Network Working Group L. Wang Internet-Draft N. Geng Intended status: Standards Track L. Li Expires: 7 January 2027 S. Zhuang Huawei Technologies 6 July 2026 BGP Route Policy Pre-view and Intent Verification Using BGP Monitoring Protocol draft-wang-grow-bmp-policy-preview-00 Abstract Deploying BGP route policies in live production networks carries significant operational risks, often resulting in unintended route leaks, suboptimal routing paths, or blackholes. This document proposes an extension to the BGP Monitoring Protocol (BMP) that enables a BGP speaker to pre-view and dry-run a candidate route policy within a localized control-plane sandbox. The resulting post- policy route changes (deltas) are streamed asynchronously to a centralized controller via a new BMP message type. This architecture allows the controller to verify policy alignment with network intents, subsequently triggering either an explicit commit or a rollback before any forwarding plane changes take effect. 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. 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/. Wang, et al. Expires 7 January 2027 [Page 1] Internet-Draft BGP RP PV & IV July 2026 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 7 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology and Architectural Overview . . . . . . . . . . . 3 3. Extension to BMP: Route Pre-view Monitoring (RPM) Message . . 3 4. Operational Procedures . . . . . . . . . . . . . . . . . . . 4 4.1. Sandbox Initialization and Delta Computation . . . . . . 4 4.2. The Intent Validation Loop . . . . . . . . . . . . . . . 5 4.3. Transaction Resolution: Commit or Rollback . . . . . . . 5 5. Performance and Scalability Optimization . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 6 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 10.1. Normative References . . . . . . . . . . . . . . . . . . 6 10.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction BGP route policies (e.g., prefix-lists, AS-path filters, community manipulation) are the primary tool for inter-domain traffic engineering. However, modern policy structures are complex and highly error-prone. When a network operator or an automated orchestrator deploys a modified policy to a router, the resulting BGP updates instantly propagate throughout the network. If the policy Wang, et al. Expires 7 January 2027 [Page 2] Internet-Draft BGP RP PV & IV July 2026 contains a logical flaw, widespread traffic disruption occurs before monitoring systems can react. Existing network validation models rely on offline simulation tools. While useful, these simulations cannot perfectly replicate the internal, real-time state machine and multi-vendor nuances of a live router's RIB processing engine. This document defines a protocol-driven mechanism for "on-box" policy pre-viewing. By leveraging a control-plane sandbox, a router executes candidate policies against its live Adj-RIB-In without modifying its active Local-RIB or Forwarding Information Base (FIB). The simulated differences (Deltas) are asynchronously reported via an extended BGP Monitoring Protocol (BMP) [RFC7854] session, providing a reliable, zero-risk framework for closed-loop intent verification. 2. Terminology and Architectural Overview o Candidate Policy: A route policy configuration that is staged but not yet committed or activated in the dataplane. o Control-Plane Sandbox: An isolated software environment within the BGP routing process used exclusively for dry-running candidate policies. o Shadow Local-RIB: A temporary routing information base generated inside the sandbox representing the simulated state of chosen routes. o Policy Transaction ID: A unique identifier assigned by the controller to trace the lifecycle of a specific policy modification event. 3. Extension to BMP: Route Pre-view Monitoring (RPM) Message This document introduces a new BMP message type, termed the Route Pre-view Monitoring (RPM) Message (Suggested Type Value: TBD1). The RPM message extends the standard BMP Route Monitoring (RM) structure by appending a mandatory Policy Transaction Header to encapsulate pre-view context. Wang, et al. Expires 7 January 2027 [Page 3] Internet-Draft BGP RP PV & IV July 2026 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BMP Common Header | | (6 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Per-Peer Header | | (42 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Policy Transaction ID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Pre-view Flag | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BGP UPDATE PDU (Variable Length) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ * Policy Transaction ID: A 32-bit unsigned integer linking the pre- viewed routes back to the configuration transaction initialized by the controller. * Pre-view Flag: A 1-octet bitmask defined as follows: * - 0x01 (Add): The route inside the BGP UPDATE would be newly selected and installed due to the candidate policy. - 0x02 (Withdraw/Deny): The route would be denied or filtered out by the candidate policy, causing a withdrawal from the active RIB. - 0x03 (Modify): The route is still accepted, but its path attributes (e.g., Local-Pref, Communities) are mutated. 4. Operational Procedures 4.1. Sandbox Initialization and Delta Computation When a candidate policy configuration block is staged on the router with a designated Transaction ID, the router MUST NOT evaluate this policy against the active operational Local-RIB. Instead, the router spawns a temporary Sandbox context: 1. The router feeds the existing Adj-RIB-In routes of the targeted peer(s) through the candidate policy engine. Wang, et al. Expires 7 January 2027 [Page 4] Internet-Draft BGP RP PV & IV July 2026 2. The resulting route outputs are gathered into a temporary Shadow Local-RIB. 3. The router performs a mathematical matrix comparison: `Delta = Shadow Local-RIB - Operational Local-RIB`. 4. For each non-zero Delta entry, the router generates an RPM message containing the simulated route state and streams it to the BMP receiver. 4.2. The Intent Validation Loop The centralized SDN controller listens to the RPM stream. By aggregating these messages across multiple monitored nodes, the controller can verify high-level intents (e.g., ensuring traffic does not transit a restricted Autonomous System). 4.3. Transaction Resolution: Commit or Rollback Once verification concludes, the controller completes the transaction using the device's configuration channel (e.g., NETCONF/YANG): * Commit Execution: If the Delta aligns with operator intent, the controller executes a configuration ``. The router merges the Shadow Local-RIB entries directly into the operational Local- RIB and updates the hardware FIB linecards. * Rollback/Discard Execution: If the Delta violates intent, the controller issues a `` or abort command. The router purges the Sandbox instance and drops the Shadow Local-RIB from memory, leaving active data-plane traffic entirely undisturbed. 5. Performance and Scalability Optimization Executing comprehensive shadow calculations across multi-million route tables can stress device CPU and memory. Implementations MUST follow these scoping rules: * Incremental Evaluation: The router SHOULD limit policy execution only to routes belonging to neighbors directly referenced by the policy modification. Wang, et al. Expires 7 January 2027 [Page 5] Internet-Draft BGP RP PV & IV July 2026 * Suppression of Unchanged Flows: If a route passes through the candidate policy with its primary path selection status and all attributes completely unchanged, the router MUST NOT generate an RPM message for that route. 6. IANA Considerations This document requests IANA to allocate a new message type value from the "BGP Monitoring Protocol (BMP) Message Types" sub-registry: o Type: TBD1 o Description: Route Pre-view Monitoring (RPM) Message o Reference: [This-Document] 7. Security Considerations RPM messages expose the hypothetical routing shifts of an enterprise fabric prior to deployment. If intercepted, an attacker could deduce intended traffic engineering patterns. The BMP sessions carrying RPM messages MUST be encrypted using TCP-AO [RFC5925] or TLS profiles customized for BMP. 8. Contributors The following people made significant contributions to this document: To be added. 9. Acknowledgements The authors would like to acknowledge the review and inputs from xxx. 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, . Wang, et al. Expires 7 January 2027 [Page 6] Internet-Draft BGP RP PV & IV July 2026 [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, January 2007, . [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP Authentication Option", RFC 5925, DOI 10.17487/RFC5925, June 2010, . [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, . 10.2. Informative References Authors' Addresses Lili Wang Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: lily.wong@huawei.com Nan Geng Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: gengnan@huawei.com Lei Li Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: kenny.lilei@huawei.com Wang, et al. Expires 7 January 2027 [Page 7] Internet-Draft BGP RP PV & IV July 2026 Shunwan Zhuang Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: zhuangshunwan@huawei.com Wang, et al. Expires 7 January 2027 [Page 8]