Inter-Domain Routing D. Abraitis Internet-Draft NetDef Intended status: Standards Track 5 December 2024 Expires: 8 June 2025 Maximum Prefix Outbound Route Filter for BGP draft-abraitis-idr-maximum-prefix-orf-00 Abstract This document introduces a Maximum Prefix ORF (Outbound Route Filtering) type for BGP. It aims to provide a mechanism whereby the sender of route information is informed of the maximum number of prefixes that the receiver is willing to accept. This facilitates improved resource management by limiting the number of routes exchanged, avoiding unnecessary or excessive route propagation, and reducing memory and CPU load. 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 8 June 2025. Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. Abraitis Expires 8 June 2025 [Page 1] Internet-Draft Maximum Prefix Outbound Route Filter for December 2024 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. Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 4. Specification of Requirements . . . . . . . . . . . . . . . . 3 5. Maximum Prefix ORF-Type . . . . . . . . . . . . . . . . . . . 3 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 7. Security Considerations . . . . . . . . . . . . . . . . . . . 4 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 4 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Normative References . . . . . . . . . . . . . . . . . . . . . 4 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction The Outbound Route Filtering (ORF) capability, as defined in [RFC5291], provides a mechanism for a BGP speaker to send to its BGP peer a set of Outbound Route Filters that can be used by its peer to filter outbound routing updates to the speaker. This document defines a new ORF type, called "Maximum Prefix Outbound Route Filter", which enables a BGP receiver to specify the maximum number of prefixes that a sender should transmit. Rather than specifying particular prefixes, the Maximum Prefix ORF allows the receiver to define a threshold for the number of prefixes it is willing to accept, regardless of specific prefix ranges. The Maximum Prefix ORF provides an efficient mechanism for managing resource consumption, particularly in large BGP environments, by enabling a BGP speaker to limit the number of routes it propagates based on the preferences of its peer. Abraitis Expires 8 June 2025 [Page 2] Internet-Draft Maximum Prefix Outbound Route Filter for December 2024 2. Efficiency The Maximum Prefix ORF provides significant operational efficiency by reducing unnecessary BGP UPDATE messages between peers. Without this ORF, all available routes are sent to the receiver, which must then filter and limit the number of prefixes it installs in its BGP table. Although the receiver filters routes upon receipt, it still processes each incoming UPDATE, resulting in increased CPU and memory load, especially in large networks. 3. Operation The Maximum Prefix ORF is designed to work in conjunction with existing maximum prefix filtering mechanisms, such as configuration commands like "neighbor X maximum-prefix N". This configuration allows operators to set a maximum prefix limit for a BGP neighbor. With the addition of the Maximum Prefix ORF, the receiver can proactively communicate this limit to its BGP peer, informing the sender to enforce the same maximum prefix constraint. This ORF type is sent from the receiver to the sender and allows the sender to filter updates before they are sent, aligning with the receiver's specified limit. Upon receiving the Maximum Prefix ORF, the sender MUST ensure that the total number of prefixes in outbound updates to this receiver does not exceed the specified limit. Any prefixes beyond this limit are filtered by the sender, reducing the load on the receiver's BGP processing and eliminating unnecessary UPDATE messages. 4. Specification of Requirements 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. 5. Maximum Prefix ORF-Type The value of the ORF-Type for the Maximum Prefix ORF-Type is TBD. A Maximum Prefix ORF entry is encoded as defined in the table. Abraitis Expires 8 June 2025 [Page 3] Internet-Draft Maximum Prefix Outbound Route Filter for December 2024 +------------------------------------------------+ | Address Family Identifier (2 octets) | +------------------------------------------------+ | Subsequent Address Family Identifier (1 octet) | +------------------------------------------------+ | Prefix Limit (4 octets) | +------------------------------------------------+ Figure 1 The meaning and use of the fields are as follows: Address Family Identifier (AFI): This field is the same as the one used in [RFC4760]. Subsequent Address Family Identifier (SAFI): This field is the same as the one used in [RFC4760]. Prefix Limit: This field indicates the maximum prefix limit the receiver wants to receive from its peer. If the received Prefix Limit is zero (0), the tuple SHOULD be ignored. 6. IANA Considerations +=======+====================+ | Value | Description | +=======+====================+ | TBD | Maximum Prefix ORF | +-------+--------------------+ Table 1: BGP Outbound Route Filtering (ORF) Types 7. Security Considerations This extension to BGP does not change the underlying security issues in [RFC4271]. Acknowledgements TBD References Normative References Abraitis Expires 8 June 2025 [Page 4] Internet-Draft Maximum Prefix Outbound Route Filter for December 2024 [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, . [RFC5291] Chen, E. and Y. Rekhter, "Outbound Route Filtering Capability for BGP-4", RFC 5291, DOI 10.17487/RFC5291, August 2008, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Author's Address Donatas Abraitis NetDef Email: donatas.abraitis@gmail.com Abraitis Expires 8 June 2025 [Page 5]