BMP Extension for Path Status TLV
draft-cppy-grow-bmp-path-marking-tlv-07

Document Type Active Internet-Draft (individual)
Authors Camilo Cardona  , Paolo Lucente  , Pierre Francois  , Yunan Gu  , Thomas Graf 
Last updated 2020-10-26
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Network Working Group                                         C. Cardona
Internet-Draft                                                P. Lucente
Intended status: Standards Track                                     NTT
Expires: April 29, 2021                                      P. Francois
                                                               INSA-Lyon
                                                                   Y. Gu
                                                                  Huawei
                                                                 T. Graf
                                                                Swisscom
                                                        October 26, 2020

                   BMP Extension for Path Status TLV
                draft-cppy-grow-bmp-path-marking-tlv-07

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 before and 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 April 29, 2021.

Copyright Notice

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   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Path Status TLV . . . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  IANA-registered Path Status TLV . . . . . . . . . . . . .   3
     2.2.  Enterprise-specific Path Status TLV . . . . . . . . . . .   5
   3.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   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 that facilitate 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
   information can complement other centralized sources of data, for
   example, flow collectors.

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   This document defines a so-called Path Status TLV to convey the BGP
   path status to the BMP server.  The BMP Path Status TLV is carried in
   the BMP Route Monitoring (RM) Message.

2.  Path Status TLV

   This document defines two types of Path Status TLVs: one is the IANA-
   registered Path Status TLV, and the other is the Enterprise-specific
   Path Status TLV.

2.1.  IANA-registered Path Status 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)       |
     +---------------------------------------------------------------+
     |        Index (2 octets)       |
     +-------------------------------+-------------------------------+
     |                      Path Status (4 octets)                   |
     +---------------------------------------------------------------+
     |                 Reason Code (2 octets, optional)              |
     +---------------------------------------------------------------+

         Figure 2: Encoding of IANA-Registered Path Status TLV

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

   o  Type = TBD2 (15 Bits): indicates that it is the IANA-registered
      Path Status TLV.

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

   o  Index (2 Octets): indicates the prefix that this TLV is
      describing.  The index is the encapsulation order, starting from
      0, of the prefix in the BGP Update PDU.

   o  Path Status (4 Octets): indicates the path status of the BGP
      Update PDU encapsulated in the RM Message.  Currently 8 types of
      path status are defined, as shown in Table 1.  All zeros are
      reserved.

   o  Reason Code (2 Octets, optional): indicates the reason of the path
      status indicated in the Path Status field.  The reason code field
      is optional.  If no reason code is carried, this field is empty.
      If a reason code is carried, the reason code is indicated by a
      2-byte value, which is defined in Table 2.

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                    +------------+------------------+
                    | Value      | Path type        |
                    +-------------------------------+
                    | 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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    +----------+-----------------------------------------------------+
    |   Value  | Reason code                                         |
    +----------------------------------------------------------------+
    | [0x0001] | invalid for super network                           |
    | [0x0002] | invalid for dampening                               |
    | [0x0003] | invalid for damping history                         |
    | [0x0004] | invalid for policy deny                             |
    | [0x0005] | invalid for ROV not valid                           |
    | [0x0006] | invalid for interface error                         |
    | [0x0007] | invalid for nexthop route unreachable               |
    | [0x0008] | invalid for nexthop tunnel unreachable              |
    | [0x0009] | invalid for nexthop restrain                        |
    | [0x000A] | invalid for not supporting BGP LSP relay            |
    | [0x000B] | invalid for being inactive within VPN insance       |
    | [0x000C] | invalid for prefix sid not exist                    |
    | [0x000D] | not preferred for peer address                      |
    | [0x000E] | not preferred for router ID                         |
    | [0x000F] | not preferred for Cluster List                      |
    | [0x0010] | not preferred for IGP cost                          |
    | [0x0011] | not preferred for peer type                         |
    | [0x0012] | not preferred for MED                               |
    | [0x0013] | not preferred for origin                            |
    | [0x0014] | not preferred for AS Path                           |
    | [0x0015] | not preferred for route type                        |
    | [0x0016] | not preferred for Local preference                  |
    | [0x0017] | not preferred for Weight                            |
    | [0x0018] | not preferred for path to next hop with bit error   |
    | [0x0019] | not preferred for path id                           |
    | [0x001A] | not preferred for ROV validation                    |
    | [0x001B] | not preferred for originate IP                      |
    | [0x001C] | not preferred for route distinguisher               |
    | [0x001D] | not preferred for delayed route selection           |
    | [0x001E] | not preferred for imported from other instances     |
    | [0x001F] | not preferred for med plus igp cost                 |
    | [0x0020] | not preferred for AIGP                              |
    | [0x0021] | not preferred for BGP LSP aigp for next hop relay   |
    | [0x0022] | not preferred for nexthop IP                        |
    +----------+-----------------------------------------------------+

                   Table 2: IANA-Registered Reason Code

2.2.  Enterprise-specific Path Status TLV

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    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)                    |
   +---------------------------------------------------------------+
   |        Index (2 octets)       |
   +---------------------------------------------------------------+
   |                      Path Status (4 octets)                   |
   +---------------------------------------------------------------+
   |               Reason Code (2 octets, optional)                |
   +---------------------------------------------------------------+

      Figure 3: Encoding of Enterprise-specific Path Status TLV

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

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

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

   o  Index (2 Octets): indicates the prefix that this TLV is
      describing.  The index is the encapsulation order, starting from
      0, of the prefix in the BGP Update PDU.

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

   o  Path Status (4 Octets): indicates the enterprise-specific path
      status.  The format is to be determined w.r.t. each PEN number.

   o  Reason Code (2 octets, optional): indicates the reasons/
      explanations of the path status indicated in the Path Status
      field.  The format is to be determined w.r.t. each PEN number.

3.  Acknowledgments

   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.

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   Type = TBD1 (15 Bits): indicates that it is the IANA-registered Path
   Status TLV.

5.  Security Considerations

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

6.  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-03 (work in progress), September 2020.

   [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-12
              (work in progress), August 2020.

   [I-D.lapukhov-bgp-ecmp-considerations]
              Lapukhov, P. and J. Tantsura, "Equal-Cost Multipath
              Considerations for BGP", draft-lapukhov-bgp-ecmp-
              considerations-04 (work in progress), May 2020.

   [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-01 (work in progress), May 2020.

   [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>.

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   [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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