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BMP v4: TLV support for BMP Route Monitoring and Peer Down Messages
draft-ietf-grow-bmp-tlv-13

Document Type Active Internet-Draft (grow WG)
Authors Paolo Lucente , Yunan Gu
Last updated 2023-10-23
Replaces draft-lucente-bmp-tlv
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draft-ietf-grow-bmp-tlv-13
Global Routing Operations                                     P. Lucente
Internet-Draft                                                       NTT
Updates: 7854 (if approved)                                        Y. Gu
Intended status: Standards Track                                  Huawei
Expires: 25 April 2024                                   23 October 2023

  BMP v4: TLV support for BMP Route Monitoring and Peer Down Messages
                       draft-ietf-grow-bmp-tlv-13

Abstract

   Most of the message types defined by the BGP Monitoring Protocol
   (BMP) make provision for data in TLV format.  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 TLV data in
   all message types.

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."

   This Internet-Draft will expire on 25 April 2024.

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   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 Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  TLV encoding  . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  BMP Message Format  . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Common Header . . . . . . . . . . . . . . . . . . . . . .   5
     4.2.  TLV data in Route Monitoring  . . . . . . . . . . . . . .   5
       4.2.1.  Group TLV . . . . . . . . . . . . . . . . . . . . . .   5
         4.2.1.1.  Wire-format example . . . . . . . . . . . . . . .   6
       4.2.2.  VRF/Table Name TLV  . . . . . . . . . . . . . . . . .   7
       4.2.3.  Stateless parsing TLVs  . . . . . . . . . . . . . . .   7
     4.3.  TLV data in Peer Down . . . . . . . . . . . . . . . . . .   8
     4.4.  TLV data in other BMP messages  . . . . . . . . . . . . .   8
   5.  Error handling  . . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   7.  Operational Considerations  . . . . . . . . . . . . . . . . .   9
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

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

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   *  Reason

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

   *  TLV (only if Reason code is 6)

   This means that both Route Monitoring and Peer Down messages have a
   non-extensible format (except for the specific case of Peer Down
   Reason Code 6 as defined by RFC 9069 [RFC9069]).  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

   *  Allow all defined BMP message types to make provision for TLV data

   *  Change the structure of Route Monitoring so that the BGPU PDU is
      enclosed in a TLV

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.

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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Type (2 octets)        |     Length (2 octets)         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                      Value (variable)                         ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 1

   TLVs SHOULD be sorted by the sender 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
   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

   In indexed TLVs, the reported length refers to the total encoded TLV
   value (ie. it does exclude the length of the index field).

   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.

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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 consistency model selected to extend this message
   type with TLVs is with the Route Mirroring type where the Per-peer
   header is being followed by TLVs.

   The BGP Update PDU Section 4.3 of [RFC4271] is encoded itself as part
   of a BGP Message TLV with code point TBD1 and index set to zero.  A
   Route Monitoring message MUST contain one BGP Message TLV which may
   be preceeded and/or followed by other optional TLV data.

   Corollary, in BMPv4 the BGP Update PDU is not just encoded as part of
   the message as it was the case for BMPv3 but it is rather enclosed in
   a TLV.

4.2.1.  Group TLV

   In a Route Monitoring message where the BGP Update PDU carries N
   NLRIs, indexed TLVs do allow to handle the cases of 1:1 and N:1
   relationship among NLRIs and TLVs.  The case of N:M relationship does
   instead require a form of grouping and hence this document defines a
   Group TLV to achieve this.

   The TLV MUST have an index set to zero.  The value MUST contain:

   *  A 2 bytes Group Index whose value MUST be greater than the amount
      of NLRIs packed in the BGP Update PDU and MUST be unique to the
      message

   *  One or more 2 bytes indexes whose values MUST be less or equal to
      the amount of NLRIs packed in the BGP Update PDU.

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   A NLRI index can be listed as part of multiple Group TLVs within the
   same message.  NLRI indexes within a Group TLV SHOULD be sorted by
   the sender.  A Group Index can not reference an NLRI index 0.
   Finally, a Group TLV MUST NOT include its own or another Group Index.
   Multiple TLVs can point to the same Group Index, i.e. a group can be
   reused within the same Route Monitoring message.

   The Group TLV code point is TBD2

4.2.1.1.  Wire-format example

   The diagram in Figure 3 shows an example of a Route Monitoring
   message carrying a BGP UPDATE containing 10 NLRIs.  The TLVs are
   comprised of:

   1.  a Group TLV with index 0x000b, pointing to NLRI 1, 2, 3 and 10

   2.  a Group TLV with index 0x000c, pointing to NLRI 4, 5 and 6

   3.  a TLV pertaining to NLRI 7

   4.  a TLV pertaining to the NLRIs listed in the Group TLV defined in
       1

   5.  a TLV pertaining to the NLRIs listed in the Group TLV defined in
       2

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        Common Header + Per-Peer Header (6 + 48 bytes)         ~
      ~                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            type=TBD1            |         length=X            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             index=0             |    value=$BGP_UPDATE_PDU{   ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                             ~
      ~                                                               ~
      ~                       NLRI_1 .. NLRI_10                       ~
      ~                                                            }  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            type=TBD2            |         length=0x000c       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             index=0             |      group_index=0x000b     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  value={0x0001,   0x0002,                     |
      |                         0x0003,   0x000a}                     |

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      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            type=TBD2            |         length=0x000a       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             index=0             |      group_index=0x000c     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  value={0x0004,   0x0005,                     |
      |                         0x0006} |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            type=SomeTlvX        |         length=0x0006       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             index=0x0007        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          value={4 bytes}                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            type=SomeTlvY        |         length=0x000a       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             index=0x000b        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          value={8 bytes}                      ~
      ~                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |            type=SomeTlvZ        |         length=0x0006       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |             index=0x000c        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          value={4 bytes}                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                  Figure 3

4.2.2.  VRF/Table Name TLV

   The Information field contains a UTF-8 string whose value MUST be
   equal to the value of the VRF or table name (ie.  RD instance name)
   being conveyed.  The string size MUST be within the range of 1 to 255
   bytes.

   The VRF/Table Name TLV code point is TBD3

4.2.3.  Stateless parsing TLVs

   Stateless parsing helps scaling the amount of Route Monitoring
   messages that can be processed at collection time, avoiding to have
   to correlate them to BGP capabilities received as part of the Peer Up
   message, for example.

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   Some BGP capabilities are not per AFI/SAFI, like 4-bytes ASN RFC 6793
   [RFC6793], and hence these can be part of the BMP Peer flags section
   of a Route Monitoring message.  Those that are, instead, per AFI/SAFI
   require finer granularity and hence the use of an indexed TLV.

   This document also defines the following new code points to help
   stateless parsing of BGP Update PDUs:

   *  Type = TBD4: 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 = TBD5: 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.

   It is recommended that any Stateless Parsing TLVs are encoded
   preceeding the BGP Message TLV in order to ease parsing of the Route
   Monitoring message at the BMP station side.

4.3.  TLV data in Peer Down

   The Peer Down Notification message type is defined in Section 4.9 of
   [RFC7854].  The consistency model selected to extend this message
   type with TLVs is with the Peer Up type where optional TLVs are
   placed at the end of the message.

   This means 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] do already
   provision for TLV data.  It is RECOMMENDED that all future BMP
   message types will also provide for TLV data following a consistency
   model with existing message types.

5.  Error handling

   It is worth nothing that RFC8654 [RFC8654] permits BGP Update 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.

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6.  Security Considerations

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

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 renaming of the "Peer Up TLVs" registry
   defined by BMP Peer Up Message Namespace [I-D.ietf-grow-bmp-peer-up]
   into "Peer Up and Peer Down TLVs" and the definition of one new
   registry "BMP Route Monitoring TLVs".  As part of the "BMP Route
   Monitoring TLVs" registry, the following new TLV types are defined
   (Section 4.2):

   *  Type = TBD1: Support for BGP Message TLV.  The value field is
      defined in Section 4.2

   *  Type = TBD2: Support for grouping of TLVs.  The value field is
      defined in Section 4.2.1

   *  Type = TBD3: Support for VRF/Table Name TLV.  The value field is
      defined in Section 4.2.2

   *  Type = TBD4: 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 = TBD5: 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

   [I-D.ietf-grow-bmp-peer-up]
              Scudder, J. and P. Lucente, "BMP Peer Up Message
              Namespace", Work in Progress, Internet-Draft, draft-ietf-
              grow-bmp-peer-up-01, 13 July 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-grow-
              bmp-peer-up-01>.

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   [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>.

   [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>.

   [RFC9069]  Evens, T., Bayraktar, S., Bhardwaj, M., and P. Lucente,
              "Support for Local RIB in the BGP Monitoring Protocol
              (BMP)", RFC 9069, DOI 10.17487/RFC9069, February 2022,
              <https://www.rfc-editor.org/info/rfc9069>.

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Acknowledgements

   The authors would like to thank Jeff Haas, Camilo Cardona, Thomas
   Graf, Pierre Francois, Ben Maddison, Tim Evens, Luuk Hendriks,
   Maxence Younsi and Ahmed Elhassany 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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