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Versions: 00 01 02

Network Working Group                                         C. Cardona
Internet-Draft                                                P. Lucente
Intended status: Standards Track                                     NTT
Expires: July 6, 2020                                        P. Francois
                                                               INSA-Lyon
                                                                   Y. Gu
                                                                  Huawei
                                                                 T. Graf
                                                                Swisscom
                                                        January 03, 2020


                   BMP Extension for Path Marking TLV
                draft-cppy-grow-bmp-path-marking-tlv-02

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-lucente-bmp-tlv
   [I-D.lucente-bmp-tlv].

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 July 6, 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
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   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.  Path Marking TLV for the RM Message . . . . . . . . . . . . .   3
     2.1.  Path Status . . . . . . . . . . . . . . . . . . . . . . .   4
       2.1.1.  IANA-registered Path Status Encoding  . . . . . . . .   4
       2.1.2.  Enterprise-specific Path Status Encoding  . . . . . .   5
     2.2.  Reason Code . . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.1.  IANA-registered Reason Code Encoding  . . . . . . . .   6
       2.2.2.  Enterprise-specific Reason Code Encoding  . . . . . .   6
   3.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     4.1.  Path Marking TLV  . . . . . . . . . . . . . . . . . . . .   7
     4.2.  Path Marking TLV Reason Code  . . . . . . . . . . . . . .   7
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   6.  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.



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   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
   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.  Path Marking TLV for the RM Message

   As per RFC4271 [RFC4271], the BMP RM Message consists of the Common
   Header, Per-Peer Header, and the BGP Update PDU.  According to draft-
   lucente-bmp-tlv [I-D.lucente-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.

   To include the path status along with each BGP path, we define the
   Path Marking TLV, shown as follows.

      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)       |
     +-------------------------------+-------------------------------+
     |E|                    Path Status(variable)                    |
     +---------------------------------------------------------------+
     |E|                    Reason Code(variable)                    |
     +---------------------------------------------------------------+

                          Figure 1: Path Marking TLV

   o  Type = TBD1 (2 Octets): indicates that it's the Path Marking 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  E bit (1 Bit) for Path Status: indicates if any enterprise-
      specific path status is used after the IANA-registered path status
      code.

   o  Path Status (4 Octets): indicates the path status of the BGP
      Update PDU encapsulated in the RM Message.  Currently 7 types of
      path status are defined, as shown in Table 1.




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   o  E bit (1 Bit) for Reason Code: indicates if any enterprise-
      specific reason code is used after the IANA-registered reason
      code.

   o  Reason Code (Variable): indicates the reasons/explanations of the
      path status indicated in the Path Type field.  The detailed Reason
      Code field is defined in Section 2.2.

2.1.  Path Status

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

   Two encoding options for Path Status are described in the following
   two sections.

2.1.1.  IANA-registered Path Status Encoding

        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
       +-------------------------------+
       |E| IANA registered path status |
       +-------------------------------+

                 Figure 2:  IANA-registered encoding of Path Status

   o  E bit (1 Bit): set to 0, indicating that only IANA-registered path
      status is used in this TLV.

   o  IANA-registered Path Status (2 octets): indicates the IANA-
      registered path status, as specified in Table 1.

                     +--------+----------------------+
                     | Value  | Path type            |
                     +-------------------------------+
                     | 0x0000 | Unknown              |
                     | 0x0001 | Invalid              |
                     | 0x0002 | Best                 |
                     | 0x0004 | Non-selected         |
                     | 0x0008 | Primary              |
                     | 0x0010 | Backup               |
                     | 0x0020 | Non-installed        |
                     | 0x0040 | Best external        |
                     | 0x0080 | Add-Path             |
                     +--------+----------------------+

                          Table 1: Path Type




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   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].

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

   A non-selected path is a route that is not selected in the BGP
   decision process.  In other words, Best route and ECMP routes are not
   considered as non-selected.

   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.

   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.

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

   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].

2.1.2.  Enterprise-specific Path Status Encoding

    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|            Enterprise-Specific Path Type (4 octets)         |
   +---------------------------------------------------------------+
   |                    Enterprise Number(4 octets)                |
   +---------------------------------------------------------------+

       Figure 3: Enterprise-specific encoding of Path Status

   o  E bit (1 Bit): set to 1, indicating enterprise-specific path
      status is used in this TLV.

   o  Enterprise-specific Path Type (4 octets): indicates enterprise-
      specific path status, which remains to be defined.

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



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2.2.  Reason Code

   The Reason Code field contains a bit field where each bit encodes a
   specific reason.  Multiple bits may be set when multiple reasons
   apply to a path.

2.2.1.  IANA-registered Reason Code Encoding

      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|           IANA-registered Reason Code(4 octets)             |
     +---------------------------------------------------------------+

               Figure 4:  IANA-registered encoding of Reason Code

   o  E bit (1 Bit): set to 0, indicating that only IANA-registered
      reason code is used in this TLV.  With the E bit set to 0, the
      Length field of the Path Marking TLV SHOULD be set to 8.

   o  IANA-registered Reason Code (4 octets): indicates the IANA-
      registered reason code of the path status.

2.2.2.  Enterprise-specific Reason Code Encoding

    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|                  Enterprise Number(4 octets)                |
   +---------------------------------------------------------------+
   +                  E-specific Reason Code(variable)             +
   ~                                                               ~
   +---------------------------------------------------------------+

       Figure 5: Enterprise-specific encoding of Reason Code

   o  E bit (1 Bit): set to 1, indicating enterprise-specific reason
      code is also used in this TLV.

   o  IANA-registered Reason Code (4 octets): indicates the IANA-
      registered reason code of the path status.

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

   o  E-specific Reason Code (Variable): indicates enterprise-specific
      reason code of the path status.






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3.  Acknowledgements

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

4.  IANA Considerations

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

4.1.  Path Marking TLV

   This document defines the Path Marking TLV with Type = TBD1: Path
   Marking (Section 2).

4.2.  Path Marking TLV Reason Code

5.  Security Considerations

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

6.  Normative References

   [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-10
              (work in progress), October 2019.

   [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-bmp-tlv]
              Lucente, P., Gu, Y., and H. Smit, "TLV support for BMP
              Route Monitoring and Peer Down Messages", draft-lucente-
              bmp-tlv-00 (work in progress), July 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>.



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   [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>.

   [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






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

   Email: guyunan@huawei.com


   Thomas Graf
   Swisscom
   Binzring 17
   Zurich  8045
   Switzerland

   Email: thomas.graf@swisscom.com



































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