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, . [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, . [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, January 2007, . [RFC7854] Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP Monitoring Protocol (BMP)", RFC 7854, DOI 10.17487/RFC7854, June 2016, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [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, . [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, . [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP Authentication Option", RFC 5925, DOI 10.17487/RFC5925, June 2010, . 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]