TLV support for BMP Route Monitoring and Peer Down Messages
draft-ietf-grow-bmp-tlv-09

Global Routing Operations                                     P. Lucente
Internet-Draft                                                       NTT
Updates: 7854 (if approved)                                        Y. Gu
Intended status: Standards Track                                  Huawei
Expires: 15 April 2023                                   12 October 2022

      TLV support for BMP Route Monitoring and Peer Down Messages
                       draft-ietf-grow-bmp-tlv-09

Abstract

   Most of the message types defined by the BGP Monitoring Protocol
   (BMP) make provision for optional trailing data.  However, Route
   Monitoring messages (which provide a snapshot of the monitored
   Routing Information Base) and Peer Down messages (which indicate that
   a peering session was terminated) do not.  Supporting optional data
   in TLV format across all BMP message types allows for a homogeneous
   and extensible surface that would be useful for the most different
   use-cases that need to convey additional data to a BMP station.
   While it is not intended for this document to cover any specific
   utilization scenario, it defines a simple way to support optional TLV
   data in all message types.

Status of This Memo

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Copyright Notice

   Copyright (c) 2022 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  TLV encoding  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  BMP Message Format  . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Common Header . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  TLV data in Route Monitoring  . . . . . . . . . . . . . .   4
     4.3.  TLV data in Peer Down . . . . . . . . . . . . . . . . . .   5
     4.4.  TLV data in other BMP messages  . . . . . . . . . . . . .   5
   5.  Error handling  . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  Operational Considerations  . . . . . . . . . . . . . . . . .   6
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   The BGP Monitoring Protocol (BMP) is defined in RFC 7854 [RFC7854].

   The Route Monitoring message consists of:

   *  Common Header

   *  Per-Peer Header

   *  BGP Update PDU

   The Peer Down Notification message consists of:

   *  Common Header

   *  Per-Peer Header

   *  Reason

   *  Data (only if Reason code is 1, 2 or 3)

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   This means that both Route Monitoring and Peer Down messages have a
   non-extensible format.  In the Route Monitoring case, this prevents
   the transmission of characteristics of transported NLRIs (e.g. to
   help with stateless parsing) or of vendor-specific data.  In the Peer
   Down case, this prevents matching with TLVs previously sent with the
   Peer Up message.  The proposal of this document is to bump the BMP
   version, for backward compatibility, and allow all message types to
   make provision for trailing TLV data.

2.  Terminology

   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.

3.  TLV encoding

   The TLV data type is already defined in Section 4.4 of [RFC7854] for
   the Initiation and Peer Up message types.  A TLV consists of:

   *  2 octets of TLV Type,

   *  2 octets of TLV Length,

   *  0 or more octets of TLV Value.

      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)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                      Value (variable)                         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 1

   TLVs SHOULD be sorted by their code point.  Multiple TLVs of the same
   type can be repeated as part of the same message, and it is left to
   the specific use-cases whether all, any, the first or the last TLV
   should be considered as well as whether ordering matters.

   Route Monitoring messages may require per-NLRI TLVs, that is, there
   may be a need to map TLVs to NLRIs contained in the BGP Update
   message, for example, to express additional characteristics of a
   specific NLRI.  For this purpose specifically, TLVs in Route

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   Monitoring messages MUST be indexed, with the index starting at one
   (1) to refer to the first NLRI.  Index zero (0) specifies that a TLV
   does apply to all NLRIs contained in the BGP Update message.
   Multiple TLVs of the same type and with the same index can be
   repeated as part of the same message.  Indexed TLVs are encoded as in
   the following figure:

      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)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Index (2 octets)       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                      Value (variable)                         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 2

   Of the BMP message types defined so far, indexed TLVs apply only to
   Route Monitoring messages and, for example, they do not apply to
   Route Mirroring messages because the sender may not be aware of the
   payload of the transported BGP Update message.

4.  BMP Message Format

4.1.  Common Header

   Section 4.1 of [RFC7854] defines the Common Header.  While the
   structure remains unaltered, the following two definitions are
   changed:

   *  Version: Indicates the BMP version.  This is set to '4' for all
      messages.

   *  Message Length: Total length of the message in bytes (including
      headers, encapsulated BGP message and optional data)

4.2.  TLV data in Route Monitoring

   The Route Monitoring message type is defined in Section 4.6 of
   [RFC7854].  The BGP Update PDU Section 4.3 of [RFC4271] MAY be
   followed by TLV data.  This document defines the following new code
   points to help stateless parsing of BGP Update PDUs:

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   *  Type = TBD1: the BGP Update PDU is encoded with support for the
      4-octet AS number capability RFC 6793 [RFC6793], length MUST be 1
      and value MUST be 0 for false and 1 for true.

   *  Type = TBD2: the BGP Update PDU is encoded with the ADD-PATH
      capability RFC 7911 [RFC7911], length MUST be 1 and value MUST be
      0 for false and 1 for true.

   *  Type = TBD3: the BGP Update PDU is encoded with the Multiple
      Labels capability RFC 8277 [RFC8277], length MUST be 1 and value
      MUST be 0 for false and 1 for true.

4.3.  TLV data in Peer Down

   The Peer Down Notification message type is defined in Section 4.9 of
   [RFC7854].  For Reason codes 1 or 3, a BGP Notification PDU follows;
   the PDU MAY be followed by TLV data.  For Reason code 2, a 2-byte
   field to give additional FSM info follows; this field MAY be followed
   by TLV data.  For all other Reason codes, TLV data MAY follow the
   Reason field.

4.4.  TLV data in other BMP messages

   All other message types defined in RFC7854 [RFC7854] already provide
   for TLV data.  It is RECOMMENDED that all future BMP message types
   also provide for trailing TLV data.

5.  Error handling

   When a BGP PDU is enclosed in BMP messages (always for Route
   Monitoring messages, in some cases for Peer Down messages),
   processing of optional trailing data is subject to proper decoding of
   a well-formed BGP message.

   Additionally, it is worth nothing that RFC8654 [RFC8654] permits BGP
   Updates and other messages to grow to a length of 65535 octets.  This
   may cause a BMP PDU that attempts to encapsulate such long messages
   to overflow.

6.  Security Considerations

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

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7.  Operational Considerations

   In Route Monitoring messages, the number of TLVs can be bound to the
   amount of NLRIs carried in the BGP Update message.  This may degrade
   the packing of information in such messages and have specific impacts
   on the memory and CPU used in a BMP implementation.  As a result of
   that it should always be possible to disable such features to
   mitigate their impact.

8.  IANA Considerations

   This document requests the definition of two new registries "BMP
   Route Monitoring Information TLVs" and "BMP Peer Down Information
   TLVs".  As part of the "BMP Route Monitoring Information TLVs"
   registry, the following new TLV types are defined (Section 4.2):

   *  Type = TBD1: Support for the 4-octet AS number capability.  The
      value field is set to 1 if the BGP Update PDU enclosed in the
      Route Monitoring message was encoded according to the capability.

   *  Type = TBD2: ADD-PATH capability.  The value field is set to 1 if
      the BGP Update PDU enclosed in the Route Monitoring message was
      encoded according to the capability.

   *  Type = TBD3: Multiple Labels capability.  The value field is set
      to 1 if the BGP Update PDU enclosed in the Route Monitoring
      message was encoded according to the capability.

9.  Normative References

   [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>.

   [RFC6793]  Vohra, Q. and E. Chen, "BGP Support for Four-Octet
              Autonomous System (AS) Number Space", RFC 6793,
              DOI 10.17487/RFC6793, December 2012,
              <https://www.rfc-editor.org/info/rfc6793>.

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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>.

   [RFC8277]  Rosen, E., "Using BGP to Bind MPLS Labels to Address
              Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
              <https://www.rfc-editor.org/info/rfc8277>.

   [RFC8654]  Bush, R., Patel, K., and D. Ward, "Extended Message
              Support for BGP", RFC 8654, DOI 10.17487/RFC8654, October
              2019, <https://www.rfc-editor.org/info/rfc8654>.

Acknowledgements

   The authors would like to thank Jeff Haas, Camilo Cardona, Thomas
   Graf, Pierre Francois and Ben Maddison for their valuable input.  The
   authors would also like to thank Greg Skinner and Zongpeng Du for
   their review.

Authors' Addresses

   Paolo Lucente
   NTT
   Veemweg 23
   3771 Barneveld
   Netherlands
   Email: paolo@ntt.net

   Yunan Gu
   Huawei
   Huawei Bld., No.156 Beiqing Rd.
   Beijing
   100095
   China
   Email: guyunan@huawei.com

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