, may co-exist in the BGP
   RIB after being processed by the local policy and the BGP decision
   process.  The path status information is currently not carried in the
   BGP Update Message RFC4271 [RFC4271] or in the BMP Update Message
   RFC7854 [RFC7854].

   External systems can use the path status for various applications.
   The path status is commonly checked by operators when performing
   troubleshooting.  Having such status stored in a centralized system
   can enable the development of tools facilitating this process.
   Optimisation systems can include the path status in their process,
   and also use the status as a validation source (since it can compare
   the calculated state to the actual outcome of the network, such as
   primary and backup path).  As a final example, path status




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   information can complement other centralized sources of data, for
   example, flow collectors.

   This document defines a so-called Path Marking TLV to convey the BGP
   path status information to the BMP server.  The BMP Path Marking is
   defined to be prepended in the BMP Route Monitoring (RM) Message.

2.  Prefix Information TLV for the RM Message

   As per RFC7854 [RFC7854], the BMP RM Message consists of the Common
   Header, Per-Peer Header, and the BGP Update PDU.  According to draft-
   grow-bmp-tlv [I-D.ietf-grow-bmp-tlv] , optional trailing data in TLV
   format is allowed in the BMP RM Message to convey characteristics of
   transported NLRIs (i.e. to help stateless parsing) or vendor-specific
   data.  Such TLV types are to be defined for each application.

   This document defines the Prefix Information TLV to convey
   descriptional information for route prefixes.  The format is shown
   below.

    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 (2 octets)        |       Length (2 octets)       |
   +---------------------------------------------------------------+
   |        Count (2 octets)       |
   +-------------------------------+-------------------------------+
   |                 Prefix information value(variable)            |
   +---------------------------------------------------------------+

                   Figure 1: Prefix Information TLV

   o  Type = TBD1 (2 Octets): Prefix Information TLV.

   o  Length (2 Octets): indicates the length of the value field of the
      Prefix Information TLV.

   o  Count (2 Octets): indicates the number of sub TLVs followed in the
      Prefix Information Value field.

   o  Prefix information value (Variable): indicates the value of the
      Prefix Informtion TLV, which consists of one or multiple sub TLVs.

3.  Path Marking sub-TLV

   As stated in Appendix F.1 of RFC4271 [RFC4271], multiple address
   prefixes with the same path attributes are allowed to be specified in
   one message.  However, such multiple prefixes may have different
   prefix information, e.g., path status.  Thus, to indicate the path



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   status for each BGP prefix, we define the Path Marking sub-TLV.  The
   order of the Path Marking sub-TLVs MUST be in accordance with the
   prefix order of the Update PDU.

   The E-bit [I-D.lucente-grow-bmp-tlv-ebit] mechanism allows the usage
   of vendor-specific TLVs in addition to IANA-registered one.  In this
   document, both encoding options for the Path Marking sub-TLV are
   described.

3.1.  IANA-registered Path Markinig sub-TLV

      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
     +-------------------------------+-------------------------------+
     |E|       Type (15 bits)        |       Length (2 octets)       |
     +-------------------------------+-------------------------------+
     |                      Path Status(4 octets)                    |
     +---------------------------------------------------------------+
     |                      Reason Code(4 octets)                    |
     +---------------------------------------------------------------+

         Figure 2:IANA-Registered Encoding of Path Marking sub-TLV

   o  E bit: For an IANA-registered sub-TLV, the E bit MUST be set to 0.

   o  Type = TBD2 (15 Bits): Path Marking sub-TLV.

   o  Length (2 Octets): indicates the length of the value field of the
      Path Marking TLV.  The value field further consists of the Path-
      Status field and Reason Code field.

   o  Path Status (4 Octets): indicates the path status of the BGP
      Update PDU encapsulated in the RM Message.  Currently 9 types of
      path status are defined, as shown in Table 1.

   o  Reason Code (4 Octets): indicates the reasons/explanations of the
      path status indicated in the Path Type field.  The detailed Reason
      Code bitmap remains to be defined.














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                    +------------+------------------+
                    | Value      | Path type        |
                    +-------------------------------+
                    | 0x00000000 | Unknown          |
                    | 0x00000001 | Invalid          |
                    | 0x00000002 | Best             |
                    | 0x00000004 | Non-selected     |
                    | 0x00000008 | Primary          |
                    | 0x00000010 | Backup           |
                    | 0x00000020 | Non+installed    |
                    | 0x00000040 | Best external    |
                    | 0x00000080 | Add-Path         |
                    +------------+------------------+

                    Table 1: IANA-Registered Path Type

   The Path Status field contains a bitmap where each bit encodes a
   specific role of the path.  Multiple bits may be set when multiple
   path status apply to a path.

   o  The best-path is defined in RFC4271 [RFC4271] and the best-
      external path is defined in draft-ietf-idr-best-external
      [I-D.ietf-idr-best-external].

   o  An invalid path is a route that does not enter the BGP decision
      process.

   o  A non-selected path is a route that is not selected in the BGP
      decision process.  Back-up routes are considered non-selected,
      while the best and ECMP routes are not considered as non-selected.

   o  A primary path is a recursive or non-recursive path whose nexthop
      resolution ends with an adjacency draft-ietf-rtgwg-bgp-pic
      [I-D.ietf-rtgwg-bgp-pic].  A prefix can have more than one primary
      path if multipath is configured draft-lapukhov-bgp-ecmp-
      considerations [I-D.lapukhov-bgp-ecmp-considerations].  A best-
      path is also considered as a primary path.

   o  A backup path is also installed in the RIB, but it is not used
      until some or all primary paths become unreachable.  Backup paths
      are used for fast convergence in the event of failures.

   o  A non-installed path refers to the route that is not installed
      into the IP routing table.

   o  For the advertisement of multiple paths for the same address
      prefix without the new paths implicitly replacing any previous
      ones, the add-path status is applied RFC7911 [RFC7911].



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3.2.  Enterprise-specific Path Marking sub-TLV

    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
   +-------------------------------+-------------------------------+
   |E|       Type (15 bits)        |       Length (2 octets)       |
   +-------------------------------+-------------------------------+
   |                      PEN number (4 octets)                    |
   +---------------------------------------------------------------+
   |                      Path Status(4 octets)                    |
   +---------------------------------------------------------------+
   |                      Reason Code(variable)                    |
   +---------------------------------------------------------------+

    Figure 3: Enterprise-specific encoding of Path Markiing sub-TLV

   o  E bit: For an Enterprise-specific sub-TLV, the E bit MUST be set
      to 1.

   o  Type = 1 (15 Bits): indicates that it's the Enterprise-specific
      Path Marking sub-TLV.

   o  Length (2 Octets): indicates the length of the value field of the
      Path Marking TLV.  The value field further consists of the Path-
      Status field and Reason Code field.

   o  PEN Number (4 octets): indicates the IANA enterprise number IANA-
      PEN.

   o  Path Status (4 Octets): indicates enterprise-specific path status,
      which remains to be defined.

   o  Reason Code (Variable): indicates the reasons/explanations of the
      path status indicated in the Path Type field.  The detailed Reason
      Code string is to be defined.

4.  Acknowledgements

   We would like to thank Jeff Haas for his valuable comments.

5.  IANA Considerations

   This document requests that IANA assign the following new parameters
   to the BMP parameters name space.

   Type = TBD1 (2 Octets): Prefix Information TLV.

   Type = TBD2 (15 Bits): Path Marking sub-TLV.




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6.  Security Considerations

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

7.  Normative References

   [I-D.ietf-grow-bmp-tlv]
              Lucente, P., Gu, Y., and H. Smit, "TLV support for BMP
              Route Monitoring and Peer Down Messages", draft-ietf-grow-
              bmp-tlv-01 (work in progress), October 2019.

   [I-D.ietf-idr-best-external]
              Marques, P., Fernando, R., Chen, E., Mohapatra, P., and H.
              Gredler, "Advertisement of the best external route in
              BGP", draft-ietf-idr-best-external-05 (work in progress),
              January 2012.

   [I-D.ietf-rtgwg-bgp-pic]
              Bashandy, A., Filsfils, C., and P. Mohapatra, "BGP Prefix
              Independent Convergence", draft-ietf-rtgwg-bgp-pic-11
              (work in progress), February 2020.

   [I-D.lapukhov-bgp-ecmp-considerations]
              Lapukhov, P. and J. Tantsura, "Equal-Cost Multipath
              Considerations for BGP", draft-lapukhov-bgp-ecmp-
              considerations-03 (work in progress), November 2019.

   [I-D.lucente-grow-bmp-tlv-ebit]
              Lucente, P. and Y. Gu, "Support for Enterprise-specific
              TLVs in the BGP Monitoring Protocol", draft-lucente-grow-
              bmp-tlv-ebit-00 (work in progress), November 2019.

   [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>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC7854]  Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
              Monitoring Protocol (BMP)", RFC 7854,
              DOI 10.17487/RFC7854, June 2016,
              <https://www.rfc-editor.org/info/rfc7854>.




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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,
              <https://www.rfc-editor.org/info/rfc7911>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

Authors' Addresses

   Camilo Cardona
   NTT
   164-168, Carrer de Numancia
   Barcelona  08029
   Spain

   Email: camilo@ntt.net


   Paolo Lucente
   NTT
   Siriusdreef 70-72
   Hoofddorp, WT  2132
   Netherlands

   Email: paolo@ntt.net


   Pierre Francois
   INSA-Lyon
   Lyon
   France

   Email: Pierre.Francois@insa-lyon.fr


   Yunan Gu
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: guyunan@huawei.com







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   Thomas Graf
   Swisscom
   Binzring 17
   Zurich  8045
   Switzerland

   Email: thomas.graf@swisscom.com












































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