BMP Route Change Statistics Based on Routing Policy
draft-smc-grow-bmp-route-change-stats-02

Network Working Group                                       S. Dikshit
Internet-Draft                                       Aruba Networks, HPE
Intended status: Standards Track                          M. Srivastava
Expires: 25 January 2027                          Hewlett Packard Enterprise
                                                                  C. Lin
                                                    New H3C Technologies
                                                            25 July 2026

            BMP Route Change Statistics Based on Routing Policy
              draft-smc-grow-bmp-route-change-stats-02

Abstract

   This document defines few generic BGP Monitoring Protocol (BMP)
   statistics for monitoring route modifications or changes due to
   applying Routing Policy.  These statistics are reported per BGP
   peer using the BMP Statistics Report message.

   This revision (-02) firms up the specification for working group
   consideration: it adds a Relationship to Other Work section that
   explicitly maps this document to concurrently circulating GROW
   contributions on BMP statistics and policy-driven telemetry and
   invites coordination with their authors, adds a worked example, and
   strengthens Security Considerations. No statistics semantics, Stat
   Type allocations, or wire formats defined in -01 are changed.

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 January 2027.

Copyright Notice

   Copyright (c) 2026 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 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.

Dikshit, et al.         Expires 25 January 2027                [Page 1]
Internet-Draft         BMP Route Change Stats                July 2026

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Motivation and Use Cases  . . . . . . . . . . . . . . . . . .   3
   3.  Per-Peer Reporting  . . . . . . . . . . . . . . . . . . . . .   3
   4.  Route Change Statistics based on Routing Policy  . . . . . .   3
     4.1.  Statistics Format . . . . . . . . . . . . . . . . . . . .   3
     4.2.  Statistics Definition . . . . . . . . . . . . . . . . . .   5
     4.3.  Worked Example  . . . . . . . . . . . . . . . . . . . . .   5
   5.  Relationship to Other Work and Call for Collaboration  . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1. Normative References . . . . . . . . . . . . . . . . . .   8
     10.2. Informative References . . . . . . . . . . . . . . . . .   9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   [RFC7854] and [RFC8671] defines different BMP statistics, and
   [RFC9972] extends these BMP statistics to provide more insights
   into the BGP RIBs.

   Routing Policy are widely used in BGP to modify route attributes.
   Monitoring which route attributes are modified and how often can
   provide valuable insights for network operators.

   This document defines few BMP statistics to report such route
   modifications in a generic and address-family-independent manner.
   The format of the BMP statistics message remains same as defined in
   [RFC7854].  Besides address family and gauge in the Stat Data
   (value) [RFC7854], these statistics also provide attribute types of
   route changes.  This route attribute could be the BGP path
   attributes [RFC4271] or additional route attributes for QoS and
   forwarding-related parameters.

1.1.  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 [RFC2119] [RFC8174] when, and only when, they appear in
   all capitals, as shown here.  The BCP14 is used to stress
   importance for operators but are not required as formal
   implementation requirement.

Dikshit, et al.         Expires 25 January 2027                [Page 2]
Internet-Draft         BMP Route Change Stats                July 2026

2.  Motivation and Use Cases

   The ability to track route modifications via Routing Policy
   enables operators to understand policy impact, detect
   misconfigurations, and analyze routing behavior.  The attribute
   type and gauge allow external collectors to derive distribution
   insights.

3.  Per-Peer Reporting

   The BMP peer statistics report message is reported per BGP peer.
   Therefore, each route attribute modification count is associated
   with a specific peer, enabling peer-level policy analysis.

   For locally originated routes applying routing policy, the peer is
   regarded as the local router itself, per Section 8.2 of [RFC7854].

4.  Route Change Statistics based on Routing Policy

4.1.  Statistics Format

   These statistics defined in this document indicate which route
   attribute were modified by routing policy using a 16-bit attribute
   type value followed by a 64-bit Gauge.  and These statistics are
   applicable to all BGP address families, represented by Address
   Family Identifier (AFI) and Subsequent Address Family Identifier
   (SAFI) [RFC4760].  Therefore, the value (Stat Data) of these
   statistics is structured as: 2-byte AFI, 1-byte SAFI, 16-bit
   Attribute Type, followed by a 64-bit Gauge, as shown in the figure
   below.

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |          2-byte AFI           |  1-byte SAFI  |  1-byte NUM   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | 16-bit Attribute Type (first)  |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     64-bit Gauge (first)                     |
      |                                                              ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~ 16-bit Attribute Type (last)                                  ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      ~                     64-bit Gauge (last)                       ~
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   *  AFI: The AFI value is defined in IANA Address Family Numbers.

   *  SAFI: The SAFI value is defined in IANA SAFI Values.

   *  NUM: Indicates that the number of attribute types included in
      the same message.

Dikshit, et al.         Expires 25 January 2027                [Page 3]
Internet-Draft         BMP Route Change Stats                July 2026

   *  Attribute Type: Indicates which route attribute was modified by
      applying routing policy.  The attribute type supports up to
      2^16 types.  In addition to the types defined in this document,
      new attribute types of route change may be defined in the
      future.  The attribute type defined in this document is as
      follows:

      -  Attribute Type = 0x0001: Local Preference.

      -  Attribute Type = 0x0002: AS Path.

      -  Attribute Type = 0x0003: MED.

      -  Attribute Type = 0x0004: Community.

      -  Attribute Type = 0x0005: Extended Community.

      -  Attribute Type = 0x0006: Large Community.

      -  Attribute Type = 0x0007: Origin.

      -  Attribute Type = 0x0008: Next Hop.

      -  Attribute Type = 0x0009: ESI.

      -  Attribute Type = 0x000A: AIGP.

      -  Attribute Type = 0x000B: Prefix SID.

      -  Attribute Type = 0x000C: DSCP.

      -  Attribute Type = 0x000D: VPN Peer ID.

      -  Attribute Type = 0x000E: Preferred Value.

      -  Attribute Type = 0x000F: IP Precedence.

      -  Attribute Type = 0x0010: QoS Local ID.

      -  Attribute Type = 0x0011: Traffic Index.

      -  Attribute Type = 0x0012: MPLS EXP.

      -  Attribute Type = 0x0013-0xFFFF: Reserved, Vendor-specific
         route attribute range.

   These statistics only apply to the AFI/SAFIs that a BGP speaker
   supports and negotiates with its peer.  These statistics for the
   Attribute Type that hasn't been modified by routing policy, MUST
   NOT be reported via the BMP Statistics Report Message.  For these
   statistics defined in this document, the routes that are rejected
   by inbound or outbound policy are not considered.

Dikshit, et al.         Expires 25 January 2027                [Page 4]
Internet-Draft         BMP Route Change Stats                July 2026

4.2.  Statistics Definition

   *  Stat Type = TBD_01: (64-bit Gauge) Number of routes with
      specific change attribute in per-AFI/SAFI post-policy
      Adj-RIB-In due to the application of inbound policy.

   *  Stat Type = TBD_02: (64-bit Gauge) Number of routes with
      specific change attribute in per-AFI/SAFI post-policy
      Adj-RIB-Out due to the application of outbound policy.

4.3.  Worked Example

   This non-normative example illustrates a Statistics Report message
   for a peer negotiated for IPv4 unicast (AFI=1, SAFI=1), where the
   outbound policy modified two attributes across the current
   Adj-RIB-Out:

   AFI  = 1 (IPv4)
   SAFI = 1 (unicast)
   NUM  = 2
   Stat Type = TBD_02 (rib-out-post-policy-attr-change-stats)
     Attribute Type = 0x0001 (Local Preference), Gauge = 128
     Attribute Type = 0x0004 (Community),        Gauge = 47

   This indicates that, at the time of reporting, 128 routes in the
   post-policy Adj-RIB-Out for this peer/AFI/SAFI had their Local
   Preference modified by outbound policy, and 47 had a Community
   modified, since the counters were last reset.  See Section 5 for
   how this per-peer, post-commit accounting relates to the
   pre-commit, per-event deltas proposed in
   [I-D.wang-grow-bmp-policy-preview].

5.  Relationship to Other Work and Call for Collaboration

   Several documents currently active in GROW address policy-driven
   route changes or telemetry from complementary angles.  This section
   maps this document explicitly against that work and records
   specific collaboration proposals; it does not change the semantics
   or wire format of any statistic defined in Section 4.

   *  [I-D.wang-grow-bmp-policy-preview] defines a new Route Pre-view
      Monitoring (RPM) BMP message that streams per-event Add/
      Withdraw/Modify deltas produced by a candidate (not yet
      committed) routing policy evaluated in a control-plane sandbox.
      This document instead reports per-peer, per-AFI/SAFI aggregate
      gauges of attribute changes actually applied by committed
      policy.  The two are complementary temporal views of the same
      underlying event -- "routing policy changed this route" -- one
      pre-commit and per-event, the other post-commit and aggregate.
      We propose to the authors (L. Wang, N. Geng, L. Li, S. Zhuang)
      that the RPM message's "Modify" Pre-view Flag (Section 3 of that
      document) reuse this document's Attribute Type registry
      (Section 4.1) to indicate which specific attribute the
      previewed policy would change, rather than leaving "Modify"

Dikshit, et al.         Expires 25 January 2027                [Page 5]
Internet-Draft         BMP Route Change Stats                July 2026

      unqualified.  This would let a single Attribute Type registry
      serve both the pre-commit preview and post-commit accounting
      use cases, and we would welcome co-authoring that specific
      cross-reference.

   *  [I-D.wang-grow-bmp-bgp-rib-stats-ext] introduces a 4-bit Flags
      field (Triggered/Differential bits) into the Stat Type TLV
      header.  The Differential bit, in particular, is directly
      applicable to the gauges defined in Section 4.2 of this
      document: an implementation could report the rate of change of
      an attribute-modification counter instead of (or in addition
      to) its cumulative value.  As also noted in
      Section 3 of [I-D.saum-grow-bmp-afi-safi-evpn], we propose that
      the Flags octet be standardized once, in a shared, reusable
      location, rather than redefined per statistics document, and we
      invite the authors of that document to coordinate on this
      point.

   *  [I-D.ietf-grow-bmp-stats-informational-tlv], already adopted by
      the GROW working group and co-authored by two of this
      document's authors (M. Srivastava, C. Lin) together with S.
      Kolenchery, defines a Statistics Information TLV carrying
      minimum, maximum, average, and median values alongside a gauge.
      The attribute-change gauges defined in Section 4.2 of this
      document are directly applicable inputs to that TLV, e.g., to
      smooth bursty policy-driven churn following a routing policy
      change roll-out.

   *  [I-D.geng-grow-bmp-rel-enhancement] and its base document
      [I-D.ietf-grow-bmp-rel] define per-event Route Event Logging
      (REL) code points describing specific processing failures (for
      example, BGP FlowSpec or SR Policy action failures).  REL
      answers "what specific event just happened and why", while this
      document answers "how many routes, in aggregate, have had a
      given attribute changed by policy for this peer".  The two
      mechanisms are not overlapping but are frequently relevant to
      the same troubleshooting session (a spike in this document's
      counters together with a burst of related REL events).  We
      suggest a future revision of either document could note this
      relationship explicitly so operators know which mechanism to
      consult first.

   Authors of the documents referenced above are encouraged to bring
   any of these coordination points to the GROW mailing list or to a
   future GROW session so that the Attribute Type registry and Flags
   conventions can be aligned before multiple, mutually incompatible
   variants reach working group last call.

Dikshit, et al.         Expires 25 January 2027                [Page 6]
Internet-Draft         BMP Route Change Stats                July 2026

6.  Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the BMP security model.  All security and authentication
   mechanisms required by Section 11 of [RFC7854], and Section 8 of
   [RFC8671] are also applicable to the gauges defined in this
   document.

   In addition, an observer of the aggregated per-peer,
   per-attribute-type counters defined in Section 4.2 can infer, over
   time, which route attributes a network operator actively adjusts
   via policy and how often, which is a coarser-grained but analogous
   disclosure concern to the one raised for the pre-commit policy
   deltas in the Security Considerations of
   [I-D.wang-grow-bmp-policy-preview].  As with that document, BMP
   sessions carrying these statistics SHOULD be protected using
   TCP-AO [RFC5925] or a TLS profile for BMP, consistent with
   Section 11 of [RFC7854].

7.  IANA Considerations

   IANA has assigned the following new parameters in the BMP
   Statistics Types registry, part of the BMP parameters registry
   group.

   This document requests IANA to update these entries as follows.
   Also, the document requests IANA to update the reference cited for
   the entries.

   *  Type = TBD_01: Number of routes with specific change attribute
      in per-AFI/SAFI post-policy Adj-RIB-In due to the application
      of inbound policy.

   *  Type = TBD_02: Number of routes with specific change attribute
      in per-AFI/SAFI post-policy Adj-RIB-Out due to the application
      of outbound policy.

8.  Contributors

   The following people made significant contributions to this
   document:

   To be added.

9.  Acknowledgements

   The authors would like to acknowledge the GROW working group and
   the authors of the related documents cited in Section 5 for their
   ongoing work in this space; specific review credit will be added
   as discussion on the coordination points in Section 5 progresses.

Dikshit, et al.         Expires 25 January 2027                [Page 7]
Internet-Draft         BMP Route Change Stats                July 2026

10.  References

10.1.  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>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.

   [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>.

   [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>.

   [RFC8671]  Evens, T., Bayraktar, S., Lucente, P., Mi, P., and S.
              Zhuang, "Support for Adj-RIB-Out in the BGP Monitoring
              Protocol (BMP)", RFC 8671, DOI 10.17487/RFC8671,
              November 2019, <https://www.rfc-editor.org/info/rfc8671>.

   [RFC9972]  Srivastava, M., Ed., Liu, Y., Lin, C., Ed., and J. Li,
              "Advanced BGP Monitoring Protocol (BMP) Statistics
              Types", RFC 9972, DOI 10.17487/RFC9972, May 2026,
              <https://www.rfc-editor.org/info/rfc9972>.

   [RFC5925]  Touch, J., Mankin, A., and R. Bonica, "The TCP
              Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
              June 2010, <https://www.rfc-editor.org/info/rfc5925>.

10.2.  Informative References

   [I-D.wang-grow-bmp-policy-preview]
              Wang, L., Geng, N., Li, L., and S. Zhuang, "BGP Route
              Policy Pre-view and Intent Verification Using BGP
              Monitoring Protocol", Work in Progress, Internet-Draft,
              draft-wang-grow-bmp-policy-preview-00, 6 July 2026.

   [I-D.wang-grow-bmp-bgp-rib-stats-ext]
              Wang, L., Geng, N., Li, L., and S. Zhuang, "BGP RIB
              Fine-Grained Filtering Statistics Extensions for BGP
              Monitoring Protocol (BMP)", Work in Progress, Internet-
              Draft, draft-wang-grow-bmp-bgp-rib-stats-ext-01,
              5 July 2026.

Dikshit, et al.         Expires 25 January 2027                [Page 8]
Internet-Draft         BMP Route Change Stats                July 2026

   [I-D.saum-grow-bmp-afi-safi-evpn]
              Dikshit, S., Srivastava, M., and C. Lin, "EVPN-Specific
              BMP RIB Statistics Extensions", Work in Progress,
              Internet-Draft, draft-saum-grow-bmp-afi-safi-evpn-06,
              25 July 2026.

   [I-D.ietf-grow-bmp-stats-informational-tlv]
              Srivastava, M., Kolenchery, S., and C. Lin, "BMP
              Statistics Information TLV", Work in Progress, Internet-
              Draft, draft-ietf-grow-bmp-stats-informational-tlv-00,
              12 May 2026.

   [I-D.geng-grow-bmp-rel-enhancement]
              Geng, N., Gao, Y., Zhuang, S., and H. Wang, "Log More
              Routing Events in the BGP Monitoring Protocol (BMP)",
              Work in Progress, Internet-Draft, draft-geng-grow-bmp-
              rel-enhancement-03, 20 July 2026.

   [I-D.ietf-grow-bmp-rel]
              Lucente, P. and C. Cardona, "Logging of routing events
              in BGP Monitoring Protocol (BMP)", Work in Progress,
              Internet-Draft, draft-ietf-grow-bmp-rel-05, 2 March
              2026.

Authors' Addresses

   Saumya Dikshit
   Aruba Networks, HPE
   Email: saumya.dikshit@hpe.com

   Mukul Srivastava
   Hewlett Packard Enterprise
   Email: mukul.srivastava@hpe.com

   Changwang Lin
   New H3C Technologies
   Email: linchangwang.04414@h3c.com

Dikshit, et al.         Expires 25 January 2027                [Page 9]